Friday, December 10, 2010
Waste electronics in developing countries to grow dramatically
Electronics Recycling: "Harris pointed to a newly released study in the March 22, 2010, issue of the journal, Environmental Science and Technology. In the report, author Eric Williams of Arizona State University writes, 'Trade bans will become increasingly irrelevant in solving the problem' and argues that a complete ban on export of used and end-of-life electronics to developing counties fails to solve the problem because the developing world will generate more used and end-of-life electronics than developed countries as early as 2017. Additionally, by 2025, the developing world will generate twice the amount of electronic scrap as what will come from developed nations."
Thursday, December 9, 2010
PERM Update meeting Jan 2011
PERM (Coral Gables, FL: January 11-13)
Jim McLeish will be providing an update on the status of Mil-HDBK-217 at the PERM meeting. For more information or to arrange a meeting, please contact Jim McLeish.
Jim McLeish will be providing an update on the status of Mil-HDBK-217 at the PERM meeting. For more information or to arrange a meeting, please contact Jim McLeish.
Friday, December 3, 2010
Electronic Material Demand Seems Hitting Bottom
Japan Bulletin: "Market demand for electronic materials seems hitting bottom. The users had increased their material inventories until mid 2010 when sales of home appliances and cars were strong. The users' demand weakened after mid 2010 mainly in Japanese domestic market. Meanwhile, the demand maintains stable except for China. Some of electronic material makers, such as sputtering target material makers, are likely to return to full operations in early 2011.
Inventory adjustment of electronic materials continues for latest several months. For instance, electronic material sales were steady for liquid crystal panel TVs. However, panel inventory became excess in the market and ITO (indium-tin-oxide) makers have downed their productions by about 20%. ITO is main material for transparent electrode of liquid crystal panel. Japanese ITO makers say the demand is especially declining in Taiwan where panel makers are integrated."
Inventory adjustment of electronic materials continues for latest several months. For instance, electronic material sales were steady for liquid crystal panel TVs. However, panel inventory became excess in the market and ITO (indium-tin-oxide) makers have downed their productions by about 20%. ITO is main material for transparent electrode of liquid crystal panel. Japanese ITO makers say the demand is especially declining in Taiwan where panel makers are integrated."
Morphology of the Tin Whiskers on the Surface of a Sn-3Ag-0.5Cu-0.5Nd Alloy
Scopus: "Rapid growth of tin whiskers has been observed on the surface of rosette-shaped NdSn3 intermetallic phase in a Sn-3Ag-0.5Cu-0.5Nd alloy after air storage. It is shown that various cross sections of NdSn3 rosettes in the solder matrix reveal different morphologies of tin whiskers, which can be classified as four types: long fibers, short fibers, tiny sprouts, and hillocks."
The fibrous whiskers and tiny sprouts are found on the surfaces of specimens exposed to air at room temperature and 423 K (150 °C), while hillocks appear only after storage at 423 K (150 °C). In addition, it is observed that, in most cases, each oxidized NdSn3 intermetallic phase contains only a single whisker at its center. Through metallographic observations and chemical analyses on the cross sections of the oxidized NdSn3 intermetallics, a "successive compressive stress model" has been proposed to interpret the tin whisker growth on the surface of a rare earth (RE)-containing solder
Analysis of tin whisker growth on lead-free alloys with Ni presence under thermal shock stress
Scopus: "This paper presents the results of whiskers formation after thermal shocks on various tin-rich materials used in electronics: Sn100, Sn99Cu1, Sn97Cu3, Sn99.3Cu0.7Ni, Sn99.3Cu0.7AgNiGe and Sn99Ag0.3Cu0.7NiGe. Alloys plated over an Ni/Au sublayer were compared with those plated directly over a Cu layer. Scanning electron microscope (SEM) imaging was applied to determine whisker densities, lengths and types. Different degrees of susceptibility to whisker formation were found for all the investigated alloys subjected to 1500 shocks in a cyclic temperature range of -45 'C to 85 'C. Although the whisker growth rates for the alloys plated over an Ni/Au sublayer were lower than for the alloys plated directly over a Cu layer, all the materials tested were more or less prone to whisker formation."
Monday, November 29, 2010
Tin whiskers growth on solder joints
Factiva: "We evaluated the Sn whisker growth behavior of Sn-Ag-Cu solder fillets on lead frames of quad flat packages (QFPs) upon OSP printed circuit boards that were exposed to 85 A degrees C/85% relative humidity (RH) exposure. Three different concentrations of halogen flux for activated Sn-3.0wt%Ag-0.5wt%Cu were used to solder in air and in an inert N-2 reflow atmosphere,' researchers in Osaka, Japan report.
'The lead frames of the QFPs consisted of Sn plated Cu and Fe-42wt%Ni (alloy 42). Sn whiskers were observed on the surface of the QFP solder fillet joints that were reflowed with halogen containing flux in an air atmosphere. A substantial amount of Sn oxides were formed in those solder fillets while whisker growth and the amount of Sn oxides increased with the halogen content. Sn oxide formation apparently enhanced whisker formation. The combination of air reflow atmosphere and high halogen flux was the worst combination for solder fillet oxidation resulting in Sn whisker formation regardless of the electrode's lead frame composition of Cu or alloy 42,' wrote A. Baated and colleagues, Osaka University.
The researchers concluded: 'In contrast, an inert N-2 reflow atmosphere obviously prevented Sn whisker formation on Sn-Ag-Cu solder fillets under all conditions used in this work"
'The lead frames of the QFPs consisted of Sn plated Cu and Fe-42wt%Ni (alloy 42). Sn whiskers were observed on the surface of the QFP solder fillet joints that were reflowed with halogen containing flux in an air atmosphere. A substantial amount of Sn oxides were formed in those solder fillets while whisker growth and the amount of Sn oxides increased with the halogen content. Sn oxide formation apparently enhanced whisker formation. The combination of air reflow atmosphere and high halogen flux was the worst combination for solder fillet oxidation resulting in Sn whisker formation regardless of the electrode's lead frame composition of Cu or alloy 42,' wrote A. Baated and colleagues, Osaka University.
The researchers concluded: 'In contrast, an inert N-2 reflow atmosphere obviously prevented Sn whisker formation on Sn-Ag-Cu solder fillets under all conditions used in this work"
Journal of Materials Science - Materials in Electronics (Effects of reflow atmosphere and flux on Sn whisker growth of Sn-Ag-Cu solders. Journal of Materials Science - Materials in Electronics, 2010;21(10):1066-1075).
For additional information, contact A. Baated, Osaka University, Institute Science & Ind Research, Mihogaoka 8-1, Osaka 5670047, Japan.
Stress-strain effects on PCB vibration reliability
Factiva: "Conventional cycle counting techniques were used to quantify the random excitation histories in terms of range distribution functions. Using the same time-domain vibration fatigue analysis used earlier for narrow-band excitation, the durability trend for the corresponding SAC305 and Sn37Pb solder interconnects under broad-band excitation was found to be similar to that found earlier under harmonic vibration excitation. Comparison between the durability prediction and test results provides a good understanding of the effect of stress-strain behavior on the fatigue constants of these solder materials"
Y. Zhou, University of Maryland, Center Advanced Life Cycle Engineering, Dept. of Mech Engineering, College Park, MD 20742, USA.
Microelectronic package having solder-filled through-vias
US20070278635A1: "An apparatus, a method, and a system associated with microelectronic packaging are disclosed herein. In various embodiments, a microelectronic package may include a die having one or more through-vias, each filled with a solder material; a substrate; and one or more solder bumps disposed between and electrically connecting the substrate and a backside of the die."
Apparatus and method for depositing and reflowing solder paste on a microelectronic workpiece
US7637412: "Stenciling machines and methods for forming solder balls on microelectronic workpieces are disclosed herein. In one embodiment, a method for depositing and reflowing solder paste on a microelectronic workpiece having a plurality of dies includes positioning a stencil having a plurality of apertures at least proximate to the workpiece. The method further includes placing discrete masses of solder paste into the apertures and reflowing the discrete masses of solder paste while the stencil is positioned at least proximate to the workpiece and while the discrete masses are in the apertures."
Solder wire for connectors
SOLDER WIRE CONSTRUCTION (US20090173517A1): "Solder construction carrier device for connecting e.g. connectors to printed circuit boards has solder construction with conductive inner wire and mass of solder formed around inner wire so that inner wire is surrounded"
The death toll of the blood minerals inside your PC
PC Pro: "“The industry is so price-conscious that no-one really wants to increase costs by eliminating a major source for these rare-earth elements,” said IDC’s Palma. “I think the lack of global regulatory enforcement will allow OEMs to say they do not know the source of the material, or rather that they do not believe they are using the subject materials from restricted areas.”
This ignorance-is-bliss approach is already gaining ground among IT suppliers. For example, Cabot – a major producer of tantalum – has made efforts to address the issues, but says it will “not knowingly purchase any material mined in the Congo”. Dell also used the “not knowingly” caveat.
“I think this act will have little real impact beyond causing an additional amount of paperwork and legal costs for the industry, with a negligible impact on costs to consumers,” said Palma."
This ignorance-is-bliss approach is already gaining ground among IT suppliers. For example, Cabot – a major producer of tantalum – has made efforts to address the issues, but says it will “not knowingly purchase any material mined in the Congo”. Dell also used the “not knowingly” caveat.
“I think this act will have little real impact beyond causing an additional amount of paperwork and legal costs for the industry, with a negligible impact on costs to consumers,” said Palma."
Sn grain size and orientation vs solder joint size
Factiva: "Polarized light microscopy and electron backscatter diffraction have been used to quantify the number of beta-Sn grains and to examine the Sn crystallographic orientation in Sn-Ag-Cu/Cu solder joints, respectively. The effect of solder joint size on the Sn grain features was investigated due to the miniaturization of solder joints,' scientists in Harbin, People's Republic of China report.
'The Sn-Ag-Cu solder joints of different sizes were found to contain only several beta-Sn crystal grains and most solder joints were comprised of no more than three Sn grains. The solder joints showed a preferred crystal orientation. The c crystal axis of beta-Sn grains tended to be at a small angle with solder pads. Specific orientation relationships were observed to be prevalent between neighboring beta-Sn grains,' wrote S.H. Yang and colleagues.
The researchers concluded: 'The grain number, crystal orientation and misorientation were independent of solder joint size"
'The Sn-Ag-Cu solder joints of different sizes were found to contain only several beta-Sn crystal grains and most solder joints were comprised of no more than three Sn grains. The solder joints showed a preferred crystal orientation. The c crystal axis of beta-Sn grains tended to be at a small angle with solder pads. Specific orientation relationships were observed to be prevalent between neighboring beta-Sn grains,' wrote S.H. Yang and colleagues.
The researchers concluded: 'The grain number, crystal orientation and misorientation were independent of solder joint size"
S.H. Yang, Harbin Institute Technology, Dept. of Electrical Packaging Technology, 92 W Dazhi St., Harbin 150001, People's Republic of China.
Interconnect Solder Bumps Making Method Developed by Inventors
Factiva: "Six inventors have invented a method for making interconnect solder bumps. The U.S. Patent was issued on Nov. 16 (No. 7,833,897). The co-inventors are Sarah H. Knickerbocker, Sean A. Allen and Phillip W. Palmatier, Hopewell Junction, N.Y.; Jerry A. Gorrell, Lagrangeville, N.Y.; John J. Garant, Poughkeepsie, N.Y.; and Christopher L. Tessler, Poughquag, N.Y.
An abstract of the invention, published by the U.S. Patent and Trademark Office, states: 'A method is provided for making of interconnect solder bumps on a wafer or other electronic device without depositing any significant amount of tin or other solder component from the solder onto the wafer surface which tin can cause shorts or other defects in the wafer."
An abstract of the invention, published by the U.S. Patent and Trademark Office, states: 'A method is provided for making of interconnect solder bumps on a wafer or other electronic device without depositing any significant amount of tin or other solder component from the solder onto the wafer surface which tin can cause shorts or other defects in the wafer."
International Business Machines Corp. (http://www.ibm.com/), Armonk, N.Y. The application was filed on July 17, 2007 (No. 11/778,678
Report on Phase I of IPC Market Research on Electronics Technology Trends: Insights
TECHTR-10WP: "Research conducted by IPC – Association Connecting Electronics Industries - indicates the top ten technology trends to watch in electronics manufacturing include miniaturization, high-performance, high-density interconnect (HDI), embedded technology, flexible circuits, lead free, halogen free, light-emitting diodes (LEDs), optoelectronics and printed electronics. Ideas about the trends have been compiled in a free white paper from interviews with industry experts and executives at printed circuit board (PCB) manufacturers, electronics manufacturing services (EMS) companies, original equipment manufacturers (OEMs) as well as suppliers of materials and equipment to those industries"
Understanding Tin Whiskers
EMS007: "In high-reliability applications, product designers and manufacturers need to take a number of these steps. That puts some limitations of the processes.
'When you can't define the risks, you need to be more conservative,' Hillman said.
While the issue can be hot--Delphi's Sam Platt said that tin whiskers 'evoke terror in electronics circles'--the occurrence of tin whiskers is fairly rare.
That makes it difficult to research the problem. 'Our understanding of tin whiskers is limited by our inability to consistently, repeatedly create them,' Hillman said."
'When you can't define the risks, you need to be more conservative,' Hillman said.
While the issue can be hot--Delphi's Sam Platt said that tin whiskers 'evoke terror in electronics circles'--the occurrence of tin whiskers is fairly rare.
That makes it difficult to research the problem. 'Our understanding of tin whiskers is limited by our inability to consistently, repeatedly create them,' Hillman said."
Managing Dross in Soldering Processes
EMS007s: "Wave, selective and related soldering processes involve relatively large volumes of molten solder that are exposed to the atmosphere. Turbulence, oxygen exposure, temperature and other factors affect dross formation in wave soldering processes. Keith Sweatman and Keith Howell, both of Nihon Superior, advise operators on how to reduce dross."
IPC Criticizes Greenpeace Electronics Guide
EMS007 : "'In addition, IPC, on behalf of our members, is extremely concerned about Greenpeace's tactics in penalizing companies for ‘failing to openly support restrictions on ... brominated flame retardants (BFRs)....' In fact, Greenpeace provides specific wording it would like to see companies use in calling for an expansion of the RoHS Directive to include the ban of BFRs.
'Demonizing certain substances without a scientific basis can lead industries to adopt substances that have a greater environmental impact or that cause resources to be inefficiently used. IPC calls on nongovernmental organizations (NGOs) and regulators to adopt scientific principles in the evaluation and banning of any chemicals and substances.'"
'Demonizing certain substances without a scientific basis can lead industries to adopt substances that have a greater environmental impact or that cause resources to be inefficiently used. IPC calls on nongovernmental organizations (NGOs) and regulators to adopt scientific principles in the evaluation and banning of any chemicals and substances.'"
RoHS Recast Vote delayed
Real Time With... SMTAI 2010
The long-awaited RoHS recast has been delayed yet again. Krista Botsford expands on the EU's decision to split RoHS and WEEE directives, as well as open scope and declarations of conformity requirements. These topics and others continue to push the vote out; it is now scheduled for November 22, 2010
Video
European Parliament votes in favour of RoHS recast
Chemical Watch: "The European Parliament has voted in favour of the recently agreed compromise proposal for the recast of the Directive on the restriction of hazardous substances (RoHS) in electrical and electronic equipment (CW 12 November 2010). While the Green Party and consumer health NGOs said they would have preferred stronger legislation, they admitted that the compromise was an improvement on the current Directive. The updated legislation will not..."
Thursday, November 25, 2010
Consultants call for two more RoHS exemptions
German consultancies the Öko-Institut and Fraunhofer IZM have advised the European Commission to grant two exemptions for certain uses of cadmium and lead from bans under the RoHS directive on hazardous substances in electronic equipment.
The recommendation follows consultations run earlier this year. The consultants found that the use of lead in integrated capacitors with PZT-based dielectric ceramics is unavoidable and should have a specific exemption. There is concern among manufacturers that this use will no longer be allowed from 2012.
The consultants also recommended renewing an exemption for cadmium in photoresistors for analog optocouplers applied in professional audio equipment until December 2013. The exemption expired at the end of 2009. Two more years are needed for the development of substitutes, they say.
The commission will now start a comitology procedure for a combined decision on both exemptions. The decision must be backed by the EU executive and member state representatives. A third consultation on three exemptions is now closed. A fourth one covering two new exemption requests may be launched in December.
The recommendation follows consultations run earlier this year. The consultants found that the use of lead in integrated capacitors with PZT-based dielectric ceramics is unavoidable and should have a specific exemption. There is concern among manufacturers that this use will no longer be allowed from 2012.
The consultants also recommended renewing an exemption for cadmium in photoresistors for analog optocouplers applied in professional audio equipment until December 2013. The exemption expired at the end of 2009. Two more years are needed for the development of substitutes, they say.
The commission will now start a comitology procedure for a combined decision on both exemptions. The decision must be backed by the EU executive and member state representatives. A third consultation on three exemptions is now closed. A fourth one covering two new exemption requests may be launched in December.
Friday, November 19, 2010
Assembleon joins sustainable electronics manufacturing working group
Global SMT and Packaging: "Royal Philips Electronics subsidiary Assembleon’s CEO Andre Papoular has accepted the seat representing pick & place in the newly formed Sustainable Electronics Manufacturing (SEM) Working Group. The Working Group is a think tank for leading players in industrial manufacturing, and aims to improve the competitiveness of this industry by reducing its environmental impact"
The Working Group’s inaugural meeting was held at today’s Sustainability Summit (17 November, Milan), amidst sustainability experts and leading suppliers of electronic components, fabrication and assembly equipment and PCBs. It is organized by OnBoard Technology together with Sustainability Magazine, Global Identification, EMSNow, PLUS, PCB Magazine and other media partners.
“We are delighted to serve on the SEM Working Group, and are well placed to contribute,” remarked Papoular. “Assembléon sets the industry benchmark for efficient pick & place machine energy use. Our AX-Series consumes half the electricity of competitors’ machines, which reduces CO2 emissions and can save up to €10.000 in operating costs per pick & place machine per year. Translating energy efficiency into business benefits is very important in this industry. We are very pleased that our work has been noticed and has resulted in the invitation to represent the pick & place discipline in the Working Group.”
Monday, November 15, 2010
German research finds high level of wireless telephones do not comply with RoHS
Chemical Watch: "A research project funded by the German Federal Environment Agency (UBA) has found that a high proportion of new wireless telephones contain substances controlled by the restriction of hazardous substances (RoHS) in electronic and electrical equipment Directive, along with other chemicals of concern. Speaking at the electronics industry Going Green Care Innovation meeting in Vienna this week Michael Riess, of VDE – the testing house that..."
Wednesday, November 10, 2010
iNEMI Whitepaper Defines HFR-Free and PVC-Free Timeline for computers
This whitepaper clarifies the good work and progress that has been made to date by iNEMI members in converting to HFR-free and PVC-free system components. It also defines the remaining issues to be addressed, the approach being taken to engineer good alternatives and the timeline expected for iNEMI’s OEM members to convert their notebook and desktop products to HFR/PVC-free.
White Paper
White Paper
Tuesday, November 9, 2010
Options for Reducing Dross
CircuitMart: "Options to reduce dross in wave soldering systems are:
Use nitrogen blanket over the waves, depending on cost of nitrogen gas,
Use oil blanket over the wave soldering pot (beware of any oil contamination)
Use the narrowest width of wave required, eg, don't buy a 24' wave for 6' width PCB
Use selective wave soldering machine if there are only few components to be soldered
use the lowest wave height required, cut the thru hole lead length to the shortest possible.
use only good quality solder bar, some cheap solder bars are recycled from solder dross
Use solder recovery systems, that squeeze hot solder dross to separate molten solder from oxide
Turn on the waves only when the PCB is near the waves (towards the end of preheating zones), and not permanently on."
Use nitrogen blanket over the waves, depending on cost of nitrogen gas,
Use oil blanket over the wave soldering pot (beware of any oil contamination)
Use the narrowest width of wave required, eg, don't buy a 24' wave for 6' width PCB
Use selective wave soldering machine if there are only few components to be soldered
use the lowest wave height required, cut the thru hole lead length to the shortest possible.
use only good quality solder bar, some cheap solder bars are recycled from solder dross
Use solder recovery systems, that squeeze hot solder dross to separate molten solder from oxide
Turn on the waves only when the PCB is near the waves (towards the end of preheating zones), and not permanently on."
Thursday, November 4, 2010
Printed Electronics: a "Game Changing" Technology
SEMI: "Printed electronics are here! We are witnessing the appearance of new products in the marketplace: some with printed components; some currently being manufactured using alternative techniques but with strong potential for large volume manufacturing based on additive processes; and others that are fully printed. All these types of devices are now available, demonstrating the capabilities of the technologies.
Multi-disciplinary teams have formed in companies representing different parts of the value chain. These teams are evaluating the products being made in an effort to bring these disruptive technologies into the market place. Vibrant activities are bringing together academic research and companies of all shapes and sizes, developing new form factors for existing products and creating new ones."
Tuesday, November 2, 2010
Lightbulb wars: More than just LED
CNET News: "'There's no source that's going to beat everything. LEDs are great for certain things, but HID [high-intensity discharge] metal halides have some really great advantages,' said Michael Myer, researcher in the energy and efficiency division of the Pacific Northwest National Laboratory, during a panel. 'I really don't think in my lifetime we'll see a stadium lit with LEDs.'
One of the drivers for change in lighting technology is government-led efforts around the world to improve efficiency, the equivalent of fuel efficiency standards for vehicles. In 2012, for instance, a law will go into effect in the U.S. in keeping witb efficiency mandates pointing toward the phase-out of 100-watt incandescent bulbs.
But even prior to legislation in the U.S. and elsewhere, demand for incandescent lighting is half what it was five years ago, said John Strainic, global product general manager for GE Lighting.
In its place are compact fluorescent bulbs and increasingly LEDs , which promise an improvement in efficiency and last far longer than other lighting technologies. GE's 40-watt-equivalent LED bulb for general lighting, for example, is projected to last over 20 years, assuming three hours of daily use."
One of the drivers for change in lighting technology is government-led efforts around the world to improve efficiency, the equivalent of fuel efficiency standards for vehicles. In 2012, for instance, a law will go into effect in the U.S. in keeping witb efficiency mandates pointing toward the phase-out of 100-watt incandescent bulbs.
But even prior to legislation in the U.S. and elsewhere, demand for incandescent lighting is half what it was five years ago, said John Strainic, global product general manager for GE Lighting.
In its place are compact fluorescent bulbs and increasingly LEDs , which promise an improvement in efficiency and last far longer than other lighting technologies. GE's 40-watt-equivalent LED bulb for general lighting, for example, is projected to last over 20 years, assuming three hours of daily use."
Nihon Superior Opens R&D Center in Japan
EMS007 "Nihon Superior Co. Ltd., a supplier of advanced soldering materials to the global market, announces the grand opening of its new Research and Development center. The opening celebration was held on Friday, October 15, 2010 at the new center located in Osaka, Japan.
'Our technical, sales and quality assurance departments have merged, resulting in our new R&D Center. We plan to leverage the capabilities of our new R&D Center to respond to a more diverse range of customer needs. Simultaneously, we will continue to aggressively advance our academic research to contribute to the development of the electronics industry,' said Tetsuro Nishimura, President of Nihon Superior Co. Ltd."
'Our technical, sales and quality assurance departments have merged, resulting in our new R&D Center. We plan to leverage the capabilities of our new R&D Center to respond to a more diverse range of customer needs. Simultaneously, we will continue to aggressively advance our academic research to contribute to the development of the electronics industry,' said Tetsuro Nishimura, President of Nihon Superior Co. Ltd."
Indium Corporation Technology Expert Presenting at IPC Works Asia
EMSNow: "Indium Corporation's Brian Huang, Area Technical Manager for South China, will be presenting at IPC Works Asia 2010, October 26 - 27, 2010, in Shenzhen, China.
Brian's paper, Establishing a Precision Stencil Printing Process for Miniaturized Electronics Assembly, discusses optimization techniques employed to establish precision SMT printing processes. These techniques are in response to the need to assemble the smaller and smaller components used in miniaturized electronics for mobile phones and other portable devices."
Brian's paper, Establishing a Precision Stencil Printing Process for Miniaturized Electronics Assembly, discusses optimization techniques employed to establish precision SMT printing processes. These techniques are in response to the need to assemble the smaller and smaller components used in miniaturized electronics for mobile phones and other portable devices."
New Developments in High Performance Solder Products
New Developments in High Performance Solder Products: "The use of special purpose solder pastes in power die attach is well-established offering low voiding and reliable bonding in volume manufacturing. However these materials are designed around high lead alloys and applied by dispensing. IGBT circuits are made by printing high tin alloys to multiple die sites, placing die and reflowing in a process more similar to conventional PCB or hybrid thick film assembly.
This paper describes how the opportunity was taken to make use of the latest developments in Pb-free SMT flux technology and re- optimize them to the different requirements of IGBT die attach. We rehearse the attributes and requirements of IGBT circuitry and then go on to show how a high performance Pb-Free solder paste has been developed to meet the requirements of large power die attachment (LDA) in IGBT module manufacturing processes.
The paste has excellent print and handling characteristics and routinely returns less than 0.5% voiding under large die over a wide range of vacuum reflow conditions. The flux vehicle chemistry offers ease of cleaning to be compatible with the next stage processes of wire bonding & circuit encapsulation"
High-temperature lead-free solders: Properties and possibilities
SpringerLink JOM Journal of the Minerals, Metals and Materials Society, Volume 61, Number 1: "Katsuaki Suganuma, Seong-Jun Kim and Keun-Soo Kim"
New Developments in High-Temperature, High-Performance Lead-Free Solder Alloys
Printed Circuit Design & Fab Magazine Online:
Author: Anton-Zoran Miric; anton.miric@heraeus.com.
Abstract: This paper reviews the composition, hardening mechanisms and performance of a new SAC metallurgical system. The alloy has small amounts of antimony, bismuth and nickel that harden the alloy and improve creep strength, resulting in significantly improved reliability (vs. SAC and SnPb) of solder joints at standard temperatures of 125'C, especially with ceramic chip components. This alloy enables operating temperatures of up to 165'C. (SMTA International, October 2010)"
Author: Anton-Zoran Miric; anton.miric@heraeus.com.
Abstract: This paper reviews the composition, hardening mechanisms and performance of a new SAC metallurgical system. The alloy has small amounts of antimony, bismuth and nickel that harden the alloy and improve creep strength, resulting in significantly improved reliability (vs. SAC and SnPb) of solder joints at standard temperatures of 125'C, especially with ceramic chip components. This alloy enables operating temperatures of up to 165'C. (SMTA International, October 2010)"
Technology could help firms overcome high tin cost
Steel Guru: "Mitch Holtzer, Cookson's director for assembly materials, said that technological developments have the potential to cut consumption of tin a metal for which it is difficult to find substitutes, without disrupting the solder market. He cited the use of nitrogen in the soldering process, which prevents tin from oxidising and therefore reduces waste, which he said, could be a solution for cutting costs.
He said that at some point nitrogen becomes inexpensive enough to use that it's a net saving for the user to pump nitrogen across the solder. Selective soldering machines, which are much smaller units that consume less solder and generate less scrap, are also coming on the market. We've seen quite a significant reduction for demand for bar solder because of this selective trend."
Even so, the long-term future for the use of tin in electronic solders is fundamentally sound, in part because of the billions of dollars invested in the infrastructure of electronics assembly, he said.
Also a 40 percent jump in silver prices this year could benefit tin. Spot silver was last indicated at $23.59 an ounce.
"If you substitute tin for silver, that does bring down the cost of solders dramatically. We see a very rapid trend (developing) in that area, which could begin next year," said Holtzer, adding that the silver content could be reduced from 3 percent to as little as 0.3 percent.
He said that at some point nitrogen becomes inexpensive enough to use that it's a net saving for the user to pump nitrogen across the solder. Selective soldering machines, which are much smaller units that consume less solder and generate less scrap, are also coming on the market. We've seen quite a significant reduction for demand for bar solder because of this selective trend."
Even so, the long-term future for the use of tin in electronic solders is fundamentally sound, in part because of the billions of dollars invested in the infrastructure of electronics assembly, he said.
Also a 40 percent jump in silver prices this year could benefit tin. Spot silver was last indicated at $23.59 an ounce.
"If you substitute tin for silver, that does bring down the cost of solders dramatically. We see a very rapid trend (developing) in that area, which could begin next year," said Holtzer, adding that the silver content could be reduced from 3 percent to as little as 0.3 percent.
Thursday, October 28, 2010
Friday, October 22, 2010
Not whiskers or hillocks, but tin bumps on RF shielding cans
Scopus: "Pure tin bumps can sometimes be formed on tin-plated steel RF cans during certain conditions of reflow. This is a rare phenomena not associated with tin whiskers. A Design of Experiments (DOE) strategy was used to confirm the oven variables that could be used to turn the formation on or off. Extensive lab work and investigation by the supplier revealed that the root cause of these bumps is organic contamination during the plating process."
S-Bond patent on active low temperature solders
United States Patent: 7806994: "Electronic package formed using low-temperature active solder including indium, bismuth, and/or cadmium
Abstract
An active solder alloy, an electronic device package including the active solder alloy bonding an electronic device to a substrate, and a method of forming high-strength joints by soldering using the solder alloy. The alloy contains up to about 10% by weight of an element or a mixture of elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, or tantalum; between about 0.1 and 5% by weight of an element or a mixture of elements selected from the group of the lanthanides (rare earths); between about 0.01 and 1% by weight of gallium up to about 10% by weight of silver; up to about 2% by weight of magnesium; and a remainder consisting of tin, bismuth, indium, cadmium, or a mixture of two or more of these elements. The alloy enables low-temperature (less than about 180.degree. C.) soldering within relatively narrow melting ranges (less than about 10.degree. C.).
Inventors: Smith; Ronald W. (Blue Bell, PA), Redd; Randall (Phoenixville, PA)
Assignee: S-Bond Technologies, LLC (Lansdale, PA)
Appl. No.: 11/579,413
Filed: May 4, 2005"
Abstract
An active solder alloy, an electronic device package including the active solder alloy bonding an electronic device to a substrate, and a method of forming high-strength joints by soldering using the solder alloy. The alloy contains up to about 10% by weight of an element or a mixture of elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, or tantalum; between about 0.1 and 5% by weight of an element or a mixture of elements selected from the group of the lanthanides (rare earths); between about 0.01 and 1% by weight of gallium up to about 10% by weight of silver; up to about 2% by weight of magnesium; and a remainder consisting of tin, bismuth, indium, cadmium, or a mixture of two or more of these elements. The alloy enables low-temperature (less than about 180.degree. C.) soldering within relatively narrow melting ranges (less than about 10.degree. C.).
Inventors: Smith; Ronald W. (Blue Bell, PA), Redd; Randall (Phoenixville, PA)
Assignee: S-Bond Technologies, LLC (Lansdale, PA)
Appl. No.: 11/579,413
Filed: May 4, 2005"
Creep properties of Sn-0.7Cu composite solder joints reinforced with nano-sized Ag particles
Scopus: "The purpose of this paper is to investigate the creep properties of Sn-0.7Cu composite solder joints reinforced with optimal nano-sized Ag particles in order to improve the creep performance of lead-free solder joints by a composite approach. Design/methodology/approach - The composite approach has been considered as an effective method to improve the creep performance of solder joints. Nano-sized Ag reinforcing particles were incorporated into Sn-0.7Cu solder by mechanically mixing. A systematic creep study was carried out on nano-composite solder joints reinforced with optimal nano-sized Ag particles and compared with Sn-0.7Cu solder joints at different temperatures and stress levels"
A steady-state creep constitutive equation for nano-composite solder joints containing the best volume reinforcement was established in this study. Microstructural features of solder joints were analyzed to help determine their deformation mechanisms during creep. Findings - The creep activation energies and stress exponents of Ag particle-enhanced Sn-0.7Cu lead-free based composite solder joints were higher than those of matrix solder joints under the same stress and temperature. Thus, the creep properties of nano-composite solder joints are better than those of Sn-0.7Cu solder joints. Originality/value - The findings indicated that nano-sized Ag reinforcing particles could effectively improve the creep properties of solder joints. A new steady-state creep constitutive equation of nano-composite solder joints was established. Deformation mechanisms of Sn-0.7Cu solder and nano-composite solder joints during creep were determined
Use of surface halogen on solder particles to improve wettability in halide-free paste
Factiva: "Publication No. WO/2010/116971 was published on Oct. 14.
Title of the invention: 'SOLDER PARTICLES AND METHOD FOR PRODUCING SAME, AND SOLDER PASTE AND METHOD FOR PRODUCING SAME.'
Applicants: ISHIKAWA METAL CO., LTD. (JP), TOHOKU TECHNOARCH CO., LTD. (JP) and DENSHI-JISSO.COM CO., LTD. (JP).
Inventors: Kazuyuki Tohji (JP), Hideyuki Takahashi (JP) and Takeshi Tanaka (JP).
According to the abstract posted by the World Intellectual Property Organization: 'Conventional solder pastes contain an activator containing a halogen for the purpose of increasing the wettability to an object to be soldered. Halogens, however, are highly toxic to the human body and cause the formation of dioxin. Consequently, there has been demand for a solder paste that is free from halogens or has a significantly reduced halogen content. In order to meet the demand, a solder paste is produced by mixing solder particles, on the surfaces of which an extremely small amount of a halogen is present, into a flux composition which does not contain an activator and is composed of an adhesive, a solvent, a thixotropic agent and the like. Although the amount of halogen contained in this solder paste is extremely small, the wettability to an object to be soldered is practically sufficient.'
The patent was filed on April 5, 2010 under Application No. PCT/JP2010/056167."
Title of the invention: 'SOLDER PARTICLES AND METHOD FOR PRODUCING SAME, AND SOLDER PASTE AND METHOD FOR PRODUCING SAME.'
Applicants: ISHIKAWA METAL CO., LTD. (JP), TOHOKU TECHNOARCH CO., LTD. (JP) and DENSHI-JISSO.COM CO., LTD. (JP).
Inventors: Kazuyuki Tohji (JP), Hideyuki Takahashi (JP) and Takeshi Tanaka (JP).
According to the abstract posted by the World Intellectual Property Organization: 'Conventional solder pastes contain an activator containing a halogen for the purpose of increasing the wettability to an object to be soldered. Halogens, however, are highly toxic to the human body and cause the formation of dioxin. Consequently, there has been demand for a solder paste that is free from halogens or has a significantly reduced halogen content. In order to meet the demand, a solder paste is produced by mixing solder particles, on the surfaces of which an extremely small amount of a halogen is present, into a flux composition which does not contain an activator and is composed of an adhesive, a solvent, a thixotropic agent and the like. Although the amount of halogen contained in this solder paste is extremely small, the wettability to an object to be soldered is practically sufficient.'
The patent was filed on April 5, 2010 under Application No. PCT/JP2010/056167."
Oxidation of liquid solders for die attachment
Scopus This study deals with thermal oxidation behaviour in the liquid state of a commonly-used die-attach solder, Pb-Sn, and its potential Pb-free alternatives (Bi-Ag and Zn-Sn) from viewpoints of thermodynamics and kinetics. The characteristics of the oxidation reaction layers were investigated using XPS, XRD and AES. The superior performance in oxidation prevention of the Zn based alloys can be ascribed to their stable oxidative product, ZnO, which exhibits low free energy of formation, as well as slow growth rate."
Indium-aluminium high temperature solder
Factiva: "United States Patent no. 7,816,250, issued on Oct. 19, was assigned to Intel Corp. (Santa Clara, Calif.).
'Composite Solder Tim for Electronic Package' was invented by Tom Fitzgerald (Phoenix), Carl Deppisch (Chandler, Ariz.) and Fay Hua (Fremont, Calif.).
According to the abstract released by the U.S. Patent & Trademark Office: 'A method includes providing a mixture of molten indium and molten aluminum, and agitating the mixture while reducing its temperature until the aluminum changes from liquid phase to solid phase, forming particles distributed within the molten indium. Agitation of the mixture sufficiently to maintain the aluminum substantially suspended in the molten aluminum continues while further reducing the temperature of the mixture until the indium changes from a liquid phase to a solid phase. A metallic composition is formed, including indium and particles of aluminum suspended within the indium, the aluminum particles being substantially free from oxidation.The metallic (solder) composition can be used to form an assembly, including an integrated circuit (IC) device, at least a first thermal component disposed adjacent to the IC device, and a solder TIM interposed between and thermally coupled with each of the IC device and the first thermal component.'
The patent was filed on Sept. 29, 2006, under Application No. 11/540,027."
'Composite Solder Tim for Electronic Package' was invented by Tom Fitzgerald (Phoenix), Carl Deppisch (Chandler, Ariz.) and Fay Hua (Fremont, Calif.).
According to the abstract released by the U.S. Patent & Trademark Office: 'A method includes providing a mixture of molten indium and molten aluminum, and agitating the mixture while reducing its temperature until the aluminum changes from liquid phase to solid phase, forming particles distributed within the molten indium. Agitation of the mixture sufficiently to maintain the aluminum substantially suspended in the molten aluminum continues while further reducing the temperature of the mixture until the indium changes from a liquid phase to a solid phase. A metallic composition is formed, including indium and particles of aluminum suspended within the indium, the aluminum particles being substantially free from oxidation.The metallic (solder) composition can be used to form an assembly, including an integrated circuit (IC) device, at least a first thermal component disposed adjacent to the IC device, and a solder TIM interposed between and thermally coupled with each of the IC device and the first thermal component.'
The patent was filed on Sept. 29, 2006, under Application No. 11/540,027."
Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation
Scopus: "In this research, a two-step process consisting of vacuum pyrolysis and vacuum centrifugal separation was employed to treat waste printed circuit boards (WPCBs). Firstly, WPCBs were pyrolysed under vacuum condition at 600 'C for 30 min in a lab-scale reactor. Then, the obtained pyrolysis residue was heated under vacuum until the solder was melted, and then the molten solder was separated from the pyrolysis residue by the centrifugal force. The results of vacuum pyrolysis showed that the type-A of WPCBs (the base plates of which was made from cellulose paper reinforced phenolic resin) pyrolysed to form an average of 67.97 wt% residue, 27.73 wt% oil, and 4.30 wt% gas; and pyrolysis of the type-B of WPCBs (the base plates of which was made from glass fiber reinforced epoxy resin) led to an average mass balance of 72.20 wt% residue, 21.45 wt% oil, and 6.35 wt% gas"
The results of vacuum centrifugal separation showed that the separation of solder was complete when the pyrolysis residue was heated at 400 °C, and the rotating drum was rotated at 1200 rpm for 10 min. The pyrolysis oil and gas can be used as fuel or chemical feedstock after treatment. The pyrolysis residue after solder separation contained various metals, glass fibers and other inorganic materials, which could be recycled for further processing. The recovered solder can be reused directly and it can also be a good resource of lead and tin for refining.
Zhou, Y., Wu, W., Qiu, K.
School of Chemistry and Chemical Engineering, Central South University, Changsha Hunan 410083, China
On the synthesis of Bi - based precursors for lead - free solders development
Scopus: "Preliminary studies on the design of lead-free solders precursors by wet chemistry methods are presented. The main objective is to assess the impact of the way of hydroxide precipitates preparation on the metal elements content of the precipitates. Namely, ternary hydroxide mixtures of three systems: a. Cu(II), Bi(III), Sn(II); b. Cu(II), Bi(III), Sb(III); and c. Cu(II), Bi(III), Zn(II) were prepared, firstly, by single-element precipitation and, secondly, by co-precipitation. Thereafter, all mixtures were reduced by using hydrogen gas.
Both, the initial mixtures and the reduced samples were studied by X-ray diffraction, optical and scanning electron microscopes. The chemical compositions of the precipitates were determined experimentally and their dependence on the pH was verified.
It was found that alloying occurred during the reduction procedure, but in some cases the reduction was not complete (i.e. oxide phases rest in the samples). This might be a huge obstacle to use such an approach for the preparation of lead-free solders. Moreover, the materials obtained after reductions apparently are bulk alloys, thus, the preparation of small-sized metal particles would be a challenge. Another key feature to be addressed in future studies is the correlation between the chemical compositions of the parent solution and these of the corresponding precipitates."
SnSbGe high temperatures solder from component manufacture
Factiva: "United States Patent no. 7,816,249, issued on Oct. 19, was assigned to Fuji Electric Systems Co. Ltd. (Tokyo)."
"Method for Producing a Semiconductor Device Using a Solder Alloy" was invented by Akira Morozumi (Nagano, Japan), Shin Soyano (Nagano, Japan) and Yoshikazu Takahashi (Nagano, Japan).
According to the abstract released by the U.S. Patent & Trademark Office: "In producing a semiconductor device, a solder alloy is prepared to contain antimony in a range of from 3 to 5 wt %, a trace amount of germanium, and a balance of tin. An insulative substrate having conductor patterns on both surfaces thereof is prepared, and a heat sink plate is mounted on a back surface of the insulative substrate by a soldering process using the solder alloy at a temperature ranging from 310 C.deg to 320 C.deg in a hydrogen reducing furnace. A semiconductor chip is mounted on a front surface of the insulative substrate."
The patent was filed on June 26, 2008, under Application No. 12/213,923.
Tuesday, October 19, 2010
Use of carbon nanotubes in electronic interconnects
LinkedIn: "I would like to know if any members of this group would be interested in taking part in a project proposal to get FP7 funding for research into the methods needed to measure the interconnect conditions. The aim being to set down some 'standard' conditions that can determine relliability and lifetime constraints."
Monday, October 18, 2010
Interview—David Crimp, Cookson Electronic Materials
Global SMT and Packaging : "David Crimp is a 25-year industry veteran (with a four year gap, as he likes to point out) and executive vice president, Europe, for Cookson Electronic Materials. What he doesn’t know about the European solder business is probably not worth writing about. Trevor Galbraith spoke to him recently about how Cookson seem to have fared better than many in the electronics interconnect business."
You moved your global research and development headquarters to Bangalore, India. What benefits did you gain by moving this key department to Asia?
Our R&D H.Q. remains in the U.S., and our Bangalore facility was opened three years ago to augment our global capabilities. We are constantly enhancing our team with the best young scientists we can find, and India has more honours kids than the U.S. has kids!
Also, this location in Asia puts us right where the action is.
You still do a lot of “blue sky” research when most of the industry has reverted to customer-led development only. Why do you think “blue-sky” is still important?
Of course it’s not all “blue sky” there! In fact, we have a full-line applications support and test facility to support our Asian customer base.
But the fundamental research can get us ahead of the curve. Take halogen-free as an example! We had materials “on the shelf” before there was a market driver.
Disruptive technologies galvanise industries: some of our nano-materials research could revolutionise the die-attach market.
What do you think is driving the trend towards nano-materials, and do we have sufficient reliability data on these materials as an interconnect medium?
Miniaturisation and lead-free are the major drivers. Nano-materials have to create value to the user. In Cookson’s case, nAg for die-attach does. Data is being generated as the material is adopted and will provide a guide to their use in other interconnect applications.
Your SACX materials are a low-silver alternative. Is the conductivity and reliability data comparable or better than SAC305?
Yes, the in-use performance of SACX Plus is comparable to SAC305 and can often improve process yield.
Regarding reliability in the case of impact resistance SACX Plus actually out performs higher silver alloys.
On the absence of the β to α Sn allotropic transformation in solder joints made from paste and metal powder
Scopus: "Until July 2006, most solder joints in the electronics industry were made of the alloy 63Sn37Pb or 62Sn36Pb2Ag. After this date, the European environmental Restriction of Hazardous Substances directive (RoHS) forced many manufacturers to use Pb-free alloys. These substitutes for SnPb are Sn-rich alloys (over 90% Sn) of various compositions. Below 13.2 'C, Sn potentially transforms into a different phase"
This occurs with catastrophic effects, as the transforming material becomes extremely brittle and falls apart. The purpose of this paper is to investigate if this allotropic transformation also occurs in samples prepared from solder paste or metal powder. This work compares the transformation propensity of samples prepared with bulk solder, solder paste, and tin powder. Different conditions and geometries are used in the investigation and experiments with both commercial and specifically prepared solder pastes are carried out. Samples prepared from bulk solder transform into the α phase as expected, whilst samples prepared from solder paste and tin powder do not transform. The residual organic compounds from the flux are believed to be responsible for this behaviour. The tin oxide (SnO2) retained in the bulk after melting could also play a role. This paper shows, for the first time, a relationship between the ability of tin to transform and the nature of the starting material and in particular that the tin β/α allotropic transformation does not occur when samples are prepared from paste or powders. The new lead-free alloys can therefore be used with more confidence in mission-critical applications. © 2010 Elsevier B.V. All rights reserved.
Friday, October 8, 2010
Sharpening Industry's Edge on Tin Whiskers: IPC Conference Convenes Top Industry Experts
Facebook: "The microscopic crystalline structures known as tin whiskers will be the focus of an IPC technical conference and workshops, December 6-7, 2010, in Schaumburg, Ill. IPC Tin Whiskers Conference: Practical Perspectives will convene industry experts from all market sectors to present the latest research and practical methodologies to mitigate the risk of tin whiskers. Presentations will provide real-world examples to illustrate causes of growth, risk mitigation, implications of material selection, methods for detection and failure analysis.
The technical conference will kick off on December 7 with a keynote presentation, “Practical Perspectives on Tin Whiskers,” by Dave Hillman, principal materials and process engineer at Rockwell Collins. Other presentations will explore: controlling the copper substrate roughness and controlling the tin deposit crystal structure; long term investigation of conformal coating; susceptibility testing; evaluations of nanotechnology-based component surface finishes; pressure-induced growth in press-in connections of PCB through-holes; reliability issues from a military perspective; and forensics, using automotive case studies."
The technical conference will kick off on December 7 with a keynote presentation, “Practical Perspectives on Tin Whiskers,” by Dave Hillman, principal materials and process engineer at Rockwell Collins. Other presentations will explore: controlling the copper substrate roughness and controlling the tin deposit crystal structure; long term investigation of conformal coating; susceptibility testing; evaluations of nanotechnology-based component surface finishes; pressure-induced growth in press-in connections of PCB through-holes; reliability issues from a military perspective; and forensics, using automotive case studies."
IPC Efforts to Base RoHS Revision on Scientific Principles May Be Paying Off
Facebook: "Yielding to growing concerns regarding the EU Parliament’s proposal to list thirty-seven substances for priority assessment under a revised RoHS Directive, the Belgian presidency proposed to abandon inclusion of a list of priority substances. Belgium currently holds the rotating EU Presidency and is responsible for chairing the EU Council.
IPC was concerned that the creation of a priority assessment list without scientific assessment would constitute a de facto blacklist. “We are extremely pleased by this turn of events,’ stated Fern Abrams, IPC director of government relations and environmental policy. “By setting aside their call for a list of substances for priority assessment, the Belgian Presidency is acknowledging our advocacy, echoed by the EU Commission and many EU member states, for a scientifically-based RoHS Directive.” Revision of the RoHS Directive will require agreement between the EU Council, Commission and Parliament."
IPC was concerned that the creation of a priority assessment list without scientific assessment would constitute a de facto blacklist. “We are extremely pleased by this turn of events,’ stated Fern Abrams, IPC director of government relations and environmental policy. “By setting aside their call for a list of substances for priority assessment, the Belgian Presidency is acknowledging our advocacy, echoed by the EU Commission and many EU member states, for a scientifically-based RoHS Directive.” Revision of the RoHS Directive will require agreement between the EU Council, Commission and Parliament."
EU presidency seeks to drop proposed Annex III of RoHS
Chemical Watch: "The planned list of priority substances to be assessed for possible prohibition under the proposed recast of the EU Directive on the restriction of hazardous substances (RoHS) in electrical and electronic equipment, is likely to be ditched in favour of a non-binding political statement, according to sources close to the discussions. After a meeting of the Member State permanent representatives to the Council (COREPER) on Wednesday and a trialogue..."
Thursday, October 7, 2010
EU presidency seeks to scrap RoHS 'priority list'
ENDS: The prospect of a first reading agreement on new EU rules for hazardous substances in electronics (RoHS) appeared dim this week as the Belgian EU presidency proposed to abandon a list of priority substances that may eventually be banned.
Such a list was included in the European Commission's original proposal, but it only included four substances of very high concern. In June the parliament's environment committee voted to drastically expand this list to 37 substances.
In the latest Belgian proposal, seen by ENDS, the four original substances proposed by the EU executive are instead mentioned in a recital saying their risks should be considered in the future. Most member states support this, ENDS understands.
The Belgian text also contains no ban on nanosilver, which MEPs had voted to include on a list of banned substances appearing in annex 4 of the RoHS directive. There are no labelling requirements for material containing nanomaterials as proposed by MEPs, and no obligation to provide safety data on such materials to the commission.
The next trialogue meeting on the issue is scheduled for Thursday. On Wednesday member states will prepare their position at working group level, and separately, the shadow rapporteurs in the parliament will meet to discuss their position. There is also disagreement between the two institutions over the start date for an 'open scope'.
The shadow rapporteurs did not want to discuss the presidency's proposal before they meet. But centre-right MEPs were opposed to the addition of a large number of substances to the priority list and may be receptive to scrapping the list altogether. Green MEPs have indicated they are open to removing some substances from this list.
Tuesday, October 5, 2010
New iNEMI project on lead-free solder alternatives
EMS007 Perspectives: Cutting Through the Lead-Free Alloy Clutter: "iNEMI has organized an industry effort to define important properties and the methodologies to test for those properties to acceptable standards. As defined, 'This is a new initiative that is a follow-on to the 'Pb-Free Alloy Alternative Project' (which will be outlined below). The project, led by Co-Chairs Greg Henshall of Hewlett-Packard and Stephen Tisdale of Intel, is now 'working on characterization of Pb-free alloy alternatives, with two main thrusts:
The first is to characterize the thermal fatigue and acceleration behavior of alternative alloys through accelerated thermal cycle testing.
The second is to develop a set of test data requirements that will allow OEMs and others to evaluate alloy properties against their requirements.
These requirements and recommended testing methods will be proposed to the IPC Solder Products Value Council to consider for standardization"
The first is to characterize the thermal fatigue and acceleration behavior of alternative alloys through accelerated thermal cycle testing.
The second is to develop a set of test data requirements that will allow OEMs and others to evaluate alloy properties against their requirements.
These requirements and recommended testing methods will be proposed to the IPC Solder Products Value Council to consider for standardization"
Alpha's Alan Plant to Present at Tallin Reliability Summit
Low silver alloys are now commonplace in the production of solder spheres for BGA and CSP components but their adoption in solder paste formulation and use has been slower and more conservative.
Plant’s presentation, 'The effect of mixing BGA and solder paste alloys on the formation of voids,' highlights a potential problem arising when assemblies are produced using spheres and solder pastes with different alloy compositions.
Hugely experienced, Plant has been an invaluable member of the Alpha team for the past 7 years. A metallurgist by training, he has been involved in electronics assembly for some 27 years overall, having held several positions within ICL and Celestica before his time with Alpha."
Plant’s presentation, 'The effect of mixing BGA and solder paste alloys on the formation of voids,' highlights a potential problem arising when assemblies are produced using spheres and solder pastes with different alloy compositions.
Hugely experienced, Plant has been an invaluable member of the Alpha team for the past 7 years. A metallurgist by training, he has been involved in electronics assembly for some 27 years overall, having held several positions within ICL and Celestica before his time with Alpha."
Characterization of lead-free solder and sintered nano-silver die-attach layers using thermal impedance
Scopus: "To check the degradation of the die-attachment, three samples using three die-attach materials were thermally cycled from -40'C to 125'C. The experimental results show that after 500 cycles, the thermal impedance of SAC305 samples and SN100C samples is increased by 12.8% and 15% respectively, which is much higher than the sample using nano-silver paste for die-attach (increased by 4.1%)"
Influence of minor Ag nano-particles additions on the microstructure of Sn30Bi0.5Cu solder
Scopus: "Ag nano-particle reinforced SnBiCu-xAg (x=1, 2, 5) composite solder pastes were prepared by a mechanical mixing method and then were reflowed on Cu substrates. Three cooling methods (furnace cooling, air cooling and water cooling) were adopted in this study.
Microstructural evolution of composite solder matrices and the intermetallic compound (IMC) layers formed in solder joints were investigated by microstructural observation and phase analysis. The addition of Ag nano-particles did not change the microstructure of solder matrices apparently both in the furnace cooled and water cooled samples. In the air cooled samples, Bi-rich grains were refined in the composite solder matrices due to the adsorption of Ag3Sn micro-particles on them. The growth of Cu6Sn5 IMC layers in air cooled SnBiCu-xAg/Cu solder joints was influenced by the adsorption of Ag3Sn micro-particles both on the surface of Cu6Sn5 layers and on the surface of the Bi-rich grains"
Peng, C., Shen, J., Xie, W., Chen, J., Wu, C., Wang, X.
College of Material Science and Engineering, Chongqing University, Chongqing, 400044, China
Balver Zinn SN100CS with Ge
EMSNow: "Our SN100CS™ is a variant of SN100C™. It helps to make optimal solder available for each specific application. This eagerly anticipated development in the highly regarded SN100C™ solder range has a content of 100 ppm (0.01 percent) of germanium (Ge).
In the SN100C™ formulation, Ge plays the vital role of the antioxidant, providing a preferential reaction with oxygen to protect the solder from oxidation, which results in the formation of dross. The greater content of germanium in the SN100CS™ solder renders it especially suitable for applications without nitrogen. This new solder also offers all of the same advantages that have made Balver Zinn's SN100C™ so popular with leading manufacturers around the globe, including its substantially reduced copper dissolution. The lower surface tension of the solder surface deoxidized with Ge also results in improved wetting and flow"
The study of mechanical properties of Sn-Ag-Cu lead-free solders with different Ag contents and Ni dopin
Scopus: "Test results show that the elastic modulus, yield stress and ultimate tensile strength increase with increasing strain rate and Ag content, but they decrease with increasing temperature. The elastic modulus, yield stress and ultimate tensile strength are lower and the elongation is larger for Sn-1.0Ag-0.5Cu-0.05Ni solder compared with Sn-1.0Ag-0.5Cu-0.02Ni solder.
The strain rate and Ag content dependent mechanical property models have been developed for Sn-Ag-Cu solders for the first time. In addition, the temperature and rate-dependent mechanical property models have also been developed for Sn-1.0Ag-0.5Cu-0.02Ni solder. The microstructures of solders were also analyzed. The Ag content affects Ag 3Sn intermetallic compound dispersion and Sn dendrite size. The microstructures of solder have fine Sn dendrites and more dispersed IMC particles for the high Ag content solder, which makes the solder exhibit high strength and yield stress"
Che, F.X.a b c , Zhu, W.H.b , Poh, E.S.W.b , Zhang, X.W.a , Zhang, X.R.b
a Institute of Microelectronics, ASTAR (Agency for Science Technology and Research), 11 Science Park Road, Singapore 117685, Singapore
b United Test and Assembly Center Ltd., 5 Serangoon North Ave 5, Singapore 554916, Singapore
c Institute of Microelectronics, 11 Science Park Road, Singapore 117685, Singapore
'Beyond Solder' conclusions
PCB007: "In conclusion, he commented that solder technology would not be easily replaced in the high-volume PCB assembly market, although it had, to a large extent, been replaced in die attach, device interconnect and package sealing. There were alternatives to solder for higher temperature applications, but these would need to be considered at an early design stage in conjunction with device and packaging materials, interconnect, layout and production requirements."
The effects of the soldering process on whisker growth on solder alloys
Scopus: "Different soldering methods resulted in varying degrees of copper erosion along with different distribution of flux residues, and subsequently different rates and locations of corrosion. It is concluded from these observations that the soldering method as well as the type of flux gives significant influence on the subsequent corrosion when exposed to high temperature and humidity conditions. Consequently, this also gives extensive effects on the onset time of whisker appearance and maximum whisker length"
Flexible, Conductive Adhesive replaces solder in solar cells
Creative Materials: "Significant pressures from many quarters confront the solar industry to both lower raw materials costs and increase product efficiency, in order to compete effectively with traditional grid power systems. New product advances can offer solutions. Among the industry's challenges is to replace solder materials.
Solder is neither environmentally acceptable, nor is it an efficient bonding agent as the solar industry looks for more cost-efficient materials and solutions. The industry trend is to produce thinner solar cells with greater surface area, in order to reduce material costs. Solder does not provide sufficient flexibility to bond effectively to crystalline silicon solar cells. Moreover, the CTE of the rigid solder interconnect is not compatible with the solar cell material, which results in more breaking and cracking of cells"
SAC+ Review paper
Factiva: "Recent years, the SnAgCu family of alloys has been found a widely application as a replacement for the conventional SnPb solders in electronic industry. In order to further enhance the properties of SnAgCu solder alloys, alloying elements such as rare earth, Bi, Sb, Fe, Co, Mn, Ti, In, Ni, Ge and nano-particles were selected by lots of researchers as alloys addition into these alloys,' researchers in Nanjing, People's Republic of China report.
'Rare earth (RE) elements have been called the ''vitamin'' of metals, which means that a small amount of RE elements can greatly enhance the properties of metals, such as microstructure refinement, alloying and purification of materials and metamorphosis of inclusions. In addition, a small amount of Zn addition has the ability to reduce undercooling efficiently and suppress the formation of massive primary Ag3Sn plates, and Bi/Ga has the ability to enhance the wettability of SnAgCu alloys as well as Ni. Moreover, adding Co/Fe/Ge can effectively refine microstructure, modify interfacial Cu-Sn compounds and increase the shear strength of joints with Cu,' wrote L.L. Gao and colleagues, NanJing University"
'Rare earth (RE) elements have been called the ''vitamin'' of metals, which means that a small amount of RE elements can greatly enhance the properties of metals, such as microstructure refinement, alloying and purification of materials and metamorphosis of inclusions. In addition, a small amount of Zn addition has the ability to reduce undercooling efficiently and suppress the formation of massive primary Ag3Sn plates, and Bi/Ga has the ability to enhance the wettability of SnAgCu alloys as well as Ni. Moreover, adding Co/Fe/Ge can effectively refine microstructure, modify interfacial Cu-Sn compounds and increase the shear strength of joints with Cu,' wrote L.L. Gao and colleagues, NanJing University"
S.B. Xue, Nanjing University Aeronaut & Astronaut, College Materials Science & Technology, Nanjing 210016, People's Republic of China.S
Nanocomposite SnBi solder bumps
Factiva: "SiC-mixed Sn-58Bi composite solder bumps were successfully fabricated via an electroplating process. For the composite solder bump fabrication, ultrasonically dispersed SiC nanoparticles were added to the plating solutions,' scientists writing in the journal Surface Review and Letters report.
'DSC analysis indicated that the melting temperature of SiCmixed Sn-58Bi solders was the same as that of the non-mixed Sn-58Bi. Shear strengths of Sn-58Bi SiC solder bumps were 6% higher than that of non-mixed solder bumps. The thicknesses of intermetallic compound were almost the same for both Sn-58Bi and Sn-58Bi SiC samples. The Sn-58Bi SiC composite solder bumps had finer lamellar structures than non-mixed Sn-58Bi. From the fracture surface analysis, fracture occurred at solder bump matrix, not at joint interface,' wrote Y.S. Shin and colleagues.
The researchers concluded: 'Therefore, the addition of the SiC nanoparticles in the Sn-58Bi solders decreased the grain sizes, which increased the shear strengths"
'DSC analysis indicated that the melting temperature of SiCmixed Sn-58Bi solders was the same as that of the non-mixed Sn-58Bi. Shear strengths of Sn-58Bi SiC solder bumps were 6% higher than that of non-mixed solder bumps. The thicknesses of intermetallic compound were almost the same for both Sn-58Bi and Sn-58Bi SiC samples. The Sn-58Bi SiC composite solder bumps had finer lamellar structures than non-mixed Sn-58Bi. From the fracture surface analysis, fracture occurred at solder bump matrix, not at joint interface,' wrote Y.S. Shin and colleagues.
The researchers concluded: 'Therefore, the addition of the SiC nanoparticles in the Sn-58Bi solders decreased the grain sizes, which increased the shear strengths"
C.W. Lee, Korea Institute Ind Technology, Microjoining Center, 7-47 Songdo Dong, Inchon 406840, South Korea.
Paste print tool uses embedded electronics for finer pitches
Advanced Packaging: "DEK has launched ProActiv process technology to enable electronics manufacturers to print pastes with high-density heterogeneous PCBs and ultra fine pitch assemblies such as advanced package assembly. Advanced printing can take place with a conventional printing process with a single thickness stencil.
As the stencil aperture area ratio decreases with the emergence of miniaturization and heterogeneous assemblies, the chance of successful printing decreases. Each ProActiv installation contains a control subsystem and a set of squeegees featuring embedded electronics."
As the stencil aperture area ratio decreases with the emergence of miniaturization and heterogeneous assemblies, the chance of successful printing decreases. Each ProActiv installation contains a control subsystem and a set of squeegees featuring embedded electronics."
RoHS 1st reading approval less likely
Directive Decoder: "Trialogue meetings have been taking place between the European Commission, European Parliament and Council of Ministers to smooth the way for a first reading approval on the RoHS recast.
However, with two meetings left there has not been the anticipated progress and negotiations may well go in to next year.
Directive Decoder"
However, with two meetings left there has not been the anticipated progress and negotiations may well go in to next year.
Directive Decoder"
Design and demonstration of self-healing behavior in a lead-free solder alloy
Scopus: "A critical review of self-healing behavior in metals and metal composites with a focus on the opportunities and challenges inherent to their design and application will be presented. In this work, a self-healing composite (SHC) is designed, consisting of carbon fiber microtubes filled with a low melting temperature alloy imbedded within a lead-free solder alloy having a higher melting point than the filler alloy.
In this concept, when the SHC is damaged or cracked, heat can be applied to the affected area whereupon the low melting alloy will melt and flow into the crack. Once heat is removed, the filler will solidify, sealing the crack to effectively heal the damaged alloy. This will lead to a decrease in the electrical resistivity of the healed composite compared to the damaged material."
Improvement of flux-less, lead-free solder wettability
Scopuss: "Atmospheric pressure non-equilibrium plasma inducted CF4 gas was irradiated to Sn and Ag substrates to obtain fluorinated Sn and Ag surfaces with a high affinity of a lead-free solder without fluxes.
The plasma was produced by applying microwave power inducted with Ar-CF4-O2 mixed gases. The plasma irradiation successfully fluorinates the metal surfaces completed within 15 min. The fluorinated metal surfaces were observed using a scanning electron microscopy (SEM) and analyzed using an X-ray photoelectron spectroscopy (XPS). The Sn and Ag surfaces were covered mainly with SnF2 and AgF2 through the plasma irradiation respectively.
The contact angle of the solder mounted on the metal substrates was measured to evaluate the wettability. The contact angle was minimized at the flow ratio of CF4/O2 which was 1/9. Surface fluorination by non-equilibrium plasma irradiation would be applicable to improve the wettability of flux-less solder"
RoHS Review video interview on exemptions
Real Time With... Electronics Midwest 2010
On Friday, September 24, 2010, the European Union published an update to the RoHS Directive. Krista Botsford explains the exemption numbering, expiration dates and some basic steps a company should take to keep up to date.
RoHS Review video interview on exemptions
Real Time With... Electronics Midwest 2010
On Friday, September 24, 2010, the European Union published an update to the RoHS Directive. Krista Botsford explains the exemption numbering, expiration dates and some basic steps a company should take to keep up to date.
Monday, October 4, 2010
Examining the impact of tin whiskers
IPC Feature article: "“There are a lot of misconceptions about what tin whiskers are, what causes them and what impact they have. The term evokes terror in electronics circles, it’s almost like bird flu or swine flu, something that’s going to wipe out the free world as we know it,” said Sam Platt, manufacturing development engineering manager at Delphi Electronics and Safety.
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
Examining the impact of tin whiskers
IPC Feature article: "“There are a lot of misconceptions about what tin whiskers are, what causes them and what impact they have. The term evokes terror in electronics circles, it’s almost like bird flu or swine flu, something that’s going to wipe out the free world as we know it,” said Sam Platt, manufacturing development engineering manager at Delphi Electronics and Safety.
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
Examining the impact of tin whiskers
IPC Feature article: "“There are a lot of misconceptions about what tin whiskers are, what causes them and what impact they have. The term evokes terror in electronics circles, it’s almost like bird flu or swine flu, something that’s going to wipe out the free world as we know it,” said Sam Platt, manufacturing development engineering manager at Delphi Electronics and Safety.
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
He will be describing Delphi’s experiences with tin whiskers at the IPC conference at Electronics Midwest in Rosemont, Ill. That runs from September 28–30. Platt will be one of five speakers in a session entitled Product Sustainability: Managing Tin Whiskers and Product Lifecycle Analysis."
IPC EMS Military Conference
IPC EMS Military Conference: "f you supply the military or are planning to, the IPC Conference for the North American EMS Industry: What It Takes to Supply the Military is for you.
By providing solutions to the many complex challenges faced by EMS suppliers to the military, this event will uniquely position you for success. The day will begin with, 'Department of Defense Electronics Challenges and Opportunities' a keynote address by Brett B. Lambert, Director of Industrial Policy in the Office of the Assistant Secretary of Defense for Acquisition."
By providing solutions to the many complex challenges faced by EMS suppliers to the military, this event will uniquely position you for success. The day will begin with, 'Department of Defense Electronics Challenges and Opportunities' a keynote address by Brett B. Lambert, Director of Industrial Policy in the Office of the Assistant Secretary of Defense for Acquisition."
Tuesday, September 21, 2010
SRC GeorgiaTech research to replace solder with copper in flip-chip
Semiconductor Research Corporation - SRC: "The second advancement is the actual connection between the chip and substrate. Both the chip and the substrate use copper wiring. The weak link between them is the solder, which is the only non-copper element in the pathway. Solders are mechanically brittle and limit both the density and performance of flip-chip connections between chips and boards. Georgia Tech researchers are replacing solder with all-copper connections, which are made into non-spherical structures, such as shielded, co-axial or other shapes that enable higher densities and performance than current solder materials.
Not only does this approach support continued system performance improvements, but also provides an environmental improvement by creating a smaller chemical footprint during fabrication."
Not only does this approach support continued system performance improvements, but also provides an environmental improvement by creating a smaller chemical footprint during fabrication."
Selective soft laser soldering
OptoIQ: "With regard to peel force and contact resistance, the quality of the laser soldered joints exceeds that of other contacting technologies. The peel force is higher by a factor of 3, whereas the thermal resistance is only about 14% of the contact solder joint.
DILAS, the diode laser company, is focused on delivering the most innovative technologies and advanced product solutions for the industrial market. Diode-based laser soldering is one example.
For further information, please contact Dave MacLellan, sales manager, Micro Division, Rofin-Baasel UK Limited, sales@rofin-baasel.co.uk."
DILAS, the diode laser company, is focused on delivering the most innovative technologies and advanced product solutions for the industrial market. Diode-based laser soldering is one example.
For further information, please contact Dave MacLellan, sales manager, Micro Division, Rofin-Baasel UK Limited, sales@rofin-baasel.co.uk."
Poll Results: On lead-free hand soldering
Poll Results:: "When asked 'Can you get on with lead-free hand soldering?', 24% responded Yes (but it looks worse than tin-lead), another 24% also responded Yes (but it is a struggle) and a completely happy 6% said Yes (and it looks great!). In total, 54% responded positively (however qualified the approval was)."
Conductive adhesives offer alternative to traditional solder connections for c-Si solar modules
EETimes: "The Hysol Eccobond CA3556HF from Henkel offers an alternative to traditional solder connections used for c-Si solar modules which can be problematic for emerging thin, fragile solar cells. The compound has been formulated to deliver low temperature curing at 150'C and an exceptionally fast cure time of five seconds.
The material provides an excellent bond between the Ag and SnPbAg coated tabs and the c-Si cells, delivering a stable and reliable electrical connection over the life of the module. Thin-film module manufacturers have also successfully incorporated this material into processes that dictate low-stress, fast curing interconnection of cells and ribbons."
The material provides an excellent bond between the Ag and SnPbAg coated tabs and the c-Si cells, delivering a stable and reliable electrical connection over the life of the module. Thin-film module manufacturers have also successfully incorporated this material into processes that dictate low-stress, fast curing interconnection of cells and ribbons."
Effect of Ag content on the microstructure of Sn-Ag-Cu based solder alloys
Soldering & Surface Mount Technology: "By using XRD analysis in addition to energy dispersive spectroscopy (EDS) it was found that the main intermetallics were Cu6Sn5 and Ag3Sn in a Sn matrix. Plate-like ?-Ag3Sn intermetallics were observed for all four alloys. Solder alloys SAC105, SAC205 and SAC305 showed a similar microstructure, while SAC405 displayed a fine microstructure with intermetallic phases dense within the Sn matrix.
Originality/value – Currently, low-silver content SAC alloys are being investigated due to their lower cost, however, the overall reliability of an alloy can be greatly affected by the microstructure and this should be taken into consideration when choosing an alloy. The size and number of Ag3Sn plate-like intermetallics can affect the reliability as they act as a site for crack propagation."
Originality/value – Currently, low-silver content SAC alloys are being investigated due to their lower cost, however, the overall reliability of an alloy can be greatly affected by the microstructure and this should be taken into consideration when choosing an alloy. The size and number of Ag3Sn plate-like intermetallics can affect the reliability as they act as a site for crack propagation."
M. Reid, (CTVR, Stokes Institute, University of Limerick, Ireland), J. Punch, (CTVR, Stokes Institute, University of Limerick, Ireland), M. Collins, (CTVR, Stokes Institute, University of Limerick, Ireland), C. Ryan, (CTVR, Stokes Institute, University of Limerick, Ireland)
Citation: M. Reid, J. Punch, M. Collins, C. Ryan, (2008
Cu alloy, Bi powder low temperature lead-free solder
Factiva: "Provided is a metal filler comprising a mixture of first metal particles with second metal particles, wherein the first metal particles are Cu-alloy particles containing Cu as the major component, which is an element being present at the highest ratio by mass, together with In and Sn; the second metal particles are Bi-alloy particles containing 40-70% by mass of Bi together with 30-60% by mass of one or more metals selected from among Ag, Cu, In and Sn; and the content of the second metal particles is 40-300 parts by mass per 100 parts by mass of the first metal particles. Also provided are a lead-free solder containing the aforesaid metal filler, a bonded structure formed by using the aforesaid lead-free solder, and a substrate to which a part provided with the aforesaid bonded structure is mounted"
Publication No. WO/2010/098357 was published on Sept. 02.
Title of the invention: "METAL FILLER, LOW-TEMPERATURE-BONDING LEAD-FREE SOLDER AND BONDED STRUCTURE."
Applicants: Asahi Kasei E-materials Corporation (JP).
Inventors: Tomonori Kiyama (JP) and Norihito Tanaka (JP)
Publication No. WO/2010/098357 was published on Sept. 02.
Title of the invention: "METAL FILLER, LOW-TEMPERATURE-BONDING LEAD-FREE SOLDER AND BONDED STRUCTURE."
Applicants: Asahi Kasei E-materials Corporation (JP).
Inventors: Tomonori Kiyama (JP) and Norihito Tanaka (JP)
Properties of SnAgCu/SnAgCuCe soldered joints for electronic packaging
Scopus: "For quad flat packages (QFP256), lead-free soldered joints reliability in service is a critical issue. In this paper, soldering experiments of quad flat package (QFP256) devices were carried out by means of infrared reflow soldering system with Sn-3.8Ag-0.7Cu and Sn-3.8Ag-0.7Cu-0.03Ce lead-free solders, respectively, and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR micro-joints tester. The results indicate that the tensile strength of Sn-Ag-Cu-Ce soldered joints is better than that of Sn-Ag-Cu soldered joints. In particular, the addition of trace Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the intermetallic compound layer of Sn-Ag-Cu solder alloys. In addition, the stress-strain response of Sn-Ag-Cu/Sn-Ag-Cu-Ce soldered joints in quad flat packaging was investigated using finite element method based on Garofalo-Arrhenius model. The simulated results indicate creep distribution of soldered joints is not uniform, the heel and toe of soldered joints, the area between soldered joints and leads are the creep concentrated sites. The creep strain of Sn-Ag-Cu-Ce soldered joints is lower than that of Sn-Ag-Cu soldered joints"
Zhang, L.a , Xue, S.-B.a , Gao, L.-L.a , Sheng, Z.a , Zeng, G.a , Chen, Y.b , Yu, S.-L.a c
a College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, China
b Harbin Welding Institute, 150080 Harbin, China
c 14th Research Institute, China Electronics Technology Group Corporation, 210013 Nanjing, China
Effects of nano-structured particles on microstructure and microhardness of Sn-Ag solder alloy
Scopus: "In this research, the typical nano-structured Polyhedral Oligomeric Silsesquioxane (POSS) particles were incorporated into the Sn-3.5Ag eutectic solder paste by mechanically mixing to form lead-free composite solder. The effects of nano-structured POSS additions on the microstructure and mechanical properties of as-fabricated composite solder alloys were systematically investigated. Experimental results indicated that the average size and spacing distance of Ag3Sn intermetallic compounds (IMCs) in composite solder matrix decreased as compared to the Sn-3.5Ag eutectic solder. The 3 wt% addition of nano-structured POSS particles could enhance the microhardness of composite solder by 18.4% compared with the Sn-3.5Ag eutectic solder matrix. The average grain size and spacing distance of Ag3Sn IMCs in Sn-Ag 3 wt% POSS composite solder matrix reduced from 0.35 to 0.23 μm and from 0.54 to 0.32 μm, respectively. The refined Ag3Sn IMCs, acting as a strengthening phase in the solder matrix, could enhance the microhardness of the composite solders"
Tai, F., Guo, F., Xia, Z.D., Lei, Y.P., Shi, Y.W.
College of Materials Science and Engineering, Beijing University of Technology, 100 Ping Le Yuan, Chaoyang District, Beijing 100124, China
The study of mechanical properties of Sn-Ag-Cu lead-free solders with different Ag contents and Ni doping under different strain rates and temperature
Scopus: "In this paper, the tensile tests were conducted at 25'C to investigate the effect of Ag content and Ni doping on the microstructures and mechanical properties of Sn-3.0Ag-0.5Cu, Sn-2.0Ag-0.5Cu, Sn-1.0Ag-0.5Cu, Sn-1.0Ag-0.5Cu-0.05Ni and Sn-1.0Ag-0.5Cu-0.02Ni solders. The effect of strain rate on mechanical properties was investigated for each solder using stain rates of 10-5 s-1, 10-4 s-1, 10-3 s-1, 10-2 s-1 and 10-1 s-1. In addition, the effect of temperature on mechanical properties was investigated for Sn-1.0Ag-0.5Cu-0.02Ni solder by conducting tests at -35 'C, 25 'C, 75 'C and 125 'C."
Test results show that the elastic modulus, yield stress and ultimate tensile strength increase with increasing strain rate and Ag content, but they decrease with increasing temperature. The elastic modulus, yield stress and ultimate tensile strength are lower and the elongation is larger for Sn-1.0Ag-0.5Cu-0.05Ni solder compared with Sn-1.0Ag-0.5Cu-0.02Ni solder. The strain rate and Ag content dependent mechanical property models have been developed for Sn-Ag-Cu solders for the first time. In addition, the temperature and rate-dependent mechanical property models have also been developed for Sn-1.0Ag-0.5Cu-0.02Ni solder. The microstructures of solders were also analyzed. The Ag content affects Ag3Sn intermetallic compound dispersion and Sn dendrite size. The microstructures of solder have fine Sn dendrites and more dispersed IMC particles for the high Ag content solder, which makes the solder exhibit high strength and yield stress
Che, F.X.a b , Zhu, W.H.b , Poh, E.S.W.b , Zhang, X.W.a , Zhang, X.R.b
a Institute of Microelectronics, ASTAR (Agency for Science, Technology and Research), 11 Science Park Road, Singapore Science Park II, Singapore 117685, Singapore
b United Test and Assembly Center Ltd., 5 Serangoon North Ave 5, Singapore 554916, Singapore
The influence of addition of Al nano-particles on the microstructure and shear strength of eutectic Sn-Ag-Cu solder on Au/Ni metallized Cu pads
Scopus : "In Sn-Ag-Cu solder joints and solder joints containing Al nano-particles, a scallop-shaped Sn-Ni-Cu intermetallic compound layer was clearly observed at the interfaces after long time aging and multiple reflows, and the intermetallic compound layer thickness was substantially increased with an increase in the number of reflow cycles as well as the aging time. However, after the addition of Al nano-particles, an additional Sn-Al-Ag intermetallic compound was found on the top surface of the Sn-Ni-Cu intermetallic compound layer. The Sn-Ag-Cu solder joints containing 3 wt% Al nano-particles consistently displayed a higher shear strength than that of the plain Sn-Ag-Cu solder joints as well as a lower Al nano-particle content as a function of reflow cycles and aging time due to a second phase dispersion strengthening mechanism by the formation of fine Sn-Ag-Al intermetallic compound particles as well as a controlled fine microstructure"
Gain, A.K.a , Fouzder, T.a , Chan, Y.C.a , Sharif, A.b , Wong, N.B.c , Yung, W.K.C.d
a Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong
b Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
c Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong
d Department of Industrial and Systems Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
A novel cyclic process involving zinc for separating silver from lead-free solder residue
Scopus: "In this study, a novel cyclic process to separate silver from the lead-free solder residues using a metal solvent has been developed. The process uses zinc as a metal solvent which selectively forms intermetallic compounds with silver, followed by the volatilization separation step to recover zinc which can be reused as the metal solvent. Based on the results obtained, up to 90% of the silver in a lead-free solder residue was calculated to be separated into the dross phase through the sixth silver separation stage using the proposed process"
Implementation and Characterization of a Medical Ultrasound Phased Array Probe With New Pb-Free Soldering Materials
Scopus: "This paper shows the use of conductive adhesives for the implementation of a medical phased array probe, where the soldering material is located among a platelet of the piezoelectric and fingers. A comparison between electroacoustic measures on the elements soldered with an ECA and with the traditional technology Sn-Pb will be also shown. Moreover, in the field of biomedical application, it is also fundamental to assure that the performances of the transducer are maintained in the time. To this aim, some laboratory tests for the evaluation of the reliability performances of the new Pb-free soldering material are proposed, and the preliminary results are presented in this paper."
Oxidation of liquid solders for die attachment
Scopus: "This study deals with thermal oxidation behaviour in the liquid state of a commonly-used die-attach solder, Pb-Sn, and its potential Pb-free alternatives (Bi-Ag and Zn-Sn) from viewpoints of thermodynamics and kinetics. The characteristics of the oxidation reaction layers were investigated using XPS, XRD and AES. The superior performance in oxidation prevention of the Zn based alloys can be ascribed to their stable oxidative product, ZnO, which exhibits low free energy of formation, as well as slow growth rate"
Song, J.-M., Cheng, Y.-M., Tsai, C.-H.
Department of Materials Science and Engineering, National Dong Hwa University, Hailien 974, Taiwan
Effect of adding Ce on interfacial reactions between Sn-Ag solder and Cu
Scopus: "We investigated the effect of adding cerium (Ce) to low Ag content Sn-1.0wt.%Ag solder on the interfacial reactions between the Sn-1.0Ag solder and Cu substrate. The formation and growth of interfacial intermetallic compounds (IMCs) between the Sn-1.0Ag-0.3Ce solder and Cu substrate were studied and the results were compared to those obtained for the Ce-free Sn-1.0Ag/Cu and most promising Sn-3.0Ag-0.5Cu/Cu systems. The addition of Ce to the Sn-Ag solder significantly reduced the growth of the interfacial Cu-Sn IMCs, retarded the interfacial reactions between the solder and the substrate, and prevented the IMC from spalling from the interface. The Sn-1.0Ag-0.3Ce solder alloy had a good interfacial stability with the Cu substrate during solid-state isothermal aging in the viewpoint of IMC growth"
Yoon, J.-W., Noh, B.-I., Choi, J.-H., Jung, S.-B.
School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, 440-746, South Korea
Robust, simplified and solder-free assembly processing of electronics products
Scopus: "This paper describes a new solder-free electronics assembly process tentatively being called The OCCAM Process, in honor of the 14th century English philosopher and logician whose words inspired the concepts found herein. Products built by this process are expected to be more reliable than previous solder-free strategies (for example, using conductive adhesive as a solder substitute) as well as traditionally manufactured soldered assemblies. The process is a reverse-order interconnection solution that employs mature, low-risk, familiar core processing technologies in a novel sequence. Components are interconnected by means of copper plating after they are assembled into their final positions in an encapsulated module, thus doing away with conventional printed circuit boards. Prototype assemblies using this new technology are currently being characterized."
Fjelstad, J.
Verdant Electronics Inc., Sunnyvale, CA, United States
Technical Paper - Society of Manufacturing Engineers
Volume TP07PUB191, 2007, 26p
The effect of ultrasound on the gold plating of silica nanoparticles for use in composite solders
Scopus: "In order to produce electronic devices that can survive harsh environments it is essential that the solder joints are very reliable and this has led to the development of composite solders. One approach to the manufacture of such solders is to disperse silica nanoparticles into it to improve their mechanical and fatigue characteristics. However, this is difficult to achieve using bare silica particles because they are not 'wettable' in the solder matrix and so cannot be dispersed efficiently. In an attempt to alleviate this issue it has been found that if the silica nanoparticles are first plated with gold then this problem of wetting can, to some extent, be overcome. However, the particles must be completely encapsulated with gold which, using the method previously described by workers at Kings College London, was found to be difficult to accomplish.
In this short communication the effect of ultrasound on the gold coverage is described. Different frequencies of ultrasound were used (20, 850 and 1176 kHz) and it was found that higher frequencies of ultrasound improved the coverage and dispersion of the gold nanoparticles over silica during the seeding step compared to simple mechanical agitation. This subsequently led to a more complete encapsulation of gold in the plating stag"
Cobley, A.J.a , Mason, T.J.a , Alarjah, M.a , Ashayer, R.b , Mannan, S.H.b
a The Sonochemistry Centre, Coventry University, Faculty of Health and Life Science, Priory Street, Coventry, CV1 5FB, United Kingdom
b Department of Mechanical Engineering, Kings College London, Strand, London, United Kingdom
The effect of ultrasound on the gold plating of silica nanoparticles for use in composite solders
Scopus: "In order to produce electronic devices that can survive harsh environments it is essential that the solder joints are very reliable and this has led to the development of composite solders. One approach to the manufacture of such solders is to disperse silica nanoparticles into it to improve their mechanical and fatigue characteristics. However, this is difficult to achieve using bare silica particles because they are not 'wettable' in the solder matrix and so cannot be dispersed efficiently. In an attempt to alleviate this issue it has been found that if the silica nanoparticles are first plated with gold then this problem of wetting can, to some extent, be overcome. However, the particles must be completely encapsulated with gold which, using the method previously described by workers at Kings College London, was found to be difficult to accomplish.
In this short communication the effect of ultrasound on the gold coverage is described. Different frequencies of ultrasound were used (20, 850 and 1176 kHz) and it was found that higher frequencies of ultrasound improved the coverage and dispersion of the gold nanoparticles over silica during the seeding step compared to simple mechanical agitation. This subsequently led to a more complete encapsulation of gold in the plating stag"
Cobley, A.J.a , Mason, T.J.a , Alarjah, M.a , Ashayer, R.b , Mannan, S.H.b
a The Sonochemistry Centre, Coventry University, Faculty of Health and Life Science, Priory Street, Coventry, CV1 5FB, United Kingdom
b Department of Mechanical Engineering, Kings College London, Strand, London, United Kingdom
Proposed TSCA IUR rule specifically calls out electronics industry
EMSNow: "Electronics manufacturers who send byproducts and waste for recycling are included among the targets of a proposed rule from the EPA published on August 13.
The rule expands the reporting requirements under the Toxic Substances Control Act (TSCA) Inventory Update Reporting (IUR) rule that requires manufacturers of chemical substances to report on the manufacturing, importation, processing, and use of those chemical substances. The EPA estimates it will cost each facility $48,700 and take 792 hours to comply with the proposed rule."
The rule expands the reporting requirements under the Toxic Substances Control Act (TSCA) Inventory Update Reporting (IUR) rule that requires manufacturers of chemical substances to report on the manufacturing, importation, processing, and use of those chemical substances. The EPA estimates it will cost each facility $48,700 and take 792 hours to comply with the proposed rule."
SMTA China and Hong Kong Chapter Announce 2010 Best Paper/Presentation and Best Exhibit Awards
EMSNow: "SMTA China announced the Best Paper/Presentation and Best Exhibit Awards at its annual awards presentation held in conjunction with the SMTA China 5th Anniversary Keynote Breakfast Reception, which took place September 1, 2010 at the Futian Shangri-la, Shenzhen Hotel."
Nihon Superior Releases Video Results for Evaluation of SN100C and SAC305
EMSNow: "Nihon Superior Co. Ltd., a supplier of advanced soldering materials to the global market, has released a video demonstrating the results of an evaluation comparing the wettability and spreadability of SN100C and SAC305 solder alloys on stranded wire.
The video demonstrates that although SAC305 has a lower melting point, the superiority of SN100C's wettability and spreadability after melting results in faster total wetting and spreading over SAC305.
In general, wettability is evaluated with zero-cross time using the wetting balance test (JIS Z 3198 or IPC J-STD-003). However, it is recommended to verify the performance of wetting and spreading of solder onto a base material after melting, such as in this evaluation. The total wetting time appears to be a more realistic indication of the true wetting and spreadability of a solder than just the zero-cross time as demonstrated in the video."
The video demonstrates that although SAC305 has a lower melting point, the superiority of SN100C's wettability and spreadability after melting results in faster total wetting and spreading over SAC305.
In general, wettability is evaluated with zero-cross time using the wetting balance test (JIS Z 3198 or IPC J-STD-003). However, it is recommended to verify the performance of wetting and spreading of solder onto a base material after melting, such as in this evaluation. The total wetting time appears to be a more realistic indication of the true wetting and spreadability of a solder than just the zero-cross time as demonstrated in the video."
New Soldering Technology for Flex Circuits
EMS007: "Essemtec Switzerland introduces a new solution for soldering heat-sensitive, flexible materials such as Mylar--a selective IR oven. The principle: The specifically selected wavelength of the IR radiation is absorbed by the solder joint, but not by the foil.
Mylar films used for membrane keyboards have a limited resistance against high temperatures. Therefore, electronic components, such as LED, cannot be connected using standard SMT solders. Instead, conductive glue or low-temperature solders are used. A European keyboard manufacturer went one step further in protecting sensitive materials by inventing selective soldering with infrared radiation."
Mylar films used for membrane keyboards have a limited resistance against high temperatures. Therefore, electronic components, such as LED, cannot be connected using standard SMT solders. Instead, conductive glue or low-temperature solders are used. A European keyboard manufacturer went one step further in protecting sensitive materials by inventing selective soldering with infrared radiation."
ZnSn high temperature solders from Kawasaki
Factiva: "According to recent research from Kawasaki, Japan, 'Pb-based solders are used as high-temperature solders in power semiconductor devices. Although the use of Pb is globally restricted, alternative materials cannot replace the Pb-based solder.'
'This study proposes that the Pb-based solder can be replaced by Zn-Sn alloys. Die shear tests revealed that some Zn-Sn solder joints between Cu substrates had a higher shear strength between 300 K and 543 K than those between Fe-42Ni substrates. The microstructure of the Zn-Sn solder joints between Cu substrates showed network microstructures consisting of a Zn phase and epsilon-CuZn5 phase and direct connection between the network microstructures and intermetallic compound layer"
'This study proposes that the Pb-based solder can be replaced by Zn-Sn alloys. Die shear tests revealed that some Zn-Sn solder joints between Cu substrates had a higher shear strength between 300 K and 543 K than those between Fe-42Ni substrates. The microstructure of the Zn-Sn solder joints between Cu substrates showed network microstructures consisting of a Zn phase and epsilon-CuZn5 phase and direct connection between the network microstructures and intermetallic compound layer"
ZnSn high temperature solders from Kawasaki
Factiva: "According to recent research from Kawasaki, Japan, 'Pb-based solders are used as high-temperature solders in power semiconductor devices. Although the use of Pb is globally restricted, alternative materials cannot replace the Pb-based solder.'
'This study proposes that the Pb-based solder can be replaced by Zn-Sn alloys. Die shear tests revealed that some Zn-Sn solder joints between Cu substrates had a higher shear strength between 300 K and 543 K than those between Fe-42Ni substrates. The microstructure of the Zn-Sn solder joints between Cu substrates showed network microstructures consisting of a Zn phase and epsilon-CuZn5 phase and direct connection between the network microstructures and intermetallic compound layer"
'This study proposes that the Pb-based solder can be replaced by Zn-Sn alloys. Die shear tests revealed that some Zn-Sn solder joints between Cu substrates had a higher shear strength between 300 K and 543 K than those between Fe-42Ni substrates. The microstructure of the Zn-Sn solder joints between Cu substrates showed network microstructures consisting of a Zn phase and epsilon-CuZn5 phase and direct connection between the network microstructures and intermetallic compound layer"
Tuesday, September 7, 2010
Electronics Reliability Summit Goes Virtual
Global SMT and Packaging: "Trafalgar Publications announces that in addition to the physical conference, it will offer delegates outside of Europe the opportunity to attend the Electronics Reliability summit in Tallinn, Estonia, 21-23 September as a Virtual Delegate. Using specialized software that combines webcasting and a video display of the presenter, delegates will be able to remotely attend each presentation and join in the debate, or ask questions after each session using the chat and/or a Twitter facility."
Monday, September 6, 2010
Nihon Superior Wins ICEP Outstanding Paper Award！
Nihon Superior Co., Ltd.: "Nihon Superior is pleased to annouce that research they have sponsored at the University of Queensland, Australia, has provided the basis for the paper that earned an ICEP Outstanding Paper Award.
The Award, presented during the opening ceremony of ICEP 2010 in Sapporo on May 12, was for the paper, “Inhibiting Cracking of Interfacial Cu6Sn5 by Ni Additions to Sn-based Lead-free Solders” that was presented by the lead author, The University of Queensland's Associate Professor Kazuhiro Nogita, at ICEP 2009 in Kyoto. The paper, which reports a phenomenon that explains a major contribution to the reliability of Nihon Superior’s SN100C solder alloy was co-authored by Stuart McDonald, Hideaki Tsukamoto and Jonathan Read of University of Queensland and the president of Nihon Superior, Tetsuro Nishimura and Shoichi Suenaga of Nihon Superior."
Subscribe to:
Posts (Atom)