Global SMT & Packaging magazine: "The Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland, in collaboration with The Institute of Scientific and Industrial Research (ISIR) at Osaka University, is pleased to announce the call for participation for the Fourth International Symposium on Tin Whiskers.
Tin whiskers are needle-like growths that can form spontaneously on tin-based lead-free finished surfaces. Tin whiskers present a unique challenge to the electronics industry. Since the 1940s, there have been numerous electronics failures caused by tin whiskers. As a result of the global transition to lead-free electronics in the early 2000s, most electronic component manufacturers now use pure tin or tin-rich alloys for terminal and lead finishes. The increasing use of tin-based lead-free finishes and materials has lead to focused research on tin whiskers, particularly for long life and mission critical applications in aerospace, aviation, and medicine, i.e. implantable medical devices."
Friday, January 29, 2010
Tin Whisker Test Development-Temperature and Humidity Effects Part I: Experimental
Scopus: "The effects of temperature and humidity on tin whisker growth were investigated through a collaborative project sponsored by the International Electronics Manufacturing Initiative (iNEMI) and its member companies. A broad range of testing conditions was adopted to test a variety of components with matte tin (Sn) plating and copper (Cu)-based leadframes. The primary goal of the study was to collect data that could be used to develop mathematical models (acceleration functions) that describe the dependence of tin whisker growth and corrosion on temperature and humidity."
See also Part II
http://tinyurl.com/ygngoa7
Cu impurities in finishes cause lead-free solder voiding
Factiva: "Recently, incorporation of impurities into the electroplated Cu layer has been demonstrated to promote the voiding in Cu/solder joints. The aim of this work is to quantitatively study the role of key Cu plating parameters in the impurity incorporation process. The reported experiments emphasize the impact of plating temperature on the voiding propensity of galvanostatically deposited Cu layers. Also, a comprehensive analysis combining the findings of this study and current-voltage results for Cu deposition at constant temperature establishes a clear correlation between overpotential changes driven by plating rate or temperature and trends in the voiding propensity of accordingly deposited Cu layers.
Based on this correlation, the ranges of overpotentials where either ''void-prone'' or ''void-free'' Cu could be deposited are clearly identified in two acidic Cu plating solutions containing different additive combinations,"
IPC APEXPO Show 2010
IPC APEXPO Show 2010: "The IPC APEX EXPO technical conference is known worldwide as one of the finest and most selective in the world. Take advantage of new research and innovations from key industry players in the areas of board fabrication and design and electronics assembly.
New sessions this year include a focus on solar panel assembly, the fight against counterfeit components, embedded active components, “head-on-pillow” defects and Package-on-Package (POP) design.
That’s in addition to a strong focus on the key areas of lead-free soldering and reliability."
Thursday, January 28, 2010
Kings College work on Zn Al reactive solders
samjid.mannan@kcl.ac.uk: We are concentrating on reflow soldering with reactive elements Zn and Al. Eventually these elements will be injected into the solder in the form of nanoparticles to delay their dissolution into the solder until after wetting has occurred, but we haven't got that far yet. We have a paper we hope to publish at the Advanced Packaging Materials Conference in Cambridge in March. I attach a flier in case you might be interested
Delphi US plans for lead-free transition
Showing products to convert 2010 and beyond, including automotive etc
Effect of elements Ni and Co on morphology and type of IMC at Sn-3Ag-0.5Cu solder joi
Scopus: "The intermetallic compound (IMC) is hard and brittle, and its forming and growth at soldering joint interface is an important issue in joint reliability. The data obtained by digital optical electronic microscope indicate that the addition of element Co changes the IMC morphology from ball-like and bar-like to distinct and sharp in crest lines and edges.
The addition of elements Ni and Co in Sn-3Ag-0.5Cu solder promotes the nucleation and makes the IMC size finer. The electron probe microanalysis (EPMA) determines the chemical compositions and confirms that the IMC is changed into the (Cu, Co, Ni)6Sn5 (Cu, Co, Ni)3Sn4 mixed type from the type of Cu6Sn5 with the elements Ni and Co in the solder."
Ames Lab work on SAC+ Zn Mn Al
Factiva: "Elemental (X) additions to Sn-3.5Ag-0.95Cu (SAC3595) solder were developed with minimal (< 0.25 wt.%) concentration to avoid pro-eutectic Ag3Sn blades by reducing undercooling (Delta T) and to eliminate thermal-aging-induced embrittlement,' researchers in the United States report.
'Calorimetry and microstructure results on simple Cu/Cu joints identified 0.21Zn, 0.10Mn, and 0.05Al as sufficient to reduce undercooling below that for SAC3595 and to eliminate Ag3Sn blades. A 211A degrees C melting onset for the X = Mn alloys also suggested the discovery of a new quaternary eutectic,' wrote I.E. Anderson and colleagues, Iowa State University."
'Calorimetry and microstructure results on simple Cu/Cu joints identified 0.21Zn, 0.10Mn, and 0.05Al as sufficient to reduce undercooling below that for SAC3595 and to eliminate Ag3Sn blades. A 211A degrees C melting onset for the X = Mn alloys also suggested the discovery of a new quaternary eutectic,' wrote I.E. Anderson and colleagues, Iowa State University."
SnIn thermal fatigue solder studies
Factiva: "The thermal resistance of Si/Sn-52In/Cu sandwiched samples was measured by the laser flash method after various stages of thermal cycling. The thermal resistance was found to increase with increasing thermal cycles after 120 cycle"
H.Y. Guo, Shenyang National Laboratory Materials Science, China.
FIB analysis of SAC grain boundaries
Factiva: "To study the intragranular mechanical behavior of a Sn-Ag-Cu solder, a focused ion beam system was used to manufacture a notched microspecimen at a eutectic area within a grain. A low-speed tensile test was performed on the microspecimen using an Instron 5848 microtester at room temperature,' scientists in Oxford, the United Kingdom report.
'The results show that, besides an obvious shearing deformation, a large number of subgrains are formed in the beta-Sn matrix. Subgrain boundaries are composed of a large number of dislocations,' wrote J.C. Gong and colleagues, University of Oxford.
The researchers concluded: 'Besides the heterogeneous deformation due to the notch, Ag3Sn intermetallic compounds influence the evolution path of subgrain boundaries"
'The results show that, besides an obvious shearing deformation, a large number of subgrains are formed in the beta-Sn matrix. Subgrain boundaries are composed of a large number of dislocations,' wrote J.C. Gong and colleagues, University of Oxford.
The researchers concluded: 'Besides the heterogeneous deformation due to the notch, Ag3Sn intermetallic compounds influence the evolution path of subgrain boundaries"
Oxford University, UK
Cu and Ni effects on microstructure and crystal orientation in SAC
Factiva: "Recently, it has been reported that the crystal orientation and grain size of the beta-Sn phase in Sn-rich solders have profound effects on the reliabilities of Pb-free solder joints, such as thermo-mechanical fatigue and electromigration. Additionally, it is also known that the microstructure of the Sn-rich solders is strongly affected by their alloy composition.'
'In this study the grain size and orientation of the beta-Sn phase were investigated in terms of their alloy composition and interfacial reactions with two different under bump metallurgies (UBMs), Cu and Ni(P). Solder balls (380 mu m in diameter) of pure Sn, Sn-0.5Cu, Sn-0.5Ag, and Sn-1.8Ag (in weight percent) were reflowed on Cu and Ni(P) UBMs. After the reflow at 250A degrees C for 120 s, the microstructure of the solder joints was analyzed by cross-polarization light microscopy and electron backscatter diffraction. For the compositional analysis of solder joints, electron probe micro-analysis was used and thermodynamics calculations were also performed,' wrote S.K. Seo and colleagues."
'In this study the grain size and orientation of the beta-Sn phase were investigated in terms of their alloy composition and interfacial reactions with two different under bump metallurgies (UBMs), Cu and Ni(P). Solder balls (380 mu m in diameter) of pure Sn, Sn-0.5Cu, Sn-0.5Ag, and Sn-1.8Ag (in weight percent) were reflowed on Cu and Ni(P) UBMs. After the reflow at 250A degrees C for 120 s, the microstructure of the solder joints was analyzed by cross-polarization light microscopy and electron backscatter diffraction. For the compositional analysis of solder joints, electron probe micro-analysis was used and thermodynamics calculations were also performed,' wrote S.K. Seo and colleagues."
University of Maryland on reballing
Factiva: "For area array packages, the practice is referred to as reballing. While reballing has been used for part reclamation, very little information is available on the reliability of reballed parts.
This paper presents lead-free ball grid array (BGA) packages subjected to two ball removal and two ball reattachment techniques. Solder attach strength was used as a metric to examine the reballing process. Both the ball shear test and the cold bump pull (CBP) test were used to test solder strength. The impact of isothermal aging was also examined. The solder strength of reballed BGAs remained at the same level when different reballing methods were used and under different aging conditions. The lead-free non-reballed BGAs had higher solder strength and wider strength distribution than reballed tin-lead BGAs,' wrote L. Nie and colleagues, University of Maryland"
Effects of nano-sized Ag reinforcing particulates on the microstructure of Sn-0.
Scopus: "Composite solders were prepared by mechanically dispersing different volumes of nano-sized Ag particles into the Sn-0.7Cu eutectic solder. The effects of Ag particle addition on the microstructure of Sn-0.7Cu solder joints were investigated. Besides, the effects of isothermal aging on the microstructural evolution in the interfacial intermetallic compound (IMC) layer of the Sn-0.7Cu solder and the composite solder reinforced with 1vol% Ag particles were analyzed, respectively.
Experimental results indicate that the growth rate of the interfacial IMC layer in the Ag particles reinforced composite solder joint is much lower than that in the Sn-0.7Cu solder joint during isothermal aging. The Ag particles reinforced composite solder joint exhibits much lower layer-growth coefficient for the growth of the IMC layer than the corresponding solder joint."
Effect of Ag and Ni on the melting point and solderability of SnSbCu solder allo
Scopus: "To improve the properties of Sn10Sb8Cu solder alloy, two new solders (SnSbCuAg and SnSbCuNi) were formed by adding small amounts of Ag or Ni into the solder alloy. The results show that the melting point of the SnSbCuAg solder alloy decreases by 14.1C and the spreading area increases by 16.5% compared to the matrix solder. The melting point of the SnSbCuNi solder alloy decreases by 5.4C and the spreading area is slightly less than that of the matrix solder.
Microstructure analysis shows that adding trace Ag makes the melting point decline due to the dispersed distribution of SnAg phase with low melting point. Adding trace Ni, Cu6Sn5 and (Cu, Ni)6Sn5 with polyhedron shape on the copper substrate can be easily seen in the SnSbCuNi solder alloy, which makes the viscosity of the melting solder increase and the spreading property of the solder decline."
Effect of aging on the SnAgCuGe/Cu soldering joint shearing strength and fracture su
Scopus: "A little element Ge was added into lead-free solder Sn2.5Ag0.7Cu (0.25, 0.5, 0.75, 1.0wt%). The SnAgCuGe/Cu joint shearing strengths and IMC (intermetallic compound) thickness were measured before and after aging.
The fracture surfaces and interfaces were analyzed by scanning electron microscope and energy dispersive X-ray analysis method. The result indicates that the shearing strength of the joint reduced obviously after aging. The joint cross sections of fracture are mainly situated in solder before aging, while at both solder and interface after aging. Aging makes IMC thicker and transform to Cu3Sn from Cu6Sn5. The thickened IMC layers turn into the weakest zones of the soldering joint."
Meng, G.-G., Li, D., Li, Z.-P., Fu, Y.-H., Chen, Q.-S.
School of Material Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China
Metal stearate flux patent
WO2010000679A1: "The invention relates to solder materials, such as a solder paste (11), and contact surfaces for solder connections, wherein according to the invention a metal stearate is used as a flux, said metal stearate being applied either as a solid layer (14, 15) on the solder particles (12) or as contact surfaces (not shown) or being present as a dispersion or solution in the binder.
Advantageously, this can allow one to avoid the use of classical fluxes, in particular non-resin solder materials can be provided. This provides a simplified storage and processability of the solder materials, while at the same time producing comparatively better solder connections. The ability to use metal stearates as a flux can be achieved if the first oxide of the metals used is formed from pure metal at a lower oxygen activity (aO) than the first chromium oxide of chromium, preferably lower than the first titanium oxide of titanium, and if the metal stearate is present in a sufficient amount."
New approach for self-assembling electronics
Printed Electronics World: "When added to an oil-water mixture, the researchers found that the cubes assembled neatly along the liquid interface. Using this process the researchers were able to create a sheet of the elements that float between the oil/water boundary. The device grid is then passed through the oil/water boundary slowly, and element fixes into place neatly on the grid substrate as the solder attracts its gold contact.
Using this process at 95 degrees Celsius, the research team made a working solar cell comprising of 64,000 elements in just three minutes. The team is now research how small they can make individual elements and how large finished devices can be."
Using this process at 95 degrees Celsius, the research team made a working solar cell comprising of 64,000 elements in just three minutes. The team is now research how small they can make individual elements and how large finished devices can be."
Effect of oxide thickness on coalescence of solder powder
Factiva: "The effect of oxide thickness on the coalescence of Sn-3.5Ag-0.5Cu solder pastes is investigated by introducing a specific chemical removal process. The native oxide film is inevitably formed when solder powders are dried in vacuum at 25 degrees C after the chemical removal"
.W. Wang, Shanghai Jiao Tong University, Shanghai
MYDATA certifies AIM leaded solder paste for jet printing
EMSNow: "MYDATA is proud to announce the certification of a new leaded solder paste from leading paste supplier, AIM, for the MYDATA MY500 Jet Printer. The certification is the latest success in AIM and MYDATA's ongoing work to develop superior jet printing technologies, and follows the launch of AIM's lead-free paste for the MY500 in 2009.
'Demand for jet printing remained resilient last year, despite generally unfavorable market conditions. Our sales jumped 50 percent in 2009, and we continue to see widespread interest in our technologies,' says Robert Gothner, MYDATA Vice President Marketing and Sales.
'Two sectors that appear especially promising are the aerospace and defense industries, where leaded paste is the preferred fluid,' Gothner adds.
'Jet printing offers a vast range of design opportunities for customers. We are delighted that growing numbers of leading solder paste manufacturers are designing products for use with the MY500 Jet Printer,' says Malin Siberg, MYDATA Strategic Product Manager for Jet Printing."
'Demand for jet printing remained resilient last year, despite generally unfavorable market conditions. Our sales jumped 50 percent in 2009, and we continue to see widespread interest in our technologies,' says Robert Gothner, MYDATA Vice President Marketing and Sales.
'Two sectors that appear especially promising are the aerospace and defense industries, where leaded paste is the preferred fluid,' Gothner adds.
'Jet printing offers a vast range of design opportunities for customers. We are delighted that growing numbers of leading solder paste manufacturers are designing products for use with the MY500 Jet Printer,' says Malin Siberg, MYDATA Strategic Product Manager for Jet Printing."
SMART Group announce new process control test methods standard
EMSNow: "SMART Group announce the release of its first Standard, 'Control of Solder Paste used in Electronic Assembly Process' (Document reference: SG PCT01), that is intended to help electronics assemblers to determine the suitability of the solder paste prior to production. The tests show the actual useful life of the paste that will help to reduce waste and environmental impact.
The test methods employed are adaptations of the methods employed by paste manufacturers found in IPC-TM-650, IPC J-STD004/5 and IEC 61189-5. They assess solder paste for Slump - Spread - Wetting - Tack - Balling. Gathered data also provides the 'Open Time' that the selected paste can provide to the user.
Process Control tests have become essential to CEM's, ECM's and ODM's as they strive to enhance yields, improve product reliability and increase profits."
The test methods employed are adaptations of the methods employed by paste manufacturers found in IPC-TM-650, IPC J-STD004/5 and IEC 61189-5. They assess solder paste for Slump - Spread - Wetting - Tack - Balling. Gathered data also provides the 'Open Time' that the selected paste can provide to the user.
Process Control tests have become essential to CEM's, ECM's and ODM's as they strive to enhance yields, improve product reliability and increase profits."
Nihon Superior to highlight soldering materials at INTERNEPCON Japan 2010
EMSNow: "Nihon Superior Co. Ltd., a supplier of advanced soldering materials to the global electronics industry, announces that it will display a full range of products based on its unique lead-free solder SN100C in Booth # East 31-12 in the East 6 Hall of East Exhibit Building at the upcoming INTERNEPCON Japan 2010, scheduled to take place January 20-22, 2010 at the Tokyo Big Site.
This will include the company's completely Halogen-Free Solder Paste, SN100C P602 D4. Also, to showcase the versatility of SN100C, the company will display a range of production boards soldered with SN100C.
A highlight of this new range is the halogen-free solder paste and flux cored wire that include no halogens, fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) in their formulation, while still delivering excellent wetting on all substrates."
A highlight of this new range is the halogen-free solder paste and flux cored wire that include no halogens, fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) in their formulation, while still delivering excellent wetting on all substrates."
SMTA International Conference on Soldering and Reliability Call for Papers
EMSNow: "The SMTA Technical Committee cordially invites industry professionals to submit abstracts for the 2010 International Conference on Soldering and Reliability being held this May in Toronto, Ontario, Canada.
Abstracts are due by January 29, 2010. Following on the very successful 2005 and 2006 International Conferences on Lead-free Soldering, and the SMTA International Conference on Soldering and Reliability held in Toronto since 2007, this conference will bring together the community of soldering and reliability experts.
Suggested topics to be covered include:
SnPb with lead-free components
Reliability
Harsh Environment
Tin Whiskers
New Alloys
Electromigration
Thermal dissipation
Manufacturing Process
Package on Package
Advanced Packaging
Halogen-Free Laminates
High Density Interconnects
Thermal Interface Materials
Underfill"
Abstracts are due by January 29, 2010. Following on the very successful 2005 and 2006 International Conferences on Lead-free Soldering, and the SMTA International Conference on Soldering and Reliability held in Toronto since 2007, this conference will bring together the community of soldering and reliability experts.
Suggested topics to be covered include:
SnPb with lead-free components
Reliability
Harsh Environment
Tin Whiskers
New Alloys
Electromigration
Thermal dissipation
Manufacturing Process
Package on Package
Advanced Packaging
Halogen-Free Laminates
High Density Interconnects
Thermal Interface Materials
Underfill"
Cobar Solder Products to exhibit at Pan Pac 2010
EMSNow : "The Balver Zinn Group announces that Cobar Europe BV will exhibit a complete range of advanced soldering materials from bar solder to SMT solder paste to high-performance fluxes at the upcoming Pan Pacific Microelectronics Symposium & Tabletop Exhibition, scheduled to take place January 26-28, 2010 at the Sheraton Kauai Resort, on Kauai, Hawaii."
SMTA to sponsor Virtual PCB
EMSNow: "The Surface Mount Technology Association has been named an exclusive sponsor of Virtual PCB, the industry's only virtual trade show and conference for the PCB design, fabrication and assembly markets. Now in its third year, Virtual PCB takes place March 2 - 4, 2010.
Under the exclusive agreement, SMTA Corporate members will receive discounted rates for exhibiting. SMTA will exhibit at the show, and plans to launch a series of technical webinars in concert with the opening of Virtual PCB."
Under the exclusive agreement, SMTA Corporate members will receive discounted rates for exhibiting. SMTA will exhibit at the show, and plans to launch a series of technical webinars in concert with the opening of Virtual PCB."
New Class of Materials Could Help Streamline Process of Computer Electronic Packaging
AzoMaterials: "A Carnegie Mellon research team led by Michael McHenry, professor of materials science and engineering, biomedical engineering and physics, in collaboration with Raja Swaminathan, Intel senior packaging materials engineer, have devised an RF heating technique for solder magnetic nanoparticle (MNP) composites that can sufficiently heat solders to cause reflow without placing computer chips in conventional ovens.
A solder is a metal alloy used to bond metals together. McHenry's team includes Ph.D. materials science and engineering candidates AshFague Habib and Kelsey Miller, and Matt Ondeck, a junior in materials science and engineering.
At present, state-of-the-art techniques for making computer chips during the electronic packaging process involve use of hot air convection or the use of infrared ovens. Because heating the chips in these ovens requires significant energy costs and also poses the risk of chip warpage, McHenry's team worked collaboratively with Intel's Swaminathan to develop a tool that uses radio frequency coils to heat specially designed magnetic particles that are mixed with solder pastes.
'By varying the concentration and composition of these magnetic particles we can control the time it takes to heat them, which ultimately helps improve the speed of processing them, and potentially lowers the cost,' said McHenry, co-publication chair of the MMM/Intermag Conference."
At present, state-of-the-art techniques for making computer chips during the electronic packaging process involve use of hot air convection or the use of infrared ovens. Because heating the chips in these ovens requires significant energy costs and also poses the risk of chip warpage, McHenry's team worked collaboratively with Intel's Swaminathan to develop a tool that uses radio frequency coils to heat specially designed magnetic particles that are mixed with solder pastes.
'By varying the concentration and composition of these magnetic particles we can control the time it takes to heat them, which ultimately helps improve the speed of processing them, and potentially lowers the cost,' said McHenry, co-publication chair of the MMM/Intermag Conference."
Developing tin-lead and lead-free solder pastes
EE Publishers: "by J Bath and R Garcia, Christopher Associates, USA; N Uchida, H Takahashi, G Clark and M Itoh, Koki Solder, Japan
Over the last few years, there has been an increase in the rate of head-in-pillow component soldering defects which interrupts the merger of the BGA/CSP component solder spheres with the molten solder paste during reflow. The issue has occurred across a broad segment of industries including consumer, telecoms and military. Part I of this article was published in EngineerIT November 2009."
Over the last few years, there has been an increase in the rate of head-in-pillow component soldering defects which interrupts the merger of the BGA/CSP component solder spheres with the molten solder paste during reflow. The issue has occurred across a broad segment of industries including consumer, telecoms and military. Part I of this article was published in EngineerIT November 2009."
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Christopher Associates, a pioneering supplier to the electronics manufacturing industry, announces that Jasbir Bath, Consulting Engineer with Christopher Associates/Koki Solder, will host a SMTA-sponsored Webinar titled "Reducing Head-in-Pillow with Tin/Lead and Lead-Free Solder Paste Development." The Webinar will be held on Thursday, February 4, 2010 at 11 a.m. USA Eastern/8 a.m. USA Pacific time, and will run for approximately 60-90 minutes with a question and answer period.
Head-in-Pillow defects have been found to cause a large percentage of failures in the reflow soldering of BGA/ CSP packages, especially in fine-pitch applications. In addition to reviewing the causes and solutions for Head-in-Pillow defects, Mr. Bath will discuss contributing factors, chemistry and process optimization related to the issue.
Mr. Bath is recognized as one of the leading experts on solder paste processing, and has been working on this challenging issue with a range of industry experts.
Christopher Associates to introduce Ultrasonic Robotic Soldering Solution
EMSNow: "Christopher Associates, a supplier and distributor to the photovoltaic industry, will introduce JAPAN UNIX Co., Ltd.'s UNISONIK Ultrasonic Robotic Soldering System in booth E8 at PHOTON's upcoming 5th Photovoltaic Technology Show, the leading venue for photovoltaic manufacturing technologies in North America, scheduled to take place February 2-4, 2010 at the Moscone Center in San Francisco.
Fluxless soldering has been a goal in many industrial applications for years. For the first time in North America, Christopher Associates will introduce JAPAN UNIX Co., Ltd.'s UNISONIK Ultrasonic Robotic Soldering System, offering a complete suite of new capabilities for high-technology manufacturing. Solder on glass and heretofore difficult surfaces now can be done cost effectively and with enhanced interconnect reliability."
Fluxless soldering has been a goal in many industrial applications for years. For the first time in North America, Christopher Associates will introduce JAPAN UNIX Co., Ltd.'s UNISONIK Ultrasonic Robotic Soldering System, offering a complete suite of new capabilities for high-technology manufacturing. Solder on glass and heretofore difficult surfaces now can be done cost effectively and with enhanced interconnect reliability."
SMART Group announces upcoming lead-free event
EMSNow "The seminar is based on practical problems and in most cases solutions to effective introduction of lead-free alloys, processes and the impact on product reliability. This unique event will feature the most common problems experienced with components, printed boards, soldering alloys and process equipment along with different joint structures that result from mixed alloy assembly. It will also update engineers with the ongoing challenges and mitigation techniques for tin whiskers.
Topics to be included will be:
-- PCB delamination with high Tg laminates
-- Solder pad cratering
-- Pad lifting in manufacture
-- Nickel/gold BGA Failure Modes
-- Via hole and blind via failures
-- Silver corrosion on PCBs
-- Difference between tin/silver and tin/copper alloys
-- Conductive Anodic Filamentation (CAF) failure
Who should attend?
This event is ideally suited to design, production and quality engineers looking at lead-free for the first time, engineers with any of the problems listed or those trying to investigate failure modes. It's vital that subcontractors be up-to-date with lead-free and its possible implementation along with material and equipment requirements to advise existing and future customers."
Topics to be included will be:
-- PCB delamination with high Tg laminates
-- Solder pad cratering
-- Pad lifting in manufacture
-- Nickel/gold BGA Failure Modes
-- Via hole and blind via failures
-- Silver corrosion on PCBs
-- Difference between tin/silver and tin/copper alloys
-- Conductive Anodic Filamentation (CAF) failure
Who should attend?
This event is ideally suited to design, production and quality engineers looking at lead-free for the first time, engineers with any of the problems listed or those trying to investigate failure modes. It's vital that subcontractors be up-to-date with lead-free and its possible implementation along with material and equipment requirements to advise existing and future customers."
Pd-doped Sn-Ag-Cu-In solder material for high drop/shock reliability
Scopus: "Pd was chosen as a minor alloying element in a new Sn-1.2Ag-0.7Cu-0.4In solder alloy to improve the drop/shock reliability.
The tensile properties and drop/shock reliability of the new Sn-1.2Ag-0.7Cu-0.4In-0.03Pd solder alloy was compared with those of the Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu alloys. The UTS, yield strength and elongation of Sn-1.2Ag-0.7Cu-0.4In-0.03Pd were superior to those of the other alloys tested. Sn-1.2Ag-0.7Cu-0.4In-0.03Pd showed outstanding drop/shock reliability compared to the representative Pb-free solder, Sn-3.0Ag-0.5Cu.
Therefore, the Sn-1.2Ag-0.7Cu-0.4In-0.03Pd composition is assessed to be an alternative Pb-free solder composition that may replace Sn-3.0Ag-0.5Cu."
IPC Solder Products Value Council Issues Report on Take Action Limits for SAC Lead-Free
Facebook | IPC: "Following a two-year study on the effect of impurity limits on the performance of lead-free solder, the IPC Solder Products Value Council (SPVC) has announced the publication of a white paper, “Take Action Limits (TAL) for SAC305 Lead-Free Soldering Processes Utilizing Solder Baths/Pots.” The paper provides electronics manufacturers with better-defined limits to guide them on a more efficient use of solder and, as a result, improve yields.
Take action limits, also known as “dump pot specifications,” are important to any electronics manufacturing company using flow soldering techniques either in selective soldering or wave soldering. The report is based on testing of eight common SAC alloys that were subjected to strenuous tests, including wetting and electron microscope examination. The IPC TAL white paper identifies three action levels:
Normal operation -- the level one would expect contamination levels to be, based on running at a steady state.
Increased monitoring -- a level that is not a danger but indicates an upward trend that should be monitored more closely.
Adjust pot -- the level at which the pot should be adjusted to ensure reliable performance of solder joints."
Take action limits, also known as “dump pot specifications,” are important to any electronics manufacturing company using flow soldering techniques either in selective soldering or wave soldering. The report is based on testing of eight common SAC alloys that were subjected to strenuous tests, including wetting and electron microscope examination. The IPC TAL white paper identifies three action levels:
Normal operation -- the level one would expect contamination levels to be, based on running at a steady state.
Increased monitoring -- a level that is not a danger but indicates an upward trend that should be monitored more closely.
Adjust pot -- the level at which the pot should be adjusted to ensure reliable performance of solder joints."
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Also
http://tinyurl.com/yz6cmw6
http://tinyurl.com/ylz6r9f
Present at SMTA International 2010 - Surface Mount Technology
Surface Mount Technology: "The SMTA International Technical Committee invites participants to submit an abstract for the 2010 SMTA International (SMTAI) conference, taking place October 24 to 28 in Orlando. Short course descriptions are also being solicited.
Papers should describe significant results from experiments, emphasize new techniques, and contain technical, economic or appropriate test data. Materials should be original, unpublished and non-commercial in nature. Participants must obtain approval to present from their company before submitting an abstract.
Abstracts are due March 5, 2010. The SMTA will announce accepted papers May 20, 2010. Final manuscripts will be due to the SMTA July 16, 2010."
Papers should describe significant results from experiments, emphasize new techniques, and contain technical, economic or appropriate test data. Materials should be original, unpublished and non-commercial in nature. Participants must obtain approval to present from their company before submitting an abstract.
Abstracts are due March 5, 2010. The SMTA will announce accepted papers May 20, 2010. Final manuscripts will be due to the SMTA July 16, 2010."
Synthesis of Ag-Cu-Sn nanocrystalline alloys as intermediate temperature solder by high energy ball milling
Scopus: "To obtain intermediate temperature alloy solders with melting temperature of 400∼600C, (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys were prepared by high energy ball milling. Ag-Cu-Sn nanocrystalline alloys have been obtained after milling for 40h.
XRD results show that the (Ag-Cu28)-25Sn alloy consists of Ag4Sn and Cu 3Sn, and the (Ag-Cu28)-30Sn alloy contains Ag 4Sn, Cu3Sn and Cu6Sn5. The small polydispersed particles with size ranging from 1um to about 25μm are observed from the (Ag-Cu2s)-30Sn alloys milled for 40h by SEM. A large amount of small particles comprised of two or three grains are commonly observed by HRTEM, and average grain size is about 17.50nm. DSC results indicate that the melting points of the (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys milled for 40h are 548.5C and 539.3C, respectively"
Micro droplet behas of molten lead free solder using inkjet printing technique
Scopus: "The dynamics of droplet formation jetted by an inkjet printing system at elevated temperature were investigated experimentally in this study. The inkjet printing system with a piezoelectric printhead driven by a bipolar waveform and a nozzle orifice diameter of 50 μm was employed. Individual droplets of molten lead-free solder; Sn3.0Ag0.5Cu were inkjet printed at 230C."
Microstructure and solderability of Sn-Ag-Cu lead-free solder powder and
Scopus: "We have developed an ultrasonic atomizing equipment to have successfully prepared Sn3Ag2.8Cu lead free solder powder. The microstructure of the powders at different atomizing medium is compared with that of the conventional alloy, and a type of optimized powder is selected to compare its solderability with that of the conventional alloy.
The results reveal that the solidification rate of nitrogen atomized powder is faster than that of air atomized one. The microstructure of atomized powder with finer grain size is composed of polygonal Cu6Sn5 and granular Ag 3Sn IMC ( intermetallic compound) which are distributed dispersively in the matrix. The IMC of the powder with Cu substrate is more irregular , and the interface between diffusion layer and Cu substrate is more blurry than that of conventional alloy with Cu substrate. In addition, the creep rupture life of the atomized powder is greatly improved compared with the conventional alloy. So the comprehensive properties of the Sn3Ag2-8Cu lead free solder powder is distinctly superior to that of the conventional alloy"
Constitutive behaviour and life prediction of lead-free solder joints based on energ
Scopus: "The difference on the microstructure between lead-free solder and lead solder leads to a different constitutive behaviour, which makes their lives different. It has been found that energy model which relates to stress-strain loop, can be measured accurately.
Therefore energy models are applied to predict the life of solder joints in electronic packing. The failure of a solder can be attributed to plastic strain, elastic strain, steady-state strain and transient-creep strain. This paper systematically introduces the constitutive behaviour of lead-free solder through plastic strain, elastic strain, transient-state strain, and summarizes the energy model applied in the life prediction of lead-free solder joints"
Effect of addition of nano-copper and extrusion temperature on the microstructure and mechanical response of
Scopus: "In the present study, 0.35 and 1.1 vol.% of nano-size copper were incorporated into pure tin using hybrid microwave sintering assisted powder metallurgy route. Microwave sintered samples were extruded both at room temperature and at 230 C.
Microstructural characterization studies were conducted on the extruded samples to investigate the distribution characteristics of secondary phase, grains and pores morphology. Resistivity of solder samples was also investigated and found to be not affected by the high temperature extrusion. Room temperature tensile test results revealed that hot extruded Sn-Cu samples exhibited higher strengths and ductility when compared to room temperature extruded samples. On the contrary, the tensile properties of pure tin remained independent of extrusion temperature. An attempt is made in this study to correlate the presence of copper and effect of extrusion temperature on the microstructural evolution and mechanical response of tin."
Development of Au-Ge based candidate alloys as an alternative to high-lead content solders
Scopus: "Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The changes in microstructure and microhardness associated with the addition of low melting point metals namely In, Sb and Sn to the Au-Ge eutectic were investigated in this work. Furthermore, the effects of thermal aging on the microstructure and its corresponding microhardness of these promising candidate alloys have been extensively reported."
The findings of this work are: the addition of Sb to the Au-Ge eutectic would not only decrease its melting point but would also improve its ductility substantially and the lattice strains induced by the In atoms were the most effective strengthening mechanism.
Gold-tin-indium solder for processing compatibiity with lead-free solder
WO2010008752A2:Disclosed in this specification is a lead-free soldering alloy made of gold, tin and indium. The tin is present in a concentration of 17.5% to 20.5%, the indium is present in a concentration of 2.0% to 6.0% and the balance is gold and the alloy has a melting point between 290 0C and 340 0C and preferably between 300 0C and 340 0C. The soldering alloy is particularly useful for hermetically sealing semiconductor devices since the melting temperature is sufficiently high to permit post-seal heating and sufficiently low to allow sealing of the semiconductor without causing damage"
Semiconductor package module without a solder ball and method of manufacturing the semiconductor package module
US7652383: "A semiconductor package module having no solder balls and a method of manufacturing the semiconductor package module are provided.
The semiconductor package module includes a module board on which a plurality of semiconductor devices are able to be mounted, a semiconductor package bonded on the module board using an adhesive, being wire-bondable to the module board, and having already undergone an electrical final test, second wires electrically connecting second bond pads of the semiconductor package to bond pads of the module board; and a third sealing resin enclosing the second wires and the semiconductor package.
Because the semiconductor package module does not use solder balls, degradation of solder joint reliability (SJR) can be prevented."
Solder-jet printer aids rapid prototype production
Factiva: "A MY500 solder-jet printer is helping Thales to meet its requirements for rapid prototype production and for achieving first-time-right soldering on boards that incorporate 'difficult' components.
The printer has eliminated the need for stencils for solder-paste application and made it easier for Thales to work with unusually shaped components.
The MY500 is used to shoot solder paste into a 900um-deep cavity, to which an SMD coaxial connector is mounted."
The printer has eliminated the need for stencils for solder-paste application and made it easier for Thales to work with unusually shaped components.
The MY500 is used to shoot solder paste into a 900um-deep cavity, to which an SMD coaxial connector is mounted."
New types of lead-free solders on the base of tin and their properties
Scopus: "The aim of the work is an experimental study of binary, ternary and quaternary systems on the base of tin alloys. 22 alloys with different ratios of individual elements Ag, Cu, In, Sb, Bi, and Sn were prepared experimentally. In addition, 6 alloys of lead-free solders produced commercially (Kovohutě Přbram nstupnick, a.s.) were used and the Pb-Sn solder served as a comparative etalon.
The following characteristics were studied: temperatures and enthalpies of phase transformations (DTA, TG, DSC) of individual solders at the rates of re-heating and cooling of specimens of about 4 C min-1, microstructural analysis (optical metallography) and microhardness of specimens, chemical analysis, microanalysis of individual phases in the structure of solders (WDX, EDX), measurement of surface tension and density of solders in dependence on the temperature, test of wettability with or without use of fluxes, measurement of corrosion properties, measurement of electrical resistivity."
Drápala, J., Technical University of Ostrava Czech Republic
Inhibiting the formation of microvoids in Cu3Sn by additions of Cu to solders
Scopus: "This observation suggests that the microvoids in Cu3Sn can be effectively inhibited by maintaining a high Cu concentration in solder (e.g. > 0.58 wt.%). Rationalization for this Cu concentration effect is presented."
Lead-free Problems - US perspective
Lead free in hirel: "A large amount of information has been accumulated in the Aerospace/Defense community about lead based versus lead-free solders/solder joints. A good place to start to tap this knowledge has recently been gathered at the Defense Acquisition University web site:
https://acc.dau.mil/leadfree
I will point out the second item on the list - the Lead-free Electronics 'Manhattan Project' to compile the 'best practices' for use of lead based or lead-free solder in harsh environements. 15 leading metallurgical scientists in the US met for two weeks to compile this 350 page baseline. Since then, the same 15 met again in August to outline the required research to close the knowledge gaps between leaded and lead-free solder, particularly in harsh environments."
https://acc.dau.mil/leadfree
I will point out the second item on the list - the Lead-free Electronics 'Manhattan Project' to compile the 'best practices' for use of lead based or lead-free solder in harsh environements. 15 leading metallurgical scientists in the US met for two weeks to compile this 350 page baseline. Since then, the same 15 met again in August to outline the required research to close the knowledge gaps between leaded and lead-free solder, particularly in harsh environments."
15) The AIA and others are proposing to the US Dept of Defense a $95M project which will take three years and which will hopefully come up with solutions to the present problems with lead-free manufacturing.
IPC seeks industry votes on top ten academic posters
EMSNow: "As determined by industry, the ten academic posters with the most votes will be displayed during the exhibition at IPC APEX EXPO on April 6–8 in Las Vegas. At the show, attendees and exhibitors will be invited to vote for their favorite poster. The authors of the top three posters will be awarded with $3,000, $1,000 and $500, for first, second and third places, respectively, which will be announced at the close of the show floor reception on Wednesday, April 7.
'This is a great opportunity to acknowledge and reward industry research that is taking place at great institutions,' said Greg Munie, IPC technical conference director. 'We urge everyone to review and vote for the abstracts they feel are the best in terms of research and usefulness to our industry.'"
'This is a great opportunity to acknowledge and reward industry research that is taking place at great institutions,' said Greg Munie, IPC technical conference director. 'We urge everyone to review and vote for the abstracts they feel are the best in terms of research and usefulness to our industry.'"
Wednesday, January 27, 2010
Greenpeace electronics guide now rates lobbying
Factiva: "Greenpeace said companies should support a new version of the European Union's RoHS (Restriction of Hazardous Substances in electronics).
The update would ban brominated flame retardants (BFRs), chlorinated flame retardants (CFRs), and PVC vinyl plastic from being used in the manufacturing of electronics. The regulation already restricts how much lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB), and polybrominated diphenyl ether (PBDE) flame retardants can be used.
As far as who's the greenest, Nokia still ranks at No. 1, but Greenpeace reduced the company's overall score by one point for 'failing to do proactive lobbying' for the RoHS revisions."
The update would ban brominated flame retardants (BFRs), chlorinated flame retardants (CFRs), and PVC vinyl plastic from being used in the manufacturing of electronics. The regulation already restricts how much lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB), and polybrominated diphenyl ether (PBDE) flame retardants can be used.
As far as who's the greenest, Nokia still ranks at No. 1, but Greenpeace reduced the company's overall score by one point for 'failing to do proactive lobbying' for the RoHS revisions."
Monday, January 11, 2010
Conductive Epoxy: Pros and Cons
Circuitmart: "Another thing, getting back to the cost issue, the traditional ones that have been used successfully like in aerospace and so forth are silver and gold filled. They are much more expensive. A lot of work has been done and still remains a question of whether you can do it with copper filled. Obviously, if you can it would be a lot cheaper. But I've not heard anybody who's gotten complete confidence in using a copper filled conductive epoxy."
Video on PERM from IPC MidWest
Real Time With... IPC Midwest 2009
Denny Fritz describes the efforts of the Pb-Free Electronics Risk Management Consortium, a group formed by the aerospace and defense industries to tackle the critical issues surrounding lead-free.
Greenpeace Green Electronics League Table 2010
Greenpeace International: "We first released our 'Guide to Greener Electronics' in August 2006. The guide ranks the 18 top manufacturers of personal computers, mobile phones, TVs and games consoles according to their policies on toxic chemicals, recycling and climate change. Last updated: January 2010"
Monday, January 4, 2010
A tin pest failure
Scopus: "This case study details a tin pest failure that occurred on plated electrical connectors exposed to low temperatures during storage. Analysis indicated that the bismuth additives specified to combat tin pest were not present in sufficient quantities, and the degradation suffered by the connectors was confirmed as tin pest. New regulations (Restriction of Hazardous Substances Directive, ROHS) are limiting the use of common tin alloying elements that combat tin pest in electronic devices. The effects of this legislation with regard to tin pest are also discussed, indicating that frequency of failures from this phenomenon could increase"
IMR Test Labs, Lansing, NY, United States
Journal of Failure Analysis and Prevention
Volume 9, Issue 5, October 2009, Pages 461-465
The necessity of corrosion protection for solderable pure tin deposits on
Scopus: "Another deficiency of equal concern is the deterioration of solderability after long term storage or, as an equivalent, after steam ageing. An improvement of these defects will be achieved by applying a corrosion resistant post-treatment, which has to combine corrosion preventive properties with being able to withstand the reflow procedure, while still being present on the surface afterwards to protect the deposit from oxidation.
Whisker and solderability studies show the effectiveness of these new coatings. Solderability after heat/humidity storage can be considerably improved and even at low temperatures excellent wetting is obtained. TOF-SIMS (time-of-flight secondary ion mass spectroscopy) is being used to clearly demonstrate that these coatings will withstand multiple reflow operations. In the search for effective corrosion protection, the hydrophobicity of the final tin layer is being investigated. Furthermore this water-repellent property has to be maintained throughout prolonged contact with water. Thus a clear indicator for a compound to be suitable as a protective layer is its property to avoid discoloration during steam ageing."
Atotech Deutschland GmbH, Germany
ST Microelectronics, Italy
2009 European Microelectronics and Packaging Conference, EMPC 2009
2009, Article number 5272863
Tin whisker observations: After years of study, tin whiskers continue to fascinate, perplex and astound
Scopus: "Raytheon participated with an industry working group to evaluate the ability of different types of conformal coatings to mitigate tin whisker growth. Bright Sn-plated brass substrate coupons were selected due to their propensity to grow whiskers during one of these studies.
The study revealed one tin whisker growth theory that is whiskers sprout through weak areas in the surface oxide layer. Another observation was that there were noticeable differences in tin whiskers based on the substrate metal used. During FIB cross-sectioning, it was observed that find that after FIB trenches were cut, new tin whisker growths emerged horizontally out of the FIB trench walls near the location where the original tin whisker had sprouted vertically from the surface."
Advanced high density interconnects
Scopus : "the development of new interconnection materials and techniques is necessary to meet the ever-stringent requirements of mechanical, thermal and electrical properties of interconnection when the interconnection dimension and pitch size are reduced to very fine scales. Furthermore, such advanced interconnection materials and techniques can also be used to stack 3D IC. In this paper, the development of novel lead-free solder nanocomposites, room to low temperature Cu-Cu and Au-Au bonding, and carbon nanotube interconnection techniques will be reported. The developed micro/nanointerconnection techniques can be easily adopted by the industry to realize high density and multifunctional integration and packaging."
Effect of phosphorus element on the comprehensive properties of Sn-Cu lead-free solder
Scopus: "In the present work, the effect of phosphorus on the creep fatigue properties of Sn-Cu eutectic lead-free solder was carried out. The experimental results show that the melting temperature was almost not changed with adding small amount of P element. However, the addition of trace P element led to the decrease in the property of creep fatigue.
The fractography analysis by a scanning electron microscopy (SEM) shows that ductile fracture was the dominant failure behavior in the process of creep fatigue test of Sn0.7Cu and Sn0.7Cu0.005P specimens. It should be pointed out that there is significant difference in the fractographs between the joints of Sn0.7Cu solder and Sn0.7Cu0.005P solder. In the fractograph of Sn0.7Cu solder joint, the microstructure is prolonged along testing direction, and the dimples were more than the fractograph of Sn0.7Cu0.005P solder joint. In addition, the voids could be found on the Sn0.7Cu0.005P solder joint, and trace P addition may increase the rate of forming void of Sn0.7Cu solder joint. The voids can potentially lead to crack initiation or propagation sites in the solder joint. As a result, the creep fatigue of solder joint containing P such as Sn0.7Cu0.005P offers worse property compared to Sn0.7Cu solder joint"
Beijing University of Technology, China
Journal of Alloys and Compounds
Bulk metallic glass solder material - Intel Patent
US7628871: "High strength, reliable bulk metallic glass (BMG) solder materials formed from alloys possessing deep eutectics with asymmetric liquidous slopes. BMG solder materials are stronger and have a higher elastic modulus than, and therefore are less likely than crystalline solder materials to damage fragile low k interlayer dielectric (ILD) materials due to thermal stress in materials with different coefficients of thermal expansion (CTE). BMG solder materials may physically, electrically, or thermally couple a feature to another feature, or any combination thereof. For example, in an embodiment of the invention, a BMG solder material may physically and electrically couple an electronic component to a printed circuit board."
6 Advantages to Using the Resistance Soldering Process
DoItYourself.com: "Resistance soldering is more precise and controllable than using a soldering iron. The unit plugs into a wall socket, and the power passes through a step-down transformer. This allows complete control of the power level. Instead of heating a steel-clad copper tip, power passes through a material that resists electricity, converting it into heat. A foot switch makes it easy to turn power on and off exactly when it is needed, and leaves your hands free to work with the solder and hand piece. This technology is becoming more and more common for many uses."
Defence Acquisition University Databank on US Military Lead-Free
[ACC]: "Conversion of the commercial supply chain to Lead-free solders and finishes is being executed. The Lead-free transition will affect the Military if not properly addressed.Managers of DoD programs must be aware of the risks associated with use of Lead-free technology to control/manage the situation. Identifying the risks, and subsequent Risk Management Plans, is facilitated by use of the references below, as well as a Lead-Free Control Plan.Acceptance of this situation and a subsequent proactive approach to control and manage risk will result in the continued safe and reliable operation of Military electronics"
Universal Instruments’ APL Hosts AREA Consortium Meeting
Universal Instruments: "Universal Instruments’ Advanced Process Lab hosted the third 2009 Advanced Research in Electronics Assembly (AREA) Consortium meeting at the Treadway Inn in Owego, NY on October 28-29. More than 75 attendees from the 29 member companies participated in the two-day event and a much larger number has signed up for subsequent webcasts of the presentations. Topics ranged from lead-free solder microstructure and reliability to environmental stress screening procedures."
November 4, 2009 - Attending companies included industry leaders such as Alcatel-Lucent, Asymtek, BAE, Boston Scientific, Brocade, Celestica, Curtiss Wright, Dell, Ericsson, Harris, IBM, Indium, Lord Corporation, MIT Lincoln Labs, Motorola, Multek, Northrop Grumman, Plexus, Qualcomm, Rockwell Automation, Sun, Texas Instruments, and Textron.
The agenda format was consistent with previous meetings, featuring concise presentations with the opportunity for detailed follow-up discussions in a final poster session. The Wednesday session opened the event with a review of systematic results of thermal cycling of lead-free soldered assemblies and then progressed to a neural network analysis of this and previous thermal cycling data. This information revealed a systematic trend of considerable importance for assessment of acceleration factors to life in service. Other Wednesday morning topics included pad cratering research and new thermal interface materials (TIMs). Previous pad cratering research has led to protocols for choosing the most reliable among the many new printed circuit board materials.
The afternoon session on the opening day featured presentations on the reliability testing of various TIMs, as well as a discussion on new insights into lead-free metallurgy. Also examined was the evolution of lead-free solder microstructure. "The so-called Manhattan Project, headed by a team of deep subject matter experts from the military and aerospace community, has identified our current inability to account for the effects of long-term aging and combinations of different loads on lead-free solder reliability as particularly critical,” stated George Westby, Director of Universal’s Advanced Process Lab. “These issues and their consequences have therefore been the focus of in-depth research efforts in recent months, and we were delighted to see technical leaders from across the industry travel to our meeting to learn and discuss our results," continued Westby. Further analysis of these results will improve the ability to measure and predict reliability and make our military and aerospace vehicles safer.
Low-Ag SAC alloys and the minimization of reflow temperatures were other topics rounding out the day-one session.
Day two of the event kicked off with updates on edge and corner bonding, a topic of ongoing interest to many, and efforts to define a practical, safe screening test for the identification of inferior electrolytic Ni, i.e. Ni/Au coatings that may give 'missing balls' and/or brittle failure of the inter-metallic bond right after reflow. Current screening tests are now suspected of doing more damage than previously thought, presenting a safety issue. Other day two topics included flux dipping of flip chips, reballing, ENEPIG coatings, and an overview of all past consortium reports and how to effectively use them for reference. The event was concluded with the poster session, including in-depth discussions of the major projects with the researchers, as well as networking opportunities.
Effect of 0.05% Cr on intermetallic compound layer growth for Sn-Ag-Cu lead-free solder joint during isothermal aging
Scopus: "The growth behaviors of interfacial intermetallic compound for the solder joints of Sn-3.0Ag-0.5Cu/Cu substrate and Sn-3.0Ag-0.3Cu-0.05Cr/Cu substrate during isothermal aging at 150' for 0, 24, 168, 500 and 1000 h respectively have been investigated.
The results showed that the intermetallic compound layer at the Sn-3.0Ag-O.3Cu-0.05Cr/Cu joint is much thinner than that at the Sn-3.0Ag-0.5Cu/Cu joint after isothermal aging for the same temperature and time. After aging for 1000 h, the average thickness of intermetallic compound layer of Sn-3.0Ag-0.3Cu-O.05Cr/Cu solder joint is only about 5.13 μm, which is far less than that ofSn-3.0Ag-0.5Cu/Cu joint at 11.33 μm. The diffusion coefficients of intermetallic compound layer of Sn-3.0Ag-0.3Cu-0.05Cr/Cu and Sn-3.0Ag-0.5Cu/Cu joints are 3.90 10-1818 m2s -1and16 10-17m2s-1 respectively. The longer the aging time, the more obvious is the effect of Cr inhibiting the overgrowth of intermetallic compound layer of Cu/Solder/Cu joint"
Assessment of lead-free solder pastes with different type of powder for fine-pitch application
Scopu: "The pastes with particle size type 3, 4 and 5 easy of attainment on the market were chosen to investigate. The rheological and technological properties of those pastes were investigated.
There were made: wetting test, viscosity test, slump test, copper corrosion test and reflow process tests. All of the investigated solder pastes pass the slump test. However, results of wetting test show that solder paste with powder particle size type 4 and 5 is more adequate for fine- pitch assembly.
But it should be notices that the solder pastes type 5 are more prone to oxidation and are more expensive."
The effects of solder volume and Cu concentration on the consumption rate of Cu pad during reflow soldering
Scopus: "The combined effect of solder volume and Cu concentration in solder on the Cu consumption rate is of significant practical importance but has never been satisfactorily addressed in literature so far.
In this study, lead-free solder balls of different volumes (400, 500, 760 and 960 μm in diameter) and different Cu concentrations (Sn3AgxCu with x = 0, 0.3, 0.5, and 0.7 wt.%) were reflowed over Cu soldering pads in order to resolve this issue. The data obtained afforded the establishment of an empirical equation that could predict the Cu consumption during reflow. Such consumption rate information is crucial for designing the Cu conduction traces with minimum but reliable dimensions. Both the solder volume and the Cu concentration had marked effects on the morphology of the reaction product. Rationalizations for the effects on the consumption rate and the morphology are presented."
National Taiwan University, Taiwan
Journal of Alloys and Compounds
Effects of novel carboxylic acid-based reductants on the wetting characteristics of anisotropic conductive adhe
Scopus: "Three different types of carboxyl acid-based reductants were added to remove the oxide layer on the surfaces of the filler particles and the conductive pad. Good wetting properties were achieved between the LMPA filler and the Cu pad in the epoxy resin using these carboxylic acid-based reductants."
Low-Temperature Sintering of Nanoscale Silver Paste for Attaching Large-Area (100
Scopus: "A low-temperature sintering technique enabled by a nanoscale silver paste has been developed for attaching large-area (>100 mm2) semiconductor chips.
This development addresses the need of power device or module manufacturers who face the challenge of replacing lead-based or lead-free solders for high-temperature applications. The solder-reflow technique for attaching large chips in power electronics poses serious concern on reliability at higher junction temperatures above 125 'C. Unlike the soldering process that relies on melting and solidification of solder alloys, the low-temperature sintering technique forms the joints by solid-state atomic diffusion at processing temperatures below 275 'C, with the sintered joints having the melting temperature of silver at 961 'C. Recently, we showed that a nanoscale silver paste could be used to bond small chips at temperatures similar to soldering temperatures without any externally applied pressure. In this paper, we extend the use of the nanomaterial to attach large chips by introducing a low pressure up to 5 MPa during the densification stage"
SnCuNi solder alloy drop testing: Is it a "drop-in" replacement for SAC 105 and SAC 305?
Scopus: "A study was performed to evaluate the reliability of SnCuNi (SCN) drop testing based electrical interconnects.
The test board used for drop testing was of a modified Jedec design. It was a 1 mm thick, two- layer FR-4 construction, using a Cu OSP surface finish. The board dimensions were 132 77 mm. The pads were non-solder mask defined with a nominal diameter of 0.0145''. Amkor CABGA 208 components, using an ENIG surface finish, were supplied without solder balls. To these, 0.020 diameter solder balls of SAC 305, SAC 105 and SCN were attached in-house using a tacky flux. A total of 16 drop test boards were assembled. SAC 305 and SAC 105 components were assembled with SAC 305 paste, while SCN components were assembled with SCN paste. Each component was connected to an event detector to monitor for electrical failure during the testing. Failure analysis was conducted through the use of dye penetration and cross-sectional analysis.
SCN alloy appears to be well suited for use in surface mount applications with minimal adjustments to he assembly process."
Universal Instruments Corp
Circuits Assembly Volume 20, Issue 11, November 2009, Page 36
Microstructures and mechanical properties of Sn-30Bi-0.5Cu low-temperature
Scopus: "A new type of low-temperature solder, Sn-30Bi-0.5Cu was fabricated by adding Cu elements into the tin-bismuth series solder. The microstructures and mechanical properties of the solder were studied.
The results show that the addition of Cu elements can restrain the segregation of bismuth in the interface between solder and Cu pad, prevent the bismuth from forming into bulky crystal as strips, and in-situ form Cu-Sn intermetallic compounds(IMCs) in tin-bismuth solder. When the mass fraction of Cu is about 0.5%, both of the tensile strength and elongation reach to the best values, and the vibration reliability increases. The reason is that the addition of Cu element can improve the microstructures of the Sn-Bi-Cu solder by forming appropriate rod-like shape fine IMC crack pinning and strengthening β-Sn soft matrix, thus strengthening its soldering and vibration mechanical properties which are close to those of Sn-Bi-Ag solder and far more than those of the Sn-Bi eutectic solders. Two types of fracture occur. During the tension tests the fracture surface type of the Sn-30Bi-0.5Cu solder is a mixed fracture surface of plastic and brittle."
Microstructures and mechanical properties of Sn-30Bi-0.5Cu low-temperature
Scopus: "A new type of low-temperature solder, Sn-30Bi-0.5Cu was fabricated by adding Cu elements into the tin-bismuth series solder. The microstructures and mechanical properties of the solder were studied. The results show that the addition of Cu elements can restrain the segregation of bismuth in the interface between solder and Cu pad, prevent the bismuth from forming into bulky crystal as strips, and in-situ form Cu-Sn intermetallic compounds(IMCs) in tin-bismuth solder. When the mass fraction of Cu is about 0.5%, both of the tensile strength and elongation reach to the best values, and the vibration reliability increases. The reason is that the addition of Cu element can improve the microstructures of the Sn-Bi-Cu solder by forming appropriate rod-like shape fine IMC crack pinning and strengthening β-Sn soft matrix, thus strengthening its soldering and vibration mechanical properties which are close to those of Sn-Bi-Ag solder and far more than those of the Sn-Bi eutectic solders. Two types of fracture occur. During the tension tests the fracture surface type of the Sn-30Bi-0.5Cu solder is a mixed fracture surface of plastic and brittle."
Influence of indium addition on characteristics of Sn-0.3Ag-0.7Cu solder alloy
Scopus: "Effects of indium (In) addition on solidus and liquidus temperatures, wetting time, wetting force, tensile strength, and microhardness of Sn-0.3Ag-0.7Cu lead-free solder alloy were investigated in this paper.
Indium was added and varied from 0 to 3 wt%. It is found that solidus and liquidus temperatures of the solder alloy are lowered as the In content is increased. However, In also increases the melting range between solidus and liquidus temperatures. Wetting time of the solder alloy is reduced by the addition of In while the wetting force is increased with the increase of In content. With the addition of In, the Sn-rich phase is smaller in size, and the intermetallic compounds are more uniformly distributed. As a result, tensile strength and microhardness of Sn-0.3Ag-0.7Cu are increased when In is added into the solder alloy."
King Mongkut's Institute of Technology Ladkrabang,, Thailand
Tokai University, Japan
Journal of Alloys and Compounds
Volume 485, Issue 1-2, 19 October 2009, Pages 225-230
Solderless assembly of electronic products - A more reliable and more cost effect
Scopus: "The new process reverses the traditional approach to electronic assembly by placing components first and then making the electrical and interconnections using traditional printed circuit board (PCB) manufacturing processes, The result is a process with compelling benefits and one which it is believed will not only be more environmentally friendly than lead-free but one which will result in more reliable electronic products and a higher yielding and at lower overall cost. This paper will show how simple modifications to design and manufacturing processes used for electronics and employment of new and alternative co-designed and integrated manufacturing methods without solder could potentially deliver significant untapped potential from future electronics assemblies with little impact on the manufacturing infrastructure."
Verdant Electronics, Jo Fjelstad
5th IEEE Vehicle Power and Propulsion Conference, VPPC '09 2009, Article number 5289876, Pages 11-16
A new technology for recycling materials from waste printed circuit boards
Scopus: "Waste printed circuit boards (WPCBs) contain lots of valuable resources together with plenty of hazardous materials, which are considered both an attractive secondary resource and an environmental contaminant. In this research, a new process of 'centrifugal separation vacuum pyrolysis' for the combined recovery of solder and organic materials from WPCBs was investigated. The results of centrifugal separation indicated that the separation of solder from WPCBs was complete when WPCBs were heated at 240 'C, and the rotating drum was rotated at 1400 rpm for 6 min intermittently"
Central South University, Changsha, China
Investigation on Sn grain number and crystal orientation in the Sn-Ag-Cu/Cu solder jo
Scopus: "Polarized light microscopy and electron backscatter diffraction have been used to quantify the number of β-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. The Sn-Ag-Cu solder joints of different sizes were found to contain only several β-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 β-Sn grains tended to be at a small angle with solder pads. Specific orientation relationships were observed to be prevalent between neighboring β-Sn grains. The grain number, crystal orientation and misorientation were independent of solder joint size"
Inkjet solder printing
Factiva: "An experimental investigation on the droplet formation of molten Sn3.0 wt%Ag0.5 wt%Cu alloy by an inkjet printing process was conducted. The printing process used a piezoelectric print head with a nozzle orifice diameter of 50 mu m. Micro-droplets of a molten lead-free solder were ejected at 230 degrees C. The print head was driven by a bipolar pulse 40 V in amplitude,' scientists in Tainan, Taiwan report."
W.S. Hwang, National Cheng Kung University, Taiwan
Journal of Micromechanics and Microengineering, 2009;19(12):25021
Underwriters Laboratories Announces Alternative Certification Program for Lead Free Verification of Cooking and Plumbing Products
Factiva: "Underwriters Laboratories (UL), a global leader in drinking water quality and safety, announced a new certification program to help manufacturers of cooking and plumbing related products demonstrate compliance with new, stricter low lead requirements that will be mandatory in California and Vermont starting Jan. 1, 2010."
alifornia Assembly Bill 1953 (AB 1953), now a state law, was passed in order to update section 116875 of the California Health & Safety Code. The law requires no more than 0.2 percent lead by weight in solder and flux used in the installation or repair of any public water system or any residential or nonresidential facility that provides water for human consumption. AB 1953 also requires no more than a weighted average of 0.25 percent lead by weight when used with respect to the wetted surfaces of pipes and pipe fittings, plumbing fittings and fixtures.
UL's new certification program will test materials to demonstrate compliance to both the California Health and Safety Code and similar legislation in Vermont. It will allow manufacturers that are required to demonstrate compliance with the California Health and Safety Code, but are not covered by or specifically included in Annex G of ANSI/NSF 61, to obtain the proper product safety certification.
"UL is giving manufacturers their first option of demonstrating compliance with new low lead laws using a means other than Annex G. We decided not to wait for Annex G to be updated or the creation of a new standard to offer our valued customers California Department of Toxic Substances Control (DTSC)-recognized product validation," said Jeff Smith, general manager, UL Global Water Business. "Now, manufacturers can quickly and efficiently navigate the compliance processes recognized by the DTSC and required by state law."
SnCu dissolves immersion Ag and fails after ageing
Factiva: "In this study, the interfacial reaction and joint reliability of immersion Ag-plated Cu substrate with the Sn-0.7Cu (wt-%) ball-grid array (BGA) solder was investigated. During reflow, the Ag plating layer was dissolved completely into the molten Sn-Cu solder and some of the Cu layer was also dissolved into the molten solder.'
'The dissolved Ag and Cu were precipitated as Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) in the solder matrix. Upon reflow, the Sn-Cu solder exhibits an off-eutectic reaction to produce the eutectic phase and precipitate (Cu6Sn5 and Ag3Sn). The Cu-Sn IMC layer was formed at the solder/Cu interface after reflow, and the IMC layer grew during aging treatment. During the shear tests, the failure mode switched from a bulk-related failure to an interface-related failure. After aging for 250 h, the joint failed partially at the solder/Cu6Sn5 interface,' wrote J.W. Yoon and colleagues.
The researchers concluded: 'The brittle fracture was linked to the formation of thick Cu-Sn IMC layer.'"
'The dissolved Ag and Cu were precipitated as Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) in the solder matrix. Upon reflow, the Sn-Cu solder exhibits an off-eutectic reaction to produce the eutectic phase and precipitate (Cu6Sn5 and Ag3Sn). The Cu-Sn IMC layer was formed at the solder/Cu interface after reflow, and the IMC layer grew during aging treatment. During the shear tests, the failure mode switched from a bulk-related failure to an interface-related failure. After aging for 250 h, the joint failed partially at the solder/Cu6Sn5 interface,' wrote J.W. Yoon and colleagues.
The researchers concluded: 'The brittle fracture was linked to the formation of thick Cu-Sn IMC layer.'"
Sungkyunkwan University, South Korea
Materials Science and Technology, 2009;25(12):1478-1484
Mixed soldering SAC, SnZnAl
Factiva: "With the development and use of a variety of Pb free solders, it is probable that some solder joints in electronic assemblies may be made with solders of two different compositions. To investigate possible microstructures resulting from such procedure, samples were prepared using small balls of four different Sn-Ag-Cu (SAC) Pb free solders, as well as Sn-Zn-Al solder, melted together with eutectic Pb-Sn solder paste and also various SAC solder pastes, on a copper substrate,' investigators in Toronto, Canada report.
'It was observed that using eutectic Pb-Sn solder paste with an SAC solder ball introduced some Pb-Sn eutectic microstructure and changed the ternary eutectic present from Ag3Sn-Cu6Sn5-Sn to Ag3Sn-Pb-Sn. Use of an SAC solder paste with Sn-Zn-Al solder introduced an apparent Ag-Cu- Zn ternary compound, replacing Zn lamellae of the Sn-Zn eutectic. With eutectic Pb-Sn solder paste, the Pb-Sn-Zn ternary eutectic was formed,' wrote L. Snugovsky and colleagues, University of Toronto.
The researchers concluded: 'It was noted that use of a high Sn solder results in rapid dissolution of the copper substrate.'"
'It was observed that using eutectic Pb-Sn solder paste with an SAC solder ball introduced some Pb-Sn eutectic microstructure and changed the ternary eutectic present from Ag3Sn-Cu6Sn5-Sn to Ag3Sn-Pb-Sn. Use of an SAC solder paste with Sn-Zn-Al solder introduced an apparent Ag-Cu- Zn ternary compound, replacing Zn lamellae of the Sn-Zn eutectic. With eutectic Pb-Sn solder paste, the Pb-Sn-Zn ternary eutectic was formed,' wrote L. Snugovsky and colleagues, University of Toronto.
The researchers concluded: 'It was noted that use of a high Sn solder results in rapid dissolution of the copper substrate.'"
Microelectronic package having solder-filled through-vias
US7638867: "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."
Intel, December 2009
Lead-free hand-soldering - ending the nightmares
EMSNow: "Most issues during the transition seem to be with Hand-soldering
As companies transition over to lead-free assembly a certain amount of hand-soldering will always be there. An article from Tech Search International last year did say that in Asia where lead-free is highly used, hand-soldering was more of a problem than lead-free SMT or wave soldering.
Kester has been getting numerous calls in reference to hand-soldering with lead-free in recent months. In fact most problem calls and requests for training through Kester University are related to lead-free hand-soldering and rework. In many cases the assemblers are using materials from various solder suppliers with similar issues occurring in all cases. Often the problems are more than material issues."
As companies transition over to lead-free assembly a certain amount of hand-soldering will always be there. An article from Tech Search International last year did say that in Asia where lead-free is highly used, hand-soldering was more of a problem than lead-free SMT or wave soldering.
Kester has been getting numerous calls in reference to hand-soldering with lead-free in recent months. In fact most problem calls and requests for training through Kester University are related to lead-free hand-soldering and rework. In many cases the assemblers are using materials from various solder suppliers with similar issues occurring in all cases. Often the problems are more than material issues."
IMC of SAC0307-xNi/Ni soldered joint and consumption of Ni coating
Scopus: "The microstructure of interfacial IMC and the consumption of Ni layer for SAC0307/Ni (Sn-0.3Ag-0.7Cu/Ni) soldered joint and SAC0307-0.05Ni/Ni (Sn-0.3Ag-0.7Cu-0.05Ni/Ni) soldered joint after aging at 180 'C were studied by scanning electron microscope( SEM).
The results indicated that the IMC layer of SAC0307/Ni and SAC0307-0.05Ni/Ni are both (Cu1-xNix)6Sn5 after reflow soldering. With the increasing of aging time, the thickness of IMC layer increases gradually, the type of IMC is not changed, but the chemical composition changes. The morphology of IMC is storm-shaped and the thickness of IMC is much thinner when SAC0307 solder added 0.05% Ni is used. The consumption of Ni layer is nearly the same using both solders after the first time reflow soldering, but the residual thickness of the Ni layer in SAC0307/Ni solder is thinner than that in SAC0307-0.05Ni/Ni after aging for 384 h.
So solders with a little Ni element can decrease the consumption rate of Ni layer effectively during aging, that is, the aging-resistant ability of Ni pad is improved obviously."
Harbin University, China
Hanjie Xuebao/Transactions of the China Welding Institution
Volume 30, Issue 11, November 2009, Pages 53-56
Rare Earths strategic supplies more important than price
Mineweb : "'Price may not be as important as security of supply [for Rare Earth metals]' says Jack Lifton, an independent consultant with more than 45 years of experience in sourcing nonferrous strategic metals. In the U.S., our dependence on rare metals is undermined by the simple fact that we're not producing any. Given that China now controls 95% of these 'technology metals' and the world is projected to eat 200,000 tons of rare earth metals near 2015, we need to jumpstart our own domestic supply chain and, more importantly, build the refineries to process them-rather than sending them to China for refining, which is our only option currently."
Au solders for medical applications
Factiva: "According to recent research from Aachen, Germany, 'Research has been carried out to investigate new soldering materials and technologies for the medical field. The two soldering techniques, which have been considered, are diffusion and active soldering.'
'In order to satisfy the most important medical requirement, the biocompatibility, gold based solders and soldering systems have been studied. According to the Directive 2002/95/EC of the European Parliament, lead as well as cadmium, hexavalent chromium and mercury have not been alloyed in the developed solders. The examined soldering systems enable joining similar and dissimilar materials, which is essential in the field of hybrid microsystems engineering,' wrote K. Bobzin and colleagues.
The researchers concluded: 'Furthermore, the achieved low process temperatures reduce the incidence of damage and thermally induced stresses in the components being joined.'
Bobzin and colleagues published their study in Materials Science and Technology (Challenging gold based filler metals for uses in medicine. Materials Science and Technology, 2009;25(12):1422-1431).
For additional information, contact S. Ferrara, Institute Oberflaechentech, Dept. of Brazing & Soldering Technology, 1 Juelicher Str 344A, Aachen, Germany."
'In order to satisfy the most important medical requirement, the biocompatibility, gold based solders and soldering systems have been studied. According to the Directive 2002/95/EC of the European Parliament, lead as well as cadmium, hexavalent chromium and mercury have not been alloyed in the developed solders. The examined soldering systems enable joining similar and dissimilar materials, which is essential in the field of hybrid microsystems engineering,' wrote K. Bobzin and colleagues.
The researchers concluded: 'Furthermore, the achieved low process temperatures reduce the incidence of damage and thermally induced stresses in the components being joined.'
Bobzin and colleagues published their study in Materials Science and Technology (Challenging gold based filler metals for uses in medicine. Materials Science and Technology, 2009;25(12):1422-1431).
For additional information, contact S. Ferrara, Institute Oberflaechentech, Dept. of Brazing & Soldering Technology, 1 Juelicher Str 344A, Aachen, Germany."
iNEMI members release definition of "Low Halogen" for electronic products
EMSNow: "The International Electronics Manufacturing Initiative (iNEMI), an industry-led consortium, released a position statement that defines 'low-halogen'(BFR/CFR/PVC*-free) for electronic products. iNEMI members supporting the statement include: Cisco, Dell Inc., Doosan Corporation, HP, Intel Corporation, Lenovo, Nan Ya Plastics Corporation, Senju Comtek Corp., Sun Microsystems Inc. and Tyco Electronics Ltd."
For PCBs and substrate laminates, iNEMI members define "low halogen" as containing no more than 1500 ppm of total halogens in the resin plus reinforcement matrix, and no more than 900 ppm (each) of bromine or chlorine (per IPC-4101). For components, each plastic in the component should contain less than 1000 ppm of bromine if the source is from brominated flame retardants (BFRs), and less than 1000 ppm of chlorine if the source is from chlorinated flame retardants (CFRs), PVC or PVC copolymers.
"Dell and the other companies supporting the iNEMI position feel that it is important to have a common definition of 'low-halogen' electronics to enable industry initiatives and supply chain conversion to 'low-halogen' products," said Scott O'Connell, environmental strategist for Dell, chair of iNEMI's Environmentally Conscious Electronics Technology Integration Group and co-chair of IPC's Low-Halogen Electronics Standard Task Group
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