Nanotech project in solders and coatings

LinkedIn discussion

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"

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."

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."

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.

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."

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.

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."

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."

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..."

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.

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"

Alpha's Alan Plant to Present at Tallin Reliability Summit

Global SMT and Packaging: "Alpha’s Regional Applications Manager Europe, Alan Plant is to present at the European Electronics Assembly Reliability Summit, September 21-23, 2010 in Tallinn, Estonia.

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."

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"

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"

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."

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"

New RoHS Exemptions Amendment published

Official Journal 24th September

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.

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."

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."

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."

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."