P. Kay Solder Surfactant

Global SMT & Packaging magazin: "P. Kay Metal will introduce patented MS2™ (Molten Solder Surfactant) in booth 1K40. By eliminating dross, MS2™ allows manufacturers to reduce solder usage by as much as 70 percent, depending on production volume, resulting in significant cost savings. MS2™ does not mix with the metal but forms a thin floating layer that covers areas of the solder surface excluding the wave, which is not disturbed during the process. MS2™ continues removing metal oxides as solder is pumped through the system, cleansing and purifying the bath. The result is lower surface tension."

South China Market Data 2009

Global SMT & Packaging magazin: "As China’s electronics manufacturing industry looks to sustain this growth, South China- one of the fastest-growing areas for the global electronics manufacturing industry- is home to the largest manufacturing base in the country."

The electronic information industry and automobile manufacturing industries in South China are much more advanced than in other regions of the country. South China accounts for 37 percent of the country’s manufacturing output in these sectors. In manufacturing sectors such as the mobile phone, laptop, household appliance, communication equipment and digital camera sectors, a change in production output will have a direct impact on the information industry throughout China. The production value of the electronic information industry in Guangdong, for example, has been the highest in China for 17 consecutive years. Dongguan, one of the province’s most productive cities, is now globally recognized for producing electronic goods. Shenzhen is renowned for producing mobile phones - in each of the last two years over 100 million phones have been produced. Recently, the sales of household appliances in the Zhujiang River Delta region have exceeded USD 12 billion. This amounts to more than 30 percent of the total sales of household appliances in China. Various industry projections report that by 2010, the Guangzhou automobile industry will be valued at USD 350 billion. The number of cars produced annually is expected to hit 1.6 million and the production value is anticipated to be USD 250 billion. In mechanics manufacturing, the need for mechanical tools in South China is growing at a rate of 20 percent a year.

Effect of Solder Thickness on Electromigration Behavior in Eutectic SnPb Solder Reaction Co

Scopus: "The trend of miniaturization of electronic products induced the shrinking dimension of interconnects in the chip. When those interconnects are subjected to high current density (usually 103 to 104 A/cm2), electromigration (EM) could affect the reliability of the chip which would ultimately break the circuit.

In this study, eutectic SnPb solders with thickness of 280, 128, and 50μm were investigated under high current density (104A/cm2) and high ambient temperature (120C). The EM-induced surface undulations were more prominent at the shorter thickness, demonstrating that the diffusion of metal atoms/ions was controlled by the actual temperature in the bulk solder instead of the back stress."

Mechanisms for Sn whisker growth in rare earth-containing Pb-free solders

Scopu: "It has recently been documented that Pb-free solder alloys doped with trace amounts of rare earth (RE) elements show a very strong propensity to grow Sn whiskers. In this work, we have investigated the effect of the addition of 2 wt.% Ce, La or Y on the whiskering behavior of Sn-3.9Ag-0.7Cu.

Hillock-type whiskers around particle peripheries were observed in water-quenched alloys with smaller RESn3 particles, while furnace-cooled alloys with larger RESn3 particles formed needle-like whiskers from within the particle. Phase separation between Sn and RE oxides occurred during oxidation of the RESn3 intermetallics. A focused ion beam serial sectioning approach was used to visualize the Sn whiskers and the oxide structure.

We show that the driving force for whisker growth is related to the compressive stresses that develop in these particles during the oxidation of the RE intermetallic phases"

Liquid Phase Sintered Solders with Indium as Minority Phase for Next Generation Thermal Interface Material A

Scopuss: "Because of their high thermal conductivity (K), low melting point (Tm), and low shear strength, indium-based materials are excellent candidates for thermal interface material (TIM) applications."

Here, a radically different approach for producing microelectronic solder TIMs based on liquid phase sintering (LPS) is presented, which not only addresses the above problems, but also paves the way for the development of solder TIMs with even higher K than that of In for next generation packages. LPS Sn-In solders, the microstructure of which consists of particles of the high melting phase (HMP) Sn and a smaller amount of intergranular low melting phase (LMP) In, were processed and characterized.

Electronics market forecasts

BPA Consulting: Looking at the sectoral demand, i.e. the demand for finished PCBs by industry sector, BPA believes that by 2012 the worldwide market will have returned to levels similar to that experienced in 2007. In other words, approximately US$ 49.3 billion. Communications and Telecoms equipment will account for 30.7% of this total; Business, Retail and Computer equipment will have the largest share at 31.7% with the third largest being consumer electronics equipement at 18%. For 2009 BPA forecasts PCB production to be just over US$39 billion compared to 2007's US$49 billion.

Looking at the consequent demand for laminate, there will be a need for 485 million square meters with the consumer sector accounting for nearly 30% of the total industry demand, Business, Retail and Computer equipment next with 27.9% and Communications and Telecoms equipement just behind with 25.5%.

Nanoscale Silver Paste and Its Low-temperature Sintering for Chip Attachment

IMAPS - Abstract Preview: "However, a serious drawback of the sintering technology is the requirement of high quasi-static pressure (40 MPa) to lower the sintering temperature of conventional thick-film silver pastes. The need of large pressure limits manufacturing throughput and places critical demands on substrate flatness and chip thickness.

In this paper, we describe development of a nanoscale silver paste, consisting of nanoparticles of silver, to lower the silver sintering temperature below 275oC without any applied pressure. The paste was extensively tested in attaching small- and large-area power semiconductor and optoelectronics chips. The sintered joints were found to have excellent electrical, thermal, mechanical, and thermo-mechanical properties, which make the nanoscale silver paste an intelligent use of the precious metal to speed up implementation of the silver sintering technology."

Au-Ge Based Candidate Alloys for High-Temperature Lead-Free Solder Alternatives

IMAPS - Abstract Preview: "The selection of high-temperature solders is a challenge since a survey of the phase diagram reveals that there is no drop-in replacement. Zn-Al based alloys are being proposed as the cost-effective replacement. However, zinc is corrosive and aluminium possesses a high natural radius of curvature. Bismuth based alloys are also being considered but they have drawbacks such as low electric/thermal conductivity and brittleness.

Au- (Ge, Si & Sn) based candidate alloys too are being proposed. Among them, Au-Si based alloys possess wetting constraints. Au-Sn based alloys consist of massive intermetallic compounds, making it viable only for small die applications.

Thus, in this work focus has been on the development of Au-Ge based solder candidates. The promising Au-Ge based ternary alloys that were determined by the CALPHAD approach based on the solidification criterion were precisely produced using a hot-stage microscope."

Effect of Germanium Addition to Sn3.5Ag Lead Free Solder System for Overall BGA

IMAPS: "A study was conducted on BGA lead-free C5 solder joint system to assess the effect of Germanium addition to Sn3.5Ag solder alloy through comparison study of Sn3.5Ag vs Sn3.5AgGe.

The main objective of this study is to find a way to resolve solder surface oxidation after thermal processes, while determining if there’s any adverse effect on the solder joint by Germanium addition. The result of this study showed that addition of Germanium in Sn3.5Ag C5 solder system did not have solder surface oxidation after thermal processes, while Sn3.5Ag alloy alone showed discoloration. Also, addition of Germanium helped to improve solder joint strength of Sn3.5Ag."

Tin recovery from printed circuit boards of obsolete computers using a hydrometallurgical approach

Scopus: "This paper presents the preliminary experimental results for the recycling of printed circuit boards from obsolete computers with the aim of extracting and recovering tin by aqua regia leaching followed by precipitation.

Printed circuit boards were dismantled, cut into small pieces and fed into a cylinder mill. Ninety-eight percent tin extraction was obtained by leaching the powder leached in aqua regia solution (3.0N HCl/1.0N HNO3). Precipitates were obtained at three different pH values by neutralization of the leach liquor using NaOH. The precipitates presented 84.1% tin recovered from the powder feed and 85.8% from the leach liquor."

Possible changes to Toxic Substances Control Act echo ROHS

Factiva: "A proposed amendment to the 1976 TSCA (Toxic Substances Control Act) has been put before the US House of Representatives that could set regulations in the United States similar to those that the ROHS (restriction-of-hazardous-substances) directive set in the European Union.

The EDEE (Environmental Design of Electrical Equipment) Act, bill HR2420, aims to “ensure a uniform federal scheme of regulation of restrictions in the use of certain substances in electrical products and equipment in interstate and foreign commerce and for other purposes.” EDEE cites among its aims better trade and the prevention of potential disparities between state laws regarding restrictions on use of toxic substances in electrical products and equipment “that could create barriers to interstate commerce, domestic and foreign trade, and distort global competition.”

EDEE states that, after July 1, 2010, electronic-industry manufacturers cannot produce any product that contains a concentration value greater than 0.1% by weight of lead, mercury, hexavalent chromium, PBB (polybrominated biphenyl), and PBDE (polybrominated diphenyl ether) as measured in any homogeneous material the product contains. EDEE lists exemptions that include certain medical equipment, equipment with a voltage rating of 300V or more, and some fixed installations. For more information on EDEE, visit: www.ec-central.org/lead-free/hr_2420.pdf ."

CEO Jim McElroy to retire from iNEMI

EMSNow: "The International Electronics Manufacturing Initiative (iNEMI) announced that CEO Jim McElroy will be retiring from the consortium later this year. The iNEMI board of directors is currently interviewing for a new CEO and McElroy will continue in his current role until his replacement is found.

McElroy joined iNEMI in September of 1996 and is only
the second person to head the organization. (The first was Bob Klaiber, who was with iNEMI founding company AT&T/Lucent Technologies and agreed to lead organizational efforts during the consortium's first year.) During McElroy's tenure, the consortium evolved from NEMI (National Electronics Manufacturing Initiative) to iNEMI and established offices in Asia and Europe. Over this time period the membership has grown by 100% and now includes leadership firms from Asia as well as North America. In addition, the iNEMI roadmap has a substantially broader scope and following in the industry. The group's project portfolio has also grown significantly with the current focus on the environment, miniaturization and medical electronics."

Morphologies and characteristics of tin whiskers on surface of SnAgCuCe/Er lead-

Scopus: "Large sized CeSn3 and ErSn3 phases precipitated in the Sn-3.8Ag-0.7Cu-1.0Ce/Er solder alloy are oxidized when they are exposed in air, and tin whiskers can rapidly grow on the surface of the oxidized CeSn3 and ErSn3 phase.

The growth behavior of tin whiskers formed on the surface of the oxidized CeSn3 and ErSn3 phases was investigated. The results indicate that not only traditional cylinder-like tin whiskers but also some special ones are observed on the surface of the oxidized CeSn3 and ErSn3 phases, such as stripe-like tin whiskers, distorted tin whiskers, tin whiskers with variable cross sections, branch-type tin whiskers, merging-type tin whiskers and jointing-type tin whiskers and so on."

Beijing University, China

Rare earth elements are recognized as the 'vitamin' of metals, and trace amount of rare earth Ce can effectively improve the comprehensive properties of the solder alloy. However, rapid tin whisker growth has been found when excessive amount of rare earth were doped in the solder alloys. The results indicated that the rare earth-phase will be oxidized and induce volume expansion when Sn 3.8Ag0.7Cu1.0Ce solder was exposed in air, and the constraint action of the solder matrix on the volume expansion of the oxidized rare earth-phase will result in a compressive stress that will accelerate the growth of tin whiskers.

Effect of Ag content on properties of SnAgCuX lead-free solder

Scopus: "The effects of Ag content on the melting temperature, wettability and mechanical properties of the soldered joints were investigated. Microstructures and shear strength of SnAgCuX soldered joint were also studied under both as-reflowed and after high temperature aging conditions.

X includes Ni, P and Ce element. The experimental results indicate that the addition of trace amounts X element can remedy the decrease in properties of the solders to a certain extent due to the decrease of Ag content. Adding trace amounts of X element has little influence on the melting temperature of the solders, but obviously improves the wettability of solder and the shear strength of the soldered joints, and markedly decreases the effect of high-temperature aging on shear strength. The reason may be related to the modification of the microstructure and IMC of the solder alloys due to the addition of trace amounts of X elements."

Beijing University, China

Recovery of components and valuable metals from printed circuit boards

Scopus: "Most methods for the treatment of scrap printed circuit boards do not reclaim the components in working order as the boards are either fed to a copper smelter, to recover the valuable elements, or, simply landfilled. This work reports the dissolution of the solder in fluoroboric acid containing Ti4 ions which was particularly selective for solder, allowing the components to be recovered.

The solder was subsequently electrowon from the leachant. The boards were then shredded and the copper dissolved in ammonium sulfate and, then treated via solvent extraction to give an electrolyte suitable for electrowinning. The remainder of the metals were dissolved aqua regia, silver remained unattacked by the aqua regia, palladium precipitated as Pd(NH4)Cl6 in the presence of zinc and nickel, the gold was removed by solvent extraction and precipitated as nanoparticles. The aqua regia was then diluted and the zinc and nickel separated by solvent extraction"

Derek Fray, Cambridge University, UK

Using Microwave-Assisted Powder Metallurgy Route and Nano-size Reinforcements to Develop Hi

Scopus : "The best tensile strength was realized for composite solders reinforced with 1.5vol.% alumina and 0.7vol.% tin oxide particulates, which far exceeds the strength of eutectic Sn-Pb solder. The morphology of pores was observed to be one of the most dominating factors affecting the strength of materials."

Nai, Singapore University

Size and Volume Effects on the Strength of Microscale Lead-Free Solder Joints

Scopus: "The fracture behavior of microscale lead-free Sn-3.0Ag-0.5Cu solder joints of different sizes was investigated under quasistatic microtension loading.

The experimental results show that the ultimate tensile strength of a joint does not always increase with decreasing thickness-to-diameter ratio (d/t), which is commonly regarded as the dominant factor for mechanical constraint in the joint. A clear joint volume effect on the strength has been found, i.e., the joint's strength increases with decreasing joint volume {Mathematical expression} and the correlation follows an inverse proportional function reasonably well"

Influence of Lanthanum Additions on the Microstructure and Microhardness of Sn-3.5Ag Solder

Scopus: "As-cast, the addition of La increased the microhardness of the Sn-Ag solder due to the refining effect of Ag3Sn particles and increased formation of LaSn3 compounds. As the aging time was increased, the microhardness of the solders decreased and the Ag3Sn compounds coarsened. However, the coarsening of Ag3Sn compounds was retarded by La, and the size and amount of LaSn3 compounds did not change perceptibly with aging time. Therefore, La additions can improve the microhardness and thermal resistance of solder joints."

Lead-Free Under the Military Microscope

PCB007: "oncerns about the practical relationship between lead-free solders, long-term reliability and U.S. defense systems have prompted some major American defense contractors and suppliers of solder products to speak out, while Uncle Sam steps in to assess the risks and rewards of the new technology from a Pentagon perspective."

"Rockwell Collins is very concerned about the topic of lead-free soldering and the impact of new lead-free soldering materials on products," says Dave Hillman, principal materials and process engineer at Rockwell Collins in Cedar Rapids, Iowa. "The introduction of lead-free alloys and materials requires significant investigation because our avionics products are flight-critical and safety-critical and have long service lives of as much as 20 years."

Like other military manufacturers, Rockwell Collins has also experienced supply chain issues as the electronics industry-of which RoHS-exempted military and medical manufacturers represent relatively tiny niche markets-makes a transition to the almost virtual universality of lead-free.

"The supply chain impact has a large bandwidth, which includes increased component costs, significantly longer component procurement lead times, and the non-procureability of components," Hillman says.

Because of questions about the reliability and supply chain impact the lead-free solders, the U.S. Department of Defense will soon issue its first official report that addresses concerns about lead-free.

The effort, by the Defense Standardization Program Office, will result in guidelines for a lead-free control plan and training materials, according to Tim Kalt, the U.S. Air Force systems integration engineer who chairs the year-old working group.

Vibration reliability test and finite element analysis for flip chip solder joints

Scopus:"Vibration fatigue test and analysis methodology for flip chip solder joint fatigue life assessment have been developed by performing vibration tests with constant G-level and varying G-level input excitation.

The linear cumulative damage analysis method (Miner's rule) predicts non-conservative result for vibration fatigue life of flip chip solder joint. Finite element analysis (FEA) using a global-local-beam modeling method was used to calculate the natural frequency and were compared to experimental data. A quasi-static finite element analysis method was developed to investigate solder joint stress strain behavior for solder joint vibration fatigue life prediction. Harmonic finite element analysis was also carried out to predict solder joint fatigue life. Results from quasi-static analysis and harmonic analysis were compared. Based on Miner's rule and stress amplitude results from FEA results, different assumed cumulative damage index (CDI) factors were investigated in fatigue life prediction"

High-temperature lead-free solders: Properties and possibilities

Scopus: "Several candidate alloys have been proposed as alternative solders to hightemperature high-lead solders. None of them, however, can fulfi ll all the requirements to replace the current highlead solders.

One should understand the properties of the candidate alloys and must carefully apply these solders for high-temperature applications step by step in order to accomplish total lead-free assembly. Three major candidate alloys can be considered as hightemperature solders: Zn-Sn, Au-Sn, and bismuth-based alloys. Each has its own superior characteristics as well as some drawbacks, but all are believed to cover most of the high-temperature applications. There have been other choices appearing as high-temperature interconnections, such as materials based on conductive adhesive technology. In addition, epoxy adhesives filled with metallic solders or nanoparticles with or without silver fl akes exhibit excellent stability and can maintain stable interconnection after refl ow heat treatment. This paper reviews the latest work on high-temperature lead-free alternative interconnection

Osaka University, Japan

A Study of the Shear Response of a Lead-Free Composite Solder by Experimental and Homogenization Techniques

Scopus: "The current study proposes a combined experimental and modeling approach to characterize the mechanical response of composite lead-free solders. The influence of the reinforcement volume fraction on the shear response of the solder material in the joint is assessed. A novel optimized geometry for single lap shear specimens is proposed.

This design minimizes the effect of plastic strain localization, leading to a significant improvement of the quality of experimental data. The constitutive model of the solder material is numerically identified from the load-displacement response of the joint by using inverse finite element identification. Experimental results for a composite solder with 0.13 reinforcement volume fraction indicate that the presence of the reinforcement leads to a 23% increase of the ultimate stress and a 50% decrease of the ultimate strain."

EMPA, Switzerland

Cambridge University, UK

OKI Develops Static Pressure Soldering Technology for Lead-Free Soldering -- Tech-On!

Tech-On!: "By adopting static pressure soldering technology to the soldering section, it can control the solder flow almost completely, and prevent damage to the PWB pad patterns.

Moreover, by enabling preliminary heat to be applied in the preheat mechanism and adopting accurate control of liquid level depth in the soldering mechanism, OKI enables steady solder injection into the through-hole and reliable soldering filling. While conventional flow soldering machines had a 50% through-hole solder filling rate on a 6mm PWB, the new machine achieves a 100% rate.

OKI considers the static pressure soldering technology as a competitive strength in the EMS business, and this technology will be applied to manufacture information and telecom equipment, measuring equipment and medical equipment."

Vibration durability of Sn3.0Ag0.5Cu (SAC305) solder interconnects: Harmonic and random excitation

Scopus: "In this study, the durability of lead (Pb)-free tin(Sn3.0)silver(Ag0.5) copper(Cu) (SAC305) printed wiring assemblies (PWAs) is investigated under constant amplitude, narrow-band (harmonic) excitation and under step-stress broad-band (random) excitation, and compared to the durability of Pb-based Sn37Pb PWAs."

The results show that Sn37Pb assemblies last longer than SAC305 assemblies at similar excitation levels, for both harmonic and random excitations used in this study. The test specimens are identical for all tests, consisting of a PWA with plastic ball grid array components, quad flat pack components, leadless ceramic chip carriers, and leadless chip resistors. The test matrix includes test boards with different kinds of finishes and different aging conditions. Both the harmonic and random vibration tests are conducted on single-axis electrodynamic shakers. The harmonic vibration excitation is applied to a single specimen at a time, while the random vibration excitation is applied simultaneously to 20 test specimens using a specially designed test fixture. The flexural response of each test specimen mounted in the fixture is first thoroughly characterized before conducting the durability experiment. The flexural strain histories, measured on the PWAs, are used to compare the performance of the assemblies at different excitation conditions and also as inputs in other studies for stress analysis to quantify the damage in the solder joints.1 The durability tests are then conducted and time-to-failure is documented for the entire test matrix. The random durability tests are conducted at three temperatures: 125 °Centigrade (C), 25 °C (room temperature), and -40 °C. The harmonic tests are conducted only at room temperature. Destructive failure analysis (cross-sectioning, polishing, and microscopy) is conducted to confirm the failure modes. The test results presented here are analyzed in related publications1 to extract the high-cycle fatigue properties of the SAC305 and Sn37Pb solder materials.

What is halogen-free solder paste?

Scopus: "Various committees, consortia, and organizations are working to determine the safe use of halogen in electronics after non-government organizations (NGO) move towards reduction of halogen e-wastes.

It is highlighted that a 900 ppm of bromine or chlorine and a combined total of 1500 ppm as a safer option, which is a step forward towards electronics OEMs bid to replace halogen-containing electronics materials with halogen-free solder pastes. Laboratory work conducted to determine repeatability of halogen-free testing results to EN14582:2007 showed a difference between NC-A flux medium in chlorine and fluorine-free samples. No halides were found when these samples were tested to J-STD 004. SIR results for the halogen-free versus halogen-containing products indicated the halogen-containing product with slightly better SIR values than the halogen-free equivalent."

Thermal fatigue of SAC+, SN1001C

Factiva: "A significance of two factors, fine dispersoids in a solder and the anisotropic nature of beta-Sn, on thermal fatigue endurance is discussed using flip chips connected by Sn-xAg-0.5Cu (x: 1, 3 and 4 mass-%) lead free solders, together with Sn and Sn-1.2Ag-0.5Cu-0.05Ni, for comparison. Both 3Ag and 4Ag showed better thermal fatigue properties than Sn and 1Ag, and a thermal fatigue life of 1.2Ag with Ni was close to that of 3Ag despite of its low silver content.'

'Microstructures of the solders before thermal fatigue tests can be classified into a single crystal-like and a fine grain type. However, this classification, which affects the amount of thermal strain by the anisotropic nature of beta-Sn, cannot accurately describe thermal fatigue lives observed,' wrote S. Terashima and colleagues.

The researchers concluded: 'On the other hand, Vickers microhardness of the solders, which was resulted from fine dispersoids, showed good relationship with observed thermal fatigue endurance"

DKL Metals to distribute solder product

Manufacturing Talk: "DKL Metals has signed an agreement with Cobar to sell its line of solder products in the UK.

Cobar products include a range of solder, liquid fluxes, thinners, rework fluxes, cleaning agents, peelable solder mask, cobrush flux applicator and solder paste and cored solder wire."

Wettability of low silver content lead-free solder alloy

Scopus: "Wettability of low silver (Ag) content Sn-xAg-0.7Cu-0.5In lead-free solder (x = 0.1,0.3,0.5) on copper substrate was investigated.

Wetting balance test results indicated that varying small Ag content in the alloy affects the wettability of solders with higher Ag content showing better wettability. The contact angles of the solder alloy showed dependence on Ag content in solder and temperature. Solder alloy with no Ag content and 0.5 mass% Ag content displayed similar contact angle and qualitatively similar surface tension; however, the maximum wetting force is significantly difference, which indicates difference in the density of solder alloy. Effects of different fluxes on wettability were also studied"

Microstructure evolution and the constitutive relations of high-temperature solders

Scopus: "This study characterized the temperature-dependent constitutive parameters (yield strength, ultimate tensile strength, elastic modulus, strain hardening exponent) from the mechanical behavior of five high-temperature solders, 95Sn-5Sb, 95Pb-5In, 90Pb-10Sn, 92.5Pb-5Sn-2.5Ag, and 93Pb-3Sn-2In-2Ag, chosen such that T m > 518 K.

To model appropriately their mechanical responses under high-temperature thermal cycling, where the temperatures exceed 473 K, the material's parameters must be determined as a function of temperature. Uni-axial tensile tests were, therefore, carried out between 298 K and 473 K to determine the constitutive behavior of each solder.

95Sn-5Sb exhibited the highest strength over the temperature range tested except near 473 K. Pb-based alloys with a higher degree of solid solution (>5%) showed greater strengthening than those primarily strengthened by coarse precipitates. Additionally, microstructure changes in 90Pb-10Sn and 95Sn-5Sb were shown to be responsible for unexpected mechanical behavior at elevated temperatures."

Thermal fatigue endurance of lead-free composite solder joints over a temperature range

Scopus: "The thermal fatigue endurance of two lead-free solder/plastic-core solder ball (PCSB) composite joint structures in low-temperature co-fired ceramic (LTCC) modules was investigated using a thermal cycling test over a temperature range of -55'C to 150'C.

The investigated solder alloys were Sn-7In-4.1Ag-0.5Cu (SAC-In) and 95.5Sn-4Ag-0.5Cu (SAC). Three failure mechanisms were observed in the test joints. Transgranular (fatigue) cracking mixed with minor intergranular cracking was the dominant failure mechanism at the outer edge of the joints in both test assemblies, whereas separation of the solder/intermetallic compound (IMC) interface and creep cracking occurred in the other parts of the test joints. The propagation rate of the transgranular crack was lower in the SAC-In joints compared with in the SAC joints. Furthermore, the SAC solder seemed to be more prone to separation of the solder/IMC interface, and more severe intergranular (creep) cracking occurred in it compared with in the SAC-In solder. In the thermal cycling test conditions, the better thermal fatigue endurance of the SAC-In solder composite joints resulted in a 75% higher characteristic lifetime compared with the SAC composite joints."

Die Attach Solder Paste has enhanced thermal control., Henkel

Henkel: "To address the thermal requirements posed by smaller outline, higher functioning power semiconductor devices, Henkel has formulated an advanced die attach solder paste suitable for both high-lead and lead-free applications. Under the leading Multicore brand of solder materials, this innovative product ensures the thermal management efficiency critical for excellent long-term reliability and performance."

Multicore® DA100(TM) incorporates a no clean, ROLO flux system that can be used for high-lead applications and uniquely offers capability for lead-free processes as well. Using specific high temperature Pb-free alloys to offer the same thermal control necessary for today's rectifiers, power transistors, amplifiers, and many other consumer and automotive components, Multicore DA100 effectively complies with the environmental goal of lead elimination in power packages by 2013, as stipulated by ROHS legislation. Furthermore, packaging specialists that wish to use high-lead solders today, can easily move to lead-free solders tomorrow, while utilizing the same flux system offered through Multicore® DA100(TM). This ability to employ a consistent flux system is extremely beneficial to customers, as it minimizes the impact of flux reliability evaluation programs for such critical elements as cleanability, wire bonding and molding, among others

Investigation of mixed SAC and SnPb solder balls under high speed ball shear and pull tests

Scopus : "This paper presents the results of microstructural analysis of mixed solder joints which are formed by attaching different alloys of solder balls and pastes on the OSP pad finish.

The effect of thermal aging on the strength and fracture energy of the mixed solder balls during high speed ball shear/pull tests was also investigated in the study. The test specimens were aged at 125' for durations of 200, 500 and 1000hours. The correlations between the solder ball fracture force/energy, failure modes and inter metallic compound (lMC) thickness of the mixed alloy solder joints are also established."

Stokes University - Isothermal Mechanical Cycling

Scopus: "This paper investigates the degradation behaviour of lead-free Sn96.5Ag3.0CuO.5 solder. A series of isothermal mechanical cycling tests under different conditions has been conducted.

The tests were monitored in-situ with a high magnification camera system. Optical observations are presented from selected tests, showing the surface morphology during testing. In addition to the optical investigation, the load drop behaviour of the samples is analysed. The result is a deeper insight into the microscale failure behaviourofSAC305 during isothermal cycling."

Medical Electronics Symposium program finalized and on-line registration open

EMSNow: "The SMTA and MEPTEC announce the program for their co-organized 2009 Medical Electronics Symposium: Drivers for Technology, Health and the Economy on September 16-17, 2009 at Arizona State University, Tempe, AZ."

One paper mentions lead-free

IMAPS Presents International Conference & Exhibition on High Temperature Electronics Network (HiTEN)

Global SMT & Packaging magazine: "The objective of the HiTEN Conference is to have a unique forum that brings together researchers and practitioners in academia and industry from all over the world. All styles of practical high temperature electronics design and implementation approaches are encouraged, along with a variety of high temperature application areas.

Today the main semiconductor focus of HITEN is silicon and silicon on insulator (SOI). Although, HITEN is not simply a semiconductor focused network. HITEN provides a conduit for the exchange and dissemination of information on all aspects of high temperature electronics. It is a global network with users, suppliers, developers and fundamental researchers dealing in all aspects of High Temperature Electronics."

Nihon Superior debuts new Lead-Free presentation

EMSNow: "Nihon Superior Co. Ltd., a supplier of advanced soldering and brazing materials to the global market, announces that a new presentation about the challenges and issues in lead-free soldering is now available on the company's Web site.

Copper erosion, voiding, and tin whiskers are only a few of the problems in the field of lead-free soldering.

Nihon Superior has the knowledge with SN100C and its proven 10-year track record to solve users' challenges. SN100C can reduce bridges with uniform eutectic solidification, provide good through-hole fill, and reduce voiding resulting in low defect manufacturing and high reliability."

Indium Corp. solders together a perfect blog strategy

Success out of the Spotlight: "You’ve probably never needed Indium Corporation’s specialty alloys, solders, and solder pastes. However, Indium’s Marketing Communications Director, Rick Short, has crafted a corporate blog strategy that hyper-targets the people who do need his company’s products.

In a fairly recent podcast with Bernie Borges, Short discussed the impetus for implementing a very comprehensive blog strategy that has ballooned into 10 blogs by 15 writers. Short started out at Indium as a tech support specialist and acquired first-hand knowledge of Indium’s customers. Indium has a corporate culture of helping people understand how to use its products in relevant ways. Short commingled the acquired insights with the corporate culture and determined that social media would be a good way to reach potential customers.

Now Short oversees blogs such as the Halogen-Free Assembly Blog and Semiconductor Packaging Blog. Not exactly mass appeal. Knowing that the audience for industrial solders is educated and detail-oriented (tech support experience will teach you a lot), Short chose to provide content on subjects not getting a lot of coverage in local papers."

Calculating Solder Alloy Density

Circuits Assembly blog: "I continue to get much interest in the solder alloy density calculator I developed. It is now online here. It assumes no chemical interaction between the metals and no formation of interstitials. It works well for solder alloys.

Many people have an incorrect idea of how to perform this calculation. The most common incorrect concept is to multiply the % by weight of each alloy times its density and add them together. Using this incorrect approach one would calculate the density of tin-lead eutectic solder as 8.79 g/cc (0.63 x 7.29 0.37 x 11.34) vs the correct 8.4 g/cc. The correct derivation follows."

Enhancement of heterogeneous nucleation of Β -Sn phases in Sn-rich solders by adding minor alloying elements with he

Scopus: "The measured undercooling of pure Sn was about 30'C due to the difficulty of nucleating a solid Β -Sn phase from a liquid phase. To promote the heterogeneous nucleation of Β -Sn phases, the addition of impurity elements to the solders was suggested. Among the impurity elements, alloying elements with hexagonal closed packed (hcp) structures, such as Co, Zn, Ti, and Mg, were found effective to enhance heterogeneous nucleation of Β -Sn phases in Sn-rich solders.

Calculations of the density functional theory indicate that the interfacial energy between Β -Sn and Zn was relatively low. Minor alloying elements with hcp crystals are expected to provide more favorable heterogeneous nucleation sites for Β -Sn phases."

Wettability and interfacial reactions of Sn-Ag-Cu/Cu and Sn-Ag-Ni/Cu solder joints

Scopus "The effects of Cu and Ni additions on the wettability and interfacial reaction of Sn-Ag solder with Cu substrate were investigated.

The wettability of the Sn-3.0Ag-0.5Cu (or Ni) solder alloy was firstly measured by a wetting balance test. The formation and growth of intermetallic compounds (IMCs) between the Sn-Ag-Ni solder and Cu substrate were evaluated, and compared the results to the Sn-Ag-Cu/Cu system. In the wetting test, the Cu and Ni additions exerted positive and negative effects, respectively, on the wettability of the Sn-Ag solder."

Kester appoints experienced Technology Manager to Solder Paste R&D

EMSNow: "Kester is pleased to announce appointment of Adrian Hawkins, Ph.D., to the role of Technology and Development Manager. Adrian's primary responsibility will be to lead the Research & Development for Solder Paste in North America.

Dr. Hawkins comes to Kester with nearly 20 years of materials experience through his work at Eastman Chemical
Company in Kingsport, TN. He spent the last four years in the semiconductor industry at a start-up company called ZettaCore in Englewood, CO.

Dr. Hawkins obtained a B.S. in Chemistry from the University of Arkansas in Monticello and a Ph.D. in Physical Organic Chemistry from the University of Arkansas.

Brian Smith, Kester's Director of Marketing & Product Technology, stated, 'We are thrilled to have Adrian on board to lead our new product development team for solder paste. This is just another move that underscores our commitment to innovative products for our current and future customers. It also clearly demonstrates our willingness to invest in our business, even when many companies are cutting back due to economic conditions."

HDP User Group International Publishes General Purpose Lead Free Process Optimization Project Report

PRWeb: "'The General Purpose Lead Free Process Optimization study was conducted to assist in defining an acceptable assembly process window that would allow complex printed circuit boards with a variety of different size, weight and thermal mass devices to be successfully assembled without having to make compromises on product reliability,' said Thilo Sack (Celestica), Project Lead for the HDP User Group GPLF Initiative.

'The publication of the HDP User Group General Purpose Lead Free Process Optimization Report provides details on the impacts to solder joint reliability and microstructure changes resulting from having to operate at the extremes of the assembly process window to accommodate the significant assembly challenges associated with high complexity designs.'"

Three important symposia featured at SMTA International

EMSNow: "The Evolving Technologies Summit will feature sessions with topics on Counterfeit Electronics, Nanotechnology, Advanced Packaging, and an International Panel will discuss and debate timely topics that include The Next 100 Years, 'stretchable electronics', solar energy and extreme density electronics. A keynote presentation by Lee Smith, Amkor Technologies, on Interconnect Trends and Technologies in 3D Stacked Packaging will be featured at lunch."

The renowned Lead-Free Soldering Technology Symposium will begin with an overview of Pb-free processing and reliability investigations underway at England's National Physical Laboratory (NPL). The second session will examine the performance variables of new Pb-free solder alloys. The ever-popular case studies session will follow the alternative alloys papers. Featured case studies describe the challenges facing producers tasked with implementing Pb-free solders on high-reliability assemblies having a high mix of component types. The symposium will conclude with a very interesting reliability session.

Bga reballing reliability

Scopus: "The common element for all reballing methods is the need to reflow solder balls while aligned on the BGA lands in order to ensure a good metallurgical and mechanical attachment. The testing process includes reballing plastic ball grid arrays (PBGA) and subjecting them to various tests.

Cross-sections were performed to evaluate the grain structure and intermetallics formation of the devices before and after reballing as well as the potential effect of copper dissolution of the device lands. The manual method usually starts with the application of a high viscosity flux to the solder balls or residual solder of the device. BGAs reballing was performed using EZReball preforms. During the solder ball removal process, the manual method using wicking braid resulted in the BGA being subjected to fewer thermal stresses that would be encountered with a flowing solder bath method. All devices passed all electrical tests after numerous thermal cycles."

A novel metal-to-metal bonding process through in-situ formation of Ag nanoparticles using Ag2O microp

Scopus: "The metal-to-metal bonding has been successfully achieved via the bonding process using Ag metallo-organic nanoparticles at a bonding temperature of around 300-, which can be alternative to the current microsoldering in electronics assembly using high-temperature solders. However, further reduction of bonding temperature and/or bonding pressure is needed.

In the present research, a novel bonding process through in-situ formation of Ag nanoparticles instead of the filler material of the Ag metallo-organic nanoparticles has been developed. The Ag nanoparticles can form by the reduction of Ag2O particles. In this study, the Ag2O particles were mixed with triethylene glycol as a reducing agent to form a paste for bonding"

Osaka University, Hitachi, Japan

A novel accelerated test technique for assessment of mechanical reliability of solder interconnects

Scopus: "In this study a new method for quality assessment of solder interconnects under high strain vibrational shear loading is presented using an ultrasonic fatigue testing system in combination with a special experimental set-up.

Using this technique lifetime curves for solder ball bonds of two different Sn-Ag-Cu lead-free alloys were obtained. Failure mechanisms of the solder ball bonds were studied using SEM methods and the reliability curves were discussed with regard to the failure modes and the composition of the lead-free alloys. The applicability of the proposed method is discussed with regard to the literature data."

University of Vienna, Austria

Mechanical Shock Behavior of Bulk Pure Sn Solder

Scopus: "A fundamental understanding of the behavior of Pb-free solders under mechanical shock conditions is lacking. Reliable experimental stress-strain data over a range of strain rates needs to be obtained for reliability models. In this paper we report on the intermediate strain rate behavior of pure Sn solder.

The first part of the paper discusses modeling and analysis of the specimen geometry to obtain a relatively uniform stress (and strain) distribution within the gage section. Analysis by the finite element method (FEM) showed that a modified specimen geometry, with 10mm gage length, provided a homogeneous strain distribution, similar to the American Society for Testing and Materials (ASTM) E8 specimen geometry. The second part describes microstructural characterization and experimental results on pure Sn at intermediate strain rates (~10/s). Ultimate tensile strength and strain to failure in the 10mm specimen were quite similar to those of the ASTM specimen.

A double necking phenomenon was observed in the ASTM specimen, which was not observed in the 10mm specimen. FEM modeling of the dynamic behavior of the solder correlated very well with the experimental observations"

Formation of Sn dendrites and SnAg eutectics in a SnAgCu solder

Scopus: "The formation behaviour of grains and their components, including Sn dendrites, Cu6Sn5 and Ag3Sn intermetallic compounds (IMCs), in a SnAgCu alloy is investigated in an experiment in which it was possible to obtain the solid reactants directly from the liquid solder during the liquid-solid phase transformation. The results show that Cu6Sn5 IMCs are formed first in a grain; then large Sn dendrites; fibre-like Ag3Sn IMCs are formed ahead of the β-Sn matrix in the coupling process, generating eutectics."

University of Oxford, Loughborough University, United Kingdom