Global Life Cycle Impact Assessments of Material Shifts: The Example of a Lead-free Electronics Industry

Amazon.co.uk: Books: "Global Life Cycle Impact Assessments of Material Shifts describes the environmental implications of this shift to lead-free solders and conductive adhesives using the standardized methodology of environmental life-cycle assessment (LCA). As the product systems involved are rather small for interconnection materials it is possible – using uncertainty analysis and consequential LCA – to arrive at robust conclusions, even in the difficult holistic field of environmental cost accounting.

The lead-free shift has many implications, such as the export of electronics waste, resource consumption, recycling issues, and technology development. LCA is rapidly developing to include more and more impact assessment, and refined weighting methods. In the end, the goal is to be able to quantify the environmental consequences of decisions and this book presents tools, data, and methodologies in detail.

It provides an understanding of current technological shifts and the potential environmental consequences, along with several illustrative examples. Global Life Cycle Impact Assessments of Material Shifts will benefit engineers and environmental experts within the electronics and materials industry, enabling them to assess the environmental costs of their own product systems."

Morphology of the tin whiskers on the surface of a Sn-3Ag-0.5Cu-0.5Nd alloy

Scopus: "Rapid growth of tin whiskers has been observed on the surface of rosette-shaped NdSn3 intermetallic phase in a Sn-3Ag-0.5Cu-0.5Nd alloy after air storage. It is shown that various cross sections of NdSn 3 rosettes in the solder matrix reveal different morphologies of tin whiskers, which can be classified as four types: long fibers, short fibers, tiny sprouts, and hillocks.

The fibrous whiskers and tiny sprouts are found on the surfaces of specimens exposed to air at room temperature and 423 K (150 C), while hillocks appear only after storage at 423 K (150 C). In addition, it is observed that, in most cases, each oxidized NdSn3 intermetallic phase contains only a single whisker at its center. Through metallographic observations and chemical analyses on the cross sections of the oxidized NdSn3 intermetallics, a 'successive compressive stress model' has been proposed to interpret the tin whisker growth on the surface of a rare earth (RE)-containing solder."

Nihon Superior's Keith Sweatman to Present at TMS 2011

EMSNow: "Nihon Superior Co. Ltd. announces that Keith Sweatman, Senior Technical Advisor, will present a paper titled 'The Stability Window and Mechanical Properties of the Interfacial Intermetallic in Lead-free Solder Joints' at the upcoming TMS 2011 Annual Meeting & Exhibition. The presentation will take place Thursday, March 3, 2011 from 9:15-9:45 a.m. at the San Diego Convention Center in San Diego, CA.

The trend to copper UBM for lead-free area-array packages subjected to drop impact means that the properties of the intermetallic that forms at the solder/copper interface are major determinants of joint reliability. The transformation of the Cu6Sn5 from the close packed hexagonal η to the monoclinic η' at 186'C can reduce the impact resistance and long-term reliability of the solder joint.

In this presentation, the authors report new studies on the effect of Ni over the range 0-9 percent on the stabilization of the η phase. The distribution of Ni in the Cu6Sn5 and its crystal structure, lattice dimensions and thermal stability have been studied using SEM/EDS, TEM/EDS, synchrotron micro-XRF mapping techniques, synchrotron XRD, DSC and dilatometry. The mechanical properties of the intermetallic as a function of nickel content have been measured by nanoindentation. The data collected provides a basis for lead-free alloy formulation for area-array attachment."

Quantum SACSi patent

Factiva: "'A lead-free solder, comprising: from around 96.8% to around 99.3% tin; from 0.2% to 3.0% copper; from 0.02% to around 0.12% silicon, and optionally 0,005% to 0,01% P and/or 0,0005%-0.01 Ge."

Quantum Chemical Technologies (Singapore) Pte Ltd and Singapore Asahi Chemical & Solder Industries Pte Ltd filed the patent application on March 16, 2007. The patent application number is 2078/DELNP/2007 A. The international classification number is C22C13/00.

Effects of Processing and Amount of Co Addition on Shear Strength

Scopus: "Due to its high Young's modulus and strong bond with Sn, Co has been considered as one of the most promising alloying elements to improve the strength and reliability performance of Pb-free solders. In this study, the microstructual characteristics and mechanical properties of Sn-3.0Ag-0.5CuXCo (X=0wt.%, 0.1wt.%, 0.2wt.%, 0.45wt.%, and 1.0wt.%) solder joints on Cu substrates were investigated.

Moreover, an exploration on different joint fabrication methods and undercooling of solder alloys with both solder preform and paste was carried out. Experimental results indicated that the undercooling of the solder alloy can be altered by Co additions. During the metallurgical process, the added Co can dissolve into the solder matrix before rolling the preform. In addition, Co can form reinforcement particles in the solder paste.

The tendency for the formation and growth of an intermetallic compound (IMC) layer can be enhanced after incorporation of Co elements into the preform. However, a proper amount of Co addition to the paste can suppress IMC growth. The shear strength of solder joints reinforced with 0.1 wt.% or 0.2 wt.% Co addition can be increased. The solder joint made by paste with 0.2 wt.% Co addition exhibited the highest shear strength among all the solder joints"

Also Electromigration

Ma, L.a , Tai, F.a , Xu, G.a , Guo, F.a , Wang, X.b

a College of Materials Science and Engineering, Beijing University of Technology, Beijing, 100124, China

b State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083, China

Mechanical behaviour of typical lead-free solders at high strain rate conditions

Scopus: "3D packaging is one of the main emerging markets especially for mobile application within the last view years. Mobile devices are exposed and hence need to be reliable under to vibration or mechanical shock conditions. Therefore, material properties covering strain rate dependency have to be at hand within reliability studies.

Miniature bulk specimens were utilized to gain stress and strain data at strain rates from 20 s-1 to 600 s -1. Specimens consist of SnAg1.3Cu0.5Ni, SnAg3.0Cu0.5 and SnAg3.5 solder compositions. Ultimate strain, ultimate transversal contraction and fracture surfaces were analysed to determine the deformation and fracture behaviour. The strain rate dependent yield stress was determined and introduced into a material description feasible for finite element analysis (FEA). Finite element simulations were conducted for all solders at strain rates of 100 s -1 to 600 s-1. Results on fracture behaviour agreed well to the experiments. All studied solder compositions revealed ductile deformation behaviour changing only little with strain rate. A higher silver content as well as copper presence lead to higher yield stress level. The sensitivity to the strain rate alters with the copper presence only"

Head-in-pillow defect - Role of the solder ball alloy

Scopus: "The base alloy in these spheres is a low silver SnAgCu alloy. A number of minor alloy additions, focused on reducing the surface oxidation, have been tried. A comparative study of the fresh spheres and those oxidized at high temperature in air has been undertaken. Results show a big difference in wetting speed of the spheres with and without oxidation. Highly oxidized spheres have a thick oxide layer at the surface which, in certain cases, is impossible to breach.

It is this 'non-wetting' surface that is in-part responsible for the head-in-pillow defect. In this paper, quantitative measurements of the wetting time of spheres that come in contact with the solder paste at different times in the reflow cycle will be presented. Videos showing the in-situ soldering process will be shown along with the real time temperature and time measurements.

Results show the effect of micro alloy additives on spheres' surface oxidation and their wetting behavior. Non-collapsing spheres resulting in the head-in pillow defect will be shown. In addition, effect of the solder paste activity will also be presented. Further, analysis of the study done under different reflow conditions will be presented showing the best and the worst reflow conditions for the formation of the head-in-pillow defect."

Effect of Cu content on the interfacial reliability of SnAgCu solder joints

Scopus: "NEMI recommended Sn3.9Ag0.6Cu to replace the eutectic SnPb solder, but solder joints of this alloy have poor performance in reliability tests of electronic packages, especially the board level drop test. In this paper, the effect of Cu content in solder is studied on the interfacial reliability of SnAgCu solder joints on the Ni/Au plated pads. After preconditioning (three reflows post package assembly), some solder balls fell off during routine handling of the packages.

Cracking occurred between the IMC layers of (Cu,Ni)6Sn5 and Ni3Sn4. Formation of the dual IMC structure is explained from the perspective of interfacial equilibrium. It is suggested that to improve the drop performance of the packages that have Ni/Au plated pads the key is to avoid the formation of the layer-type of (Cu,Ni)6Sn5 at the interface. Approaches to do that are discussed. A rule for selecting solder alloy and surface materials on both sides of the joints is proposed for BGA packages"

Improvement of wettability and drop impact reliability by Al addition in SnAgCu solder

Scopus: "SnAgCu solder is most popular solder composition system in the package industry. Therefore, SnAgCu solder has been studied by many researchers to improve its properties. In this study, we ran tests to verify the effect of Al additive metal in SnAgCu solder in term of wettability and drop impact reliability."

The test solder compositions were Sn1.0Ag0.5Cu solder (Ref. solder) and Sn1.0Ag0.5Cu-xwt%Al solder and Al contents were 0.005, 0.01, 0.02, 0.1, and 0.12wt%. Generally, a higher wettability solder has high wetting force and short wetting time. In addition higher wettability solder shows enhancement of the bonding property on metal pads due to an increase in bonding area. In the results of the wettability test, Al doped solders showed higher wetting force and shorter wetting time than the Ref. solder. Meanwhile, wetting property was enhanced by increasing the additive content of Al metal. However, too much Al addition over 0.1 wt% resulted in a poor wetting property due to an increase in oxides In this study, the optimal content of the Al additive was selected to be 0.01-0.02wt%Al. In addition Sn1.0Ag0.5Cu0.02Al (under Al doped solder) and the Ref. solder were tested for their bonding property and drop property. Generally, IMC thickness, IMC shape, and the ductility of the solder bulk are the most intluential factors in drop impact tests. Therefore, before the drop impact test, these factors were tested as multi-retlows. At fIrst, in the ball shear test, the bonding property was stable as multi-retlows in all samples. In addition, there were no differences in IMC shape and IMC growth observed after 5 retlows between the Ref. solder and the Al doped solder. Meanwhile, in the hardness test, the Al doped solder showed lower hardness values compared with the Ref. solder. Thus, we judged that the Al doped solder after retlow has higher ductility and estimated that the Al doped solder would show enhanced drop properties in the drop impact test. Actually, in the results of the drop impact test on Cu-OSP PCB, Al doped solder showed an over 30% better drop impact reliability compared to the Ref. solder. Through this study, we could found that wettability and drop property of Sn-Ag-Cu solder system can be improved through the Al additive. However, Al doped solders actually have to be tested more for the application of PKG.

Lee, Y.W., Kim, I.H., Kim, E.S., Lee, J.H., Moon, J.T.

MK Electron Co., Ltd., 316-2, Kumeu-ri, Pogok-eup, Cheoin-gu, Yongin, Gyeonggi-do, 449-812, South Korea

Improvement of wettability and drop impact reliability by Al addition in SnAgCu solder

Scopus: "SnAgCu solder is most popular solder composition system in the package industry. Therefore, SnAgCu solder has been studied by many researchers to improve its properties. In this study, we ran tests to verify the effect of Al additive metal in SnAgCu solder in term of wettability and drop impact reliability."

The test solder compositions were Sn1.0Ag0.5Cu solder (Ref. solder) and Sn1.0Ag0.5Cu-xwt%Al solder and Al contents were 0.005, 0.01, 0.02, 0.1, and 0.12wt%. Generally, a higher wettability solder has high wetting force and short wetting time. In addition higher wettability solder shows enhancement of the bonding property on metal pads due to an increase in bonding area. In the results of the wettability test, Al doped solders showed higher wetting force and shorter wetting time than the Ref. solder. Meanwhile, wetting property was enhanced by increasing the additive content of Al metal. However, too much Al addition over 0.1 wt% resulted in a poor wetting property due to an increase in oxides In this study, the optimal content of the Al additive was selected to be 0.01-0.02wt%Al. In addition Sn1.0Ag0.5Cu0.02Al (under Al doped solder) and the Ref. solder were tested for their bonding property and drop property. Generally, IMC thickness, IMC shape, and the ductility of the solder bulk are the most intluential factors in drop impact tests. Therefore, before the drop impact test, these factors were tested as multi-retlows. At fIrst, in the ball shear test, the bonding property was stable as multi-retlows in all samples. In addition, there were no differences in IMC shape and IMC growth observed after 5 retlows between the Ref. solder and the Al doped solder. Meanwhile, in the hardness test, the Al doped solder showed lower hardness values compared with the Ref. solder. Thus, we judged that the Al doped solder after retlow has higher ductility and estimated that the Al doped solder would show enhanced drop properties in the drop impact test. Actually, in the results of the drop impact test on Cu-OSP PCB, Al doped solder showed an over 30% better drop impact reliability compared to the Ref. solder. Through this study, we could found that wettability and drop property of Sn-Ag-Cu solder system can be improved through the Al additive. However, Al doped solders actually have to be tested more for the application of PKG.

Lee, Y.W., Kim, I.H., Kim, E.S., Lee, J.H., Moon, J.T.

MK Electron Co., Ltd., 316-2, Kumeu-ri, Pogok-eup, Cheoin-gu, Yongin, Gyeonggi-do, 449-812, South Korea

Development trend of three-dimensional (3D) integration technology

Scopus: "Over the past decades, the downscaling of transistor dimensions has improved circuit performance, power, and integration density. However, conventional device scaling is approaching the physical limits and it is increasingly difficult to sustain the same miniaturization scaling rate. Three-dimensional (3D) integrated circuits that stack multiple functional chips using through-silicon-vias (TSVs) and low-volume lead-free solder interconnects may overcome these problems, because this approach makes it possible to reduce global interconnect length and to increase device density without shrinking device dimensions.

Different levels of 3D integration investigation were previously reported and updated. The current paper reviews the 3D integration technologies, including process technology and reliability

Sakuma, K.

IBM Research - Tokyo, 1623-14, Shimotsuruma, Yamato-shi, Kanagawa-ken 242-8502, Japan

Chip pillar/solder bump patent

Factiva: "'A new method and package is provided for the mounting of semiconductor devices that have been provided with small-pitch Input/Output interconnect bumps. Fine pitch solder bumps, consisting of pillar metal and a solder bump, are applied directly to the I/O pads of the semiconductor device, the device is then flip-chip bonded to a substrate. Dummy bumps may be provided for cases where the I/O pads of the device are arranged such that additional mechanical support for the device is required"

United States Patent no. 7,902,679, issued on March 8, was assigned to Megica Corp. (Hsinchu, Taiwan).

Intel Assigned Patent for Attachment Using Magnetic Particle Based Solder Composites

Factiva: "'Electronic devices and methods for fabricating electronic devices are described. One method includes providing a first body with a plurality of composite bumps thereon, the composite bumps comprising a solder and magnetic particles. The method also includes applying a magnetic field to the magnetic particles to generate sufficient heat to melt the solder and form molten bump regions containing the magnetic particles therein. The method also includes coupling a second body to the first body through the molten bump regions, and cooling the molten bump regions to form solidified composite bumps coupling the second body to the first body. Other embodiments are described and claimed."

Intel, Santa Clara, Calif., has been assigned a patent (7,902,060) developed by Rajasekaran Swaminathan, Tempe, Ariz

The influence of solder composition on the impact strength of lead-free solder ball grid array joints

Scopus: "This study aims to investigate the shear and tensile impact strength of solder ball attachments. Tests were conducted on Ni-doped and non-Ni-doped Sn-0.7wt.% Cu, Sn-37wt.% Pb and Sn-3.0wt.% Ag-0.7wt.% Cu solder ball grid arrays (BGAs) placed on Cu substrates, which were as-reflowed and aged, over a wide range of displacement rates from 10 to 4000 mm/s in shear and from 1 to 400 mm/s in tensile tests.

Ni additions to the Sn-0.7wt.% Cu solders has slowed the growth of the interface intermetallic compounds (IMCs) and made the IMC layer morphology smooth. As-reflowed Ni-doped Sn-0.7wt.% Cu BGA joints show superior properties at high speed shear and tensile impacts compared to the non-Ni-doped Sn-0.7wt.% Cu and Sn-3.0wt.% Ag-0.7wt.% Cu BGAs. Sn-3.0wt.% Ag-0.7wt.% Cu BGAs exhibit the least resistance in both shear and tensile tests among the four compositions of solders, which may result from the cracks in the IMC layers introduced during the reflow processe"

Tsukamoto, H.a , Nishimura, T.b , Suenaga, S.b , McDonald, S.D.a , Sweatman, K.W.b , Nogita, K.a

a School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4072, Australia

b Nihon Superior Co. Ltd., Osaka 564-0063, Japan

Senju In solder patent

Factiva: "'Provided are a lead-free solder which is capable of reducing the occurrence of a void and a joining member using the same which is excellent in adhesion, joining strength, and machinability. A lead-free solder alloy has a composition comprising 0.1 to 3% of Sn and/or 0.1 to 2% of Bi and a balance of In and unavoidable impurities and has an effect of suppressing the occurrence of a void upon soldering.

The lead-free solder alloy is melted down, a metal substrate is immersed, and the molten lead-free solder alloy and the immersed metal substrate are subjected to ultrasonic vibration, whereby a lead-free solder alloy layer is formed on a surface of the metal substrate to form a joining member. A heat sink and a package are subjected to reflow heating in the presence of a flux to be soldered through the joining member.'"

Hitachi Metals patent "Solder Alloy and Glass Bonded Body Using the Same"

Factiva: "The invention provides a solder alloy containing, by mass, 2.0 to 15.0% of Ag, 0.1 to 6.0% of Al, 0.01 to 0.50% of Y, the balance being Sn and unavoidable impurities. The solder alloy preferably contains 0.01 to 0.50% of Ge by mass. The solder alloy of the invention is suited to bonding oxides together and the oxides preferably comprise glass. The invention provides a glass bonded body formed by bonding glasses with the use of the solder alloy.'"

Study on properties of lead-free solder powder with different composition

Scopus: "Lead-free solder powder of Sn-Ag-Cu system was prepared with a supersonic atomizer designed by ourselves. Then the effects of different compositions on the properties of the powder were studied, and the microstructure of its brazed joint was observed, which was compared with that of Sn37Pb solder powder.

The results show that the Sn3Ag2.8Cu powder has the highest effective atomization efficiency, the lowest oxygen content, the best sphericity and surface smoothness in the three different compositions powders under the same superheat; the diffusion layer formed between Sn3Ag2.8Cu soldering paste and the copper substrate is thicker and their intermetallics are more irregular than those of Sn37Pb and Sn3Ag2.8Cu-0.1Ce soldering paste; the Sn3Ag2.8Cu-0.1Ce powder has higher effective atomization efficiency and oxygen content than the Sn37Pb powder."

Xu, T.a b , Jin, Z.b , Wang, D.a

a Xi'an Shiyou University, Xi'an 710065, China

b Xi'an Jiaotong University, Xi'an 710049, China

Tensile deformation behavior of nano-sized Mo particles reinforced SnAgCu solders

Scopus : "In this work, tensile deformation of Sn-3.8Ag-0.7Cu (SAC387) solder and composite of SAC387 reinforced with nano-sized Mo particles have been studied with strain rates from 10-5 to 10-1 s-1 and temperatures of 25, 75 and 125 'C.

It is found that the yield strength (σY.S ) and strain hardening exponent (n) are increased with the strain rate, but the n values decrease with increasing temperatures. The n values of the composite solder are also increased with the percentage of the Mo nano-particles (up to 1 wt.%) and thereafter decrease with further increasing of the Mo particle. The strain rate dependence of the Hollomon parameters is found to be stronger at higher temperatures for SAC387 solder, but it is weaker for the composite solders. Empirical equations for σY.S and Hollomon parameters with strain rate and temperatures have been found for both SAC387 and composite solders. Finally, the fracture surfaces of the solders are examined"

Rao, B.S.S.C.a b , Kumar, K.M.a , Kripesh, V.b , Zeng, K.Y.a

a Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore

b Institute of Microelectronics, Agency for Science, Technology and Research (ASTAR), 11 Science Park Road, Science Park II, Singapore 117685, Singapore

US Air Force - Mitigating Reduction of Hazardous Substances (RoHS) Lead -Free Issues in Aerospace Circuit Board Manufacture

Federal Business Opportunities: "This effort investigates the durability and survivability of current technology component families to establish aerospace and defense electronics Pb-free assembly process margins and practices."

Mechanisms of deformation in high-ductility Ce-containing Sn-Ag-Cu solder alloys

Scopus: "Rare-earth-containing Pb-free solders have gained widespread attention due to their superior ductility relative to conventional Pb-free alloys.

Our previous work has shown that new Ce-based alloys are also extremely oxidation resistant compared to La or Y-containing alloys. In this paper, we report on a mechanism-based model for the large increases in ductility with small addition of rare-earth element to Sn-3.9Ag-0.7Cu.

The mechanisms of ductility enhancement by Ce were observed in a scanning electron microscope, in interrupted shear-tests, where CeSn3 particles served as microscopic fracture and void nucleation sites. Micro-mechanical modeling using the finite-element method was used to examine the plastic strain field in solder affected by the particles. The concentrated deformation band was seen to be disturbed by the particles, resulting in a more uniform deformation pattern with reduced strains and thus enhanced ductility of the lap-sheared joint"

Xie, H.X.a , Chawla, N.a , Shen, Y.-L.b

a Materials Science and Engineering, Arizona State University, Tempe, AZ 85287-6106, United States

b Department of Mechanical Engineering, The University of New Mexico, Albuquerque, NM 87131, United States

Tensile properties and wettability of SAC0307 and SAC105 low Ag lead-free solder alloys

Scopus: "In this article, the tensile properties of low Ag lead-free solder alloys, SAC0307 and SAC105, are examined under various strain rates and temperatures. The wettability of these solders on Cu pad is also characterized by using different fluxes. The SAC305 and Sn37Pb solder alloys are also studied for comparison. Our results show that the properties of all solder alloys are dependent on the strain rate and temperature.

The ultimate tensile strength increases monotonously with the increment of strain rate. Both SAC0307 and SAC105 alloys possess lower strength and higher elongation ratio than SAC305 and Sn37Pb alloys. For all the fluxes used in this study, the SAC0307 and SAC105 alloys show the similar wettability to SAC305, whereas worse than that of Sn37Pb alloy. Increasing the activity of the flux does not improve the wettability of the SAC solder alloys on Cu pad effectively."

Cheng, F.a b , Gao, F.c , Zhang, J.a , Jin, W.a , Xiao, X.a

a Materials Science and Engineering School, Tianjin University, Tianjin 300072, China

b Tianjin Key Laboratory of Advanced Joining Technology, Tianjin University, Tianjin 300072, China

c McCormick School of Engineering and Applied Science, Northwestern University, Evanston 60208, United States

Tin-whisker failure problem from lead-free solder in military electronics is target of Air Force research job

Military & Aerospace Electronics: "U.S. Air Force electronics researchers are asking industry to develop a set of requirements virtually to eliminate the risks of tin whiskers and other problems related to lead-free solder in integrated circuit and circuit board manufacturing for aerospace and defense electronics applications.

The Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base, Ohio, released a broad agency announcement (BAA-11-16-PKM) last Thursday for a program called Mitigating Reduction of Hazardous Substances (RoHS) Lead-Free Issues in Aerospace Circuit Board Manufacture, which seeks to develop guidelines to help military electronics manufacturers choose lead-free components, as well as control thermal degradation of lead-free solders at the component and materials level."

Scientists at the Materials Integrity Branch of the AFRL Systems Support Division are asking industry experts to find ways of eliminating tin whiskers in lead-free solders to help reduce defects and field failures in aerospace and defense electronics. Tin whiskers, which can grow over time on lead-free solders, can cause short circuits and other defects in electronic systems.

Air Force researchers are interested in using a method that has been used on military-grade electronic parts since the mid-1960s to mitigate tin whisker problems: fusing the matte tin on lead-free parts and boards in a post processing step prior to board assembly, or by requesting a fused tin finish from parts vendors.

As more parts and materials are re-engineered to be compatible with the higher temperatures and longer dwell times necessary when using many lead-free alloys, the number of parts likely to be compatible with tin fusing should grow, Air Force officials explain. To come up with guidelines to achieve this, companies must identify component families normally only available with pure unfused matte tin finishes that are compatible with tin fusing.

For the program, the Air Force is asking companies to find ways to determine the suitability of electronic components or materials for soldering cycles during circuit card assembly, as well as ways to estimate time to failure due to this kind of soldering.

The program also asks companies to find the best ways of selecting components, materials, and vendors for design and manufacture of defense and aerospace electronics equipment using suitable lead-free solder alloys.

The Mitigating Reduction of Hazardous Substances (RoHS) Lead-Free Issues in Aerospace Circuit Board Manufacture program should be a 15-month, $1.7 million effort, with a contract to one company expected to be awarded as early as 30 June 2011.

Worldwide wave soldering overview

EMSNow: "EMS providers and OEM board level assemblers have an increasing number of procurement options to choose from when selecting a wave solder equipment supplier. As the effects of globalization continue, the competitive landscape is changing as a number of formerly geographic focused wave solder equipment suppliers enter the international capital equipment supply chain."

Alpha Fry Limited Files Patent Application for Solder Alloy

Factiva: "An alloy suitable for use in a wave solder process, reflow soldering process, hot air leveling process or a ball grid array, the alloy comprising from 0.08 - 3 wt.% bismuth, from 0.15 -1.5 wt.% copper, from 0.1 - 1.5 wt.% silver, from 0-0.1 wt.% phosphorus, from 0 - 0.1 wt.% germanium, from 0 - 0.1 wt.% gallium, from 0 - 0.3 wt.% of one or more rare earth elements, from 0 -0.3 wt.% indium, from 0 - 0.3 wt.% magnesium, from 0 - 0.3 wt.% calcium, from 0 - 0.3 wt.% silicon, from 0 - 0.3 wt.% aluminium, from 0 - 0.3 wt.% zinc, and at least one of the following elements from 0.02 - 0.3 wt% nickel, from 0.008 - 0.2 wt% manganese, from 0.01 - 0.3 wt% cobalt, from 0.01 - 0.3 wt% chromium, from 0.02 - 0.3 wt% iron, and from 0.008 - 0.1 wt% zirconium, and the balance tin, together with unavoidable impurities"

New Delhi, March 22 -- UK based Alpha Fry Limited filed patent application for solder alloy. The inventors are Anthony Ingham, Gerard Campbell, Brian Lewis, Bawa Singh, John Laughlin and Ranjit Pandher.

Alpha Fry Limited filed the patent application on May 30, 2007. The patent application number is 4088/DELNP/2007 A. The international classification number is B23K35/26.

Effects of Co nanoparticle addition to Sn-3.8Ag-0.7Cu solder on interfacial structure after reflow and ageing

Scopus: "Effects of Co nanoparticle additions to Sn-3.8Ag-0.7Cu on the structure of solder/copper interface have been studied after reflow and high temperature ageing (150 'C, up to 1008 h). Results show that the Co nanoparticles substantially suppress the growth of Cu3Sn but enhance Cu 6Sn5 growth. Cobalt nanoparticles reduce interdiffusion coefficient in Cu3Sn. It is suggested that the Co nanoparticles undergo surface dissolution during reflow and exert their influence, at least partially, through alloying effect"

Paste mixing paper

Haseeb, A.S.M.A., Leng, T.S.

Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

RoHS II Gathers Momentum

EMS007: "The new RoHS directive is expected to cover all but a very few instances of Electrical and Electronic Equipment (EEE). Annex I of the directive introduces a new, eleventh product category – ‘other electrical and electronic equipment not covered by any of the categories above (categories 1–10).’ Thus electrical and electronic equipment types that were not covered before will be covered by RoHS II, including formerly grey zone items such as electric toys"

High-temperature lead-free solder alternatives

Science Direct For lead-free solders in the high-temperature regime, unfortunately, a limited number of alloying systems are available. These are Bi based alloys, gold involving alloys and Zn–Al based alloys. Based on these systems, possible candidate alloys were designed to have a melting range between 270 °C and 350 °C. Each has its own superior characteristics as well as some drawbacks however none of them can fulfill all the requirements to replace the current high-lead content solders. Even the alternative technologies that are currently being developed cannot address several critical issues of high-temperature soldering. Therefore, further research and development of high-temperature lead-free soldering is obviously needed.

Vivek Chidambarama, b, , , , Jesper Hattela and John Halda

a Department of Mechanical Engineering, Technical University of Denmark, Building 425, Produktionstorvet, Lyngby DK-2800, Denmark

b Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), 11 Science Park Road, Singapore 117685, Singapore

Foxconn R&D center in Changsha, China to begin operation in April

EMSNow: "Foxconn Electronics (Hon Hai Precision Industry) is accelerating its deployment in western China with its R&D center in Changsha, Hunan province to commence official operations in April, according to industry sources.

Construction of the office building in Changsha has completed, and the company will begin to relocate its R&D staff in Shenzhen and other areas to Changsha in April, said the sources.

The R&D center will initially focus on the development of software, digital content and related products for China's triple network convergence, the sources added."

Microstructure of brazed joint and properties of two lead-free solder powders

Scopus: "Wettability, sphericity and particle size distribution of lead-free solder powders of Sn3Ag2.8Cu and Sn3Ag2.8Cu-0.1Ce and microstracture of brazed joint by the two solder were investigated by means of scanning electron microscopy (SEM) and laser particle size analyzer, and the microstructure of brazed joint and wettability of the powders were compared with those of the corresponding alloys"

The results show that the particle size distribution and sphericity of both Sn3Ag2.7Cu-0.1Ce and Sn3Ag2.8Cu powder are good. The Sn3Ag2.8Cu-0.1Ce solder powder possesses better wettability compared to Sn37Pb and Sn3Ag2.8Cu powders. Brazing with Cu substrate, the diffusion layer of Sn3Ag2.8Cu-0.1Ce solder powder is thinner than that of Sn3Ag2.8Cu powder, but the diffusion layers of both Sn3Ag2.8Cu and Sn3Ag2.8Cu-0.1Ce powders with Cu substrate are thicker than that of the corresponding alloy. The Sn3Ag2.8Cu-0.1Ce powder exhibits favorable combination of properties.

Xu, T.-H.a b , Wang, D.-H.a

a College of Materials Science and Engineering, Xi'an Shiyou University, Xi'an 710065, China

b College of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China

Alpha: Metal Costs Surge to Record Highs

Circuits Assembly "Strong global demand for metals such as tin and silver is driving up metal costs to all time highs, says Alpha.

Investors relying particularly on silver as an alternative investment are creating an additional price pressure, says the firm.

In early March silver surged to more than $36 per troy ounce.

In March 2007, tin had surged from $7,000 metric ton to $14,000 per metric ton. Today's levels are more than $28,000 per metric ton, says Alpha"

TMC.net There is additional price pressure created by investors relying, particularly on Silver, as an alternative investment choice to shield their investments from perceived higher risk alternatives. Alpha is sensitive to the dramatic impact escalating metal costs have on the electronics assembly industry. Cost of Metals is a critical driver to Alpha's entire business model and effectively managing this issue is at the very center of our organization's long term viability.

In May 2005, Alpha introduced Cost of Metals surcharges as our business was no longer able to absorb the severe increases in this critical raw material set to our product technologies. These metal surcharges are based on a series of Tiers linked to bands of Silver and Tin cost levels. In early March silver surged to over $36.00 a troy ounce.

Since there is no way to reliably predict the trends of metal prices, as the last six years have demonstrated, this surcharge program was designed to minimize daily fluctuations for our customers and allow reduced costs when the costs of metals return to more traditional levels.

In March 2007, Alpha introduced Tin metal surcharges. At that time tin had surged from $7,000 metric ton to $14,000 per metric ton. Today's levels are over $28,000 per metric ton. These extensive price increases have forced Alpha to share the increased cost of our Raw Materials with our entire channel to market.

The total impact of Silver and Tin cost increases, as well as the inter-day price swings, have a significant impact on our business. In order to maintain our current levels of technical support and the research and development that our customers expect, we will continue to implement the Silver and Tin surcharges.

Rising to the Challenge of Pad Cratering

Rising to the Challenge of Pad Cratering: "However, it's been difficult to determine what materials will work best in varied applications. 'In the beginning, there wasn't much attention to these types of failure because they were almost unheard of. But more companies started getting products ready to ship and realizing they had a problem that was not with one or two parts, but with many. These are catastrophic failures that are sometime latent. The defect doesn't always show itself in testing,' said Reza Ghaffarian, a NASA Jet Propulsion Lab Engineer."

That will help alleviate an issue that has become a major challenge for many manufacturers. "With the transition to lead-free solder and halogen-free PCB materials, one of the primary failure modes for lead-free BGAs is when copper pads on the board are pulled up, which causes pad cratering," said Satish Parupalli, an Intel engineer who helped coordinate the development of the IPC-9708 within the IPC 6-10d task group. "Assuming no manufacturing defects and test issues, people agree that the resin material is a driving factor for this failure mode. But with the transition to lead-free, there's been no one technique that helped us identify what changed in resin materials that caused this problem."

Gold/tin process from Stellar Industries improves wettability in die bonding

Advanced Packaging: "The new gold/tin (AuSn) process from Stellar Industries is ideally matched to Stellar’s proprietary CPU copper on aluminum nitride (AlN) submounts with its sharp guillotine edge for precise edge alignments.

The new gold/tin process improves wettability and offers variable freeze time options to ensure efficient laser die bonding. Reduced micro-voiding improves thermal performance for increased reliability.

The AuSn performance is available from 70Au/30Sn to 80Au/20Sn compositions."

Morphology of the tin whiskers on the surface of a Sn-3Ag-0.5Cu-0.5Nd alloy

Scopus: "Rapid growth of tin whiskers has been observed on the surface of rosette-shaped NdSn3 intermetallic phase in a Sn-3Ag-0.5Cu-0.5Nd alloy after air storage. It is shown that various cross sections of NdSn 3 rosettes in the solder matrix reveal different morphologies of tin whiskers, which can be classified as four types: long fibers, short fibers, tiny sprouts, and hillocks.

The fibrous whiskers and tiny sprouts are found on the surfaces of specimens exposed to air at room temperature and 423 K (150 C), while hillocks appear only after storage at 423 K (150 C). In addition, it is observed that, in most cases, each oxidized NdSn3 intermetallic phase contains only a single whisker at its center. Through metallographic observations and chemical analyses on the cross sections of the oxidized NdSn3 intermetallics, a 'successive compressive stress model' has been proposed to interpret the tin whisker growth on the surface of a rare earth (RE)-containing solder"