SN100C P600 D4 is a halogen-free high-reliability no-clean lead-free solder paste that does not contain F, Cl, Br and I. Designed as a high-reliability solder paste for high-density assembly with stable printability, the paste provides excellent reflow with good wetting and minimum incidence of mid-chip balling, and low residue. Additionally, it typically can be reflowed with a profile similar to that which is commonly used with SAC305 and SAC405 with 240°C peak.
Thursday, December 24, 2009
Friday, December 11, 2009
SAC105 bump ageing experiments
Factiva: "Cold bump pull tests performed on wafer level chip scale packages using SAC105 solder bumps show an increase in the occurrence of brittle failure modes with aging temperature and time,' scientists in Quezon City, Philippines report.
'Fast intermetallic growth at 0-1000 h can be attributed to (Cu, Ni)(6)Sn-5, while the decrease in intermetallic growth rate at t> 1000 h can be attributed to diffusion processes leading to (Cu,Ni)(6)Sn-5 and (Ni,Cu)(3)Sn-4 formation and growth. Ni diffuses toward the solder bulk and saturates at 175-200 degrees C, while Cu diffuses from the under bump metallization (UBM) toward the solder bump at 125-150 degrees C. Interactions between Cu and Ni atoms lead to saturation of their atomic % gradients due to intermetallic formation,"
'Fast intermetallic growth at 0-1000 h can be attributed to (Cu, Ni)(6)Sn-5, while the decrease in intermetallic growth rate at t> 1000 h can be attributed to diffusion processes leading to (Cu,Ni)(6)Sn-5 and (Ni,Cu)(3)Sn-4 formation and growth. Ni diffuses toward the solder bulk and saturates at 175-200 degrees C, while Cu diffuses from the under bump metallization (UBM) toward the solder bump at 125-150 degrees C. Interactions between Cu and Ni atoms lead to saturation of their atomic % gradients due to intermetallic formation,"
Friday, December 4, 2009
Solder material maker Shenmao expects revenues in 2010 to grow 20% on year
Digitimes: "Taiwan-based solder material maker Shenmao Technology expects its revenues in 2010 to grow 20% and reach a record high compared to 2009.
The company's October 2009 revenues dropped about 10% to NT$516 million (US$16.03 million) since the PCB industry is entering the low season, revenues are also expected to see a 10% sequential decrease in the fourth quarter, weaker than its earlier expectation of a flat or single-digit decline, according to the company.
On the other hand, Shenmao's shipments and revenues generated from BGA solder spheres both hit records in October, with revenue share reaching 6.4%. Revenue share of bumping solder pastes was less than 1%, but the company expects the segment to see rapid growth in 2010. More than half of Shenmao's products are used in notebooks.
The company is focusing on high-margin products which account more than 30% of total revenues. It estimates consolidated gross margin to remain around 18% in the fourth quarter."
The company's October 2009 revenues dropped about 10% to NT$516 million (US$16.03 million) since the PCB industry is entering the low season, revenues are also expected to see a 10% sequential decrease in the fourth quarter, weaker than its earlier expectation of a flat or single-digit decline, according to the company.
On the other hand, Shenmao's shipments and revenues generated from BGA solder spheres both hit records in October, with revenue share reaching 6.4%. Revenue share of bumping solder pastes was less than 1%, but the company expects the segment to see rapid growth in 2010. More than half of Shenmao's products are used in notebooks.
The company is focusing on high-margin products which account more than 30% of total revenues. It estimates consolidated gross margin to remain around 18% in the fourth quarter."
Next Generation Adaptable NANOPillar Bumping Technology
Factiva: "'Looking forward, NANOPillar(TM) bumping is a key enabling technology for cost reduction by Au wirebond displacement in conventional packages as well as for emerging 3D packaging applications. The interest in Pillar bumping by our customers has been overwhelming; particularly in light of the diverse solder alloy options that are enabled. In developing our NANOPillar(TM) bumping technology, our focus has been to develop a proprietary, next generation pillar bumping technology with unsurpassed solder composition versatility.'"
Occam Process WO patent
WO2009140050A2: "A system for prototyping electrical circuits, as well as creating production circuits, without using solder. Stand-in electrical components are placed on a carrier and scanned . From the resulting data, a machine tool or laser ablation system then creates a negative master with aperture(s) into which production components are placed and secured. Component leads or packages are encapsulated with electrically insulating material with vias exposing the leads.
Traces connect appropriate leads forming a circuit sub-assembly which can serve as a basis for a circuit assembly formed through a reverse-interconnection process."
Applied Nanotech Awarded $500,000 for Tin Whiskers
Nanotechnology: "During this eighteen month Phase II Small Business Innovation Research program, which results from successful completion of a Phase I award, Applied Nanotech will focus on optimizing its patented (pending) process for the mitigation of tin whiskers. Both the MDA and NASA have reported that tin whiskers have been the cause of more than $1 billion in catastrophic damage to satellites, missiles, and other electronic equipment.
Current recognized mitigation techniques add cost and complexity to the manufacturing process and have had mixed success. Our unique ability to perform tin whisker remediation with a pulse of energy, while simultaneously preventing new whiskers from growing, provides a distinct advantage over competitive methods.
'As the world is moving toward lead free solder, the tin whiskers issue will become very problematic, not only for defense and aerospace applications, but for all electronic products,' said Dr. Zvi Yaniv, CEO of Applied Nanotech, Inc.
'This improved method of remediation of tin whiskers is a direct outgrowth of our activity in technical inks and pastes,' said Doug Baker, CEO of Applied Nanotech Holdings, Inc. 'We continue to broaden the applicability of our technology to generate increased revenues.'"
Current recognized mitigation techniques add cost and complexity to the manufacturing process and have had mixed success. Our unique ability to perform tin whisker remediation with a pulse of energy, while simultaneously preventing new whiskers from growing, provides a distinct advantage over competitive methods.
'As the world is moving toward lead free solder, the tin whiskers issue will become very problematic, not only for defense and aerospace applications, but for all electronic products,' said Dr. Zvi Yaniv, CEO of Applied Nanotech, Inc.
'This improved method of remediation of tin whiskers is a direct outgrowth of our activity in technical inks and pastes,' said Doug Baker, CEO of Applied Nanotech Holdings, Inc. 'We continue to broaden the applicability of our technology to generate increased revenues.'"
Henkel introduces zero halogen multicore HF108 solder paste
EMSNow: "Though industry consortia have set some competing standards as to the acceptable levels of halogen, the common benchmark is up to 900 ppm bromine, 900 ppm chlorine and maximum total halogens of 1500 ppm. Henkel, however, has developed a material that has zero deliberately added halogens, yet has the excellent reflow and stability characteristics normally associated with halogen-containing materials.
'Multicore HF108 has no intentionally added halogen and is under the limit of detection in the rigorous oxygen bomb/ion chromatography test,' says Steve Dowds, Henkel Global Product Manager for Solders. 'Taking out the halogen is easy -- the difficult part is how to replace it.'"
'Multicore HF108 has no intentionally added halogen and is under the limit of detection in the rigorous oxygen bomb/ion chromatography test,' says Steve Dowds, Henkel Global Product Manager for Solders. 'Taking out the halogen is easy -- the difficult part is how to replace it.'"
Lead free production & problems when changing the processes
evertiq.com: "In general, different variations of the Sn-Ag-Cu alloy (SAC), with silver content from 3.0% to 4.0%, are all acceptable compositions for lead-free soldering (including reflow and wave soldering). Studies using SMT test vehicles, by IPC in collaboration with solder suppliers and EMS companies (such as Flextronics), have concluded that there is no significant difference in the process performance and thermal cycling performance among these different variations of the alloy composition.
However, when the silver content is much lower (such as SAC105), the thermomechanical reliability performance is adversely affected, due to the reduced amount of Ag3Sn intermetallic compound in the solder microstructure. SAC105 is more suitable for BGA/CSP balls for handheld products where drop test reliability is more critical than thermal cycling reliability."
However, when the silver content is much lower (such as SAC105), the thermomechanical reliability performance is adversely affected, due to the reduced amount of Ag3Sn intermetallic compound in the solder microstructure. SAC105 is more suitable for BGA/CSP balls for handheld products where drop test reliability is more critical than thermal cycling reliability."
The tin-copper alloy is a viable alternative for wave soldering of cost sensitive products where reliability is less critical. Several variants of the Sn-Cu alloy have also been considered by the industry, including silver (Ag), nickel (Ni), and other elements as alloying additions. In addition to cost, reliability, hole-fill, and copper dissolution (especially for PTH rework) are important considerations when selecting an alloy for wave soldering.
Introducing and qualifying a new solder alloy for volume production is a significant undertaking which demands an industry-wide effort. Flextronics is working with several industry consortia to study various alternative lead-free alloys, for solder paste, bar, BGA solder balls, etc., with the hope of finding a common alloy that is suitable for across-the-board applications.
Lead-free fillet tearing
EMT Worldwide: "Selected combinations of tin / silver / copper with a silver content of 3% - 4% are prone to cause this tearing during solidification of the solder. Tin / copper and tin / copper / nickel do not seem to feature this defect type. The solder is rough in appearance due to the shrinkage of the metal between the tin dendrites. There is no evidence currently that this has any impact on the reliability of the solder joints."
EWI Signs Agreement With S-Bond Technologies
Earth Times: "EWI SonicSolder is an EWI patented binary lead-free solder alloy that melts at 231 degrees C. In conjunction with ultrasonic soldering, it can be used to join difficult-to-wet materials like aluminum, titanium, glass, ceramics, and dissimilar materials. Potential applications include tubing, electronics, medical products, and structural components. In various base-metal (copper, aluminum, titanium) combinations, shear strength of about 5 ksi has been obtained. Currently available in ingot form, the solder will be available in a wire form at a later date."
Intermetallic Formation and Fluidity in Sn-Rich Sn-Cu-Ni Alloys
Scopus: "This paper investigates the phase equilibria and solidification behavior of Sn-Cu-Ni alloys with compositions in the range of 0wt.% to 1.5wt.% Cu and 0wt.% to 0.3wt.% Ni.
The isothermal section at 268C in the Sn-rich corner was determined. No evidence for a ternary phase was found, and the section is in good agreement with past experimental studies that report wide solubility ranges for (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. The vacuum fluidity test was applied to compositions that are liquid at 268C to map the variation in microstructure and flow behavior with composition in this system. Significant variations in fluidity length were measured among the Sn-Cu-Ni alloys, and the variations correlate with the microstructure that develops during solidification.
The generated fluidity map enables the selection of Sn-Cu-Ni solder compositions that exhibit good fluidity behavior during solidification and form near-eutectic microstructures."
Synthesis and DSC study on Sn3.5Ag alloy nanoparticles used for lower melting tempera
Scopus: " A possible way to decrease the melting temperature of a solder alloy is to decrease the alloy particle size to the nanometer range. Sn3.5Ag nanoparticles with different size distribution were synthesized using chemical reduction method by applying NaBH4 as reduction agent. The melting properties of these synthesized nanoparticles were studied by differential scanning calorimetry (DSC), and size-dependent melting temperature depression of these nanoparticles has been observed. Gibbs-Thomson equation was used to analyze the size-dependent melting temperature property, giving a good prediction of the melting temperature depression for the Sn-based lead-free solder alloy nanoparticles."
Effects of Ni addition on the interfacial reactions between Sn-Cu solders and Ni substrate
Scopus : "This research investigates the effects of adding a small amount of Ni to solder.
The interfacial reactions between Ni and the Sn-Cu solders at 250C are examined. Two sets of Sn-0.7wt% Cu-xNi solders and Sn-1.0wt% Cu-xNi solders (x=0.02, 0.05 and 0.1wt%) were prepared. The results reveal that the interfacial reactions are very sensitive to Ni. With increasing Ni addition, the reaction phase grain, Cu6Sn5, becomes larger and its morphology changes from a rod-like shape into a faceted structure. The reaction progressions are accelerated in comparison with those without Ni addition. The solder spreading effect on the Cu6Sn5 morphology was also investigated. Cu6Sn5 exhibits a gradual change in microstructure from the center to the rim for the case when the solder ball spreads over a Ni substrate. However, the solder does not alter the Cu6sn5 microstructure while reacting on a small Ni pad without spreading. This suggests that the Cu and Ni contents in the solder near the interface vary during the solder ball spreading process."
Investigation of rare earth-doped BiAg high-temperature solders
Scopus : "In the present work, the microstructure and properties of the rare earth Ce-doped BiAg solders with various Ag content are investigated.
The results indicate that the maximum of the shear strength appears in the BiAg solder joints containing 5 and 7.5 wt.% Ag. At the same time, a similar trend appears in the hardness test of the BiAg bulk solders. Moreover, the results show that the microstructure and properties of the solders can be modified due to the unique properties of rare earth element. Small amounts of rare earth addition may enhance the wettability of SiAg solder on Cu substrate, and result in the increase of the shear strength of the solder joints. However, the rare earth addition may not give obvious influence on the melting temperature and the electrical conductivity. Thus, it is expected that the BiAg solder containing small amounts of rare earth element may possess a better potential as a replacement for high-Pb solders"
Effect of praseodymium on the microstructure and properties of Sn3.8Ag0.7Cu solder
Scopus: "Effects of Pr addition on wettability, microstructure of Sn3.8Ag0.7Cu solder were studied, the mechanical properties of solder joints were investigated and the fracture morphologies were also analyzed in this paper.
The results indicate that adding appropriate amount of Pr can evidently improve the wettability of solder, and it is also found that Pr can refine the β-Sn dendrites and reduce the intermetallic compounds growth inside the solder due to the fine PrSn3 particles formed in the solder which can act as heterogeneous nucleation sites. Moreover, the joints soldered with the SnAgCuPr solders possess sound mechanical properties which may result from the finer microstructure improved by the Pr"
Development of Au-Ge based candidate alloys as an alternative to high-lead content solders
Scopus: "Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The changes in microstructure and microhardness associated with the addition of low melting point metals namely In, Sb and Sn to the Au-Ge eutectic were investigated in this work. Furthermore, the effects of thermal aging on the microstructure and its corresponding microhardness of these promising candidate alloys have been extensively reported."
the addition of Sb to the Au-Ge eutectic would not only decrease its melting point but would also improve its ductility substantially and the lattice strains induced by the In atoms were the most effective strengthening mechanism
Wednesday, November 4, 2009
Tin Pest in Sn-0.5Cu Lead-Free Solder Alloys: A Chemical Analysis of Trace Elements
Scopus: "Two samples of Sn-0.5Cu solder alloys, stored at -18'C for 7 years, were chemically analyzed by an inductively coupled plasma-optical emission spectroscopy method. One of the samples was unaffected by this exposure; the other one had completely transformed into brittle α-Sn.
Ten elements were found to exhibit statistically significant differences in their concentrations between the two samples, with the higher always associated with the untransformed sample. The highest concentrations were found for elements with an appreciable solubility in Sn, i.e., Bi, In, Pb, and Sb"
Open University, UK
Vienna University, Austria
Evaluation of tin-whisker growth during thermal-cycle testing using stress- an
Scopus: "Two models with different crystal-orientation distributions were evaluated. Samples with a higher tin atomic density were found to be more likely to have longer tin whiskers and higher whisker density. It is concluded from these results that the tin-atomic-density distribution calculated with this model can be used as an effective indicator of the propensity to form tin whiskers."
The influence of the Pb-free solder alloy composition and processing parameter
Scopus: "The test results show a direct relationship between characteristic fatigue life and Ag content, with the higher Ag content alloys outperforming those with the lowest Ag content. As might be anticipated, there also was a consistent inverse relationship between fatigue life and dwell time for the Pb free solders. The failure analysis and microstructural evolution is characterized with optical metallography and scanning electron microscopy and the fatigue reliability of the Pb free solders is discussed in terms of the microstructures"
Accelerating the effects of aging on the reliability of lead free solder joint
Scopus: "Three common lead free alloys were selected for the present study: 98.5Sn-1.0Ag-0.5Cu (SAC105), 96.5Sn- 3.0Ag-0.5Cu (SAC305), and 95.5Sn-4.0Ag-0.5Cu (SAC405). The present study did not address effects of solder volume, pad size, pad finish or reflow profile, focusing on 30 mil (760μm) diameter solder spheres reflowed onto solder mask defined OSP coated Cu pads with a typical lead free profile. Isothermal aging was conducted for up to 3,000 hours at temperatures of 70'C, 100'C, and 125'C respectively.
As expected, the resulting room temperature properties all decreased with aging time, and faster so for higher aging temperatures. Some of the acceleration factors extracted for the evolution of the individual properties did, however, differ greatly for a given alloy. The only way to establish the same microstructure, and thus the same combination of properties, faster by annealing at a higher temperature is thus to fully stabilize it. This takes thousands of hours even at 125'C, i.e. it is not practical for real assemblies"
Effects of additional elements (Fe, Co, Al) on SnAgCu solder joints
Scopuss: "One approach to improve the thermal fatigue properties of these alloys is to add a further alloying element SAC X. Until now, further elements have mainly been added by metallurgical alloying, requiring special equipment and conditions. The powder production is even more difficult. In this paper a new way how to add minor amounts around 0.1 wt.-% of a forth element to SAC solder joints is presented. One possibility is to do the doping during the reflow process adding the additional elements via the flux by incorporating Co-, Fe-, Al- or other metal compounds into the flux. Experiments have shown that Co and Fe were successfully added while for certain other elements like for example Al this was not possible until now. In comparison to standard SAC solder the Co containing solder shows a refined microstructure and Co is found in the intermetallic phase Cu6Sn5. Fe which has been found at grain boundaries is not only attractive as alloying element but as metallization layer, too. It is possible to deposit Fe on printed circuit boards using electroplating. During soldering the slowly growing FeSn2 phase forms between the solder and the Fe layer"
Monday, November 2, 2009
Solder Ball Attachment Assessment of Reballed Plastic Ball Grid Array Packages
Scopus: "For area array packages, the practice is referred to as reballing. While reballing has been used for part reclamation, very little information is available on the reliability of reballed parts. This paper presents lead-free ball grid array (BGA) packages subjected to two ball removal and two ball reattachment techniques. Solder attach strength was used as a metric to examine the reballing process."
Lead-free solders with rare earth additions
Scopus: "There have been significant research efforts to improve the properties of globally recognized lead-free solders, such as Sn-Ag-Cu, Sn-Cu, Sn-Bi, etc. Rare earth (RE) elements have been selected in the current research to be added into lead-free solders as alloying elements in an effort to improve the comprehensive properties, such as wettability, microstructural stability, creep resistance, and mechanical strength and integrity of the solders.
This article overviews the background and rationale for the alloy development, the fabrication techniques for RE-containing solders, the roles of RE elements, as well as current status of RE-containing solder research. Examples of several representative RE-containing solders are introduced. The effects of RE element addition on the wetting behavior, microstructure, and mechanical properties of certain lead-free solder alloys are presented and analyzed."
Beijing University, China
Stabilisation of Cu6Sn5 by Ni in Sn-0.7Cu-0.05Ni lead-free solder alloys
Scopus: "Cu6Sn5 exists at least in two crystal structures with an allotropic transformation from monoclinic η'-Cu6Sn5 at temperatures lower than 186 'C to hexagonal η-Cu6Sn5. We recently discovered that the hexagonal structure of Cu6Sn5 in lead-free solder alloys with trace Ni additions is stable down to room temperature using high resolution TEM/ED/EDS.
This report further confirm the phase stabilising effect of Ni by analysing samples of Cu6Sn5 extracted from a Sn-0.7wt%Cu-0.05wt%Ni lead-free solder alloy. Techniques used include X-ray diffraction, transmission electron microscopy and differential scanning calorimetry"
Lead-Free Looking for the Holy Grail
EMS007 Perspectives:: "The continued development of alloys has led to at least two shifts in the industry.
A need exists to rationalize the data from different sources on the properties of the alloys and how the testing for these properties is performed. For example, iNEMI has put its continued effort in lead-free solders into this area and away from alloy specification itself.
In addition, many OEMs are moving away from trying to define the composition of the solder to specifying the performance of the final assembly. They have developed, or are developing, a specification for what they want the assembly to be able to demonstrate, and, as long as this can be demonstrated, the actual solder and process will be left to the EMS. The major remaining concern is that the solder materials be obtained in conformance with international concerns for the environment and human rights."
New Co alloys from Balver Zinn
EMT Worldwide: "The second in the new series is Tin Silver based i-SAC Solder Family i-SAC105. The melting characteristic of silver containing alloys has been improved with the addition of Cobalt (Co). Solder i-SAC105, with silver composition on request between 0.5 – 1.5%, offers the advantages of silver free alloys and the characteristics of silver containing alloys. i-SAC105 produces low priced, bright and shiny solder joints and a fine grain microstructure, even with this low addition of silver content. As with the previous product, Cobalt is responsible for a homogenous microstructure in comparison to standard SnAg alloys. A formulation including Germanium (Ge) again plays the role of antioxidant, preferentially reacting with oxygen to protect the solder from the oxidation that results in the formation of dross. i-SAC105 has a melting point of 217'C to 227'C"
New Alloys Lead to Test Innovations
Surface Mount Technology: "The problem with SAC alloys, particularly SAC105, is that they tend to contaminate contacts faster than SnPb. SAC105, with its reliability in drop tests, has become a favored alloy with mobile electronics manufacturers."
Fine-pitch BGAs are particularly difficult to contact, and fine-pitch spring probes have even higher resistances as a result of their smaller spring force. This, together with the tendency of SAC105 to contaminate spring probes, challenges test applications. When maintenance is required – as often as every 200 cycles for BGAs with SAC105 – cost of test goes up and production test cycles speeds go down. Contamination transfers from the package to the contact tip. The degree of contamination depends on the solder alloy used and is aggravated by high temperature, another hallmark of lead-free assembly.
Some interconnects that are harder than Au show success, including Pd alloys. Pd has higher resistance values and to test, low force and low conductivity are needed. With increased resistance comes reduced first pass yields, so many test engineers simply replace Au-plated contacts more frequently. Other spring probe plunger manufacturers use coatings to help solve contamination and durability problems. Socket manufacturer Yamichi has applied a coating technology to help solve contactor problems with contamination and durability. Their proprietary Conductive Super-Hard (CSH) coating is based on diamond-like carbon technology. The material is conductive and helps mitigate surface contact contamination with intermetallic compounds.
Wednesday, October 21, 2009
Jabil, Flextronics Implement P. KAY Metal MS2 for Dross Elimination
CircuiTree: A number of major production facilities in Mexico, including Jabil and Flextronics, have joined the growing list of contract manufactures and OEMS to implement dross elimination technology from P. KAY Metal.
Larry Kay, president of P. KAY, said, "We are very excited that two of the leading contract manufactures in the world have now Implemented MS2 as the best available technology for eliminating Tons of wasted solder generated by the wave solder operation."
Facilities that have implemented the MS2 process are enjoying a major reduction in solder bar purchases ranging from 70-90percent. In addition to the industries commitment to waste reduction, MS2 customers are reporting a significant improvement in overall solder joint quality.
Monday, October 19, 2009
Melting temperature depression of Sn-0.4Co-0.7Cu lead-free solder nanoparticles
Scopus: "The purpose of this paper is to study the melting temperature of the nanoparticles of the new developed Sn-0.4Co-0.7Cu (wt%) lead-free solder alloy.
Design/methodology/approach: Nanoparticles of Sn-0.4Co-0.7Cu lead-free solder alloy were prepared by the self-developed consumableelectrode direct current arc technique, where ultrasonic vibration was applied during the manufacturing of the particles. X-ray diffraction and field emission scanning electron microscope were employed to analyze the crystal structure and morphology of the nanopartiles, respectively. Differential scanning calorimetry was used to investigate the melting temperature of both the bulk alloy and as-prepared nanoparticles. Findings: The melting temperature of the nanoparticles was approximately 5'C lower compared to that of the bulk alloy.
Originality/value: As a novel developed lead-free solder alloy, the Sn-0.4Co-0.7Cu (wt%) alloy provides a cost advantage compared to the extensively used Sn-Ag-Cu system. Some limitations still exist, however, mainly due to its relatively higher melting temperature compared to that of eutectic Sn-37Pb solder"
Shanghai University, China
Chalmers University, Sweden
Comparison of Interfacial Stability of Pb-Free Solders (Sn-3.5Ag, Sn-3.5Ag-0.7Cu,
Scopus: "The solid-state interfacial reactions of Pb-free solders (Sn-3.5Ag, Sn-3.5Ag-0.7Cu, and Sn-0.7Cu) with electroless nickel-immersion gold (ENIG)-plated Cu substrate, and the growth of interfacial intermetallic compound (IMC) layers were investigated and compared during aging at 200 'C for up to 1000 h.
The Sn-3.5Ag-0.7Cu solder exhibited a higher IMC growth rate and a higher consumption rate of the Ni(P) layer than the other two Pb-free solders. The interfacial reaction of the Sn-0.7Cu/ENIG-plated Cu system during aging was the slowest among the three kinds of solder joint. The thickness of the interfacial IMCs were ranked in the order Sn-3.5Ag-0.7Cu\,$>$\,Sn-3.5Ag\,$>$\,Sn-0.7Cu.
The higher melting temperature of the Sn-0.7Cu solder and the presence of Cu element within the solder suppressed the growth of the interfacial IMC layer and the consumption of the Ni(P) layer, resulting in the superior interfacial stability of the solder joint at high temperature of 200 'C."
Yoon, J.-W., Noh, B.-I., Jung, S.-B.
IEEE Transactions on Components and Packaging Technologies
22 September 2009
Article in Press
Physical Properties of Sn96.5Ag3.5-Based Solders with Additions of Bi, Ge, and In
Scopus: "The melting temperature, electrical resistivity, surface tension, and density of the (Sn0.965Ag0.035)95.17Bi4.83, (Sn0.965Ag0.035)95.17Bi4.73Ge0.1, and (Sn0.965Ag0.035)94-Bi2In4 alloys have been studied in comparison with the Sn60Pb40 and Sn96.5Ag3.5 binary alloys (all wt.%).
The electrical conductivity of the solid alloys based on Sn96.5Ag3.5 is comparable to that of the Sn60Pb40 alloy. The wetting behavior on Cu and Ni surfaces has been investigated in a wide temperature interval. It is established that the addition of Bi to Sn96.5Ag3.5 decreases the surface tension and improves the wetting properties of the alloy.
The addition of a small quantity of Ge to the Sn-Ag-Bi alloy did not improve the wetting behavior on either Cu or Ni surfaces. The wetting ability of the (Sn0.965Ag0.035)94Bi2In4 alloy was slightly worse as compared with (Sn0.965Ag0.035)95.17Bi4.83"
Molex Solder Charge
Molex webpage: Molex's innovative and patented Solder Charge™ SMT Technology for printed circuit board (PCB) adhesion provides precision to one ten-thousandth of an inch through the use of stamping equipmentSolder Charge SMT Technology optimizes the density benefits of a ball grid array (BGA) tail plus improves on BGA processing and manufacturing with connections that are more uniform and exact. The innovative technology provides a stronger and more reliable PCB interface at a lower cost. Molex's patented Solder Charge SMT Technology provides precision to one ten-thousandth of an inch and compensates for variation in PCB flatness through an engulfment of the terminal with maximum surface area on the solder pad. In contrast, the BGA solder method uses manual placement of heated metal alloys to adhere to the bottom of a connector and post reflow has the widest point of solder above the solder pad rather than on the pad itself. Molex's solder-charge technology uses standard reflow processes and offers a reflow profile for every connector utilizing this process.
Ni-based Conductive Electrical Adhesive
Factiva: "Cotronics Corp.Duralco 122 nickel-filled adhesive and casting epoxy is formulated to provide an alternative to silver-filled, electrically conductive epoxies. It is suitable for flexible circuit manufacture and repair, solder replacement, semiconductor bonding, EMI shielding, thermistors, wire tacking, heating elements, assembling, electronics, etc. The two-part epoxy is mixed by hand and cures at room temperature in 16–24 hrs at 75'F, or can be fast-cured in 10 min. at 200'F. It is resistant to moisture, chemicals and solvents."
Effects of nano-structured particles on microstructure and microhardness of Sn-Ag sol
Scopus: "In this research, the typical nano-structured Polyhedral Oligomeric Silsesquioxane (POSS) particles were incorporated into the Sn-3.5Ag eutectic solder paste by mechanically mixing to form lead-free composite solder. The effects of nano-structured POSS additions on the microstructure and mechanical properties of as-fabricated composite solder alloys were systematically investigated.
Experimental results indicated that the average size and spacing distance of Ag3Sn intermetallic compounds (IMCs) in composite solder matrix decreased as compared to the Sn-3.5Ag eutectic solder. The 3wt% addition of nano-structured POSS particles could enhance the microhardness of composite solder by 18.4% compared with the Sn-3.5Ag eutectic solder matrix."
The average grain size and spacing distance of Ag3Sn IMCs in Sn-Ag + 3 wt% POSS composite solder matrix reduced from 0.35 to 0.23 μm and from 0.54 to 0.32 μm, respectively. The refined Ag3Sn IMCs, acting as a strengthening phase in the solder matrix, could enhance the microhardness of the composite solders
Beijing University, China
Thursday, October 1, 2009
RE additions cause whiskers
Scopus "The phenomenon of rare earth (RE) additions inducing whisker growth in Sn-0.7Cu-Nd (0.1-5wt.%Nd) solder is reported.
The results showed that Nd exists as Sn3Nd in the microstructure of the solder alloys. A snowflake-like Sn3Nd was observed when Nd≤0.5wt.%. After exposure to ambient conditions, the Nd-bearing alloys have a strong tendency toward whisker growth, with a short incubation time for whisker nucleation (only several hours). All whiskers originated from the Sn-Nd compound, where whiskers grew relatively fast; the average growth rate of the five longest whiskers was approximately 4/s, and a 190μm whisker was observed within 480h.
Based on these results, it was predicted that whisker growth would be inevitable for all RE-bearing solders. The cause of this phenomenon is also discussed. Finally, the authors suggest that any solders doped with RE should be carefully considered again"
Institute of Metal Research, Shenyang, China
The effect of Cu and Ni on the structure and properties of the IMC formed by the reaction of liquid Sn-Cu based solders wit
Scopus: "The influence of Cu and Ni additions on the morphology of the intermetallic compounds (IMC) formed at the interface of the liquid Sn-Cu solder and the Cu substrate has been studied. At low Cu concentrations only a thin IMC layer is formed which remains almost unchanged in time and the substrate is dissolving quickly. Ni additions significantly accelerate the growth kinetics of the IMC layer, prevent the formation of a Cu3 Sn layer and reduce the rate of substrate dissolution."
Electromigration behaviors in Sb particle-reinforced composite eutectic SnAgCu solder joints
Scopus: "In order to conquer the instable physical properties of e-SAC in the severe service environment, composite approach was developed. One of the promising ways was intentionally incorporated metal-particles reinforcements. In this study, the e-SAC with 1 wt% Sb particles additive was investigated under the current density of 10 4 A/cm2 and 120'C the ambient temperature. Unlike the non-composite solders that had obvious formation of hillock and valley at the anode side and cathode side, respectively. The crack initiated at the edge of the cathode interface and propagated to the center in the Sb particle-reinforced composite solder. The Sn-Sb phase, formed near the cathode interface after the first-reflow, blocked the movement of metal atoms/ions, but then induced the current crowding. In addition, synergistic influence of the compressive and tensile stress caused the fracturing of the Sn-Sb phase in the solder matrix due to its brittleness and immobility."
Why they grow? Getting to the roots of lethal metal whiskers
Physorg.com: "A team of scientists from the Max Planck Institute for Metals Research has been working with Robert Bosch GmbH to measure the forces that trigger this metallic hair growth. Tin whiskers can be up to a few millimetres long and just a few micrometres in diameter. They sprout from the tin used to solder and plate electronic components made of copper. Understanding in detail what makes the whiskers grow is the first step on the way to preventing their growth. (Applied Physics Letters, June 2009)
The systems in a NASA computer centre failed after new data storage had been installed; at least 18 short circuits occurred in the high-performance computers before technicians found the reason: the replacement of the storage devices dislodged metal whiskers from the base construction and their subsequent distribution via air circulation caused system failure by bridging the electrical circuits of the supercomputers.
Researchers working with Eric J. Mittemeijer at the Max Planck Institute for Metals Research together with colleagues from the Robert Bosch GmbH, Argonne National Laboratory in Illinois and Oak Ridge National Laboratory in Tennessee have revealed the forces that cause these whiskers to sprout from tin-plated copper"
The systems in a NASA computer centre failed after new data storage had been installed; at least 18 short circuits occurred in the high-performance computers before technicians found the reason: the replacement of the storage devices dislodged metal whiskers from the base construction and their subsequent distribution via air circulation caused system failure by bridging the electrical circuits of the supercomputers.
Researchers working with Eric J. Mittemeijer at the Max Planck Institute for Metals Research together with colleagues from the Robert Bosch GmbH, Argonne National Laboratory in Illinois and Oak Ridge National Laboratory in Tennessee have revealed the forces that cause these whiskers to sprout from tin-plated copper"
Characterization of the Effect of Shape Memory Alloy on Solder Joint Strength Through Modeling and Testing
Scopus: "The objective of this research is to investigate how shape memory alloy (SMA) applied in the under bump metallization (UBM) can affect solder joint reliability under thermal mechanical stress. Joint strength tests revealed the better strength of solder joints with SMA UBM after accelerated thermal cycling test. Finite element modeling as well as multilayer stress calculations revealed less strain accumulated in the solder and more stress concentrated in Si in the solder joint with SMA UBM. A mechanism by which the SMA accommodates most of the stress and strain caused by the mismatch of the thermal expansion coefficients was proposed to explain the reinforcement of the solder joint by the SMA UBM"
Wednesday, September 30, 2009
Evolutions of the interface and shear strength between SnAgCu-xNi solder and Cu substrate during isothermal
Scopus: "The interfacial evolution and shear strength of Sn3.8Ag0.7Cu-xNi composite solders on organic solderability preservative (OSP) finished pad were investigated at a temperature of 150 'C aging for 0-1000 h.
It was found that all aged joints exhibited a duplex intermetallic compounds (IMCs) structure; i.e. a layer of (CuNi)6Sn5 close to the solder and a layer of Cu3Sn adjacent to the Cu substrate. The growth of the Cu3Sn layer was suppressed significantly after Ni particles addition, and the scallop-shape IMC with the composition of (CuNi)6Sn5 could be examined at the interface of all solder joints."
Tianjin University, China
Motorola (China) Electronics Ltd., China
cUniversity of Wollongong, Australia
Balver Zinn to demonstrate new lead-free solder SN100C in Hamburg
EMSNow: "This eagerly anticipated development in the highly regarded SN100C solder range has a content of 100ppm (0.01%) of germanium (Ge). In the BALVER ZINN SN100C formulation, Ge plays the vital role of antioxidant, providing a preferential reaction with oxygen to protect the solder from the oxidation that 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 the familiar 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.
Balver Zinn SN100CS Solder should be used for the first fill and top-up of a solder pot. Balver Zinn also offers an additive, Desoxy RSN, to be used should the Ge level be found to have fallen substantially below 0.006%, in order to keep the Ge level up to 0.01%."
The greater content of germanium in the SN100CS Solder renders it especially suitable for applications without nitrogen. This new solder also offers all the familiar 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.
Balver Zinn SN100CS Solder should be used for the first fill and top-up of a solder pot. Balver Zinn also offers an additive, Desoxy RSN, to be used should the Ge level be found to have fallen substantially below 0.006%, in order to keep the Ge level up to 0.01%."
Nihon Superior's SN100C University research recognized
EMSNow: "At the University of Queensland's Industry Connect and Showcase Event on September 1, 2009, research titled 'Inhibition of Cracking in Lead-Free Solder Joints' was sponsored by Nihon Superior. 'The Influence of Ni Content on Cracking in IMC Reaction Layers between Sn-Cu-Ni Solders and Cu Substrates' was chosen by the Dean of the Faculty of Engineering, Architecture and Information Technology, Professor Graham Schaffer from the 40 or so projects on display as one of the best examples of a successful cooperation between the university and industry. This event, the first of its kind, was held in the grand hall of the historic 19th century Customs House overlooking the river in Queen"
Professor Schaffer made the point that the cooperation between the university and Nihon Superior had been mutually beneficial. The research had contributed significantly toward establishing the case for Nihon Superior's unique patented SN100C tin-copper-nickel-germanium alloy as the best option for the electronics industry as it moves to lead-free solder. For the university, the project opened opportunities in an important area of materials science in which it had not previously been active.
As an example of the breakthroughs that had been achieved in the project, Professor Schaffer highlighted the recent discovery by Dr. Kazuhiro Nogita, the Principal Research Fellow in charge of the project, of the stabilization by nickel of the intermetallic phase that effects solder joint reliability.
The identification by Mr. Tetsuro Nishimura, president of Nihon Superior, of the importance of nickel in lead-free solder formulation was the basis on which the company's successful global business was developed. However, not all aspects of the effect of this addition had been understood at the time the study of this alloy began at University of Queensland. Early work established the effect of the nickel addition on the solidification behavior of the SN100C alloy and work currently underway is elucidating the factors that affect the resistance of a solder joint to the impact loading that occurs when a portable device such as a mobile phone is accidentally dropped. This work is expected to further strengthen the position of SN100C in the increasingly competitive global market for lead-free solder.
SAC-RE Impact Studies
Factiva: "This study was concerned with the effect of thermal aging on the impact properties of solder joints. Three kinds of solders, conventional Sn-37Pb solder, Sn-3.8Ag-0.7Cu solder, and Sn-3.8Ag-0.7Cu doped with rare-earth (RE) elements, were selected to manufacture joint specimens for the Charpy impact test,' scientists in Beijing, People's Republic of China report."
For the Sn-3.8Ag-0.7Cu joints, with microstructure coarsening, crack propagation partly shifted towards the Sn/Cu6Sn5 interface. Compared with the 100 h aged joints, the area fraction of intergranular fracture of Sn grains on the Sn-3.8Ag-0.7Cu fracture surfaces was increased when the aging time was 1000 h. On the contrary, the fracture morphologies of Sn-3.8Ag-0.7Cu-RE were mainly brittle as thermal aging increased
Zheijiang Met Res Inst patent SnSbCuXhigh temperature solder
WO2009111932A1: "A lead-free high-temperature electronic solder comprises, by mass, 8 to 22% Sb, 0.5 to 8% Cu and the balance Sn; 8 to 22% Sb, 0.5 to 8% Cu, 0.01 to 2% Ni and the balance Sn; or 8 to 22% Sb, 0.5 to 8% Cu, 0.01 to 2% Ni, 0 to 0.01% at least one of Ga, P, or mixed rare earth and the balance Sn. The melting point of the solder is 240 to 320? and the tensile strength is 58 to 84Mpa.
The preparing method of solder comprises keeping mixed each alloy element at 700 to 750? for 1 to 2 hours using vacuum smelting furnace or anti-vacuum smelting furnace, mixing them before being discharged from the furnace, then pouring, and solidifying. The solder is prepared to be at least one of solder mother alloy, solder block, welding stick, welding ball, welding ring, welding foil, welding powder, or welding paste. The solder has high melting temperature, good oxidation resistance and excellent humidification performance characteristics."
Nihon expands Chinese capacity
Factiva: "Nihon Superior Co. is expanding Chinese production of solder for home appliances in response to a surge in local demand as Chinese output by Japanese appliance manufacturers rebounds.
The solder manufacturer is relocating a Chinese production subsidiary's plant from Suzhou, Jiangsu Province, to a new facility 50km to the west that could be put into service this November. The new plant, which cost some 80 million yen, has a monthly capacity of 50 tons -- five times that of the old plant. It will supply solder to Japanese appliance manufacturers with plants in and around Shanghai.
Accompanying the expansion, workers at the plant will be tripled to 60.
By increasing local supply capacity and reducing shipping costs, Nihon Superior aims to create operations capable of responding promptly to customers' orders. It hopes to increase Chinese sales to around 5 billion yen in the year ending April 2013 from 1.7 billion yen in the year ended this past Apr"
The solder manufacturer is relocating a Chinese production subsidiary's plant from Suzhou, Jiangsu Province, to a new facility 50km to the west that could be put into service this November. The new plant, which cost some 80 million yen, has a monthly capacity of 50 tons -- five times that of the old plant. It will supply solder to Japanese appliance manufacturers with plants in and around Shanghai.
Accompanying the expansion, workers at the plant will be tripled to 60.
By increasing local supply capacity and reducing shipping costs, Nihon Superior aims to create operations capable of responding promptly to customers' orders. It hopes to increase Chinese sales to around 5 billion yen in the year ending April 2013 from 1.7 billion yen in the year ended this past Apr"
SAC-Mn effect on microstructure
Factiva: "The researchers concluded: 'The presence of Mn in the solder alloy is responsible for the difference in microstructure of the Sn-Ag-Cu-Mn solder alloy vs Cu assembly in the reflowed condition, which in turn influences the microstructure of the same after aging with respect to others.'
Ghosh and colleagues published their study in Metallurgical and Materials Transactions a - Physical Metallurgy and Materials Science (Aging Characteristics of Sn-Ag Eutectic Solder Alloy with the Addition of Cu, In, and Mn. Metallurgical and Materials Transactions a - Physical Metallurgy and Materials Science, 2009;40A(10):2369-2376)."
Ghosh and colleagues published their study in Metallurgical and Materials Transactions a - Physical Metallurgy and Materials Science (Aging Characteristics of Sn-Ag Eutectic Solder Alloy with the Addition of Cu, In, and Mn. Metallurgical and Materials Transactions a - Physical Metallurgy and Materials Science, 2009;40A(10):2369-2376)."
Method of copper precipitation in lead-free solder
US7591873: "The purpose of the present invention is to separate excess coppers leached out in a lead-free solder bath and recover tin with high efficiency. An element X for forming a (CuX)6Sn5 compound between copper and tin in molten lead-free solders is added to separate out a (CuX)6Sn5 compound.
Tin is recovered by binding the (CuX)6Sn5 compound by passing thereof through a multi-perforated plate, further generating swirling currents to precipitate and separate the bound (CuX)6Sn5 compounds and removing thereof."
Nihon Superior
Indium buys nanomaterials firm Reactive NanoTechnologies
Small Times: "Indium Corp. has acquired processes, equipment, and 'know-how' of nanomaterial developer Reactive NanoTechnologies for an undisclosed sum. Process, equipment, and staff will be moved to Indium's Utica, NY, facility, with the core team continuing to support the firm's NanoFoil and NanoBond businesses.
'Indium's presence in the global electronics materials market will allow NanoBond technology to proliferate more quickly and broadly,' said Joe Grzyb, RNT's CEO, in a statement. He added that there is 'strong synergy' with Indium's solder, assembly, and thermal interface materials.
For Indium, the addition will bolster its position in supplying materials for sputtering targets and metallic interfaces, noted Ross Berntson, Indium's VP of sales, marketing, and technical support.
The news follows one week after RNT licensed its NanoFoil and NanoBond technologies to Taiwan's Solar Applied Material Technology Corp. (Solartech), to bond sputtering targets using RNT's room-temperature bonding technique."
'Indium's presence in the global electronics materials market will allow NanoBond technology to proliferate more quickly and broadly,' said Joe Grzyb, RNT's CEO, in a statement. He added that there is 'strong synergy' with Indium's solder, assembly, and thermal interface materials.
For Indium, the addition will bolster its position in supplying materials for sputtering targets and metallic interfaces, noted Ross Berntson, Indium's VP of sales, marketing, and technical support.
The news follows one week after RNT licensed its NanoFoil and NanoBond technologies to Taiwan's Solar Applied Material Technology Corp. (Solartech), to bond sputtering targets using RNT's room-temperature bonding technique."
Managing the solder alloy explosion
EMSNow: "But in the short term, the boom in solder options is causing a lot of headaches throughout the broad electronics industry. One of them is that there's not a huge base of knowledge for the new solders. For example, the alloys that provide drop-shock resistance needed in handhelds may not fare well when put into servers or PCs that run at higher temperatures than cell phones. Solder fatigue may be an issue."
"IPC, HP and iNEMI are trying to put together standard test methods and to build a knowledge base around these materials so people can take advantage of the benefits the new alloys provide while avoiding unintended negative consequences," said Henshall, who serves as co-chairman for iNEMI's Lead Free Alloy Characterization project.
He noted that most of the low silver solders perform well in drop-shock reliability tests. Using solder with less of this precious metal in wave soldering also can have a tangible financial impact for assemblers. However, there's not much knowledge on whether these cost savings will pay off for OEMs and end customers.
Other problems arise when chipmakers change solder, for example moving to low-silver alloys to trim costs. That can cause major problems upstream. For example, one chipmaker switched to low silver solder balls for a BGA line. Reducing silver increases the melting temperature, which caused a problem for a system maker whose processes were at the low end of the accepted window for the earlier version with higher silver solder balls.
"The parts were the same, but the component manufacturer went from SAC 305 to a low silver alloy without changing part number, so the board assembler didn't know anything had changed. They started getting poorly formed joints that decreased production yield. An even greater concern is that poorly formed joints could pass functional tests but start to fail once they get into the field," Henshall said.
Even if component makers say they're switching solders, OEMs currently don't have enough knowledge to know whether the change will have an impact on quality and reliability. That's because the industry has not yet built up a knowledge base that addresses broad attributes such as solder fatigue.
Henshall will be discussing the many issues tied to the plethora of lead-free alloys during the IPC Materials Conference: Engineering for Compliance in Irvine, Calif. Ron Lasky of Indium and Jean-Paul Clech of EPSI will address different aspects of the issue during a 90-minute session on Nov. 11.
He'll also be describing some of the efforts to provide more insight. iNEMI is working to gather data on many of the alloys and is also teaming with the Solder Products Value Council and IPC to develop standards for alloy testing.
Development of lead-free nanocomposite solders using oxide ba
Scopus: "In this study, Sn.3.5Ag/SnO2 nanocomposite solders are developed. Composites with 0.7 and 1.0 volume percentage of tin oxide were synthesized through powder metallurgy route incorporating microwave assisted rapid sintering technique followed by hot extrusion. The extruded specimens were examined in terms of their physical and tensile properties. Tensile characterization studies revealed that 0.2% yield strength and ultimate tensile strength were increased significantly by addition of 0.7 volume percent of nano SnO2 particles. An attempt is made to correlate mechanical properties of Sn-3.5Ag with the presence of SnO2 particles at the nanometer length scale."
Effect of nano-size oxide based reinforcement on the tensile
Scopus: "In the present study, using powder metallurgy route, varying volume fraction of ZrO2 stabilized with 8 mol.% of Y2O 3 particulates were incorporated into Sn-3.5Ag-0.7Cu solder to develop nanocomposite solders.
The samples were extruded and characterized in terms of microstructural and tensile properties. With the addition of nano length scale reinforcement, the results revealed an improvement in 0.2% yield strength (upto ∼ 39%) and ultimate tensile strength (upto ∼ 43%), when compared with that of monolithic Sn-Ag-Cu solder. An attempt is made in this study to interrelate the tensile behavior of Sn-Ag-Cu with the presence of nano-size reinforcement."
Nanoparticles of SnAgCu lead-free solder alloy with an equivalent melting temperature of SnPb solder alloy
Scopus: "Nanoparticles were prepared with a consumable-electrode direct current arc (CDCA) technique. The results showed that the calorimetric melting onset temperature of the nanoparticles of SnAgCu solder alloy could be as low as 179'C, equivalent to that of the traditionally used SnPb eutectic alloy (183'C).
Moreover, the homogenous melting model (HMM) and Gibbs-Thomson equation were employed to theoretically estimate the size-dependent melting temperature of the as-prepared nanoparticles. The structure and morphology of the nanoparticles were analyzed with a high-resolution transmission electron microscopy (HRTEM). The CDCA technique showed promising prospect in manufacturing large amounts of nanoparticles with controlled shape, small size, narrow particle size distribution and nearly oxide-free composition.
This undoubtedly puts forward a novel feasible approach to manufacture high quality lead-free solders for electronic products"
Effects of sulfide-forming element additions on the Kirkendall void formation and drop impact reliability of Cu/Sn-3.5Ag sol
Scopus: "Ternary Pb-free solders, Sn-3.5Ag-X, containing 0.5 wt.% of Zn, Mn and Cr, were reacted with Cu UBM, which was electroplated using SPS additive.
Characteristics of Cu-Sn IMCs and Kirkendall void formation at the Cu/Sn-3.5Ag solder joints were significantly affected by the third element, and the potency to suppress Kirkendall voids at the solder joint increased in the order of Cr, Mn, Zn, which was indeed the order of the drop reliability improvement.
From the AES analyses, it was suggested that the sulfide-forming elements in the solder diffused into the Cu UBM and reduced the segregation of S atoms to the Cu/Cu3Sn interface by scavenging S, which led to the suppression of Kirkendall void nucleation at the Cu/Cu3Sn interface and the drop reliability improvement. In the case of the Zn-containing solder joint, Cu3Sn phase, known to be a host of Kirkendall voids, did not form at all even after extended aging treatments. The magnitude of the tensile stress at the Cu3Sn/Cu interface which drove the Kirkendall void growth was estimated to be 10-100 MPa"
Monday, September 21, 2009
TEERM NASA Lead-Free Electronics - Project 2
TEERM NASA Lead-Free Electronics - Project 2: "TEERM Active Project
NASA-DOD Lead-Free Electronics (Project 2)
Project Number: NT.1504
POC: Kurt Kessel, (321-867-8480) kurt.r.kessel@nasa.gov
Greg Krivdo, (321-867-0492) Gregory.T.Krivdo@nasa.gov
Background
NASA’s earlier lead-free solder high-reliability testing effort helped shed light on the reliability of circuit cards manufactured with lead-free solders. However, that project was not able to fully explore rework and solder mixing. As the transition to lead-free becomes an ever-closer reality for military and aerospace applications, it will be critical to fully understand the implications of rework and solder mixing.
This joint project of DoD, NASA and defense and space contractor representatives will build on the results from the former NASA-led lead-free solder project. The new effort will focus on the rework of tin-lead and lead-free solder alloys and will include the mixing of tin-lead /lead-free & lead-free/ tin-lead solder alloys."
NASA-DOD Lead-Free Electronics (Project 2)
Project Number: NT.1504
POC: Kurt Kessel, (321-867-8480) kurt.r.kessel@nasa.gov
Greg Krivdo, (321-867-0492) Gregory.T.Krivdo@nasa.gov
Background
NASA’s earlier lead-free solder high-reliability testing effort helped shed light on the reliability of circuit cards manufactured with lead-free solders. However, that project was not able to fully explore rework and solder mixing. As the transition to lead-free becomes an ever-closer reality for military and aerospace applications, it will be critical to fully understand the implications of rework and solder mixing.
This joint project of DoD, NASA and defense and space contractor representatives will build on the results from the former NASA-led lead-free solder project. The new effort will focus on the rework of tin-lead and lead-free solder alloys and will include the mixing of tin-lead /lead-free & lead-free/ tin-lead solder alloys."
Higher Prices and More Failures Predicted for Defense Electronics
www.nationaldefensemagazine.org: "The Defense Department needs to fund additional research into how to deal with lead-free electronics, Hillman said.
The Pentagon’s Defense Microelectronics Activity — a small agency that reports to the office of the secretary of defense — has for years been developing and testing lead-free solders and assemblies for military systems. But these projects are still in the experimental stage. One industry source says that DMEA tests showed that the lead-free assemblies performed poorly compared to the tin-lead solder used in military systems."
The Pentagon’s Defense Microelectronics Activity — a small agency that reports to the office of the secretary of defense — has for years been developing and testing lead-free solders and assemblies for military systems. But these projects are still in the experimental stage. One industry source says that DMEA tests showed that the lead-free assemblies performed poorly compared to the tin-lead solder used in military systems."
Comment:
The present solder alloys are not sufficently reliable; that is a proven fact which industry/NASA studies
have clearly demonstrated. A vivid example is the following paper "NASA-DoD Lead-Free Electronics Project June 24, 2009"
which is part of this effort: http://www.teerm.nasa.gov/projects/NASA_DODLeadFreeElectronics_Proj2.html
Robert J. Landman
Thursday, September 10, 2009
Solder-free Connectors Using Buckled Pillars
ElectroIQ: "A novel use of stud bumping equipment has enabled the development of buckled pillar connectors for 3D assemblies that are put together with screws rather than solder. While still in development stages, the process is targeting high-powered systems such as servers and routers for aerospace applications.
Aparticularly versatile form of wafer bumping is stud bumping, using either gold or copper wire.1 The equipment required is an adaptation of a traditional wire bonder. A ball bond is made at a first contact pad using heat and ultrasonic energy. The wire is extended in a precise direction and a flying lead is created by terminating the wire, for example using electronic flame-off (EFO). This type of stud bump can be used as a buckled pillar connector, enabling electronic assemblies that are put together with screws rather than solder. With appropriate assembly and testing techniques, this can lead to waste-free integrated assemblies; no good parts are thrown away due to compound yield problems, otherwise known as known good die (KGD) problems."
Aparticularly versatile form of wafer bumping is stud bumping, using either gold or copper wire.1 The equipment required is an adaptation of a traditional wire bonder. A ball bond is made at a first contact pad using heat and ultrasonic energy. The wire is extended in a precise direction and a flying lead is created by terminating the wire, for example using electronic flame-off (EFO). This type of stud bump can be used as a buckled pillar connector, enabling electronic assemblies that are put together with screws rather than solder. With appropriate assembly and testing techniques, this can lead to waste-free integrated assemblies; no good parts are thrown away due to compound yield problems, otherwise known as known good die (KGD) problems."
Salmon Technologies Inc
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."
Influence of lanthanum additions on the microstructure and microhardness of sn-3.5Ag solder
Scopus: "This study evaluates the effects of different amounts of lanthanum (La) additions on the microstructure and microhardness of Sn-3.5Ag solders. Sn-3.5Ag-xLa ternary solders were prepared by adding 0 wt.% to 1.0 wt.% La to Sn-3.5Ag alloy.
Copper substrates were then dipped in the molten solders and these samples aged at 150'C for up to 625 h. The microstructure and microhardness of the as-solidified solder and the aged solder/copper samples were investigated. The Sn-3.5Ag-xLa solders comprised β-Sn, Ag 3Sn, and LaSn3 phases, and their microstructure was refined by La additions. 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."
Auto OEMs Complete Pb-Free Solder Validation Test Plan
Circuits Assembly: "A project team made up of Chrysler, Ford and General Motors has developed a process to help automotive suppliers remove lead-based solder from electronics components used in vehicles.
Under the auspices of the United States Council for Automotive Research, and in concert with the Vehicle Recycling Partnership LLC, a Lead-Free Solder Validation Test Plan has been developed for suppliers of audio components, instrument clusters, engine controls and other electronics components to use in meeting the requirements for all products manufactured by Chrysler, Ford and GM.
Goals include reducing costs and speeding time-to-market, and meeting the European End-of-Life Vehicle directive requiring the elimination of leaded solder in all electronic components beginning January 2011.
Representatives from TRW and Lear Corp. joined the VRP Lead-Free Solder Validation Team, which began work in April 2008. Among the challenges was sorting through the hundreds of tests and validation processes each of the OEMs require suppliers to use.
“Taking lead out of a component essentially means it’s a new product,” said Jennifer Senish, member of the VRP Lead-Free Solder Validation Team and General Motors environmental/durability engineer. “There needs to be an entirely new set of tests, including chemical, thermal and fatigue evaluations to ensure the products are still robust.”"
Under the auspices of the United States Council for Automotive Research, and in concert with the Vehicle Recycling Partnership LLC, a Lead-Free Solder Validation Test Plan has been developed for suppliers of audio components, instrument clusters, engine controls and other electronics components to use in meeting the requirements for all products manufactured by Chrysler, Ford and GM.
Goals include reducing costs and speeding time-to-market, and meeting the European End-of-Life Vehicle directive requiring the elimination of leaded solder in all electronic components beginning January 2011.
Representatives from TRW and Lear Corp. joined the VRP Lead-Free Solder Validation Team, which began work in April 2008. Among the challenges was sorting through the hundreds of tests and validation processes each of the OEMs require suppliers to use.
“Taking lead out of a component essentially means it’s a new product,” said Jennifer Senish, member of the VRP Lead-Free Solder Validation Team and General Motors environmental/durability engineer. “There needs to be an entirely new set of tests, including chemical, thermal and fatigue evaluations to ensure the products are still robust.”"
iNEMI Roadmap: R&D in Printing, Dispense
electroiq.com: "As PCBs become more complex, the challenges for printing and dispensing technologies grow. Miniaturization, functional densification, and integration are driving 01005, 0201, finer pitch (0.3-0.4 mm) QFPs and SMT connectors, finer pitch (0.3-0.4mm) CSPs, flip chips and chip on board (COB) usage, as well as tighter spacing (<10 mil) between components. The increase in frequency and in the range of component sizes assembled on a single board adds to these hurdles. The widening range of required paste volumes deposited on mixed-technology assemblies is pushing traditional stencil design rules to their limit. Further, there is a need for stencil, printing, and materials technologies advances to increase deposit consistency.
These changes require greater accuracy and control with stencil printing and new dispensing and patterning capabilities, especially when non-planar surfaces are introduced. This is an area to focus R&D efforts to ensure that SMT materials, processes, and equipment keep pace with the ever-increasing complexity in PCBs."
These changes require greater accuracy and control with stencil printing and new dispensing and patterning capabilities, especially when non-planar surfaces are introduced. This is an area to focus R&D efforts to ensure that SMT materials, processes, and equipment keep pace with the ever-increasing complexity in PCBs."
Effects of small amounts of Ni/P/Ce element additions on the microstructure and prope
Scopus: "The purpose of this study is to investigate the effects of small amounts of Ni, P and Ce element additions on the microstructure and properties of Sn3.0Ag0.5Cu solder alloy.
The results indicate that adding trace amounts of Ni, P or Ce element has little influence on the melting temperature of Sn3.0Ag0.5Cu solder alloy. Adding Ni or Ce element cannot improve the wettability and anti-oxidization of the Sn3.0Ag0.5Cu solder alloy, but it can depress the interfacial intermetallic compounds growth due to the high temperature aging and then improves the shear strength of the solder joint."
In addition, the P element addition not only significantly increases the maximum wetting force and decreases the wetting time of the solder, but also improves the anti-oxidation property of the Sn3.0Ag0.5Cu solder. At the same time, adding P element also increases the hot cracking sensitivity of the solder surface in the solidification. However, it is noted that adding Ni or Ce element can depress the formation of the hot carking. The reason may be related to the modification of the microstructure of the solder alloys due to trace amounts of Ce or Ni elements additions. The adding elements change the microstructure of Sn3.0Ag0.5Cu solder alloy
Beijing University of Technology, China
Research of new Sn-Ag based lead-free composite solders containing nano-structured reinfo
Scopus: "Composite solders were fabricated by mechanically mixing the Sn-3.5Ag solder paste with nano-scale of 1% (mass fraction), 2% and 3% polyhedral oligomeric silsesquioxanes (POSS) particles.
POSS microstructure, melting characteristic, wetting property and shear strength were investigated. The results showed that the POSS particle didn't change the melting temperature of composite solders. Addition of POSS in the Sn-3.5Ag solder increased the spreading area and decreased the contact angle of lead-free composite solder. Shear strength of POSS particle reinforced composite solder joints were improved remarkably."
Beijing University of Technology, China
Reliability challenges of automotive power electronics
Scopus: "A high reliability of power electronic modules is an essential requirement for hybrid traction applications. This includes a high capability to withstand the stress of repeated active and passive thermal cycles in order to meet the lifetime requirements. Active power cycling requirements are not especially severe for hybrid traction applications compared to many industrial applications. The lifetime for passive thermal cycles by a change of ambient conditions in contrast is defined by the materials and the architecture of a power module. The classical module design with Cu base plates is limited in lifetime particularly with respect to passive temperature cycles due to CTE mismatch. The advanced pressure contact design eliminates the base plate together with the base plate solder and the terminal solder interconnections and thus enhances the thermal cycling capability. As a synergy effect, this design establishes a very balanced static and transient current distribution for paralleled chips. Finally, the last remaining solder interface - the chip solder layer - can be replaced by an Ag diffusion sinter technology. The presented cycling test results will confirm, that the first 100% solder-free module shows an improved performance in passive and active cycling tests"
A novel accelerated test technique for assessment of mechanical reliability of solder interconnects
Scopus: "The conventional reliability testing procedures are reported to be expensive and time consuming. Thus alternative tests and evaluation methods for reliability assessment of solder joints are required. 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"
Simultaneous Lead and Lead-free Soldering with a Single Reflow System
electroiq.com: "SnPb and lead-free PCBs can be soldered simultaneously without investing significantly in duplicate reflow ovens, oven changeover, or segmented reflow soldering systems. The different reflow profiles required are achieved solely through the use of different conveyor speeds for two parallel lanes. The temperature settings for the heating and cooling modules are identical, because the modules span both conveyor lanes in a homogenous fashion. There are not any additional technical fixtures, such as separate nozzle sheets or gas deflector plates, that would influence heat transfer at the two sides of the system. This increases ease of use for the operator, and keeps investment costs down."
Properties of SnAgCu/SnAgCuCe soldered joints for electronic packaging
Scopus "For quad flat packages (QFP256), lead-free soldered joints reliability in service is a critical issue. In this paper, soldering experiments of quad flat package (QFP256) devices were carried out by means of infrared reflow soldering system with Sn-3.8Ag-0.7Cu and Sn-3.8Ag-0.7Cu-0.03Ce lead-free solders, respectively, and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR micro-joints tester.
The results indicate that the tensile strength of Sn-Ag-Cu-Ce soldered joints is better than that of Sn-Ag-Cu soldered joints. In particular, the addition of trace Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the intermetallic compound layer of Sn-Ag-Cu solder alloys.
In addition, the stress-strain response of Sn-Ag-Cu/Sn-Ag-Cu-Ce soldered joints in quad flat packaging was investigated using finite element method based on Garofalo-Arrhenius model. The simulated results indicate creep distribution of soldered joints is not uniform, the heel and toe of soldered joints, the area between soldered joints and leads are the creep concentrated sites. The creep strain of Sn-Ag-Cu-Ce soldered joints is lower than that of Sn-Ag-Cu soldered joints."
Nanjing University of Aeronautics and Astronautics, China
Harbin Welding Institute, Harbin, China
China Electronics Technology Group Corporation, Nanjing, China
Effects of Nano-TiO2 additions on thermal analysis, microstructure and tensile properties of Sn3.5Ag0.25Cu solder
Scopus: "For development of a lead-free composite solder for advance electrical components, a series of Sn3.5Ag0.25Cu (SAC) solders containing TiO2 nanopowders have been studied."
The results showed that the addition of 0.25-1 wt.% TiO2 nanopowders into the lead-free SAC solder caused its liquidus temperature to increase by about 3.5-5.9 °C. Metallographic observations of the lead-free SAC composite solders revealed a reduction in the grain size of β-Sn, Ag3Sn phase and Ag3Sn phase located between the spacing lamellae. In terms of mechanical behavior, the addition of larger weight fractions of TiO2 nanopowders in lead-free SAC solder matrix led to an improvement in microhardness, 0.2%YS and UTS. However, ductility of the lead-free SAC composite solders was observed to decrease
National Pingtung University of Science and Technology, Taiwan
National Yunlin University of Science and Technology, Taiwan
Monday, September 7, 2009
SMTA connecting to members with Social Media
EMSNow: "The Surface Mount Technology Association (SMTA) has established itself on several of the most well-known social media sites in an effort to connect with members and broaden its outreach in the electronics assembly industry. Using Facebook, LinkedIn, Youtube, and most recently Twitter, the SMTA has discovered a more personal realm to network and share knowledge.
'We are really excited about the new level this kind of technology will add to our events and our membership,' commented Tom Forsythe, Kyzen Corporation and SMTA Vice President of Communications."
'We are really excited about the new level this kind of technology will add to our events and our membership,' commented Tom Forsythe, Kyzen Corporation and SMTA Vice President of Communications."
Friday, September 4, 2009
MEPTEC 2009, Medical Electronics Symposium
MEPTEC 2009:
Market data and trends
Solder trends
Tim Jensen, Indium Corporation
Second generation lead-free alloys
Randy Schueller, DfR Solutions
Thursday, September 3, 2009
Solder recovery from WEEE using copper smelting
Factiva: "In the view points of resource recycling and environment protection it is necessary to extract the valuable metals from waste electric and electronic scraps (WEES) which contain considerable amounts of valuable metals such as copper, tin, gold, and silver. In present work, a novel process to extract valuable metals such as copper and tin from WEES by smelting with the addition of waste copper slag as a slag formative has been developed.'
'The process uses only waste copper slag without using any additional flux components as slag formatives. In each set of experiment, crushed WEES were melted with waste copper slag for 30 min at 1623 K in air atmosphere,' wrote B.S. Kim and colleagues.
The researchers concluded: 'Based on proposed process flow-sheet, up to 90% of copper and 80% of tin contained in the raw materials were extracted as a Cu-Fe-Sn alloy phase at the input ratio of 50:50 of WEES and waste copper slag"
'The process uses only waste copper slag without using any additional flux components as slag formatives. In each set of experiment, crushed WEES were melted with waste copper slag for 30 min at 1623 K in air atmosphere,' wrote B.S. Kim and colleagues.
The researchers concluded: 'Based on proposed process flow-sheet, up to 90% of copper and 80% of tin contained in the raw materials were extracted as a Cu-Fe-Sn alloy phase at the input ratio of 50:50 of WEES and waste copper slag"
A Tin Pest Failure
Scopus: "This case study details a tin pest failure that occurred on plated electrical connectors exposed to low temperatures during storage. Analysis indicated that the bismuth additives specified to combat tin pest were not present in sufficient quantities, and the degradation suffered by the connectors was confirmed as tin pest.
New regulations (Restriction of Hazardous Substances Directive, ROHS) are limiting the use of common tin alloying elements that combat tin pest in electronic devices. The effects of this legislation with regard to tin pest are also discussed, indicating that frequency of failures from this phenomenon could increase"
Xbox 360 and PS3 Failures Explained
Console and PC Gaming News ::.: "The problems seem to be cumulative, perhaps explaining why we haven’t heard that much about PS3 failure – yet. A Google search for PS3 YLOD – while nowhere near the scale of a similar RROD search – does indicate an increasingly alarming problem.
The YLOD, contrary to popular belief, isn’t necessarily Blu-Ray drive failure – it’s the same thing that afflicts the 360; excessive heat causes the solder holding the GPU in place to flow, breaking its connection to the board. One of the leading factors in this is the lead-free solder that companies are now legally required to use in electronics manufacture. If there’s anyone to be blamed for your console failing, blame a hippy"
Combining Tin/Lead and Lead-free
SMT: "With the electronics industry movement to lead-free components, hybrid manufacturing may be a necessary solution if a non-RoHS assembly uses tin/lead solder and lead-free BGAs are being introduced to the assembly and process. Diligence and process controls are required to verify the acceptable case temperatures for all components on the BOM, reflow profile parameters, and appropriate alloy mixing. Additional testing and failure analysis (FA) is also recommended to verify the reliability of the design and overall assembly's technology."
Non RoHS lead solder reballing certification with optical inspection available from ISI
Military & Aerospace Electronics: "Interconnect Systems Inc. (ISI) in Camarillo, Calif., is offering a process of removing lead free solder spheres then attaching tin-lead (Sn63Pb37) eutectic lead solder spheres that has been qualified by commercial, industrial, military, and aerospace companies, ISI officials say.
This solder reballing process is in response to a wave of lead free parts that resulted from the European Restriction of Hazardous Substances (RoHS) directives that prohibited lead in solder. Many military applications still need lead solder electronics, cannot use RoHS compliant lead free packaging, and need a process to convert RoHS parts to lead solder parts."
This solder reballing process is in response to a wave of lead free parts that resulted from the European Restriction of Hazardous Substances (RoHS) directives that prohibited lead in solder. Many military applications still need lead solder electronics, cannot use RoHS compliant lead free packaging, and need a process to convert RoHS parts to lead solder parts."
Asia solder hopes on Q2 global demand
Oman Tribune: "Asian electronics makers are forecasting a turnaround in the second half of this year, citing a pick-up in global demand.
Several companies say the worst is over for a sector at the heart of emerging Asia’s battered, export-reliant economies — from Thailand to Singapore, Malaysia and Taiwan.
“I think the weakness in electronic component demand has hit bottom in the second quarter because new orders are now increasing,” Anusorn Muttaraid, director of Thailand’s Delta Electronics, said on Wednesday."
Several companies say the worst is over for a sector at the heart of emerging Asia’s battered, export-reliant economies — from Thailand to Singapore, Malaysia and Taiwan.
“I think the weakness in electronic component demand has hit bottom in the second quarter because new orders are now increasing,” Anusorn Muttaraid, director of Thailand’s Delta Electronics, said on Wednesday."
Dell on combined vibration and thermal cycling
Factiva: "While some electronic products are routinely subjected to concurrent vibration and temperature cycle loading, the ability to accurately model and estimate life expectancy of hardware under such conditions still presents a unique challenge.'
'For combined vibration and temperature cycling, one of the most likely causes of failure is the fatigue of solder interconnects. This paper presents an approach to predict solder joint life under combined thermal cycling and vibration loading conditions, by taking into account temperature effects and loading interactions,' wrote H.Y. Qi and colleagues, Dell Inc.
The researchers concluded: 'Combined loading experiment on a test vehicle populated with PBGA packages was used to demonstrate this approach."
'For combined vibration and temperature cycling, one of the most likely causes of failure is the fatigue of solder interconnects. This paper presents an approach to predict solder joint life under combined thermal cycling and vibration loading conditions, by taking into account temperature effects and loading interactions,' wrote H.Y. Qi and colleagues, Dell Inc.
The researchers concluded: 'Combined loading experiment on a test vehicle populated with PBGA packages was used to demonstrate this approach."
Effect of solder bump size on shear strength
Factiva: "The effect of wafer-level solder bump size on solder bump shear strength and intermetallic growth as a function of time, at different storage temperatures is studied, using solder bumps of two different heights: 95 mu m (SB95) and 142 mu m (SB142). Smaller solder bumps (SB95) lead to a faster decrease in bump shear strength"
ZnX intermetallics in InBiZn for CTE mismatch in die-attach
US7578966 "A solder composition includes a reflow-wetting element that is an intermetallic both pre-reflow and post-reflow. The intermetallic releases the reflow-wetting element upon heating. The solder composition includes the intermetallic first phase in a bulk-solder second phase. A method of assembling a microelectronic package includes the intermetallic in a solder. A computing system also includes the intermetallic first phase in the bulk-solder second phase.
1. A solder composition comprising:
a ZnX intermetallic first phase, wherein X is a metal selected from tin, gold, silver, copper, nickel, aluminum, and combinations thereof, and wherein the ZnX intermetallic phase is present in a concentration range from about 0.01% to about 1%; and the balance, a bulk solder second phase of InBiZn, and wherein Zn has the ability to be liberated from the ZnX intermetallic first phase in a temperature range from about 95C. to about 110 C."
1. A solder composition comprising:
a ZnX intermetallic first phase, wherein X is a metal selected from tin, gold, silver, copper, nickel, aluminum, and combinations thereof, and wherein the ZnX intermetallic phase is present in a concentration range from about 0.01% to about 1%; and the balance, a bulk solder second phase of InBiZn, and wherein Zn has the ability to be liberated from the ZnX intermetallic first phase in a temperature range from about 95C. to about 110 C."
Intel Corporation
COOH for non-conventional molten solder
WO2009104338A1: "This invention provides tin or a solder alloy, which has nonconventional properties, that is, has a very low viscosity in a melted state to realize good wet spreading properties, has excellent physical and mechanical properties, i.e., excellent flexibility, elongation and toughness, and can realize joining in which the reliability of joining at a joint by covering or joining using the tin or solder alloy is high, and an electronic component and a semiconductor device using the tin or solder alloy.
Conventional tin, tin-lead-base solder alloy, lead-free solder alloy, which are currently widely used, that is, a molten tin, or a molten solder alloy composed mainly of tin and containing any one or at least two of metals selected from lead, silver, copper, zinc, bismuth, antimony, nickel, and germanium is immersed in a solution containing 5 to 80% by weight of an organic compound containing at least a carbonyl group (-COOH), which is soluble in an oil-based solvent having a liquid temperature of 180˚C to 300˚C and has a stable molecular structure, followed by vigorous stirring to remove oxides and impurities present in the molten tin or the molten solder alloy"
Nippon Joint, Japan
Horizon Techonology, Japan
Nihon Superior patent on regulating Ni content using P
WO2009104271A1: "A method by which the amount of nickel contained in an alloy having a composition represented by Sn-X-Ni can be regulated. The method of nickel concentration regulation comprises adding phosphorus to Sn-X-Ni in a molten state (wherein X is one or more elements selected from the group consisting of Ag, Zn, Cu, Bi, Au, Ti, Ge, Ga, Si, and Ce), holding the mixture at 250-400C, and removing the resultant dross floating on the surface of the liquid phase and containing a P-Ni compound and a P-Sn-Ni compound.
An example of X is copper, and the content thereof may be 0.3-5 wt.%. The phosphorus may be added in the state of an Sn-P alloy. The upper limit of the amount of the phosphorus to be added may be about half the nickel amount in terms of atomic amount."
Kester to host Solder Alloy Task Group at IPC Midwest 2009
EMSNow: "Kester announces that David Scheiner will host a Solder Alloy Task Group at the upcoming IPC Midwest Conference. The meeting will be held during Session 5-24c of the Standards Development Meetings, scheduled to take place Tuesday, September 22, 2009 from 1:30-3 p.m.
The Task Group will be headed by David Scheiner of Kester and has completed modifying, via Amendments 1 and 2, revision C of J-STD-006, 'Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders for Electronic Soldering Applications'. It is continuing work on revising this document to its revision D."
The Task Group will be headed by David Scheiner of Kester and has completed modifying, via Amendments 1 and 2, revision C of J-STD-006, 'Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders for Electronic Soldering Applications'. It is continuing work on revising this document to its revision D."
Allen Lu named president of SEMI China
EMSNow: "SEMI announced the appointment of Allen Lu, Ph.D. as the president of SEMI China. Lu assumes responsibility for the association's programs, products and services in China. He will oversee relationships with SEMI members, government and academia in the region; support SEMI international programs; and serve SEMI members from all regions that have interests in China.
Lu succeeds Rong-Ling Chen, who has served as acting president of SEMI China since April 2009 and who will continue to serve SEMI as an advisor to Lu."
SMTA China names MW Associates as official PR agency for third year
EMSNow: "MW Associates, a global all-electronics marketing agency, announces that for the third year in a row it has been named SMTA China's official public relations agency. The marketing company's President Megan Wendling received this prestigious honor at the recent NEPCON South China exhibition and conference that took place in Shenzhen, China.
Megan and the MW Associates team have fully supported all events of SMTA China, actively promoted SMTA China conferences and solicited many sponsors to SMTA China for years."
Megan and the MW Associates team have fully supported all events of SMTA China, actively promoted SMTA China conferences and solicited many sponsors to SMTA China for years."
SMTA China presents seven best-paper awards at SMTA China South 2009 Conference
EMSNow: "SMTA China announces that it presented awards for seven papers at the SMTA China South 2009 Conference Award Presentation Ceremony, held on Thursday, August 27, 2009 at the Shenzhen Ritz-Carlton Hotel in conjunction with the SMTA Hong Kong Chapter Annual Breakfast Reception.
Flextronics' Jesus Tan was awarded The Best Paper of Technology Conference One for the paper titled 'Technical Evaluation for Pallet Material Selection.'
Shenzhen Kaifa Technology Co., Ltd.'s Zuyao Liu was awarded The Best Presentation of Technology Conference One for the presentation titled 'Influence of PBGA Thermo Warpage on Soldering Joints' Reliability.'"
Flextronics' Jesus Tan was awarded The Best Paper of Technology Conference One for the paper titled 'Technical Evaluation for Pallet Material Selection.'
Shenzhen Kaifa Technology Co., Ltd.'s Zuyao Liu was awarded The Best Presentation of Technology Conference One for the presentation titled 'Influence of PBGA Thermo Warpage on Soldering Joints' Reliability.'"
INEMI's Haley Fu was awarded The Best Paper of Technology Conference Two for the paper titled "iNEMI HFR-Free Program Introduction."
Martin Wen, from Indium Corporation's Shenzhen Rep Office, received the award for The Best Presentation of Technology Conference Two for the presentation titled "Addressing the Challenge of Head-in-Pillow Defects in Electronics Assembly."
Kyzen's Phil Zhang was awarded The Best Paper of Vendor Conference One for his paper titled "White Residue on Printed Wiring Boards Post Soldering/Cleaning."
Steve Glass, from RMD Instruments LLC, was awarded The Best Paper of Vendor Conference Two for his paper titled "Understanding XRF Technology and Clarification of its Application for Counterfeit Component Awareness and the RoHS Directive."
Nobe Yan, of ICHIMURA - Shenzhen Kunqixinhua Technology Co., Ltd., was awarded Best Paper of Vendor Conference Three for "The Hazards of Tin Oxide Slag and Its Solutions."
For more information about the SMTA China, contact Ms. Peggy Chen at +86-21-5609-3010; fax: +86-21-5609-3020; E-mail: peggy@smta.org.
Effect of particle size distributions on the rheology of Sn/Ag/Cu lead-free solder pastes
Scopus: "The dependence of viscosities on the particle size distribution of lead-free solder powders (Sn/Ag/Cu) is investigated using a parallel-plate rheometer. Experimental results show that for a fixed weight fraction of particles, as the increase of size ratios, the viscosities of the solder paste decrease especially at low shear rates. I
n addition, for solder paste with more small particles introduced, shear-thickening appears before the onset of shear thinning. The higher the relative fraction, the more dramatically viscosities increase, which is consistent with modeling results using Cross equation. A possible mechanism is proposed to reveal the relationship between microstructure and corresponding rheological behaviors."
Shanghai Jiao Tong University, China
Effect of fine dispersoids and anisotropic nature of β-Sn on thermal fatigue properties of fli
Scopus: "A significance of two factors, fine dispersoids in a solder and the anisotropic nature of b-Sn, on thermal fatigue endurance is discussed using flip chips connected by Sn-xAg0.5Cu (x: 1, 3 and 4 mass-%) lead free solders, together with Sn and Sn-12Ag-05Cu-005Ni, for comparison.
Both 3Ag and 4Ag showed better thermal fatigue properties than Sn and 1Ag, and a thermal fatigue life of 12Ag 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 b-Sn, cannot accurately describe thermal fatigue lives observed. On the other hand, Vickers microhardness of the solders, which was resulted from fine dispersoids, showed good relationship with observed thermal fatigue endurance"
Electromigration behaviors in Sb particle-reinforced composite eutectic SnAgCu solder joints
Scopuss: "Due to the limited capacity of solder joints in microprocessors for the higher current density (usually 103-104A/cm2), electromigration (EM), known as the mass movement resulting from imposition of high current density, has gained extensive attention during the last decades, specifically, the EM-induced damages in the eutectic 95.5Sn-3.8Ag-0.9Cu (e-SAC) that were heavily used in the electronic packaging industry. In order to conquer the instable physical properties of e-SAC in the severe service environment, composite approach was developed. One of the promising ways was intentionally incorporated metal-particles reinforcements.
In this study, the e-SAC with 1wt% Sb particles additive was investigated under the current density of 104A/cm2 and 120C the ambient temperature."
Beijing University, China
Polymer nanocomposites for electronic packaging
Scopus: "This paper examines the use of Polymer nanocomposites in the area of electronic packaging. This includes capacitors and resistors as embedded passives, low k materials, electrically conducting adhesives (ECAs) as interconnects, etc. Polymer nanocomposites can provide high capacitance densities, ranging from 5nF/inch2 to 25 nF/inch2, depending on composition, particle size and film thickness"
Endicotts
Cytotoxicity of silver solder employed in orthodontics
Scopus: "The results revealed a maximum response rate for the silver soldering group, as well as severe inhibition of cell proliferation and growth, more round cells with mostly darkened and granular aspects, suggesting lysis with cell death. A similar response was seen in the positivecontrol group.
Conclusion: The hypothesis is rejected. The silver soldering used in orthodontics represents a highly cytotoxic material for the cells analyzed."
Investigation of Gold Nanoparticle Inks for Low-Temperature Lead-Free Packaging Technology
Scopus: "Gold nanoparticle inks were investigated as a potential candidate for lead-free packaging applications. Inks consisted of surfactant-passivated nanoparticles dissolved in a solvent.
Optimized gold inks are able to sinter at temperatures as low as 120C and achieve conductivities of up to 70% of bulk. Once sintered, the metallic structure reverts to bulk-like properties and approaches bulk reliability and performance.
Thus nanoparticle-based solders would operate at much lower homologous temperatures as compared with alloy-based solders. Nanoparticle inks under investigation were sintered at 180C. The resulting material exhibited a resistivity of 5 μΩcm, which is significantly lower than those of Pb-Sn and Sn-Ag-Cu. Electromigration studies were carried out and time to failure was investigated as a function of temperature.
Electromigration activation energy was calculated through Black's equation to be 0.52eV, which is consistent with surface/grain boundary diffusion. These studies suggest that nanoparticle-ink-based films show excellent robustness, due to their irreversible conversion to bulk-like materials. Nanoparticle inks are thus promising candidates for next-generation lead-free solders."
Effect of Electromigration on Interfacial Reactions in 90Sn-10Sb Pb-Free Solder Joints
Scopus: "The electromigration effect on interfacial reactions in Cu/90Sn-10Sb/Cu Pb-free solder joints was investigated under electric current stressing. The growth of the Cu3Sn and Cu6Sn5 intermetallic compound (IMC) layers was enhanced at the anode but inhibited at the cathode, compared with the no-current case."
Shenyang National Laboratory for Materials Science, China
University of Illinois, US
Microstructure, Intermetallic Growth, and Reliability of Rapidly Solidified Pb-Free Solder Joints Formed via
Scopus: "The majority of research on Pb-free solders has been done with reflow times sufficient to allow significant intermetallic growth at the liquid solder/pad interface. With the need for small, fine-pitched solder joints and to avoid damage to heat-sensitive read/write sensors, the hard disk drive industry predominantly uses solder jet bonding for electrical connections of the heads.
This technique does not use flux and has solidification times on the order of a millisecond, four orders of magnitude smaller than that of conventional solder technology. Therefore, the intermetallic formation is highly nonequilibrium and is localized near the pad interface. Surface finish thicknesses and composition have a significant influence on intermetallic growth and composition of solder joints. The intermetallic microstructure, along with voids, can significantly impact joint reliability.
In this paper, results of wettability and mechanical solder ball shear measurements on as-plated and aged samples are reported and correlated with microstructure and growth of intermetallic compounds (IMCs) at the solder/pad interface. A wide range of Au-Sn IMCs are found at the pad interface, and Au-embrittlement effects are not found until Au exceeds 7wt.%."
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