Thermal Cycling Reliability of Alternative Low-Silver Tin-Based Solders

2014 ◽  
Vol 11 (4) ◽  
pp. 137-145 ◽  
Author(s):  
Elviz George ◽  
Michael Osterman ◽  
Michael Pecht ◽  
Richard Coyle ◽  
Richard Parker ◽  
...  
Keyword(s):  
Silver Content ◽  
Temperature Cycling ◽  
Temperature Cycle ◽  
Sac305 Solder ◽  
Test Assembly ◽  
Snpb Solder ◽  
Primary Focus ◽  
Free Solder ◽  
Electronic Assemblies ◽  
Cycles To Failure

Sn-3.0Ag-0.5Cu (SAC305) alloy is the most widely used solder in electronic assemblies. However, issues associated with cost and drop/shock durability have resulted in a search for alternative lead-free solder alloys. One approach to improve the drop/shock reliability has been to reduce the silver content in Sn-Ag-Cu alloys. Another approach is doping Sn-Ag-Cu solder with additional elements. In 2008, the International Electronics Manufacturing Initiative (iNEMI) started the “Characterization of Pb-Free Alloy Alternatives” project to provide a comprehensive study of 15 tin-based solder interconnect compositions benchmarked against the eutectic tin-lead solder. For this study, temperature cycle durability was the primary focus and solders were selected to study the effect of varying silver content, microalloy additions, and aging. This paper reports the findings from one of the test conditions conducted under the iNEMI project. The cycles to failure for a temperature cycling test condition from −15°C to 125°C, with dwell times of 60 min at both extremes, are presented. The test assembly consisted of 16 of the 192 I/O BGAs and 16 of the 84 I/O BGAs soldered onto an LG451HR laminate. Test results revealed that the reduction of silver resulted in a reduction in cycles to failure. In all cases, the 15 tin-based solders were more durable than the eutectic SnPb solder. Aging at 125°C for 10 d did not affect the cycles to failure in SAC105 solder; however, the cycles to failure decreased with aging in SAC305 solder. In addition, aging resulted in a wider distribution of cycles to failure in 192 I/O BGAs. Failure analysis was carried out on all solder materials to identify the failure site and failure mode.

Thermal Cycling Reliability of Alternative Low-Silver Tin-based Solders

2013 ◽  
Vol 2013 (1) ◽  
pp. 000120-000127 ◽  
Author(s):  
Elviz George ◽  
Michael Osterman ◽  
Michael Pecht ◽  
Richard Coyle ◽  
Richard Parker ◽  
...  
Keyword(s):  
Silver Content ◽  
Temperature Cycling ◽  
Temperature Cycle ◽  
Sac305 Solder ◽  
Test Assembly ◽  
Cu Alloys ◽  
Primary Focus ◽  
Effects Of Aging ◽  
Electronic Assemblies ◽  
Cycles To Failure

Sn-3.0Ag-0.5Cu (SAC305) alloy is the most widely used solder in electronic assemblies. However, issues associated with cost and drop/shock durability have resulted in a continued search for alternative solder alloys. One approach to improve the drop/shock reliability has been to reduce the silver content in Sn-Ag-Cu alloys. Another approach is doping Sn-Ag-Cu solder with additional elements. Moreover, conflicting results have been reported in literature on the effects of aging on Sn-Ag-Cu alloys. In 2008, International Electronics Manufacturing Initiative (iNEMI) started the “Characterization of Pb-Free Alloy Alternatives” project to provide a comprehensive study of fifteen tin-based solder interconnect compositions benchmarked against the eutectic tin-lead solder. For this study, temperature cycle durability was the primary focus and solders were selected to study the effect of varying silver content, microalloy additions, and aging. This paper reports the preliminary findings from one of the test conditions conducted under the iNEMI project. The cycles to failure for a temperature cycling test condition from −15°C to 125°C, with dwell times of 60 minutes at both extremes are presented. The test assembly consisted of sixteen 192 I/O BGAs and sixteen 84 I/O BGAs soldered on to LG451HR laminate. Preliminary findings revealed that the reduction of silver resulted in a reduction in cycles to failure. In all cases, the fifteen tin-based solders were more durable than the eutectic SnPb solder. Aging did not affect the cycles to failure in SAC105 solder; however, the cycles to failure decreased with aging in SAC305 solder. In addition, aging resulted in a wider distribution of cycles to failure in 192 I/O BGAs.

BGA Solder Life Prediction under Combined Power and Temperature Cycling Condition

2012 ◽  
Vol 2012 (1) ◽  
pp. 000531-000534 ◽  
Author(s):  
Fei Chai ◽  
Michael Osterman ◽  
Michael Pecht
Keyword(s):  
Ball Grid Array ◽  
Temperature Cycling ◽  
Temperature Cycle ◽  
Fatigue Reliability ◽  
Sac305 Solder ◽  
Cycling Test ◽  
Solder Interconnect ◽  
Power Cycling ◽  
Plastic Ball ◽  
Plastic Ball Grid Array

Solder interconnect failure is a known life limiting failure mechanism that is induced by cyclic temperature excursions. Thermal fatigue reliability of solder interconnects is conventionally assessed by simple temperature cycling test, which applies a constant temperature range, fixed dwell times and ramp rates during the test. However, due to the user controlled power cycles, non-constant workloads, and changes in the surrounding environment, electronics in the field often experience a complex combination of temperature and power cycling. In this study, the effect of power cycling superposed on a simple temperature cycling is experimentally examined. Furthermore, a scheme for modeling the solder interconnect fatigue life of Plastic Ball Grid Array (PBGA) parts under the concurrent power and temperature cycling. Damage, defined as the number of applied cycles over the number of survivable cycles, from the simple temperature cycle and the power cycle are linearly added using Miner's rule, and compared with the concurrent temperature and power cycling test. Cycles to failure of each condition is derived by life testing conducted on Plastic Ball Grid Array (PBGA) assembled with eutectic and SAC305 solder.

Evaluating the Impact of Dwell Time on Solder Interconnect Durability under Bending Loads

2012 ◽  
Vol 2012 (1) ◽  
pp. 000510-000513
Author(s):  
Sandeep Menon ◽  
Michael Osterman ◽  
Michael Pecht
Keyword(s):  
Fatigue Life ◽  
Dwell Time ◽  
Hold Time ◽  
Temperature Cycling ◽  
Temperature Cycle ◽  
Mechanical Loads ◽  
Solder Interconnects ◽  
Solder Interconnect ◽  
Electronic Assemblies ◽  
The Impact

With increased portability and miniaturization of modern day electronics, the mechanical robustness of these systems has become more of a concern. Existing standards for conducting mechanical durability tests of electronic assemblies include bend, shock/drop, vibration and torsion. Though these standards provide insights into both cyclic fatigue and overstress damage incurred in the solder interconnects (widely regarded as the primary mode of failure in electronic assemblies), they fail to address the impact of time dependent (creep) behavior due to sustained mechanical loads on the solder interconnect durability. It has been seen that the solder durability under thermal cycling loads is inversely proportional to the dwell time or hold time at either temperature extreme of the imposed temperature cycle. Fatigue life models, which include dwell time, have been developed for solder interconnects subject to temperature cycling. However the fatigue life models that have been developed in literature for solder interconnects under mechanical loads fail to address the impact the duration of loading. In this study, solder interconnect test vehicles were subject to cyclic mechanical bending with varying dwell times in order to understand the impact of duration of mechanical loads on the solder interconnect durability. The solder interconnects examined in this study were formed with 2512 resistor packages using varying solder compositions (SnPb and SAC305). In order to evaluate the impact of dwell time, the boards were tested with a 60 second and a 300 second dwell time on both extremes of the loading profile. It was observed that an increase in dwell time of the loading profile resulted in a decrease in the characteristic life of the solder interconnects.

scholarly journals Study on Creep Damage in Sn60Pb40 and Sn3.8Ag0.7Cu (Lead-Free) Solders in c-Si Solar PV Cell Interconnections under In-Situ Thermal Cycling in Ghana

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 441
Author(s):  
Frank Kwabena Afriyie Nyarko ◽  
Gabriel Takyi ◽  
Francis Boafo Effah
Keyword(s):  
Energy Density ◽  
Creep Strain ◽  
Thermal Cycle ◽  
Creep Damage ◽  
Temperature Cycle ◽  
Solder Interconnection ◽  
Snpb Solder ◽  
Pv Modules ◽  
Free Solder ◽  
Density Methods

A numerical study on the creep damage in soldered interconnects in c-Si solar photovoltaic cells has been conducted using equivalent creep strain, accumulated creep strain and accumulated creep energy density methods. The study used data from outdoor weathering of photovoltaic (PV) modules over a three-year period (2012–2014) to produce temperature cycle profiles that served as thermal loads and boundary conditions for the investigation of the soldered interconnects’ thermo-mechanical response when exposed to real-world conditions. A test region average (TRA) temperature cycle determined in a previous study for the 2012–2014 data was also used. The appropriate constitutive models of constituent materials forming a typical solar cell were utilized to generate accurate material responses to evaluate the damage from the thermal cycles. This study modeled two forms of soldered interconnections: Sn60Pb40 (SnPb) and Sn3.8Ag0.7Cu (Pb-free). The results of the damage analysis of the interconnections generated from the thermal cycle loads using accumulated creep strain method showed that the Pb-free solder interconnection recorded greater damage than that of the SnPb-solder interconnection for the TRA, 2012, 2013 and 2014 temperature cycles. The percentage changes from SnPb to Pb-free were 57.96%, 43.61%, 44.87% and 45.43%, respectively. This shows significant damage to the Pb-free solder under the TRA conditions. Results from the accumulated creep energy density (ACED) method showed a percentage change of 71.4% (from 1.3573 × 105 J/mm3 to 2.3275 × 105 J/mm3) in accumulated creep energy density by replacing SnPb-solder with Pb-free solder interconnection during the TRA thermal cycle. At the KNUST test site in Kumasi, Ghana, the findings show that Sn60Pb40 solder interconnections are likely to be more reliable than Pb-free solder interconnections. The systematic technique employed in this study would be useful to the thermo-mechanical reliability research community. The study also provides useful information to PV design and manufacturing engineers for the design of robust PV modules.

scholarly journals Extreme PCR: Efficient and Specific DNA Amplification in 15–60 Seconds

2015 ◽  
Vol 61 (1) ◽  
pp. 145-153 ◽  
Author(s):  
Jared S Farrar ◽  
Carl T Wittwer
Keyword(s):  
High Resolution ◽  
Single Molecule ◽  
High Resolution Melting ◽  
Dna Amplification ◽  
Temperature Cycling ◽  
High Yield ◽  
Temperature Cycle ◽  
Amplification Efficiency ◽  
Analytical Sensitivity ◽  
Agarose Gels

Abstract BACKGROUND PCR is a key technology in molecular biology and diagnostics that typically amplifies and quantifies specific DNA fragments in about an hour. However, the kinetic limits of PCR are unknown. METHODS We developed prototype instruments to temperature cycle 1- to 5-μL samples in 0.4–2.0 s at annealing/extension temperatures of 62 °C–76 °C and denaturation temperatures of 85 °C–92 °C. Primer and polymerase concentrations were increased 10- to 20-fold above typical concentrations to match the kinetics of primer annealing and polymerase extension to the faster temperature cycling. We assessed analytical specificity and yield on agarose gels and by high-resolution melting analysis. Amplification efficiency and analytical sensitivity were demonstrated by real-time optical monitoring. RESULTS Using single-copy genes from human genomic DNA, we amplified 45- to 102-bp targets in 15–60 s. Agarose gels showed bright single bands at the expected size, and high-resolution melting curves revealed single products without using any “hot start” technique. Amplification efficiencies were 91.7%–95.8% by use of 0.8- to 1.9-s cycles with single-molecule sensitivity. A 60-bp genomic target was amplified in 14.7 s by use of 35 cycles. CONCLUSIONS The time required for PCR is inversely related to the concentration of critical reactants. By increasing primer and polymerase concentrations 10- to 20-fold with temperature cycles of 0.4–2.0 s, efficient (>90%), specific, high-yield PCR from human DNA is possible in <15 s. Extreme PCR demonstrates the feasibility of while-you-wait testing for infectious disease, forensics, and any application where immediate results may be critical.

scholarly journals Distribution and Microstructure Analysis of Ceramic Particles in the Lead-Free Solder Matrix

2020 ◽  
Author(s):  
Manoj Kumar Pal ◽  
Gréta Gergely ◽  
Dániel Koncz-Horváth ◽  
Zoltán Gácsi
Keyword(s):  
Silicon Carbide ◽  
Intermetallic Compounds ◽  
Solder Alloy ◽  
Solder Matrix ◽  
Microstructure Analysis ◽  
Lead Free ◽  
Lead Free Solder ◽  
Sac305 Solder ◽  
Small Change ◽  
Free Solder

Abstract The Sn-3.0Ag-0.5Cu solder alloy is a prominent candidate for the Pb-free solder, and SAC305 solder is generally employed in today’s electronic enterprise. In this study, the formation of intermetallic compounds (Cu6Sn5 and Ag3Sn) at the interface, average neighbour’s particle distance, and the morphological mosaic are examined by the addition of SiC and nickel-coated silicon carbide reinforcements within Sn-3.0Ag-0.5Cu solder. Results revealed that the addition of SiC and SiC(Ni) particles are associated with a small change to the average neighbor’s particle distance and a decrease of clustering rate to a certain limit of the Sn-3.0Ag-0.5Cu solder composites. Moreover, the development of the Cu6Sn5 and the structure of the Ag3Sn are improved with the addition of SiC and Ni coated SiC.

Effect of Aging on the Properties of Intermetallic Layers in SAC+Bi Solder Joints

2021 ◽  
Author(s):  
Mohammad Ashraful Haq ◽  
Mohd Aminul Hoque ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Aging Condition ◽  
Sac305 Solder ◽  
The Poor ◽  
Free Solder ◽  
Lead Free Solders ◽  
Overall Reliability ◽  
Intermetallic Layers

Abstract A major problem faced by electronic packaging industries is the poor reliability of lead free solder joints. One of the most common methods utilized to tackle this problem is by doping the alloy with other elements, especially bismuth. Researches have shown Bismuth doped solder joints to mostly fail near the Intermetallic (IMC) layer rather than the bulk of the solder joint as commonly observed in traditional SAC305 solder joints. An understanding of the properties of this IMC layer would thus provide better solutions on improving the reliability of bismuth doped solder joints. In this study, the authors have used three different lead free solders doped with 1%, 2% and 3% bismuth. Joints of these alloys were created on copper substrates. The joints were then polished to clearly expose the IMC layers. These joints were then aged at 125 °C for 0, 1, 2, 5 and 10 days. For each aging condition, the elastic modulus and the hardness of the IMC layers were evaluated using a nanoindenter. The IMC layer thickness and the chemical composition of the IMC layers were also determined for each alloy at every aging condition using Scanning Electron Microscopy (SEM) and EDS. The results from this study will give a better idea on how the percentage of bismuth content in lead free solder affects the IMC layer properties and the overall reliability of the solder joints.

Analysis of the Interfacial Reaction Between Sn-3.5Ag and Electroplating Interlayers

2005 ◽  
Vol 863 ◽  
Author(s):  
S.M. Yang ◽  
Y.Y. Chang ◽  
Weite Wu
Keyword(s):  
Diffusion Barrier ◽  
Interfacial Microstructure ◽  
X Ray ◽  
Soldering Process ◽  
Free Process ◽  
Snpb Solder ◽  
Microstructure Examination ◽  
Free Solder ◽  
Electroplating Process ◽  
Morphology Characterization

AbstractAt present, Pb-free process is imperative in the electronic packaging industry. Many reports focus on Pb-free solder to improve the solderability, it seems not obtain wettability as good as SnPb solder. In this study, an alloy interlayer with different content was deposited on Cu to balance wettability and diffusion barrier in the interface of joint by electroplating process. There are three types of interlayers including Cu, Ni, and SnNi alloy. The interlayer may react with Sn-3.5Ag solder during reflow process. Sn-Ni alloy plating layer is selected to improve wettability and provide diffusion barrier at the same time in soldering process. For interfacial microstructure examination, morphology characterization can be obtained by using scanning electron microscope (SEM) and energy-dispersive x-ray analysis (EDX). The structure of IMC is identified by x-ray diffraction (XRD).

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