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|Reliability Analysis of Lead Free Solder Joints with Solder Doping on Harsh Environment|
|Keywords: Doped Lead Free Solder, Harsh Environment / High Temperature, Reliability|
|This study is to evaluate the effect of long term isothermal aging and thermal cycling on the reliability of lead-free solder mixes with different solder doping, PC Board plating, and temperature aging for ball grid array (BGA), quad flat no lead packages (QFN) and 2512 Resistor from different environment of electronics. The primary goal is to find a manufacture able solder paste that will mitigate the effects of aging on lead-free solder joints, and secondary goal would be to find a paste for solder doping that could be used for individual package reliability enhancement and a solder for solder-sphere replacement to enhance the solder joint reliability. Twelve doped solder pastes supplied by eight companies of Alpha, Accurus, Heraues, Indium, Henkel, Inventec, AIM, and Senju, as well as SAC105 and SAC305 lead-free solder balls together with three board platings of OSP, Immersion Silver and ENIG are being tested. Package sizes ranges from 15mm, 0.8mm pitch BGA to 6mm, 0.5mm pitch BGA, and QFN and 2512 Resistor were tested. Isothermal temperature condition is 125¡æ with aging time period of 12 months. Subsequently, the specimens were thermally cycled from -40¡æ to 125¡æ with 15 minutes dwell time at the high and low peak temperature. Failure modes of solder joints as well as microstructure change will be investigated using Scanning Electron Microscope (SEM) to track different crack propagations across the solder bulk cross section, and also Intermetallic Compound (IMC) layers thickness will be measured. Energy-dispersive X-ray spectroscopy (EDX) will be employed also to analyze the chemical characterization of IMC layer for SAC/ImAg, SAC/OPS and SAC/ENIG systems. Data analysis will be performed, and statistical Weibull distribution will be used here to show the characteristic life degradation for different solder pastes under different conditions. Ideal outcome for this project should conclude which solder paste and board plating combination provides the best reliability of each component category, and how thermal aging effect influences the reliability to the lead free solder balls.|
|Cong Zhao, Ph.D. Candidate