![]() ![]() In the presence of lead from HASL boards or components Bi can greatly reduce thermal cycle fatigue resistance due to the formation of Sn16Pb32Bi52 (MP=95C) which can diffuse along the grain boundaries. ![]() Bi further lowers melting point and improves wettability.In the presence of lead from HASL boards or components indium forms a ternary compound that has a phase change at 114C. Moderate melt point lead-free alternative is lower than SnAgCu.Bi improves wettability and slightly improves corrosion resistance. Stencil life or shelf life of solder paste may be reduced due to reactive nature of zinc. High oxidation rate precludes its use for wave soldering. Zn exhibits high oxidation rate and is susceptible to atmospheric corrosion. Moderate melt point lead-free alternative is only slightly higher than SnPb.A small amount of Ag can improve strength and thermal cycle fatigue resistance, assuming the absence of lead.Bi improves wettability but is somewhat offset by higher oxidation rate. The study also examines the impact of soldering materials, such as tin-bismuth (SnBi) and tin-silver-copper solder alloys (SAC305 and SAC405), on the Cu pillar bump. Large Bi proportion greatly reduces the melting point of the solder, but the alloy is more brittle.Low melt point precludes its use for applications where operating temperature is close to 138C. Low melt point lead-free alternative potentially suitable for some consumer electronics.Bi reduces the melting point of the solder.Cu retards the dissolution rate of copper from boards and components into the molten solder during soldering. Soldering components onto PET substrates must be done using low temperature solder, normal lead free solder is not suitable. Cu improves thermal cycle fatigue resistance. We use a hot plate to solder SMT devices to the PET substrates using low temperature Tin Bismuth solder. Cu reduces the melting point of the solder.Ag provides greater strength but less ductility than Pb.Higher surface tension and poorer wetting than SnPb.SnAgCu family is electronics industry standard which in most cases has shown equal or greater thermal cycle fatigue resistance than SnPb. Higher melt point lead-free alternative.Physical Properties of Lead-free Alloys SnAgCu(Bi) Alloys: Reflow Soldering, Wave Soldering, Hand Soldering ![]()
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