| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 103 === The microstuctures mechanical properties of Sn3.5Ag lead-free solders addition various alloy elements are investigated in the paper. In this study, the Cu(2.5wt.%) Ni(2.5wt.%) and Zn(2.5wt.%) Ga(2.5wt.%) are added to Sn3.5Ag lead-free solders, in which the microstructures and mechanical properties of these lead-free solders are compared with the conventional Sn40Pb solder. In addition, the difference of cooling rates significantly effects on the wettability, IMC layer, and shear strength of the lead-free solders are investigated in detail. The solders was put on the copper plate, and welding at 250℃, 260℃ and 270℃, respectively. After welding, the wetting angel of solder was measured by laser angle-measured meter. The IMC layer growth rate of the as received lead-free solder weldment, and post weldment aging at 150℃ for 250h, and 150℃ for 500h were measured by optical microscopy.
The experimental results indicate the higher welding temperature, the worse wettability. It is confirmed that the wettability is related to shear strength. By use of optical microscopy observation, it is observed indicate that that the longer aging time the thicker IMC layer will be the result. The study discovers that after thermal aging, the Zn(2.5wt.%) Ga(2.5wt.%) additions to Sn3.5Ag lead-free solders can suppress the IMC layer growth rate.
Keywords: Lead-free solder, Sn3.5Ag, Wettability, IMC layer, Shear strength
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