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Indexed by:会议论文

Date of Publication:2009-01-01

Included Journals:CPCI-S

Page Number:511-515

Key Words:Sn-3.5Ag; Sn-3.5Ag/Cu; Strain sensitivity; Shear; Fracture

Abstract:The multiscale microstructures and shear properties of Sn-3.5Ag at different cooling rates and Sn-3.5Ag/Cu joint have been studied. Results show that when the cooling rate decreased from 3.5K/s to 1.0K/s, short-needlelike bulk Ag(3)Sn intermetallic compounds (IMCs) formed and dispersed homogeneously in matrix. Simultaneously, eutectic region was refined. Linear increasing relationship on log-log plot was obtained between shear strength and shear strain rate for all samples. The shear strength of Sn-3.5Ag solder at fast cooling rate was higher than that at a slow cooling rate, but both were smaller than that of joint. The strain sensitivity exponent m for bulk solders at 1.0K/s, 3.5K/s and joint was 0.094, 0.076 and 0.082, respectively. Fractography analysis indicated all the solder samples, and Sn-3.5Ag/Cu joint at low strain rates (0.1rad/s and 1rad/s), exhibited ductile fracture no matter what cooling rate. At high strain rate (10rad/s), broken Cu(6)Sn(5) were found in the fractography of Sn-3.5Ag/Cu joint. However, the main part of the fractography was still composed of dimples, which indicated mixed fracture happened.