Investigating micro-alloyed solders with thermal shock tests

This paper presents how the low Ag content and micro-alloys in solders can influence the quality and the reliability of joints during thermal shock tests. The solder joints of 0603 (1.6 × 0.8 mm) size surface mounted resistors were compared, while the thermal shock cycle number was increased up to 2000 cycles. The low Ag content, micro-alloyed solders, named mSAC1 and mSAC2, were compared to normal SAC305, SAC405 and 62Sn36Pb2Ag solders. Cross-sections were made to measure the Cu₃Sn and the Cu₆Sn₅ intermetallic layers´ average thickness. By inspecting the cross-sections, it is also revealed what kind of typical crack path has formed in the solder joints.