Laser Soldering Properties of MEMS Probe for Semiconductor Water Testing

Abstract

In this study, the laser soldering process of microelectromechanical system (MEMS) probes and multilayer ceramic (MLC) substrates was optimized with Type 4 (T4) and Type 7 (T7) Sn-3.0Ag-0.5Cu (SAC305), Type 4 Sn-0.3Ag-0.7Cu (SAC0307), and Type 4 Sn-5.0Sb (SnSb) soldering, and the probe solder joint properties were compared. SAC0307 and SnSb were used to confirm the bonding property of the low-Ag solder and the high-temperature durability. We conducted a thermal cycling test (TCT) with 500 cycles at temperatures of -25 ℃ to 105 ℃ with a 10-min dwell time at each temperature. Before and after the TCT, the microstructure of solder joint as well as the shear strength between the probe and the MLC were examined. The results revealed that, after the TCT, the degradation rate of T7 SAC305 solder was lower than that of T4 SAC305, and the SnSb solder did not exhibit bonding strength degradation. The fracture mode of the SAC solder joint was ductile-brittle. In the case of the SnSb joint, brittle fracture was the major fracture mode because of the Sn-Sb intermetallic compounds. The SnSb solder had an excellent bonding strength and degradation property after the TCT, but the lack of toughness caused brittle fracture. These results confirm the applicability of T4 SnSb and T7 SAC305 solders for high-temperature response and fine pitch bonding.