Laser Soldering Process Optimization of MEMS Probe of Probe Card for Semiconductor Wafer Test

Abstract

In this study, the laser soldering process of probe-multilayer ceramic (MLC) substrates was optimized using Type 4 (T4) and Type 7 (T7) Sn-3.0Ag-0.5Cu (SAC305), T7 Sn-0.7Cu solders to improve the high-temperature durability of probe solder joints and satisfy the fine pitch requirements of the soldering process. Thermal cycle tests (TCTs) were performed to compare the heat resistance characteristics of the probe solder joint. The results showed that the bonding strength degradation rates of the SAC305 and Sn-0.7Cu solders after the TCT were within 40% compared to that of the as-soldered state. Because the probe surface and MLC were plated with Ni/Au, various intermetallic compounds (IMCs) were observed at the solder joint. The total IMC thickness of the T7 solder joint was thinner than that of the T4 solder because of the difference in redox reactions according to the particle size of the solder paste. The fracture surface of the probe-MLC solder joint after the shear strength test exhibited a mixed ductile and brittle fracture, and that of the Sn-0.7Cu solder joint exhibited a ductile fracture with numerous dimples.