Mechanical Properties and Interface Microstructure of SAC305 Solder Joints Made to an Ag-Pd-Pt Thick Film Metallization: Part 1—Processing Effects

The processibility was document for interconnections made between the 96.5Sn-3.0Ag-0.5Cu (wt.%, abbreviated SAC305) Pb-free solder and an Ag-Pd-Pt thick film conductor on an alumina substrate. The Sheppard’s hook pull test was used to assess the solder joint strength. Microanalysis techniques documented the corresponding microstructures. Excellent solderability was observed across the process parameters defined by the soldering temperatures of 240–290°C and soldering times of 15–120 s. Molten SAC305 solder dissolved the Ag-Pd-Pt thick film, leading to the precipitation of Ag (trace of Pd) and (Pd, Pt)xSny intermetallic compound (IMC) particles upon solidification. The mechanical strengths of the solder joints were excellent (10–15 N) and remained largely insensitive to the processing conditions. The failure mode was ductile fracture in the solder. These findings confirmed that the SAC305 solder/Ag-Pd-Pt thick film interconnection system had the necessary process window for use in high reliability, hybrid microcircuit (HMC) applications.