Pb-free, High Thermal and Electrical Performance Driven Die Attach Material Development for Power Packages

Most power packages still use a high-lead (Pb) solder paste because the high-Pb solder paste has the advantage of no re-melt during the printed circuit board (PCB) reflow process as well as good wettability and high reliability performance. There are a few material candidates that could meet the reliability compliance to AEC-Q100/-Q101 Grade 0 and provide thermal and electrical performance comparable to lead solder. Silver (Ag)-sintered material is one of candidates. However, the different types of Ag-sintered materials available in the market have not been proven to meet the required quality level and have not been validated for workability. This paper investigated Ag-based materials to replace a high-lead (Pb) solder paste and checked associated processing and reliability testing for power discrete packages. Evaluation was conducted from material screen-out by workability check, epoxy coverage and void-free performance. In addition, automotive reliability had to be confirmed with the process workability. Electrical/thermal performance were simulated with material and localized void ratio and confirmed for performance comparable or better than the current high-Pb material. The new material is expected to achieve void-free and high thermal/electrical performance and address the environmental issue with Pb.