High Reliability Power Package Design for Automotive Requirements

As the high demand of high power and high current in power discrete packages, products are applying the bigger die size but are limited by the same package footprint. The bigger die size requires bigger exposed pad(e-pad) size but limited by given footprint and gives challenges to package design and assembly process. Along with the size challenges, the package should consider high reliability requirement for automotive application. Once die size is getting bigger, high die to exposed pad size ratio is worse in package reliability. Because it causes package delamination and die crack due to insufficient adhesion around the silicon die. This paper investigated package cracks by structure and material property, especially the epoxy molding compound (EMC). To achieve a robust package structure with even bigger die size, an evaluation was conducted on several types of EMCs and various leadframe design options and verified by mechanical simulation. Finally, the key considerations for package design are proposed based on the results.