Design optimization for a power package by simulation

As one of challenges, clip design for bonding area is becoming smaller and smaller to achieve die size requirement, better view inspection and efficient solder flux cleaning. However, with a small bonding area, there will be a concern on high thermal resistance during working condition, especially under a surge current, in which junction temperature may be higher than the melting temperature of soft solder, i.e. 298 °C, resulting in a potential concern of package reliability. Therefore, design optimization has to be done to reduce the risk on reliability as low as possible. In this study, different clip designs are proposed and effect of clip tip, die pad size and die size on junction temperature under surge test are studies. Simulation data show that clip design is the only key for device to pass surge test without any soft solder melting issue. A clip design guideline is thereafter provided with that making clip tip small as possible for better view inspection and solder flux cleaning, but also keeping a good thermal performance to pass surge test without reliability concerns.