Encapsulation of Power Modules for Extreme Environment Electronics

It has been demonstrated that wideband gap devices fabricated from SiC, or GaN grown on SiC, can operate over a much wider temperature range than traditional silicon or GaAs devices. However, most of the packaging technology in use to today was developed for silicon or GaAs devices and much of this technology is fundamentally limited in its temperature range. For example encapsulation and housing materials often have maximum service temperatures of 200°C. Therefore, new technologies are needed to enable the wide spread use of these new devices at elevated temperatures. In particular, the identification or development of suitable gels and housing materials for power electronic modules operating at high temperature is a critical issue. These power modules operate with very high internal voltages, and gels and polymeric housings have traditionally been used to prevent arcing within the packages.

This paper seeks to address one of these fundamental issues, which is the dielectric breakdown strength associated with the encapsulating gels and housing materials under extreme environmental conditions. Several potential materials were selected and long term reliability data on a number of encapsulation gels and housing materials that are suitable for operation of these devices in excess of 180°C is provided. Baseline electric breakdown data measured at high temperature as well as data on aged samples has been collected.