Silicone Gels for Continuous Operation up to 200 C in Power Modules

Silicones have been used for decades as protective materials for power modules. Whereas the original formulations suit the temperature requirements of early generation IGBT chips (with a junction temperature of 150deg C), recent advances in IGBT design and the emergence of new compound semiconductor technologies such as silicon carbide and gallium nitride are pushing the operating temperature limits to higher values - up to 175deg C as of today. However, the potential of SiC and GaN goes well beyond the 175deg C operating temperature and a market pull for higher temperature of operation, up to 200deg C or higher, has been required. This requires the development of high temperature resistant silicone gels for the protection of the power chips together with the adequate sintering technology and housing material capable of operation at such temperatures. The purpose of this paper is to present the recent advances from DOW in the development of high temperature resistant silicone-based gels to meet the 200deg C continuous operating temperature of the next generation of power modules. The first section of this paper will explain the benefits of high temperature resistant gels together with the challenges that have to be solved. The second section will provide reliability data on two different candidates developed by DOW and capable of temperature resistance at 215deg C for up to 2000 hours.