Future Trends of Power Semiconductor Modules

The paper discusses new and future developments in power semiconductors based on research and development investigations now taking place. Thermal Fatigue tests, in which power semiconductor modules are heated by conducting full load current then forced-cooled without load current, result in rapidly changing internal temperature. Power semiconductor modules can be divided into three distinct types. Comparisons are made between conventional-soldered modules, pressure contact modules, and eutectic bonded modules. Reliability, thermal fatigue capability, blocking stability and other features and properties are compared. New construction techniques have resulted in 50,000 cycle capability. This is a significant improvement over the 500 cycle capability of conventional soldered modules. The impact on field failures and long term equipment reliability are discussed. These new power modules will have significant impact on manufacturers of motor drives, switching power supplies, and robotic controls. The equipment manufacturer will be able to take advantage of the next generation modules in order to improve system reliability. The paper includes a detailed discussion of internal construction of power semiconductor modules and how reliability and field failures are affected by various types of modules. Operating life test results are discussed, including High Temperature Blocking Life, Thermal Fatigue, and Thermal Resistance. Major developments in the on-going evolution of power semiconductor modules are traced, in order to identify future trends. The early modules suffered from occasional field failure problems related to deterioration of solder joints under conditions of cyclical load currents. Solutions to these problems have lead to development of a new generation of power modules.