Accelerated testing of IGBT power modules to determine time to failure

Reliability of IGBT power modules is crucial to their use in failure critical systems and with the advent of all electric and hybrid vehicles the need for good reliability data for IGBT modules is essential. IGBT power modules are constructed of layers and power dies, all of which are interconnected with solder or bond wires. These materials have dissimilar coefficients of thermal expansion and during its life, the IGBT module experiences temperature changes which cause stresses to build up in the various materials eventually resulting in the failure of the module. Because of the high robustness of these modules, testing in service for time to failure can be a very lengthy process. This paper describes a procedure and test rig which can automatically temperature cycle IGBT power modules in a very short time and determine their life expectancy. The paper also shows test results from a number of modules and correlates this data to provide a time to failure for the modules.