Effects of multiple ceramics on reliability in high current power modules

Ceramics in power modules must provide electrical isolation and simultaneous thermal management. The disadvantage of this dual functionality is in the module finished assembly. The difference in the coefficient of thermal expansion of the isolation materials, relative to the baseplate can induce high strain energy at the solder interface. The number of ceramics used, thickness, material type and location on the power substrate all influence the reliability of the power module. The purpose of this paper is to show the effects of multiple ceramics on the substrate, subjected to temperature cycling. A methodology for determining reliability is presented herein