Assembly Reliability and Molding Material Comparison of Miniature Integrated High Power Module With Insulated Metal Substrate

Given the increasing demand for power density and lightweight specifications, the discrete transistor outline-type package is no longer sufficient for personal vehicle. The new generation of high-power drive needs excellent heat dissipation and miniaturized system simultaneously. However, a traditional architecture of power module, direct bonding copper substrate, has serious warpage deformation and limitation of the heat dissipation. Therefore, a power module with an insulated metal substrate (IMS) is proposed. The proposed power module has a smaller volume, better electrical and thermal performance, and high reliability to be utilized in personal vehicles. A fine-quality assembly process is also presented and verified. Furthermore, two different kinds of molding materials that are widely used in power modules, silicone gel, and epoxy, are utilized. The IMS-type module with silicone gel molding fails the temperature cycling test (TCT) with the delamination of the solder layer. The module with epoxy successfully passes the automotive-grade reliability tests, including TCT, highly accelerated stress test, high-temperature reverse bias, and intermittent operational life test according to the standard of AEC-Q101. The finite element analysis for the IMS power module is presented and analyzed under the condition of TCT to estimate the mechanical behavior of the solder layer. The equivalent plastic strain of solder layer with silicone gel and epoxy is 0.76 and 0.08, respectively, after TCT, separately. The main reason can be attributed to the coefficient of thermal expansion between the IMS and molding material. According to the analyzed results, the effect of molding material should not be ignored in the power modulus.