Achieving SiC Power modules with high heat dissipation by Developing New Bonding Material

Abstract:
This presentation introduces a high heat dissipation module using a new bonding material. The base material for the new bonding is made up of aluminum, which makes it less expensive than the Ag sinter material. The proposed new material and structure, improves the heat dissipation performance of the power module by 12 % better than that of the Ag sinter model. Based on the proposed structure, we simulated different bonding materials and thermal stacks. As for the actual measurement conditions, not only the bonding material but also optimized structure of heat spread was changed and confirmed. In addition, the optimal structure of thermal diffusion is not only the vertical structure, but also the horizontal structure. In general, there are two ways to improve heat dissipation in the internal design of the power module. 1. How to use materials with high thermal conductivity. 2. The method of designing materials with high thermal conductivity to diffuse heat, that is, assembling thick materials with high heat dissipation near the heat source. Two of these methods are mainstream. This presentation introduces the new design product that uses both methods to achieve the optimal design of the power module and maximizes performance with single-sided heat dissipation. The base material of the developed bonding material is Al and both surfaces are Ag plated. Bonding is carried out in a solid state with pressure and thermal assistance. As a reliability evaluation of Ag sinter and the new bonding material, bonding 5mm SiC chip to a Cu substrate of 2mm, respectively, and confirmed the result of the delamination rate of the bonding material after 1000 cycles at -40 ~ 150 °C in thermal shock test. A significant difference in the m,η values of the Ag sinter of the new material was observed. The new material had m,η values of 28.5,25.2, while Ag sinter had m-values of 0.74 or 7.31 and η values of 46.2. This makes the design thick Cu substrates by using new bonding materials possible, which enables high heat dissipation in power module technology and has succeeded in developing module element technology with high heat dissipation. ROHM's power modules are the original power module developed based on new bonding technology. Since it can achieve both excellent heat spread and high reliability, The design of the ceramic substrate for insulation is as simple as possible. This is not only an excellent thermal design, but also a design that takes into account the current balance, that is, the resonance risk of the SiC power module. With this new technology development, ROHM power modules are expected to achieve a current density of approximately 37 A/cm3 per switch for a 2-in-1 750-V power module.