Enhancing Semiconductor Package Reliability through Mechanical Property Optimization of Pressureless Sintering Die Attach Adhesives

Abstract

There is growing demand for high-power devices, wide bandgap SiC and GaN semiconductor materials in semiconductor market, and a drive to integrate die attach materials that can replace lead-containing solders. However, epoxy-based and solder materials face challenges to meet high thermal conductivity and survive elevated working temperatures. Pressure-assisted silver sintering has overcome these challenges, but downsides of pressure-assisted silver sintering are that it requires special equipment and for some applications, packages are unable to withstand the pressure required to facilitate sintering. Pressureless sintering materials could be processed using the same equipment as traditional die attach adhesives. It develops strong metal bonds to substrates, providing high thermal conductivity and withstanding high temperatures. However, compared to pressure-assisted sintering, pressureless materials may have difficulties to form a dense bondline structure if the formulation design is not optimized. Moreover, once the sintered structure is built during cure, further bondline reduction may induce additional stress. Therefore, it is critical that the pressureless sintering material’s mechanical properties are formulated to effectively manage stress and pass all reliability testing – especially for automotive packages. This paper will present the findings from a study that evaluated the impact of various formulation components – such as silver packing and resin chemistry – on the mechanical properties and interfacial bonding of pressureless sintering die attach adhesives. The effect on in-package reliability performance was also investigated to better understand material properties that can pass reliability testing while maintaining high thermal and electrical conductivity adhesive requirements.