The Impact of Die Tilt on the Reliability of Packages With Dies Bonded to Substrates Using Silver Sintered Material

Abstract In semiconductor packaging, there is a significant push to replace lead-based solders with silver or copper sintering due to the harmful effects of lead-based solders on health and the environment. Additionally, the high thermal and electrical conductivity of sintering materials aligns with the current requirements for high-power semiconductor packages. However, the sintering process is complex, involving multiple stages, and heavily relies on the expertise of the packaging engineer. One of the less understood defects associated with sintering the die to the lead frame or substrate is die tilt, and its impact on the reliability of the package remains unclear. In this article, an investigation was conducted on samples manufactured in our lab to identify the range of resulting die tilt and its source. Furthermore, an analytical model was developed to study the influence of the die tilt on the reliability of the package through stresses in the bond layer. This model was verified through finite element simulations and validated with experiments. The results showed that the die tilt has no influence on the warpage of the package, but it has a significant influence on the shear and peeling stresses in the bond layer and, subsequently, on the fracture in the bond layer. The reliability of the package is influenced by this fracture in the bond layer. The die tilt ranges between ±0.3 deg and is primarily attributed to substrate irregularities. Die tilt significantly impacts the reliability of the package and must be considered as a worst-case scenario during the package design phase. The analytical model serves as a crucial tool that should be utilized in the package design process.