Analysis of Indium-Silver Alloy Thermal Interface Material Reliability and Coverage Degradation Mechanisms

Thermal management of microprocessor chips has emerged as a critical issue to ensure high-power operation, especially in high-performance computing (HPC) applications such as artificial intelligence (AI). To effectively transfer the heat generated from the chip junction to the heat spreader or heat sink, the development of thermal interface materials (TIMs) with high thermal conductivity and the processes for applying them are very active in the electronics packaging industry. In general, polymer-based TIMs have been widely developed and used for their mechanical properties and process workability. However, due to the limitations of polymers, the thermal conductivity required for HPC applications cannot be satisfied. Indium (In) has been widely selected for high power consumption devices as a high dielectric constant (k) TIM due to its high thermal conductivity. However, the low liquidus point of In can be problematic for flip chip lidded ball grid array (FCLBGA) applications since indium may be re-melted during ball attachment reflow, which can reduce TIM coverage [3]. In this paper, indium-silver (InAg)-based alloys were evaluated to develop high thermal conductivity TIM solutions that can be applied to large body FCBGA devices and examines the reliability of indium-silver alloy TIMs under thermal cycling conditions. By varying the silver content, we investigated its impact on mechanical stability and TIM coverage degradation. Indium alloy with higher silver content showed reduced package warpage and fewer voids, as observed through Shadow moire and SAT inspection. In contrast, Indium alloys with lower silver content exhibited more significant structural deformation and void formation Our findings suggest that increasing silver content in indium alloys enhances the TIM coverage and mechanical stability with better thermal performance