SLID bonding for thermal interfaces – Thermal performance

Solid-Liquid Inter-Diffusion (SLID) bonding is traditionally a technology used for high performance and high reliable die attach/interconnect applications [1]. The generic properties of SLID allows the bonding to occur at a relatively low process temperature. However, when the bond is completed, the final joint has a melting temperature well above the process temperature. This makes it well suited as a thermal interface material (TIM) for electronic assemblies. The typical bonding temperature of Cu-Sn SLID and Au-Sn SLID are 280-300 °C and 320-350 °C respectively. These temperatures compare to that of other high temperature (HT) electronic adhesives e.g. Staystik® 101G. The thermal performance of the SLID bond is superior to other electronic TIMs. This is due to the thin joint (~ 10 µm) and the high thermal conductivity (~ 60 W/mK for Au-Sn). Thus, the thermal resistance of a SLID joint, about 0.2 mm2K/W, is significantly lower than most other joints suitable for use in electronic assemblies.
In this study SLID bonding is introduced as a novel TIM for electronic assemblies. Simulations are performed to compare the stationary thermal performance of SLID with other high performance and HT adhesives. Finite element analysis (FEA) is used to perform the simulations. The study is based on a case study involving a HT (> 200 °C) power controller device for a brushless DC motor for downhole applications. The results demonstrate the superb relative thermal performance of SLID compared to other state-of-art high performance and HT adhesives. A parameter study of the model’s sensitivity to the choice of TIM, e.g. power dissipation vs. TIM specs, is also presented.