SLID Bonding for Energy Dense Applications – Thermo-Mechanics

Solid-Liquid Inter-Diffusion (SLID) bonding is traditionally a technology used for high performance and high reliable die attach/interconnect applications. 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 point well above the process temperature. This makes it well suited as for high performance electronic assemblies. The typical bonding temperature of Cu-Sn SLID and Au-Sn SLID are 250-300 °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 interface materials. This is due to the thin joint (~ 10 μm) and the high thermal conductivity (~ 60 W/m∙K for Au-Sn). Thus, the thermal resistance of a SLID joint, about 2×10-3 cm2∙K/W, is significantly lower than most other thermo-mechanical joints suitable for use in electronic assemblies. SLID joints have also proven to be mechanically robust for harsh environment applications.
In this study the thermo-mechanical properties of large Cu-Sn SLID bond are investigated. Simulations are performed to explore the stationary thermo-mechanical performance of the joint. 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 effective strain was found to be high in the bond adjacent Cu layers but reasonably small, < 1%, within the joint itself.