Thermal Conductivity is NOT the Only Deciding Factor: A Guide to Understanding Unaddressed Challenges with Liquid Metals TIMs

In the last decade, technology for advanced chip packaging has created a challenge for thermal engineers. The density at which high-power electronics can be packed into increasingly small spaces has resulted in heat fluxes that, in many cases, cannot be addressed by traditional polymer or silicone based thermal interface materials (TIMs). This has created a need for a new generation of thermally conductive materials. One proposed solution is to use liquid metal-based TIMs. The liquid metal of choice for thermal interface applications is mainly gallium-based liquid metal. Gallium-based liquid metal demonstrates a great deal of promise as a TIM material offering innately high thermal conductivity, non-toxic properties, conformability, resistance to hardening effects, and resistance to delamination effects. However, liquid metal-based TIMs represent a large shift in the TIM market in terms of material properties compared to their polymer and silicone-based counterparts. Thus, the selection of a TIM based simply on the highest possible thermal conductivity is no longer the most critical guiding factor. Instead, a pivot to understanding thermal resistance and what key unaddressed challenges effect thermal resistance is necessary to fully utilize liquid metal TIMs. With this, there are a lot of unique phenomena with liquid metals that affect thermal resistance, thus impacting the material performance in a device. This paper will explore some of these key unaddressed factors that can contribute to thermal resistance with liquid metal materials and seek to provide guidance on how to manage or mitigate these effects.