Experimental Determination of Thermal Contact Resistance Between Metallic Substrates Using an In-House Developed Portable Thermal Contact Resistance Setup

Thermal contact resistance (TCR) is critical in cryogenic, nuclear, space, and electronic systems as it affects heat transfer efficiency at material interfaces. Minimizing TCR enhances system performance, reliability, and lifespan. Accurate TCR measurement is essential for evaluating thermal interface materials (TIMs) and ensuring optimal thermal management. This investigation focuses on developing an in-house experimental setup for measuring TCR between metallic substrates. Two copper samples (L/D < 1) were used as the heat source and sink. The heat flux transients at the source/sink interface were estimated using an inverse heat conduction technique with recorded temperature data of the sink as input to a developed numerical model. The effect of surface roughness and interfacial pressure on TCR was studied. As the contact surfaces changed from rough to smooth, TCR values decreased. As interfacial pressure increased from 0 k N/mm2 to 189.65 k N/mm2, TCR values for rough surfaces fell from 1.0 m2 K/kW to 0.57 m2 K/kW. When solder paste (SAC0307) was used as a TIM under no-load condition, a significant drop in TCR for rough surfaces was observed, falling from 1 m2 K/kW to 0.37 m2 K/kW. An additional finding is the time required for the source and sink to reach thermal equilibrium, which is significantly influenced by surface roughness, TIM, and the interfacial pressure. The results suggest that for smooth interfaces involving high-thermal-conductivity source and sink materials, the benefit of TIMs is limited. A key conclusion of the study is that the heat sink requires approximately 21 s longer to reach thermal equilibrium for every 0.1 m2 · K/kW increase in thermal contact resistance.