Improving Thermal Contact Conductance from Electronics Board to Rack Infrastructure

This paper presents experimental results of thermal contact conductance between an electronics board and rack infrastructure. For line replaceable units using liquid conduction cooling, the baseplate-cold plate interface introduces a critical thermal resistance. Using a dedicated experimental set-up that measures temperature gradients across such interfaces, this study systematically analyses key design parameters, such as surface roughness, contact pressure, coatings, such as nickel and tin plating, and the application of indium as thermal interface material. Limitations of theoretical models are addressed demonstrating the importance of experimental testing. Empirical results of this study show that coldplate plating and the use of indium have the most impact on the interface heat transfer coefficient. The presented results enable design engineers to improve thermal contact conductance thereby extending the range of liquid conduction cooling for cases in which electronics boards are clamped into a rack infrastructure.