Thermal modeling and experimental validation of thermal interface performance between non-flat surfaces

Thermal interface materials (TIMs) are commonly used to reduce the thermal resistance between an electronic device and its cooling solution. The thermal performance of a TIM is very sensitive to its bond line thickness, and hence, the warpage profiles of the mating surfaces. The contact surfaces are usually never perfectly flat due to the manufacturing process induced warpage in heat sinks and electronic packages. This paper focuses on a simplified numeric approach to simulate thermal performance of a TIM between the non-flat surfaces. This modeling approach uses an “equivalent” thermal conductivity to simulate warpage rather than building actual surface curvature in the model. In order to validate the numerical model, a test apparatus was developed and tooled up to measure the thermal resistance of an aluminum-nitride (AlN) filled thermal grease between the non-flat surfaces. It can be concluded that the simplified numerical approach can efficiently predict the TIM thermal performance between non-flat surfaces. This model can be further extended to the cases with more complicated surface profiles and multiple heat sources