Looking for ways to troubleshoot or optimize your Thermal Interface materials? One method which we have contrived to determine the performance of your thermal stack-up excluding the thermal interface material is to use a liquid metal. This is a topic I have discussed at multiple conferences, but will discuss in-depth in a later posting.
Another method that can be used involves placing a phase change metal at the thermal interface to make a mold of the Tthermal interface material gap. Some metal thermal interface materials melt at a low enough temperature to melt during chip operation or under mild heat. At room temperature however, they re-solidify, taking a mold of the thermal interface material gap. By disassembling your thermal stack-up with the phase-change metal, you can view any non-planarity of substrates or surface roughness through inspection of the metal thermal interface material. It is unlikely that the interface material will completely squeeze-out or appear with a smooth mirror-like finish because no machined parts are perfect. This method will demonstrate just how far off perfect your material design has come.