Pressure-Dependent Thermal Characterization of Biporous Copper Structures

With the advance of modern semiconductor technology, the power density of electronic devices continuously increases. The performance of electronic devices is now governed by heat dissipation from the heat source to the heat sink, which requires new efficient thermal management solutions. Thermal interface materials (TIMs), placed between heat source and heat sink, are designed to form a conduction pathway by providing a low thermal resistance conduit and by eliminating the air gaps between two contact surfaces. However, most TIMs commercially available show limited performances as they are either thermally conductive but stiff (e.g., metals) or mechanically ductile with high thermal resistance (e.g., polymers), which motivates the search for new materials for the use in TIMs. In this article, we suggest a new type of metal/polymer composite-based TIMs with the aim of developing thermally conductive and mechanically compliant materials at a low cost. Metal/polymer composite-based TIMs are fabricated by using a hydrogen bubble-templated electrodeposition method that forms microscale cavities and nanoscale nanofeatures on copper substrate, called the biporous copper (BPCu). The BPCu is then sintered to enhance the structural strength and is infiltrated by polydimethylsiloxane (PDMS) to increase its structural flexibility and durability against mechanical or thermal stresses. We measure the pressure-dependent thermal resistances of TIMs by assuming 1-D thermal conduction. The average effective thermal conductivities are 19.4 and 18.3 W/m K of 60% and 80% PDMS filling ratio samples, respectively. In addition, enhancements in mechanical strength of BPCu/PDMS TIMs are confirmed through the smaller structural deformation.