Pressure-Dependent Thermal Characterization of Bi-Porous Copper Structures

With the advance of modern semiconductor technology, the power density of electronic devices significantly increases. The performance of electronic devices is thereby governed by the efficiency of heat dissipation from heat source to heat sink, which requires better thermal management methods. Thermal interface materials (TIMs), placed between the heat source and heat sink, help a conduction pathway by providing a low thermal resistance conduit and eliminating the air gaps between two contact surfaces. However, most of commercially available TIMs show limited performances as they are either thermally conductive but stiff (e.g., metals) or mechanically ductile but with high thermal resistance (e.g., polymers). In this study, we suggest a new type of metal/polymer composite TIMs by combining the advantages from those two materials in order to develop a thermally conductive and mechanically compliant material at a low cost. TIMs are fabricated by using a hydrogen bubble templated electrodeposition method that forms microscale cavities and nanoscale nanofeatures on copper substrate, bi-porous copper (BPCu). The bi-porous copper 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. Then, the pressure-dependent thermal resistances through the TIMs are measured by assuming one-dimensional thermal conduction. The measurements confirm that the average effective thermal conductivities range from 10-30 W/mK for 80% PDMS filling ratio sample. In addition, mechanical strength augmentations for BPCu/PDMS TIM are discussed, and the result shows mechanical strength enhancement with PDMS infiltration by means of less structure deformation.