Thermal interface materials (TIMs) act as heat transfer pathway between heat source and heat sink, and with the booming growth of microelectronic devices, power density increase calls for highly efficient TIMs for better performance and thermal management. For TIMs, not only high conductivity is required but also durability against external forces, surface flexibility and production easiness should be regarded as benchmarks for TIMs evaluation. Traditionally, metallic-based TIMs provides high thermal conductivity but low surface flexibility, and their polymer counterparts show opposite characteristics. To combine the benefits from both groups, we propose a metal/polymer composite TIM via reinforcing the three dimensional porous copper structure with polymer matrix. We utilize horizontal deposition to fabricate self-assembly polymer sphere opal structure, and the opal structure works as sacrificial template to create semi-ordered 3D porous copper inverse opal structure (CIO) by electrodepositing copper to fill the gaps between polymer spheres. Structure pore sizes are chosen to be 1400 and 2600 nm, and SEM images for as-fabricated CIO samples will be utilized to analysis structure heights, porosity and surface morphology. CIO samples are then infiltrated with 80% volumetric filling ratio by polydimethylsiloxane (PDMS) to increase structural flexibility and durability against mechanical or thermal stresses. In this study, one-dimensional heat transfer testing apparatus with adjustable pressure source is built, and the linearity test as well as silicon-copper interface resistance calibration under different pressure is firstly examined to ensure data validity. For measuring total thermal interface resistance, the CIO/PDMS sample is place between two dimensionally symmetric copper bars with applied pressure provided by the thread rod. The applied pressures are quantified by load cells, and values are set to range from 0.5 to 3 MPa. The temperature distribution along two copper bars will be recorded for heat flux and thermal interface resistance calculation. We investigate the pressure-dependent thermal characteristics of CIO/PDMS samples by employing one-dimensional thermal conduction, and the measured thermal resistance shows more uniform distribution when the applied pressure increases. The measured total thermal interface resistances (R”total) follow pressure-inverse relation, and with higher structure thickness, higher total thermal interface resistance is observed. We further discuss the mechanical strength enhancement by comparing structure thickness changes under different applied pressure, and the result demonstrates that with PDMS infiltration, less structure deformation will occur and better mechanical strength can be achieved.