Microstructured Finger-Joint Interfaces for Reducing Thermal Contact Resistance in Thermal Pad Assemblies

Thermal pads are widely used for heat dissipation in electronic devices, but their performance can be limited by incomplete contact with the adjoining surfaces. In this study, a double-sided finger-joint interface was introduced to improve thermal contact without modifying the composition of the thermal pad. Two commercial thermal pads were assembled between either planar or finger-structured brass substrates and tested under pressures ranging from 0.1 to 1.0 MPa. For both pads, the finger-joint interface reduced the thermal contact resistance to approximately one-third of that measured with the corresponding planar interface. Surface morphology characterization and mechanical analysis indicated that the finger geometry increased the local normal contact force and promoted more effective contact between the pads and substrates. In a bolt-clamped LED assembly, the finger-joint interface reduced the chip temperature by 49.6 °C at 1.0 A, corresponding to a 45.3% reduction in chip temperature rise. This improvement was retained after 100 heating and cooling cycles. These findings demonstrate that surface geometry provides a practical approach for improving the effective thermal contact performance of thermal pads.