METALLIZED THREE-DIMENSIONAL CENTROSYMMETRIC MICROSTRUCTURES TO ENHANCE DRY CONTACT THERMAL CONDUCTANCE ACROSS NONFLAT INTERFACES
Various thermal interface materials (TIMs) are created to reduce contact thermal resistance between two surfaces; however, there is a clear need for dry contact thermal interface solutions at low pressure. We recently presented a novel dry TIM made of an array of compliant metallized zig zag microsprings (~100s µm tall), which are fabricated using projection micro-stereolithography (µSL) and electrodeposition processes. This dry surface coating allowed conformal interface contact at low pressures (10s-100s kPa) to reduce contact thermal resistance between surfaces with a nonflatness of ~5 µm. The asymmetric zig zag spring geometry is unable to remain in complete contact with the mating surface when compressed, which reduces the overall contact area with the opposing surface and hampers thermal performance. A newly designed hexagon spring geometry is presented herein to address this limitation of the previous design. Simulation of the spring behavior shows that the hexagon spring can remain in contact with the mating surface under compression, which is confirmed via experimental observations. The experimentally measured mechanical compliance shows reasonable agreement with the mechanical compliance predicted by the simulations. Thermal resistance measurements indicate that the thermal resistance of the hexagon spring array is unaffected by the presence of surface nonflatness.