Thermal stress and heat transfer characteristics of a Cu/diamond/Cu heat spreading device

Abstract

A Cu/diamond/Cu heat spreading device has recently been proposed. This work analyzes its thermal stress and the heat transfer of the diamond device using finite element simulation, to understand the dependence of the thermal stress and the heat transfer. The diamond device operates with a heat source at temperatures from 400 K to 600 K. With a 2 μm Cu top layer, the heat spreader consists of a diamond layer of thickness 40–300 μm and a bottom Cu layer of thickness 5–300 μm. The thermal stress in the diamond layer at the edge is maximal close to the substrate Cu layer, where a peeling point may be present. The thermal stress reaches saturation as the bottom Cu layer becomes thicker up to 60 μm and then does not increase further. The maximum thermal stress increases with the diamond thickness. Effective thermal conductivity increases with the thickness of the diamond layer. The heat transfer increases markedly with the increased thickness of the diamond layer up to 100 μm, heat transfer only slightly improves beyond the range of thickness. The diamond layer with thickness of approximately 100 μm provides greater efficiency of heat transfer than thicker diamond layer. Combining the increase of heat transfer and the contrasting increase of maximum thermal stress we suggest an optimal diamond layer thickness for the construction of a diamond device being of less than 100 μm.