Composite diamond heat spreader

Sumitomo Electric Industries, LTD. (SEI) is developing inexpensive and high performance heat spreaders which comprise of CVD diamond and silicon substrate (composite diamond heat spreader). By using finite element method (FEM) analysis, we present characteristics of the composite diamond heat spreader. The calculational results indicate two advantages about the composite diamond heat spreader: (1) A composite diamond heat spreader that consists of very thin (20 μm) CVD diamond film exhibits a considerable heat spreading effect, which is equivalent to thermal conductivity of 300 W/m.K. (2) The composite diamond heat spreader shows a higher coefficient of thermal expansion (CTE) than that of bulk CVD diamond. Thus, adopting diamond/silicon structure brings better thermal expansion matching between the composite diamond heat spreader and laser diode (LD), such as gallium arsenide (GaAs) or indium phosphide (InP). The production process of the composite diamond heat spreader is proposed. Since the production cost of CVD diamond is proportional to its thickness, the result of the FEM analysis that states very thin diamond film shows a better heat spreading effect than conventional materials is a great advantage and the deposition cost of very thin (≤ 20 μm) CVD diamond film can be reduced. The production cost of the composite diamond heat spreader is considered to be comparable to those of conventional heat spreader materials, such as AIN and CuW.