Expansion matched heat sinks made by µ-metal injection molding

There is an ongoing and increasing interest in using expansion matched micro-channel heat sinks for high-power diode laser bars. In this new approach the heat sinks are produced by µ-metal injection molding (µ-MIM). Unlike conventional heat sinks which are made of copper, these particular heat sinks are made of copper-tungsten because it combines two of low coefficient of thermal expansion (CTE) and reasonable thermal conductivity. Manufacturing heat sinks with the µ-MIM process allows for an economic mass production of complex micro near net shape parts. Especially when manufacturing over 10,000 parts with the µ-MIM process, manufacturing cost per part reduce considerably. The main goal is to use the opportunities µ-MIM offers. That means producing complex parts, which have a matched CTE in this case to gallium arsenide (GaAs). Therefore a material which combines high thermal conductivity behavior with a low coefficient of thermal expansion is needed. An additional advantage of the µ-MIM process is that the needed green bodies of the heat sink can be joint together in a co-sintering process. In this paper the current status of production of heat sinks with microstructured surfaces by µ-MIM for thermal management applications are presented. The range of operation and the limitations are outlined with special concern regarding the materials and the minimal structure size. The implication and advantages of using ultrafine powders are emphasized. Therefore sintering behavior, microstructure of sintered parts and characteristic properties as density, CTE, thermal conductivity and electro-optical characterization are shown identified.