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R.M. German and J.L. Johnson, “Metal Powder Injection Molding of Copper and Copper Alloys with a Focus on Microelectronic Heat Dissipation,” Inter. J. of Powder Metall., vol. 43, no. 5, 2007, pp. 55-63.

 

Abstract

    Powder injection molding (PIM) has been applied to copper and copper alloys for several years. Many powder and process variants have been demonstrated, and recent work has been directed to applications associated with heat dissipation in electronic systems. This focuses attention on unalloyed copper with high thermal and electrical conductivity and on bronze for aesthetic non-structural uses. This paper provides a brief history of the field and the ensuing rationalization of the powder, process, and properties to the application. Fundamentally, PIM of copper requires a balance between the optimal processing options that deliver the desired properties and the conflicting dictates of low-cost processing. A key to success often is tied to oxygen control in the copper powder.

 

Conclusions

    None of the seven copper powders tested here emerged as clearly the best choice for PIM. All of the powders achieved from 93% to 96% of the pore-free density. The jet-milled copper powder had the lowest impurity level and gave the highest sintered thermal conductivity. The gas-atomized and 25 µm water-atomized powders had the highest solids loadings, which generally promotes ease of PIM processing; however, a less spherical particle shape is often preferred for component shape retention during debinding. Evaluation of the dimensional uniformity differences from these powders is a future task. Additionally, as PIM moves into thermal management applications the obvious cost issues arise as different powders and processing options are considered. However, it is clear that the foundation in powders, processing, and design are in place to make PIM copper a successful growth area.