Evaluation of copper powders for processing heat sinks by metal injection moulding

Abstract

Powder characteristics that enable metal injection moulding of high conductivity copper heat sinks are investigated. Gas atomised, water atomised, oxide reduced and jet milled copper powders are characterised in terms of particle size, packing density, mixing torque and impurity content. The sintering kinetics and rate of oxide reduction are investigated using die pressed samples. Densities of 93 to 96% of theoretical can be achieved for all of the powders. Oxide reduction is complete by about 900°C. One of the water atomised copper powders is injection moulded to produce a demonstration heat sink. Thermal and electrical conductivities are measured and related to iron content and porosity. Overall impurity contents for typical powders are about 0·15 wt-%, resulting in thermal conductivities of 280 to 320 W m⁻¹ K⁻¹ for MIM copper.

Keywords:

• GAS ATOMISING
• WATER ATOMISING
• METAL INJECTION MOULDING
• HEAT SINKS
• CU POWDER