Parameter study influencing thermal conductivity of annealed pure copper coatings deposited by selective cold spray processes

When two copper splats are in contact, a resistance to heat transfer exists between the splats. In thermal spraying, the conductivity of the coating is mainly reduced by non-metallic bonds at internal interfaces and trapped oxides. In cold spraying, however, almost no oxidation occurs during spraying. To demonstrate the capabilities and advantages of Cold Spray for the manufacturing of a conductive copper coating, the present study is focused at comparing the different processing methods in the as-sprayed and the annealed state. As a result, the coatings sprayed with spherical copper particles showed superior thermal conductive characteristics than coatings sprayed with non-spherical particles. There was a critical annealing temperature giving the maximum thermal conductivity. Up to a critical temperature, the annealing process enhanced the thermal conduction between adjacent splats. But, over that temperature, the voids in the coating rearrange and concentrate along the grain boundaries.