Additive Manufacturing of 3D-copper-metallizations on alumina by means of Selective Laser Melting for power electronic applications

In the power electronic sector thick metallizations of the substrates are required to ensure high current carrying capabilities. In order to guarantee an optimal thermal dissipation, ceramic substrates are state of the art and commonly used. In general, LTCC, HTCC, DBC or AMB technologies are used for fabricating circuit carriers in firing processes for power electronic applications. Those technologies however need subsequent process steps like structuring, etching and washing that are cost intensive and have a negative environmental impact. Moreover, the flexibility of those technologies for prototyping, small-batch productions and special requirements is limited. In this context Additive Manufacturing (AM) can provide a solution for those constraints. This study reveals the benefits of the generative manufacturing process such as material efficiency, product customization/-flexibility, elimination of the usage of tools, constructional freedom and less process steps in contrast to the conventional fabrication methods of ceramic substrates. The present paper illustrates further investigations in manufacturing thick copper structures (700 um) on alumina with the usage of the Selective Laser Melting (SLM) technology. Observable delaminations due to high tensions within the selective laser melted metallization could be eliminated by heating the build platform up to a substrate temperature of 250 °C and a reduction of residual oxygen in the process chamber to 5 ppm. As a final demonstrator, 3D-structures like load connections and bridges on 750 um thick SLM-copper-metallizations on alumina, free of delaminations and oxidations could be manufactured.