Metal powder bed fusion of pure and coated copper for power electronics applications using a green laser

Automotive power electronics for electric vehicles contain small functional structures, preferably made of copper, which are built on sensitive ceramic-based direct bonded copper (DBC) substrates. An innovative additive manufacturing (AM) approach is presented, leveraging the laser powder bed fusion process (PBF-LB/M) for manufacturing these structures directly onto the DBC. This reduces manufacturing cost and effort by eliminating separate pick-and-place and joining processes. Interface characteristics between DBC and AM structures, which have not been in the focus of research so far, become important. Laser-based processing of copper poses a major challenge due to its reflectivity and thermal conductivity. Additionally, using a DBC in the PBF-LB/M process results in complex multi-material interactions. To increase the absorptivity of the copper, a green laser (wavelength λ ≈ 515 nm) is used. Additionally, pure copper is compared to modified copper with graphene oxide coating. Within the parameter study, an influence of the process parameters on the part properties was identified. For pure copper, only a small process window, requiring high laser powers and low scanning speeds, can be used for manufacturing high-density structures. The graphene oxide coating improves the absorptivity, allowing processing with lower energy input and a broader process window. However, with the application in focus, it must be emphasized that the AM structure as well as the DBC, can be affected detrimentally. Excessive energy input can damage the ceramic of the DBC causing cracking, eventually further limiting the robust process window. Still, suitable parameter sets were identified. • LPBF approach for manufacturing of functional structures for power electronics. • Processing of pure and graphene oxide coated copper with a green wavelength laser. • Interface characteristics between AM structures and ceramic-based substrate. • Successful manufacturing of high-density structures out of pure copper. • Shift in and extension of the process window for copper with graphene oxide coating.