Fabrication of metal-ceramic substrates by laser powder bed fusion using a high-power green laser and high temperature preheating

With the increasing demand for customized products, new requirements on production processes are set. Additive manufacturing with its tool-independent character shows great potential to replace conventional manufacturing processes. This also applies to power electronic assemblies, which are currently produced with a low variety of variants in large batches. However, high-quality processing of copper is a prerequisite for power electronics applications in order to achieve low power losses and long module lifetimes. Green high-power lasers show great potential to process pure copper powder by means of powder bed fusion using a laser-based system (PBF-LB/M) and open up new opportunities in power electronics production. PBF-LB/M not only facilitates the production of mono-material components such as load connectors or heat sinks but also provides multi-material capabilities, enabling 3D metallizations on ceramic substrates for use as power electronic circuit carriers. Therefore, parametric studies on the fabrication of copper metallizations via PBF-LB/M on alumina substrates using a 1 kW green laser have been conducted and are summarized in this paper. At first, the beam-matter interaction between preheated alumina substrates and parameterized laser radiation was analyzed. Based on the results, process parameters have been defined, which were then used for the production of copper metallizations. High temperature preheating of the ceramics was applied in order avoid delamination effects due to thermomechanical stresses during solidification. In parametric studies with respect to laser power, laser velocity and hatching distance on 500 degrees C preheated substrates, electrical conductivities of 30 MS/m and shear strengths of 69 MPa were obtained.