Characterization of laser powder cladding for fast, flexible and direct generation of conductive structures on three-dimensional ceramic substrates [CERACLAD]
Duration: 06/01/2023 – 05/31/2025
The main objective of the CERACLAD research project is the direct generation of conductive structures from graded copper/copper-phosphorus systems on technical ceramics without upstream and downstream process steps by means of DED-LB/M. The copper-phosphorus material is to be used as a base layer on the ceramic due to its good wetting behavior. For high electrical conductivity, pure copper is applied in further layers. In the DED-LB/M process, two conveying lines can be continuously combined for this purpose and materials can be mixed in the process zone. The processing of CuP is additionally investigated in the PBF-LB/M process to determine the adhesion mechanisms. An infrared laser beam source is used for both processes.
For the further development of MID technology for reliable application in higher power classes and the development of new application possibilities, the qualification of a process for the fast, flexible and direct generation of conductive 3D structures is necessary. Therefore, the CERACLAD project will investigate whether the technical challenges mentioned above can be overcome by laser powder cladding (DED-LB/M) for the direct, flexible and tool-free production of conductive tracks on planar and 3D substrates for power electronics. A key aspect of investigation here is the adhesion mechanism of welded graded layers of copper/copper-phosphorus material systems. Based on preliminary investigations, the adhesion mechanisms are to be investigated and transferred to the DED-LB/M by means of metallization investigations using laser powder bed welding (PBF-LB/M) on planar substrates. For electrical functionalization, a copper layer is then welded onto the copper-phosphorus metallization in the DED-LB/M process. A low melting point copper-phosphorus material with good laser weldability is used in the interconnect zone. In consecutive material layers, the phosphorus content is reduced in order to maximize the electrical conductivity when graded with pure copper.
In this context, the scientific and technical challenge is, on the one hand, to add structures of copper/copper-phosphorus materials with high adhesive strength and variable structure widths between 700 μm and several millimeters to the surfaces of the selected ceramic substrates by means of DED-LB/M. On the other hand, it is necessary to develop a new method of additive deposition. For applications in power electronics, powder adhesion next to the conductive path must also be minimized, e.g. by powder overspray to increase the electrical dielectric strength between individual conductive paths, and the surface topology must be optimized for solderability and bondability in subsequent process steps. Both of these issues were identified as challenges in the CLADMID project . Second, adhesion of the metallization to the ceramic is critical. One challenge is the initial, punctual thermal stress on the ceramic as a result of the selective energy input by the laser beam, which creates a high temperature gradient. To avoid destruction of the ceramic and to achieve high bond strengths, preheating is used in the PBF-LB/M process. This reduces the required energy input of the laser radiation to put the ceramic into a molten state, which is decisive for good bonding .
In this context, in the project applied for here, it is to be ensured in the direct process of laser powder buildup welding (DED-LB/M) by a temporal and a spatial modulation of the introduced laser beam power that sufficient energy is introduced and accumulated both in the ceramic substrate and in the copper powder material by the laser beam.
Benefits for SMEs
The research results of laser powder cladding on ceramics can help small and medium-sized enterprises to increase their competitiveness. The direct generation of conductive structures shortens the process chain and manufacturing costs. The additional high performance offers the company, if successfully industrialized, an opportunity to position itself as a technology pioneer and thereby differentiate itself from the competition. Alternative processes for additive metallization of ceramics are currently still being researched and have not yet been industrialized. The individual costs of ceramic 3D-MIDs are relatively low due to the short process chain and low tooling costs and enable flexible and fast customization, which is an additional advantage with ever shorter product development times and individual manufacturing requirements. The low cost of change and the advantages of the technology can help strengthen the profitability of companies and consolidate their position in the market.