Effect of fillers on the metallization of laser-structured polymer parts

Abstract

Abstract Molded interconnect devices offer great potential as a substitute for circuit boards, especially regarding three-dimensional shaping and functional integration. Applying circuits to polymer substrates can be performed by means of LPKF laser direct structuring® (LDS). There, the matrix polymer is filled with a special metal additive, enabling laser activation and subsequent metallization. Important effects emerge from additional inorganic fillers inside the matrix polymer, e.g. the (thermo)mechanical behavior and the processing properties. In this work, the degree to which inorganic fillers affect the quality of metallization is investigated. An increase in the plating thickness was successfully achieved by adding varying amounts of talc platelets (diameter 7 μm) to a PA10T-based copolyamide filled with 4 and 8 wt% LDS additive, in contrast to poor metal deposition adding only LDS additive. Additionally, talc and glass spheres with a diameter of 50 μm were used, leading to unsatisfactory metallization results. To explain this behavior, adhering LDS particles were found on the talc platelets with a diameter of 7 μm on the surface of the laser-structured specimen. The talc platelets and glass spheres of 50 μm were not available in sufficient dimensions on the surface and thus led to worse plating results.