Effect of talc on the metal adhesion of laser-structured polymer parts

Mechatronic integrated devices (MID) enable the combination of electrical, mechanical, thermal and optical functions within one component. The three-dimensional circuitries can be applied to a polymer substrate by means of LPKF laser-direct-structuring (LDS). For this, the matrix polymer is filled with a special additive, enabling laser activation and subsequent metallization. In order to reduce the thermo-mechanical stress in the polymer-metal composite, high levels of inorganic fillers are added to the polymer compound to improve its coefficient of thermal expansion. At the same time, the fillers affect the metallization behavior as well as the metal adhesion as a key property for the reliability of MID. In this work, the extent to which talc affects the adhesion of the metallization was investigated by the hot-pin-pull-test. An increase in the metal adhesion was achieved by adding varying amounts of talc platelets (diameter 7 μm) to a PA10T-based copolyamide filled with 4 and 8 wt.-% LDS-additive. The specimen were further characterized using a scanning electron microscope (SEM). The results indicate that the increased adhesion is caused by mechanical anchoring of the metallization among the protruding talc platelets.