On the influence of fillers on the quality of selectively metallized layers in polymers
Laser structuring processes such as direct structuring (LDS) according to the process principle of LPKF Laser & Electronics AG enable the application of three-dimensional circuitries to plactic substrates, also referred to as molded interconnected devices (MID). A metal complex in the substrate material is selectively activated by laser radiation and the resulting germs are electroless metallized. Laser structuring and metallization are influenced in many ways. Fillers in particular, which are added to the plastic to adjust its coefficient of thermal expansion to the level of the applied metal, influence metallization and coating properties. This affects both the starting and deposition behavior, which is reflected in the layer thickness and homogeneity, as well as the adhesive strength. In many cases, however, these influences are not yet fully understood.
The aim of this work therefore is to investigate the influence of fillers on the metallization. For this purpose, different filler types and shapes of defined contents are added to an aromatic polyamide. Furthermore the content of a specific talc type, as well as the content of LDS-additive are systematically varied. The plastic compounds produced in this way are further processed into test specimens by means of injection molding, laser structured and metallized. Subsequently, the metallization quality is characterised and evaluated based on the layer thickness and homogeneity. Related to this, the adhesive strength of the metallized layers on the plastic substrate is also examined. In addition, the investigations include a morphological analysis of the samples with regard to the distribution and orientation of the fillers. To evaluate the industrial applicability, the mechanical properties of the substrates are characterized additionally.
This should deepen the understanding of the process and thus contribute to an economic production of such components as well as improved reliability in use.