Reliability of Molded Interconnect Devices Regarding Crack Initiation and Overmolding

The reliability of Laser Direct Structured Molded Interconnect Devices (LDS-MID) under harsh environmental conditions is the limiting factor of the MID technology. Various factors influence the crack initiation of LDS-MID conductor tracks. In order to investigate and quantify the effects of diverse influences, a Design of Experiment (DoE) is topic of current research. Based on the results of this, the applicability of MID technology for automotive industry is being tested in the form of simplified sensor modules for engines and transmissions. Therefor specimens with optimum process parameters are overmolded using the same thermoplastic material as the substrate. All specimens are subjected to temperature shock tests using the temperature profile prescribed in automotive industry. In order to detect micro cracks within the conductor tracks, the electrical resistances are permanently recorded and evaluated by means of online four-terminal sensing. The Coefficient of Thermal Expansion (CTE) of the substrate and its surface roughness after laser structuring were identified to yield significant effects on reliability of MID. Furthermore, there is a risk to initiate cracks by overmolding. This work shows that MID are suitable for applications in automotive environmental conditions and that significant optimization potentials lie in the coordination of the manufacturing process parameters.