Thermoplastic encapsulations of a sensor platform by high-temperature injection molding up to 360°C

For bioprotective encapsulated Internet of Things (IoT) electronics for the medical market, especially for cost-effective, single or multiple use, injection molding will be of major importance. The stresses from the production process pose special challenges for electronics. The aim of the study was the simulative and experimental characterization of the load spectrum from the injection molding process and its effects on electronics. General recommendations for the encapsulation of IoT electronics in polymer matrices were derived. A microcontroller-controlled temperature sensor board and a suitable injection mold were developed. Eight circumferential NTC-sensors measured the prevailing thermal load directly on the component during overmolding. A simulation model allowed statements on the loads to be made about individual components, validated in experimental tests. In addition to PP and PMMA, PSU with a melt temperature of 360°C was tested. The temperature influence of the melt could be described as a function of the component position. The loss of adhesion, shrinkage, distortion, cavities, and delamination were analyzed using micrograph analysis. Complete functionality of the electronics was ensured after encapsulation. Optimization strategies were developed for the design of both IoT electronics and the injection mold. Novel concepts such as interlayer or backfill vias could be derived for future research approaches. POLYM. ENG. SCI., 59:1315–1331 2019.