A user employing the assembly injection molding technique is able to generate mechatronic assembly groups of utmost complexity at high cost-efficiency and large freedom of design. Sensors represent one of the challenges involved when electronic assembly groups are to be integrated in an housing that is tight to media impact. To obtain a media-tight enclosure of assembly groups consisting of SMD components on FR4 circuit boards thermosets which allow for injection molding are increasingly applied.Operating temperatures are high and the coefficient of thermal expansion complies with that of the circuit boards. When inserts are to be overmolded, operators have to face various challenges. First, the melt must not cause thermal or mechanical damage to the overmolded components. Moreover, the coefficient of thermal expansion must be adapted to the board and the SMD components, to avoid damage to the components in case of temperature change loads. Filled plastics’ material properties are usually anisotropic. The present publication will include experimental process and material studies to show which impacts in terms of process and design must be taken into consideration, in order to minimize the load acting upon the insert when overmolded, as well as adapt, as far as possible, the coefficient of thermal expansion to the part to be overmolded. Moreover, the core temperatures obtained in an SMD component when overmolded with a plastics material, were determined. This serves to derive guidelines of component selection, concerning their junction temperatures. Excellent adhesion between plastic and circuit board is essential for media-tight encasing. Investigation has shown the effects exerted on the formation of adhesion by the soldering stop varnish applied, by the materials used for the circuit board, and also by the plastic used for overmolding. Epoxy resins have shown to generate mainly good adhesion, whereas thermoplastics allow for adhesion with FR4 circuit boards only in some cases. Various prototype studies like overmolding rpm sensors, LED pushbuttons etc. have shown that the system information mentioned is indispensable for well-aimed product development.