A semiconductor package system comprises a semiconductor package and a cap. The semiconductor package comprises a die pad, a chip mounted or arranged to a first main face of the die pad and an encapsulation body encapsulating the chip and the die pad. The cap covers at least partly an exposed second main face of the die pad. The cap comprises a cap body of an electrically insulating and thermally conductive material and a fastening system fastening the cap to the semiconductor package. The fastening system extends from the cap body towards the encapsulation body or along a side surface of the semiconductor package.