In this work we present the results on a reliability study on SMD components mounted on an organic power electronics substrate. The substrate technology has been developed to meet the needs of high ampacity and thermal conductivity with an organic substrate material. Therefore a thick structured copper core was introduced throughout the entire substrate size (see fig. 1). On top of the copper core common FR4 multilayer structures are realised to create a typical SMD PCB surface. The bottom of the copper core was covered with one prepreg with a high thermal conductivity and one copper layer to be able to connect to a heat sink. The copper core becomes structured to enable the use as the layer for conducting high currents. Therefore insulation trenches were manufactured and plugged with a polymer.