The importance of alternative drive systems in the automotive industry increases with regard to emissions and the costs of mobility and transport. At Daimler, special emphasis is placed on the development of vehicles with fuel cells or hybrid propulsion. The automotive industry sees in a hybrid drive a combination of a conventional internal combustion engine and an electric motor powered by a battery. The rotor of a electric motor consists out of a defined number of sheet packages which individual sheets are previously punchned under immense sheet scrap. To minimize this, the concept of the segmented rotor ring has been developed. The challenge in the implementation of the rotor segmentation are the high requirements in strength and tolerance on the joints. In this paper the development of joining technology joint geometry has been described. To satisfy these requirements, different basic geometries were investigated for their potential. This was done through the establishment of significant simulation models and their validation with tensile tests. From the T-slot geometry the fir-tree geometry is emerged under a gradually developing. Due to the development of a defined parameter optimization method combined with a design optimization, the geometry of a fir tree was developed into a highly resilient joint geometry, which was confirmed by tensile tests. The implementation of the fir tree on the rotor geometry was carried out considering the geometrical and punching technical limitations. The implementation and evaluation of the centrifugal tests showed a correlation with the results of the tensile tests. The next step are tensile and centrifugal tests at high temperatures in order to ensure the joining strength in every situation. The execution of fatigue tests is necessary to detect potential vulnerabilities and to guarantee the operational stability. As a final step towards production stage the ability to automate the joining process must still be investigated and developed.