The paper describes thermo-mechanical problems of the soldering process, which is used to interconnect single solar cells with each other, in order to create a photovoltaic module. The interconnection wires need to conduct high currents, because of the demands for high power modules that operate at low voltages. Therefore the resistance of the wiring is a very critical factor, because it influences strongly the total module efficiency. However significant mechanical problems are created by increasing the width and height of the rectangular wires, because the brittle silicon solar cells are prone to breakage. Therefore innovations in interconnection design are necessary to release mechanical stresses during the assembly process.