The aim of this study was to investigate the usefulness of the laser welding technology for the realization of wire connections: semiconductor structure-outer leading in power devices. Laser technology can be alternative to the traditional ultrasonic method of bonding, applied in power devices (for example IGBT transistors). The bondings made by ultrasonic method have adhesive nature and therefore are more susceptible for the damage than laser welded joints. A laser beam of a wavelength of 1.06 μm was applied in the new method of leads joining. Nickel was used as a material for wire leads and an intermediate plate (Molybdenum) between semiconductor structure and wire was placed additionally. The wire was welded directly to this plate. In this paper the thermo-mechanical properties of these bonding will be presented. Two fundamental problems will be discussed: thermal stresses, induced during laser welding, which have influence on the behaviour of the joints, and thermal state of the finished leads during conducting great currents, typical for the work of the power devices. The results of experiment investigations and results of computer modeling will be also presented.
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