Process studies on copper laser beam welding over gap by using disc laser at green wavelength

Abstract

The increasing demand for the substitution of the internal combustion engine vehicles to the battery electric vehicles requires beside battery cells high performance power electronic devices such as power control units (PCU). However, a combined requirement of high junction temperature stability and a large joint area of the interconnection on the PCU is a challenge for the conventional joining method such as soldering and wire bonding process. The Laser Impulse Metal Bonding (LIMBO) process enables a high temperature stable weld joint and large joint area. During the LIMBO process only minimized thermal stress is induced into the underlying substrate by a spatial separation between both joining partners in an overlap configuration with a gap. Hence, an energetic separation between the melting and joining phase is given.In this paper, the LIMBO process is firstly investigated with the disc laser at wavelength λ = 515 nm. Due to the enhanced absorptivity of the laser beam at this wavelength on copper material, the process duration of the LIMBO process is about the half compared to the LIMBO process with wavelength λ = 1064 nm.