Efficient Copper Micro Welding with Fiber Lasers Using Spatial Power Modulation

Joining of copper material in order to create a contact is an important task in electronics industry. Conventionally pulsed rod-based IR laser sources with low beam quality have a high energy input for welding copper due to large spot diameters. Fiber laser sources have high beam quality which allows small laser spots to be generated. Therefore, the threshold for deep penetration welding can be reached by using lower power. But when such small laser spots are used, the resulting connection area has to be enlarged. To achieve this, spatial power modulation has been introduced. The use of spatial power modulation—a linear feed with superposed circular motion—allows a significant expansion of process boundaries. The additional parameters of oscillation frequency and amplitude enable new strategies to control the laser welding process. This paper presents recent developments concerning process improvements and increase in efficiency by applying spatial power modulation. We discuss process regimes for spatial power modulation by analyzing the melt pool dynamic via high-speed videography. These regimes are an important aspect for process efficiency. Effects of heat conduction and spatial power modulation have been studied.