Welding and Soldering with High Power Diode Lasers

The wide range of available wavelengths, high brightness and increasing reliability are breaking new ground for diode lasers. Material processing with high power diode lasers in industrial manufacturing is getting more and more important. In automotive, medical device and also solar cell production they are important tools for automated production. Closed-loop temperature control by integrated on-axis pyrometer and fast beam deflection units are established tools for flexible processes documentation and quality control. Depending on the operating conditions, diode lasers have proven to run for several years in production nearly free of maintenance. High Power Diode Lasers New semiconductor material delivers more laser power per bar. InGaAlAs based chip material at a wavelength of 808nm has shown up to 170 W laser power with an efficiency of more than 60 %. [1] With InGaAs based semiconductor material at 940nm optical power of up to 200 W seems to be achievable. Such highly efficient chips allow the increase of output power of diode stacks and modules without design changes. With high beam quality an efficient coupling into 200 m and 400 m fibers is possible [2]. Fiber coupled diode lasers are mainly used for materials processing (MP) and diode pumped solid state lasers (DPSSL). For industrial applications fibre coupled systems offer some significant advantages: Modular set-up for easy integration Separation between beam source and processing optics which allows plug & play exchange of the beam source during service Symmetric and homogeneous beam profile Customizing of beam size and shape at fiber end With higher laser power also for non-standard wavelength a large number of different applications can be addressed. InGaAs on InP substrates are used for wavelength >1300 nm with output power of 30 W. (AlGaIn)(AsSb) on GaSb substrates for >1800nm. In this wavelength range, high power means about 10-15 W per laser diode bar. Diode lasers are highly efficient and allow fast and easy modulation of the power level. Compared to other laser types, diode lasers convert the supplied energy (current) directly and immediately into laser radiation. This, for example, allows closed-loop temperature control of a welding process by using a pyrometer. The pyrometer is detecting the thermal radiation caused by the welding process and calculates the temperature of the welding spot (Figure 1). The pyrometer can be integrated into the processing head so that laser and pyrometer detector are coaxial and have the same field of view. 180 190 200 210 220 230 240 250 260 270 0 400 80