Soldering
Fiber-coupled diode sources for selective laser soldering
Soldering joins components with a filler alloy that melts below 450 °C, without melting the base metals. With a laser, energy is delivered without contact, locally and with precise control in time and space, which reduces thermal stress compared with iron or wave soldering [1]. There is no tip wear, hard-to-reach joints become accessible and heat-sensitive components are protected.
Selective soldering in electronics
Lasers solder through-hole (THT) and surface-mount (SMD) components, flexible circuits and connectors, either one by one or quasi-simultaneously with a scanner. They are also used in photovoltaic modules and automotive electrical connections [1]. Diode lasers between 790 and 980 nm are the preferred source thanks to their efficiency, with the alloy supplied as wire, paste or preforms [1].
| Parameter | Reference values in the literature |
|---|---|
| Wavelength | 790–980 nm (diode) [1]; 1070 nm (fiber) [2] |
| Power (CW) | 2–80 W depending on joint size; 30–80 W for most applications [1] |
| Spot diameter | From ~50 µm in dense packaging [1]; 0.1–1 mm in quasi-simultaneous soldering [2] |
| Alloy | SAC305 (Sn96.5Ag3Cu0.5), lead-free [2] |
| Power ramp | 1–2 s per joint depending on the component [2] |
| Thermal load on the component | ~150 °C maximum on the underside, for less than 3 s [2] |
Closed-loop temperature control
Absorption changes during the process: solid alloy, molten alloy, the copper pad and the component lead all absorb differently. Power is therefore regulated with a pyrometer that measures the joint temperature and adjusts the emission in real time [1, 2]. With high-frequency pyrometric control, crack- and pore-free SAC305 joints have been obtained on temperature-sensitive components [2].
Our sources
We design and manufacture near-infrared fiber-coupled diode bars, with powers from a few watts to hundreds of watts and a range of core diameters, and with external power control for integration with temperature measurement systems.
References
1. Ezeonu SO. Laser soldering. En: Mastai Y, editor. Materials Science – Advanced Topics. IntechOpen; 2013. doi:10.5772/51527
2. Ermer J, Saffer J, Schaumberger K, et al. Qualification of a system technology for selective laser-based quasi-simultaneous soldering with an integrated pyrometric process control. Procedia CIRP. 2020;94:622–626. doi:10.1016/j.procir.2020.09.093
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