Laser micro welding of conductive materials like copper has always been somewhat of a difficult proposition due to copper’s high reflectivity at the 1064nm wavelength. 532nm “green” laser welders however, remove this barrier, offering a truly viable method for laser micro welding copper (and other conductive materials) in high volume.
Why is this so important? Well, as part miniaturization continues, and connector sizes decrease below 0.004-inches thick for flat ribbons and wire diameters, the traditional processes we used to use – like crimping, soldering and brazing – become less viable due to high joint resistance, questionable joint reliability, and longevity. By contrast, welding, which provides excellent joint integrity, longevity and conduction performance, is quickly becoming the required standard.
Some of the applications I can think of that would really benefit from this approach include:
- Flat ribbon to thick film metalized pad
- Wire to metalized pad/terminal
- Side by side square terminal to round wire
- Flat to flat lead frame connections
- Miniature lithium ion/polymer battery connections
- Micro welding of dissimilar materials
The real challenge of micro welding copper, however, is how to control the heat balance in these small and highly conductive parts to enable welding while eliminating over- or under-heating. Using the 532 nm (green) wavelength is one way of meeting this significant challenge. Reducing the wavelength from 1064nm to 532nm significantly reduces the reflectivity of copper and other conductive materials. The 532nm wavelength enables consistent coupling into the copper and stabilizes welding. For those with experience of laser welding, the green laser welds copper like a 1064nm laser welds steel.
LW5AG Green Laser Welder Welding Copper Green Laser Welded Copper Bus Bars
A word of caution for those looking to adopt the 532nm technology for micro welding: there are mixed wavelength lasers on the market that use 532nm to couple into the part, and then use 1064nm to provide the weld energy. This does not work well for micro welding applications where consistent absorption during the weld is key to providing weld quality and repeatability. In addition, this set up offers no independent control of the 532nm wavelength because it is linked to the 1064nm.