Green laser welds gold and copper

Laser welding specialist Miyachi has introduced a green laser device, which it claimed was the first laser welder able to consistently join gold and copper.

Intended for electronics, medical and semiconductor manufacturers, the ML-8150C welder can be used to join wires and sheets, for example welding gold wires to integrated-circuit lead frames and copper wires to PCB substrates, the company said.

It added that these metals have been difficult to laser-weld because they have high surface reflectance, especially towards the laser colours commonly used in welding. However, they absorb ore strongly in some parts of the spectrum, in particular green light. In trials, laser penetration into three layers of 0.5mm, non-coated CuSn6 (copper alloyed with 6% tin) was measured at 1.26mm, effectively welding together all three sheets.

The new welder uses a second-harmonic generation scheme to double the laser light frequency, taking it from a wavelength 1064nm to one of 532nm, ie. green light. This increases the energy absorbed by the metals by between 4.5 and 20 times, Miyachi said. It added that improved beam definition, coupled with higher power, also raises the energy density of the laser by some nine times, compared to its earlier product in this sector.

The ML-8150C has a maximum rated output of 5W, with energy of 4 J/pulse in pulses of 0.2 to 5ms, and a repetition rate of one to 30 pulses/sec. Peak power output is 1.5 kW.

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