Laser welding of glass now ready for industry

21 Jul 2016

Femtosecond laser system developed by Trumpf enables economical, high-quality glass welding,

Achieving economical, high-quality laser-welding of glass has long posed a major challenge for materials processors, according industrial laser and toolmaker Trumpf.

But now the laser specialist has developed a femtosecond laser system that replaces conventional glass joining processes such as glueing.

The advantage of the new approach is that, in contrast to glueing, no additional materials that could be susceptible to evaporation or embrittlement are required. This means reduced costs and increases the durability and stability of the seam.

Trumpf commented that the nature of glass poses considerable challenges with regard to processing: glass is hard and brittle, has lower thermal conductivity than metal and tends to crack when heated unevenly due to the internal tension developed. Femtosecond laser systems can prevent such cracking. Elke Kaiser, applications engineer at TRUMPF, said, “The laser system must permit variable programming of pauses and pulses.”

How to laser process glass

In its statement about this new approach, Trumpf explained how the femtosecond laser system can process glass successfully: “Glass is permeable to light with wavelengths ranging from ultraviolet to near infrared. Absorption takes place only when the energy densities are high, so that processing within the glass is facilitated. The highest performance density lies deep in the lower glass at the focal point. The energy from several thousand laser pulses creates a melt pool which is pushed upwards in a few milliseconds. Skillful thermal management and an optimal ratio of pulses and pauses are necessary to prevent the glass from cracking.”

Laser-welded protective caps

Glass components that were previously glued to each other can now be economically welded with high-quality results, as Trumpf has demonstrated in its own production of laser light cables.

Until recently, the lids of the protective caps for the laser light cables were glued on. Now, lasers are used to weld them on. The joint strength of the glass parts depends primarily on the level of pulse energy. For example, the pulse energy for 1030nm infrared light needs to be 9 microjoules.

Trumpf is currently building a laser-welding system for reliable glass welding for mass production of the protective caps for the laser light cables in its own production plant in Schramberg. Elke Kaiser commented , “The laser system also serves as a pilot system to demonstrate to potential users that new laser methods are reliable and ready for deployment in glass processing.”