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Microwelding by fibre laser

The Fraunhofer Institute for Laser Technology has developed a contour-welding method for microsystems.

Medical products and components in the bio-engineering and bio-analysis sector have to be made from highly bio-compatible materials and the joining method employed has to meet special requirements. It has to get by with as few additive materials as possible, and should under no circumstances influence or contaminate the materials. As an alternative to conventional joining techniques, laser welding offers a number of innovative solutions featuring high welding speeds, narrow weld seams and special process variants for joining transparent plastics.

A series of new beam sources enables laser characteristics to be specially adapted to these tasks. Highly advanced microsystems with complex welding contours for medical engineering and biotechnological applications, such as a new type of microfluidic chip with very narrow and closely spaced channels, make great demands on joining technology. The new chip has to be furnished with a cover film, for which the welding seam must be no more than 100μm wide.

The new TWIST (Transmission Welding by Incremental Scanning Technique) contour-welding method developed by the Fraunhofer Institute for Laser Technology ILT meets these stringent requirements, producing high-quality welding seams at high process speeds.

Based on fibre lasers, this irradiation method can produce 100μm-wide seams at a rate of up to 18m/min.

Any potential degradation of the material due to the high intensity of the focused fibre laser light is avoided in the new process. For the welding of transparent plastics, the new beam sources enable the laser characteristics to be adapted to the polymers’ absorption behavior, thus obviating the need for additional absorbers. This improved irradiation strategy preserves the advantages of laser transmission beam welding without influencing the surfaces of the components. It can be used for transparent and translucent polymers.

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