Microwelding of plastics by fiber laser

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					                                          Microwelding of plastics by fiber laser




                                                                                                   The application of an innovative irra-
                                          Task                                                     diation strategy for introducing the
                                                                                                   energy is required, as the intensity
                                          In recent years, laser-beam welding                      of the focused fiber laser beam
                                          of plastics has become an established                    (106 W/cm2) is much higher than the
                                          processing technique for many indus-                     usual values for plastics welding
                                          trial applications. It has limitations,                  (300 W/cm2). By using a highly dynamic
                                          however, with respect to weld seam                       rapid circular movement along the
                                          width and operating speed. New deve-                     direction of feed, welds can be made
                                          lopments in medical and biotechnolo-                     without destroying the material even
                                          gical microsystems have increased the                    at great intensities.
                                          requirements which have to be met in
                                          the laser welding of plastics. The widen-
                                          ing of the range of materials used in
                                          microsystems engineering to include                      Results and Applications
                                          plastics has both opened up new pro-
     500 µm                               spects and created new requirements                      With the new irradiation strategy and
                                          for innovative concepts and methods                      use of the fiber laser, microfluidic com-
                                          that can be applied.                                     ponents made of PMMA and PC can
                                                                                                   be sealed along the complex weld con-
                                          Production techniques are required                       tour with a laser output as low as 3.5
                                          which will enable plastics to be reliably                W and an operating speed of 2 m/min.
                                          welded at geometries of 100 µm. On                       The width of the weld seam is less
                                          the basis of a fiber laser and an inno-                  than 500 µm, and a cycle time of
                                          vative irradiation strategy, a new tech-                 below 6 s can be achieved with cor-
                                          nique has been developed for the laser                   responding scaling of the process para-
                                          welding of plastics.                                     meters. On the polycarbonate samples,
                                                                                                   weld seams with a good visual appea-
                                                                                                   rance can be produced at an output
                                                                                                   of 8 W and a feed rate of 18 m/min.
Above: Light-microscope image
of two 120 µm-wide weld seams             Method                                                   The weld seam width can be reduced
on a sample of polycarbonate.                                                                      to 100 µm. The new process has great
Below: Welded microfluidic com-           In the tests, a fiber laser with a wave-                 potential for use in the large-scale pro-
ponent made of PMMA with a
complex channel structure.
                                          length of 1112 nm and a maximum                          duction of microfluidic components.
                                          output of 9 W is used as the beam
                                                                                                                                                         Subject to alterations in specifications and other technical information. 04/2007.
                                          source. Thanks to its excellent beam
                                          quality of M2 < 1.1 a focus diameter of
                                          30 µm can be attained for a working                      Contact
                                          distance of 100 mm.
                                                                                                   Dipl.-Ing. A. L. Boglea, Tel.: -217
                                                                                                   andrei.boglea@ilt.fraunhofer.de
                                                                                                   Dr. A. Gillner, Tel.: -148
                                                                                                   arnold.gillner@ilt.fraunhofer.de




                                          Fraunhofer-Institut für Lasertechnik ILT                 Director: Prof. Dr. rer. nat. Reinhart Poprawe M.A.
                                                                                                   Vice Director: Prof. Dr. rer. nat. Peter Loosen
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