Effective microstructuring of sensitive components by USP processing
Laser structuring with an ultrashort pulse laser is particularly suitable for join partners with a high thermal sensitivity. With thermal penetration depths in the range of a few micrometers an USP laser structuring allows to roughen the contact area without damaging the deeper layers of the material. Depending on the material, several structure types are possible: for example a deterministic structuring with a ditch or pattern structure inceases the contact surface efficiently and provides a better bonding with the join partner for the glue. By adjusting the laser beam to the workpiece oblique drillings can be included by special procedures, which lead to a better grip of the fusion. For metalic materials, in particular steels, aluminium or titanium, a statistical structure can be used. These so called Cone-like-protrusions (CLPs) are created during the USP processing by a self assembly effect. It results in a hierarchical structure in the range of micrometers superimposed by nanostructures. In addition to an approximately fivefold to tenfold increase of the surface, these CLP structures have undercuts. For example in the thermal fusion process with plastic, the liquid plastic can flow into these undercuts of the metalic surface, harden there and from a fixed anchor point. This effect can also be used effectively with adhesive bonds.