Laser joining method and laser joining device for fusing workpieces

A laser joining method for bonding different workpieces made of plastic material, or plastic material together with other materials, a first workpiece facing a laser source being made of a material transparent to a laser beam and a second workpiece being made of a material absorbent to the laser beam, or a material that is transparent to the laser beam and includes an absorbing coating or an absorbing intermediate film, so that bonding contact faces of each of the first and second workpieces abutting one another melt under the action of laser light and bond to one another during a subsequent cooling process under pressure application, the workpieces to be bonded being pressed against one another by a clamping device for pressure application, for which purpose the workpieces are disposed between a support element and a clamping element, to which a clamping force can be applied and which extends across the first workpiece and is substantially transparent to laser light, and a mask having mask structures being used, which allows laser light to pass only in a region of the bonding contact faces so as to plasticize only the bonding contact faces on the second workpiece, the mask structures being larger than the wavelength of the laser beam used, and the laser beam being either line-shaped and moved relative to the workpieces and the mask, or being areal and directed in a stationary manner at the workpieces and the mask, and the clamping element being adapted, on a bearing side thereof for the first workpiece, to a first contour side of the first workpiece,

• wherein at least the first workpiece facing the laser source being formed by a three-dimensional molded part, in which the first contour side facing the clamping element is non-planar such that the first contour side of the first workpiece includes at least one peak and includes at least one valley at a lower elevation than the at least one peak, and
• wherein the mask structures are created on the bearing side of the clamping element facing the first workpiece such that at least one of the mask structures is at a protruding portion of the clamping element that is adapted to be received in the at least one valley of the first workpiece to thereby enable pressing and bonding of the first workpiece to the second workpiece by forming at least one of the bonding contact faces at a location that corresponds with the at least one valley of the first workpiece.