Joining Plastics, Metal and Ceramics via Laser
An essential element of the so-called Liftec process that was developed at the Fraunhofer Institute for Laser Technology ILT is a component made of a material that has a higher melting point than the plastic to which it is to be joined. By absorbing laser radiation, this component is heated to a temperature above the melting point of the plastic. The component is then pressed against the plastic part mechanically. As a result, the plastic softens due to conduction of heat, allowing the non-plastic component to penetrate the plastic material. With selection of suitable component geometries, a firm, positive connection is created upon cooling.
Because of the high energy density of laser radiation, localized and rapid heating of the metal component is achieved. If the thermal radiation from the components is measured with the aid of a pyrometer, the specifically required temperature for the materials involved can be established. This results in stress-free components, among other benefits.
Heating by means of laser radiation is almost independent of the thermal conductivity and electrical conductivity of the material that is pressed in. Thus, in addition to metals, other materials such as ceramics can also be joined with plastics. Fields of application for the process include, for instance, joining of plastic eyeglass lenses with the frame, providing not only improved product integrity and insurance against loosening, but also new design opportunities. Joining of plastic windows or facades with a metal frame represents another potential application. Here, too, a high-strength, leak-proof joint can be achieved.