Direct Metal Coating of Injection Molded Parts
Using a newly developed metal injection unit, it is now possible to apply metal structures to plastic parts directly in the injection mold. This could significantly shorten the process chain for production of electronic components.
Working together with the Krallmann Group and KraussMaffei Technologies GmbH, the IKV, Aachen, has developed a process that combines metal die-casting with injection molding of thermoplastics. This process is called integrated metal-plastic molding and is expected to simplify production of plastic parts with integrated electrically conductive regions.
A special metal injection unit attached directly to the injection mold is used to process the low-melting-point alloys. The unit holds a hot pot with a dispensing plunger to which small bars of tin solder are fed. Because of their low viscosity, the metal alloys can be processed in the liquid state with almost no pressure. The metal is molded onto the plastic part directly through a temperature-controlled needle shutoff nozzle. Use of a special temperature control technique allows delicate circuit structures to be applied to the plastic surfaces without damaging the plastic substrate.
The process can be performed with a 3-station indexing plate mold, for instance. At the first station, the plastic circuit carrier is produced. At the second station, the metal is applied to the plastic carrier. At the third station, the metallic circuit trace is overmolded with a second plastic component and in this way electrically insulated.
Compared to previous methods, this technique shortens the process chain for production of electronic components. Equipment for producing metal components or lead frames can be dispensed with, for instance. The process also eliminates the need for additional assembly equipment. In addition, the logistics costs for individual parts are reduced. By shortening the process chain, part quality is improved further. Integrated metal-plastic molding offers great freedom when designing components and reduces the space needed for conductive components.