There has long been a desire to deposit conductive paths directly on molded plastic structures, combining the electrical and mechanical functions in one component to form an injection-molded circuit carrier. This technology has been accomplished by using the Laser Direct Structuring (LDS) process from LPKF on modified Vectra® LCP (Liquid Crystal Polymer) material from Ticona. The electronics housing can substitute for the conventional circuit board, encouraging miniaturization. This technology is suitable for mobile communication devices, hearing aids, and sensory technology for automobile electronics just to name a few.
This laser-based process consists of a minimal number of manufacturing steps: injection molding, laser structuring, and metallization (see figure). Basically, the structure is molded in a standard mold using polymer material that can be laser activated, the desired interconnect pattern is directly written on the resulting molded part utilizing LPKF's scanner based Microline 3D IR laser system, and the conductive paths are plated using industry standard electroless plating technology from Enthone, Inc. (West Haven, CT). The plating adheres only where the plastic been activated by the laser. Structures with a current resolution of >150 μm can be produced. Due to the high temperature resistance, the circuit structures on this LCP material are solderable.
The Microline 3D IR laser system contains a Nd:VO4 laser source for activating the plastic surface and a galvanometer scanner that guides the laser beam along the three-dimensional component surface. The LCP material (plastic granulate shown supporting MIDs in figure) consists of standard plastics, additives, and laser-fissionable metal-complexes.
Read LPKF's article on 3D-MID manufacturing featured on page IIa of Photonic Tech Briefs' October 2002 issue, or view it on-line at www.ptbmagazine.com/articles.