Résumé:
For protection against moisture and consequent corrosion, printed circuit boards (PCBs) with enhanced environmental protection are, after assembly with electronic components, selectively coated with a protective film, a so called conformal coating. The main current methods for selective electronics coating are spray painting, which has good productivity but very limited resolution, and micro dispensing, which has limited productivity and cannot economically be upscaled. Inkjet technology on the other hand does provide sufficient resolution and the necessary scalability needed in large volume production for selective conformal PCB coatings, but the main drawback is its limitation in throw distance, which is in most applications only a few millimetres against component heights in excess of 10 millimetres on many PCBs. By optimising drop volumes and speeds by means of waveform tuning, reliable throw distances can however greatly increased. In this presentation a solution for selective inkjet-printed conformal PCB coatings with a paraffin based wax at a throw distance of 15 millimetres is presented.