Recent progress in direct exposure of interconnects on PCBs

Abstract

Purpose – This paper aims to use a survey of techniques to present the patterning of electric circuitry on printed circuit boards (PCBs). Second, a proposal of a new technology for direct exposure of interconnects on PCBs, using a digital micromirror device (DMD) is presented. Design/methodology/approach – In this proposal, the DMD chip was incorporated into a prototype system for exposure of soldermask pattern for a mass scale production. As a light source, 52 semiconductor UV lasers were combined together to deliver UV powerful beam onto the DMD chip area. Findings – A laser beam power of around 9 W was achieved from a single exposure head. With five exposure heads installed into a single machine, it is possible to expose 1,400 PCB panels per day. Such a production rate from a single exposure machine satisfies the demands of biggest PCB factories. Research limitations/implications – The Gaussian energy distribution of the laser beam from the 52-lasers head on the PCB surface was experimentally found. Because the exposure image needs to be highly uniform, this made a problem when the printed circuitry quality is considered. This problem was solved by using a software algorithm. Practical implications – The use of UV lasers exposure heads brings economical advantages over conventional bulb UV lamps. The power consumption drops down ten times for lasers source. Social implications – Because the exposure processing can be made with lower electric costs and higher yield, it will make the PCBs cheaper. Originality/value – At present, the idea of collecting a great number of lasers as a UV source for exposure head is attractive solution.