Measuring the Thickness of Coatings on Printed Wiring Boards

The Beta Backscatter Coating Thickness Gauge has been a very well used “tool” in printed wiring production for many years. The increased requirement to more closely control the quality and cost of high priced materials and processes has been met by instrument developments utilising microprocessors, not only for measurement but also for instrument, operator and results evaluation. Despite this, the instrumentation will only deliver the correct results if given correct information in the first place, thus, the operator must know a little of the preceeding coating process or at least be given the relevant and correct information. This paper describes the importance of the substrate material and the density of the coating material when measuring coating thickness.