Gravdigr's Questions

[infinite monkey]

That's solder mask, protecting the circuitry (etched copper) from scratches and from solder wicking and shorts and corrosion. When producing circuit boards (I was QA supervisor at a high tech board manufacturer back in the day) the copper layer is etched into the circuitry pattern, then solder mask applied, then sent through a solder bath system with air knives to coat the exposed copper surfaces in solder, those surfaces being either through-hole or surface mount areas for components (typically a tin/lead alloy.) The mask prevents a big old mess of solder covered copper for that process.

That's it in a nutshell anyway. The green mask isn't always used: we made some boards coated in gold plating, and some the exposed laminate was left that way. Depends on the application and intricacy of the board. Don't know why green is the color, but when I worked in the industry it was all green.