System for coating plated through hole surfaces

摘要

A system is disclosed for coating the interior surfaces of plated through holes in printed circuit boards by flowing a minimal volume of a low viscosity fluid carrying resist solids through holes in a board. After coating, the liquid phase of the fluid is evaporated, leaving a protective solid coating adhered to the walls of the plated through holes. The system enables positive imaging of the printed circuit boards preparatory to etching.