Ernest D Mitchell

US Patent:

40642909, Dec 20, 1977

Filed:

Aug 6, 1973

Appl. No.:

5/385950

Inventors:

Julius Alex Ebel - Anaheim CA
Ernest H. Mitchell - Santa Ana CA

International Classification:

B05D 132
B05D 512

US Classification:

427 97

Abstract:

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.