Cleaning the Walls of Drilled Throughholes in Printed Circuit Boards and Cards by Plasma Etching
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
For the complete and fast removal of an epoxy resin/glass particle/copper drilling smear layer, occurring during the drilling of throughholes in printed circuit boards and cards on the hole walls of the copper planes, it is proposed that the previous O2/CF4 plasma etch process be followed by a further plasma process, using activated gases, such as methyl chloride, bromide or iodide. During a plasma etch process with a gas mixture of O2 and CF4 and an operating pressure of about 0.4 mbar, substantially only epoxy resin is removed which together with glass particles and copper drillings forms the smear layer on the hole walls of drilled copper conductor planes.