Plasma etching with tracer

摘要

A procedure for cleaning drilled holes in laminated workpieces such as printed electric circuit boards includes the steps of coating a cutting instrument, such as a drill bit, with a liquid tracer prior to a cutting or drilling operation. During the cutting or drilling operation, the liquid tracer becomes mixed with material such as an electrically insulating binder layer disposed between opposed metal plates of the circuit board. Any smearing of the insulation material upon exposed metal surfaces of the drilled hole contain elements of chemical compounds used in the tracer. After extraction of the drill bit from the circuit board, the board is placed in a plasma reactor wherein the metal surfaces are etched to remove any smears and debris of the insulation material found on the exposed metal surfaces. The tracer elements, such as deuterium and phosphorus are monitored in the effluent plasma of the reactor to determine when the cleaning of drilled holes in the board is completed.