Improved, Rapid Process For Cleaning "Blind" Via Holes Drilled In A Circuit Board
Original Publication Date: 1979-Sep-01
Included in the Prior Art Database: 2005-Feb-20
Certain circuit board subassemblies are made with small, typically 6-mil diameter, blind via holes which extend to the surface of internally "buried" copper pads. These vias are formed by the heat-induced, drilling action of laser beams which are directed to impinge upon and into selectively etched portions of the subassembly surface, ultimately penetrating to the buried pad. After laser drilling, the holes are left filled with debris which must be removed in order to insure subsequent additive plating integrity or continuity between the buried pad, the via walls and the copper circuitry on the subassembly surface.