Plasma Smear Removal in a High Aspect Drilled Hole
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-02
The drilling of through holes in multilayer printed circuit boards results in the smearing of epoxy layers across the copper planes. This smear must be removed and is typically accomplished by a plasma etch process. However, in the case of a high aspect ratio hole the center etches at a much slower rate than the shallow parts of the hole. This uneven etching is remedied in a procedure that yields uniform etching and smear removal throughout a high aspect ratio hole.