Dear Groovy The mechanism for the wedge void defect you described is not solely limited to the drilling process creating a mechanical separation. Another occurance of wedge voiding can be created in the microetch step that follows deposition of a conductive material. Microetching is performed to undercut the conductive material and improve dry film adhesion to the outer layer. The microetch, however, does not limit its' reaction to the surface copper. Obviously, it also etches any copper that is present in the hole. Therefore, in some direct plate systems, the process sequence is modified to perform microetching prior to conditioning and thus eliminate the possibility of etching off the tail of the nailhead subsequent to the conditioning and conductor deposition steps. Otherwise, exposed glass that has not been conditioned will be present and hence the chance for a wedge void. The other possibility is that the copper supporting the conductive layer is removed which would also produce a wedge void. I assume your next question would be something to the effect of "What about dry film adhesion to the direct plate surface?" The answer is straightforward. If you formulate the chemistry to not adhere to copper, very little of it will. Say in the neighborhood of zero to several angstrom units, which can be easily removed with mechanical scrubbing or other (non microetching) chemical methods. It's difficult to describe the mechanisms of the process without slides, etc. I hope this explains what I meant in my earlier message. If I can explain it any better for you over the phone, please leave a message. I'll be on the road this entire week, so it may take a while for me to get with you if you call. Thanks for your interest! Kevin H. Baranowski Atotech USA 800 848 2826 X 4542