B - Operations – Transporting – 08 – B
Patent
B - Operations, Transporting
08
B
356/20, 356/22
B08B 3/08 (2006.01) H05K 3/00 (2006.01)
Patent
CA 1097823
CLEANING OF HIGH ASPECT RATIO THROUGH HOLES IN MULTILAYER PRINTED CIRCUIT BOARDS ABSTRACT OF THE DISCLOSURE A cleaning process for high aspect ratio through holes of multilayer printed circuit boards assures the removal of any loosened fiberous material or epoxy smears in the through holes and also provides an inverted "T" structure at the innerplanes of the internal conductive circuits within the printed circuit board sandwich. The inverted "T" structure helps to move the contact point between the plating of the through hole and internal cir- cuit lines further into the circuit board, thereby elimi- nating the "Z" stress at the edge of the innerplane. This process is accomplished by first vapor blasting the through holes, soaking the board in a suitable solvent to loosen any fibers or smears on the circuit innerplanes of the board, removing the excess solvent from the through holes and then feeding a unilateral stream of a cleaning solution through the holes, the cleaning solution opera- ting to remove excess fibers and smears in the through holes and to produce a slight, uniform etchback of the metal innerplanes of the printed circuit boards. There- after, the solution may be reduced and any excess clean- ing solution is removed.
310044
Alpaugh Warren A.
Canestaro Michael J.
Ellis Theron L.
International Business Machines Corporation
Na
LandOfFree
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