Smear Removal from Printed Circuit Boards
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-10
The removal of epoxy smear from drilled holes presents several difficulties, such as copper or epoxy etch back, undercutting, and redisposition of epoxy. These can be avoided by using a caustic, organic-aqueous mixture for cleaning the through-holes after a drilling operation. The drilled panels are first immersed in a mixture, such as stripper A-150 from Enthone, Inc., at 190 degrees F for approximately two minutes. This mixtur serves as an epoxy resin wetting agent. The panels are then dipped in a 10% hydrochloric acid solution and followed by immersion for approximately 2 minutes in a sodium chlorite and sodium hydroxide mixture at 190 degrees F.