Ultrasonic Copper Lift-Off Prior to Additive Plating
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
A process is described for the selective removal of a thin copper layer. Copper, sputtered on a photolithographically structured permanent resist, is removed from the resist surface by wet rotating brush rolls. Ultrasound and an alkaline solution of a complexing agent also remove the copper layer from the vertical walls of photoresist channels to prevent overplating in the additive bath. The process for producing an embedded conductor structure for multilayer circuit boards, as previously disclosed in the IBM Technical Disclosure Bulletin 27, 3086-3087 (October 1984), is improved by removing excess copper from the vertical walls of photoresist channels, using 1.