Inventors:
Sudarshan Lal - Glen Rock NJ
Craig G. Smith - Bridgewater NJ
Assignee:
AT&T Bell Laboratories - Murray Hill NJ
International Classification:
B44C 122
C23F 100
Abstract:
This invention is a process for etching copper sheets on insulating boards for use in fabricating multilayer printed circuit boards. The improvement resides in adding to a standard copper etching solution certain alkyltrimethyl ammonium chlorides with alkyl chain lengths ranging from 6 to 20 carbon atoms in amounts sufficient to yield intermediate kinetics behavior. Of special interest are dodecyltrimethyl ammonium chloride, hexadecyltrimethyl ammonium chloride and octadecyltrimethyl ammonium chloride present in an amount of from 0. 01 to 1. 0 wt %. A silicon-based antiforming agent may be added in amounts of from 0. 05 to 2. 0 wt. % to prevent an unacceptably large amount of foam from occurring during etching. With this formulation, the rate is mass transport controlled at low rates and almost independent of mass transport at high rates due to the inhibition of the surface reaction rate. As a result, non-uniformities in etch rates due to variations in mass transport conditions in processing equipment may be eliminated.
