UNIFORMITY OF COPPER ETCHING IN THE FABRICATION OF MULTILAYER PRINTED CIRCUIT BOARDS

摘要

This invention is a process for etching copper sheets on insulating boards for use in fabricating multilayer printed circuit boards. The improvementresides in adding to a standard copper etching solution certain alkyltrimethyl ammonium chlorides with alkyl chain lengths ranging from 6 to 20 carbon atoms inamounts 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 2.0wt. % 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. This unique formulation could significantly improve the yields presently obtained in manufacturing as well as allow the processing of fine-line multilayer circuit boards.