Fine pitch circuitization with filled plated through holes

摘要

A high density printed wiring board is prepared by applying an essentially solid material into plated through holes such that the metallized layers within the through hole are unaffected by chemical metal etchants. In this manner, lateral surface metallized layers can exclusively be reduced in thickness by use of said chemical agents. These thinned lateral surface metallized layers are ultimately converted into fine pitch, 25 to 40 microns, circuitry, thereby providing high density boards. Since the through hole wall metallization is unaffected by the etching process, excellent electrical connection between the fine line circuitry is obtained. Various printed wiring board embodiments are also presented.