ULTRASONIC MIXING OF THROUGH HOLE TREATING COMPOSITIONS

摘要

A method for treating a non-conductive through hole surface of a printed wiring board is disclosed. A printed wiring board (26) including through holes (32) is cleaned, conditioned, and a conductive coating is applied to the initially-nonconductive through hole (32) by contacting it with a series of baths. The conductive coating, for example a graphite dispersion coating, facilitates later electroplating of the conductive surface. While at least partially immersing the through hole in one or more of these baths, ultrasonic energy is introduced in the bath in the vicinity of the through hole (32). The ultrasonic energy reduces the formation of blowholes during later processing (and especially soldering) of the printed wiring board (26). The ultrasonic treatment can also improve the dispersion of the conductive particles in a conductive carbon dispersion, reduce or eliminate the formation of pinhole defects, and provide other advantages.