Abstract
In recent years, via holes have been used to connect the external wiring and internal wiring of multilayer substrates. When copper foil in the wiring layer is processed by a laser, melted copper is adhered, and projections called “overhangs” are formed around the opening of the via holes. The adhesiveness and flatness of the plating are decreased by the overhangs, and it is therefore indispensable to remove them. In this study, a magnetic polishing method was tried as a novel removal technique. This paper describes the polishing results and the method for producing the magnetic abrasive grains used in the polishing.
