Study of New Removal Technique by Use of Magnetic Polishing Method of Copper Overhang Generated in the Direct Laser Via Process

Abstract

In recent years, via holes is used for the connection of external wiring and internal wiring of the multilayer substrate. When copper foil of wiring layer was processed by laser, melted copper was adhered, so projections called “overhang” are formed around the opening of via hole. Adhesiveness and flatness of plating will be decreased by the overhung, therefore removal process of them will be indispensable. Therefore magnetic polishing method was tried as a novel removal technique in this study.