Method of forming via hole in resin layer

Abstract

To reliably expose an underlying layer at a bottom surface of a via hole to form a via hole even at a resin layer including an inorganic filler. A method of forming a via hole by firing a laser beam at a resin layer (10) including an inorganic filler (12) characterized by including a first laser beam firing step of firing a (CO2) laser beam of the infrared region at a position of said resin layer for forming a via hole so as to expel the resin (11) and said inorganic filler (12) and thereby form a hole (18) in the resin layer and a second laser beam firing step of firing a (UV-YAG) laser beam of the ultraviolet region focused at a position where the hole is formed to remove a modified layer (16) of the resin remaining at the bottom of the hole and form a via hole (20) with an underlying layer (14) exposed at its bottom.

Dependencies are inferred from the claim text.