Patent ID: 8008756

Claim:
A heat dissipating wiring board comprising: a metal wiring plate with a circuit pattern formed therein; a filler-containing resin layer having embedded therein said metal wiring plate such that a top surface of said metal wiring plate is exposed; and a heat dissipating plate arranged on an under surface of said filler-containing resin layer, wherein a space that divides part of said circuit pattern is formed of a through groove provided in said metal wiring plate, said through groove comprises: a fine groove that opens at said top surface of said metal wiring plate; and an expanded groove that expands discontinuously from a lower end of said fine groove toward an under surface of said metal wiring plate, said fine groove expands from said top surface of said metal wiring plate towards said expanded groove, and an oxidized film formed on an inner wall of said fine groove is thicker than an oxidized film formed on an inner wall of said expanded groove.