Patent ID: 8568007

Claim:
A vehicle headlight comprising: a mounting base board having a top surface and a bottom surface that are opposite with respect to each other and are formed as substantially respective flat surfaces, the top surface of the mounting base board including a mounting region; a semiconductor light source mounted on the mounting region of the mounting base board; a heat sink including a radiating base plate having a top surface of a substantially flat surface, the radiating base plate having a top surface, the top surface of the radiating base plate being attached to the bottom surface of the mounting base board, wherein at least one of the bottom surface of the mounting base board and the top surface of the radiating base plate includes a concave portion, the concave portion being larger than the mounting region of the mounting base board, the concave portion including an opposing surface of the mounting region of the mounting base board, the opposing surface being located on the bottom surface of the mounting base board; a reflector having an opening portion located adjacent the radiating base board of the heat sink so that light emitted from the semiconductor light source is emitted in a light-emitting direction of the vehicle headlight from the opening portion of the reflector; at least one hole passing through the mounting base board and located toward the concave portion of the at least one of the bottom surface of the mounting base board and the top surface of the radiating base plate; and a thermal conductive viscous material including an inclusion having a maximum particle size, the thermal conductive viscous material disposed in the concave portion of the at least one of the bottom surface of the mounting base board and the top surface of the radiating base plate, wherein a depth of the concave portion is deeper than the maximum particle size of the inclusion of the thermal conductive viscous material wherein the thermal conductive viscous material is viewable from the at least one hole.