Lamp unit, circuit board, and method of manufaturing circuit board

A circuit board configured to mount an optical semiconductor element comprising:

• an insulating layer;
• a first copper material layer arranged to be superimposed on one surface side of the insulating layer, and forming a thermal conduction part;
• a second copper material layer arranged to be superimposed on the other surface side of the insulating layer, a trace part to be connected to the optical semiconductor element being formed therein;
• and
• an opening part which is provided in the insulating layer, through which the first copper material layer is exposed toward the other surface side, and in which the optical semiconductor element is arranged with an undersurface thereof bonded to the first copper material layer.

A method of manufacturing a circuit board configured to mount an optical semiconductor element comprising:

• forming a first copper material layer on one surface of an insulating layer;
• forming a second copper material layer on the other surface of the insulating layer;
• forming an opening part in the insulating layer by removing a part of the insulating layer in such a manner that the first copper material layer is exposed from the other surface side;
• bonding an undersurface of the optical semiconductor element to the first copper material layer in the opening part;
• and
• joining an electrode of the optical semiconductor element to the second copper material layer.