In the etching step, an uneven portion is formed by the laser on the upper surface of the metal substrate in the region corresponding to the pattern. This makes it possible to further increase the bonding force between the metal substrate and the metal layer without having to perform an additional process.

The method further includes a silver coating step of forming a silver coating on the upper surface of the metal substrate. The metal layer is formed on the upper surface of the silver coating. Due to the silver coating, the light emitted from the chips mounted on the metal substrate is reflected in an effective manner. Furthermore, the metal substrate can be protected by the silver coating.

Since the metal substrate is made of a metallic material, it is possible to easily form the metal layer the electroplating.

Inasmuch as an uneven portion is formed on the upper surface of the metal layer in a corresponding relationship with the uneven portion of the metal substrate, it is possible to improve the bonding force with the chips.

At least a part of the uneven portion is formed to make a closed curve. This makes it possible to further improve the bonding force between the metal substrate and the metal layer.