Light source board, manufacturing method thereof, and luminous keyboard using the same

A light source board, comprising:

• a substrate having a long side, a first short side, and a second short side, the substrate is formed of a flexible material;
• a composite circuit layer disposed on the substrate, the composite circuit layer comprising:
• a first conductive trace layer, and
• a second conductive trace layer stacked on the first conductive trace layer, wherein a conductivity of the second conductive trace layer is higher than a conductivity of the first conductive trace layer, and
• the composite circuit layer having:
• a wire portion formed of at least the first conductive trace layer, and
• a plurality of pad portions each formed of at least the first conductive trace layer and the second conductive trace layer, wherein the wire portion is electrically coupled to the plurality of pad portions;
• a first protective layer disposed on the composite circuit layer, the first protective layer exposing the pad portions;
• a plurality of light sources disposed on the pad portions, respectively;
• and
• a wire tail portion, the wire tail portion has a plurality of extended wires and a portion to be bent, the substrate is able to be bent by an external force at the portion to be bent, the extended wires is formed of only the first conductive trace layer in the portion to be bent, and the second conductive trace layer unextend in the portion to be bent.