Flexible printed circuit board structure

1. A structure of a flexible printed circuit board comprising:

a substrate;

a pair of lower flexible printed circuit boards facing each other at edges on the substrate and mounted with anode pads and cathode pads; and

a pair of upper flexible printed circuit boards facing each other at edges on the substrate to partially overlap the lower flexible printed circuit boards and mounted with anode pads and cathode pads,

wherein the upper flexible printed circuit boards and the lower flexible printed circuit boards include an insulating film base; an anode portion and a cathode portion mounted on the insulating film base; and a pair of anode and cathode pads mounted on one end portion of the insulating film base and a separate pair of anode and cathode pads mounted on an opposite end portion of the insulating film base,

wherein an end portion of each upper flexible printed circuit board overlaps an end portion of each lower flexible printed circuit board,

wherein the anode pads and the cathode pads of the upper flexible printed circuit boards and the anode pads and the cathode pads of the lower flexible printed circuit boards, which overlap each other, conduct electricity by a conductive material that fills a hole formed in a portion of the upper flexible printed circuit boards that overlap the lower flexible printed circuit boards,

wherein an anode pad and a cathode pad in the pairs of anode and cathode pads on end portions of the insulating film base are mounted in parallel to each other.

2. The structure of claim 1 , wherein the upper flexible printed circuit board and the lower flexible printed circuit board are bar-type flexible printed circuit boards.

3. The structure of claim 1 , wherein the upper flexible printed circuit board and the lower flexible printed circuit board have a width of 1 to 5 mm.

4. The structure of claim 1 , wherein the hole is formed at the anode pad and the cathode pad of the upper flexible printed circuit board.

5. The structure of claim 4 , wherein a diameter of the hole is equal to or smaller than a width of the anode pad and the cathode pad.

6. The structure of claim 4 , wherein a distance between a center of the hole of the anode pad and a center of the hole of the cathode pad is 0.5 to 2 mm.

7. The structure of claim 1 , wherein the conductive material includes lead.

8. The structure of claim 1 , wherein the conductive material is any one of brass solder, silver solder, german silver solder, manganese solder, gold solder, a lead-tin alloy, a lead-tin-zinc alloy, a lead-cadmium alloy, zinc-cadmium solder and a lead-tin-bismuth-based alloy.

9. The structure of claim 1 , wherein the upper flexible printed circuit board and the lower flexible printed circuit board have a multilayer structure including two or more layers.

10. The structure of claim 9 , wherein an uppermost layer of the upper flexible printed circuit board is installed to extend in a length direction of the upper flexible printed circuit board, and an end portion of the uppermost layer of the upper flexible printed circuit board is positioned to overlap the lower flexible printed circuit board.

11. The structure of claim 10 , wherein the hole is formed at the anode pad and the cathode pad that are formed on an end portion of the uppermost layer of the upper flexible printed circuit board.

12. The structure of claim 1 , further comprising an anisotropic conductive film positioned between the substrate and the flexible printed circuit board to correspond to the flexible printed circuit board.