Flexible circuit board with planarized cover layer structure

A flexible circuit board, the flexible circuit board comprising:

• a substrate, which comprises a first surface and a second surface;
• a conductor layer, which is bonded by a first bonding layer to the first surface of the substrate, the conductor layer comprising a plurality of extended conductive signal lines, the conductive signal lines being spaced from each other by a predetermined distance so as to define a separation area between adjacent ones of the conductive signal lines;
• the first adhesive layer being formed on a surface of the conductor layer;
• and
• an insulation cover layer, which is laminated through a second adhesive layer on the surface of the conductor layer;
• characterized in that:
• the separation areas between the conductive signal lines of the conductor layer and a surface of each of the conductor layers are respectively formed with a filling layer, and the filling layer has a height that is higher than the surface of the conductor layer by a covering height, whereby the first adhesive layer has a planarization height in the separation areas and the planarization height is substantially equal to the sum of the height of conductive signal lines and the covering height.