Attenuation reduction grounding structure for differential-mode signal transmission lines of flexible circuit board

A flexible circuit board with an attenuation reduction grounding structure for differential-mode signal transmission lines of the flexible circuit board, comprising:

• a flexible substrate, which extends in an extension direction and comprises a first surface and a second surface, the flexible substrate comprising at least one connection section and an extension section connected to the connection section;
• at least one pair of differential-mode signal lines, which are formed on the first surface of the flexible substrate to be adjacent to each other and isolated from each other, each of the differential-mode signal lines having a pairs of top angles;
• at least one grounding line, which is formed on the first surface of the substrate and isolated from the differential-mode signal lines, the grounding line comprising a conductive contact zone formed on at least one selected location of a surface of the extension section;
• a covering insulation layer, which is formed to cover the first surface of the substrate, the pair of differential-mode signal lines, and the grounding line;
• a thin metal foil layer, which is bonded to a surface of the covering insulation layer and electrically connected to the conductive contact zone of the grounding line, the thin metal foil layer comprises a plurality of openings formed at locations corresponding to the pairs of top angles of the differential-mode signal lines respectively;
• and
• at least one via hole, which is formed in the extension section of the flexible substrate, the via hole extending through the thin metal foil layer and the covering insulation layer and corresponding to the conductive contact zone of the grounding line, the extension section comprising a plurality of slit lines formed by cutting in the extension direction to define a plurality of cluster lines.