Flexible coplanar waveguide low profile high speed transmission circuit and fabrication method of the same

A fabrication method of a flexible coplanar waveguide low profile high speed transmission circuit, comprising:

• providing a first flexible substrate, a second flexible substrate and a circuit layer, wherein the circuit layer comprises a signal transmission circuit and two grounded circuits, and the signal transmission circuit is disposed between the two grounded circuits;
• disposing the circuit layer between the first flexible substrate and the second flexible substrate;
• performing a pressing step to press the first flexible substrate, the second flexible substrate and the circuit layer;
• adhering a first EMI shielding film to the first flexible substrate, wherein the first EMI shielding film and the circuit layer are located on two opposite surfaces of the first flexible substrate;
• and
• adhering a second EMI shielding film to the second flexible substrate, wherein the second EMI shielding film and the circuit layer are located on two opposite surfaces of the second flexible substrate;
• wherein the flexible coplanar waveguide low profile high speed transmission circuit satisfy the following equation:
• tan
• (
• DT
• /
• TS
• DK
• )
• ≥
• 1
• where DT is a distance between the signal transmission circuit line and one of the grounded line;
• TS is a thickness of the first flexible substrate and a thickness of the second flexible substrate, and DK is the dielectric constant of the first flexible substrate and the second flexible substrate.