Because of the special nature of FPC, we have to pay attention to the following printed flexible circuits layout design requirements:
Rules: ensure the signal smoothly aligned priority, design it short, straight, less via for the principle, try to avoid long, fine and round circle circuit layout, keep it horizontal, vertical and 45-degree degree layout, avoid arbitrary Angle line, arc circuit for the bending part, the details are as following:
1. Line width: considering that the width for data circuit and power circuit are different, we make the reserved trajectory in accordance with the average 0.15mm
2. Line distance: According to the current production capacity of most manufacturers, we design the line distance (Pitch) to be 0.10mm.
3. Line margin: the outermost line distance FPC contour distance should be 0.30mm, the bigger the better if there is enough space.
4. Fillet: FPC contour on the fillet minimum design as the radius R = 1.5mm
5. The conductive circuit is perpendicular to the bending direction
6. The conductive circuit should pass through the curved area evenly
7. The conductive circuit should be as far as possible covered with curved area
8. in the curved area cannot have additional plating metal (bending area circuit is not plated)
9. Line width should be consistent
10. Double-sided flex PCB traces cannot overlap together to form “I”
11. The number of layers in the curved area should be as less as possible
12. Bend area cannot have plated through holes and non-plated through holes
13. The bending center axis should be set in the center of the conductive circuit. The material coefficient and thickness of both the circuit should be the maximum same. This is very important in dynamic bending applications.
14. The horizontal torsion follows the following principle – reducing the bending cross section to increase flexibility, or partially increase the area of the copper foil to increase toughness.
15. Vertical bending: increasing the radius of bending, or bending the central area to reduce the number of layers.
16. For products require EMI, if there is the USB, MIPI and other high-frequency radiation signal line in the FPC, it should be based on EMI measurement on the FPC to increase the conductive silver foil layer and conductive silver foil to ground, to prevent EMI.