FPC Board Design Tips

This Gold Phoenix PCB Knowledge Center article explains practical design tips for flexible printed circuit (FPC) boards, covering stiffener placement, electroplating, outline processing, copper fill, drilling, process holes, and related process parameters.

1.   If it is necessary to add a stiffener to a flex board, the finger at the stiffener point must be moved inward by 0.3–0.5 mm, and an excess lead wire should then be made. The lead wire width is 0.1–0.2 mm smaller than the finger.

2.   Perform electroplating tests on flex boards. When conducting tests, attention should be paid to avoiding too much or too little plating, and repeated electroplating should be avoided. If the board can be fully conductive, use the electroplating gold process; if it cannot be fully conductive, use the immersion gold process. The immersion gold process should be done through a hole diagram.

3.   Copy the outline onto another layer, change the line width to 0.13 mm, cut it, and then add it to the line without fingers.

4.   First, arrange the outer shape of the board, and then fill in the process copper sheet. The copper sheet should be 0.5–0.8 mm away from the outer shape.

5.   Draw marking lines for packaging, adhesive tape, and stiffener on the circuit. The line width is 0.1 mm.

6.   Arrange the circuit, packaging, and drilling strip, and then copy the process copper sheet onto the circuit.

7.   When making drill strips, the process holes and alignment holes of the flex board and encapsulated drill strips should be the same size as the holes on the circuit.

8.   The 2.0 mm process hole in the drilling strip should be placed on the first knife.

9.   When making flex board drill strips, six sets of electroplated holes should be added, and the hole diameter should be based on the smallest one inside the flex board. (The minimum aperture of the flex board is 0.2 mm.)

10.  If there are slots in the sealing drill tape, a separate knife should be set up and placed at the end. (The minimum slot size is 0.65 mm.)

11.  When drilling holes for stiffener and adhesive tape, they should be 0.2 mm or more larger than one side of the flex board encapsulation, and additional shear holes should be added. (The size of the shear hole is 0.5–0.8 mm.)

12.  The drilling data of the flex board should be enlarged by five thousandths (1.0005), and if the PI stiffener needs to be drilled, the drilling data of the PI stiffener should be reduced by eight thousandths (0.9992).