For an FPC made out of Kapton (polyimide), what are the:

  • min trace width
  • min trace-trace separation
  • min distance from a trace to the edge of the FPC
  • min drill hole diameter
  • min distance from a drill hole to the edge of the FPC
  • min distance from a drill hole to a trace

I'm looking for the "lowest common denominator" that any competent fab should be able to handle. Thanks!

  • 1
    \$\begingroup\$ Ask yout PCB supplier! \$\endgroup\$ Jun 2, 2013 at 6:43
  • \$\begingroup\$ That's different than asking for the standard. For example, if I was asking about non-flex PCB, the standard would be 4 4 rules. I don't believe it is right to downvote this, as the StackExchange policy on beginner questions is to allow them. \$\endgroup\$ Jun 2, 2013 at 7:01
  • \$\begingroup\$ Just out of curiosity (since I have no idea what norms are followed in FPC layouts), aren't drill-holes preferably avoided with FPC? A drilling would reduce structural strength of an already flimsy substrate, I'd suspect. \$\endgroup\$ Jun 4, 2013 at 6:25
  • \$\begingroup\$ Good question, @Anindo! Maybe mechanical drilling is bad but laser drilling is fine? \$\endgroup\$ Jun 5, 2013 at 7:53
  • 2
    \$\begingroup\$ rigid-flex is the "standard" way to handle through-hole and large surface-mount components. \$\endgroup\$ Jun 24, 2013 at 19:08

2 Answers 2


There are no standard design rules, each manufacturer, unfortunately, has their own design rules. These are dictated by how tightly controlled they run their processes. Even if they use the same machines and processes it will vary a little. Vias in FPC (which are small) are not an issue unless you expect to flex the cable lots and PTH parts should be fine as well as long the parts are mounted (the body supplies some rigidity). SMT devices can be an issue as the rigid body combined with flexing generates large stresses on the pads and can pull the pads off.

Have run PTH, SMT and wire bonds onto FPC and rather than use rigid flex (which is a good option) we used FR-4 (and some times ceramic) stiffeners on the backside to prevent flexing in that region (no traces, just fiberglass).


I'm no expert on Flex PCB's but a board house I've used in the past has the following specifications listed for flex boards and flex rigid boards material PI, PET, PEN, FR-4 :
Minimum trace Width / Min Clearance:
Inner: 0.5oz: 4/4mil, 1oz: 5/5mil,2oz: 5/7mil
Outer: 1/3oz-0.5oz: 4/4mil, 1oz: 5/5mil, 2oz: 5/7mil

Min Hole Ring
Inner: 0.5oz: 4mil , 1oz: 5mil,2oz: 7mil
Outer: 1/3oz-0.5oz: 4mil, 1oz: 5mil,2oz: 7mil

Min Hole Size and Tolerance
Min hole: 8mil
Tolerance: PTH±3mil, NPTH±2mil

Minimum distance from a drill hole to the edge of the FPC : Not listed ??

Minimum distance from a drill hole to a trace: Apply Minimum trace Width / Min Clearance rule


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