Inputs
- Flex thickness
- Target radius
- Copper thickness
- Bend type
- Copper type
FPC / PCB Engineering Calculator
FPC Bend Radius Calculator
Estimate minimum bend radius and flex strain for RA or ED copper.
How to use the FPC Bend Radius Calculator
FPC bend radius affects copper fatigue, coverlay cracking and assembly reliability. Use this calculator to estimate a conservative minimum radius and strain level.
Bend radius and strain
Formula: Strain (%) = thickness / (2 x bend radius) x 100
- Thickness: total thickness of the flex bend area.
- Bend radius: inside bend radius used in the assembly.
- Strain: approximate outer-fiber strain before neutral-axis refinement.
Formula Basis
- Formula basis: geometric outer-fiber strain estimate for a bent flex section.
- Engineering note: IPC-2223-style flex design guidance, manufacturer rules and bend testing should be used for final FPC release.
Example
A 0.15 mm flex area with a 1.5 mm target bend radius has an approximate strain of 5%.
Outputs
- Recommended minimum radius
- Estimated strain
- Pass / warning indication
Engineering Notes
- RA copper is usually preferred for dynamic bending.
- Avoid vias, pads, stiffener edges and sharp corners in the bend zone.
- Dynamic bend applications need cycle testing instead of radius calculation only.
Validation Checks
- Bend-zone routing
- Copper strain
- Stiffener setback
- Dynamic bend cycle risk
Related Manufacturing Process
- Circuit Layout - Trace width, spacing, bend-zone routing, differential pair spacing
- Reliability Validation - Bending test, thermal shock, peel strength, solder float, ionic contamination
Related Calculators
- FPC Neutral Axis & Bend Stress Calculator - Visualize an FPC stack-up, estimate neutral-axis location, copper strain and layer stress, and compare coverlay opening or air-gap bend zones.
- Stiffener Setback Calculator - Estimate the minimum setback between stiffener edge and bend tangent for flex reliability review.
FAQ
Why does ED copper need more caution?
ED copper is generally less suitable for repeated dynamic flexing than RA copper, so the calculator uses a higher radius multiplier.
Can I place vias in the bend area?
It is normally avoided because plated holes and pads concentrate stress during bending.