Semi-Flex PCBs
Bend once, install forever.
Semi-flex PCBs are FR-4 boards with a thinned bend zone, designed for static installation in folded enclosures. A third of the cost of rigid-flex when you only need to bend once.
- Bend cycles
- ≤ 50
- Bend zone
- 0.2 mm
- Min radius
- R ≥ 6×t
- vs. rigid-flex
- ⅓
Use cases
When to pick semi-flex over rigid-flex
Simple: the moving parts of the design should live on rigid-flex, but the fold-once-at-install corner of the design can use semi-flex and save serious cost.
Assembly-line fold into a folded-sheetmetal housing.
Wrap-around LED strip from driver board to fixture.
BMS board folded to match 18650 cell stack geometry.
Bent once to sit around the coil former inside the meter.
Sensor-to-main-board bend fixed during module assembly.
Board folded once to sit in a thin remote enclosure.
Display PCB folded to meet main PCB at 90°.
Where the device doesn’t flex in daily use.
How the bend zone is built
One board, two thicknesses
The bend region is mechanically routed down to 0.2–0.4 mm, leaving two internal copper layers carrying the bend. Coverlay replaces solder mask in the bend zone to give copper room to flex without cracking.
- Controlled-depth mechanical routing
- Internal copper only in bend zone
- Coverlay protects bend area
- Pre-bake before bend to drive off moisture
- Jig-bent at install — no in-service flexing
- Post-bend electrical QC (100% continuity)
- Same fab tooling as rigid — short lead time
- Ships flat · bent only on the customer’s line
Capability
Published semi-flex spec
| Geometry | |
| Layer count (rigid) | 2 – 8 layers |
|---|---|
| Bend-zone thickness | 0.2 – 0.4 mm |
| Rigid-zone thickness | 0.8 – 2.0 mm |
| Min bend radius | 6 × bend-zone thickness |
| Bend cycles For dynamic bend, use rigid-flex | ≤ 50 (static install) |
| Materials | |
| Base | FR-4 (no polyimide) |
| Coverlay in bend zone | Liquid photo-imageable coverlay |
| Copper | 0.5 – 1 oz (inner, in bend zone) |
| Process | |
| Bend-zone forming | Depth-controlled mechanical route |
| Pre-bake | 125 °C / 4 h before bending |
| QC post-bend | 100% electrical continuity & visual |
| Cost & lead time | |
| vs. rigid-flex cost | Typically 30 – 40% |
| Lead time | 10 – 12 working days |
| Compliance | |
| Quality | IPC-A-600 · IPC-6013 bend-zone clauses |
| Cert | ISO 9001 · UL |
Frequently Asked Questions
Semi-flex FAQ
01Is semi-flex the same as rigid-flex?
No — rigid-flex uses polyimide in the bend region and can flex millions of cycles. Semi-flex uses FR-4 (routed thin) and is rated for up to ~50 bend cycles total. Cheaper, but static-only.
02Can I bend the board myself on assembly?
Yes — in fact that’s the point. We ship the board flat with a pre-score. You bend it on your assembly line using a simple jig. Always pre-bake the panel before bending.
03What’s the cost saving vs. rigid-flex?
Typically 60-70% cheaper than equivalent 4-layer rigid-flex because no polyimide and no coverlay lamination are used — standard FR-4 tooling.
04How should I design the bend zone?
Route all traces perpendicular to the bend line, keep them on inner layers, use copper pours sparingly, and make the zone length ≥ 5 mm. We’ll DFM-review before quoting.
Ready when you are
Send your Gerber & BOM — get a quote in 24 hours.
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