PCB & PCBA Manufacturer
Rigid Flex Circuit Boards – PCB Flex Rigid Solution
A Rigid Flex Circuit Board (also known as a flex rigid PCB or PCB flex rigid solution) is a hybrid construction that integrates rigid FR4 sections and flexible polyimide sections into a single printed circuit board.
This technology allows you to mount heavy components on the rigid sections – processors, connectors, batteries, large capacitors – while the flexible sections bend, fold, and twist to fit into tight, irregular, or moving enclosures.
If your product requires 3D packaging, high reliability, or reduced weight, a rigid flex circuit board is the solution.
What is a Rigid Flex Circuit Board?
| Feature | Description |
|---|---|
| Rigid sections | Standard FR4 material – supports heavy components |
| Flex sections | Thin polyimide (Kapton) – bends and folds |
| Continuous traces | Copper conductors run uninterrupted from rigid to flex to rigid |
| No connectors | Replaces rigid board + cable + rigid board assemblies |
| Single board | One integrated circuit board – not multiple boards |
Think of it as: A rigid PCB that grows flexible “wings” or “tails” where needed.
Rigid Flex vs. Rigid PCB + Cable + Rigid PCB
| Approach | Components | Connections | Reliability | Assembly |
|---|---|---|---|---|
| Traditional | PCB #1 + Cable + PCB #2 | 2 connectors + cable | Lower (connector failures) | Complex |
| Rigid Flex | Single integrated board | 0 connectors | Higher (no connectors) | Simple |
Why Choose a Rigid Flex Circuit Board?
| Benefit | How Rigid Flex Delivers |
|---|---|
| Eliminates connectors | No board-to-board connectors – removes a major failure point |
| No cables | No cable BOM, no cable assembly, no cable routing |
| 3D packaging | Folds to fit curved or irregular enclosures |
| Higher reliability | Fewer interconnects = fewer failure modes |
| Weight reduction | No connectors, no heavy cable harnesses |
| Space savings | Replaces multiple boards with one |
| Better signal integrity | Continuous traces – no impedance jumps at connectors |
| Lower assembly cost | One board to place, not multiple boards + cables |
| Simpler logistics | One SKU instead of 3-5 SKUs |
Rigid Flex Circuit Board Construction
| Layer | Material | Thickness (typical) | Function |
|---|---|---|---|
| Coverlay (top) | Polyimide film | 0.5 mil | Protects flex copper |
| Flex copper layer(s) | Rolled annealed (RA) copper | 0.5-1 oz | Signal traces in flex areas |
| Polyimide core | Flexible base material | 1-2 mil per layer | Insulation between flex layers |
| Flex copper layer(s) | Rolled annealed (RA) copper | 0.5-1 oz | Signal traces in flex areas |
| Coverlay (bottom) | Polyimide film | 0.5 mil | Protects flex copper |
| FR4 rigid sections (added on rigid areas only) | FR4 + prepreg + copper | 0.4-1.6 mm | Component mounting, additional routing |
Key point: The flexible polyimide core runs continuously through the entire board. FR4 material is selectively added only where rigidity is needed.
Common Rigid Flex Configurations
| Configuration | Rigid Sections | Flex Sections | Typical Application |
|---|---|---|---|
| Single flex tail | 2 | 1 | Hinge connection (laptop, clam shell) |
| Multiple tails | 1 + multiple satellite | 2+ | Medical scope, multi-sensor array |
| Z-fold | 3 | 2 | Foldable phone, stackable modules |
| Parallel sections | 3+ | 2+ | Multi-panel display |
| Book-fold | 2 | 1 (foldable) | Portable instrument, foldable device |
Technical Specifications for Rigid Flex Circuit Boards
| Parameter | Our Capability |
|---|---|
| Rigid sections – layer count | 2 to 12 layers per section |
| Flex sections – layer count | 1 to 4 layers |
| Total rigid sections | 2 to 8+ sections |
| Rigid thickness per section | 0.6mm to 2.4mm (can vary) |
| Flex thickness | 0.1mm to 0.4mm |
| Copper – rigid sections | 1 oz to 6 oz |
| Copper – flex sections | 0.5 oz or 1 oz RA (rolled annealed) |
| Min trace/spacing (rigid) | 4 mil / 4 mil |
| Min trace/spacing (flex) | 4 mil / 4 mil |
| Min drill size | 0.20mm mechanical |
| Bend radius (static) | Minimum 10x flex thickness |
| Bend radius (dynamic) | Minimum 30x flex thickness |
| Surface finish | ENIG (preferred), HASL, OSP, Immersion Silver |
| Stiffeners | FR4, polyimide, or metal (on flex sections as needed) |
| EMI shielding | Silver ink, copper layer, or shielding film |
Design Guidelines for Rigid Flex Circuit Boards
| Design Element | Recommendation | Why |
|---|---|---|
| Bend radius | ≥10x flex thickness (static), ≥30x (dynamic) | Prevents copper fatigue and cracking |
| Flex length | Allow extra length for bending | Prevents stress on rigid sections |
| Flex width | Consistent width – no sharp corners | Reduces stress concentration |
| Trace routing in flex | Perpendicular to bend axis | Minimizes stress on traces |
| Via placement | No vias in bend areas | Vias crack under flex stress |
| Copper weight in flex | 0.5 oz preferred (1 oz max) | Thinner copper bends better |
| Copper type in flex | Rolled annealed (RA) only | RA copper withstands bending |
| Coverlay | Use coverlay (not solder mask) on flex | Coverlay flexes, solder mask cracks |
| Component placement | Rigid sections only | Flex too thin for heavy components |
| Stiffeners | Add under connectors on flex tails | Prevents flex damage during mating |
Applications for Rigid Flex Circuit Boards
| Industry | Application | Why Rigid Flex is Ideal |
|---|---|---|
| Aerospace | Avionics, satellite electronics | Vibration resistance, weight reduction, high reliability |
| Medical | Endoscopes, patient monitors, hearing aids | Small size, no connector failure, cleanability |
| Wearables | Smartwatches, fitness bands, AR/VR glasses | Fits curved enclosures, low weight, battery support |
| Industrial | Robotics, CNC controllers, sensors | Dynamic flexing, rugged environment |
| Automotive | Camera modules, sensors, infotainment | Vibration resistance, tight spaces |
| Consumer | Laptops, tablets, foldable phones, cameras | Hinge connection, space efficiency |
| Military | Portable radios, ruggedized equipment | High reliability, shock/vibration resistance |
Rigid Flex vs. Alternatives – Comparison
| Feature | Rigid PCB + Cable | Flexible PCB Only | Rigid Flex (Combo) |
|---|---|---|---|
| Heavy component support | Excellent | Poor (needs stiffeners) | Excellent (on rigid sections) |
| Bendability | None (cable bends) | Excellent (entire board) | Excellent (flex sections only) |
| Connectors needed | Yes (2-4) | Fewer | None |
| Space efficiency | Good | Excellent | Very good |
| Weight | Heavy (connectors + cable) | Light | Light |
| Reliability | Moderate (connectors fail) | Good | Excellent |
| Assembly complexity | High (multiple parts) | Low | Low |
| Total system cost | Often higher | Moderate | Often lower |
| Best for | Low cost, simple | Simple bending | Complex folding + heavy components |
Why Choose Our Rigid Flex Circuit Boards?
| Feature | What You Get |
|---|---|
| True rigid-flex integration | Continuous traces from rigid through flex to rigid |
| RA copper standard for flex | Withstands repeated bending (dynamic flex) |
| No connectors needed | Eliminate connector failure points |
| Engineering support | Bend radius analysis, stackup design, material selection |
| Prototype available | Fast turnaround for design validation |
| Volume production | Scalable to your needs |
| ISO9001 & UL certified | Quality and safety guaranteed |
| Free DFM review | Rigid flex specific – bend radius, via placement, stackup |
Order Process for Rigid Flex Circuit Boards
Upload Gerber files – specify rigid and flex layers, bend areas, flex length
Free DFM review – we verify bend radius, via placement, stackup, flex routing
Receive quotation – based on configuration complexity
First article (strongly recommended) – 5-20 pieces for validation
Production – built to your specifications
100% electrical test – including flex continuity and bend test (if specified)
Secure shipping
New to rigid flex circuit boards? Start with a prototype (5-10 pieces) to validate your design before mass production. We provide free DFM review to catch issues early.
