Rigid Flex

A rigid-flex PCB is a circuit board that combines rigid and flexible PCBs through specific processes, offering both support stability and bendable/foldable characteristics.

Common types include single/double-sided flexible combined with single/double-sided rigid, and multi-layer flexible combined with multi-layer rigid.

Rigid PCBs are hard and stable, flexible PCBs are soft and bendable but low in strength. Rigid-flex PCBs combine their advantages to meet complex layout and mechanical performance needs.

Composed of rigid layers (FR-4, etc.), flexible layers (polyimide PI), adhesive layers (glue), and metal traces.

Consider circuit complexity, signal requirements, and cost. Simple circuits need 2-4 layers; complex high-speed circuits may need ≥6 layers.

Avoid sharp angles; use rounded/45° angles. Keep line widths uniform and appropriately widened. Avoid vias in bending areas (distance from rigid-flex zone ≥50mil).

Lines should transition smoothly and perpendicularly to the bending direction. Wires should be evenly distributed and maximized in width. PTH, Coverlay, and non-flowing PP designs are forbidden in the transition zone.

Use simulation software to calculate parameters. Select low-loss dielectrics (e.g., RO4000 series). Strictly control etching to ensure line width consistency.

Add thermal vias in rigid layers under high-power components. Use metal substrates/thermal conductive adhesives. Perform thermal simulation at the design stage to optimize heat dissipation paths.

Design according to installation space and mechanical structure. The size of the flexible area should consider bending deformation to avoid over-compression.

Ensure smooth transitions between pads and traces; avoid right angles. Set solder toes for independent pads to enhance support and soldering firmness.

Tool holes in flexible boards must not be shared. Positioning holes in rigid areas should consider processing and assembly accuracy.

Reasonably partition planes to reduce noise. Connect planes via vias/metallized holes, paying attention to reliability and current-carrying capacity.

Avoid vias in bending areas. Add protective copper traces or arc-shaped traces when space allows. Maximize the bending area as much as possible.

Avoid long parallel traces. Use differential signaling. Increase the spacing between signal and ground layers to reduce coupling.

Reasonably set test points in rigid areas for easy production testing. Positions should be accessible and not affect circuit functions.

Thermal expansion coefficients of rigid and flexible layers should be matched. The adhesive layer should have good adhesion to both (e.g., PI and FR-4).

Arrange stack-up order by signal type (high-speed signals close to ground layers). Balance thickness and cost.

Use clear symbols and text on drawings to mark bending ranges, directions, and radius requirements.

Set product models, version numbers, production dates, etc., in rigid areas. Identifications should be clear, wear-resistant, and traceable.

Keep traces short and straight with few vias. Use microstrip/stripline structures. Shield to prevent radiation and interference.

Design to meet manufacturers' process capabilities (minimum line width/spacing, via size, etc.). Facilitate automatic/manual assembly.

Ensure smooth transitions to avoid stress concentration. Use gradual line width changes or special transition structures.

Copper cladding in rigid areas aids heat dissipation and reduces ground impedance. In flexible areas, consider bending reliability for copper cladding.

Surround with ground and add shielding layers. Keep away from interference sources (high-power components, clock traces, etc.).

Reasonably layout to reduce radiation sources. Shield interference-prone circuits. Optimize grounding to reduce resistance.

Select vias (blind/buried/through) as needed. Blind/buried vias reduce layers but are costly. Use through vias cautiously in flexible areas.

Make openings slightly larger than designed to allow glue flow. Use special dies for small dense openings.

Increase copper in rigid areas (set solid copper berths in scrap areas). Reasonably select material thickness.

Ensure sufficient line width for high currents. Use multi-layer copper foil or add traces. Consider heat dissipation and voltage drop.

Plan panelization according to production equipment and processes. Improve efficiency and material utilization; note shape size and positioning.

Set test points and repair interfaces. Layout components for easy disassembly. Provide detailed repair instructions.

Place through-hole components in rigid areas for easy fixing. Reasonably distribute SMD components in rigid/flexible areas to ensure reliable connections.

Set multiple fiducial marks in rigid areas for production positioning and calibration. Shapes/sizes should meet equipment requirements.

Select materials suitable for temperature/humidity ranges. Strengthen fixing and support in vibration environments; optimize layout to reduce impacts.

Use physical isolation (slotting/shielding) or electrical isolation (opto-couplers/transformers) to separate analog/digital signals, etc.

Locally/wholly paste PI/steel/FR4 and other reinforcement materials. Choose methods and thicknesses as needed.

Simplify design to reduce layers and complex structures. Choose cost-effective materials/processes. Optimize panelization and processes.

Maintain sufficient spacing to prevent breakdown. Use insulating materials/isolating layers. Special 标识 and protect high-voltage traces.

Welding is suitable for most cases; ensure quality. Crimping is for frequent connections; select appropriate connectors and processes.

Process: Rigid board fabrication → flexible board fabrication → rigid-flex bonding → shape processing → surface treatment → testing.

Rigid layers: FR-4; flexible layers: polyimide (PI).

Control lamination temperature, pressure, time. Optimize sequence to reduce stress. Prevent bubbles and wrinkles.

Use ductile copper foil. Control etching parameters. Use grid routing in bending areas to disperse stress.

Laser drilling + via filling/electroplating. Control parameters to avoid burrs. Strictly test electrical conductivity.

Use high-precision milling/stamping equipment. Fix flexible areas with spacers during processing. Stamp flexible areas before rigid ones in die stamping.

Immersion gold, gold plating, HASL, OSP (organic solderability preservative), etc., selected as needed.

Optimize lamination parameters for flatness. Increase flexible area size in design. Use proper support and fixing during processing.

Strictly control etching for line width consistency. Select high-precision stable dielectric materials. Monitor and adjust impedance in real time during production.

Optimize processes to reduce steps. Use automated equipment. Reasonably schedule production to improve equipment utilization.

Increase residual copper design. Adjust 压板 heating rate ≥3.0℃/min. Select appropriate glue materials for uniform filling.

Select high-adhesion glue. Clean bonding surfaces. Control bonding temperature, pressure, time.

Fix four corners with a soldering iron before lamination. Adjust lamination parameters according to coverlay properties. Avoid wrinkles and bubbles.

Conduct strict electrical tests (AOI, flying probe testing) during production. Strictly control processes to avoid trace defects.

Use traction boards to pass through horizontal lines and prevent jamming. Use special fixing and support during processing for stability.

Use high-precision positioning systems (laser/pin). Strictly check and adjust alignment before lamination.

Use ductile electrolytic copper foil. Design bending radius ≥10x board thickness. Special routing to enhance fatigue resistance.

Optimize trace design for solderability. Select suitable soldering processes (reflow/wave soldering). Control temperature and time.

Use high-precision screen printing equipment and stencils. Clean and position boards before printing, and strictly control parameters like squeegee pressure, speed, and angle.

Select suitable inks and processes to ensure clear and wear-resistant characters. Pay attention to printing position and direction, and conduct quality checks to prevent blurring or peeling.

Establish a complete quality management system. Strictly control raw materials, processes, and equipment parameters. Regularly maintain and calibrate equipment, and conduct sampling inspections.

Classify and recycle waste such as metal and plastic. Refine metal waste and reuse or incinerate plastic waste environmentally.

Install anti-static flooring, workbenches, wrist straps, etc., in the workshop. Ground equipment and use anti-static packaging for raw materials and semi-finished products.

Develop detailed rework process specifications, train rework personnel, use appropriate tools and equipment, and protect surrounding circuits and components.

Maintain a clean workshop with regular disinfection. Use dust-proof and moisture-proof packaging for raw materials and semi-finished products, and adopt clean production processes.

Use protective packaging such as anti-static bags and foam pads. Label product models, quantities, production dates, etc.

Use anti-static and non-sharp fixtures. Fix with vacuum suction or special clamps. Avoid dragging or folding, and use special trays for handling.

Unreasonable grounding design, damaged shielding layer, insufficient routing spacing, and unmatched impedance for high-speed signals.

Polyimide materials can withstand short-term high temperatures of 260°C. It is recommended to control the peak temperature at 245°C-255°C with high-temperature duration ≤60 seconds.

Optimize process parameters such as placement pressure and temperature curves. Use high-precision pick-and-place machines and positioning systems, and strengthen incoming material inspection.

Check the transition zone fillet radius (recommended ≥0.5mm), avoid assembly stress concentration, and add reinforcing plates or optimize bending processes.

Prioritize miniaturized, thin, and bend-resistant components (e.g., flip chips, 0201 and smaller packages). Avoid components with 过长 or heavy leads.

Combine laser and mechanical drilling, use positioning holes and targets for alignment, and monitor in real time with AOI.

Use X-ray to detect internal voids and cold soldering. Conduct pull tests and thermal cycle tests to evaluate environmental reliability.

According to IPC standards, ≥3 times the substrate thickness (e.g., 0.1mm PI substrate, recommended ≥0.3mm). Refer to material supplier parameters.

Check routing length and meandering trace rationality. Confirm impedance matching and dielectric constant of dielectric materials.

Select glue with appropriate viscosity, control application volume and position, and adjust dispensing parameters and paths to avoid overflow.

Wrinkles may cause trace deformation or breakage, affecting electrical and mechanical performance. Replace or repair and retest.

Use flying probe, ICT, or FCT testing. Simulate actual bending of flexible parts and test signal integrity, voltage/current, etc.

≥10¹⁰Ω at normal temperature/humidity, ≥10⁸Ω after 168 hours at 85℃/85%RH (IPC-6012 standard).

Apply 1.5-2 times the rated voltage for 1-5 minutes with no breakdown or flashover (e.g., 75-100V for 50V rated voltage).

Conduct high-low temperature cycles (-40℃→room→85℃), hold each temperature for 30-60 minutes, ≥50 cycles, and inspect for trace cracking or delamination.

Use special equipment to set angle (e.g., ±90°) and frequency (10 cycles/min), bend until failure, and record cycles (≥100,000 times).

Use flying probe testers or multimeters for point-by-point troubleshooting. Combine with AOI for surface open detection and 金相切片 for internal inspection if needed.

Avoid compressing or pulling flexible parts. Use elastic probes, match fixture positioning accuracy with the board, and ensure anti-static measures.

Re-solder cold/void solder joints with a hot air gun. Use desoldering wick for short circuits, and control temperature and time.

For flexible parts, use laser micromachining to remove damaged areas and repair with selective electroplating or conductive adhesive. For rigid parts, use jumper wires or replace components.

Re-perform functional and insulation resistance tests and visual inspections. Reinforce repaired areas (apply conformal coating, add reinforcing plates) and conduct environmental tests if needed.

Repair is more cost-effective for minor damage; re-production is better for multi-layer or extensive damage. Repair costs are about 30%-70% of production costs.

Protect non-repaired areas with heat-insulating materials. Use fine, non-sharp tools to avoid scratching flexible parts, and clean residual contaminants.

Number of layers, size, process complexity (e.g., blind/buried vias, high-precision impedance), material selection, order quantity. Processes account for 30%-50%.

Optimize design to reduce layers and special processes. Select cost-effective materials, increase batch size, and negotiate preferential plans with suppliers.

10-15 days for regular products, 20-30 days for complex products, and 5-7 days for urgent orders (with increased costs).

Higher density integration, thinner and lighter designs (e.g., Anylayer HDI), flexible materials with low dielectric constant and high flexibility, and integration with advanced packaging like SiP.

Meeting high-frequency and high-speed signal transmission requirements, solving attenuation and crosstalk issues, and improving bend resistance and reliability of flexible parts.

AI optimizes design and predicts defects. Machine learning adjusts process parameters, and AI visual inspection improves defect recognition efficiency.

Compliance with RoHS, REACH, etc., restrictions on hazardous substances, reduced wastewater/gas emissions, and use of environmentally friendly materials/processes.

High reliability, biocompatibility, ISO 13485 certification, strict EMC requirements, and resistance to high-temperature/pressure sterilization.