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Rigid Flex PCB

A rigid-flex PCB consists of rigid PCB material combined with flexible PCB material, connected by a flexible adhesive material.

 
rigid flex pcb manufacturers

About Rigid Flex Board

A rigid-flex PCB combines both rigid and flexible substrate materials, offering mechanical support with rigid sections and flexibility with flexible ones. This allows for space-saving, lightweight designs with complex interconnections and 3D form factors, commonly used in industries like consumer electronics, automotive, aerospace, medical, and industrial sectors.

Rigid-flex PCBs enable dynamic movement, interconnections between multiple PCBs, compact packaging, and reduced reliance on external cables or connectors. They allow for lighter, thinner, and more rugged devices, with 3D shaping and improved assembly efficiency.

Rigid Flex PCB Products

Cemera Rigid Flex Module

VR Glass Rigid Flex PCB

6 Layer Rigid Flex

8 Layer pcb rigid flex

10 Layer semi flex pcb

12 Layer flexible rigid pcb

HDI Rigid Flex PCB

16 Layer rigid flex circuits

Robotic Rigid Flex Board

Request Rigid Flex PCB Quote Now

Manufacturing Capability

PCB attributes Flex Rigid-flex
Min Layer Count 1 1
Max Layer Count 12 ≤ 32
Min Core thickness .001″ (.025 mm) 3 oz (89 ml)
Max Finished Copper Weight (I/L) 2 oz (59 ml) 3 oz (89 ml)
Max Finished Copper thickness (O/L) 12 micron (.012 mm) 9 micron (.009 mm) (only for O/L)
Max Panel Size 12×18 12×18
Smallest Mechanical Drill Diameter .0079″ (.201 mm) .0071″ (.180 mm)
Smallest Laser Drill Diameter No .005″ (.127 mm)
Min Finished Hole Size .006″ (.152 mm) .006″ (.152 mm)
Max through Hole Aspect Ratio 10:1 10:1
Max Blind Via Aspect Ratio .75:1 .75:1
Min Trace and Space ≥ .0035”(.089 mm) ≥ .0035”(.089 mm)(rigid)
Min Pad Size for Test .016″ (.406 mm) .005” (.127 mm) (rigid)
Process Pad Diameter D + .014″ (.356 mm) (1-mil (.025 mm) annular ring) D + .014″ (.356 mm) (1-mil (.025 mm) annular ring)
Stacked Vias No No
Min Wire Bond Pad Size > .006″ (.152 mm) > .006″ (.152 mm)
Controlled Impedance Tolerance 10% 5%
Solder Mask Registration Within .002″ (.051 mm) Within .002″ (.051 mm)
Solder Mask Feature Tolerance .001″ (.025 mm) .001″ (.025 mm)
Solder Mask Min Dam Size .004″ (.102 mm) .001″ (.025 mm)
Min Diameter Route Cutter Available .019″ (.483 mm) .024″ (.610 mm)
Mechanical Routed Part Size Tolerance .003″ (.076 mm) .010″ (.254 mm)
Bow and Twist Tolerance N/A As per spec
Thickness Tolerance +/- .002″ (.051 mm) 10%
Sequential Laminations N/A 2
Buried Vias Yes Yes
Blind Vias Yes Yes
Conductive Filled Vias No Yes
Non Conductive Filled Vias No Yes

Manufacturing Process

Adhesive/Seed coating applied

An epoxy or acrylic adhesive is applied, or sputtering is used to create a thin copper layer for a plating key.

Copper foil added

Copper foil is added either by lamination to the adhesive (the more mainstream approach) or chemical plating onto the seed layer.

Drilling

Holes for vias and pads in flex substrates are typically drilled mechanically, often using a multi-panel setup.

Through-hole plating

Once the holes are made, copper is deposited and chemically plated in the same way as rigid PCB cores (commonly referred to as Cuposit).

Etch-resist printing

A photosensitive etch resist is coated onto the film surfaces, and the desired mask pattern is used to expose and develop the resist before the chemical etching of the copper.

Etching and stripping

After exposed copper is etched, the etch resist is chemically stripped from the flex circuit.

Coverlay or Covercoat

The top and bottom areas of the flex circuit are protected by coverlay layers which are cut to shape. There may be components mounted on sections of the flexible circuit, in which case the coverlay is also acting as a solder mask.

Cutting out the flex

The final step in creating the flex circuit is cutting it out. This is often referred to as “blanking”. The high-volume cost-effective blanking approach involves a hydraulic punch and die set, which involves reasonably high tooling costs.

Flexible and rigid laminating

The flex circuit is laminated into the panel along with the rigid and any other flexible sections, with additional adhesive, heat, and pressure. Multiple flex sections are not laminated adjacent to each other unless you are designing multi-layer flex.

Design Guidelines

Rigid flex printed circuit boards, or PCBs, serve a vital role across multiple industries where reliability is a must in less-than-ideal situations. They are an excellent go-between between the high-density circuitry of hardboards and the durability and flexibility of flexible circuits.

This guide highlights rigid flex PCB design guidelines, and for even more information, refer to our rigid flex design for manufacturing guide, and our Valu Builds brochure on low cost, high reliability rigid flex material layups.

Alternatively, if you’re a customer in need of custom rigid flex PCB solutions, contact us today to get a quote or set up a design consultation.

 

Rigid-flex circuit boards (PCBs) are ideal for environments subject to shock, vibration, and heat, as they are durable and reliable under mechanical stress. They are commonly used in military, aerospace, medical devices, cameras, and increasingly in consumer electronics like drones and wearable tech, due to their compact size, lightweight nature, and ability to endure harsh conditions.

These PCBs are particularly useful in applications where space and weight are limited, such as pacemakers and hearing implants. Their design reduces points of failure by eliminating connectors, making them more reliable. Rigid-flex PCBs can bend or fold without damage, allowing for more flexible designs and reducing assembly errors.

Overall, rigid-flex solutions are cost-effective, durable, and flexible, making them a preferred choice for industries requiring high performance in challenging environments. PAYPCB offers low-cost, high-performance rigid-flex circuits with dynamic flex properties that can withstand hundreds of thousands of bend cycles.

Rigid-flex PCBs are ideal for routing circuitry between multiple rigid boards and eliminating connectors with flexible cabling. They are particularly useful in confined spaces where the PCB must conform to a specific design. While generally more expensive than rigid boards, RAYPCB' rigid-flex PCBs can be cost-effective when combining multiple hard boards. Their lightweight nature makes them suitable for low-weight applications like drones, aerospace, and wearables. Additionally, their flexibility provides superior performance in high-shock and high-vibration environments.

Rigid-flex PCBs combine both rigid and flexible circuit elements, making them ideal for compact, high-performance designs that must endure mechanical stress. Effective design of rigid-flex circuits requires careful attention to several key factors:

  • Flex-to-Rigid Transitions:
    1. Smooth Transitions: Ensure the junction between flexible and rigid sections is smooth to avoid stress on the flexible parts. Exposing the flexible areas to excessive stress at this interface can lead to failure.

    2. Keep-Out Areas: Maintain a safety margin around the flex-to-rigid transition. Avoid placing pads, vias, or traces in this area, and position drill holes slightly further from the margin to prevent damaging the flexible sections.

  • Bend Radius:
    The flexibility of the PCB allows it to bend without damage. Ensure the bend radius is large enough to prevent stress on the conductors:

    1. 1-2 Layer Flexible Components: Minimum bend radius should be 6 times the thickness of the flexible section.

    2. 3+ Layer Flexible Components: Minimum bend radius should be 12 times the thickness.

  • Material Selection:
    1. Common Materials: Polyimide is commonly used for the flexible components, and FR4 for the rigid sections.

    2. No-Flow Prepreg: Prevents resin from flowing into the flexible areas during lamination, maintaining the integrity of the flex components.

    3. Laminate and Prepreg Selection: Limited options are available, so fabricators should be consulted for guidance. RAYPCB offers a wide range of UL 94 V-0 and RoHS-compliant rigid-flex constructions.

  • Layer Count and Stackup:
    1. The layer count should balance between rigid and flexible areas for optimal performance under shock and vibration.

    2. High-Density Routing: For high-density routing, layer counts can exceed 20, with flexible layers typically ranging from 1-4.

    3. The flex layers extend throughout the rigid sections to enhance performance.

  • Trace Routing and VIA Placement:
    1. Trace Routing: Traces on flexible components need to be wider to accommodate bending without stress. Trace width transitions at flex-to-rigid boundaries should be carefully managed to maintain impedance integrity.

    2. VIA Placement: Vias should be kept clear of the flex-to-rigid transition area. Typically, vias should be at least 0.050” (1.27mm) away from the transition to avoid reliability issues.

  • Heat Management:
    1. Heat Dissipation: Rigid sections offer more design options for heat dissipation. Flexible areas, due to their lower density, retain less heat. Place heat-generating components in areas where heat dissipation is optimal. The placement of flexible areas may also contribute to overall heat management.

RAYPCB is a trusted provider of high-reliability, fail-proof rigid-flex electronic packaging, designed to excel in high-shock and high-vibration environments. Our solutions are also ideal for weight and cost reduction when connecting four or more rigid boards electronically. For engineers seeking top-tier rigid-flex solutions for mission-critical components, RAYPCB is your go-to partner.

We offer the largest library of rigid-flex constructions, featuring ultra-thin dielectrics that help reduce weight in your designs. To learn more about our latest rigid-flex products and design specifications, visit our blog or request a copy of our rigid-flex design guidelines today!

Contact RAYPCB today to connect with one of our knowledgeable team members or to request a quote for your project. We're here to help you find the best rigid-flex solutions tailored to your specific needs. Reach out now to get started!

Stack Up Reference

2 Layer Rigid Flex PCB Stack-Up Reference

3 Layer Rigid Flex PCB Stack-Up Reference

4 Layer Rigid Flex PCB Stack-Up Reference

5 Layer Rigid Flex PCB Stack-Up Reference

6 Layer Rigid Flex PCB Stack-Up Reference

6 Layer Any layer HDI Rigid Flex PCB Stack-Up Reference

8 Layer HDI Blind and Buried Via Rigid Flex PCB Stack-Up Reference

8 Layer Any layer HDI Rigid Flex PCB Stack-Up Reference

12 Layer Any layer HDI Rigid Flex PCB Stack-Up Reference

Design, Manufacturing & Cost

Rayming Rigid flex PCB capabilities: 

Rigid Board: Up to 20 layer ( accept buried or blind hole design)  

Flex Board: 8 Layer ( Accept PI,Aluminum, Fr4 stiffener, and other special materials requirement ）

Estimate Cost Now, Pls send PCB file to Sales@raypcb.com, We will quote you Very Soon !

Rayming Rigid flex PCB board manufacturing solutions are custom designed for many top electronic industry. Fabricated with dependable high stardard quality control and  reliability, our Rigid flex Board are built to withstand the rigors of aerospace, Robot control, medical, and military applications. As a reliability replacement for wire and wire harness assemblies,rigid flex circuit provide a significant cost saving with no reduction in performance.Our pcb engineer team can assist you from early rigid-flex design stages of your application all the way to final production for all your flex and rigid-flex circuit needs.

A rigid-flex PCB consists of rigid PCB material combined with flexible PCB material, connected by a flexible adhesive material. The rigid sections provide mechanical support for components and the flexible sections allow dynamic movement and shaping.

The rigid sections are typically made of materials like FR-4, while the flexible sections use polyimide or other flexible dielectric materials. The layers are bonded together using advanced adhesion techniques. Conductive traces can be etched on both rigid and flexible layers to route signals between components.

Vias and component holes are plated through both rigid and flexible layers to enable vertical interconnections. Components are mounted on the rigid portions only, while the flexible portions provide dynamic interconnects between the rigid segments.

Rigid-flex PCBs enable:

  • Dynamic flexing, bending, folding, and wrapping
  • Interconnections between multiple PCBs
  • Complex, dense, and compact electronics packaging
  • Rugged devices with flex-resistant cabling
  • Lighter and thinner products by eliminating wires and connectors
  • 3D shaping and conformability
  • Reduced assembly cost by combining multiple PCBs

Compared to using discrete rigid PCBs with external cables or flex circuit interconnects, rigid-flex PCB technology provides a fully integrated solution with design, performance and reliability advantages.

A rigid-flex PCB combines rigid materials (like FR-4) with flexible materials (such as polyimide), offering both structural support and dynamic flexibility. The rigid sections provide stability for component mounting and heat dissipation, while the flexible sections enable interconnections that can bend or flex.

Key features:

  • Rigid segments: Used for mounting components and heat dissipation.
  • Flexible segments: Allow dynamic bending, folding, and 3D shaping.
  • Plated through holes: Connect layers vertically across both rigid and flexible areas.
  • Assembly: Components are mounted only on rigid parts, while flexible sections can bend or flex as needed.

The materials are bonded using advanced lamination techniques, ensuring durability under thermal and mechanical stresses. Proper design considerations include trace routing for flexibility, minimizing transition stress, controlling bend radius, and accommodating thickness variations between rigid and flexible areas. When well-designed, rigid-flex PCBs offer both flexibility and structural integrity for complex applications.

Designing a reliable rigid-flex PCB requires special considerations not needed for standard rigid PCBs. Key design factors include:

  1. Layer Stackup: Choose a balance between rigid and flexible layers based on component density, routing needs, and dynamic flexibility. Rigid layers typically use FR-4, while flex layers use polyimide. The stackup must balance flexibility, rigidity, impedance control, and manufacturability.

  2. Rigid-to-Flex Transitions: Proper management of intersections between rigid and flex sections is crucial to avoid stress-related failures. Use gradual transitions, wider annular rings, and minimize copper exposure near transitions.

  3. Bend Radius: Flexible segments must adhere to a minimum bend radius (typically 3mm to 10mm) to prevent damage to traces or layers. The bend radius depends on factors like material and copper thickness.

  4. Component Placement: All components must be placed on rigid areas, with a keepout zone around the edges to avoid overlap with flexible regions. High-stress components should be positioned away from rigid-flex transitions.

  5. Routing Considerations: Flexible layer traces must be wider and spaced appropriately to endure dynamic bending, avoid sharp angles, and follow the neutral bend axis. Copper density must be balanced to maintain performance and reliability.

These factors are critical for ensuring the functionality and durability of rigid-flex PCBs in dynamic and demanding environments.

Fabricating a rigid-flex PCB involves advanced techniques and precise processes, including:

  1. Materials Preparation: Rigid and flexible core materials are cleaned, coated, and conditioned for optimal adhesion.

  2. Imaging: Traces, pads, and features are created on inner and outer layers using lithography and etching.

  3. Hole Formation: Holes for components, vias, and tooling are drilled or punched, then plated with copper for vertical interconnects.

  4. Lamination: Rigid and flexible layers are aligned and bonded using high temperature, pressure, and advanced adhesives.

  5. Outer Layer Imaging: The outer layer traces are patterned using lithography and etching.

  6. Solder Mask and Finish: Solder mask is applied, and the surface is treated with finishes like ENIG or immersion tin.

  7. Singulation: The PCB panel is precision-routed to separate individual boards, which may have complex shapes.

  8. Testing: Electrical testing and automated optical inspection ensure functionality and accuracy.

  9. Assembly: Components are mounted on the rigid sections, and the PCB is shaped into a 3D form as required.

The process requires expertise in surface preparation, high-accuracy imaging, controlled lamination, precise drilling and hole plating, and design-for-manufacturability (DFM) techniques to optimize performance and reliability.

Rigid-flex PCBs are more expensive than standard rigid PCBs due to several factors:

  1. Layer Count: More layers increase material, lamination complexity, and fabrication costs, with higher layer counts costing exponentially more.

  2. Panel Utilization: Complex geometries lead to lower panel utilization, increasing costs due to less PCB area per panel.

  3. Finishing and Coatings: Specialized solder mask, coverlay, and surface finishes, as well as techniques like thick copper and buried vias, add to the cost.

  4. Flexible Material Type: Durable, heat-resistant flex materials (e.g., polyimide, LCP) are more expensive.

  5. Registration Accuracy: Tighter alignment and drilling tolerances require advanced equipment, increasing costs.

  6. Design Complexity: Dense routing, high component counts, and HDI features raise fabrication difficulty and costs.

  7. Low Volume: Smaller production runs prevent economies of scale, increasing the cost per board.

  8. Testing: Extensive inspection and electrical testing add to the overall cost.

Additionally, there are engineering costs for specialized design, simulation, prototyping, documentation, and qualification.

Rigid-flex PCBs are used in a wide range of applications due to their ability to combine flexibility with rigidity. Key application areas include:

  1. Consumer Electronics: Wearables, smartphones, laptops, and cameras use rigid-flex PCBs for compact size, rugged cabling, and dynamic positioning.

  2. Automotive Electronics: Applications like automotive cameras, powertrain systems, LED lighting, and infotainment systems rely on rigid-flex PCBs for shape flexibility and vibration resistance.

  3. Medical Equipment: Devices like hearing aids, blood analyzers, surgical tools, and implants benefit from rigid-flex PCBs for fitting in tight, curved spaces and providing dynamic interconnections.

  4. Industrial: Robotics, motion control, telemetry, and navigation systems use rigid-flex PCBs for rugged, shape-conforming designs.

  5. Military/Aerospace: Avionics, guidance systems, communications, and navigation electronics in defense and aerospace applications require rigid-flex PCBs for compact, durable performance.

  6. Advanced HDI: Used as carrier boards for high-density interposers and multi-chip modules (MCMs) in advanced packaging applications like ASICs.

Rigid-flex PCBs enable designs that go beyond the capabilities of standard rigid boards, supporting dynamic motion, flexibility, and 3D shaping for diverse industries.

Rigid-flex PCBs offer several advantages over traditional rigid PCBs:

  1. Dynamic Flexing and Motion: Flexible sections allow for motion, vibration absorption, twisting, bending, and wrapping, which rigid PCBs cannot achieve.

  2. Lightweight and Compact: By eliminating external cables and connectors, rigid-flex PCBs reduce size and weight, making them ideal for portable and space-constrained designs.

  3. Enhanced Reliability: The integrated design minimizes interconnection failures, improving overall system reliability compared to systems relying on cables and connectors.

  4. Complex Shaping: Rigid-flex PCBs can be shaped into complex 3D forms, fitting into product enclosures and mechanical designs, unlike rigid PCBs that are planar.

  5. Simplified Assembly: Components can be pre-mounted on the rigid sections, enabling easier system assembly by simply folding the PCB into shape.

  6. Design Flexibility: Rigid-flex PCBs allow for the placement of rigid areas only where necessary, optimizing design flexibility.

  7. Cost Savings: Fewer parts, reduced assembly steps, and streamlined handling result in cost savings compared to hybrid rigid/flex solutions.

Rigid-flex PCBs provide performance and reliability benefits for applications requiring dynamic movement, vibration resistance, compactness, and 3D assembly, while also reducing complexity and costs compared to traditional and hybrid solutions.

When designing rigid-flex PCBs, follow these key guidelines for optimal performance and manufacturability:

  1. Layer Stackup: Choose sufficient layers for rigidity, heat dissipation, and signal integrity, while minimizing flexible layers to only what’s necessary for dynamic motion. Balance impedance control, flex/rigid transitions, and manufacturability.

  2. Rigid-Flex Transitions: Use gradual tapers or teardrop shapes at transitions, avoid placing components or vias near these areas, and adjust solder mask pullbacks. Analyze transitions with stress simulations.

  3. Bend Radius: Ensure bends don’t exceed the minimum radius and position them along the neutral axis of the flex layers. Account for dynamic flexing stresses that may reduce the bend radius over time.

  4. Flexible PCB Design Rules: Use wider trace/space dimensions, avoid acute angles, and balance copper density across flex layers. Route critical signals near the neutral bend axis.

  5. Board Tolerances: Allow for alignment variability and dynamic shape changes during use. Include design margins for critical features.

  6. Simulation: Use 3D CAD simulations to verify shape and motion, perform stress analysis on transitions, model thermal performance, and check signal integrity, especially across bends.

  7. Manufacturing and Testing: Use standard materials when possible, account for thickness variations between rigid and flex areas, and provide test points for critical signals. Follow fabrication shop DFM guidelines.

By adhering to these principles, rigid-flex PCBs can be designed for optimal flexibility, reliability, and manufacturability, ensuring they meet performance requirements.

Engineers use a variety of software tools to design and analyze rigid-flex PCBs, addressing tasks such as layout, 3D modeling, simulation, and documentation:

  • PCB Layout: Tools like Altium Designer, Cadence Allegro, Mentor Xpedition, and Zuken CR-8000 help with component placement, trace routing, and layer stack-up optimization.

  • 3D Modeling: Tools such as Cadence OrCAD 3D Modeler, Altium 3D PCB Visualization, and SolidWorks PCB 3D Modeling aid in visualizing the physical design and checking for mechanical fit.

  • Simulation and Analysis: Ansys Q3D Extractor (signal integrity), Ansys HFSS (antenna design), Cadence Clarity 3D Solver (thermal and mechanical analysis), and Mentor Valor Process Preparation (manufacturability) ensure the PCB’s performance and manufacturability.

  • Documentation: Tools like AutoCAD, PDF 3D, and illustration software generate necessary documentation and assembly instructions.

These tools help engineers optimize design parameters and ensure rigid-flex PCBs are functional, manufacturable, and reliable.

Summary of Key Points on Rigid-Flex PCBs:

  • Structure: Rigid-flex PCBs combine rigid materials (like FR-4) and flexible materials (like polyimide), allowing for dynamic flexing and 3D shaping.

  • Design Considerations: Careful management of layer stackup, rigid-to-flex transition geometry, bend radius, trace routing, and component placement is essential for optimal performance.

  • Functionality: Rigid portions provide mechanical support, while flexible sections enable out-of-plane interconnections between rigid areas.

  • Benefits: Rigid-flex PCBs offer advantages in terms of space, weight reduction, complexity, and reliability compared to traditional rigid PCBs, especially for compact or complex designs.

  • Cost: While rigid-flex PCBs are more expensive than rigid boards, the cost can be offset by benefits such as system miniaturization, consolidation, and simplified assembly.

  • Applications: Common in consumer electronics, automotive, aerospace/defense, medical devices, and industrial automation, where dynamic motion, vibration resistance, and compact, conformal designs are required.

  • Design Best Practices: Following guidelines for flex/rigid transitions, bend radius, trace routing, and using tools for simulation and modeling ensures reliable and efficient performance.

  • Conclusion: Rigid-flex PCB technology provides unique benefits for products requiring dynamic flexibility, vibration resistance, lightweight structures, and conformal assembly. By understanding design, manufacturing, and cost factors, engineers can leverage rigid-flex PCBs effectively.