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What is Rigid Flex PCB ?

Offering a variety of cost effective solutions and capabilities to manufacture single or double flex with multilayer rigid PCB, we will help you exceed all your applications requirements.

Rigid Flex PCB
Flexible PCB
Turnkey Assembly
Multilayer PCB

Rigid Flex PCB Manufacturing Service

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 ）

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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.

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Introduction

A rigid-flex printed circuit board (PCB) combines rigid FR4 board sections and flexible polyimide circuits into a single integrated assembly. Rigid-flex PCBs provide solutions for applications requiring mechanical flexibility, space efficiency, lightweight construction, and dynamic electrical connections.

This article provides an in-depth overview of rigid-flex technology covering:

  • Benefits and capabilities
  • Materials and construction
  • Flex-rigid-flex configurations
  • Design rules and guidelines
  • Modeling considerations
  • Manufacturing processes
  • Reliability factors
  • Cost tradeoffs
  • Applications of rigid-flex boards

Understanding rigid-flex PCB technology enables exploiting its advantages in products requiring flexible circuits and interconnects.

rigid flex pcb manufacturers

Benefits and Capabilities

Rigid-flex PCBs offer a number of advantages:

  • Dynamic flexing and three-dimensional configurations
  • Folding and shaping into compact mechanical envelopes
  • Redistribution routing between rigid areas
  • Lower weight than discrete cabling
  • Eliminates connectors between rigid boards
  • Improves product reliability and quality
  • Consolidates multiple PCBs into single assembly
  • Design flexibility to integrate subsystems

Materials and Construction

Rigid-flex PCBs integrate a number of materials:

Rigid Sections

  • FR4 glass reinforced laminates
  • Provide mechanical structure
  • House high component densities

Flexible Sections

  • Polyimide films like Kapton
  • Allow bending and flexing
  • Thickness down to 1 mil

Bonding Layers

  • Acrylic or epoxy adhesive films
  • Bonds polyimide films to FR4 laminates

Coverlayers

  • Polyimide coatings protect circuits
  • ALLOW SOLDERING FLEX AREAS

Flex-Rigid-Flex Configurations

Common constructions include:

2 Layer Flex-Rigid

  • One flex layer bonded to one rigid layer

Multi-Layer Flex-Rigid

  • One flex layer attached to multilayer rigid board

Multi-Flex Rigid

  • Multiple flex layers bonded to rigid section

Rigid-Flex-Rigid

  • Rigid boards interconnected by flex section

Flex-Rigid-Flex

  • Flexible circuits extending from both sides
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rigid-flex_pcb

Design Rules and Guidelines

Rigid-flex PCBs require following specialized design practices:

Layer Stackup

  • Use symmetric stackup around flex area
  • Ensure adequate bonding layer widths
  • Watch out for rigid-flex thickness changes

Layout

  • Avoid small pads and traces in flex area
  • Watch trace angles entering rigid areas
  • Use teardrops on pads at transitions

Copper Relief

  • Provide clearance cuts in copper around flex
  • Prevent stresses from shearing copper

Stress Relief

  • Allow sufficient bend radius
  • Incorporate intermittent gaps along flex

Stiffening Elements

  • Add rigid stiffeners for structural support
  • Manage dynamic bend regions

Modeling Considerations

Use modeling tools for electrical, mechanical and thermal analysis:

Electrical

  • Model impedance of traces in flexible sections
  • Ensure impedance consistent through rigid-flex transition

Mechanical

  • FEA stress and fatigue analysis
  • Optimize tradeoff between flexibility and durability

Thermal

  • Heat transfer variation between rigid and flex areas
  • Ensure thermal management of components
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Manufacturing Processes

Process flow of Rigid-Flex PCB 1

Fabricating rigid-flex PCBs requires specialized sequential lamination techniques:

  • Bond flex circuit layers to rigid sections in lamination presses
  • Use precision drills/routers to create clearance openings
  • Controlled depth cutting prevents material burring
  • Etch copper relief patterns around flex areas
  • Limit number of angles in routing rigid sections
  • Solder mask application requires custom tooling
  • Precise process control is critical throughout

Reliability Considerations

Factors affecting rigid-flex PCB reliability:

Design

  • Avoiding flex overload through modeling
  • Providing adequate bend radius

Materials

  • Adhesion between rigid and flex layers
  • Characteristics like Tg and moisture absorption

Processes

  • Bonding and lamination parameters
  • Drilling and routing quality
  • Depth control of cuts into flex

Testing

  • Mechanical cycling and bend testing
  • Electrical continuity through dynamic flexing
  • Thermal shock and vibration
  • Coefficient of thermal expansion mismatches

Cost Tradeoffs

Rigid-flex PCBs allows design consolidation but at increased cost: Increased Costs Low volume manufacturing Additional process steps Specialized materials Complex designs More post-assembly inspection Cost Savings Eliminate connectors and cabling Reduce piece part count Decrease assembly time and cost Miniaturization due to efficient use of space Product reliability improvements
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Applications of Rigid Flex Boards

rigid flex board

Common uses of rigid-flex technology:

  • Consumer electronics – cell phones, laptops
  • Computer components – HDDs, optical drives
  • Medical – endoscopes, hearing aids
  • Defense and aerospace – guided missiles
  • Automotive – dynamic flex interconnects
  • Robotics – arms and manipulators
  • Test and measurement equipment

Conclusion

Rigid-flex PCB technology provides integrated solutions for designs requiring flexibility and interconnects between moving subassemblies. Realizing the advantages requires expertise in specialized materials, modeling, fabrication processes and reliability testing. When applied appropriately, rigid-flex PCBs enable more compact, lighter weight and robust product designs compared to traditional discrete flex circuits and cabling.

Frequently Asked Questions

Here are some common questions on rigid-flex PCB technology:

Q: What are the main benefits of rigid-flex PCBs?

They allow dynamic flexing and interconnections, consolidation of multiple PCBs, lighter weight assembly, and improved reliability.

Q: What are some typical applications of rigid-flex boards?

Consumer products, computer components like drives, medical devices, robotics, defense, automotive electronics are common applications.

Q: What are the major design considerations for rigid-flex PCBs?

Stackup symmetry, adequate bonding widths, copper relief cuts, component layout, controlling flex stresses, and smooth impedance transitions are key considerations.

Q: How are rigid-flex PCBs manufactured?

Specialized lamination, drilling and routing processes are required along with precise process control.

Q: What drives the higher cost of rigid-flex PCBs?

Low volume production, additional process steps, advanced materials, complex designs and more inspection all contribute to increased costs.