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 Manufacturing Service
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 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.
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:
- FR4 glass reinforced laminates
- Provide mechanical structure
- House high component densities
- Polyimide films like Kapton
- Allow bending and flexing
- Thickness down to 1 mil
- Acrylic or epoxy adhesive films
- Bonds polyimide films to FR4 laminates
- Polyimide coatings protect circuits
- ALLOW SOLDERING FLEX AREAS
Common constructions include:
2 Layer Flex-Rigid
- One flex layer bonded to one rigid layer
- One flex layer attached to multilayer rigid board
- Multiple flex layers bonded to rigid section
- Rigid boards interconnected by flex section
- Flexible circuits extending from both sides
Design Rules and Guidelines
Rigid-flex PCBs require following specialized design practices:
- Use symmetric stackup around flex area
- Ensure adequate bonding layer widths
- Watch out for rigid-flex thickness changes
- Avoid small pads and traces in flex area
- Watch trace angles entering rigid areas
- Use teardrops on pads at transitions
- Provide clearance cuts in copper around flex
- Prevent stresses from shearing copper
- Allow sufficient bend radius
- Incorporate intermittent gaps along flex
- Add rigid stiffeners for structural support
- Manage dynamic bend regions
Use modeling tools for electrical, mechanical and thermal analysis:
- Model impedance of traces in flexible sections
- Ensure impedance consistent through rigid-flex transition
- FEA stress and fatigue analysis
- Optimize tradeoff between flexibility and durability
- Heat transfer variation between rigid and flex areas
- Ensure thermal management of components
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
Factors affecting rigid-flex PCB reliability:
- Avoiding flex overload through modeling
- Providing adequate bend radius
- Adhesion between rigid and flex layers
- Characteristics like Tg and moisture absorption
- Bonding and lamination parameters
- Drilling and routing quality
- Depth control of cuts into flex
- Mechanical cycling and bend testing
- Electrical continuity through dynamic flexing
- Thermal shock and vibration
- Coefficient of thermal expansion mismatches
Applications of Rigid Flex Boards
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.