Recently, Best Technology faced a huge challenge in a 2oz copper rigid flex PCB manufacturing, this board appeared simple on the drawing but revealed multiple layers of engineering challenges once entering mass production. But finally, we finished this project very well and overcome this challenge, letâs see what are the challenges on this project and how does our team overcome them!
Project Introduction
The board used a 70/25 double-sided adhesive ED flexible substrate with PI25/AD50 coverlay, coupled with a 2+2 layers dual access structure that required thick copper, small annular rings, narrow spacings, and FR4 stiffeners with extremely limited clearance. Each of these parameters independently creates difficulty, but combined, they demand precise collaboration between engineering, fabrication, and process control.
This article explains:
Why the design was inherently difficult
What manufacturing risks were present
How our engineering team solved each challenge
What PCB designers should avoid in similar projects
Flexible substrate: 70/25 double-sided adhesive ED copper
Coverlay: PI 25 ”m + Adhesive 50 ”m
Base copper: 2 oz copper
Layer count: Four-layer rigid-flex structure
Critical routing: 0.15 mm minimum trace/space
Plated hole: 0.66 mm with hole spacing of only 0.60 mm
Annular ring: 0.05 mm on certain pads
Stiffener: FR4 stiffener with 0.95 mm stiffener hole and 0.31 mm ribs
This combination is common in advanced HDI rigid-flex PCB manufacturing, yet its manufacturability depends heavily on copper behavior, adhesive flow, and drilling tolerances.
Why This Rigid-Flex PCB Was Inherently Difficult?
1. Thick copper increases side-etching risk
With 2 oz copper, the etching rate is higher and lateral etchâoften called side-etchâis harder to control. In this case, the side-etching amount reached: 0.0070 ± 0.003 mm. For ultra-fine traces in a rigid-flex PCB design, this will eat into the design margin.
2. Small annular rings compromise via reliability
Pads with 0.05 mm annular ring severely restrict drilling tolerance. In flex-rigid PCB fabrication, annular rings below 0.10 mm are classified as high-risk features.
3. Extremely tight stiffener clearance
The stiffener needed:
±0.20 mm placement tolerance
±0.05 mm drilling tolerance
But the designer only left 0.15 mm clearance, causing a mismatch between rigid-flex PCB stiffener alignment tolerance and actual manufacturing capability.
4. Thin FR4 stiffener ribs cause glue overflow
Ribs only 0.31 mm wide cannot allow adhesive to retreat during bonding, causing pure glue to overflow and block the stiffener holes.
Technical Challenge #1: Thick Copper Etching with Narrow Spacing
A 2 oz thick copper PCB combined with:
0.15 mm trace/space
0.05 mm annular ring
0.66 mm PTH
creates a situation where compensation is unavoidable.
However, after compensation (~0.007 mm), the remaining trace width would drop to:
0.08 mm (0.15 â 0.07 mm)
This is below the safe manufacturability range of most rigid-flex PCB suppliers.
Best Technology’s solution
Eliminated compensation on 0.15 mm traces
Implemented fine-tuned etching control
Maintained ~0.10 mm final copper width
Ensured full electrical reliability
This is a proven strategy in advanced rigid-flex PCB manufacturing for thick-copper builds.
Technical Challenge #2: Annular Ring Integrity in Plated Through Holes
Annular rings <0.10 mm are extremely vulnerable to:
Drill wander
Etching undershoot
Copper thinning
This is especially critical in high-reliability rigid-flex PCBs, where via integrity is essential.
Best Technology’s solution
Applied rigid-board-level PTH plating process
Improved copper thickness inside the via barrel
Adjusted drilling control to 0.65 ± 0.075 mm
Customer accepted partial ring breakage as long as electrical integrity remained intact
This ensured consistent via performance even in ultra-dense rigid-flex PCB layouts.
Technical Challenge #3: Stiffener Bonding, Alignment, and Adhesive Overflow
1. Why stiffener tolerance was problematic
In rigid-flex PCB assembly, stiffeners are critical for mechanical reinforcement. However:
Hole spacing was only 0.60 mm
Stiffener clearance only 0.15 mm per side
Combined tolerance ±0.25 mm
This inevitably leads to the stiffener covering the pads unless advanced alignment controls are used.
2. Why glue overflow occurs
Thin ribs (0.31 mm) cannot provide an escape path for adhesive. During lamination:
The glue squeezes into the holes
Holes become blocked
Boards fail inspection
3. Best Technologyâs engineered solution
Pre-laminated pure adhesive onto FR4 stiffener
Re-drilled stiffener holes after bonding
Greatly reduced glue overflow
Added 100% AOI + manual inspection for hole clearing
Rejected defective boards, shipped only fully passing units
This is a common best practice in flex PCB stiffener processing when tolerances are tight.
DFM Guidelines for Rigid-Flex PCB Designers
Avoid annular rings under 0.15 mm, especially in 2 oz copper flex-rigid PCB design.
Avoid combining thick copper with fine lines, this will increase manufacturing risk.
Ensure stiffener clearance > total tolerance stack-up. If your clearance is smaller than the alignment tolerance, the stiffener will inevitably shift.
Keep stiffener ribs â„0.5 mm
Send your design for DFM review before finalizing. A goodrigid-flex PCB manufacturer will help adjust the stack-up, drill size, and stiffener layout to avoid expensive redesigns.
This case demonstrates how a complex rigid-flex PCBâwith 2 oz copper, ultra-fine traces, small annular rings, and extreme stiffener constraintsâcan be successfully manufactured through detailed engineering, advanced process control, and disciplined quality screening.
Best Technology combines strong fabrication capability with practical DFM insight, enabling customers to produce compact, reliable, and manufacturable rigid-flex PCB designs that perform consistently under demanding conditions.
If you need support with your next rigid-flex or flex PCB project, our engineering team is ready to assist with stack-up review, DFM checks, or trial builds.
EBest Circuit (Best Technology) is the leading rigid flex PCB manufacturer that delivers exceptional speed, quality, and transparency. With our industry-leading â24-hour rapid prototypingâ, we ensure your projects move forward without delay. Our advanced manufacturing processes guarantee high-performance PCBs with precision and reliability, while our âtransparent pricingâ means no hidden costsâjust fair, competitive rates. Whether you need a âsingle prototype or mass productionâ, we support â1-piece minimum ordersâ, making us the ideal partner for startups and enterprises alike. Fast turnaround, cutting-edge technology, and honest pricingâtrust EBest Circuit (Best Technology) to power your innovations efficiently and affordably.
What Is Rigid Flex PCB?
Rigid flex PCB merges rigid and flexible regions into a single board, allowing dynamic bending in specific areas while providing stable support for components. Unlike traditional rigid PCBs, which lack flexibility, or pure flexible PCBs, which may lack structural integrity, Rigid Flex PCB achieves a balance through layer-by-layer integration. This design is particularly valuable in applications where space is constrained or dynamic movement is required, such as wearable devices and automotive electronics. The technology relies on advanced materials and manufacturing processes to ensure both mechanical durability and electrical performance.
What Is Material of Rigid Flex PCB?
Hereâs material of rigid flex PCB:
Flexible Substrates:
Polyimide (PI): A high-temperature-resistant material with excellent flexibility and dimensional stability, ideal for dynamic bending applications.
FCCL (Flexible Copper Clad Laminate): Composed of PI or polyester film bonded to copper foil, FCCL forms the base of flexible layers. Options include adhesive-based FCCL (cost-effective but thicker) and adhesive-less FCCL (thinner and more flexible) .
Polyamide: A cost-effective alternative to PI, suitable for low-flex applications.
Rigid Substrates:
FR-4: The most common rigid material, offering good mechanical strength and thermal stability.
High-Performance Materials: For advanced applications, materials like Rogers RT/duroid or ceramic-reinforced composites are used to meet high-frequency or extreme-temperature requirements.
Copper Foil:
Electrolytic Copper (ED): Cost-effective but less flexible, suitable for static or low-flex regions.
Rolled Annealed (RA) Copper: Exhibits superior ductility, making it ideal for high-flexibility areas .
Adhesives:
Epoxy Resins: Used to bond rigid and flexible layers, ensuring strong adhesion and thermal resistance.
Acrylic-Based Adhesives: Offer transparency and flexibility, suitable for display modules.
Cover Lays:
PI Cover Lays: Protect flexible circuits from environmental factors while maintaining flexibility.
FR-4 Cover Lays: Provide added rigidity in hybrid regions.
Solder Masks:
Liquid Photoimageable (LPI) soldermasks are applied to both rigid and flexible areas to prevent oxidation and ensure solderability.
Stiffeners:
Rigid materials like FR-4 or metal plates are added to reinforce areas where components are mounted, enhancing mechanical stability.
Weight Reduction: Eliminating bulky connectors and harnesses leads to lighter assemblies, critical for aerospace and portable electronics.
Improved Thermal Management: Rigid layers provide better heat dissipation, while flexible layers prevent thermal stress in dynamic areas.
Design Flexibility: Complex 3D layouts are possible, enabling innovative product designs.
Cost-Effectiveness in Volume: While initial costs are higher, mass production reduces per-unit expenses due to simplified assembly.
High Performance: Supports high-frequency signals and dense routing, meeting demands of advanced electronics.
What Are Disadvantages of Rigid Flex PCB?
Despite its advantages, Rigid Flex PCB has limitations:
Higher Initial Costs: Material and manufacturing complexity drive up prototype and low-volume production costs.
Design Complexity: Requires specialized expertise to balance rigidity, flexibility, and thermal expansion.
Manufacturing Challenges: Precise alignment and lamination processes are critical, increasing the risk of defects.
Limited Flexibility Cycles: Repeated bending can degrade performance over time, especially in high-stress applications.
Thermal Expansion Mismatch: Differences in CTE (Coefficient of Thermal Expansion) between rigid and flexible layers may cause delamination.
Testing Difficulty: Inspecting and repairing hybrid boards is more challenging than standard PCBs.
Environmental Sensitivity: Flexible materials may degrade in harsh conditions (e.g., extreme temperatures or humidity).
How to Design Rigid-flex PCB to Reduce Production Cost?
Designing for cost efficiency in Rigid Flex PCB involves balancing performance requirements with manufacturing feasibility. Here are practical strategies to minimize production costs:
Simplify Layer Stack-Up: Use the minimum number of layers necessary for your design. A 4-layer configuration (2 rigid + 2 flex) is often sufficient for most applications, avoiding the premium costs of multi-layer boards unless advanced routing is essential.
Standardize Material Selection: Choose widely available materials like FR-4 for rigid sections and PI for flex layers to leverage economies of scale. Reserve high-performance materials for specific critical regions rather than the entire board.
Optimize Flex Zone Size: Limit flexible regions to areas where bending is absolutely necessary. Use rigid sections for component-heavy zones to reduce the amount of expensive flex material and processing.
Choose Cost-Effective Copper Foil: Use electrolytic copper (ED) for rigid and low-flex areas, and reserve rolled annealed (RA) copper for high-flex zones only, where its superior ductility is truly needed.
Simplify Via Design: Prioritize through-hole vias in rigid sections, as they are cheaper than microvias or blind vias. Minimize vias in flex layers to reduce the need for complex coverlay processing.
Maximize Panel Utilization: Work with manufacturers to design boards that fit efficiently on standard panels, reducing material waste. Symmetrical or modular designs are ideal for maximizing the number of boards per panel.
Relax Non-Critical Tolerances: Specify achievable bend radii (typically 3-5 times the flex layer thickness) and allow looser dimensional tolerances where possible to avoid costly precision manufacturing adjustments.
Leverage Adhesive-Based FCCL for Prototyping: Use cost-effective adhesive-based flexible copper clad laminates for initial prototypes to validate designs before committing to more expensive adhesive-less materials.
Integrate Passive Components: Embed resistors, capacitors, or inductors into the PCB layers to reduce the number of surface-mount components, lowering assembly costs and simplifying the manufacturing process.
Collaborate Early with Manufacturers: Engage manufacturers in the design phase for DFM (Design for Manufacturability) feedback. They can suggest cost-effective alternatives, such as standardizing hole sizes or avoiding complex surface finishes.
How to Choose A Trusted Rigid Flex PCB Manufacturer?
Technical Expertise: Look for manufacturers with a proven track record in Rigid Flex PCB fabrication, including experience with complex stack-ups, materials like PI and FR-4, and advanced processes such as laser drilling and automated lamination.
Certifications and Compliance: Ensure the manufacturer adheres to industry standards like IPC-6012 (rigid PCBs), IPC-6013 (flexible PCBs), and ISO 9001 for quality management, demonstrating a commitment to consistency and reliability.
Advanced Equipment: State-of-the-art facilities with equipment like CNC drilling, automated optical inspection (AOI), and vacuum lamination machines are essential for precise fabrication, especially for intricate flex zones.
Prototyping Capabilities: A manufacturer offering rapid prototyping services allows you to test designs quickly and cost-effectively, identifying and resolving issues before full-scale production.
Quality Control Processes: Robust testing procedures, including bend cycle testing, thermal shock testing, and impedance control verification, ensure that the final product meets performance and reliability standards.
Supply Chain Stability: Choose manufacturers with strong relationships with material suppliers to minimize delays and cost fluctuations, particularly for specialized components like high-temperature adhesives or premium copper foils.
Transparent Communication: A responsive team that provides clear updates on production timelines, cost breakdowns, and design feedback is essential for a smooth collaboration and successful project execution.
How Much Does Rigid Flex PCB Cost?
The cost of Rigid Flex PCB varies based on factors such as layer count, material selection, design complexity, and production volume. Hereâs a general cost overview in USD for small to medium batches:
4-Layer Rigid Flex PCB: $10 to $30 per board, suitable for basic designs with moderate flex requirements.
6-Layer Rigid Flex PCB: $20 to $60 per board, ideal for mid-level complexity with dual-sided routing and multiple flex zones.
8-Layer Rigid Flex PCB: $40 to $120 per board, designed for high-density interconnects and advanced functionalities like embedded components.
To reduce costs effectively:
Increase Order Volume: Larger batches lower per-unit costs by spreading setup and tooling expenses across more boards.
Simplify Design: Reduce the number of flex zones, use standard materials, and avoid unnecessary features like exotic surface finishes.
Optimize Panelization: Maximize the number of boards per panel to minimize material waste and improve production efficiency.
Negotiate with Suppliers: Long-term partnerships with manufacturers can lead to discounted pricing, especially for repeat orders or large-scale projects.
Conclusion
Rigid Flex PCB represents a leap forward in PCB technology, offering unmatched flexibility and reliability for modern electronic devices. By understanding its core components, design strategies, and manufacturer selection criteria, engineers can harness its full potential while keeping costs in check. From material choice to layer stack-up, every decision plays a role in creating a balance between performance and affordability. For businesses seeking high-quality Rigid Flex PCBs tailored to their unique needs, EBest Circuit (Best Technology) stands ready to deliver innovative solutions. With a focus on precision manufacturing, cost efficiency, and technical expertise, our team is committed to bringing your designs to life. Contact us today atsales@bestpcbs.com for a detailed quote and letâs transform your concepts into cutting-edge electronic products.
The birth and development of FPC (Flexible Printed Circuit) and PCB(Printed Circuit Board) have given rise to a new product called the rigid flex PCB. Therefore, a flexible-rigid combination board is a circuit board that combines a flexible circuit with a rigid circuit through processes such as lamination, according to relevant technical requirements, resulting in a circuit board that possesses both the characteristics of FPC and PCB.
What Is Rigid Flex PCB?
A rigid flex PCB is a composite type of circuit board that combines flexible printed circuit boards (FPC) with rigid printed circuit boards (PCB) through specific processes. It integrates the flexibility of FPC and the rigidity ofPCB, possessing both characteristics of FPC and PCB. It can be folded or bent to reduce space occupation and can solder complex components, offering higher stability and reliability.
Best technology focus on high quality rigid-flex PCB design, prototype and manufacturing over 18 years. So we can flexibly handle various emergencies encountered in production based on our rich work experience to achieve fast delivery. Meanwhile, we have our own complete PCB manufacturing industry chain and advanced production machines, so we can control the cost of the entire production process well and provide customers with high-quality products at competitive prices. Please feel free to contact us at sales@bestpcbs.com if you have any request for rigid flex PCB.
Rigid Flex PCB Layer Stackup
1. Basic layered architecture
The stacked structure of the rigid-flexible board achieves functional partitioning through the alternating combination of rigid materials and flexible materials:
âOuter rigid layerâ: Usually uses FR4 fiberglass board to provide mechanical support and component installation stability, while achieving electrical isolationâ.
âIntermediate flexible layerâ: It is composed of polyimide (PI) film or polyester (PET), and is combined with rolled & annealed copper or electrolytic copper to form a conductive line to achieve bending connection functionâ.
âAdhesive layerâ: Use thermosetting adhesive (such as epoxy resin) or low-flow adhesive semi-cured sheet to seamlessly combine the rigid layer and the flexible layer to enhance structural stabilityâ.
Four-layer structure: double-layer FPC substrate + gold finger interface + FR4 filling area + hollow layered design, taking into account plug-in stability and flexibility.
2. Material configuration and function
Rigid substrate
FR4 fiberglass board: high temperature resistance, good insulation, thickness 0.2â3.2 mm, used for support and heat dissipation.
Flexible substrate
Polyimide (PI) film: high temperature resistance (>300°C), low deformation, thickness 12.7â127ÎŒm, suitable for dynamic bending scenarios.â
Conductive layer
Rolled copper (smooth and ductile) or electrolytic copper (low cost), thickness 12â35 ÎŒm, used for signal transmission.
Protective layer
Coverlay: PI or PET material, thickness 12.7â127 ÎŒm, moisture-proof, anti-pollution and solder-resistant.
3. Layer classification and typical application
Single-sided board
Structural features: There is a conductive circuit layer on only one side, and the other side is covered with a substrate or insulating ink, which is transparent under strong light (excluding special process requirements).
Application scenarios: Simple circuit connection scenarios, such as low-complexity sensor modules.
Double-sided board
Structural features: There are conductive circuit layers on both sides, and the electrical connection between layers is achieved through metallized holes (PTH holes).
Application scenarios: General electronic devices, such as basic communication modules.
Multi-layer board
Definition: 3 or more circuit layers are superimposed through a “sandwich” structure, combining rigid substrates with flexible substrates.
Typical layer range: 4, 6, and 8 layers are common, and high-complexity designs can reach 12 or more layers.
Rigid Flex PCB Layer Stackup
What Are the Advantages of Rigid Flex PCB?
Space optimization and lightweight design
Space saving: Through the integrated design of flexible circuits and rigid circuits, the connection requirements of traditional hard boards and flexible boards are reduced, and the space utilization rate is optimized.
Light weight: The weight of flexible materials is only about 10% of that of hard boards, which greatly reduces the overall weight of the equipment.
Shrinkage: Supports three-dimensional folding design, suitable for miniaturized products such as wearable devices and folding screen mobile phones.
Improved reliability
Reduce connection point failures: The integrated structure of the whole board reduces the risk of poor welding or connector failure and improves long-term stability.
Environmental impact resistance: Resistant to high and low temperatures (-55â~125â), chemical corrosion and ultraviolet rays, suitable for harsh environments such as automotive electronics and aerospace.
Vibration resistance: The flexible area can absorb mechanical resonance and reduce the impact of vibration and impact on components.
Cost-effectiveness
Reduce assembly costs: Reduce the number of connectors, simplify the production process, and reduce labor and procurement costs.
Reduce maintenance costs: High reliability design extends product life and reduces the frequency of later repairs.
Signal and heat dissipation performance optimization
âSignal integrityâ: Short transmission path and controlled impedance reduce signal attenuation and support high-speed data transmission (such as industrial camera image processing).
âEMC performance enhancementâ: The shielding design of the flexible area reduces electromagnetic interference (EMI) and improves the ability to resist radio frequency interference.
âHigh heat dissipation efficiencyâ: By extending the copper layer area, the heat dissipation path is expanded and the thermal resistance is reduced, which is suitable for high-power equipment.
Structural flexibility and multi-functional integration
âDynamic bending designâ: Foldable and curled, adaptable to complex spatial layout (such as laser radar, medical endoscope)
âHigh-density wiringâ: HDI technology (blind vias, buried vias) supports multi-layer signal layer and power layer integration to meet complex circuit requirements.
âMulti-functional adaptationâ: The flexible area and the rigid area are freely combined, compatible with complex component installation and dynamic mechanical structure.
âProduction and design advantages
âSimplified assembly processâ: Reduce the use of cables and connectors and reduce the assembly error rate.
âDesign freedomâ: Supports three-dimensional wiring and flexibly matches different device forms (such as hearing aids and folding screen hinges.
Through material and process innovation, the rigid-flexible board has achieved breakthroughs in space, reliability, cost and performance, becoming a core solution for high-tech fields such as consumer electronics, automobiles, and medical care.
What Are the Advantages of Rigid Flex PCB?
Rigid-Flex PCB Design Guidelines
1. Preliminary planning and tool configuration
Definition of stack structure:
Use EDA tools such as Altium Designer to define rigid and flexible layers through the stack manager (shortcut D+K), and check the “Is Flex” property to divide the soft and hard areas.
Panel Division and Area Locking:
Use “dividing line” (shortcut D+S) to divide the board surface, fix the rigid area through the 3D lock function, and retain the dynamic bending characteristics of the flexible area.
2. Three-dimensional layout and structural design
3D modeling verification
Enable 3D view in EDA tools, simulate folding paths and bending radii, ensure that the direction of flexible region lines is perpendicular to the bending axis, reduce stress concentration.
It is forbidden to place vias in the dynamic bending area, and the vias should be kept away from the soft and hard combination area â„ 50mil (high reliability scenarios â„ 70mil).
Material matching and stacking
The flexible area selects rolled copper (with excellent ductility) as the conductive layer, with a thickness of 12-35ÎŒm; the cover film (Coverlay) uses PI material, with a thickness of 12.7-127ÎŒm.
The hard plate area is pressed with PP glue (semi-cured sheet) and the flexible plate, and the hollow layered design is used to reduce the bending stress.
3. Routing and through hole design rules
Circuit Optimization
The flexible region conductors use a teardrop transition, with the width maximized (â„4mil), evenly distributed to disperse stress.
Signal lines are preferred to be perpendicular to the bending direction, and multi-layer cross-wiring uses an ‘I-Beam’ structure to enhance fatigue resistance.
Transition Area Treatment
At the junction of rigid and flexible sections, the circuit transitions smoothly to avoid right angles or through-hole (PTH) design; the cover film must have a 0.5â1mm excess for overflow when opening windows.
Stainless steel stiffener strips or PI stiffener films are added on both sides of the bending area to enhance mechanical support.
4. Verification and Production Alignment
Simulation and Test Rules
Verify impedance continuity through TDR testing, with dynamic bending areas requiring more than 100,000 cycles of simulation.
Use tools such as Mentor Xpedition for lamination simulation to check the risk of glue overflow.
Production File Output
Provide layered Gerber files, marking the boundaries of soft and hard regions and the positions of stiffener. CAM engineers need to handle parameters for inner shrinkage due to glue overflow.
Laser cutting parameters for rigid board areas must be precisely controlled in depth to avoid damaging internal layers.
The design of flexible-hard combination boards should combine three-dimensional simulation, material properties, and process limitations, achieving high-density interconnection and reliability balance through layered lamination and dynamic bending rules.
Rigid Flex PCB Manufacturing Process
1. Material preparation and inner layer production
Cutting and drilling
Cutting: Cut the substrate (FR4, PI film, etc.) according to the design parameters, adjust the equipment parameters and clean the surface of the board.
Drilling: Use laser or mechanical drilling technology to make through holes (PTH) or blind holes. The hard board area needs to be cut with controlled depth to avoid damaging the inner layer circuit.
Inner layer circuit formation
Pressure dry film and exposure: Press dry film on the copper clad board, and define the circuit pattern through film alignment exposure.
Development and etching: Develop to remove the unexposed dry film, and the acid etching solution dissolves the unprotected copper layer to form a conductive circuit.
2. Rigid-flexible lamination
Flexible layer processing
Apply cover film: Apply polyimide (PI) cover film to the circuit layer in the flexible area (such as L3/L4), and check bubbles and fitting accuracy after pre-pressing and fixing. â
Stiffener and protectionâ: Stainless steel stiffener strips or PI reinforcement film are added on both sides of the bending area to improve mechanical strengthâ.
âMultilayer laminationâ
âLamination and laminationâ: The flexible board (FPC) and the rigid board (PCB) are alternately laminated through PP glue (semi-cured sheet), and high-temperature lamination is formed into a “sandwich” structure to eliminate the risk of delaminationâ.
âHollow designâ: The dynamic bending area adopts a hollow layering process to reduce stress concentrationâ.
3. âOuter layer processing and hole metallizationâ
Secondary drilling and hole processingâ
âLaser cuttingâ: The outer layer of the hard board area is exposed to the flexible area through laser uncovering (gong edge), and the cutting depth is controlled to avoid damaging the inner layer circuitâ.
âCopper deposition and copper platingâ: Chemical copper deposition in the hole is used to achieve conduction, and the outer layer is electroplated with a thickened copper layer (12â35ÎŒm) to improve the conductivity reliabilityâ.
Outer layer circuit productionâ
âGraphic transferâ: The outer copper clad laminate is exposed, developed, and etched to form surface circuits, and the teardrop-shaped pad design enhances the connection strengthâ.
4. âSurface treatment and moldingâ
âSolder mask and character printingâ
âSolder mask (green oil): Print photosensitive solder mask ink to cover non-welding areas and form an insulating protective layer after curingâ.
âSilk screen textâ: Mark component location, product model and other informationâ.
Surface metallizationâ
âElectronic nickel immersion gold (ENIG): Chemical nickel-gold plating in the pad area to prevent oxidation and improve welding performanceâ.
Molding and testingâ
âEdge and punchingâ: Cut the shape to remove excess waste and retain the functional areaâ.
âReliability testâ:
âElectrical testâ: Verify continuity and impedance continuityâ.
âBending testâ: Simulate dynamic bending for more than 100,000 times to detect the risk of breakage or delaminationâ.
5. Special process adaptation
High-frequency signal optimization: high-frequency boards (such as Rogers) are combined with blind and buried hole design to reduce signal attenuation.
Automotive grade requirements: pass vibration and high and low temperature cycle tests (-55â~125â), and add FR4 reinforcement to the hard board area.
The production of soft and hard boards requires precise control of material matching and process parameters (such as temperature and pressure), and through multi-layer lamination and dynamic bending optimization, it meets the lightweight and reliability requirements of high-density electronic equipment.
Flex Rigid PCB Manufacturer
EBest Circuit (Best Technology),aflex rigid PCB manufacturer, establish on June 28, 2006, is a Hong Kong registered company, whom focused on FR4 PCB, Flexible PCB, Flex Rigid PCBdesign, prototype and manufacturing and also provideâPCB assembly(PCBA) service.
BEST begin to As a printed circuit board (PCB) vendor in Asia, we are dedicated to be your best partner of advance, high-precision printed circuit boards, such as heavy copper boards, mixed layers, high TG, HDI, high frequency (Rogers, Taconic), impedance controlled board, Metal Core PCB (MCPCB) such as Aluminum PCB, Copper PCB, and so on.
What we provide is not only PCB & MCPCB manufacturing, but also including PCB duplicating, Engineering & process design, components management & sourcing solution, PCB in house assembly & full system integration, surface mounted technology (SMT).
All the PCB & MCPCB are strictly follow the operation procedures stipulated in ISO9001:2000 in respect to material purchasing, product manufacturing, testing, packing, marketing, etc. All the order placed with us is money-refund-guaranteed.
Most of our engineer and operators has more than ten years of experience in PCB industry, so we can produce special such as 20 OZ heavy copper board, 4 layer MCPCB, etc. At the same time, we purchased many advanced, art-of-state machines & devices for PCB manufacturing, checking, to improve the quality of our boards.
Currently our monthly productivity is 260,000 square feet (28,900 square meter), more than 100 different boards will be completed. We can also provide fast delivery service, and urgent boards can be shipped out within 24 hours!
More information welcome to contact us if you’re interested in us.(The email is at the beginning of this blog)
What Is the Difference Between Rigid Flex PCB and Flex PCB?
Differences in materials and structures
ââFlex PCB
Substrateâ: Single or double-layer PI or PET film
Single or multi-layer flexible circuit, without rigid support
Usually without stiffener
âRigid-flex PCB
Substrateâ: The rigid area uses FR4 or high-frequency plates, the flexible area uses PI film, and is bonded with PP adhesive (semi-cured sheet).
Mixed structure with 3 or more layers, including blind hole/buried hole design, interconnecting rigid and flexible areas
Stainless steel stiffener strips or PI reinforcement film need to be added in the bending area.
Differences in design and manufacturing processâ
âFlexible PCB Board
Graphic transferâ: Circuits are formed by dry film exposure and etching, without rigid support structureâ.
âSurface treatmentâ: Cover with PI protective film (Coverlay) to prevent oxidationâ.
Applicable processâ: Single-sided or double-sided circuits, low cost but weak environmental impact resistanceâ.
âRigid-flex PCB boardâ:
Lamination difficultiesâ: Precise control of the thickness matching of the rigid-flexible area is required to avoid delamination (such as hollow delamination process).
Hole processingâ: Vias are prohibited in the dynamic bending area, and a smooth circuit design is required in the rigid-flexible transition area.
Special processâ: Laser cutting of the rigid board area to retain the flexible area, copper plating to ensure conduction.
Comparison of performance and application scenariosâ
âFlexible board
Low mechanical strength, easily damaged by external forces.
High-frequency signals are easily attenuated (affected by bending).
Low cost (suitable for mass production)
Used in consumer electronics (headphones, smart watches).
Rigid-flexible board
High mechanical strength, rigid area provides support, flexible area resists bending fatigue
The rigid area can integrate high-speed signal layer, impedance control is more precise
High cost (complex process, low yield)
Used in high reliability areas (aerospace, automotive radar)
What Are the Applications of Rigid Flex PCB?
The versatility of rigid flex PCBs makes them essential in various industries:
Consumer Electronics-Used in smartphones, foldable devices, and wearables.
Medical Devices-Applied in implants, imaging systems, and diagnostic tools.
Automotive Electronics-Integrated into advanced driver-assistance systems (ADAS) and infotainment.
Aerospace & Defense-Utilized in satellite systems, avionics, and military-grade equipment.
Industrial Equipment-Found in robotics, control systems, and automation devices.
A well-designed rigid flex PCB enhances performance, reliability, and space efficiency in modern electronic applications. Selecting the right manufacturer ensures high-quality production and long-term durability.
âConclusion
As an integrated carrier of rigid-flexible synergy, the rigid-flexible board is driving electronic devices to iterate towards higher integration and stronger reliability with its unique structural design and performance advantages. In the industrial and medical fields, the precise design of the rigid-flexible transition zone (such as the hollow layering process) has achieved stable signal transmission and vibration resistance in complex environments for equipment such as endoscopes and vehicle-mounted radars; in the consumer electronics field, the rigid-flexible board has broken through the space limitations of traditional rigid boards with its high-density wiring and dynamic bending characteristics (â„100,000 cycle life) in folding screen hinges and mobile phone camera modules.
From the perspective of technological evolution, the material innovation (such as the combination of high-frequency FR4 and ultra-thin PI film) and process upgrade (laser cutting precision control) of the rigid-flexible board will continue to promote its application in high-frequency and high-speed scenarios, such as 5G millimeter wave communications and autonomous driving sensors. At the same time, it significantly improves the reliability of the system-level package (SiP) by reducing connector solder joints and optimizing the rigid-flexible transition zone line design (teardrop-shaped wires and reinforcement strips).
In the future, with the popularization of wearable devices and IoT terminals, the soft-hard combination board will be more deeply integrated into the design philosophy of “rigid-flexible symbiosis” – the rigid area carries the computing core, and the flexible area achieves form adaptation. Ultimately, in the “soft-hard game” of the electronics industry, it will become the ultimate solution to balance function, cost and reliability.
