A 6-Layer Rigid-Flex PCB is an advanced printed circuit board technology that integrally combines rigid board stability with flexible circuit dynamic bending capability. This product from UGPCB utilizes a premium adhesive-free lamination process, resulting in a final board thickness of 1.50mm, dimensions of 120x80mm, and features an ENIG (Electroless Nickel Immersion Gold, 3μ”) surface finish. It represents a cutting-edge solution for High-Density Interconnect (HDI) and three-dimensional electronic packaging, solving complex spatial and mechanical challenges in modern electronics.
Scientific Product Classification
According to IPC-6013D standards and product construction, this board is accurately classified as:
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By Construction: Rigid-Flex Printed Board (Type 4)
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By Layer Count: Six-Layer Board (combining rigid and flexible layers)
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By Technology: Adhesive-less (Adhesive-Free) Flexible Material Rigid-Flex PCB
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By Application: High-Reliability, High-Flex-Cycle Industrial & Medical Grade PCB
Core Structure & Materials
The exceptional performance is rooted in its sophisticated layered structure and top-tier materials:
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Core Flex Material: Features Shengyi’s 18/50/18 μm adhesive-free double-sided substrate. “18/50/18” denotes a structure of 1 oz (18μm) copper / 50μm Polyimide (PI) dielectric / 1 oz (18μm) copper. The adhesive-free construction bonds copper to PI chemically, eliminating adhesive layers, which significantly enhances thermal resistance, chemical resistance, and flex circuit reliability.
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Rigid Section Material: Uses 25/25 prepreg for lamination in rigid areas, providing robust mechanical support.
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Surface Finish: The entire board employs ENIG (3μ”). This 3-microinch gold layer offers excellent flatness, oxidation resistance, and solderability for PCB pads, making it ideal for assembling fine-pitch components like BGAs.
Design Key Considerations & Working Principle
Rigid-flex PCB design is critical for success. The board operates by routing electrical signals through flexible polyimide areas for dynamic movement, while using rigid FR-4 sections for component mounting and structural support.
Essential Design Guidelines Include:
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Bend Area Definition: Clearly distinguish between static (one-time install) and dynamic (repeated operation) bend zones. Design the bend radius accordingly. A dynamic bend radius should be at least 10x the flex area thickness (for this board, ≥15mm is recommended).
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Transition Zone Reinforcement: The rigid-to-flex junction is a stress point. Use teardrop pads, curved traces, and stiffeners to prevent delamination and cracking.
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Impedance Control: For high-speed signals (e.g., differential pairs) crossing flex areas, precisely calculate trace width and dielectric thickness to maintain consistent characteristic impedance (e.g., 50Ω single-ended, 100Ω differential).
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Flex Routing Rules: In flexible areas, route conductors perpendicular to the bend axis. Use curved or staggered traces to distribute stress evenly.
Performance Characteristics & Advantages
Compared to traditional adhesive-based rigid-flex PCBs or rigid-board+connector assemblies, this UGPCB product offers distinct PCB advantages:
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Enhanced Reliability: The adhesive-free structure prevents delamination risks from adhesive aging or moisture absorption, increasing flex life by up to 10x and withstands over 100,000 dynamic bend cycles.
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Superior Electrical Performance: Uniform PI dielectric with stable dielectric constant (Dk~3.4) ensures signal integrity for high-frequency applications and reduces loss.
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Lightweight & High-Density: Eliminates connectors, cables, and solder joints, enabling 3D assembly. Can reduce system weight by up to 60% and save over 50% space.
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Excellent Durability: Resists extreme temperatures (-55°C to +125°C) and chemical exposure, suitable for harsh environments.
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Simplified Assembly: A single integrated component reduces assembly steps, potential failure points, and improves final product yield.
Production Process Overview
UGPCB’s rigid-flex PCB manufacturing combines advanced rigid PCB fabrication and flexible circuit production processes:
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Inner Layer Fabrication: Separate etching of rigid FR-4 and flexible PI core layers.
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Lamination: Precise alignment and high-temperature/pressure bonding of rigid layers, adhesive-free flex cores, and prepreg into a monolithic structure—a critical step in multilayer PCB processing.
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Drilling & Plating: Mechanical and laser drilling (if needed) followed by copper deposition and plating to create Plated Through Holes (PTH) for interlayer connection.
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Outer Layer Imaging & Etching: Pattern formation for outer layer circuits.
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Surface Finish Application: ENIG chemical deposition.
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Coverlay & Profiling: Application of protective film (coverlay) on flex areas. Precise routing and laser cutting define the board outline and flex section openings.
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Electrical Test & Final Inspection: 100% flying probe or fixture testing for electrical continuity, followed by rigorous visual and dimensional inspection.
Primary Applications & Use Cases
This 6-layer high-reliability PCB is the ideal choice for demanding applications:
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Aerospace & Defense: Satellite deployment mechanisms, guidance systems, avionics sensors requiring utmost reliability and weight reduction.
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Advanced Medical Devices: Endoscopes, ultrasound probes, wearable monitors needing complex motion and signal transmission in minimal space.
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Industrial Robotics: Robot joints, internal robotic arm assemblies for seamless power/signal transmission across moving parts.
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Precision Instruments & Consumer Electronics: Advanced camera modules, foldable display hinges, drone gimbals pursuing slimness and durability.
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Automotive Electronics: Automated parking sensors, foldable dash displays, in-vehicle camera modules resistant to vibration and thermal cycling.
Ready to integrate superior reliability into your design? Contact UGPCB engineers today for a free design review and quote on your custom 6-Layer Rigid-Flex PCB solution.