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Flexible Printed Circuits (FPCs) offer unique advantages in thinness, bendability, and fatigue resistance, making them widely used in consumer electronics, medical devices, automotive, and aerospace applications. Below are the key industry terms and their latest definitions:
1.Materials & Substrates
Wrought Foil (Rolled Annealed Copper, RA Foil)
Mechanically rolled and annealed copper foil with superior ductility and crack resistance, ideal for dynamic FPCs requiring repeated bending. Outperforms Electro-Deposited (ED) foil in high-flex applications.
2. Coverlay / Covercoat
A composite film of polyimide (PI) and thermosetting adhesive, laminated onto FPC surfaces to protect circuits, resist soldering, prevent corrosion, and enhance bending reliability. A modern alternative to traditional solder mask.
3. Polyimide (PI)
The industry-standard substrate for FPCs, offering exceptional heat resistance, electrical insulation, and dimensional stability. Essential for high-end FPCs and rigid-flex boards.
4. Polyester Film (PET)
Used as a protective layer or Coverlay base material in cost-sensitive static FPCs. Features high transparency but lower heat resistance compared to PI.
5. FPC Types & Applications
Dynamic Flex FPC
Designed for continuous or repetitive bending (e.g., foldable screens, wearables). Requires high fatigue resistance, typically using RA copper foil.
6. Static Flex FPC
Used in fixed installations with minimal movement (e.g., camera modules, display connectors). Only requires one-time bending during assembly.
7.Membrane Switch
A tactile switch system made of PET/PC films with screen-printed silver paste circuits, combined with spacer layers and panels. Common in human-machine interfaces.
8. Rigid-Flex PCB
Hybrid boards integrating rigid and flexible sections, offering both structural stability and bendability. Widely used in compact, high-performance electronics.
9.Manufacturing & Design
Access Hole (Window Opening)
Openings in Coverlay to expose pads or test points for SMT assembly or electrical testing.
10.Anchoring Spurs
Serrated extensions around pads to improve adhesion to the substrate, preventing detachment under stress.
11.Bendability
A material’s ability to withstand repeated bending without failure. Key metrics include minimum bend radius and cycle life.
12.Laser Via / Microvia
Microscopic holes (≤100µm) drilled by laser for high-density interconnects (HDI) in multilayer FPCs.
13.Steel Rule Die
A cutting die with embedded blades for precision FPC outline punching, similar to paper die-cutting.
14.Reel-to-Reel (R2R)
Continuous roll-based manufacturing for FPCs, TAB, or other flexible components, improving efficiency and reducing costs.
15.Surface Treatments & Adhesives
ENIG / ENEPIG
ENIG (Electroless Nickel Immersion Gold): Standard finish for solderability and oxidation resistance.
ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold): Enhanced version with better wire bonding performance.
16.Acrylic Adhesive
A flexible, high-bond-strength adhesive for laminating copper to PI or attaching Coverlay.
17.Adhesive (Bonding Layer)
Used in multilayer FPCs or rigid-flex boards, including thermoset, thermoplastic, and UV-curable types.
18.Stiffener
Reinforcement materials (PI, FR4, or metal) added to localized areas (e.g., connectors) for mechanical support without electrical function.
This glossary covers critical FPC design, material, and process terminology, serving as a practical reference for R&D, engineering, procurement, and QA professionals.
*(Note: Industry trends such as 3D-printed rigid-flex, self-healing FPCs, and biodegradable substrates are emerging but not yet standardized.)*
