I. Core Components of FPCB Lamination (Universal Base Layers)

II. Key Types of FPCB Laminated Structures (Classified by Layer Count)

1. Single-Sided FPCB — Simplest, Low-Cost Structure

• Key Parameters: Line width/line spacing ≥ 100μm/100μm; total thickness 0.1-0.2mm
• Application Scenarios: Simple wiring, low-cost requirements (e.g., remote control key circuits, small sensor connecting wires, simple signal transmission for home appliances)
• Advantages: Simple process, lowest cost, best flexibility; Disadvantages: Single-sided wiring only, limited functionality, unable to achieve complex interconnection

2. Double-Sided FPCB — Double-Sided Wiring, Balancing Functionality and Flexibility

• Core Features: Interconnection between upper and lower conductor layers via "vias" (through vias, blind vias); line width/line spacing ≥ 50μm/50μm; total thickness 0.15-0.3mm
• Application Scenarios: Double-sided wiring, medium functional density (e.g., mobile phone screen connecting cables, smartwatch motherboards, small camera modules)

• Advantages: More functional than single-sided FPCB, can integrate more components, maintains excellent flexibility; Disadvantages: Higher cost than single-sided FPCB, increased complexity due to via process
  

3. Multi-Layer FPCB — Core Structure for High-Density, Complex Functions

• Key Components: Inner layer is "core board" (base film + conductor layer); interlayer interconnection via "buried vias" and "blind vias"; partial high-end products adopt "adhesiveless core boards" to reduce thickness
• Key Parameters: 4-20 layers; line width/line spacing ≥ 10μm/10μm (precision process up to 5μm/5μm); total thickness 0.2-0.8mm
• Application Scenarios: High-density wiring, complex function integration (e.g., hinge circuits for foldable phones, BMS (Battery Management System) for new energy vehicles, interconnection for aerospace equipment)
• Advantages: High integration, can replace multiple single/double-sided FPCBs, reducing assembly complexity; Disadvantages: Complex process (interlayer alignment accuracy ±5μm), high cost, slightly lower flexibility than single/double-sided FPCBs

III. Special Laminated Structure: Rigid-Flex PCB

• Structural Principle: On the basis of multi-layer FPCB, rigid substrates (e.g., FR-4) are embedded in local areas to form an integrated design of "flexible areas + rigid areas"
• Typical Lamination: Rigid Area (FR-4 base + thick copper conductor layer) → Transition Layer (flexible base + adhesive layer) → Flexible Area (PI base + thin copper conductor layer)
• Core Advantages: Rigid areas for component mounting and load-bearing fixation (e.g., soldering chips, connectors); flexible areas for spatial bending and dynamic connection (e.g., adapting to complex internal structures of equipment)
• Application Scenarios: Balancing stability and flexibility (e.g., mobile phone camera modules, UAV flight control boards, implantable circuits for medical devices)

IV. Core Principles of FPCB Lamination Design

1. Flexibility Priority: All materials (base film, adhesive) must be flexible to avoid rigid materials affecting overall deformability
2. Interlayer Consistency: Uniform thickness of each layer and even adhesive coating to prevent interlayer bubbles and peeling (which affect bending life)
3. Wiring Adaptation: Use "rolled annealed copper foil" in dynamically bent areas (e.g., foldable screen hinges) to reduce copper foil fracture risk; use "electrodeposited copper foil" in static areas to lower costs
4. Reliability Assurance: Cover layers must fully wrap conductor layers (except pads) to prevent oxidation; vias require metallization to enhance interconnection stability

V. Summary: Selection Logic for Different Laminated Structures