I. Pricing System (Professional Dimension Breakdown)

Material Cost (60%-70% of Total Price)

• Base Film:
  • Polyimide (PI) base film: ~80-150 RMB yuan/㎡ (significant variation by temperature resistance; e.g., standard PI withstands -55℃~125℃, while high-end modified PI resists over 200℃ at >200 RMB yuan/㎡).
  • Polyester (PET) base film: Only 30-50 RMB yuan/㎡, with a 3-5x cost gap compared to PI.
• Conductor Layer:
  • Rolled Annealed Copper (RACu): ~120-180 RMB yuan/kg (high flexibility for dynamic bending), 50%-100% more expensive than Electrodeposited Copper (EDCu: 60-90 RMB yuan/kg).
  • Cost increases by 3%-5% per 1μm increase in copper foil thickness (e.g., 18μm RACu costs 40% more than 9μm RACu).
• Auxiliary Materials:
  • Adhesiveless structure (direct thermal compression bonding) costs 20%-30% more than adhesive-based structure (acrylate adhesive).
  • Electroless Nickel Immersion Gold (ENIG) surface finish: ~1.2-1.8 RMB yuan/square decimeter, 3-4x higher than tin plating (0.3-0.5 RMB yuan/square decimeter).

Process Complexity Premium (20%-30% of Total Price)

• Layer Count:
  • Single-layer FPCB: Benchmark price ~50-80 RMB yuan/㎡.
  • Double-layer FPCB (with vias): 50%-80% premium.
  • 4-layer FPCB (with blind/buried vias): 150%-200% premium.
  • Multi-layer FPCB (≥10 layers): Over 500% premium (interlayer alignment accuracy ±3μm; each 1% yield reduction increases cost by 2%-3%).
• Wiring Precision:
  • Reducing line width/line spacing from 50μm/50μm to 10μm/10μm adds an 80%-120% premium (requires LDI laser direct imaging with ≥5000dpi resolution and ≤3μm etching undercut).
• Special Processes:
  • Rigid-Flex PCB (FR-4 rigid area lamination): 40%-60% premium over same-layer pure FPCB.
  • Dynamic folding FPCB (≥1 million bending cycles): Requires RACu + adhesiveless structure, with over 100% premium.

Production Scale Impact

• Small-batch customization (≤1000 pieces): Unit price is 2-3x mass production price (includes mold fees: 500-2000 RMB yuan/set for laser cutting, and trial production losses).

• Mass production (≥100,000 pieces): Unit price drops to 40%-60% of small-batch price via optimized panel layout (utilization rate >85%) and automated production lines (AOI inspection replacing manual labor).
  

II. Manufacturing Process (Aligned with IPC-6012F Flexible Circuit Specifications)

1. Base Film Pretreatment

• Process Goal: Enhance adhesion between base film and conductor layer.
• Key Steps:
  • PI base film: Plasma treatment (300-500W power, 10-30s duration, surface tension ≥40mN/m).
  • PET base film: Corona treatment (15-25kV voltage to avoid high-temperature damage).
• Quality Requirements: No oil stains/scratches on the surface; thickness tolerance ±5% (e.g., ≤1.25μm for 25μm PI).

2. Conductor Layer Preparation (Etching Process)

• Main Processes:
  • Conventional: "Copper-clad base film → Photolithography → Etching".
  • Precision fine-line: "Sputter deposition → Electroplating thickening".
• Key Parameters:
  • Photolithography: LDI laser direct imaging (alignment accuracy ±2μm, line width uniformity ≤3μm); wet film thickness 10-20μm (ensuring post-etch line edge roughness Ra ≤1.5μm).
  • Etching: Acidic copper chloride etchant (Cu²+ concentration 180-220g/L, temperature 45-55℃), etching rate 2-3μm/min, undercut ratio ≤1:1 (≤10μm undercut for 10μm line width).
• Quality Requirements: No open circuits/residual copper; adhesion ≥0.5N/mm (per IPC-TM-650 2.4.9 test standard).

3. Interlayer Interconnection (Lamination & Via Processes)

• Multi-layer Lamination:
  • Vacuum autoclave (180-220℃, 2-4MPa pressure, 30-60min holding time); interlayer alignment accuracy ±3μm (CCD alignment system).
  • Adhesiveless FPCB: Controlled heating curve (5-10℃/min heating rate to avoid bubbles).
• Via Processing:
  • Drilling: Laser drilling (50-150μm hole diameter, ±5μm position accuracy); mechanical drilling (≥200μm hole diameter for thick base films).
  • Metallization: Chemical copper deposition (0.5-1μm Cu layer) → Electroplating (hole wall copper thickness ≥15μm, meeting IPC 2221 current-carrying requirements).
• Quality Requirements: Via conduction resistance ≤50mΩ; no hole breakage/voids (≥99.5% pass rate via X-ray inspection).

4. Surface Finish

• ENIG: Nickel layer 3-5μm, gold layer 0.05-0.15μm (thin gold for soldering, thick gold ≥0.5μm for connectors); no corrosion after 48h salt spray test (5% NaCl).
• Tin Plating: Tin layer 5-15μm; ≥95% wetting area in solderability test (235℃ solder, 2-3s immersion).
• OSP (Organic Solderability Preservative): Film thickness 0.2-0.5μm; 6-month shelf life (room temperature dry environment).

5. Cover Layer Lamination

• Process: Thermal compression bonding of cover film (PI/PET base + adhesive) to substrate (120-160℃, 1-2MPa pressure, 20-30s); opening position accuracy ±10μm (matching pads).
• Quality Requirements: No bubbles/lifting; adhesion ≥0.3N/mm; no cracking after 1000h at 125℃.

6. Forming & Inspection

• Forming: Laser cutting (±5μm accuracy for irregular shapes); die cutting (±20μm accuracy for mass production); burr-free edges (Ra ≤5μm).
• Inspection:
  • Electrical Testing: Flying probe test (100% coverage, conduction resistance ≤100mΩ, insulation resistance ≥10¹²Ω).
  • Reliability Testing:
    • Bending test (dynamic: 180° folding, 10 cycles/min, ≥1 million cycles; static: 0.5mm bending radius, 24h no open circuit).
    • Thermal cycle test (-55℃~125℃, 100 cycles) with no performance degradation.

III. Core Parameters (Per IPC-6012F & Industry Technical Specifications)

1. Base Film Parameters

• Temperature Resistance: PI (short-term 260℃/10s, long-term 125℃); PET (short-term 150℃/10s, long-term 80℃).
• Mechanical Properties: Tensile strength (PI ≥150MPa, PET ≥50MPa); elongation at break (PI ≥40%, PET ≥100%); flexural modulus (PI ≥2.5GPa for dynamic scenarios).
• Electrical Properties: Dielectric constant (PI≈3.5, PET≈3.2 at 1MHz); dielectric loss tangent (PI ≤0.005, PET ≤0.01 at 1MHz); breakdown voltage ≥20kV/mm.

2. Conductor Layer Parameters

• Copper Foil Type:
  • EDCu: Coarse grain, suitable for static scenarios; tensile strength ≥200MPa.
  • RACu: Fine grain, suitable for dynamic scenarios; tensile strength ≥300MPa, elongation ≥15%.
• Thickness & Current-Carrying Capacity (per IPC 2221: ≤30A/mm² at 25℃):
  • 18μm copper foil: ≤3A current for 1mm width.
  • 35μm copper foil: ≤5A current for 1mm width.
  • 70μm copper foil: ≤8A current for 1mm width.
• Surface Roughness: Ra ≤1.0μm (reduces signal loss for high-frequency scenarios ≥10GHz).

3. Wiring Precision Parameters

• Line Width/Line Spacing:
  • Standard FPCB: 20μm/20μm (tolerance ±10%).
  • Precision FPCB: 10μm/10μm (tolerance ±5%).
  • High-end FPCB: 5μm/5μm (tolerance ±3%).
• Feature Sizes: Minimum pad diameter ≥50μm (for 01005 components); via diameter (laser drilling ≥50μm, mechanical drilling ≥200μm); pad diameter ≥ via diameter + 100μm (to avoid hole breakage).

4. Reliability Parameters

• Bending Life: Dynamic bending (0.5mm radius, 180° folding) ≥1 million cycles (RACu + adhesiveless structure); static bending (1mm radius, fixed deformation) ≥1000h no open circuit.
• Environmental Adaptability: Insulation resistance ≥10¹¹Ω after 100 thermal cycles (-55℃/30min → 125℃/30min); conduction resistance change rate ≤10% after 1000h damp heat test (85℃/85% RH).
• Chemical Resistance: No corrosion or electrical performance degradation after 24h immersion in isopropyl alcohol/ethanol.