What Type of PCB to Choose for Different Product Fields?

November 7, 2025

This article systematically outlines the key points for PCB material selection, process design, performance indicators, and cost control across six typical application scenarios, supplemented with a pitfall guide, aiming to provide engineers with a one-stop practical reference.

I. Consumer Electronics: Balancing Thinness/Lightness and High Integration

Core Needs: Miniaturization, low power consumption, cost sensitivity.
Typical Applications: Mobile phones, laptops, TWS earphones, smartwatches.

1. Material Selection

Substrates:
FR-4 (Tg 130°C): Mainstream choice, low cost (~¥150/m²), supports 4-6 layers, suitable for ordinary signal transmission (e.g., charging modules, key circuits).
High-Frequency Modified FR-4 (e.g., Shengyi S1141H): Dk=4.2, cost ~40% lower than Rogers, suitable for 1-6GHz signals (e.g., Wi-Fi 6 modules).
Polyimide (PI): Used for Flexible PCBs (FPC), thickness 0.025-0.1mm, withstands over 100,000 bends, adaptable for folding screen hinges.

Copper Foil:
1oz (35μm): Balances signal transmission and cost, suitable for most consumer electronics.
Ultra-thin Copper Foil (9-12μm): Reduces thickness, used in ultra-thin laptops (e.g., MacBook Air motherboard thickness 1.5mm).

2. Process Selection

HDI Technology: 1st/2nd order buried vias; line width/spacing 30/30μm, supports multi-chip integration (e.g., mobile phone motherboards integrating CPU, baseband).
Laser Drilling: Minimum aperture 0.1mm, increases wiring density (e.g., TWS earphone charging case PCB area reduced by 30%).

Surface Tratement:

HASL (Lead-Free): Low cost, good solderability, suitable for non-high-frequency areas (e.g., power interfaces).
ENIG: High surface flatness (Ra < 0.1μm), suitable for high-frequency signals (e.g., 5G RF antennas).

3. Performance Indicators

Thickness: 0.4-1.6mm, mobile phone motherboards typically use 0.8mm thin board + buried via design.
Impedance Control: Differential pairs (e.g., USB4.0) impedance 100Ω±10%, single-ended lines (e.g., GPIO) 50Ω±10%.
Thermal Design: Embedded copper blocks (thickness 0.5mm) or thermal conductive adhesive bonding, reduces SoC junction temperature (e.g., iPhone 15 Pro motherboard reduces A17 chip temperature by 10°C via embedded copper block).

4. Certifications and Reliability

Certifications: UL 94V-0 flame retardant certification, RoHS environmental certification.
Testing: High/low temperature cycling (-20°C~70°C, 500 cycles), drop test (1.2m height, 1 time on each of 6 sides).

5. Cost and Mass Production Advice

Cost Range: Single-layer board ¥50-100/m², 6-layer HDI board ¥800-1200/m².
Mass Production Optimization: Use panelization design (e.g., 8-up panel), reduces material waste (utilization rate increased to 90%).

II. Automotive Electronics: High Reliability and Extreme Environment Adaptation

Core Needs: Wide-temperature tolerance, vibration resistance, functional safety.
Typical Applications: BMS, Autonomous Driving Domain Controllers, Vehicle Radar.

1. Material Selection

Substrates:
High Tg FR-4 (Tg≥170°C): Suitable for engine compartments (-40°C~150°C), flexural strength 30% higher than ordinary FR-4.
Aluminum Substrate: Thermal conductivity 2.0 W/m·K, used for motor controllers, improves heat dissipation efficiency by 50%.
Polyimide (PI): Used in high-temperature areas (e.g., near turbochargers), short-term tolerance 200°C.
Copper Foil: 3-6oz (105-210μm): High current transmission (50-200A), reduces line resistance (e.g., BMS busbar design).

2. Process Selection

Heavy Copper Plating: Hole wall copper thickness ≥25μm, improves vibration resistance (<3% resistance change after 1 million vibrations).
Composite Surface Treatment: Electroless Nickel Immersion Gold (ENIG) + Immersion Tin, reduces solder joint corrosion area by 80% after salt spray test (1000 hours).
Conformal Coating: Thickness 25-50μm, resistant to oil, salt spray, complies with ISO 16750 standard.

3. Performance Indicators

Temperature Range: -40°C~150°C, supports 1000 temperature cycles (-40°C~125°C).
Vibration Resistance: 20G acceleration, 10-2000Hz random vibration, requires continuous inspection of solder joint void rate <5%.
Functional Safety: Complies with ISO 26262 ASIL B-D levels, key signal dual-path redundancy design (e.g., sensor interfaces in autonomous driving domain controllers).

4. Certifications and Reliability

Certifications: IATF 16949 Quality Management System, AEC-Q100 (passive components), AEC-Q200 (active components).
Testing:
High Voltage Test: 800V platform requires CAF test (1000V DC, no conductive anodic filament).
EMC Test: Radiated interference ≤30dBμV/m (30-1000MHz), complies with CISPR 25 standard.

5. Cost and Mass Production Advice

Cost Range: Single-layer board ¥300-500/m², 16-layer HDI board ¥3000-5000/m².
Mass Production Optimization: Adopt modular design (e.g., separate BMS cell detection board and main control board), reduces maintenance costs (failure rate decreased by 50%).

III. Medical Devices: High Precision and Biocompatibility

Core Needs: Zero tolerance, sterilization resistance, biosafety.
Typical Applications: CT Scanners, Pacemakers, Wearable Monitors.

1. Material Selection

Substrates:
Halogen-Free FR-4 (Cl/Br < 900ppm): e.g., Isola FR406, UL 94 V-0 certified, avoids drug solution contamination.
Polyimide (PI): For implantable devices, biocompatibility test cell survival rate ≥98%, resistant to EO sterilization (50°C, 12 hours). Surface Treatment:
ENIG (Au≥0.1μm): Excellent solderability, suitable for precision soldering (e.g., pacemaker electrode interfaces).
Medical Grade Conformal Coating: e.g., Dow Corning TC-5288, withstands 1000 alcohol wipes, water absorption <0.01%.

2. Process Selection

Laser Drilling: Minimum aperture 0.15mm, supports high-density wiring (e.g., CT detector pixel arrays).
Aseptic Packaging: Titanium alloy shell + laser welding, hermeticity test leakage rate < 1×10^-5 mbar·L/s.

3. Performance Indicators

Signal Accuracy: ADC sampling error ≤±0.5LSB, noise control <15μV (e.g., ultrasound echo signal processing).
Insulation Performance: High-voltage areas (e.g., MRI gradient coils) spacing ≥0.5mm, insulation resistance >10¹²Ω.

4. Certifications and Reliability

Certifications: ISO 13485 Quality Management System, FDA 510(k) (non-implantable), CE MDR (implantable).
Testing:
Biocompatibility: Full set of ISO 10993 tests (cytotoxicity, sensitization), implantable devices require genetic toxicity testing.
Sterilization Resistance: After ethylene oxide sterilization, Tg value decrease <10%, interlayer bonding strength maintained ≥1.2N/mm.

5. Cost and Mass Production Advice

Cost Range: Single-layer board ¥800-1500/m², 8-layer board ¥5000-8000/m².
Mass Production Optimization: Establish material traceability files; select suppliers with Class 1000 cleanrooms, dust particle control ≤0.5μm.

IV. Industrial Control: Long-Term Stability and Anti-Interference

Core Needs: Vibration resistance, EMI resistance, wide-temperature operation.
Typical Applications: PLC Controllers, Industrial Robots, Sensor Nodes.

1. Material Selection

Substrates:
High Tg FR-4 (Tg≥170°C): Suitable for high-temperature environments (-40°C~125°C), flexural strength 20% higher than ordinary FR-4.
Ceramic Substrate: Thermal conductivity 25 W/m·K, used for high-power modules (e.g., frequency converter IGBT heat dissipation).
Copper Foil: 2oz (70μm): High current transmission (20-50A), reduces trace temperature rise (e.g., motor drive circuits).

2. Process Selection

Heavy Copper Plating: Hole wall copper thickness ≥25μm, improves vibration resistance by 50% (<5% resistance change after 1 million vibrations).
3W Spacing Rule: Critical signal line spacing ≥3x line width, reduces crosstalk (e.g., Industrial Ethernet differential pairs).

3. Performance Indicators

Temperature Range: -40°C~125°C, supports 1000 hours 85/85 test (85°C/85%RH).
Vibration Resistance: 10-2000Hz random vibration, acceleration 20G, component fixation uses red glue (coverage area ≥80%).

4. Certifications and Reliability

Certifications: IEC 61131-2 (Industrial control standard), UL 94 V-0 flame retardant certification.
Testing:
Salt Spray Test: 5% NaCl solution, 35°C, 1000 hours, solder joint corrosion area <5%.
EMC Test: Conducted interference ≤40dBμV (150kHz-30MHz), complies with CISPR 32 standard.

5. Cost and Mass Production Advice

Cost Range: Single-layer board ¥200-350/m², 4-layer board ¥1000-1500/m².
Mass Production Optimization: Adopt modular design (e.g., separate PLC I/O modules), reduces maintenance cost by 40%. Select certified suppliers, stable lead time of 10-15 days.

V. High-Frequency Communication: The Ultimate Pursuit of Signal Integrity

Core Needs: Low loss, stable impedance, high-frequency response.
Typical Applications: 5G Base Stations, Satellite Communication, Millimeter-Wave Radar.

1. Material Selection

Substrates:
Rogers RO4350B: Dk=3.48±0.05, Df=0.0037@10GHz, suitable for signals above 24GHz (e.g., vehicle radar).
Shengyi S1000-2M: Dk=3.0±0.05, Df=0.0027@10GHz, cost ~50% lower than Rogers, suitable for 5G base station AAU modules.
Copper Foil: VLP Copper Foil (Surface Roughness Ra < 0.5μm): Reduces high-frequency loss (e.g., 5G RF line loss reduced by 0.5dB/10cm).

2. Process Selection

mSAP: Line width/spacing 3.5/3.5mil (90/90μm), supports high-density high-frequency routing (e.g., 64T64R mmWave radar).
Differential Pair Design: Impedance 100±5%, line width/spacing 4.5/5.5mil (115/140μm), for PCIe 5.0 interfaces.

3. Performance Indicators

Signal Loss: Insertion loss ≤0.3dB/cm @28GHz, return loss ≤-15dB.
Impedance Stability: Impedance variation ±3Ω over -40°C~125°C range, complies with IST test standard.

4. Certifications and Reliability

Certifications: IPC-6013 Class 3 (High Reliability), MIL-PRF-55110G (Military Standard).
Testing:
S-Parameter Test: S21 ≥ -10dB @20GHz, eye diagram extinction ratio ≥6dB (e.g., 5G NR signal).
Thermal Shock Test: -55°C~260°C, 1000 cycles, interlayer bonding strength ≥1.5N/mm.

5. Cost and Mass Production Advice

Cost Range: Single-layer board ¥1000-2000/m², 8-layer board ¥8000-12000/m².
Mass Production Optimization: Use step lamination process, reduces material stress (layer misalignment ≤50μm). Select suppliers with high-frequency testing capabilities, provide complete S-parameter report.

VI. Rigid-Flex Boards: Flexible Solutions for Dynamic Scenarios

Core Needs: Bend resistance, 3D topology, space optimization.
Typical Applications: Folding Screen Hinges, Industrial Robot Joints, Medical Endoscopes.

1. Material Selection

Flexible Layers:
Polyimide (PI): Thickness 0.025-0.1mm, withstands over 100,000 bends (radius≥1mm), adaptable for folding screens.
Liquid Crystal Polymer (LCP): Dk=2.95±0.02, used for high-frequency flexible cables (e.g., 5G phone antennas).
Rigid Layers: FR-4 (Tg≥150°C): Combined with flexible layers, supports multi-layer rigid-flex stacking (e.g., industrial robot control boards).

2. Process Selection

Adhesiveless Lamination (RCC): Reduces dielectric layer thickness (total thickness ≤0.2mm), impedance control accuracy ±5%, suitable for 77GHz radar.
Stress Relief Slots: Laser-cut V-shaped slots in bend areas (depth ≤50% board thickness), increases lifespan by 30%.

3. Performance Indicators

Bend Cycle Life: Over 100,000 cycles (IPC-6013D standard, 90° bend angle, 1mm radius).
Impedance Stability: Differential impedance variation ±5% after bending, suitable for high-speed signals (e.g., HDMI 2.1).

4. Certifications and Reliability

Certifications: IPC-2223C (Rigid-Flex Design Standard), UL 94 V-0 flame retardant certification.
Testing:
Dynamic Flex Test: 1 cycle/sec, <5% resistance change after 100,000 cycles, no insulation failure.
IP67 Waterproof: Coated with magnetic flux coating, no corrosion after 1000-hour salt spray test.

5. Cost and Mass Production Advice

Cost Range: 4-layer rigid-flex board ¥3000-5000/m², 8-layer rigid-flex board ¥8000-12000/m².
Mass Production Optimization: Use pre-bending process (e.g., 30° pre-bend for folding screen hinge) to reduce stress concentration in use.
Select suppliers with rigid-flex mass production experience, yield can reach over 85%.

VII. Pitfall Guide: Key Design Taboos and Selection Suggestions

1.[Consumer Electronics]: Avoid excessive layer count; strictly evaluate cost-effectiveness for HDI beyond 6 layers (e.g., 6-layer HDI often suffices for phone motherboards).
2.[Automotive Electronics]: Prohibit standard FR-4 in high-temperature areas (e.g., engine bay); must use higher temperature resistant PI substrate (Tg≥260°C) to ensure long-term reliability.
3.[Medical Devices]: Implantable PCBs must pass ISO 10993-12 (extractables testing) and strictly avoid halogen-containing materials to prevent biological toxicity risks.
4.[Industrial Control]: Avoid upright electrolytic capacitors in vibrating environments; prioritize horizontal installation reinforced with red glue to enhance mechanical stability.
5.[High-Frequency Communication]: For mmWave signals (>24GHz), use Rogers RO4350B or equivalent high-end materials; modified FR-4 cannot meet the extremely low loss requirements.
6.[Rigid-Flex Boards]: Strictly avoid placing vias in bend areas; prioritize blind vias or Laser Direct Imaging (LDI) processes to eliminate stress concentration points and ensure bend cycle life.