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PI vs. PET Substrates in FPC Manufacturing: Advanced Material Analysis & Application Optimization
- Mar 17,2025
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At Shenzhen Huaruixin Electronics Co., Ltd., our decades of engineering expertise in advanced circuit solutions drives innovation in Flexible Printed Circuit (FPC) design and manufacturing. This technical guide provides an in-depth comparison of Polyimide (PI) and Polyester (PET) films, with tailored insights for designers and manufacturers seeking optimized performance.
Enhanced Material Comparison Table
Parameter | Polyimide (PI) | Polyester (PET) |
Glass Transition Temperature (Tg) | 345°C (ASTM D3418), retains 92% modulus at 200°C | 75°C (ASTM D3418), modulus degrades >60% at 85°C |
Coefficient of Thermal Expansion (CTE) | 17–30 ppm/°C (X/Y axis, IPC-2221), 70–100 ppm/°C (Z-axis) | 60–80 ppm/°C (X/Y axis, IPC-2221), 120–150 ppm/°C (Z-axis) |
Dissipation Factor (Df @ 10 GHz) | 0.0035 (ASTM D2520), stable up to 150°C | 0.0028 (ASTM D2520), optimal <85°C |
Tensile Modulus (GPa) | 3.0–4.0 (ASTM D882), anisotropic response | 2.0–2.5 (ASTM D882), isotropic flexibility |
Water Vapor Transmission Rate (WVTR) | 0.5–1.0 g/m²·day (ASTM F1249) | 1.5–2.5 g/m²·day (ASTM F1249) |
Copper Foil Adhesion (N/cm) | ≥7.0 (IPC-TM-650), withstands 288°C reflow | ≥5.0 (IPC-TM-650), limited to 245°C reflow |
Flammability Rating | UL 94 V-0 (0.025mm thickness) | UL 94 HB (0.1mm thickness) |
Surface Roughness (Ra) | 0.8–1.2μm (SEM analysis) | 0.5–0.8μm (SEM analysis) |
Key Technical Differentiators
1.Thermal Management
PI’s low CTE mismatch (17–30 ppm/°C) minimizes thermo-mechanical stress in multi-layer assemblies, critical for high-power LED drivers requiring thermal cycling (-40°C to +125°C).
PET’s high Z-axis CTE (120–150 ppm/°C) necessitates stiffener integration (e.g., 0.1mm stainless steel) to prevent via cracking during soldering.
2，Electrical Performance
PI’s stable Dk/Df profile (Dk=3.5 ±0.1, Df=0.0035 ±0.0005) ensures signal integrity in 5G antenna modules (24–40 GHz).
PET’s lower Dk (Dk=3.2) reduces insertion loss (<0.5 dB/inch) in wearable device sensors, but requires capacitive
compensation for impedance matching.
3.Mechanical Reliability
PI’s high tensile modulus (3.8 GPa) enables 0.075mm bend radius in foldable display hinges, passing 100,000+ flex cycles (ISO 13387-2).
PET’s ductile failure mode (elongation at break >200%) demands stress relief patterns (e.g., serpentine traces) to avoid delamination in automotive wire harness connectors.
4.Chemical Resistance
PI withstands sulfuric acid (98%) and methyl ethyl ketone (MEK) for 1,000+ hours (ASTM D543), critical for battery management systems exposed to electrolyte vapors.
PET requires parylene-C coating (5–10μm) to protect against aliphatic hydrocarbons in industrial IoT sensors.
Manufacturing Process Optimization
PI Lamination:
Use ultrasonic welding (20kHz frequency) for 50μm copper foil adhesion improvement (peel strength +30%).
Implement vacuum pressure lamination (500 mbar) to eliminate microvoids in 4+ layer stacks.
PET Etching:
Apply plasma surface treatment (argon/oxygen mix, 100W power) to enhance solder mask adhesion (cross-cut test >4B, IPC-TM-650).
Optimize etch factor (1.5:1) for 15μm trace/space in high-density sensor arrays.
Conclusion
Choosing between PI and PET hinges on application demands, thermal stability, and budget. At Huaruixin, we empower designers and manufacturers with technical expertise and state-of-the-art solutions. Let’s collaborate to bring your next project to life!
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Email: sales@hrxfpc.com
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Shenzhen Huaruixin Electronics Co., Ltd. – Innovating Flexible Circuits Since 2010.
Disclaimer: The information provided is for educational purposes. For specific technical advice, contact our engineering team.
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