A Complete Guide by MultPCB
When choosing materials for flexible printed circuit boards (Flex PCBs), the most common question we hear at MultPCB is:
Should I use PI or PET for my Flex PCB project?
Both PI (Polyimide) and PET (Polyester) are widely used in the electronics industry—but they serve very different purposes. In this article, we’ll break down their differences and help you decide which material is best for your application.
When designing flexible PCBs, one of the first decisions you’ll face is choosing the right base material. Two of the most commonly used materials are Polyimide (PI) and Polyester (PET). While both are flexible, they have significant differences in thermal stability, cost, mechanical performance, and application suitability.
In this article, we’ll compare PI vs PET for flex PCB applications, so you can make the best material choice for your next project.
🔍 What Are PI and PET?
✅ Polyimide (PI)
Polyimide is a high-performance thermoplastic polymer known for its excellent heat resistance, flexibility, and chemical stability. It’s widely used in advanced flex PCB designs due to its durability and ability to handle high temperatures.
✅ Polyester (PET)
Polyester, or PET, is a lower-cost alternative to polyimide. It’s commonly used in static or disposable electronics applications where thermal demands are lower. PET is known for its smooth surface and optical clarity, but it has limitations in high-temperature environments.
PI vs PET Comparison Table
| Feature | PI (Polyimide) | PET (Polyester) |
|---|---|---|
| Max Operating Temp | Up to 260–300°C | Up to 150°C |
| Flexibility | Excellent (ideal for dynamic flex) | Good (best for static flex) |
| Thermal Stability | Excellent | Moderate |
| Chemical Resistance | Strong | Moderate |
| Electrical Performance | High insulation, low dielectric loss | Good insulation |
| Moisture Resistance | Very good | Moderate |
| Cost | Higher | Lower |
| Common Thickness | 0.0125–0.125 mm | 0.050–0.100 mm |
| Use Case | Aerospace, Automotive, Medical | LED strips, Toys, Keyboards |
When to Use PI for Your Flex PCB
MultPCB recommends PI for applications that require:
- High temperatures or soldering processes
- Repeated bending or dynamic movement
- Miniaturized, multilayer, or high-density designs
- Mission-critical reliability (e.g. aerospace, military, automotive, medical)
PI is the industry standard for high-end Flex PCBs.
When to Use PET for Your Flex PCB
PET is a good option when your application:
- Does not involve soldering
- Is cost-sensitive
- Will experience minimal or no bending
- Is for disposable or static products, such as:
- LED light strips
- Consumer remote controls
- Membrane switches
- Toys and novelty electronics
PET works great in low-cost, low-heat environments.
How MultPCB Can Help
At MultPCB, we specialize in manufacturing both PI-based and PET-based Flex PCBs. Whether you need a single-layer static circuit or a complex multi-layer rigid-flex design, our team can help you select the right material and structure for:
- Performance
- Flexibility
- Budget
✅ Our Flex PCB Capabilities Include:
- 1 to 6 layers
- 0.05 mm to 0.5 mm thickness
- OSP, ENIG, Immersion Silver surface finishes
- Coverlay or solder mask options
- RA Copper for enhanced flex life
- Rapid prototyping & volume production
📝 Final Thoughts: PI or PET?
| Choose PI if… | Choose PET if… |
|---|---|
| You need high heat resistance | You want a low-cost static solution |
| Your board will flex repeatedly | The circuit will stay flat and unmoving |
| Your product needs long-term reliability | It’s a temporary or disposable device |
| Your design requires tight tolerances or soldering | Your PCB doesn’t involve high-temp processes |
📞 Let’s Build Your Flex PCB Together
At MultPCB, we’re more than just a supplier—we’re your engineering partner. From material selection to final testing, we help ensure every flex PCB we deliver meets your performance and reliability goals.
💬 Contact us at sales@multpcb.com
🌐 Learn more at www.multpcb.com
📦 Free samples and fast quotes available on request!
