As the global PCBA industry continues to grow, more engineers and buyers are searching for advanced circuit board materials. One phrase that frequently appears in Google search is “Polyimide Rigid PCB”. However, this term is misleading because polyimide is not used to manufacture rigid boards—it is primarily a flexible PCB substrate.
Polyimide (PI) is a polymer material known for its excellent thermal stability, mechanical strength, and electrical insulation. Because it can bend and fold without damaging circuitry, polyimide is the core material behind flexible PCB technology. Polyimide materials were first developed in the early 1900s and entered commercial production by 1955. Today, they are typically available in yellow, amber, or orange colors and are widely used in high-performance electronics.
Below, YILONG provides a comprehensive technical explanation of Polyimide PCBs materials, their classifications, manufacturing processes, advantages, and comparison with FR4.
What Is Polyimide PCBs?
A Polyimide PCBs is a flexible or flex-rigid circuit board that uses polyimide film as the base material. These boards are valued for their durability, temperature resistance, and ability to withstand repeated bending. As product designs continue to move toward lightweight and compact structures, polyimide flexible PCB demand is increasing significantly.
Types of Polyimide PCBs Materials
2nd-Generation Polyimide (Pure Polyimide)
This is the most common version of polyimide material, offering high flexibility, excellent heat resistance, and strong chemical stability. Pure polyimide films do not require brominated flame retardants, making them suitable for demanding electrical and communication devices. Their softness and durability allow them to perform reliably in vibration-heavy environments.
3rd-Generation Polyimide (Flame-Retardant Polyimide)
The third-generation polyimide adds flame-retardant additives to meet safety requirements in industries such as medical, aerospace, and industrial equipment. While its flame-retardant performance is superior, it has slightly reduced flexibility, making it easier for manufacturers to process.
Low-Flow Polyimide
Low-flow polyimide has reduced resin viscosity, enabling precise placement during lamination. This material is ideal for fine-pitch and complex flexible PCB structures. With strong flame-retardant and chemical-resistant properties, low-flow polyimide performs well in high-stress environments. Its cost is higher, so it is typically used for advanced electronics.
Filled Polyimide
To improve stiffness, strength, and chemical resistance, fillers such as glass fiber, carbon fiber, or mica are added.
l Glass fiber provides strength at low cost.
l Carbon fiber offers excellent stiffness for high-performance electronics.
l Mica-filled polyimide is used for semiconductors and aerospace where extreme chemical resistance is required.
Comparison of Polyimide PCBs Materials
Leading manufacturers such as DuPont and Isola offer different grades of polyimide films, including Kapton HM and Isola P95.
l Kapton HM: High toughness, excellent thermal stability, and strong chemical/corrosion resistance.
l Isola P95: High dielectric strength and thermal performance for high-voltage or high-temperature applications.
l Polyimide materials typically offer wide operating temperatures, high dielectric strength, and excellent durability, making them ideal for advanced electronics and harsh environments.
Polyimide Flexible PCB Manufacturing Process
YILONG produces polyimide flexible PCBs through a controlled and precise manufacturing process. The general steps include:
1. Raw Material Preparation: Polyimide film is laminated with copper foil using a specially formulated resin.
2. Lamination: Heat and pressure bond the copper foil to the polyimide substrate, forming a stable copper-clad laminate.
3. Drilling: CNC or laser drilling creates micro-vias and connection points. Polyimide requires careful drill control due to its brittleness.
4. Silkscreen Printing: Photo-sensitive ink and stencils are used to transfer circuit patterns onto the board.
5. Etching: Chemical etching removes excess copper, leaving the designed circuitry.
6. Plating: Copper plating enhances conductivity and strengthens vias and traces.
7. Testing: Electrical, thermal, and visual inspections ensure proper performance.
8. Assembly: Components are mounted using SMT or THT techniques. Soldering is performed in a clean environment to avoid contamination.
Advanced Techniques Used in Polyimide PCBs Manufacturing
To meet the growing demands for micro-electronics and high-density circuits, several advanced processes are used:
l Semi-Additive Process (SAP) for finer trace width/spacing
l Modified SAP for ultra-high density interconnect (HDI) applications
l Electrodeposited Polyimide Copper Coating for improved reliability
l Laser Direct Imaging (LDI) for precise micro-circuitry
Why Choose Polyimide PCBs?
Dimensional Stability
Polyimide boards maintain structural accuracy within a wide temperature range, making them ideal for precision electronics.
Flexibility Options
Based on the design, different polyimide materials can offer flexibility, rigidity, flame-retardancy, or chemical resistance.
High Dielectric Strength
Ensures safe operation in high-voltage systems.
Higher Cost
Polyimide material and manufacturing are more expensive, which must be considered during planning.
Limited Thickness Options
Polyimide substrates are thinner than FR4, which may not suit applications requiring thicker board structures.
Applications of Polyimide PCBs
Polyimide flexible PCBs are widely used in industries requiring durability, lightweight design, and superior heat resistance:
l Automotive electronics: ECU modules, sensors, power systems
l Medical devices: X-ray systems, monitors, diagnostic tools
l Military and defense: radar, avionics, communication modules
l Consumer electronics: smartphones, laptops, wearables
l Computing & servers: processors, GPUs, power modules, data centers
Polyimide vs FR4 — Key Differences
|
Feature |
Polyimide |
FR4 |
|
Flexibility |
Highly flexible for dynamic bending |
Rigid, not bendable |
|
Thermal stability |
Can withstand 250°C+ |
Typically 130–140°C |
|
Chemical resistance |
Excellent and inert |
Moderate |
|
Flame retardancy |
Can be flame-retardant |
Standard flame-retardant grade |
|
Cost |
High |
Low |
Polyimide clearly outperforms FR4 in thermal, mechanical, and chemical properties, making it the preferred choice for high-performance flexible PCBs.
Conclusion
Polyimide PCBs have become essential in modern electronics where reliability, flexibility, and high-temperature resistance are required. As electronic designs continue to evolve, demand for polyimide flexible PCBs will keep rising. With strong expertise in polyimide materials and flex-rigid manufacturing, YILONG can support advanced PCB solutions for automotive, medical, aerospace, and consumer electronics applications.
If you need custom Polyimide PCBs, flexible PCB, or flex-rigid PCB solutions, feel free to contact YILONG for technical support and quotation. Email: yilong@yilonginsulation.com www.yilonginsulation.com.
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