Flexible circuit boards are printed circuits made from a polyester film or polyimide substrate. These circuit boards are highly reliable and have excellent bending properties. By embedding the circuit design in a thin, lightweight, bendable plastic sheet, a large number of precision components can be stacked in a narrow and limited space, resulting in a bendable, flexible circuit.
Pure Flexible Circuits: Utilizing polyimide (PI) or polyester (PET) substrates
Rigid-Flex Circuits: Integrating FR4 with flexible sections
Stretchable Circuits: Emerging elastic substrate technologies
1. Product Benefits
Bend radius: ≥3× board thickness for dynamic applications (IPC-6013 standard)
Weight density: 0.5–1.2 g/cm³ (60% lighter than rigid PCBs)
Thermal stability: -65°C to 200°C (PI substrate)
Flexible circuits are known for their flexibility and elasticity. They can be bent, twisted, and folded without compromising their functionality. This inherent flexibility makes them ideal for applications where space is limited or PCBs need to conform to complex shapes. They are also less prone to mechanical failure, making them suitable for harsh environments and applications that require frequent movement.
One of the most significant advantages of flexible printed circuits is their ability to reduce weight and size in PCB assembly. By eliminating the need for connectors and reducing the number of interconnections, flexible PCBs can significantly reduce the overall size and weight of a device. This is especially important in industries such as aerospace, where weight and space constraints are key factors.
2. Substrates
Substrate Performance Matrix
| Parameter | PI Film | PET Film | LCP Film |
|---|
| Dielectric Loss (10 GHz) | 0.002 | 0.025 | 0.001 |
| CTE (ppm/°C) | 15–20 | 50–70 | 5–10 |
| Tensile Strength (MPa) | 250 | 180 | 300 |
Advanced Conductor Technologies
Ultra-thin rolled copper foil: >500k bend cycles at 12µm thickness
Nano-silver conductive ink: 30µm line width resolution
Anisotropic Conductive Film (ACF): Z-axis resistance <0.1Ω
3. PCB Design Principles
Dynamic Bending Solutions
Serpentine trace design: Strain relief structures
Neutral axis calculation: ε = (t/2R) × 100% ≤ 0.3%
Reinforcement zone optimization: Local FR4/PI stiffeners
High-Frequency Signal Integrity
Differential pair impedance control: ±10% tolerance
Transmission loss: <0.5 dB/inch @10 GHz
Embedded shielding layer: Surface resistance <1 Ω/sq
Flexible PCB Application Areas
Flexible Printed Circuit Boards (FPCs) are used in a wide range of applications covering a variety of fields, including mobile devices, in-vehicle systems, medical devices, industrial automation and power control, aerospace and military, home appliances, and display technology.
Topfast offers high quality flexible circuits designed to meet the needs of the most demanding applications, providing a high degree of flexibility and reliability.