Flexible PCB Manufacturing & Design Guide

Flexible PCB, is a lightweight and bendable circuit board designed to connect electronic components in limited or dynamic spaces. Compared with rigid PCBs, flexible circuits can fold, twist, and fit into compact electronic designs, making them essential in modern electronic products. At DOUBLEPORT, we provide complete solutions for flexible PCB fabrication, design, and assembly. This page gives you a full overview of flexible PCB structure, materials, manufacturing process, and key applications.

Flex PCB made by laminating a layer of copper foil (usually 18μm, 35μm, 70μm, etc.) to a substrate by hot pressing or chemical deposition, and then etching and other processes. Therefore, the flex PCB does not have a solid rigid support in structure, but relies on its own flexible material to support the layout of the circuit. Flex Plus is able to manufacture ultra-thin flex PCB with a thickness of only 5μm, providing more options for compact, lightweight, and high-performance applications.

What Is a Flexible PCB?

A Flexible PCB is a copper circuit laminated on a flexible base film, typically polyimide (PI) or polyester (PET).

This construction allows the circuit to bend or fold without breaking the copper traces.

Flexible PCBs are commonly used in smartphones, medical devices, automotive electronics, and aerospace systems — where space saving and high reliability are required.

Structure and Materials

A flexible PCB is composed of several main layers:

1. Base Film (PI or PET) – provides flexibility and insulation.

2. Copper Foil – forms the conductive circuit.

3. Adhesive (Optional) – used in adhesive-based constructions.

4. Coverlay Film – protects the copper traces while allowing openings for pads.

5. Stiffener (PI or FR4) – adds mechanical strength to connector areas or component zones.

6. PSA (Pressure Sensitive Adhesive) – used when bonding to other parts.

There are two major constructions:

Flexible PCB  with Glue– uses glue between copper and PI layers, lower cost but less heat resistant.

Flexible PCB without Glue – directly laminated without glue, higher performance for fine-pitch or high-temperature designs.

Flexible PCB Manufacturing Process

The flexible PCB manufacturing process requires precision control at every step to ensure dimensional stability and consistent impedance. The general process includes:

1. Base Material Cutting

2. CNC Drilling or Laser Drilling

3. Pattern Imaging and Etching

4. Plating (Through-hole / Surface)

5. Coverlay Lamination and Curing

6. Stiffener or PSA Attachment

7. Profiling and Punching

8. Electrical Testing and Visual Inspection

Each step must maintain cleanliness, accuracy, and temperature control to avoid dimensional shift or copper cracking.

Advantages and Limitations

Advantages

1. Ultra-thin and lightweight

2. High flexibility and bend radius

3. Reduced wiring space and assembly weight

4. Excellent thermal dissipation

5. Suitable for dynamic or movable connections

Limitations:

1. Higher material and tooling cost

2. Complex manufacturing and assembly process

3. Requires strict handling to avoid damage

However, with proper design and supplier experience, flexible PCBs can provide unmatched reliability for compact electronics.

Need a custom Flexible PCB Solution?

Our engineering team can help you select materials, optimize stack-up, and provide one-stop manufacturing.

Contact DOUBLEPORT for your next project.