Types of Flex Circuits

Flex and rigid-flex circuits are available in a variety of configurations to meet a broad range of application requirements. Below you will find information regarding the different types of flexible circuits available from a single- or double-sided design to multi-layer technologies, including rigid-flex circuit design specifications.

See our technical article for more information on flex circuit material and construction methods or see our past flex circuit technical webinar to better help you design your next flexible PCB.

At a Glance: Types of Flex Circuits

• Flex and rigid-flex circuits are available in single-layer, double-sided, multi-layer, and rigid-flex configurations, each designed to support different electrical, mechanical, and space-constrained requirements.
• Material options include adhesive and adhesiveless polyimide constructions, copper weights from 1/3 oz to 2 oz, and a variety of stiffener materials including polyimide, FR4, stainless steel, and aluminum.
• Advanced configurations support controlled impedance designs, dynamic flex applications, blind and buried vias, EMI/RF shielding, and complex interconnect requirements.

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Single-Layer Flex Circuit

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Double-Sided Flex Circuit

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Multi-Layer Flex Circuit

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Rigid-Flex Circuit

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Frequently Asked Questions

Quick Links

• What is the difference between a single-layer flex circuit and a double-sided flex circuit?
• When should a multi-layer flex circuit be used?
• What are the advantages of rigid-flex circuit technology?
• What material and construction options are available for flex circuits?
• Which flex circuit type is best for dynamic flex applications?

What is the difference between a single-layer flex circuit and a double-sided flex circuit?

A single-layer flex circuit contains one conductive copper layer positioned between insulating polyimide layers. Double-sided flex circuits contain two conductive copper layers separated by an insulating polyimide core and connected through plated through-holes. The additional copper layer allows for increased routing capability and more complex circuit designs. Double-sided constructions can also support high-speed controlled impedance designs in surface micro strip configurations.

When should a multi-layer flex circuit be used?

Multi-layer flex circuits are used when a design requires three or more conductive layers within a flexible construction. These circuits provide increased routing density and can support controlled impedance designs using surface micro strip or stripline configurations. Multi-layer flex circuits use plated through-holes to connect layers throughout the stack-up. According to the source, these constructions are intended for bend-to-fit applications rather than dynamic flex designs.

What are the advantages of rigid-flex circuit technology?

Rigid-flex circuits combine flexible and rigid circuit sections within a single design. The construction can include multiple rigid layers, one or more flexible layers, plated through-holes extending through both rigid and flexible regions, and optional blind and buried vias. This configuration allows designers to reduce interconnect complexity while supporting compact packaging requirements. Rigid-flex circuits can also support controlled impedance designs and selected dynamic flex applications when one or two flex layers are used.

What material and construction options are available for flex circuits?

Flex circuits can be manufactured using adhesive or adhesiveless polyimide core materials with standard thicknesses ranging from 1/2 mil to 4 mil depending on the construction type. Copper thicknesses are available from 1/3 oz to 2 oz in rolled annealed or electro deposited formats. Coverlays typically consist of polyimide with epoxy or acrylic adhesive systems. Additional options include polyimide, FR4, stainless steel, or aluminum stiffeners, pressure-sensitive adhesives, and EMI/RF shielding films.

Which flex circuit type is best for dynamic flex applications?

The appropriate flex circuit type depends on how the circuit will move during operation. Single-layer flex circuits are suitable for both bend-to-fit and dynamic flex applications. Double-sided flex circuits may also be used in dynamic flex applications depending on the construction. Rigid-flex circuits can support dynamic flex applications when configured with one or two flex layers. Multi-layer flex circuits, however, are identified in the source as bend-to-fit constructions rather than dynamic flex solutions.

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The Perfect Fit for Your Application

From single-layer to multi-layer flex circuits, we've got configurations to meet your most complex design needs. Whether you're engineering next-generation medical devices, aerospace avionics, military communications equipment, automotive control systems, or consumer electronics, Epec delivers precision, durability, and performance in every flex or rigid-flex PCB we build.

Our experience supporting applications across industrial automation, IoT, and wearable technologies ensures that your design will be ready to meet both performance and regulatory standards. Act now for precise, reliable, and cost-effective solutions for your next PCB design!

Explore more, Common Flex and Rigid-Flex Printed Circuit Board Material Stack-Up.

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