Flexible PCBs and Their Applications in the Next Generation of Electronics

Conventional rigid printed circuit boards reach their design limitations in some applications. Flexible PCBs and their combination with rigid sections in the form of rigid-flex PCBs offer a solution.

Flexible PCB makes it possible to design electronics not only in two dimensions but effectively in three dimensions. A circuit can bend, adapt to the shape of a device, and route signals through areas where a conventional rigid PCB would be too large or structurally unsuitable.

This is why Flex PCBs are becoming increasingly important in the automotive industry, medical technology, consumer electronics, aerospace, industrial electronics, and emerging wearable devices.

What Is a Flexible PCB?

A flexible PCB is a printed circuit board built on a flexible dielectric substrate. Unlike conventional rigid PCBs, its primary supporting material is not a rigid FR-4 laminate but, for example, a polyimide film.

A typical flexible PCB structure can contain one or more conductive layers, dielectric materials, copper foils, coverlay, stiffeners, vias, and other elements required for a specific application.

Depending on their construction, flexible PCB can include:

• single-sided Flex PCBs,
• double-sided Flex PCBs,
• multilayer flexible PCBs,
• rigid-flex PCBs combining rigid and flexible sections,
• flexible PCBs with HDI structures and microvias.

For example, the IPC-6013 standard distinguishes between single-sided, double-sided, and multilayer flexible constructions as well as rigid-flex combinations. Flexible PCB can also incorporate blind and buried vias or HDI layers.

Many of these topics have already been covered in our previously published articles, such as What Are FLEX PCBs? and Flexible Electronics and Innovations in Materials.

Why Are Flex PCBs Important for Modern Electronics?

The main advantage of a flexible PCB is not simply its ability to bend. Its real significance lies in the way it changes how an electronic device can be designed.

A conventional rigid PCB generally requires the design to conform to the approximate shape of a flat board. A Flex PCB, by contrast, allows electronics to be routed around structural elements, folded into a smaller space, or adapted to curved surfaces.

The main advantages include:

• Space savings – a flexible PCB can be folded or routed in multiple directions.
• Lower weight – thin flexible layers can replace part of the cabling, connectors, and other mechanical elements.
• Fewer connections – a Flex PCB can replace several individual wires and connectors, reducing the number of potential points of failure.
• Mechanical flexibility – the circuit can be designed for bending or controlled dynamic movement.
• Design freedom – the electronics can follow the shape of the product and make better use of the available space.
• 3D integration – a flexible circuit can be installed in geometrically complex structures.

IPC identifies flexural durability, three-dimensional installation capability, low weight, and thin construction among the key advantages of flexible PCBs.

Polyimide as the Basis of Flexible Circuits

Polyimide is one of the most widely used materials for flexible PCB. Its importance comes primarily from its combination of mechanical, electrical, and thermal properties.

Polyimide flexible substrates make it possible to create very thin structures that can bend while maintaining electrical functionality.

For demanding applications, however, material selection is considerably more complex.

Designers need to consider, for example:

• the number of bending cycles,
• minimum bend radius,
• dielectric thickness,
• copper thickness,
• coverlay type,
• thermal load,
• electrical parameters,
• required service life,
• mechanical mounting method.

Material selection is therefore not simply a matter of flexibility. The material must be appropriate for the specific mechanical, electrical, and thermal stresses involved.

Rigid-Flex: When Flexibility Alone Is Not Enough

Rigid-flex PCBs, which combine rigid and flexible sections within a single board, represent a particularly interesting area.

The rigid sections can accommodate processors, connectors, or other components that require a stable mechanical base. The flexible section then connects the individual segments and allows them to be arranged in three-dimensional space.

Rigid-flex technology can therefore replace a combination of several conventional PCBs, cable assemblies, and connectors.

Potential benefits include:

• fewer mechanical connections,
• reduced space requirements,
• lower weight,
• simpler assembly,
• better use of the internal space of the device,
• potentially higher system reliability.

IPC therefore gives rigid-flex constructions specific attention. The IPC-2223 standard establishes specific design requirements for flexible and rigid-flex boards and addresses mechanical and physical properties, conductor routing, bend areas, and the construction of connections between rigid and flexible sections.

IPC also lists IPC-2223F in 2026 as a standard for the design of flexible and rigid-flexible boards, demonstrating that this area of PCB design continues to evolve alongside the requirements of modern electronics.

Flexible PCB in the Automotive Industry

Today, a car is essentially a computer on wheels. The number of electronic systems, sensors, cameras, displays, and control units continues to grow.

At the same time, vehicle architecture is changing. Electronics must be lightweight and compact and capable of operating in environments involving vibration, temperature fluctuations, and limited installation space.

Flex PCBs can be used, for example, in:

• sensors,
• lighting,
• camera systems,
• control panels,
• displays,
• seat electronics,
• door modules,
• electric vehicle battery systems,
• interconnections between electronic modules.

In electric vehicles, every gram and every centimeter of installation space can be important. Flexible interconnects can therefore represent an interesting alternative to conventional cable harnesses.

Medical Technology and Wearable Electronics

One of the most interesting areas is the use of Flex PCBs in medical and wearable devices.

Modern wearable electronics are no longer limited to smartwatches. Electronics are increasingly being integrated directly onto the body, into clothing, or into very small medical devices.

Flexible electronics make it possible to develop structures that better conform to the human body.

Current research in flexible electronics focuses, for example, on:

• health monitoring,
• biosensors,
• wearable healthcare,
• flexible sensors,
• motion-monitoring devices,
• neurotechnology,
• implantable electronics.

In 2025, a research team publishing on arXiv presented a flexible packaging method for ALPIDE sensors using aluminium and polyimide layers with thicknesses in the range of tens of micrometres. The construction uses a three-layer flexible PCB with 20 µm aluminium structures and a 25 µm polyimide substrate.

This is a good example of where development is heading: a flexible PCB does not necessarily have to simply connect two components. It can become part of the mechanical and functional architecture of the electronic device itself.

Flexible PCB and Electronics Miniaturization

One of the major trends in modern electronics is miniaturization.

More functions have to fit into increasingly smaller spaces. This applies to smartphones, wearable electronics, medical devices, sensors, and automotive systems.

Flex PCBs offer a significant design advantage here: electronics do not have to be arranged on a single flat surface.

A circuit can be:

bent → folded → routed around a component → adapted to the device enclosure.

This creates opportunities for new types of designs that would be difficult to implement using conventional rigid PCBs.

The next step is to combine Flex PCBs with HDI technology, microvias, and very fine conductive structures. IPC design standards address both flexible PCB and HDI constructions as important areas of PCB design.

Flex PCBs in Aerospace, Space, and Specialized Applications

In aerospace applications, low weight, reliability, and the ability to use limited space efficiently are particularly important.

Flexible circuits can be relevant for applications such as:

• avionics,
• sensor systems,
• satellite electronics,
• camera systems,
• communication systems,
• space-constrained electronic modules.

An interesting example of flexible interconnect technology can also be found in quantum computing research. Researchers have previously demonstrated flexible superconducting transmission structures on thin polyimide substrates as a potentially compact alternative to conventional cabling solutions in cryogenic systems.

This demonstrates that flexible substrates are not simply a technology for consumer electronics. Their properties can also be valuable in highly specialized systems.

A Flex PCB Is Not Simply a “Bent PCB”

When designing flexible circuits, it is important to understand that a Flex PCB is not simply a conventional PCB manufactured from a material that can be bent.

Mechanical stress has a significant influence on conductor design, transitions between rigid and flexible sections, the placement of holes and components, and the use of stiffeners.

The design therefore needs to address issues such as:

• where bending will occur,
• whether the bend is static or dynamic,
• the minimum bend radius,
• how conductors will be routed through the bend area,
• how mechanical strain will be relieved,
• how the Flex PCB will be connected to components,
• how the board will be protected during assembly.

This is why dedicated IPC standards exist for the design and qualification of flexible and rigid-flex PCBs. IPC-6013, for example, defines qualification and performance requirements for flexible boards and covers different constructions, from single-sided boards to multilayer rigid-flex structures.

The Future: From Flex PCBs to Flexible Electronics

The next stage of development may not simply involve making the PCB itself flexible.

The broader concept of flexible and printed electronics is developing, in which not only interconnects but also sensors, transistors, antennas, and other electronic structures can be flexible.

Research is focusing, for example, on printed electronics, flexible sensors, 2D materials, and new conductive materials.

A review study published on arXiv covering research into graphene and MXenes, for example, describes their potential for flexible sensors, pressure sensors, supercapacitors, thermoelectric generators, and heating elements. These technologies have particular potential in wearable electronics, healthcare, and IoT.

Further research published in 2025 points to the development of printed and flexible electronics towards computing directly on or near the sensor. The authors identify reliability, integration of individual components, and efficient memory design as important challenges.

The Challenge for PCB Manufacturers

Flexible PCBs therefore represent much more than another variant of the conventional printed circuit board.

They require a different approach to:

• design,
• material selection,
• manufacturing processes,
• mechanical stress,
• testing,
• assembly,
• quality control.

At the same time, they open the door to electronics that are smaller, lighter, more space-efficient, and more flexible in terms of design.

The development of next-generation electronics will increasingly combine different technologies: rigid PCBs, Flex PCBs, rigid-flex, HDI, microvias, and new materials. The goal will not simply be to manufacture a smaller board, but to design electronics as an integral part of the overall product.

Flexibility as a New Dimension of PCB Design

Conventional PCBs have traditionally defined electronics as a predominantly flat system. Flexible PCB adds another dimension – the ability to adapt electrical interconnections to the actual geometry of the device.

This is precisely where their importance for the next generation of electronics lies.

From smartphones and electric vehicles to medical sensors and systems used in space technologies, there will be an increasing need for electronics that can adapt to the available space, movement, and function of the device.

Flex PCBs are therefore not simply a technology for the future. In many sectors, they are already one of the key technologies enabling miniaturization and the development of modern electronic products.

The manufacturing of flexible PCBs involves specific requirements for materials, design, and production processes. Key factors include the choice of polyimide, copper thickness, conductor routing, minimum bend radius, and the placement of stiffeners and components.

For more complex Flex and rigid-flex designs, it is therefore important to consider manufacturability from the very beginning of the design process. We will cover the manufacturing process and key design rules in a separate article.

Sources

• Novel, D., Lega, A., Facchinelli, T., Iuppa, R., Beolé, S. and Bellutti, P. (2025) ‘A Packaging Method for ALPIDE Integration Enabling Flexible and Low-Material-Budget Designs’ [Preprint]. arXiv. Available at: https://arxiv.org/abs/2503.11208 (Accessed: 4 August 2026).
  
  
• IPC (2021) IPC-6013E: Qualification and Performance Specification for Flexible/Rigid-Flexible Printed Boards. Bannockburn, IL: IPC. Available at: https://www.ipc.org/TOC/IPC-6013D.pdf (Accessed: 4 August 2026).