What is Flex PCB? – A Comprehensive Guide For Flexible Circuit Board

Over the years, consumer products such as mobile phones have become more complex, a far cry from electronic products produced 30 years ago. The introduction of the flexible circuit board, better known as the flex PCB, made it possible to combine different components to make these complex products with lightweight and small dimensions.

Flexible circuit boards played a significant role in creating lighter and multi-functional products. An excellent example is the laptop, first introduced in April 1981. The early version of laptops weighed about 24 pounds and had a memory of only 64KB. Today, most laptops weigh between 2 and 5 pounds and have a RAM of at least 8GB or 16 GB. Hence, despite being lighter, today’s laptops are more powerful than their early predecessors.

Laptop users owe these desirable features to the introduction of flexible circuit boards, which allowed modern-day laptops to become more potent despite reducing their weight.

What is a Flexible Circuit Board?

Flexible circuit boards have become popular among electronics manufacturers because of their unique qualities, which set them apart from rigid PCBs.

It is an ultralight polyimide or polymer circuit board. This type of PCB is made of conductive copper strips laminated into a flexible layer base and insulated by a solder mask. Because it does not need rigid PCB material, the circuit board becomes bendable so that you can contort it without damaging it.

Types of Flexible Circuit Boards

Single Layer Flexible Circuit Board

1. Single-sided flex PCB

The single-sided flexible circuit board is the most basic among the types of flex PCBs. It consists of a substrate layer, conductive copper layer, coverlay, and silkscreen. 

It only has a single layer of flexible polyimide or polymer film, and the conductive copper layer is only accessible on one side of the PCB. As a result, the other side can be used to put various electronic components. Its simple design makes it suitable for various applications and more affordable for brand owners, and also easier for PCB suppliers to produce it in large quantities quickly. Hence, it is also the main reason why it is the most widely used flex circuit.

2. Double-sided flex PCB

As the name suggests, double-sided flex PCBs have two copper layers on flexible polyimide or polymer film. Unlike the single-sided flex circuit, a double-sided flexible circuit board allows the creation of trace patterns on both top and bottom sides. You can connect each side using the copper-plated through-holes wherever you want. It also permits electrical connections via the layers.

One advantage of the double-sided flexible circuit board is that it can be used more complex electronic products to achieve more functions. Manufacturers have found it useful in making dashboard components, lighting and other industrial areas.

3. Multi-layered flex PCB

On the other hand, a multi-layered flexible circuit board combines three or more copper layers. Several copper layers in multi-layered flexible PCB boards are joined together by plated through holes, similar to those in double-sided boards. Multilayered flexible PCBs contain a number of individual copper layers and dielectric layers.

One of the benefits of using a multi-layered flexible circuit board is freedom in design with multiple functions. Manufacturers can use it for those with complex design requirements. It is utilized to make components for mobile phones, satellites, cameras, and hearing aids.

Flexible Circuit Board

Advantages of a Flexible Circuit Board

Flexible circuit boards offer many benefits, which is why they have become a popular choice among electronics product manufacturers regarding PCBc. Here are five key advantages of using flex circuits in your electronics components:

  • Freedom of design

Flex circuit boards give designers freedom of design because they are not limited to two layers but can be multi-layered. You can combine single-sided and double-sided flex circuits, which allows designers limitless design opportunities. A flexible circuit board is your best choice for creating components with complicated configurations and needing a handful of interconnections.

  • Flexibility

One of the most significant advantages of flex circuits is their flexibility, which allows you to join several planes during the execution. As a result, weight is greatly reduced, saving you from space issues common among rigid circuit boards. Flex circuits are highly bendable, allowing manufacturers to flex or distort them at different levels based on the requirements needed without compromising their integrity.

  • Reliability

PCB manufacturers can attest to the importance of interconnect circuit boards, especially in modern-day consumer products. With flex circuit boards, interconnection failure will not be an issue. Flex circuit boards allow the design of circuit boards that contain fewer interconnection points, which enhances reliability even in challenging conditions. Flex circuits also boast improved thermal stability because of the polyimide material used in the circuit boards.

  • Durability

Durability is another essential benefit of a flexible circuit board. Consumer products today need to withstand wear and tear, which makes flex circuits ideal in the manufacturing industry. PCB suppliers revealed that a flexible circuit board can extend the average lifespan of an electronic device to 500 million times. Also, flex circuits are bendable up to 360 degrees. They are known to survive the impact of vibrations and shocks, which enhances performance in any application.

  • Suitable for high-temperature

Aside from durability, a flexible circuit board is proven to withstand high temperatures because of its polyimide material. It can also endure acids, oils, and gasses. Flex circuits can be exposed to high temperatures of up to 400 degrees Centigrade and still function correctly and in harsh environments.

Double Llexible Circuit Board

Applications of Flexible Circuit Board

Since its introduction, flexible circuit boards have emerged as popular circuit boards across many industries. Here are three sectors that find flex circuit boards useful in their products: 

  • Aerospace

Flexible circuit boards are known to withstand vibrations and high temperatures. Hence, it is the primary PCB choice for components used to make aerospace products. Flex circuit boards have become ideal components for producing satellites and planes. These products need components that can endure extreme temperatures in the atmosphere and space and remain functional despite being subject to vibrations while flying or during liftoff.

Since flex circuit boards can be distorted into different shapes, they are suitable for components in spacecraft that are always subject to extreme environments.

  • Consumer electronics

Data showed that more than 33 percent of sales on flexible circuit boards are used for printers, smart devices, scanners, and other computer-related devices. Flex circuits are crucial for computer technology, which continues to change and requires smaller, more portable products. A flexible circuit board can do the job for tech products that need heavy computing capacity without increasing the weight.

  • Automotive components

Another industry that relies on flexible circuit boards is the automobile industry, which is the second largest user of flexible circuit boards. It is no surprise that the hardware used in cars nowadays is more advanced and requires the help of a flexible PCB. It is being utilized for car sensors, dashboards, cameras, and GPS. 

  • Medical devices

The medical device industry is one of the beneficiaries of flex circuit boards. Many medical devices need a lot of capabilities without sacrificing weight. Most medical devices must be powerful but lightweight, which becomes achievable with the help of flex PCBs. For example, flex circuit boards are instrumental in the creation of hearing-assist devices with a higher range and resolution than those currently in the market. 

In many medical devices used in surgery and health monitoring, flex PCBs allow the design of compact devices to fit in the ear or enter a person’s intestines. 3

  • Wearable devices

Another area that benefits from flexible circuit boards is wearable devices. Among the requirements for wearable devices are that they are lightweight and thin. Being lightweight is non-negotiable when it comes to wearable devices. A good example is smartwatches. Consumers would only be interested in buying smartwatches that are light enough to be carried on their wrists. Its weight must allow it to be worn on the wrist without making you uncomfortable. It is only possible with the flex circuit boards, which will make the product lighter without losing its functionalities.  

Flex circuit boards are found in products such as Apple Watch, smart jewelry, headsets, augmented reality glasses, and health monitoring patches.


Undoubtedly, flexible circuit boards have become essential in making products that are more powerful but portable in many industries. Components for aircraft, medical devices, cars, and even those used in daily life rely on flexible circuit boards to become lightweight without compromising capabilities. 

As technology improves and products continue to innovate, flex PCBs will remain the primary choice in making circuit boards for products created by various industries.

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