Everything You Need to Know About Flex PCBs

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The world has become smaller, thanks to the rapid evolution of technology. With burgeoning global demand for connectivity, broadband, lightning-fast data processing capabilities, etc., there has been an equally phenomenal rise in demand for advanced technology products. Flex PCB manufacturing is one such market segment that has noticed considerable growth over the recent past.

Flex circuits are fundamental components of the new electronics era. With them, electronic devices can be made much thinner while still being able to take on a variety of shapes. In fact, many objects today use flexible PCBs to produce exceptional design flexibility and allow for a much more compact form factor. Engineers worldwide are starting to realize the potential of Flexible PCBs and how much they can help save money and boost their businesses. This is why many companies are beginning to consider working with flexible circuits.

This technology is so revolutionary; it is referred to as the polymerization of printed circuit boards. This guide covers all the essential details you need to know about flex PCBs.

flexible printed circuit board

An Introduction to Flex Printed Circuit Boards

Flex PCBs are a type of PCB that has flexible features. This means that they are not rigid like standard PCBs. The flexibility allows them to be bent and shaped in many ways, making them ideal for use in many different applications. These include wearable devices such as smartwatches, fitness trackers, medical devices, and other similar products.

A flex PCB comprises several layers of copper laminate with insulating material between each layer. There are also holes drilled into the board to allow for routing signals from one layer to another. Flexible circuits can be made using various materials, including glass epoxy, FR4, or polyimide film. The insulating material used determines how flexible the board will be; if it is too rigid, it may break during bending operations or when pressure is applied.

The advantages of flex PCBs include:

  • Flexible materials have better electrical properties than rigid ones. This allows circuits to have more components and still be thinner without causing signal loss or interference.
  • There is no need for rigid substrates, which means that the weight of your product can be reduced significantly. This is especially important in aviation, where every gram counts.
  • In addition to being lighter, flex PCBs can also be curved to fit into unusual shapes, making them ideal for use in wearable technology where devices need to be worn on the body, such as smartwatches or fitness trackers.
  • The designs of flex circuits can be customized to meet specific requirements, allowing you to use them in a wide range of applications without needing to make any changes to your design or production process.
  • Flex circuits can be manufactured using existing equipment and techniques, producing them quickly and easily at a low cost with little extra effort.
  • A flexible circuit design is also much easier to create than a rigid one, making it easier for you to develop new ideas and innovations that will help improve your business performance.
  • Flexible circuits allow you to make smaller products with more features than possible on rigid boards. For example, a small laptop computer could have all the functionality of a normal-sized laptop but without its bulkiness or weight.

Types of Flex PCBs

Single-Sided Flex PCB

Single-sided flex boards are usually used for low-frequency RF applications and surface-mount technology (SMT) circuits. Single-sided flex boards are made of FR4, a glass cloth laminate with epoxy resin on both sides of the board. The FR4 material has high dielectric strength and excellent thermal stability. Single-sided flex boards can be fabricated in any shape or size to meet your requirements.

Single-sided flex boards can be made using through hole and surface mount technology (SMT). Through-hole technology is used when many components are on one side of the board that must be soldered through holes drilled into the substrate's top layer. Surface mount technology is used when no through holes are required in the substrate's top layer.

Double-Sided Flex PCB

Double-sided flex PCBs are two separate pieces of copper laminated together with a dielectric. They can be used for almost any electronics application, including power distribution and battery charging systems. Double-sided flex PCBs are also suitable for placing chips on both sides of the board if you need to add more functionality to your device.

In some cases, double-sided flex PCBs may be necessary for your project. For example, if you need to connect more than one device or component to a single board, a dual-layer design may work best for you.

Multi-Layer Flex PCB

Multi-layer flex circuits are created by stacking up several layers of copper on top of each other and then sandwiching them between two polymer layers. These multi-layer boards are typically used for high-density applications because they offer more flexibility than rigid boards where each signal must run directly from one end to another.

Multi-layer flex circuits also offer more flexibility than double-layered boards because they allow you to route signals between different layers on the same board without going through an external connector or wire harness, which makes your product smaller.


HDI stands for high-density interconnect and refers to flex PCB with a relatively high number of copper pads per square inch. This makes it possible to achieve high levels of connectivity with minimal trace widths, which translates into increased speed and efficiency. An HDI flex circuit can be used in any application requiring high-bandwidth data transfer. For example, HDI flex circuits are commonly found in computer motherboards, video cards, and other high-speed electronics.

Flex PCBs: Common Applications

Flex PCBs are used in a variety of applications. The most common applications include:

Smart Garments

The ability to bend or flex a circuit board allows for more comfortable and practical designs for everyday use. For example, smart garments may be designed with flexible circuits that enable them to stretch with the body. This could be used in sports clothing or other garments designed to keep you cool while exercising.

Medical Devices

Flexible circuit boards can also be used in medical devices such as artificial joints, prosthetics, and pacemakers. These devices allow patients with limited mobility to perform everyday tasks more efficiently, which improves their quality of life.


Wearables have become increasingly popular over the past few years as consumers look for ways to monitor their health and fitness levels. Some wearables allow users to track their heart rate, calories burned and steps taken throughout the day, while others provide notifications when they need rest or fluids due to dehydration or heat exhaustion.

Flex PCB Primary Components

A flex PCB contains many different components that allow it to function correctly. Some of these include:

The Flexible Circuit Substrate

The flexible circuit substrate is the base material of the flex circuit board, which provides mechanical strength. It is usually made from polyimide or polyester materials processed through lamination or curing methods such as UV curable resin or oxygen plasma treatment (OPT).


Wires are one of the most critical components of a flex PCB. The cables make it possible for electricity to flow through the device, making it possible for it to function correctly. Many different types of wires are available, including copper and gold wires, which offer high conductivity and corrosion resistance, respectively.


Dielectric refers to any material that can insulate an electric charge from another source. It is usually made from FR4 material.

Copper Laminate

Copper laminate is a copper foil that has been die cut into desired shapes and sizes to create electrical connections between layers on the flex circuitry board.


Pads are where you connect components to the circuit board using solder paste or solder masking tape during manufacturing. Once soldered, they provide mechanical support and protection for components during the use of your product.


Capacitors on a flex PCB are used to store electrical energy so that it can be released later when the user needs it. They work by storing an electrical charge on two parallel plates, separated by an insulating material such as mica or plastic film. This allows them to store energy until the device needs it and then release it when needed without affecting other parts of the circuit board or system in which they are located.

Flex PCB Manufacturing Phases

pcb flex

Summing Up

Ultimately, flexible PCBs are an intriguing electronic design innovation that is likely to stay. Just as we are seeing more and more manufacturers start using flex PCBs, it seems that the market is getting a bit more competitive these days. In any case, we hope this guide has helped you better understand this emerging technology for future use. Give them a try on your next design and see how they can improve your assembly workflow.

If you have a flexible design that needs PCB manufacturing, or if you are developing a product that may be better suited for a flex PCB or any other kind of specialty PCB, then look no further than HemeixinPCB.

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