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Flexible PCB: Introduction, Types, Materials and Its Applications

What is a flexible printed circuit board？

Speaking of circuit boards, everyone may not be unfamiliar. Almost all electronic products in our lives need printed circuit boards. However, there are many types of circuit boards. So what is a flexible PCB?

Introduction of the flexible circuit board

Flexible PCB is also known as the flexible printed circuit board, flexible printed circuit, or flexible circuit board. We call it this name because it allows the circuit to be flexibly designed to fit electronic devices or products rather than just being constructed on the circuit board.

Simply put, the flexible PCB is composed of multiple printed circuits and components located on the flex circuit board. These flexible circuit boards use the same component design as rigid PCBs. However, the only difference is that the flexible PCB board is made so that it can be bent into the required shape during application.

4 Types of Flexible Printed Circuits

Single-sided flexible PCB:

This is one of the basic types of the flexible circuit board. The single-sided flexible PCB includes a single layer of flexible polyimide film and a thin copper layer. The conductive copper layer can only be accessed from one side of the flexible printed circuit.

Dual-channel single-sided flexible PCB:

As the name suggests, these flex circuit boards are single-sided. But the copper plate or conductive material can be contacted from both sides of the flexible PCB board.

Double-sided flexible PCB:

These flex board PCBs have two layers of conductors on each side of the base polyimide layer. The flex circuit design between the two conductive layers is realized by using metalized plated through holes.

Multi-layer flexible PCB:

Multi-layer flexible PCB is a combination of multiple double-sided and single-sided flexible printed circuits. These flex printed circuits are connected through plated through holes or surfaces mounted with adhesive patterns.

Materials used in flexible PCB

Although most standard PCB have fiberglass or metal bases. But generally, the core of a flexible printed circuit is composed of flexible polymer. Most flexible printed circuit boards are based on polyimide (PI) film.

The advantage of this kind of PI film is that it does not soften when heated but remains flexible after heat curing. Many other thermosetting resins will harden after heating, making PI a high-quality material in flexible PCB structures.

Generally, standard PI film does not have good moisture resistance and tear resistance. In this case, you can choose an upgraded PI film to alleviate these problems.

Flexible PCB also require adhesives or particular substrates to connect. In the past, the flex PCB manufacturer only used adhesives, but this method reduced the reliability of the flex circuit board.

To solve these problems, flex circuit board manufacturers have developed adhesive-free PI. This material can achieve a thinner design while reducing the risk of through-hole damage. The flex circuit manufacturer does not use a solder mask to cover and protect the flex printed circuit but instead uses a cover film made of PI.

If you want the area on the flexible PCB to be rigid, the flexible circuit manufacturer can laminate a harder area on this part. But it should be noted that the signal cannot propagate between the flex and the harder area.

Rigid-flex pcb vs. rigid pcbs and flexible pcb

As the name suggests, rigid-flex PCB is a mixture of rigid PCBs and flexible PCB. Rigid-flex PCB combines the excellent qualities of both while eliminating many of their limitations. Rigid-flex PCB combines flex circuit design with rigid materials.

By layering the flexible PCB board inside the rigid printed circuit board material, the versatility of the flexible printed circuit is finally combined with the stability, strength, and circuit wiring density of the rigid printed circuit board. This mixing opens up a series of possibilities for more complex and mechanically challenging rigid-flex PCB designs.

Rigid-flex PCB simplifies the electronic design by eliminating flexible cables, connectors, and discrete wiring. Its electrical performance has been enhanced compared to its counterparts because the circuit is an integral part of the overall structure. All electrical and mechanical connections are contained in the rigid-flex PCB, providing electronic designers with greatly improved service reliability and electrical performance.

Although the cost of rigid-flex PCB is usually higher than flexible PCB and rigid PCBs. However, the reliability, weight reduction, strength, and space-saving advantages of rigid-flex PCBs are generally ideal in specific applications and are superior to any other electronic packaging technology. Ultimately, rigid-flex PCB provides the best benefits of rigid PCBs and flexible PCB in one solution.

What are flexible PCB used for?

Application of flexible PCB:

There are two basic types of applications for flexible PCB.

Static application: install flexible PCB to adapt to a specific application. It can be understood as a one-time bending. (Also called flex-to-fit)

Dynamic bending application: As part of the final product application, the flexible PCB is bent multiple times.

People are increasingly using flexible PCB for electronic products, such as calculators, mobile phones, printers, and LCD TVs. In addition, they are also used in heart monitors, pacemakers, and hearing aids in the medical field. It even includes manufacturing robotic arms, processing machines, bar code equipment, etc. In fact, the applications of flexible PCB are endless.

PCBasic provides a flexible printed circuit board at a low cost

PCBasic is one of the most popular flexible pcb manufacturers in Shenzhen, China. We specialize in producing flexible pcbs with low price and high quality. These flex circuit boards are custom-designed according to customer needs. Just look at the "product categories" that PCBasic specializes in, and you know how much we have expanded over the years.

These categories include data communications, optical networking, medical, industrial control, aerospace/military, etc., to name a few.

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