Introduction to Flexible Printed Circuit Board


It is an electrical circuit that connects electrical components with conductive copper wires to give mechanical support? It’s the foundation of many electronic projects, allowing for smaller, more compact, and less unpredictable designs.

Compare circuit boards installed in TVs in the 1990s to those available in modern LED designs and smartphones, and you’ll see how PCBs have grown over time into a more sophisticated circuit board.

Single-layer, double layer, multiple layer PCB boards, as well as rigid, flexible, rigid-flex, and aluminum circuit boards, are all varieties of PCB boards. Only flexible circuit boards will be discussed in this article.

Let’s get started.

A flexible circuit has a conductive layer of traces made out of copper wire.

Flexible PCB Manufacturing Process:

Flexible PCBs are made from polyimide as the base substrate material. Because this material is more expensive than FR-4, it must be utilized with caution. The nesting technique is used to keep circuit boards close to each other to make the most of the polyimide material.

Looping is One of the Steps in Making Flexible Boards.

The service loop guarantees that the servicing length and circuit assembly, which is the amount of extra material added beyond the designer’s limit, are both met.

Conductor Sizing

On the board, thin copper is used as a conductive substance. The circuit’s flexibility is due to the thin copper, which makes it appropriate for dynamic applications.


To compensate for any isotropic losses during the manufacturing process, the etching technique is performed. Copper foil thickness is half the line width loss in this technique. Conductor, etch mask, and the numerous types of conductors employed are all factors that influence line width.


Routing is straightforward. Routing reduces tension and makes bending and folding easier.

Planes that fly on the ground

Ground planes will help to lighten the load.

The use of ground planes reduces the board’s weight and improves circuit flexibility.

Before applying to fillet, you must first create holes to expand the pad area and split tension. Then, for dynamic flex circuit applications, add adhesive-backed films. Then, before applying photo imaginable liquid and film polymers that act as a solder mask and protect the circuits from both internal and external damage, apply screen-printable liquid overcoats.

Types of Flexible PCBs:

There are four different types of flexible printed circuit boards.

  1. Flexible Single-Layer PCB

As the name implies, a single-layer flexible PCB has only one conductive layer that rests on top of the flexible dielectric film. Only one side of the PCB is occupied by electric components.

Flexible Double-Layer PCB The conductive layer on both sides of the double-layer flexible PCB allows you to connect electrical components on either side of the conductive layer.

  1. Flexible PCB with Multiple Layers

Three or more conductive layers are separated by a dielectric substance on the multi-layer flexible PCB. The uneven lamination enables great board flexibility, and the bonding area often has a thinner lamination.

  1. PCB with Rigid-Flex

The rigid-flex PCB is a hybrid circuit board that combines stiff and flexible circuit boards to provide greater component density than standard circuit boards.

  1. Flexible PCB from HDI

High-density interconnects (HDI) is the abbreviation for high-density interconnect. Compared to other boards, these circuit designs are more efficient, dependable, and have better design, construction, and layout. Because of the thinner substrate material utilized in the fabrication of HDI flexible boards, they have higher electrical performance and smaller package sizes.


Flexible boards can be bent into any shape, which is why they are widely utilized for dynamic flexing and static applications in today’s world. Circuit boards for dynamic applications are designed for regular flexing, whereas circuit boards for static applications are designed for minimal flexing.

Flexible circuit designs are designed to endure extreme temperatures ranging from -200° C to 400° C, making them ideal for borehole measurements in the oil and gas industry.

Flexible circuit boards are useful in a variety of applications, but they cannot be used in place of rigid circuit boards. Because rigid boards are inexpensive and may be used in high-volume automated fabrication applications, they are widely used.

Flexible circuit boards are ideal for applications that demand increased performance, high accuracy, precision, and regular flexing. Applications of flexible circuit boards include:

  1. Cameras
  2. Antilock brakes
  3. Fuel pumps
  4. Ultrasound probes
  5. Semiconductor test
  6. Medical devices
  7. Motion systems
  8. Satellites
  9. Avionics
  10. Battery packs
  11. Manufacturing devices
  12. Airbag apparatus
  13. Bar code equipment

Circuits that are flexible or can flex are referred to as flex circuits. Flexible circuits are made up of a thin insulating polymer film glued to a substrate with a pattern of conductive traces. Flex circuits have been in use since World War II, and their applications are continuously expanding at a rapid pace.

Flex Circuit Sorts: There are many different types of flex circuits, and we’ll go through the most common ones here.

1: Flex on one side only: The most basic flex circuits are single-sided flex circuits, which have a single layer of metal traces on one side of a dielectric layer. Polyimide or polymer can be used as the dielectric. Insulation and protection from environmental degradation are provided via a polyimide overlay.


  1. Low cost to acquire.
  2. Minimized interconnect errors.
  3. Clean system appearance.
  4. Ability to reduce packaging size.


A double-sided flex circuit consists of numerous layers on both sides of a single dielectric layer. To build linkages between the two layers, metalized through-holes are plated.


Have small human errors compared to hand-built wire harnesses?

  1. The circuit boards can be mounted for all types of components.
  2. Have a small footprint which is highly applied in lightweight electronics due to its flexibility and elasticity.
  3. It is ideal for certain occasions i.e.
  • Has complex connections.
  • Hostile environments.
  • Power plane and ground operations.
  • Shielding applications.



Multi-Layer Flex: Multi-Layer flex circuits are made up of multiple copper layers separated by dielectric layers. Through holes join the metal layers once more. Layer design surface mounting has more complicated linkages.



Rigid-Flex Circuits: Rigid-flex circuits are made up of many circuit layers that are joined by an epoxy pre-preg bonding film, similar to a multi-layer flex circuit. Rigid circuit boards and flex circuits are essentially interchangeable in flex circuits. Component density is higher in rigid-flex circuits.



The Basic Materials Utilized in Flex Circuits: Now we’ll talk about the basic materials that are used in flex circuits.

  • Conductors: Conductors allow for the free movement of electrical electricity. Copper is the most frequent conductor, but other materials like aluminum, carbon, and silver ink are also utilized.
  • Adhesives: Surface mount component binding is done via adhesives. Adhesives are chosen based on the needs of the customer and the thickness of the conductor. Epoxy, acrylic, and PSAs are some of the adhesives that are employed (Pressure Sensitive Adhesives). Some circuits are constructed without the use of adhesives.
  • Insulators: Insulators are used to keep electrical conductors apart without conducting current. They can also be utilized as a source of support. Polyimide, polyester, solder mask, polyethylene naphthalene, and polyethylene terephthalate are all common insulators.
  • Finishes: Finishes are applied to metal surfaces to prevent oxidation. The final result is determined by how the circuit is used. Solder, tin, immersion in nickel or gold, silver, carbon, and other typical finishes are only a few examples.

Flex Circuits’ Advantages:

Flex circuits provide several advantages that make them more useful than standard cables and rigid boards.

  • Because the design is precise and the production is entirely automated, there is a significant reduction in assembly errors.
  • They require less work and have fewer manufacturing faults. There is also a reduction in the time and cost of assembly.
  • Flex circuits can be created in a variety of ways to accommodate a variety of complex layouts.
  • They are lighter hence take less room.
  • The flexible quality of the material also aids in reducing and absorbing the effects of any vibration.
  • They can be used in a variety of difficult situations. The thinner flex circuits also allow for more heat to pass through.
  • Mechanical connectors are used sparingly. There are also fewer connecting points, indicating that the system is more reliable.
  • Rigid circuit boards have fewer pieces and interconnections than flexible circuit boards. Complex arrangements with fewer interconnections can also be used to create rigid circuits.
  • Rigid-flex circuits have also been shown to be denser, with lighter components, allowing for more functionalities.
  • Flex Circuit Applications: There are two fundamental categories of flex circuit applications:
  • Static Application:
  • Dynamic Flexing Application: When the flex circuit is bent several times as part of the final product’s application, it’s called dynamic flexing.

Most of the electronics are made of flex circuits.

They’re utilized in automation, processing machines, and bar code scanners, among other things. Satellites and GPS systems use them as well. Flex circuits have an almost limitless number of uses.


PCBgogo is a company that specializes in producing high-quality PCBs (Printed Circuit Boards) at a low cost. These boards are made in order to meet your specific requirements.

Data communication, optical networking, medicinal treatment, industrial control, aerospace/military, and so on are only a few of these sectors.

The flexible circuit board is meant to save space and increase flexibility to satisfy a smaller and greater density mounting design. In a nutshell, FPC is the only way to assure that electrical items can be miniaturized and moved.

The flexible printed circuit is either an etched copper circuit with a polymer substrate or a polymer thick film circuit. Solutions range from a single conductive line to a complicated layered 3D package for both thin and light, compact structure, and complex electronics. Flexible packages have lower overall quality and volume than standard wire harnesses by 70%. Reinforcement can also improve the flexibility of a flexible circuit.

Different contours and special packaging sizes are allowed on the flexible PCB, which may be moved, bent, and torsion without damaging the conductor. The volume is the only constraint. A flexible circuit can be used in the periodic motion of the internal connection system and become part of the end product’s function since it can endure millions of dynamic bending. Flexible circuits benefit products that require electrical signal/power transfer and have a modest shape coefficient/package size.

The electric performance of flexible circuit boards is good. Low dielectric constant allows for electrical signal transmission; superior thermal properties allow for simpler cooling of components, and a higher glass transition temperature or melting point allows components to operate at high temperatures.

Flex circuits can give improved assembly reliability and output due to reduced hardware for internal connections, such as common solder points used for standard electronic packages, trunk lines, bottom lines, and cables. While assembling, higher component dislocation appeared to be easier. Because standard linking hardware is made up of numerous complex systems. With quality engineering, a thin flexible system is intended for only one-way assembly, eliminating human error associated with standard and independent routing activities.

To put it briefly,

  • Flexing for easier installation and repair • Reduced weight and space • Dynamic flexing requirements
  • Improve repeatability and dependability
  • Controlling the temperature
  • Enhance the appearance
  • Dismantle all the connections
  • Ensure that high-speed circuitry has consistent electrical characteristics.
  • Lower the cost of assembly
  • 7 Tips for Creating a High-Quality PCB

The seven important points that an EE or a newbie should remember if they want to create high-quality PCBs for their electronic applications are listed below.

  1. Material to make the board: In any of the PCB designs, this is the first step to start with. You need to know the resources for making a PCB.
  • A printed circuit board (PCB) is made out of a non-conductive and solid material that has been laminated with copper. Copper plating aids in the creation of a conductive surface. The foundation material is commonly FR-4, which is a glass-reinforced epoxy. This material is both cost-effective and flame-resistant.
  • PTFE or ceramic bases: combined with various fillers are employed in RF or high-performance circuits.
  1. PCB stack-up: The number of layers on each PCB is referred to as the PCB stack-up. It enables an EE to comprehend each layer’s required impedance. Appropriate layer count estimation allows the engineer to choose the best fabrication procedure to achieve the desired yield, reliability, and production cost savings.
  1. Copper Traces: The copper traces on a PCB are the most crucial components. While designing them, it is critical to grasp their properties as well as their limitations. Copper traces are commonly made by extracting copper from a solid metal sheet that has been laid on top of the base material.
  2. VIAs: are small drilled hole that goes through two or more adjacent layers, the hole is plated with copper that forms an electrical connection through the insulation that separates the copper layers.

The types of VIAs include: Buried, Through, Blind and Micro.

  1. Selection of parts: It is the most tiresome step in any PCB design work. Choosing the right part will help to minimize the number of errors and ensure the high quality of the designed PCB. For you to produce the best PCB in the market, you need to keep the following in mind:
  • Selection of the widely used part which is readily available and is no more in the market.
  • Some of the parts are sold in large numbers you have to be aware of when selecting them for use.
  • All elements are offered in a package that is attached to the PCBs. Some of the parts are available in a number of packages which may make them compatible.
  • Some parts are sold in bulk, so keep that in mind while choosing them for your project.
  • All components come in a package that makes it easier for us to attach them to the PCB. Some parts are available in various packages, making them potentially interchangeable.
  1. Design Guidelines: An EE should focus on the design rules after addressing all of the preceding requirements. Cross-talk budgets, component placements, layer allocations, time of flight analysis, Design for Manufacture (DFM) standards, and other factors should all be taken into account.
  2. Signal and Power Integrity: This is one of the positive elements of a solid PCB. Signal fall and rise times, drive strength, track lengths, and characteristic impedance are all things to think about. Signal-integrity (SI) simulations will be run before and after the layout to guarantee that the quality is maintained.

Large currents are required for high-performance electronic circuits. As a result, the power distribution network’s AC and DC performance should be evaluated.

The preceding list is a nice place to start for both seasoned and inexperienced EEs. We’ll go over some of these aspects in more detail in future blogs, as well as walk you through various PCB assembly jobs.

Fabrication of Circuit Boards

Jumping right into fabrication without understanding the relationships and procedures between the schematic or idea you have in mind and getting that idea manufactured might not be a good idea. It may be helpful to define a few other words and their interrelationships before defining PCB manufacture.

  • Development of PCBs: The process of moving a circuit board design from concept to production is known as PCB development. There are usually three stages to this: design, manufacture, and testing. And, except for the simplest designs, this approach is iterative, intending to achieve the greatest quality design in the time allocated for development
  • PCB Manufacturing: The building of your board design is known as PCB manufacturing. This is a two-step process that starts with the manufacture of the board and finishes with the assembling of the printed circuit board (PCBA).
  • PCB Testing: Following manufacturing, PCB testing, also known as bringing up, is the third stage of PCB development. During development, testing is carried out to assess the board’s capacity to perform its planned operating functions. Any mistakes or locations where the design should be adjusted to increase performance are detected during this step, and a new cycle is started to include the design changes.
  • PCB Assembly: PCB assembly, also known as PCBA, is the second step or stage of PCB manufacture, during which the board components are soldered to the bare board.


PCB Development Stages

Advantages and downsides of PCBs

(PCB) Printed Circuit Board. This circuit board is an essential component of modern electrical devices. A printed circuit board should contain a certain number of active and passive parts. Traces/ findings on the board connect the component from one side to another. With the advent of very small-sized electronic components, it is entirely possible to create very massive circuits on small printed circuit boards.

To know more about the printed circuit board, the following are the benefits and drawbacks.

PCB Drawbacks include:

  1. Uneven PCB surface finishes.
  2. It is not a good choice for fine-pitch.
  3. It’s made of lead.
  4. Once injured, it is difficult to repair.
  5. It can be applied in a certain circuit.
  6. Once printed, we can’t be changed.
  7. Reduced or plugged in
  8. One sort of circuit operation necessitates reworking.
  9. Harmful chemicals are produced during the etching process, which pollutes the environment.

Advantages of PCBs:

  1. PCBs are inexpensive, allowing for mass production at a cheaper cost.
  2. Changes can be made.
  3. The product is found all over
  4. Shelf life is excellent.
  5. Smaller in size and less wire is used


The flexible PCB designs are reliable as they come with few solder joints and contact crimps. The circuit requires less space due to its flexibility.