What is FPC Circuit Board?

It’s well known that Printed Circuit board (PCB) plays an important role in the electronics industry. This is because PCB is widely used to perform various roles in devices such as computers, televisions, and power systems. A printed circuit board consists of conductive tracks that interconnect components on the board. They include potentiometers, resistors, capacitors, and switches with various voltage or current levels. They are also commonly used for electrical safety testing or verification.

According to JIS C5017, the Japanese Industrial Standard for measuring the mechanical properties of printed circuit boards, a flexible printed circuit board (FPC) is a PCB with a cylindrical or rectangular shape that can vary in size based on the requirements of its application. The standard divides FPCs into two categories: Rigid and Flexible PCB. Rigid FPCs help mechanically connect components, but cannot bend. A flexible FPC is a double-sided PCB that can withstand bending forces. Also, we mainly use it for electrical interconnection applications.

FPCs are popular with engineers because they are easy to modify and customize without any solder joints. The flexibility of the FPC allows for different retrofit solutions. It significantly reduces the cost of manufacturing new boards for specific applications. For example, it is easier to add functionality to the surface of an existing board than to create an entirely new board from scratch.



Composition of FPC  Materials

The composition of an FPC material depends on its intended application and end use. The flexibility of FPC depends on the material’s ability to resist cracking, warping and mechanical damage while maintaining high electrical conductivity. Therefore, manufacturers tend to use fiberglass or FR-4 materials for FPC flexible printed circuit boards. It consists of a mixture of epoxy resin and fiberglass. FR-4 is a rigid board that combines thermal and electrical properties.

1. Insulating film
It is a layer of high-density polyethylene made by extruding the resin through a nozzle and coating it on the substrate. HDPE films eliminate capacitive coupling between substrates. It also eliminates other circuits to electrically shield the interconnects on top of the board. The HDPE layer also acts as a vapor barrier to prevent moisture from entering the circuit during curing.

2. Electrostatic adhesive layer
After the HDPE film is applied, the adhesive layer can connect the components. These components may include potentiometers and LEDs on the circuit board to improve performance or reduce cost. The adhesive layer is acrylic or polyimide, allowing the LED to be directly bonded to the FPC, saving material and assembly time.

3. Conductor
Then we add a conductive layer on top of the adhesive layer. This layer can be polyimide or epoxy or the printed circuit board itself. To avoid warping, we can apply the conductor to a solution at 100 °C.

Finally, we added a second adhesive layer to the conductors to further reduce bending or cracking issues. We usually use cellulose or acrylic for this layer.

To make an FPC board, components are first pre-assembled onto the board and then cut to size. The FPC material is then put into the mold to bend without breaking. Typically, we heat the FPC material to 120 °C for about 1 hour. This is done to obtain the necessary stiffness so that the material is able to resist the flexors and flex easily. The component is then added to the mold and pressurized to embed it in the FPC.

Next, we apply a layer of conductive ink on top of the component. It helps create a smooth surface that prevents electrical resistance and improves performance.

5. Overlay
The cover layer is a top plate made of polyimide or acrylic. The overlay protects the underside of the FPC material. It also acts as an insulation, preventing moisture from entering the FPC material. The overlay is also high temperature resistant, allowing us to use it in ovens and heaters.



Why do you need to use an FPC circuit board?

We use FPCs in applications that require flexibility and conductivity. But we don’t use it when we need mechanical strength. Since FPCs are thin and light, we use them in portable devices such as cell phones, digital cameras, and walkie-talkies. We can use them in large devices like peripherals and power supplies.

1. Reduce weight and space
Since FPCs don’t have terminals for electrical connectors, we can use them in devices that need to be lightweight but have outputs that connect many components. For example, a portable GPS device can use an FPC to connect a small battery to the host. The main unit has an internal rechargeable battery. However, the GPS receiver also requires power and some other functions, such as the display and buttons. FPC provides all these components and connects them.

2. Easy customization
FPCs are flexible and we can cut them to the required size. Since they are not soldered, they can be easily removed from the board and modified for new uses. You can create entirely new electronics by adding FPCs with add-ons on boards already used for other purposes. For example, we can add an FPC to connect an external battery to an existing product. They include a car radio that adds functionality without completely replacing it.

3. Meet dynamic bending requirements
We mainly use FPCs on portable devices because of their flexibility and light weight. They can be adapted to flexible products such as cell phones, or they can be cut to the size needed for new circuit boards. These properties make them ideal for use in consumer electronics.

4. Bend for easy installation and maintenance
We use FPCs in solar panels, satellites, generators and electric vehicles in homes and buildings. One can easily install solar panels in places where roofing cannot be built or where landscaping is difficult. The flexibility of these FPCs means they can be adapted to many different environments while still providing electrical pathways between various components. We also use FPCs in electric vehicles. This is because they have a lightweight construction while maintaining the required strength to ensure they do not break when driven.

5. Impedance Control
Manufacturers use high-quality materials to make FPCs with high electrical conductivity. Therefore, we also use them in consumer electronics where impedance control is required. The main advantage of using FPC instead of soldered connections is that we can easily control the impedance, which is necessary for mobile devices such as cell phones.

6. Scalability
We need to expand some electronics later, like solar panels or electric cars. This is due to technological advancements or improved user needs. These products can use FPC to connect to various other components that we can add later when new functionality is needed.

7. Improve reliability and repeatability
When we use FPC in solar panels, we weigh the FPC and mechanically test it to be stable after installation. This process ensures that the product operates reliably and smoothly in many different environments.

8. Thermal Management
We can design products that use FPCs with good thermal management. Since we can’t solder the FPC to the motherboard, we can move it and replace it with another one to change its thermal performance. This process ensures that the product is always performing well.

9. Improve aesthetics
We can design the FPC very thin to reduce the size of the final product and make it look very nice. One can achieve this by printing components on film rather than inside the FPC. The manufacturer prints the components on top of the FPC. It still seems to be connected to it while retaining its function and appearance.

10. Eliminate connectors
FPCs do not require connectors as they can be easily removed and reconnected to other boards. With no connectors and terminals, you don’t need to disassemble the product every time you access the cable. You can then reconnect the FPC later, reducing production costs and ensuring products look clean.

11. Reduce assembly costs
In many cases, FPC can reduce assembly costs. For example, semiconductor companies need to add new components to their production lines. We can use FPC with other components to create circuit boards. This increases the functionality of the product while reducing production costs.

12. Increase scalability
FPCs can connect many components to the central board to create larger devices. Because of their flexibility and light weight, we can assemble these boards into large products with high performance features.

13. Provide uniform electrical characteristics for high-speed circuits
Because the company manufactures FPCs using the same high-quality materials and technologies as optical fibers, they provide reliable electrical characteristics for high-speed circuits. Therefore, these circuits can operate at very high speeds without becoming unstable.

14. Improve Signal Integrity
We can design FPCs to improve signal integrity by reducing noise and reflections. They also enhance transmission performance and immunity to electromagnetic interference (EMI).




Flex PCB

The text above shows that FPC is ideal for a variety of applications. Also, we can replace traditional circuit boards. The polyester (PET) and polyimide (PEEK) materials used in FPC are conductive. Therefore, they can be connected to other circuits and components. They also provide mechanical protection for stronger products. The 1-ounce thick Type-V-PET substrate used in FPC is flexible and can carry a lot of current. At the same time it can also withstand high temperature changes. This makes it ideal for high power applications such as solar panels.

level one
We form a “graphic overlay” at this stage. The surface is first cleaned, the screen printed, and then cured to ensure a high-quality printing process with repeatable characteristics. Tier 1 is where most of the modification takes place. We print silkscreen or other overlay patterns. We usually do this in CMYK format, using a high-quality inkjet printer to ensure the sharpest possible image.

Tier 2
The lamination stage includes adding electrical traces. This layer is a conductive adhesive that is laminated with the first layer to form the final FPC product. Adhesives must provide a smooth surface for electrical and mechanical stability. We can do this with vacuum or pressure lamination, depending on how rigid or flexible the final product is.

Tier 3
This is an essential layer as it provides a strong mechanical bond between the first and second layers. One of the most popular binder options is a thin ceramic binder that provides excellent mechanical properties. We can apply this using manual or automated systems to ensure consistent production quality at every location.

Tier 4
The last layer determines the physical look and feel of the FPC. The thickness of this layer can vary depending on various factors. They include material type, application requirements and production location.

We use flexible printed circuits (FPCs) in many different applications, such as solar panels, electric vehicles, and airplanes. Additionally, we use them in new applications such as aerial drones and wearable electronics. Therefore, FPCs must provide reliable electrical characteristics for high-speed circuits. FPC manufacturers use more than 20 different chip types and a wide range of specialized components to create end products.




The difference between PET and FPC

PET is our most commonly used polymer in FPC. PET has low thermal expansion, and it’s also transparent, which means we can use it for solar panels or display panels. On the other hand, FPC can be used flexibly for high-performance displays or indoor use.

A flexible printed circuit board (FPC) is a low-cost flexible circuit board that saves significant shipping space. When we apply PCBs with many components, their size becomes larger. The fabrication and construction of FPCs is made easy due to the flexible key features.

Flexible Printed Circuit Cards (FPCs) combine integrated circuits (ICs) and thin-film printed circuit traces. We use them to make flexible circuit boards. A flexible printed circuit card is an electronic device used to house an integrated circuit (IC).

Flexible Printed Circuits (FPCs) are thin plastic sheets that we can use in applications. Some examples include new applications such as solar panels, electric vehicles, aircraft and aerial drones. We manufacture FPCs from conductive, flexible plastics. A plastic top layer that is etched and printed with various circuits and components. This helps create circuits that are thin enough to be flexible and durable.

Flexible Printed Circuit Cards (FPCs) are helpful in many different applications. They include solar panels, electric cars and airplanes. We also use them in new applications like aerial drones and wearable electronics. Therefore, FPCs must provide reliable electrical characteristics for high-speed circuits.

Trace width advantage
One of the great advantages of FPC technology is maintaining high line widths, thereby increasing performance. This performance improvement is significant for wireless applications. There is a significant difference between the time it takes for a radio signal to travel from one point on a circuit board to another and the time it takes for the signal to be disturbed by noise and interference. Higher line widths can enable greater signal integrity by reducing these delays while increasing data rates and transmission range.

Another benefit of FPC technology is the low dielectric constant (low εr). PET allows for smaller trace widths and higher performance than other materials such as FR-4. Using low εr in FPC traces also reduces line width variation, which improves signal integrity.

Electrical Characteristics
FPC offers several electrical advantages, mainly due to the use of PET. As mentioned earlier, PET is a low-dielectric material, so FPCs using PET can achieve lower line width variations. Reducing linewidth variation improves noise immunity and signal integrity.

FPCs also allow for easy routing, increasing manufacturing yields. Low temperature co-fired ceramics (LTCC) and silica also aid in the FPC process. It provides enhanced thermal performance to the circuit.

The most common FPC manufacturing method is transfer printing. That’s because it involves transferring e-ink onto a surface. Parts of the surface are then etched away to create the circuit. Transfer printing allows very high-speed processing capabilities. We may need circuits that support wireless communication such as WiFi.

manufacturing process
FPC manufacturing is a complex process involving the use of many different materials and processes. We can make FPCs by transferring inks onto flexible substrates. This creates the circuit and removes portions of the substrate to expose the circuit. We then transfer the ink using an ultra-sensitive printer that applies 500-800 g/cm² of pressure.

Inks used in FPC manufacturing include a mixture of photoinitiators and photoresists. This allows high speed propagation. We can print the desired area of ​​the circuit first. We then deposit a thin layer on top of the printed area as an etch mask. The exposed areas are then etched away using oxygen plasma to create the desired circuitry.

The final step in the FPC manufacturing process is to cut the circuit into the proper shape. The circuit must be thin enough to accommodate any movement and thick enough to remain durable and functional. The thickness of FPC is usually between 0.031mm and 0.065mm. However, it can also be as thin as 0.01mm or even thinner for special applications such as wearable electronics.



Applications of Flexible Printed Circuit Boards

FPC has many applications in many different fields. We use FPCs in solar cells, cell phones, vehicles and airplanes. Many of these applications require thin and durable flexible sheets. Therefore, they can withstand bending, folding or rolling.

1. Hybrid Electronics
These are an electronic product that has both organic and inorganic components. Hybrid electronics are useful clothing or building materials with embedded electronics.

2. Wearable Electronics
Wearable electronics include everything from fitness trackers to glasses and other products we wear on our bodies. We have been using FPC for wearable electronics. This is because of their extremely thin, flexible and transparent properties. This makes them great for integrating clothing and other clothing items.

3. Wireless Communication
We have been using FPCs in many different types of wireless communications. They are good because they offer very high speed and low power consumption. They are essential for portable devices such as cell phones, laptops, tablets, smartphones, etc. Many of these products require flexible boards that can be bent without damaging the circuit. Flexible FPC makes these products ultra-thin and durable. They also offer a range of advantages, such as ease of wiring and simplified design.

4. Connector
We use FPC in all our connectors, including low temperature, high temperature and ultra high temperature versions. FPC connectors are also essential for high-speed cables. They include fiber optic cables and micro RF coaxial cables (eg CAT6).

5. Connectors and Housings
FPCs are essential in the connector and housing industry for their versatility and ease of use. Many companies use FPCs to connect many products, including cell phones and other portable devices. Others also use FPCs to house components like LEDs and capacitors.

6. Printed circuit boards
FPCs are essential in printed circuit boards (PCBs). They also work best in circuit sheets printed on flexible substrates, usually made of PET or laminated silica. FPCs are ideal for PCBs because they can withstand high temperatures. They can also be easily integrated into circuit boards and offer excellent flexibility.

7. Portable Equipment
FPCs are suitable for the portable device market due to their thinness and durability. One of the fundamental properties of FPCs for this market is that we can fold, roll or bend them without damaging them.

8. Solar
FPCs are ideal for solar power generation because of their flexibility, thinness and eco-friendly properties. We use them in electronics that convert light into energy. They include solar cells, photoelectrochemical cells, and the like. Flexible, thin and durable, these cells provide high efficiency for solar energy.



What is the cost of FPC?
Most manufacturers and sellers determine FPC pricing based on application type, components, and quantity. For example, a small FPC order for a mobile phone used as a business card, we can price it separately. On the other hand, if we use FPCs in solar cells or aircraft control systems, we can price a larger order with more components into one order. FPC pricing is also affected by product or component type. For example, flexible FPC circuit boards are essential in smaller orders than rigid FPC. This is because they are less expensive to set up and have fewer orders.

F-LGA and L-CUP are two common types of flexible printed circuit boards that are ideal for a variety of applications.

F-LGA is a connector commonly referred to as a micro connector due to its small size. This connector has a unique design to suit the application. They require reliable, low-cost and lightweight connections. F-LGA is a flexible PCB used for high frequency connections in cell phones, pagers, cellular phones, cameras, etc.

The L-CUP is a connector with an LC interface designed for signal transmission between fiber optic cables used in network equipment such as routers, hubs, and switches. The connector has high transmission rates and excellent repeatability. L-CUP is a flexible PCB used in photovoltaic solar cells, medical devices and aerospace equipment.

FPC is a flexible component used in a wide range of applications. Due to the versatility of FPCs, we can use them in many different applications that require high durability and low cost embedded components. This flexibility and capability makes FPC circuits ideal components for many projects, including solar cells and cell phones.




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