What Is Flexible Copper Clad Laminate?

A PCB is made up of different materials based on the requirement and device it will be used on. For instance, manufacturers will use FCCL or flexible Copper-clad laminate to make flexible PCBs. The use of this material has gained a significant amount of popularity, which is why we have provided you with a full read about FCCL, its uses, benefits, and every other essential information.

What Is A Flexible Copper Clad Laminate?

Flexible Copper-clad laminate is the sub-section of the Flexible PCBs. These categories are made by considering the mechanical rigidity of copper-clad laminates. Other than the FCCL, there is another alternative called RCCL, or rigid Copper-clad laminate. 

FCCL is the base laminate of the Flexible PCB. As part of the primary material, FCCL plays a major in the flexibility of the product and other functions. Also, FCCL consists of layers of copper foil and polyimide, which are used as an electrical conductor and insulator for the PCB.

How Does Copper Clad Laminate Stack-Ups?

FCCL are copper foils laminated at the top of the polyimide film. Moreover, the combination of copper sheets and polyimide acts as the insulator for the substrate. These thin copper sheets serve as the electrical conductor at the surface level. 

Categories Of FCCL PCBs

The FCCL PCB are categorized into the following:

• Single-sided.
• Multisided FCCL PCBs.
• Double-sided PCBs.

These categories are based on the board’s number of sides and the tracing’s density.

Structures Of The Flexible Copper Clad Laminate PCBs.

The FCCL PCBs are also classified, divided, or grouped into several sub-categories; these categories are based on the product’s structure. The categories are divided by FCCL with adhesives and FCCL without adhesives. 

FCCL is used for PCB fabrication, whether non-adhesive or adhesive FCCL is used. The adhesive of FCCL is called 3L-FCCL, whereas FCCL without adhesive is called 2L-FCCL.

Difference Between Non-Adhesive and Adhesive FCCL

The primary difference between Adhesive and non-adhesive FCCL is that the adhesive FCCL is laminated in between the PI (polyimide film) and Copper, whereas the non-adhesive is not.

Another major difference is that the non-adhesive FCCL is more costly than the FCCL adhesive. In regards to applications and production capabilities, there are major differences between them based on the manufacturing requirements. Whereas the FCCL with adhesive is best for producing the following types of flexible PCBs:

• Single-sided FPCB.
• Simple Flexible Keyboards.
• Double-sided FPCB.

The non-adhesive FCCL is best for producing the following flexible PCBs:

• Multilayer circuit boards.
• High-density SMDs.
• High-density interconnect PCBs.
• Impedance-controlled PCBs.
• Rigid-flexible circuit boards.

Things To Know About FCCL PCBs

Before choosing the FCCL materials or lamination, you must consider the following:

• Desired Thickness

You will need a strictly controlled impedance and thickness of the PCB laminates. Due to this, you may have to combine the varying thicknesses of the following products:

• Adhesive.
• FCCL.
• Coverlay.

Keep in mind that this combination is generally needed for special uses of the PCB.

• The FCCL Copper Pouring Design

The copper pour is the term given to the cross-hatched or the solid area on the bare PCB filled with Copper.

The following are the reasons for copper pour:

• Enhancing the flexible bending features of the FPCB.
• Reduce the amount of etching materials needed for the production of PCBs.
• FCCL is also used for making the connections on the PCBs.

There are several Copper pours, such as hatching pour, cross-hatching, and solid copper pour.

Different Types Of The Copper Pour

The sole purpose of the copper pour is to enhance the bending ability of the PCB while reducing the etched materials, which will improve connections. Other than that, there are several types of Copper pouring methods for different purposes. 

The following section teaches how you can learn the difference between different pour processes:

• Solid Copper Pour

PCB designers commonly use solid copper areas as the base layer that can cover the outstanding areas on the stand-off regions, such as the pads and traces.

• Cross-Hatched Copper Pour

This type of copper pour helps to balance the heat and dilation on both sides of the PCB. It can go a long way to avoid the warping of the PCB substrates.

• Hatched Copper Pour

Amongst the different functions of copper pouring, this type supports the impedance adjustment of the high-frequency traces. It is highly helpful for enhancing the impedance capabilities.

Bending Capabilities

One of the unique features of FCCL is enhanced bending. The primary material is copper foil lamination onto the Polyimide film. It can support the idea of the required design of the product with emphasis on the folding, sliding, and bending attributes.

Regardless of the foldability and bendability of the Flexible PCBs, the flexible Copper laminate has some level of discrepancies. One major example of this is the thickness of FCCL, and the non-adhesive FCCL has better bending than the adhesive FCCL.

Flexible PCB is used in a wide range of industries due to its unique physical bending capabilities and extension that allows PCB to be fitted into electronic devices. The flexibility of the PCB is determined by the copper thickness, overlay thickness, adhesive thickness, and Kapton thickness. 

What Are The Features Of Adhesiveless FCCL?

There are many reasons why many FPCB manufacturers are opting for the non-adhesive FCCL due to its remarkable features:

• Heat Resistance

Since non-adhesive has remarkable heat resistance, it leads to better bonding between the tear strength of soft materials. Another good thing about heat resistance is that the non-adhesive FCCL is not damaged when put at high temperatures for a long time. 

• Chemical Resistance

The non-adhesive FCCL has several beneficial chemical resistance properties. Moreover, the tear strength does not change. However, the 3-layer rubber flexible boards have bad chemical resistance because of the adhesive, and the tear strength varies. Another feature of non-adhesive FCCL is that it can reduce the substrate’s thickness in thinness, lightness, and shortness.

What Are The Benefits Of Using Flexible Copper Clad Laminate PCB?

Following are the benefits you can by using FCCL PCB:

• Flexibility: One of the obvious benefits of using FCCL PCB is that the flexible materials can be twisted and bent to the required sizes and shapes. This flexibility makes them the best choice for devices when the traditional PCBs are not beneficial.
• Lightweight: FCCL PCBs are lighter than the traditional PCB. It is highly beneficial for places where weight is vital, such as portable customer devices and aerospace.
• Durability: One of the major benefits of using FCCL PCBs is that they can withstand repeated flex and bending without affecting the circuitry’s integrity.
• Space-savings: Several industries use this type of PCB for devices with compact and less space as these PCBs can easily fit around the components. 
• Less Mechanical Strength: In devices with mechanical stress, such as car electronics, FCCL-printed circuit boards are ideal since they can absorb and distribute stress more efficiently than rigid PCBs.
• Better Signal Integrity: Flexible PCBs provide better signal integrity as they reduce impedance mismatches and signals, which makes them the best for high-speed and high-frequency applications.

Conclusion

Flexible Copper-clad laminate bolsters the flexible bending of the Flex PCBs. To get the best results, you should use non-adhesive and adhesive, as using both simultaneously can affect the performance and results of the electronic devices.