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What are the materials features of flexible PCB?
84 0 Aug 11.2022, 17:13:35

Electronic circuit boards have gained momentum in terms of materials used in fabrication. The types of PCBs in the market are backed up by various high-performing buildup materials. In this article, we are going to focus on flexible printed circuit boards and the material used to build their structures.

A flexible printed circuit board is a PCB that is made up of a flexible insulating substrate. They are boards that are accompanied ban excellent electrical performance together with high assembly density characteristics, minimal thickness, and lightweight. They have found great applications in the area of digital cameras, mobile phones, LCM, aerospace products, and mobile phones.


                                                The flexible PCB by PCBgogo

The flexible circuit board’s materials



This material is mostly used as a cover and base film. It has high-temperature resistance features which can be reinforced through welding. It is the most used material and the price increases with thickness.


This is used in the manufacturing of flexible boards when the high temperatures are not conditions for their manufacturing. They have better dimensional stability and moisture absorption in the best way than the PI. The PET is also colorless, which is not the case with PI.

PET is used generally as a base film but can also be used to reinforce the PCBs.

Comparison between the P1 and PET


This is a product of DuPont under the Teflon trademark. This type of insulator has the following characteristics;

· Chemical inertness; the material cannot be dissolved by almost all the strong bases, strong acids, strong organic solvents, and strong oxidants. In other words, they are referred to as “Plastic King”

· Excellent electrical conductivity properties; this is the top insulator among all known plastics with a volume resistance of up to 1018?-cm. It has the best electrical performance with a dielectric constant of 2.1 and minimal temperature and frequency effects.

· Thermal stability; high melting point of 327 ?C and it has a temperature stability range of about -200 to 260 ?C.

· Flammability; it has a limiting oxygen index of about 95%.

· Non-sticky; no viscous substance can adhere to this material. The contact angle of water is about 114?.

· Good weather resistance; this material can survive outdoors for over 20 years while retaining its mechanical properties.

The PTFE is used in the fabrication of the flexible copper-clad laminate which finds use in its excellent dielectric properties. The organic features in the material are good for speeding up signal processing.

Flexible PCB fabrication materials and procedures to improve terminal performance

Flexible PCB has many uses in the product, but basically, it is no more than a lead line, printed circuit, connector, and multi-functional integrated system. If the function is distinguished by space design, changing its shape, folding, and flexing design assembly, the Flexible PCB design can be used to prevent electrostatic interference problems in electronic equipment. The use of flexible circuit boards, regardless of cost, so that the quality of products directly on the soft board structure, not only the design volume is relatively small, but the overall product size can also be significantly reduced due to the characteristics of the board.

Flexible PCB substrate structure is quite simple, mainly by the upper protective layer, the middle of the wiring layer, in mass production of soft point circuit board with positioning holes for production procedures and post-processing. As for the use of flexible PCB, according to the space required to change the board shape, or folded form of use, and multi-layer structure as long as the outer layer of anti-EMI, electrostatic barrier design form, the flexible circuit board can also achieve efficient EMI problems to improve the design.

The key circuit board, the uppermost layer of the flexible PCB structure for copper, there are divided into RA (Rolled Annealed Copper, hot-rolled annealed copper), ED (Electro Deposited, electrodeposition), and ED copper manufacturing costs are quite low, but the material will be easier to fracture or fracture. RA (Rolled Annealed Copper) production costs are higher, but its flexibility performance is better, so in the high flexural state of the application of flexible circuit boards, most of the RA material.

As for the flexible PCB to form, it is necessary to bond through the adhesive to different layers of the cover layer, calendering copper, substrate, the general use of the adhesive (Adhesive) acrylic (Acrylic), epoxy resin (Mo Epoxy) two main categories, epoxy resin heat resistance is lower than acrylic, mainly for household products, while acrylic although high heat resistance, high strength advantages, but its poor insulation, and in the flexible PCB production structure, the thickness of the adhesive accounts for the overall thickness of 20 ~ 40μm (micron).

Limitations of the Flexible PCB

· High initial cost; The board is manufactured for special use, and the cost of the photographic plate and circuit design are relatively higher. Unless it is a must and special to use the flexible PCBs it is advisable not to use them in small-scale applications.

· Flexible printed circuit boards are very difficult to replace and fix.

· They have a limited size; The process of manufacturing is called batch process hence they cannot be made much longer and wider due to the production equipment size.

· When operated improperly, they get damaged easily; trained personnel is required to operate and solder this board.

For highly flexural applications, reinforcement and integrated design are available to improve material performance

In the flexible PCB process, the copper foil and substrate production, cut off processing and then take the perforation, plating operations, roughly in the flexible PCB hole pre-finished, the photoresist material coating process, the coating is completed that the flexible PCB exposure development process, the preparation of etched lines for processing in advance, after completing the exposure development process that solvent etching operations, at this time etching to a certain extent so that the conductive lines take shape, is to clean the surface to remove the solvent, this time for the use of adhesives evenly coated on the flexible PCB base and etched copper foil surface, and then for the adhesion process of the cover layer.

After completing the above operations, the flexible PCB has roughly 80% completion, at this time we still need to deal with the connection point of the flexible PCB, such as increasing the hole guide welding processing, then the flexible PCB shape processing, such as the use of laser cutting specific shape, if the flexible PCB is a soft and hard composite board, or need to be soldered with the functional module processing, at this time and then the secondary processing, or with the reinforcement board processing design.

flexible PCB's use is quite diverse, and the production difficulty is not high, only flexible PCB itself can not produce too complex, tight lines, because the too fine circuit will be too small because of the cross-sectional area of copper foil, if the PCB flex, it is easy to make the internal lines break, so too complex circuits will mostly use the core HDI high-density multilayer board to handle the relevant circuit needs, only a large number of data transmission interface, or different functions of the carrier board data I/O transmission connection, will use flexible PCB to connect the board.

Flex-rigid PCB manufactuered by PCBgogo


The flexible circuit boards are manufactured by involving so many materials so that we can be able to achieve the flexibility that the board has. The above fore-mentioned material should be used as discussed. The PCBgogo manufacturers can fabricate such boards for you. The modern facilities that the company have has the benefit of delivering satisfactory outcomes to its customers.

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