What are the advantages, disadvantages and development trends of FPC flexible boards? Seek circuit analysis from PCB MASTER COMPANY.
The FPC flexible printed circuit board, also known as "flexible board" in Chinese, with its English name "Flexible Printed Circuit", is a highly reliable and excellently flexible printed circuit board made of flexible insulating base materials such as polyimide or polyester film. It features high wiring density, light weight, thin thickness and good flexibility. Flexible printed circuit boards can also be divided into single-sided, double-sided and multi-layer boards. Flexible printed circuit boards are mainly applied to the connection parts of electronic products.
Its advantages are as follows: All circuits can be configured completely. It saves the connection work of redundant flat cables, which can improve the flexibility. It enables the assembly in three-dimensional space within a limited space, effectively reducing the volume of the product. It increases the convenience of carrying and can also reduce the weight of the final product.
Characteristics of FPC:
1. Short assembly time: All circuits are configured completely, eliminating the connection work of redundant flat cables.
2. Smaller in volume than PCB: It can effectively reduce the product volume and increase the convenience of carrying.
3. Lighter in weight than rigid PCB: It can reduce the weight of the final product.
4. Thinner than PCB: It can improve flexibility and enhance the assembly in three-dimensional space within a limited space.
Advantages of FPC:
The flexible printed circuit board is a printed circuit board made of flexible insulating base materials and has many advantages that rigid printed circuit boards do not possess:
1. It can be freely bent, wound, folded, arranged arbitrarily according to the requirements of spatial layout, and moved and stretched freely in three-dimensional space, thus achieving the integration of component assembly and wire connection.
2. The use of FPC can greatly reduce the volume and weight of electronic products, meeting the needs of the development of electronic products towards high density, miniaturization, and high reliability. Therefore, FPC has been widely used in fields or products such as aerospace, military, mobile communications, laptop computers, computer peripherals, PDAs, digital cameras and so on.
3. FPC also has the advantages of good heat dissipation and solderability, being easy to assemble and connect, and having a relatively low comprehensive cost. The design combining rigidity and flexibility also makes up to some extent for the slight deficiency of flexible base materials in component carrying capacity.
Disadvantages of FPC:
1. High one-time initial cost: Since flexible PCBs are designed and manufactured for special applications, the costs required for the initial circuit design, wiring, and photographic negatives are relatively high. Unless there is a special need to use soft PCBs, it is usually advisable not to adopt them when the application quantity is small.
2. It is relatively difficult to make changes and repairs to soft PCBs: Once a flexible PCB is manufactured, any changes must start from the original drawing or the compiled photoplotting program, so it is not easy to make changes. There is a protective film covering its surface, which needs to be removed before repair and restored after repair, and this is a rather difficult task.
3. Size limitation: In the case where soft PCBs are not yet widely used, they are usually manufactured by the intermittent process, so they are limited by the size of the production equipment and cannot be made very long or wide.
4. Prone to damage due to improper operation: Improper operation by assembly personnel can easily cause damage to soft circuits. Soldering and rework of soft PCBs require trained personnel to operate.
All electronic products need to use PCBs, and the market trend of PCB circuit boards is almost a barometer of the electronics industry. With the development of high-end and miniaturized electronic products such as mobile phones, laptop computers, and PDAs, the demand for flexible PCBs (FPCs) is increasing. PCB manufacturers are accelerating the development of FPCs that are thinner, lighter, and have higher wiring densities. A single-layer FPC has a conductive pattern chemically etched on it, and the conductive pattern layer on the surface of the flexible insulating substrate is rolled copper foil. The insulating substrate can be polyimide, polyethylene terephthalate, aramid fiber ester, or polyvinyl chloride.
Single-layer FPCs can be further divided into the following four sub-categories:
1.1Layer connection without a cover layer: The conductor pattern is on the insulating substrate, and there is no cover layer on the surface of the conductors. The interconnection is achieved by soldering, fusion welding, or pressure welding, and it is commonly used in early telephones.
2. 1Layer connection with a cover layer: Compared with the previous type, there is just an additional cover layer on the surface of the conductors. When covering, the solder pads need to be exposed. For simplicity, the end regions can be left uncovered. It is the most widely used type among single-sided soft PCBs and is used in automotive instruments and electronic instruments.
3. 2 Layer connection without a cover layer: The connection pad interfaces can be connected on both the front and back sides of the conductors. A via hole is opened in the insulating substrate at the solder pad position. This via hole can be formed by punching, etching, or other mechanical methods at the required position on the insulating substrate.
4. 2 Layer connection with a cover layer: Different from the previous type, there is a cover layer on the surface. The cover layer has via holes, allowing both sides to be terminated while still maintaining the cover layer. It is made of two layers of insulating materials and one layer of metal conductor.
2Layer FPC has a layer of conductive patterns formed by etching on each side of the insulating base film, which increases the wiring density per unit area. Metallized holes connect the patterns on both sides of the insulating material to form conductive paths so as to meet the design and functional requirements for flexibility. And the cover film can protect the single-sided and double-sided conductors and indicate the placement positions of components. Depending on requirements, metallized holes and cover layers may or may not be present. This type of FPC is less commonly used.
Multilayer FPC laminates three or more layers of single-sided or double-sided flexible circuit layers together. Through drilling and electroplating, metallized holes are formed to create conductive paths between different layers. In this way, there is no need to adopt complex welding processes. Multilayer circuits have significant functional differences in terms of higher reliability, better heat conduction, and more convenient assembly performance.
Its advantages are that the base film is lightweight and has excellent electrical properties, such as a low dielectric constant. The multilayer soft PCB circuit board made of polyimide film as the base material is approximately one-third lighter than the rigid epoxy glass cloth multilayer PCB board. However, it loses the excellent flexibility of single-sided and double-sided soft PCBs. Most of such products do not require flexibility.
Multilayer FPC can be further divided into the following types:
1. Finished Products with Flexible Insulating Substrates: This type is manufactured on flexible insulating substrates, and the finished products are specified to be flexible. This structure usually involves bonding the two ends of many single-sided or double-sided microstrip flexible PCBs together, while the central parts are not bonded together, thus achieving high flexibility. To obtain high flexibility, a thin and suitable coating, such as polyimide, can be used on the conductor layer instead of a thick laminated cover layer.
2. Finished Products with Soft Insulating Substrates: This type is manufactured on soft insulating substrates, and the finished products are not specified to be flexible. This kind of multilayer FPC is made by laminating soft insulating materials, such as polyimide films, into multilayer boards, losing their inherent flexibility after lamination.
Analysis of the Market Prospects and Prediction of the Development Trends of China's FPC (Flexible Printed Circuit) Industry in Recent Years
In the future, FPC needs to continuously innovate in four aspects, mainly including:
1. Thickness: The thickness of FPC must be more flexible and thinner. PCBMASTER Company has already developed 0.08mm single-sided FPC and 0.08mm double-sided FPC flexible printed circuit boards. Once the 0.08mm ultra-thin FPC circuit boards were launched, they received multiple orders from customers.
2. Foldability: The ability to be bent is an inherent characteristic of FPC. In the future, the foldability of FPC must be stronger and able to withstand more than 10,000 bends. Of course, this requires better base materials.
3. Price: At present, the price of FPC is much higher than that of PCB. If the price of FPC can be reduced, the market will surely become much broader.
4. Technological Level: To meet various requirements, the manufacturing technology of FPC must be upgraded, and the minimum hole diameter, minimum line width/line spacing must meet higher standards.
PCB MASTER Company (www.pcbmaster.com) is a professional manufacturer specializing in the research, development and production of high-precision PCB circuit boards. It can mass-produce 4 - 60 layer PCB boards, circuit boards, printed circuit boards, high-frequency boards, high-speed boards, HDI boards, PCB printed circuit boards, high-frequency and high-speed boards, double-sided and multi-layer printed circuit boards, HDI circuit boards, mixed-pressure circuit boards, high-frequency circuit boards, and rigid-flex circuit boards.
This article is provided by PCB board ---- circuit board ---- circuit board factory PCB MASTER company (www.pcbmaster.com)