Application of FPC flexible circuit board in automotive circuit
According to the flexibility of the substrate, PCB can be divided into rigid PCB (R-PCB), flexible board (FPC), and rigid-flexible PCB. According to the number of layers of the conductive pattern, it can be divided into single-sided PCB, double-sided PCB, and multi-layer PCB. In addition, there are special product classifications, such as high-speed and high-frequency PCBs, high-density connection PCBs (HDI), packaging substrates, etc.
The production process of PCB can be roughly divided into two parts, one is the production of the circuit layer, and the other is to combine, press and reprocess the circuit layer with other layer materials, and finally form FPC.
When the signal transmission line is distributed on the outermost layer of the FPC, in order to avoid signal distortion caused by electromagnetic interference during the signal transmission process, the FPC will press a layer of electromagnetic shielding film after pressing the cover film to shield the external electromagnetic interference, so as to ensure that the FPC circuit can work normally.
FPC application market
In terms of the main downstream application structure of FPC in 2019, smartphones, PCs, other consumer electronics, automobiles, tablets, and servers/data centers accounted for 44.9%, 18.5%, 14.2%, 6.6%, 4.8%, and 4%, respectively. Smartphones have been the main source of downstream demand growth for FPC. As major markets have been saturated since 2018 and the industry has continued to weaken, shipments will rebound slightly in 2021, benefiting from the wave of 5G replacements.
The continuous growth of wearable device shipments has brought continuous growth to FPC products. At present, there is still a large room for development of FPC products in the wearable device market. It is expected that with the further expansion of the wearable device market, the FPC market will also further expand.
In the automotive field, the current automotive FPC market size is less than 10 billion RMB. Compared with traditional wire harnesses, FPC integration has high production efficiency and high dimensional accuracy, and is suitable for large-scale mass production. At the same time, in terms of technology, the FPC wiring harness solution has many advantages such as high integration, automatic assembly, assembly accuracy, ultra-thin thickness, ultra-softness, and lightweight.
Taking lithium iron phosphate battery as an example, multiple cells need to be filled in the battery pack, and FPC is used for collection between the cells. The improved 590 module contains 16 batteries, and a total of two FPCs are used. In the long module based on double-row batteries, the number of batteries can reach 32, and the number of FPCs used will double.
FPC lightweight is the main direction of future automotive wiring harness development
The automobile wiring harness is the main body of the automobile circuit network. It is mainly composed of wires, terminals, connectors and sheaths. Automotive wiring harness products are customized products, and different vehicle manufacturers and different models have different design schemes and quality standards.
FPC is a printed circuit board made of flexible insulating substrates. Compared with rigid boards, it has many advantages, such as high wiring density, light and thin, free bending, and three-dimensional assembly.
Therefore, it has obvious advantages in product shape design and reliability design, suitable for miniaturized and thinned electronic products. In line with the development trend of intelligent and portable electronic products in the downstream industry, it is widely used in consumer electronics such as smartphones, tablet computers, wearable devices, automotive electronics, communications and other fields.
The automotive manufacturing industry has witnessed the highest deployment of robotic automation. Welding, assembly, machine maintenance, material removal, part transfer, etc. are the assembly operations that are best suited for robotic automation. However, for tasks that require judgment and decision-making, there is still room for improvement in the performance of robots.
The wiring harness is the nervous system of a car, consisting of wire and connector assemblies of many sizes and shapes. The wiring harness carries various control and power signals between the main control unit, the battery, and various components of the car. Assembling such cables with connectors requires a high level of skill and is the most time-consuming. It involves mating the cables with the appropriate connectors and securing the complex wiring structures inside the car.
Traditionally, it has been difficult for robots to install wiring harnesses on car bodies. Therefore, in order to simplify the complex problems related to wire harnesses, various methods are being adopted to simplify wire harness architecture and improve the function of robots. The goal of simplifying wire harness manufacturing requires a persistent push for automation, wire harness automation.
Lightweight is the nervous system of its development. As an important part of the vehicle, the automotive wiring harness accounts for 2% of the total weight of the vehicle. And as the increase of automotive electronic equipment continues to expand, the lightweight of wiring harnesses is becoming more and more important to reduce the energy consumption of single vehicles. The weight of copper wires in automotive wiring harnesses accounts for 75%, which is the main lightweight direction.
FPC flexible flat wire harness
Facing the rapid development of automobile electrification, intelligence, and networking, the design strategy of automobile wiring harness system is low-carbon and energy saving, light weight and small size, and intelligent integration.
FPC flexible flat wire harness has the characteristics of small size, light weight, and soft structure. It is suitable for wiring harnesses in small spaces, such as car roofs, doors, lights and other areas. A car uses FPC flexible flat wire harness to replace the traditional wire harness, the overall weight of the wire harness is reduced by about 50%, and the volume is reduced by about 60%.
In addition, the integration of electronic modules, switches and FPC harnesses can reduce the use of connectors and accessories and reduce costs. Therefore, the application of FPC wiring harness can better optimize space, reduce energy consumption, and realize green travel of the whole vehicle. At present, FPC has begun to be widely used in new energy vehicles to replace traditional battery sampling lines.
Global automotive wiring harness market
The global automotive wiring harness market is expected to reach a value of USD 91.53 billion by 2025. Due to the market-oriented trend, major wiring harness manufacturers are researching to replace the existing copper material with other materials to achieve the goal of lightweighting the vehicle. Lightweight requirements are also a growing challenge in aerospace.
In the early days, several major wiring harness manufacturers such as TE, Sumitomo, Furukawa, and Yazaki all proposed some highly feasible and operable solutions for using aluminum or aluminum alloy instead of copper as the material for electrical conduction and signal transmission. Because the use of aluminum will reduce the weight by 20%-40% compared with copper, and it has an advantage in cost. However, various related solutions have not been popularized in application at present.
Insulation harness technology (IHT) for flexible circuit boards developed by Trackwise in the UK, can help manufacture flexible printed circuits of any length. Trackwise’s company has manufactured the world’s first and longest 26-meter FPC, which can support the control and transmission of power and communication signals without additional wiring harness due to its lightweight advantage. The technology is already used in spacecraft and could be adopted in automobiles to the same advantage.
The intelligent development of electric vehicles is a trend in the future development of automotive technology . The wide range of product applications of electric vehicles has created more new technology applications related to automobiles, thus endowing automobiles with more social features.
At present, electric vehicles represented by Tesla’s FPC power battery FPCFPC solution to replace traditional copper wiring harnesses have been completely recognized by the market, besides greatly reducing weight and improving space utilization, it can also realize automatic assembly, add fuse current protection design to improve safety, etc.
As the PC solution is widely adopted in the mainstream models of electric vehicles, the FPC solution will be promoted to become the mainstream solution for power battery signal transmission.