Flexible Printed Circuit board (FPC, Flexible Printed Circuit) is a circuit board made of flexible copper-clad plate as a substrate, used as a signal transmission medium for the connection of electronic products, with high wiring assembly density, good bending, lightweight, flexible process and so on. FPC can generally be divided into single-layer FPC, double-layer FPC, multi-layer FPC and soft and hard combined board.

Complex and cumbersome automotive wiring harness system

For automobiles, both fuel vehicles and intelligent vehicles have a large number of FPC applications, generally an electric vehicle will be up to more than 100 FPC applications; Mainly in the automotive electronics plate, automotive electronics is the general term for automotive electronic control devices and automotive electronic control devices. It mainly includes engine control system, chassis control system and automobile electronic control system; And from the structure, space and other considerations.

In the future, new energy vehicles will definitely use FPC to replace wiring harnesses in large numbers, which is a very important trend. FPC will be applied in many parts of the vehicle, such as battery BMS, vehicle lighting system, gate control system, camera module, etc. In this case, the FPC and vehicle camera modules in the battery BMS have the highest application value and are also key development areas.

Application of FPC in new energy vehicle BMS system

The FPC Cable application of BMS is mainly in the battery, and the battery technology is one of the key factors restricting the performance of the vehicle. Cost and space are two important factors for batteries, and it is crucial to improve battery technology, reduce size and reduce cost.

As far as the current technology is concerned, the capacity of the battery is basically to the extreme, everyone is asking the structure to efficiency, how to maximize the use of space, and the size of the battery PACK is almost fixed, so the number of batteries can be loaded in the pack is actually limited.

Previous new energy batteries are the use of traditional copper wire harness scheme, in the PACK can be loaded in the number of batteries is actually limited, the need for a lot of wiring harness, the space is crowded; The use of FPC instead of traditional BMS wiring not only ensures the stability of performance, but also reduces the risk of upper cover friction caused by breathing. Pack assembly, the traditional wiring harness relies on workers to manually fix the port on the battery pack, the degree of automation is low, due to the thin thickness of the FPC, the battery pack structure is customized, the assembly can be grabbed by the mechanical arm directly placed on the battery pack, the degree of automation is high, more suitable for large-scale mass production, which is also the mainstream practice of each family. Even in the long run, the circuit of the motherboard and slave board can be replaced by a chip, and the chip can be installed on the FPC, which can maximize the stability of the product, save space and reduce costs.

In addition, the comprehensive cost of the FPC program is still lower than the wire harness program, although the traditional wire harness is cheaper from the perspective of raw materials, but in the module link, the production line of a wire harness program may need 15 workers, the production line of the soft board program may only need five or six people, and the consistency of the FPC is better.

The collection cable is an important part of the BMS system of new energy vehicles to monitor the voltage and temperature of the new energy power battery cell; Connect data acquisition and transmission with overcurrent protection function; Protect the car power battery cell, abnormal short circuit automatically disconnect and other functions.

Previously, the new energy vehicle power battery collection wire used the traditional copper wire harness scheme, the conventional wire harness is formed by the copper wire surrounded by plastic, and each wire harness reaches an electrode when the battery pack is connected. When the power battery pack current signal is many, many wire harnesses are needed to match, and the space is crowded.

Compared with copper wire harness, FPC has outstanding advantages in safety, lightweight and regular layout due to its high integration, ultra-thin thickness and ultra-softness, and the trend of FPC replacing copper wire harness is clear.

FPC should have the following advantages in the power battery module

● Highly integrated: self-embedded Fuse, connector, chip NTC, aluminum/nickel terminals; It not only provides excellent and consistent electrical performance, but also can meet the design requirements of smaller and higher density installation with three spatial wiring and the appearance can be changed according to the limitations of space, which is suitable for the development of high-density, miniaturization and high reliability, so as to achieve the integration of component assembly and wire connection.

● Automatic assembly: fast and accurate assembly, which is conducive to automation; In the assembly and fault tolerance here, you can avoid a lot of manual errors in the harness design, and reduce a lot of opportunities for insertion errors at the connector level. Using FPC sampling, the Module integration process complexity can be reduced, and the connection between FPC and battery busbar can be automated welding, effectively reducing labor costs. Even if the customer is unable to mature automatic welding, the traditional screw locking method can still effectively reduce the manual input.

● Ultra-thin thickness: 0.34mm in conductor area, 2mm in NTC.

● Ultra-soft: the conductor area can be bent and assembled at 90° and 180°.

● Lightweight: When the vehicle is used, the weight can be reduced by about 1kg compared to the wiring harness scheme.

● Cost advantage: From the cost point of view, the cost of FPC itself is not high, for the connection cost, there is a great reduction.

At present, the FPC program has become the most important choice for most new energy vehicle models.

The FPC is integrated into the CCS (Cells Contact System, integrated bus, and wiring harness assembly). CCS products are composed of FPC, plastic structural parts, copper-aluminum bars, etc. The copper-aluminum bars are connected in series and parallel by laser welding. The FPC is connected with the copper-aluminum bars and plastic structural parts to form electrical connections and signal detection structural parts.

Application of FPC in vehicle camera module

The camera module is mainly composed of lens, Sensor, image processing chip, FPC flexible circuit board and other structures, and is a crucial electronic device for image capture.

Among them, the main functions of FPC flexible printed circuit board in the camera module are as follows:

(1) Provide electrical characteristics and play the role of electrical connection;

(2) Provide mechanical properties to support the fixing and assembly of electronic components;

③ It can realize automatic mounting, soldering and detection between integrated circuits and electronic components.

After the camera module adopts FPC, the error of manual wiring is avoided, and the integrated circuit and electronic components can be automatically inserted, mounted, soldering and testing, which makes the product quality and labor productivity improved, while the cost is reduced, and the maintenance is more convenient!

 FPC solution

In general, the soft package and hard package battery is a different FPC program, the various practices are not the same, including the end of the connector different connection forms have different programs (crimping, welding, etc.) FPC the biggest benefit is its flexibility, in it can be upgraded with the battery control technology iteration, will evolve a lot of forms, itself is also a customized product.

In the era of intelligent vehicles, FPC in the battery of a large number of automation applications is only a matter of time, the future of new energy vehicles will certainly use a large number of FPC instead of wiring harness, in multiple parts of the vehicle application implementation, and FPC technology in the field of new energy vehicles will also become an important trend!

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