With the rapid development of the new energy vehicle industry, the performance and safety of power batteries as core components directly determine the vehicle’s range and user experience. The Battery Management System (BM5), as the “nerve center” of power batteries, undertakes key tasks such as real-time monitoring, balanced management, and fault warning. In this field, flexible circuit boards (FPCs) are gradually replacing traditional copper wire harnesses with their lightweight, high-density integration, and flexible layout characteristics, becoming the core driving force for upgrading BMS technology.
In traditional BMS systems, copper wire harnesses are difficult to adapt to the space requirements of high-density battery modules due to their large size, high weight, and complex wiring. Traditional wire harness solutions require hundreds of independent copper wires to connect battery cells, resulting in less than 70% utilization of internal space in the battery pack, and the total weight of the wire harness accounts for more than 5% of the total mass of the battery pack. In contrast, FPC integrates voltage acquisition, temperature sensing, overcurrent protection and other circuits on single-layer or multi-layer flexible substrates, with a thickness controlled within 0.2mm, reducing weight by 80%, and supporting three-dimensional zero fold layout, increasing the space utilization rate of battery packs to over 90%.
The core value of FPC in BMS lies in its highly integrated capability. Through embedded design, FPC can integrate temperature sensors (such as NTC thermistors), voltage detection circuits, and communication interfaces to achieve precise acquisition of battery level parameters. The copper coating of FPC forms a micro porous interconnect structure through laser drilling technology, supporting multi-layer circuit stacking, thereby achieving isolation design between signal and power lines in limited space and reducing electromagnetic interference risks. This integrated design not only simplifies the BMS architecture, but also provides high-precision data support for battery state of health (SOH) estimation and thermal runaway warning algorithms.
Traditional wiring harnesses rely on manual welding and assembly, resulting in low efficiency and poor consistency. FPC adopts roll to roll (R2R) continuous production process and surface mount technology (SMT) to achieve full process automation. The working environment of power batteries is harsh, requiring tolerance to temperature shocks ranging from -40 ℃ to 120 ℃, mechanical vibrations at 2000Hz, and wet and hot corrosion. FPC can address these challenges through material and process innovation: 1. Substrate performance optimization: using polyimide (PI) substrate, its glass transition temperature (Tg) reaches 260 ℃, tensile strength>200MPa, and maintains circuit integrity after 1000 dome bending tests. 2. Surface treatment technology: The nickel gold plating (ENIG) process extends the anti-oxidation life of the copper layer to more than 10 years, and the contact resistance fluctuation is less than 1%. 3. Structural reinforcement design: By adding stainless steel reinforcement plates or FR4 rigid areas, the local bending stiffness is increased by 300% to adapt to the mechanical stress during battery module assembly.
The application of flexible circuit boards in BMS systems for new energy vehicles not only solves the bottleneck of traditional technology, but also promotes the leap of battery management towards high precision, high reliability, and intelligence through collaborative innovation in materials, processes, and design. This technological innovation not only provides the underlying support for carbon neutrality goals, but also marks the comprehensive transformation of automotive electronics from a “mechanical dominated” to a “flexible intelligent” era.