New energy vehicle film capacitor busbar product industry knowledge details

New energy vehicle film capacitor busbar is a laminated composite conductive connector specially designed for DC support capacitors in electric vehicles, hybrid vehicles and plug-in hybrid vehicles. This product is usually made of two or more layers of copper bars sandwiched by an insulating medium (such as polyester film or polypropylene film) and laminated by hot pressing to form an integrated sandwich structure of "positive electrode-insulation-negative electrode". Terminals are drawn out at both ends or sides for connecting power semiconductor modules (such as IGBT, SiC modules) and DC busbars. Compared with traditional discrete wire connections, this integrated busbar has extremely low distributed inductance (usually controllable in the range of 10nH to 30nH), which can effectively suppress voltage spikes generated by power switching devices during high-speed switching and protect semiconductor chips from overvoltage breakdown. In terms of product form, New Energy Vehicle Film Capacitor BusBar is a standard name in the industry, emphasizing its matching relationship with film capacitors; while Automotive Power Connectors is a broader category, covering all high-voltage connectors inside electric vehicles, in which the busbar is responsible for the transmission of large currents between capacitors and power modules.

 

Based on differences in manufacturing processes and surface treatments, Busbar Automotive generally refers to automotive-grade busbar products, which must meet ISO 26262 functional safety standards and LV 215 high-voltage connector specifications. In terms of corrosion resistance and weldability, Tin-plate Busbar Automotive and Tin Plated Copper BusBar for EV refer to busbars with tin-plated surfaces. The thickness of the tin-plated layer is usually 3~10μm, which can prevent oxidation of the copper matrix and provide stable contact resistance when bolts are tightened. From the application level, the busbar electric vehicle covers a full range of products from cell connection in the battery pack, module series connection to capacitor connection in the motor controller; while the ev battery busbar specifically refers to the battery connection row inside the battery pack. The difference from the capacitor busbar is that it needs to withstand more frequent vibrations and cell expansion displacements.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The manufacturing process of new energy vehicle film capacitor busbars combines various technologies such as precision stamping, selective plating, hot press lamination, and CNC bending. Each process has a direct impact on the electrical performance and service life of the final product. The starting point of the process chain is the blanking and forming of copper strips: blanking, punching and pre-bending high-precision copper strips (thickness 1~5mm) are completed in one go through high-speed punches and progressive dies. For multi-layer structures, the positive and negative copper bars need to be processed separately and designed to ensure that they can be accurately aligned after stacking. After stamping is completed, the edges of all copper bars must be chamfered or deburred (chamfer radius 0.5~1.5mm) to prevent sharp burrs from piercing the insulation film in subsequent processes. Next, enter the selective plating process: for Tin-plate Busbar Automotive and Tin Plated Copper BusBar for EV, we only need to tin-plate the connection terminals (that is, the area in contact with the power module or capacitor), while other areas of the copper bar can remain bare copper (will be covered by an insulating layer later). Selective plating is achieved by masking the non-plated area (using special fixtures or photosensitive ink). The thickness of the tin layer is 3~10μm. After plating, a salt spray test is required to verify the corrosion resistance.

 

After electroplating is completed, the most critical lamination process begins. Stack the positive copper bar, insulating film (polypropylene or PET) and negative copper bar in order and then feed them into the vacuum heat press. The hot pressing temperature is controlled between 120~180℃ (depending on the melting point of the insulating film material), the pressure is 5~15kg/cm², and the heat and pressure are maintained for 30~90 seconds. During this process, the surface of the insulating film is partially melted or softened, and closely adheres to the surface of the copper bar under pressure. After cooling, a solid composite without bubbles and displacement is formed. For the New Energy Vehicle Film Capacitor BusBar, since the capacitor is extremely sensitive to parasitic parameters, the overlapping area and edge alignment of the positive and negative copper bars must be strictly controlled during lamination, otherwise it will cause local inductance to increase or electric field concentration.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The material selection for new energy vehicle film capacitor busbars needs to take into account conductivity, insulation performance, heat resistance and vehicle-level reliability. The conductive substrate usually uses T2 copper or C1100 electrolytic tough copper, with copper content ≥99.90% and conductivity ≥97%IACS. Depending on the current carrying capacity, the thickness of the copper bar is generally between 1mm and 5mm, and the width is designed based on the installation space and current distribution. For high-current applications in busbar electric vehicles, copper-aluminum composite busbars (that is, the middle layer is aluminum and the two sides are covered with copper) are sometimes used to reduce weight while ensuring conductive performance. However, pure copper is still the mainstream in capacitor busbars because the thermal expansion coefficient of copper is more consistent with the ceramic or metal components of the capacitor terminals.

 

In terms of surface treatment, Tin-plate Busbar Automotive and Tin Plated Copper BusBar for EV require the tin plating layer to be dense and uniform, with a thickness of usually 3~8μm. Tin plating has three functions: first, to prevent the copper matrix from oxidation and discoloration during long-term use (the resistivity of copper oxide is much higher than that of metallic copper); second, when the bolts are tightened, the soft tin layer can plastically deform and fill the microscopic gaps on the contact surface, making the contact resistance lower and more stable; third, the chemical stability of the tin layer can slow down electrochemical corrosion when connected to aluminum wires or aluminum terminals. For products that do not require tin plating, partial silver or nickel plating can also be performed on the connection area, but the cost is higher. Insulating materials are the core component of laminated busbars. The insulating medium between two layers of copper bars is usually polypropylene (PP) film or polyethylene terephthalate (PET) film, with a thickness between 0.1mm and 0.5mm. Among them, polypropylene film has lower dielectric loss and higher breakdown field strength, and is suitable for capacitor busbars with demanding electrical performance requirements; while PET film has a higher temperature resistance level (up to 130°C) and is suitable for applications close to heating elements.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The core application industries of new energy vehicle film capacitor busbars are concentrated in the fields of electric vehicle drive systems and charging infrastructure. In the main drive motor controller of pure electric vehicles (BEV) and hybrid electric vehicles (HEV), DC-Link capacitors are connected in parallel between the power battery and the IGBT/SiC power module to smooth the bus voltage, absorb ripple current and suppress voltage spikes. The New Energy Vehicle Film Capacitor BusBar is the bridge connecting the capacitor and the power module - it introduces the DC power from the battery into the capacitor through a very low inductance path, and then delivers the filtered pure DC power to the power module. Since the operating switching frequency of electric vehicle motor controllers is usually between 8 kHz and 20 kHz, the power module will generate extremely high di/dt (current change rate) at the switching moment. If the inductance connected to the busbar is too large, dangerous high-voltage spikes will be induced at both ends of the power module, which may break down the semiconductor chip.

 

Busbar Automotive's laminated composite structure can reduce stray inductance to extremely low levels, which is a key technical measure to ensure the safe operation of power modules. In the fast charging system of electric vehicles, film capacitors and their supporting busbars are also widely used inside the on-board charger (OBC) and DC-DC converter. In these scenarios, Automotive Power Connectors need to withstand large currents during charging (usually 150A to 500A) and continuous vibration during vehicle driving. Therefore, high requirements are placed on the mechanical strength and vibration resistance of the busbar. It is worth noting that with the popularity of 800V high-voltage platforms, the insulation treatment of Tin-plate Busbar Automotive (such as powder coating or dipping) needs to meet a higher withstand voltage level (usually required rated insulation voltage 1000V DC, withstand voltage 3000V AC). In the field of commercial vehicles, such as electric buses and electric trucks, the motor controllers have higher power (up to more than 300kW). The supporting Tin Plated Copper BusBar for EV and busbar electric vehicle often use thicker copper bars (3~6mm) and multi-layer parallel design to reduce losses and temperature rise. Although the application positions of ev battery busbar and capacitor busbar are different, the two have the same design concept - they both pursue low resistance, low inductance and high reliability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We have the low-inductance design and precision manufacturing capabilities of Automotive BusBar. Our team of automotive-grade engineers can complete stray inductance simulation and structural quotation based on your system parameters and deliver standard-compliant samples for your testing and verification.