Laminated busbars: a key component in electrical systems
Feb 05, 2025
product definition
Laminated BusBar is an integrated composite structure connection component formed by alternately laminating multiple layers of conductive materials (usually copper or aluminum) and high-insulating materials (such as epoxy resin, polyester film or aramid paper) through a hot pressing process. This product realizes efficient and reliable electrical connections between power modules, capacitors, and input and output terminals in power electronic systems by transforming the complex connections of traditional discrete wire harnesses into compact, flat, low-inductance laminated structures. From an electrical performance perspective, Laminated BusBar uses the principle of proximity effect to cause the magnetic fields generated by reverse currents flowing in adjacent conductor layers to cancel each other out, thereby significantly reducing the stray inductance of the loop. The reduction of stray inductance plays a decisive role in suppressing the voltage spikes generated by power semiconductor devices such as IGBT during the switching process. It can reduce or even eliminate the use of absorption capacitors, simplify circuit design and reduce system costs.
From a mechanical structure perspective, it integrates multiple connection points into an integral component, reducing the number of wire harnesses and connectors, and improving the system's vibration resistance and assembly consistency. As the most common type, Laminated Copper BusBar uses copper as the conductive layer material. With copper's excellent electrical conductivity and heat conduction capabilities, it is suitable for high current and high power density application scenarios. Copper has low resistivity and can carry higher current under the same cross-sectional area. The thermal expansion coefficient between copper and insulating materials is well matched, which helps to improve the thermal cycle reliability of the product. In addition, Laminated BusBar can also be customized according to electrical schematics and mechanical installation requirements to achieve complex electrical connection topology in a limited space. It is a key supporting component for power electronic equipment to achieve modularization, compactness, and high frequency.
basic structure
The basic structure of BusBar Laminated is composed of three parts: conductive layer, insulating layer and necessary connection terminals. Each layer is tightly combined into a whole through hot pressing process. The conductive layer is usually made of high-purity electrolytic copper or aluminum alloy materials. It can be designed as a single-layer or multi-layer structure according to the current carrying requirements. The thickness, width and outline of each conductive layer are customized according to the current distribution and installation space. The insulation layer is placed between adjacent conductive layers and on the outermost surface. Commonly used insulation materials include polyester film (PET), polyimide film (PI), epoxy glass cloth (FR4) or aramid paper (Nomex). The corresponding material and thickness are selected according to the working voltage level and temperature resistance requirements. Each conductive layer is led out through preset terminals and window openings to achieve electrical connection with external devices such as IGBT modules, capacitors, input and output busbars. After the entire laminated structure is hot-pressed and solidified under high temperature and pressure, the insulating material and the conductive layer form a tight fit without bubbles and delamination.
Adjacent conductive layers are only separated by the insulating layer, thus achieving extremely small inter-layer distance and loop area, which is the structural basis for obtaining low stray inductance characteristics. For applications that require enhanced edge insulation performance or increased creepage distance, secondary injection molding, resin potting or insulating powder coating can be performed on the edge of the laminated busbar to form a closed or semi-closed edge protection structure. In addition, according to the mechanical installation requirements, the laminated busbar can also be integrated with structural parts such as positioning pins, support columns, and insulating gaskets, so that it can perform the dual functions of electrical connection and mechanical support at the same time.
Manufacturing process
The manufacturing process of Laminated BusBar mainly includes the following key links. First, conductive layer processing. Cut out, punch and bend the copper or aluminum plates according to the design drawings. The punching process needs to ensure that the hole position tolerance is within ±0.1mm, and the bending process needs to control the bending angle and bending radius to avoid material cracking or internal stress concentration due to excessive bending. For structures that require the lamination of multiple conductive layers, the shape and hole position of each conductive layer must be accurately aligned. Second, surface treatment. In order to improve the corrosion resistance and contact performance of the conductive layer, the copper conductive layer is usually tin-plated, nickel-plated or silver-plated. Tin plating is the most common method and is suitable for most indoor applications; nickel plating is suitable for high-temperature environments; silver plating is suitable for high-frequency or high-current applications that have extremely high requirements on contact resistance. Surface preparation should be completed before lamination to ensure that the plating covers all surfaces of the conductive layer, including edges and hole walls. Third, the insulation layer is cut and stacked.
The insulating film is precisely cut according to the contour shape of the conductive layer, and laid between the conductive layers and the outermost layer in the designed stacking sequence. The number of insulating layers and the thickness of each layer are determined based on the withstand voltage requirements and distributed capacitance requirements. Fourth, hot pressing molding. Put the stacked conductive layer and insulating layer into a hot press machine and perform hot pressing under the set temperature (usually 150°C to 250°C), pressure and time conditions. During the hot pressing process, the insulating material softens, flows and fills the tiny gaps between the conductive layers, and solidifies after cooling to form an integrated composite structure. The hot pressing parameters need to be optimized according to the characteristics of the insulation material and the thickness of the product to ensure no bubbles, no delamination, and a strong bond. Fifth, edge sealing and insulation enhancement. For products that need to increase the creepage distance or strengthen the edge insulation strength, the edge of the busbar can be subjected to secondary injection molding, resin potting or spraying with insulating powder after hot pressing. Sixth, finished product testing. Each Laminated BusBar must undergo 100% withstand voltage test and insulation resistance test before leaving the factory. The withstand voltage test voltage is based on 2 times the working voltage plus 1000V or the customer's specific requirements. At the same time, sampling is carried out for dimensional inspection, appearance inspection and conduction resistance test. For customers with special requirements, distributed inductance testing or temperature rise testing can also be arranged.
FAQ
Q: What are the main advantages of Laminated BusBar over traditional cable harnesses?
A:Laminated BusBar has multiple advantages over traditional cable harnesses. First, the stray inductance is significantly reduced, which can effectively suppress the turn-off voltage spike of the power semiconductor and reduce or even eliminate the absorption capacitance. Second, the structure is compact and takes up little space, which helps to increase the power density of the equipment. Third, assembly is simple and fast. One busbar assembly can replace dozens of cables and connectors, reducing assembly time and potential failure points. Fourth, the heat dissipation performance is better, and the flat structure facilitates heat conduction and air duct design. Fifth, it has strong vibration resistance and the integrated structure has no risk of wire harness loosening.
Q: How low can the stray inductance of a Laminated BusBar be?
A: The size of stray inductance depends on the lamination structure of the conductive layer, the thickness of the insulating layer, the length of the current path and the outlet method of the terminal. Through optimized design, the stray inductance of Laminated BusBar can be controlled between 10nH and 50nH, while the stray inductance of traditional cable harnesses is usually between 100nH and 500nH. For busbars designed with extremely thin insulation layers (such as 0.1mm) and wide conductive layers, the stray inductance can even be reduced to less than 5nH.
Q: What is the operating temperature range of Laminated BusBar?
A: The operating temperature range mainly depends on the selection of insulation materials. The operating temperature of busbars insulated by polyester film is usually -40°C to +105°C; the operating temperature of busbars insulated by polyimide film can be extended to -55°C to +200°C. The working temperatures of the conductive layer material (copper or aluminum) and the surface treatment layer (tin, nickel, silver) also need to be considered simultaneously. For example, the maximum operating temperature of the tin plating layer is about 150°C. Above this temperature, the tin layer may reflow or accelerate oxidation.
contact us
Our company specializes in the R&D, design and manufacturing of BusBar for Power Electronics, and has full-process service capabilities from solution simulation, mold development, hot press molding to finished product testing. You are welcome to send technical drawings or performance requirements to our engineering team, and we will provide you with a low-inductance optimized design, fast sample delivery, and complete test report support.
