Busbar - Not only for conductivity, but also for improving the heat dissipation system

author: Milliohm Electronic

2025-09-12

I: Busbar Overview

Definition: A busbar is a conductive connector used to transmit current in electrical systems. Typically made of metal (such as copper, aluminum, or their alloys), it comes in the form of bars, plates, or strips. It is also commonly referred to as a "busbar," "busbar," or "current-carrying copper sheet." Essentially, a busbar establishes a conductive path between two or more electrical components or increases the path's carrying capacity, enabling direct current transmission. Its core function is to transmit current and dissipate heat, much like a specialized "wire."

II: The Role of Busbars

A. "Bridge" for Current Transmission

① Establishing a Conductive Circuit: They create a conductive path between two or more electrical components, transferring current from one end to the other (such as heating elements, motors, and circuit modules). They function like a "specialized wire" or "jumper wire."

② Optimizing a Replacement for Traditional Wires: In certain scenarios, busbars offer advantages over traditional wires. Busbars typically connect components through surface contact, reducing contact resistance, voltage drop, and power loss. They are more resistant to vibration and shock than wires, making them suitable for dynamic environments such as industrial equipment and automobiles.

③ Improving Current Carrying Capacity (Electromagnetic Compatibility): Copper, with its excellent electrical conductivity, can be used as a current carrier. While PCB copper plating is costly and has limited current-carrying capacity, attaching busbars can improve current handling overall, resulting in lower resistance and impedance than standard PCB traces.

B. "Housekeeper" for Temperature Rise Optimization

① Reduced Heat Loss: Copper has extremely low resistivity. According to the thermal equation Q = I^2Rt, for current-carrying carriers of the same size, the lower the resistivity, the smaller R and Q. Therefore, copper as a carrier can effectively reduce energy loss and improve circuit efficiency.

② Assisted Heat Dissipation: Copper has a thermal conductivity of 401W/(M・K). Through conduction through the copper itself, radiation through air, and increased heat dissipation surface area, the heat exchange capacity in the circuit is improved, dissipating heat efficiently (in conjunction with equipment cooling methods such as air cooling and water cooling), thereby reducing temperature rise.

③ Indirect EMC Optimization: Excessive temperatures in other high-current components (differential-mode inductors, common-mode inductors, transformers, etc.) can lead to EMC violations, magnetic failure, and cracking. Adding current-carrying strips to heat-generating areas can increase heat dissipation and indirectly improve EMC.

III: Characteristics and Advantages of Busbars

① High Conductivity: Copper is an excellent conductive material, second only to silver in conductivity. It effectively reduces power transmission losses, improves efficiency, and satisfies power transmission requirements.

② High Current Carrying Capacity: Its extremely low resistivity minimizes heat loss, reduces heat generation, and improves overall current carrying capacity.

③ Corrosion Resistance: Copper exhibits a certain degree of corrosion resistance and can withstand harsh environments through processes such as nickel and tin plating, resisting oxidation and corrosion and extending its service life.

④ High Reliability: It maintains its conductive properties under harsh conditions and over extended use, demonstrating excellent long-term reliability.

IV: Material selection advantages

Material	Electrical Conductivity	Thermal Conductivity	Tensile Strength	Price	Application Scenario
Copper (T2)	101% IACS	391W/(m·K)	≥220 MPa	Higher	High conductivity occasions
Brass (H65)	28% IACS	120W/(m·K)	≥340 MPa	Medium	High mechanical strength requirements
Aluminum (1350)	61% IACS	237W/(m·K)	≥90MPa	Lower	Weight-sensitive occasions

There are many materials available for current busbars on the market, such as copper, brass, phosphor copper, and silver. Milliohm Electronic uses T2 copper as its raw material. This material has a copper content of over 99.90% and a resistivity of only 0.0172Ωm, effectively reducing power transmission losses. Its' electrical conductivity is superior to brass and phosphor copper, providing a high current-carrying capacity and excellent processing flexibility.

V: Advantages of Busbar Processing

① Anti-Oxidation Treatment - Electroplating: Nickel, chromium, tin, and other metals are electroplated on the surface of the copper busbar. The nickel plating layer is hard and wear-resistant, blocking oxygen from contacting the copper and improving its oxidation resistance. Chromium plating forms a dense oxide film, enhancing corrosion resistance. Tin plating improves solderability and reduces problems such as cold solder joints and insufficient thrust during SMT processing.

② Surface Treatment - Ultrasonic Cleaning / Magnetic Polishing: After the raw materials are stamped and formed, the busbar undergoes ultrasonic cleaning and magnetic polishing to remove surface burrs and metal powder generated by cutting. This prevents cold solder joints from heating during use due to burrs and metal dust, thereby improving product reliability and aesthetics.

③ Flatness Treatment - 180° Leveling + Inspection Before Shipment: Flatness affects heat dissipation on the PCB. For example, cold solder joints caused by warped leads or gaps in the product can cause severe overheating of the PCB.

④ Taping packaging - convenient for automated placement: The busbar tape packaging is convenient for automated production and SMT placement. It is moisture-proof, dust-proof, and anti-static, reducing mechanical damage. The reel-type structure facilitates packaging and transportation, reducing packaging material waste and component loss.

VI: Application Scenarios

① Power Systems: In substations, busbars are used to connect transformers, circuit breakers, disconnectors, and other equipment to collect and distribute high-voltage power.

② Industrial Equipment: Applications include uninterruptible power supplies (UPSs), inverters, drive systems for industrial motors (such as fans, pumps, and compressors), and power supply cabinets in communication base stations.

③ Automotive/New Energy: Fast charging stations/charging modules typically draw high internal currents. Current-carrying bars are typically used to dissipate excess current, and cooling systems are used to dissipate heat to prevent overheating caused by excessive current.

VII: Design and Selection

① Layout Principles

Interference Avoidance Principle: Maintain an appropriate distance between busbars and sensitive signal lines to reduce electromagnetic interference. Consider using shielding layers, meshes, enclosures, or isolation zones to further minimize interference.

Uniform Distribution Principle: In multi-point power supply scenarios, ensure that current is evenly distributed to all load points to avoid hotspots of concentrated current.

Place the busbars in a location that facilitates heat dissipation, such as at the edge of the PCB or near a heat sink. If necessary, increase heat dissipation holes or copper foil area to enhance heat dissipation.

Current Diversion Design: For high-current applications, consider connecting multiple busbars in parallel with consistent length and width to achieve uniform current distribution.

② Selection and Matching

Dimension Selection: Calculate the required busbar width and thickness based on the current level.

Shape Design: Use straight busbars whenever possible and avoid sharp turns. If turns are necessary, use arc transitions instead of right-angle turns to reduce local resistance.

Interface Design: Design appropriate transition areas at the interface between the busbar and the connector or component. Use a gradient width or fan-shaped design to avoid sudden changes in current density.

Interlayer Connections: If the busbar needs to cross layers, use a sufficient number and size of vias, evenly distributed to avoid current concentration points.

Note: If you would like to learn more about our products or solutions, or applications in specific scenarios, please feel free to contact our technical support team.

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