Imagine the PCB as a traffic network, where current is the traffic flow.
When dealing with "peak traffic" at the 100A level, simply widening all "roads" (increasing overall copper weight) is an inefficient waste of resources. The real bottlenecks often exist only on a few "main arteries."
An elegant solution is to construct an "overpass" directly above these main roads: The SMT Busbar (Current-Carrying Copper Strip). It doesn't occupy valuable "ground" (inner PCB layer) space, yet carries huge "traffic" (current) with extremely low "tolls" (resistance).
01. Enhancing Current Carrying Capacity
▶ Shunting and Reducing Current Density
Busbars provide a low-impedance path to shunt high currents, significantly reducing the current density in PCB traces. Adding busbars to the Power Delivery Network (PDN) prevents localized hotspots and component damage.
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Case Study: After adding copper busbars, peak current density dropped significantly from 131.8A/mm², reducing temperature rise from 70°C to a safe range.
▶ Increasing Conductor Cross-Section
By embedding copper strips or surface-mounting them, the effective cross-sectional area of the conductor is drastically increased.
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Application: A standard SMT copper block (e.g., 6mm×4mm×1mm) can carry 20A with a temperature rise kept within 15°C. This technology is widely used in Tesla's body controllers.
02. Optimizing Thermal Management
▶ High Thermal Conductivity Design
Copper has twice the thermal conductivity of aluminum. Busbars act as thermal bridges, rapidly conducting heat from power devices to the PCB or heatsinks.
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Embedded Copper Blocks: Buried within the PCB to contact heat sources directly, enabling vertical heat dissipation and increasing current density by 15%.
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Surface Arrays: Micro-copper pillars on the TOP layer enhance the surface area for dissipation.
▶ Direct Heat Dissipation Channels
Surface-mount busbars are exposed to air, utilizing natural convection for cooling.
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Simulation Results: Thermal analysis confirms that adding busbars results in a more uniform temperature distribution and eliminates localized hotspots.
03. Process & Design Optimization
▶ SMT Compatibility
Modern busbars are plated with Tin/Nickel, making them fully compatible with SMT automatic placement.
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Cost Reduction: For example, mounting a 0.8mm thick copper bar on the back of a motherboard eliminates the need for extra PCB layers, reducing manufacturing costs by approximately 20%.
▶ Mitigating Current Crowding
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Star Configuration: Expanding copper foil at power device pins minimizes peak current density.
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Structural Integrity: While busbars strengthen the PCB, we recommend using short busbar link structures or honeycomb via arrays (with conductive resin plugging) to manage thermal expansion mismatches and reduce thermal resistance by 18%.
04. Comprehensive Comparison
| Solution | Current Capacity | Thermal Efficiency | Cost & Process |
| Traditional Heavy Copper | Medium (Depends on width) | Average (Depends on area) | High Cost (Increases overall copper weight) |
| Increasing PCB Layers | Limited Improvement | Negligible Improvement | Cost Increases ~20% |
| SMT Busbar (Surface/Embedded) | High (50A+ easily) | Excellent (Vertical/Convection) | No extra layers, SMT Compatible, Fast Customization |