Al-Cu Busbar Laser Welding: Managing IMC for ESS (2026)
Release time:
2026-02-06
Joining Aluminum (Al) terminals to Copper (Cu) busbars remains one of the more complex tasks in battery assembly due to the inherent formation of brittle Intermetallic Compounds (IMC). Huiyao Laser addresses this challenge by implementing high-frequency "Wobble" welding technology. By oscillating the beam, we aim to manage the melt pool temperature and keep the IMC layer within a manageable thickness, supporting a stable electrical connection of <0.1mΩ.
Addressing the Al-Cu Joining Challenge
Joining Aluminum (Al) terminals to Copper (Cu) busbars remains one of the more complex tasks in battery assembly due to the inherent formation of brittle Intermetallic Compounds (IMC). Huiyao Laser addresses this challenge by implementing high-frequency "Wobble" welding technology. By oscillating the beam, we aim to manage the melt pool temperature and keep the IMC layer within a manageable thickness, supporting a stable electrical connection of <0.1mΩ.
The Strategy of Thermal Asymmetry
Because Copper and Aluminum have significantly different melting points, a standard laser approach can often lead to over-melting of the Aluminum side. Huiyao Laser utilizes a "Thermal Asymmetry" process. By slightly offsetting the laser energy toward the Copper busbar, we allow the Copper to reach its melting point and "wet" the Aluminum surface. This technique is designed to create a metallurgical bond with reduced metal dilution, offering a non-contact alternative to ultrasonic welding that avoids mechanical vibration stress on the cell's internal seals.
Process Comparison: Joining Technologies
| Criterion | Huiyao Wobble Laser | Ultrasonic Welding | Standard Fiber Laser |
| Contact Resistance | Target <0.1mΩ | 0.2−0.4mΩ | High Variability |
| Mechanical Stress | Non-contact | High-frequency Vibration | High Thermal Stress |
| Busbar Thickness | Up to 5mm | Typically <2mm | Limited by Spatter |
| Weld Consistency | High (Visual Tracking) | Mechanical Dependent | Heat-Sensitive |
Engineering Insight: Protecting the Terminal Seal
Prismatic cells are sensitive to heat-affected zones (HAZ) near the terminal seals. Huiyao Laser employs Pulse-Modulated Fiber Lasers with customized power ramping. This allows for a controlled cooling phase at the end of the weld, which is intended to prevent crater cracks and keep the seal temperature within safe operating limits. This focus on thermal control is vital for maintaining the hermetic integrity of the cell over thousands of thermal cycles in the field.
Conclusion
As ESS modules move toward higher current requirements, the reliability of the Al-Cu joint becomes even more critical. Huiyao Laser focuses on refining these welding parameters to support the rigorous uptime demands of 2026 battery production.
Facing Al-Cu welding inconsistencies? See our Laser Welding Solutions or Request a weld-sample analysis from our lab.
AUTHOR: The Huiyao Laser Engineering Team
A collective of solution architects and process engineers at Huiyao Laser, 100% dedicated to solving the core bottlenecks in EV and ESS battery manufacturing.
© 2026 Huiyao Laser Technology Co., Ltd. All Rights Reserved.
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