In lithium battery manufacturing, dissimilar metal connections have always been a key bottleneck restricting product performance. External leads in lithium batteries are often made of copper wire, ensuring efficient current transmission due to its excellent conductivity. Battery tabs, on the other hand, are commonly made of aluminum, achieving lightweight design while effectively controlling costs. However, joining aluminum and copper is a recognized technical challenge in the industry. Traditional welding processes easily form high-resistance intermetallic compounds at the interface, severely impacting overall battery performance.
The core issue facing traditional welding methods is the tendency for brittle phases to form at the aluminum-copper interface. These phases not only increase the resistance of the connection but also reduce structural strength. During battery charging and discharging, excessive contact resistance can cause localized heating and, in extreme cases, even thermal runaway, posing a significant threat to battery safety. This pain point is particularly prominent in critical applications such as tab lead extraction for pouch-type lithium batteries and top electrode connection for cylindrical batteries, necessitating the urgent need for more reliable connection solutions.
The advent of ultrasonic soldering irons offers an innovative approach to addressing this challenge. Its core principle is to use high-frequency vibration energy to promote active diffusion of atoms on the aluminum and copper surfaces, forming a uniform and stable diffusion layer at the interface between the two metals. This unique connection method fundamentally reduces the formation of brittle phases, significantly reducing contact resistance to below 50μΩ, far exceeding the performance of traditional welding processes. Furthermore, this atomic-level diffusion bonding imparts greater structural strength to the interface, providing excellent resistance to vibration and impact, and adapting to the complex operating conditions encountered during battery operation.
In practical applications, ultrasonic soldering irons have demonstrated significant advantages. For the tab connection of soft-pack lithium batteries, they can precisely and reliably connect the aluminum tab to the copper lead, avoiding interface defects caused by traditional welding and ensuring stable current transmission. For the top electrode connection of cylindrical batteries, this technology can effectively improve the consistency and durability of the electrode connection, reduce the risk of battery overheating, and provide strong guarantees for the safety performance and service life of lithium batteries. With the continuous advancement of lithium battery technology, ultrasonic soldering irons are expected to become one of the core technologies for solving the difficult problem of joining dissimilar metals between aluminum and copper, driving the lithium battery industry towards higher efficiency and safety.
