Battery Laser Welding: The Alternative to Ultrasonic Wire Bonding
When making interconnections in battery modules, laser welding is faster than traditional wire bonding. For cylindrical cells, busbars can even be welded directly to the cells instead of connected via wires, diminishing by half the number of welds in the module. Single-mode fiber lasers also provide an excellent and controlled weld penetration with minimal spatter and reduced heat.
Whereas ultrasonic welding systems use sonotrodes specifically designed for each application and limited to simple shapes, the Laserax welding systems can be adjusted on the fly to create various welding patterns and sizes.
Overview of battery welding applications
- Materials: Copper, nickel, aluminum, and stainless steel, dissimilar metals
- Types of cells: Cylindrical and prismatic
- Battery components: Tabs, terminals, foils, busbars, cell cases, safety vents, cover plates
THE FASTEST WELDING PROCESS
When making cell-to-busbar connections, ultrasonic wire bonding typically takes between 500-1000ms per weld. Laser welding is much faster because it involves fewer, smoother mechanical movements: only ultra-fast mirrors located in the laser head need to be moved to position the laser beam. This drastically reduces the positioning time for each weld. When integrated with our robots, the average welding time including mechanical movements between cells can reach values under 100ms per cell.
|Busbar Thickness||Cell Thickness||Cell Type||Weld Dimension||Laser Power||Resistivity (μΩ)||Shear Test (N)||Time (ms)||Depth of Penetration (μm)|
|250 μm Al 1100||250 μm nickel-plated steel||21700 cylindrical||2 circles (diameter of 2 mm and 3.5 mm)||500W||5||195||39||80‑120|
|500 μm Al 1100||250 μm nickel-plated steel||4680 cylindrical||2 circles (diameter of 3 mm and 5 mm)||850W||3.5||550||37||80‑120|
|500 μm Al 1100||1 mm Al 3000||4680 cylindrical||2 circles (diameter of 7 mm and 9 mm)||850W||0.5||740||77||150‑250|
|2.32 mm Al||1.62 mm Al||Prismatic||Spiral (length of 22.5 mm)||2000W||5||1500||262||300‑500|
|2.32 mm Al||1.62 mm nickel-plated copper||Prismatic||Spiral (length of 22.5 mm)||2000W||6||2400||634||300‑500|
REAL-TIME WELD MONITORING TO DETECT BAD WELDS
Laser Weld Monitoring (LWM) devices can be used to detect bad welds in real time during laser welding. This ensures that every single weld in the battery is good, and that defective ones are reworked right away.
Optical sensors installed in the laser use reflected and emitted radiation from the weld to determine if the weld is good. They can detect different types of weld defects such as gap or contamination.
Because of our faster welding speed, a single laser welding machine can easily work like 10 ultrasonic wire bonders. This minimizes the number of machines needed in production facilities, allowing you to:
- Save square footage
- Save energy
- Reduce maintenance
CYLINDRICAL CELLS: FROM 4 WELDS TO 2 WELDS
Whereas ultrasonic wire bonding typically requires 4 welds per cell, laser welding only needs 2. This provides several benefits:
- A larger contact area
- Half as many potential failure points
- One weld carries all the current (higher current per weld)
- Less mechanical stress transferred to the module
- Smaller resistance (lower heat & electrical loss)
- Better current distribution
- Better heat transfer from cells to busbar conductors
- Fastest lasers on the market with unmatched scanning speed
- Turnkey solutions (Class 1 certified laser safety, fume extraction, vision, automation, etc.)
- Optical configuration that prevents overheating
- Quickly configuration for different battery assemblies (automatic change in the laser configuration)
- Minimal heat affected zone (HAZ)