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Copper busbars are one of the most demanding joints in a lithium battery pack. They must carry high current with low resistance, resist vibration, and stay leak-free and low-spatter at the module level. Copper’s high reflectivity at 1080 nm and high thermal conductivity narrow the laser welding window, so the question is not simply which numbers to dial in. The best laser welding parameters for copper busbars are the set that produces a stable, low-spatter weld with the required penetration and electrical performance at the lowest practical heat input. This article explains the parameter levers and how they map to the SFX Laser DLW-150B and DLW-300B enclosed laser welding platform.
Why copper busbar welding needs a different parameter approach
Copper reflects a large share of near-infrared laser energy until a stable melt is established. It also conducts heat away from the weld zone quickly. The result is a narrow process window: too little energy gives lack of fusion, while too much energy creates spatter, porosity, undercut, or a heat-affected zone that can disturb nearby battery components. For battery pack busbars, the best parameter set is therefore not a single recipe copied from steel or aluminum. It is a qualified combination of laser mode, peak power, pulse width, frequency, average power, focus position, clamping, and travel speed, verified by cross-section and electrical test.
Parameter levers that matter for copper busbars
| Parameter | Effect on copper busbar welding | Practical direction on the SFX DLW-150B and DLW-300B |
|---|---|---|
| Laser mode | Quasi-continuous-wave operation combines continuous-wave and pulsed-laser advantages, giving high energy output with low heat effect. | Use the continuous/modulation mode to shape the energy input. Modulation helps control heat on thin copper tabs and foil-to-busbar joints. |
| Peak power | Higher peak power improves coupling into reflective copper and supports penetration, but excessive peak power can increase spatter. | DLW-150B offers 1500 W peak power; DLW-300B offers 3000 W peak power. Use the lowest peak power that achieves the required penetration and resistance. |
| Pulse width | Short pulses limit heat input and distortion. Longer pulses can increase penetration but widen the heat-affected zone. | Adjust within the 0.005–50 ms range. Start short and increase only when penetration or fusion is insufficient. |
| Frequency | Higher frequency with lower pulse energy can smooth the seam and reduce spatter. Lower frequency with higher energy can deepen penetration. | Use up to 20 kHz. Balance frequency with peak power and pulse width rather than changing one variable alone. |
| Average power | Sets overall heat input and influences achievable welding speed. | Adjust from 10–100% after peak power and pulse shape are established. Fine-tune average power to eliminate spatter without losing penetration. |
| Focus position | Copper welding requires tight, repeatable focus because the spot is small and reflectivity is high. | Use one-click quick positioning and automatic weld recognition and calibration on the DLW series. Confirm focus on scrap copper before production. |
| Clamping and fit-up | Gaps, weak clamping, and surface contamination cause incomplete fusion and weak welds. | Use the automated lifting and clamping structure. Maintain clean copper surfaces and zero gap at the busbar-to-tab interface. |
| Travel speed | Speed balances penetration and heat input. Faster travel reduces heat but can cause lack of fusion; slower travel increases heat and spatter risk. | Establish speed by experiment with the qualified pulse and power settings. Change speed only after the focus and clamping are stable. |
| Shielding gas coverage, if used in your qualified procedure | Coverage can reduce oxidation and stabilize the melt in copper welding. | Apply according to your battery-pack welding procedure and verify with visual and cross-section inspection. |
A practical starting strategy for copper busbars in lithium battery packs
- Confirm the stack thickness and joint design. The SFX DLW-150B and DLW-300B are specified for a welding capacity of 0.2–1.5 mm. Confirm that your copper busbar, tab, or connector stack falls within this range before fixing parameters.
- Select the platform based on headroom. For thin foil-to-busbar tabs and precision joints, the DLW-150B with 150 W average power and 1500 W peak power may be sufficient. For thicker copper joints within the 0.2–1.5 mm capacity, the DLW-300B provides 300 W average power and 3000 W peak power for more process headroom.
- Start in quasi-continuous-wave mode. The DLW series is designed for precision welding of ultra-thin metals below 0.5 mm, with high energy output and low heat effect. Use modulation to shape the pulse and control heat input.
- Begin with a high-peak-power, short-pulse, high-frequency direction. For copper, this direction helps overcome reflectivity and create a stable melt. Then adjust pulse width and average power to eliminate spatter and porosity.
- Lock focus and clamping before optimizing speed. The DLW platform supports 2D graphics, a larger single-pass welding area, and more uniform energy distribution. Use these capabilities with rigid clamping to keep the weld consistent across the busbar length.
- Run a structured design of experiments. Change one variable at a time: peak power, pulse width, frequency, average power, and travel speed. Record spatter level, bead appearance, cross-section penetration, and joint resistance for each condition.
- Qualify the recipe and store it. The DLW series includes a multilingual process library and CNC control so a validated recipe can be recalled for repeat production.
What “best” should mean in production
- Stable penetration: full or controlled penetration into the busbar or tab without burn-through or undercut.
- Low spatter: no loose copper particles that can create short-circuit risks inside the battery pack.
- Low and stable resistance: the joint meets the electrical resistance target after aging and vibration.
- Repeatable fit-up: clamping and part tolerance keep the gap consistent from module to module.
- Verified metallurgy: cross-sections show sound fusion with limited porosity and an acceptable heat-affected zone.
Quality verification for battery pack busbars
Parameter development should always be tied to inspection. Use visual inspection for spatter and bead form, cross-sectioning for penetration and porosity, pull or shear testing for mechanical strength, and resistance measurement for electrical performance. The DLW series supports automatic recognition and calibration of welds, intelligent motion trajectory, and teaching programming for quick start, which helps transfer a qualified copper busbar recipe into repeatable production.
SFX Laser solution for new energy battery module welding
The SFX DLW-150B and DLW-300B enclosed laser welding machine is customized for new energy battery module welding. Key specifications include 150 W and 300 W laser power, 1500 W and 3000 W peak power, 1080±2 nm wavelength, 0.2–1.5 mm welding capacity, continuous/modulation laser mode, 10–100% power adjustment, up to 20 kHz frequency, 0.005–50 ms pulse width range, AC220V±10% input, and air cooling. The platform is designed for precision welding of ultra-thin metals, with an automated lifting and clamping structure to reduce incomplete welding and weak welds.
If you are developing copper busbar welding for lithium battery packs, contact SFX Laser at [email protected] or +1 (714) 391-6302 (USA CA Office) to review your stack thickness, joint design, and production requirements.
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