Ultrasonic welding, laser welding and resistance welding are the three common processes for joining thin metal sheets and harnesses. They work differently and suit different jobs — picking the wrong one costs money and quality.
Ultrasonic metal welding
Joins metals solid-state through high-frequency friction, without melting. Advantages: minimal heat effect, no spatter, no filler needed — ideal for stacked thin sheets of highly conductive copper and aluminum, such as battery tabs and harness terminals. Limitation: weld area is constrained by horn size, so it's unsuitable for large continuous seams.
Laser welding
Melts metal with a high-energy laser beam. Advantages: deep penetration, high speed, complex weld paths possible — good for continuous sealed welds on structural parts. Drawbacks: high equipment investment, difficult on highly reflective copper and aluminum, and the melting process causes some thermal distortion.
Resistance welding
Generates heat from electrical resistance at the contact point to melt the metal. Advantages: simple equipment, low cost, mature for steel sheet spot welding. Drawbacks: electrodes wear fast and need regular dressing; inefficient and inconsistent on highly conductive copper and aluminum.
Selection advice
For battery tabs, multi-layer foils and harness terminals, consider ultrasonic welding first; for deep-penetration continuous sealed structural welds, consider laser; for ordinary steel spot welding on a budget, resistance welding remains practical. Always validate with sample welds — pull tests, resistance measurements and cross-sections beat brochures for decision-making.