Where is ultrasonic welding actually used? This guide breaks it down by industry — from automotive high-voltage harnesses and EV battery tabs to medical devices, food packaging, and semiconductor bonding — and explains why ultrasonic Cu-Al welding has become the common choice.
Automotive High-Voltage Harnesses: From Crimping to Ultrasonic Welding
As EV voltage platforms move from 400V to 800V, harnesses must carry 4–5× the current, with wire size rising from 50 mm² to over 200 mm². Traditional crimping relies on a mechanical interlock, leaving strands as independent conductors with imperfect contact; resistance rises over time and becomes a heat hazard. Ultrasonic welding fuses the strands into a metallurgical bond with low, long-term stable resistance.
Reference data: about 1–3 μΩ initial resistance on a 70 mm² harness, below 0.1 mΩ in broader testing; joint pull force rises from 2616 N to 6650 N as energy goes from 5 kJ to 11 kJ.
EV Batteries: Tabs, Foils & Busbars
Batteries are the fastest-growing ultrasonic metal welding application, covering positive/negative tabs, stacked foil groups, and tab-to-busbar connections. Ultrasonic welding suits thin pouch cell tabs especially well because it creates no melt pool and won’t overheat and burn the foil like laser welding can. Typical cycle time is 0.3–0.8 s, with challenges around multi-layer foil consistency, anvil wear, and underweld/overweld detection.
Energy Storage & EV Charging
Energy storage demands large-capacity cells, busbars/busbars, battery-cluster connections, and long-term cycle reliability. DC fast chargers often run over 250A, with plugs subject to frequent insertion cycles and vehicle vibration — so every connection needs both stable resistance and robust welds. Ultrasonic welding delivers both, while reducing copper terminals, plastic housings, and tooling costs.
Solar & E-Motors
In solar, ultrasonic welding replaces part of the soldering for copper ribbons, bus ribbons, and junction-box conductive connections — cutting energy and enabling flux-free processes for outdoor humidity and thermal cycling. In motors, it is used for magnet-wire end preparation, hairpin windings, and flat-wire motors, where low resistance and high strength matter, competing with laser welding and brazing.
Medical Devices: No Adhesive, Sterile, Biocompatible
Medical is a high-certainty direction for ultrasonic plastic welding because its strengths line up: no adhesive, no particulate contamination, hermetic and leak-tight, biocompatible, and cleanroom-friendly. Uses include infusion sets, catheters, syringes, filters, plasma separation cups, sterile connectors, and microfluidic devices. It can even join metal-to-plastic in some cases, such as a plastic cap to an aluminum seal in vaccine cold-chain packaging.
Packaging, Personal Care & Food
Key selling points are speed, continuous production, tolerance to contaminants, localized sealing, and no adhesive. Uses include flexible packaging, caps, bag sealing, filling lines, coffee capsules, cosmetics packaging, and nonwoven filter media. High-speed packaging is a growth area named in multiple industry reports.
Electronics & Semiconductors: From Welding to Bonding
Here the technology extends to ultrasonic wire bonding: aluminum, copper, and gold wire bonding, plus IGBT, SiC, and GaN power-module packages. A very small heat effect on the die and tiny, consistently shaped welds create high technical barriers and differentiation.
Why These Industries Rely on Ultrasonic Cu-Al Welding
These industries use copper, aluminum, and their combinations extensively. Fusion welding of Cu-Al easily forms brittle intermetallic compounds (IMC) that cause failure; ultrasonic solid-state welding significantly suppresses IMC growth, making it the preferred choice for low-resistance, high-reliability connections.
FAQ (Ultrasonic Welding Applications)
Conclusion & Next
The application boundary of ultrasonic welding is expanding fast. In the previous article we covered its principles, equipment, and process parameters. Next, read Ultrasonic Welding Quality & Equipment Selection — how to judge a weld, troubleshoot underweld/overweld, compare with crimping/laser/resistance welding, and choose equipment.
For a complete high-voltage harness solution, see our HV Harness ultrasonic welding solution or contact us.
Part 2 of the Ultrasonic Welding Guide. Data from public sources and vendor data — please verify before quoting.