JHNSONIC / JINHENENG ULTRASONIC
ULTRASONIC WELDING · HV HARNESS
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JHNSONIC / JINHENENG ULTRASONIC
EV voltage platforms are climbing toward 800V, and harnesses must carry four to five times the current. We replace crimping with ultrasonic metal welding, fusing copper strands at the molecular level — lower resistance, higher strength, more reliable connections.
With current capacity up four to five times and wire size rising to 200mm², the "imperfect contact" left by crimping gradually becomes a heat hazard under high current — the connection process has to evolve.
The next generation of EV high-voltage harnesses is expected to carry four to five times the current of today's ordinary EV cables, with wire size climbing from 50mm² to 200mm² or more. As both cross-section and current grow, conventional connection methods start to struggle.
Cables and terminals are currently joined by welding, crimping, or mechanical connection. Crimping — mature, stable, and suited to mass production — has long been the mainstream choice, but crimped copper strands remain individual conductors with imperfect contact between them. Over time, contact resistance can gradually increase, the joint heats up, and energy losses grow. Conventional welding, meanwhile, suffers from high energy consumption, inconsistent performance, and pollution.
No external heat — 15–20kHz high-frequency vibration scrubs away oxide layers, bonding the metals metallurgically right at the interface, all in under a second.
Ultrasonic welding is a solid-state joining technology. The generator converts line power into high-frequency, high-voltage AC; the transducer turns it into 15–20kHz mechanical vibration through piezoelectric ceramics; the welding horn then delivers the vibration to the workpieces, forming a metallic bond at the weld interface under vertical pressure.
When welding harnesses, the high-frequency vibration scrubs oxide off each individual strand, creating metallurgical bonds between the twisted wires — conductivity close to a single continuous piece of metal. The whole weld cycle typically takes less than a second.
Low resistance, high strength, speed, copper-aluminum capability, no flux — five advantages, all backed by measured data, not marketing copy.
On a 70mm² harness, ultrasonic welds show an initial resistance of just 1–3μΩ; in broader testing, contact resistance can fall below 0.1mΩ. Such low contact resistance avoids resistive heating, eliminating the risk of local overheating and joint burn-out.
With no external heating and no residual stress, joints achieve better tensile and fatigue performance. Test data shows that raising weld energy from 5kJ to 11kJ lifts joint tensile force from 2616N to 6650N.
Each weld completes in 0.1–2 seconds, with energy use well below conventional thermal welding.
Beyond like materials, dissimilar metals with very different properties — such as copper and aluminum — can also be welded.
No flux, solder, or other consumables, and no irritating fumes — friendlier to both the environment and operators.
Fast chargers run 250A+ and their plugs see constant daily mating cycles — resistance must stay stable and welds must hold. Ultrasonic welding delivers both, and cuts three costs at once.
Advantages only matter when they land in production. Take DC fast chargers: operating current can exceed 250A, and the charging plug endures frequent daily mating cycles and vehicle-side tugging — two hard requirements for every connection point: stable resistance, and welds that hold.
The contact resistance of crimped joints grows over time, and under sustained high current the resulting heat is a real hazard. Ultrasonic welding fuses metals at the molecular level, keeping temperature rise in check and extending equipment life.
Metallurgically bonded welds withstand frequent plug cycles and the vibration and stress of driving — the 6650N tensile figure above is the proof. For manufacturers, that translates directly into lower after-sales repair costs.
On materials: no solder, flux, or shielding gas, and terminals can be simplified — swap crimp wings for weld pads, drop copper terminals and plastic housings, and tooling costs follow. On energy: as a cold-welding process, energy is released only at the instant of welding — no preheating, no holding temperature.
Aluminum conductors weigh only 1/3 as much as copper and cost 60% less — a practical substitute while copper prices stay high. But conventional processes tend to form brittle intermetallic compounds when joining copper to aluminum, causing joint failure. Ultrasonic welding joins Cu-Al reliably, letting manufacturers control cost without giving up performance.
Ultrasonic welding equipment integrates easily into automated lines, and the weld process itself can be automatically controlled. Semi-automated setups save 3–5 operators, so doubling orders doesn't mean doubling headcount.
One is a mechanical interlock where strands stay individual; the other is a metallurgical bond at the interface, fusing metal into one — on interface density, long-term electrical stability, and total cost, ultrasonic welding wins across the board.
Higher-power, smarter machines, accelerating domestic substitution, maturing standards — China's market is expected to top 12 billion RMB in 2026.
For large cross-section harnesses above 50mm², the industry has shipped 20kW high-power ultrasonic welding systems, and the latest generation welds up to 200mm².
Welding machines now routinely capture pressure, temperature, and amplitude in real time for quality traceability and early warning, and some bring AI in for live monitoring and control.
In high-voltage harness scenarios such as EVs and charging stations, domestic brands have visibly gained market share.
The commonly used welding standard is the US standard USCAR-38, which defines test methods and performance requirements for ultrasonic wire-to-terminal metallurgical bonds, including tensile, peel-strength, and environmental-resistance tests. Domestic harness production and inspection mainly follow QC/T 29106—2014, Technical Specifications for Automotive Wire Harnesses.
The shift from crimping to ultrasonic welding is driven by the upgrade of the vehicle's electrical system: higher voltage, higher current, and rising demands for connection consistency and stability. Ultrasonic welding is backed by measured data on resistance, strength, and cost — and that is exactly why it is spreading across high-voltage harness manufacturing.