Troubleshooting guide
Ultrasonic Wire Welding Defects: Causes and Corrective Actions
Troubleshoot weak wire splices, cut strands, excessive flash, incomplete bonding, unstable weld energy, tool marking and conductor contamination.
Engineering review: 2026-08-28
Ultrasonic welding creates a solid-state bond through pressure and high-frequency motion. A weak or unstable splice cannot be corrected reliably by changing energy alone; material preparation, tooling and joint geometry must be controlled together.
Symptom and cause map
| Symptom | Possible causes | First checks |
|---|---|---|
| Low pull or peel result | Low energy, poor placement, contamination, worn tool | Material surface, strand lay and tooling condition |
| Incomplete bonding | Insufficient motion transfer, low pressure, oversized joint | Weld signature and actual gathered cross-section |
| Cut or broken strands | Excess energy, pressure, time or sharp tooling | Weld thickness and tool edges |
| Excessive flash | Too much material displacement or poor containment | Anvil width, joint volume and recipe |
| Insulation damage | Strip length too short, heat or tool contact | Conductor exposure and fixture position |
| Weld energy drifts | Material variation, tool wear, placement or pressure instability | Lot, tool count and consecutive weld signatures |
| Surface marking is uneven | Misalignment, debris or tool wear | Sonotrode/anvil contact pattern |
Match the process window to actual cross-section
Use the total gathered conductor cross-section and material construction, not only the largest individual wire. The WM-711 ultrasonic wire welding machine, WM-717S splice station and WM-718 high-power splicer cover different published process ranges. A joint near a range boundary requires an actual material trial.
Controlled correction sequence
- Preserve failed and accepted welds, wire lot, recipe and tool identity.
- Confirm strip length, strand count, material and surface condition.
- Inspect sonotrode, anvil, alignment and fixture cleanliness.
- Compare weld signature and finished geometry with the approved sample.
- Change only one validated parameter at a time.
- Re-run consecutive joints using the production loading method.
- Re-approve dimensions, mechanical result, electrical result and required sections.
The EV harness and battery pack assembly guides show where ultrasonic splices enter production. Public measured evidence is limited to the case library. For a joint-specific diagnosis, send the splice drawing, wire samples, failed welds and recipe record.
Questions engineers ask
What causes low strength in an ultrasonic wire splice?
Possible causes include insufficient energy or amplitude, incorrect pressure, unsuitable weld time, contaminated conductors, poor strand placement, worn tooling or a splice cross-section outside the validated process window.
Why can increasing weld energy make the splice worse?
Excess energy can cut strands, create flash, over-thin the weld, damage insulation or accelerate tool wear. Confirm material preparation, pressure, tooling and placement before changing one validated parameter at a time.
How should an ultrasonic wire weld be approved?
Use the product drawing and agreed process specification to define dimensions, visual condition, peel or pull method, electrical resistance and any cross-section or environmental tests. Preserve the machine recipe and tooling identity with the sample.