Ultrasonic Welding

Ultrasonic welding joins thermoplastics and thin metals using high-frequency vibration and pressure, creating fast, clean, repeatable bonds without adhesives or added filler.

Overview

Ultrasonic welding uses high-frequency mechanical vibrations and clamping pressure to create solid-state bonds in thermoplastics and thin metals, typically in under a second. The process generates localized frictional heat at a designed joint feature, causing material to melt or soften and fuse without adding filler metal, fasteners, or adhesives. It is highly repeatable, easily automated, and well-suited to cleanroom or low-particulate environments.

Use ultrasonic welding for high-volume assemblies with compatible materials, tight leak or strength requirements, and limited tolerance for contamination or cosmetic damage. It excels on small to medium-sized parts such as housings, filters, and battery components where you can design in proper joint geometry. Tradeoffs: parts must be ultrasonically weldable materials, joint access is required, and joint design is critical. Very thick sections, large weld areas, and highly filled or brittle plastics can be challenging and may need process development or alternative joining methods.

Common Materials

  • ABS
  • Polycarbonate
  • Polypropylene
  • Nylon 6/6
  • PET
  • Copper sheet/foil

Tolerances

±0.002" to ±0.005" on mating weld features with good tooling

Applications

  • Automotive sensor and electronics housings
  • Medical device enclosures and fluid reservoirs
  • Disposable filters and membrane housings
  • Battery tabs and small busbars
  • Consumer electronics plastic enclosures
  • Blister packs and sealed packaging

When to Choose Ultrasonic Welding

Choose ultrasonic welding when you have compatible thermoplastics or thin metals, need fast cycle times, and want a clean, consumable-free process. It is ideal for high-volume or automated assembly of small to medium parts where you can control joint geometry and part tolerances. Use it when you need strong, repeatable, often hermetic joints without adhesives, screws, or flux residues.

vs MIG (GMAW)

Pick ultrasonic welding over MIG when joining thermoplastics or very thin nonferrous metals where arc welding would burn through or is impossible. Ultrasonic is also better when you need clean, flash-free, small-format welds suitable for automation and tight assemblies, with no spatter, shielding gas, or post-weld cleanup.

vs TIG (GTAW)

Choose ultrasonic over TIG when you need to join plastics or delicate, thin metal tabs and foils at high speed with minimal heat-affected zone. Ultrasonic welding is more suitable for small precision assemblies, enclosed housings, and high-volume production where TIG’s manual nature, heat input, and filler requirements are drawbacks.

vs Stick (SMAW)

Use ultrasonic welding instead of Stick when you are assembling small components, plastics, or thin-gauge metals in a controlled production environment. Ultrasonic provides far better precision, aesthetics, and speed for mass production, while Stick is more suited to structural, heavy-gauge, and field work.

vs Resistance Welding

Select ultrasonic welding when you need to join plastics or mixed-material stacks where traditional spot welding cannot be applied. For thin nonferrous metals and battery tabs, ultrasonic can produce strong bonds with lower current demands, less marking, and finer control of heat input than resistance welding.

vs Laser Welding

Prefer ultrasonic welding when parts are opaque plastics, joint fit-up is less perfect, or you want a more forgiving, lower-capital process. Ultrasonic often wins for thicker joint lines, higher weld forces, and applications where you can design in energy directors rather than relying on laser transparency and precise beam alignment.

Design Considerations

  • Design dedicated weld joints such as energy directors, shear joints, or tongue-and-groove features instead of trying to weld flat-to-flat surfaces
  • Hold mating joint features to tight, repeatable tolerances and control flash traps so small dimensional shifts do not compromise weld strength or sealing
  • Keep weld areas free of paint, mold release, labels, and contamination; specify any required cleaning steps on the drawing or work instructions
  • Provide rigid support surfaces under the weld joint in the fixture design to prevent part flex and inconsistent welds
  • Avoid overly thick sections and large continuous weld paths; break long welds into segments and keep walls uniform where possible
  • Call out required weld strength, leak rate, and cosmetic zones so the supplier can select horn design, amplitude, and process parameters correctly