Ultrasonic Welding FAQ

Ultrasonic Welding FAQ

How does ultrasonic metal welding work?
Parts to be joined are held together between the ultrasonic horn and anvil. They experience ultrasonic vibrations of 20 to 40 kHz, depending upon application. Vibration of the horn causes the parts to scrub together (in shear) that removes surface contaminants to expose bare metal areas. The materials’ atomic structures then co-mingle to create a strong, surface molecular, solid-state bond that is clean and has low electrical resistance. These properties together make the process ideal for electronic applications and more.
What strength is expected from materials joined ultrasonically?
Usually, the bond created is as strong or stronger than the parent materials.
What metals can be joined ultrasonically?
Generally, non-ferrous metals: aluminum, silver, gold, copper, brass, nickel and alloys of these materials. Applications include battery foil/tab welding, wire splicing, wire termination, spot welding, seam welding and copper tube sealing for the refrigeration industry.
What about steel components?
Welding to iron, steel and stainless steel is not recommended because they are harder than non-ferrous metals. The surface structures are too dense and do not allow the transfer of materials for consistent bonding. The parameters required would be more aggressive with heat build-up, resulting in increased tool wear. While bonding may occur, consistent weld strength is difficult to achieve.
What about dissimilar materials such as aluminum to copper?
Ultrasonic welding works well for dissimilar metals because the process is the same whether the materials are similar or not. Examples include battery nickel/copper tab/foil welding, silver-plated or copper stranded wire to nickel-plated copper or brass terminals, copper pads to aluminum heat sinks, and precious metal contacts to contact arms, among others.
What about plated parts?
It depends upon the plating. Tin plating inhibits the bonding process, acting more like a lubricant. The tin heats up and may actually reflow. The parts slide over each other rather than scrubbing against each other. Heat builds up which has a negative effect, especially on wire strands, as they become brittle and usually break. Silver and gold plating is different. These are more compatible because they seem to move away from the weld area or are able to be scrubbed through to get to the base metal. Applications with these platings include stranded wire splicing and tipping, wire termination to plated terminals or lead frames.
What are weld size and material thickness restrictions?
1/4” square for 40 kHz and up to 1/2” for 20 kHz. The material can be of any thickness on the anvil side of the weld as long as it can be held stationary either on the anvil or by clamping. On the horn side, material can be up to 1/8”, provided sufficient power is available from the controller.
What amount of tool wear is expected?
This depends upon the materials being joined. Harder materials that require more aggressive parameters result in higher tool wear versus softer metals that require less aggressive parameter settings.
Can tooling be reworked for extended use?
Many times a horn or replaceable tip can be reworked (reknurled) one time, more if the rework allows the tool to remain to print or weight specifications. Stick anvils may be reknurled as long as they can still be clamped in position in the tool support or fixturing and hold the part as required.
Can the same tooling be used for different applications?
Most tooling is custom made for specific applications, especially the fixturing. The knurl patterns on the horn and anvil are specified according to material thickness and weld area requirements as well as part configurations. Some tooling combinations may be used for situations other than the original application, but may need modification.
How much training is needed for the operation of our new machine?
Our machines are very easy to operate and do not require any certification. Tech-Sonic provides training when installing the machine and application. Training includes operations of the controls, how and when to change tooling, parameter settings and place multiple application setups in the preset menu if needed.

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