How Ultrasonic Soldering Works

Ultrasonic soldering is a flux free method which is considered more eco-friendly comparing to conventional soldering methods. Instead of chemical agents, surface oxide layers are removed from the soldered surface by using vibrations and a cavitationphenomenon.

Ultrasonic soldering technology is different from ultrasonic plastic welding, in which the vibrations generate heat to melt the parts being joined. Ultrasonic soldering uses the same basics as the ultrasonic cleaning process where the vibrational energy induces cavitation in the water bath or the cleaning solvent. Immersed parts are scrubbed clean by a strong erosive effect of collapsing vapor bubbles in the liquid medium.

During the ultrasonic soldering process, heat from a separate energy source melts the solder before vibrational energy is applied. Molten solder then acts as an acoustic transfer medium for the ultrasonic vibrations. When high-frequency vibrational energy is applied to the molten solder, controlled acoustic cavitation is induced at the tip of the soldering tool in order to break up and disperse surface oxides. The cavitating micro bubbles burst, cleaning all surfaces and allowing the liquid solder to wet and bond pure metal.

Vibrations also ensure that the solder joint is free of voids, vibrational energy forces the liquid solder into crevices and micropores in the substrate. It helps to seal the parts and increases the surface area to which the solder can bond. Ultrasonic vibrations also press gas bubbles out of the liquid solder therefore this method makes joints suitable for high vacuum applications where hermetic seals are required.

Ultrasonic soldering allows for joining dissimilar materials and can be used for materials that are difficult to solder with conventional methods. Because it requires no flux, users save time and costs of cleaning flux residues while reducing corrosion and increasing the durability of soldered joints.
Ultrasonic soldering method can be easily adopted to manual soldering with a handheld ultrasonic soldering iron or even mass production ultrasonic soldering machine.