Things are moving away from plain old iron soldering – http://www.amazon.com/iCooker-Soldering-Iron-Watt-Solder/dp/B01774KARE. Ultrasonic soldering is gaining popularity die to its ability to solder onto materials that were previously very hard to solder such as aluminum and steel and those that were totally unsolderable such as glass. Materials such as steel have strong oxide layers thus making the conventional iron tip method inefficient for soldering. To overcome this, people have been using strongly acidic flux components to reduce the oxide layer. This is however facing a challenge from environmental conservationists. This is where ultrasonic soldering comes in.
Ultrasonic soldering relies on an effect known as cavitation. This arises when ultrasonic waves are applied to liquids. This effect releases a lot of energy within a very short time. This energy is used to remove the oxide layer from these elements that have very low solderability such as magnesium. Once the oxide layer is removed, there is no further need of flux application since the metal becomes fully solderable.
The tip of an ultrasonic soldering iron solders and applies the waves simultaneously. Once the cavitation gets rid of dirt, the oxide later and other impurities, the solder is applied and a layer of alloy is formed through an action spreading of molten solder. In soldering on glass, the cavitation causes the metal in solder to use the oxygen molecules in glass as a bonding mechanism. Glass in itself is not solderable since it’s formed in an oxidation process. By incorporating the oxygen molecules, the metal creates a bond that is only possible through the process. However, the method still hasn’t achieved widespread use probably due to the technicalities and equipment involved. In future however, and with the current environmental trends, it may very well represent the future of soldering.