What Does Dewetting Mean?
Dewetting is a phenomenon where a thin film of liquid ruptures on a substrate, which leads to droplet formation. It is the opposite of the process of spreading, which is a liquid spreading on substrates.
Dewetting, along with spreading are essential processes for various industrial processes like:
- Protective coating
In most cases, dewetting is undesirable as it deteriorates the thin film.
Corrosionpedia Explains Dewetting
Dewetting is a serious problem with component parts, such as in solder joints or pads. When dewetting occurs, solder fails to adhere to parts. Some of the underlying factors for this are contamination and corrosion, along with extremely high temperatures.
Although it is a rare phenomenon, dewetting in systems like solder joints may occur during the manufacturing process and also during repair. In such cases, the lead component on the part can produce a favorable mechanical connection to its pad. The contact can become intermittent, and this results in the lead popping off. Typically, dewetted joints present an irregular appearance and may look lumpy due to outgassing.
Under magnification, conductive debris such as leads that have been clipped off and solder balls due to previous repairs may be observed on printed circuit boards (PCB). The site may have holes and tarnished pads. A pad that has gone through dewetting is still salvageable if bare copper is used to clean it.
The dewetted portions in any areas other than solder joints can be prevented through the following methods:
- Removing tarnish and corrosion
- Preventing chemical contamination
- Thorough cleaning
Surfactants can also be used, as these have a significant effect in terms of controlling dewetting. Surfactants can significantly increase the spreading coefficient while reducing interfacial tension. As more molecules of the surfactant reach the surface, less dewetting can be found in the system.