UV Radiation / Ozone
UV-O3 cleaning is generally effective for removing organic contaminants, though it may be ineffective for removing inorganic contaminants. Therefore, as preliminary cleaning, inorganic contaminants must be removed in advance using pure water, solvents, or the like before UV-O3cleaning is conducted.
Principle of UV-O3 Cleaning
The principle of UV-O3 cleaning is as follows: organic compounds are converted into volatile substances (e.g., water, carbon dioxide, nitrogen) by decomposition by ultraviolet rays and by strong oxidation during the formation and decomposition of O3 and are removed from the contaminated surface.
The major wavelengths of the ultraviolet rays radiated from a well-known low-pressure mercury vapor lamp are 184.9 nm and 253.7 nm. When atmospheric oxygen O2 is irradiated with ultraviolet rays with a wavelength of 184.9 nm, the oxygen absorbs the ultraviolet rays to form O3 by the following reaction:
Ultraviolet rays with a wavelength of 189.4 nm Ozone O3 irradiated with ultraviolet rays with a wavelength of 253.7 nm absorbs the ultraviolet light to decompose O3. During the process of formation or decomposition of O3, atomic oxygen O having a strong oxidizing ability is generated.
Contaminants Removable by UV-O3 Cleaning
- Cutting oils
- Mixtures of beeswax and pine resin
- Lapping agents
- Vacuum-pump oils
- Silicon diffusion-pump oils
- Silicon vacuum greases
- Soldering fluxes
- Human sebum
- Contaminants adsorbed during long-term air exposure
- Carbon thin films formed by vacuum evaporation
Frequently Asked Questions
How does UV/ozone cleaning work?
Organic compounds on the surface are converted into volatile substances such as water, carbon dioxide and nitrogen. Ultraviolet at 184.9 nm is absorbed by atmospheric oxygen to form ozone, while ultraviolet at 253.7 nm is absorbed by that ozone and decomposes it. During both the formation and the decomposition of ozone, atomic oxygen with strong oxidizing ability is generated, and that is what removes the contamination.
What contamination does UV/ozone cleaning remove?
Documented removable contaminants include cutting oils, lapping agents, vacuum-pump oils, silicon diffusion-pump oils, silicon vacuum greases, soldering fluxes, mixtures of beeswax and pine resin, human sebum, carbon thin films formed by vacuum evaporation, and contaminants adsorbed during long-term air exposure.
Can UV/ozone cleaning be used on its own?
Generally not. It is effective on organic contaminants but may be ineffective against inorganic ones, so inorganic contamination must be removed in advance with pure water, solvents or similar before UV-ozone cleaning is carried out.
Which light source is used?
The standard source is a low-pressure mercury vapor lamp, whose major emitted wavelengths are 184.9 nm and 253.7 nm -- the two wavelengths that respectively form and decompose ozone, so a single lamp drives both halves of the reaction.
