On almost all products, whether recently manufactured or from storage, there are layers of foreign substances. Though often very thin and invisible, they considerably impair further production steps or are the cause of poor quality in further processing:
The origin of these contaminations is varied:
- release agents (oils, waxes, silicones, greases, hydrocarbons in general)
- greases or oil mists deposited post-production, fingerprints
- water film from humid air
- weathering and oxide layers (also polymer decomposition by UV light)
Conventional cleaning processes:
- wiping, extracting, blowing off
- wiping with solvents (water, organic solvents)
- etching with acids or leaches in an immersion bath
In many cases, achieving adequate results is impossible with these procedures:
- Wiping cannot reach corners, cracks and cavities
- After immersion, cleaning liquid saturated with the substance to be dissolved may stand in cracks and cavities and no longer clean effectively.
Wet chemical cleaning processes also have the following considerable disadvantages:
- Storage, transport, use and disposal of toxic and environmentally harmful solvents and etching substances is expensive and labour-intensive.
- Solvents must be removed after cleaning, components must be dried.
- The foreign substances are not removed completely so that several cleaning runs with different methods must be applied
The material removal rates in plasma cleaning are much lower than in wet-chemicals processes. Accordingly, an initial wet-cleaning process is advisable for heavy contamination. The special benefits of dry cleaning by means of a plasma treatment are on the one hand that they do not use any liquid chemicals at all, the cleaned components are immediately ready for further processing. On the other hand, low-pressure plasma reaches even into the narrowest cracks and gaps. Choose from the following cleaning processes:
Removal of hydrocarbons in the oxygen plasmaRemoval of all oils, greases, waxes, silicones, release agents
Decomposition of oxide layers in hydrogen plasma.
Removal of almost all substances by physical etching (ion etching, micro-sandblasting) in the argon plasma.Non-selective process which removes almost all substances which cannot be removed by chemical action in the hydrogen plasma and oxygen plasma.
For more details, see ⇒ Plasma cleaning.
If plasma treatment is continued after completion of cleaning, non-polar component surfaces are activated to make them wettable.
(⇒ Plasma activation) Furthermore, the component surfaces themselves will be etched when exposed to the plasma effect for a long time
(⇒ Plasma etching)