When unwanted gas from a material gets released, outgassing occurs. This is a challenge that hinders high vacuum deposition, or the process utilized to apply thin layers of material to an object’s surface.
In a vacuum chamber, outgassing happens when gases become expelled from object surfaces in that chamber. More on this as you read on, plus:
- Vacuum chamber outgassing
- Why it is a concern
- Sources of outgassing
- Methods to reduce outgassing
- KeyLink’s vacuum plasma treatment systems
Overview of Vacuum Chamber Outgassing
Vacuum chambers are rigid enclosures that utilize vacuum pumps, which take charge to eliminate unwanted air and other gases. This then creates a low-pressure environment, or simply, the vacuum.
To create vacuum chambers or vacuum rooms, you should have an enclosure built from solid materials like stainless steel and pumps attached to the chamber, letting the atmosphere within this chamber be pumped out.
Vacuum chambers find compatibility in different industrial applications that include manufacturing, research, quality testing, food, and many other industrial areas.
So, what’s outgassing in a vacuum? Outgassing in vacuum chambers happens when previously trapped gases within materials get released upon low pressure exposure. This happens due to various mechanisms, from desorption to permeation, which changes in temperature and pressure influence.
Outgasses introduce contaminants into your vacuum chamber, obviously affecting the smooth-sailing operations in your enterprise. The presence of materials with low outgassing rates is necessary to immediately resolve outgassing. You must also conduct rigorous testing to ensure everything complies with the standards of the industry.
Outgassing vs. Offgassing
While both outgassing and offgassing involves gas release from your materials, their general difference is that, they occur in entirely different conditions.
The former typically pertains to the release of gas in a vacuum or environments with intense temperature. For instance, in the aerospace industry.
On the other hand, the latter, offgassing, transpires at room temperature and often normal atmospheric issues. This term is used to associate with indoor air quality problems from household items like paints and furniture, releasing elements, such as volatile organic compounds that can harm your health.
Degassing vs. Outgassing
Their differences lie in their focus and application. While outgassing is the release of gas from solid materials in vacuum systems, in order to remove harmful substances, such as in manufacturing electronics, degassing removes dissolved gases from liquids, not solids. This then enhances the quality of products, particularly in the food and pharmaceutical industries.
Both degassing and outgassing are necessary to ensure the integrity and safety of materials, but individually work under distinct conditions.
Why It Is a Concern
There are several reasons why outgassing in your vacuum chambers is a major concern:
Contamination
The unwanted release of gases, as well as other volatile substances, causes contamination to vacuum environments. This can affect the good performance of sensitive equipment. It can challenge the semiconductor manufacturing, optics, or space simulation industries.
Pressure Changes
Aside from nasty contamination, outgassing also tends to boost pressure inside the vacuum chamber. This can disrupt the functioning of your instruments and equipment that rely on certain pressure ranges.
Vacuum Degradation
Since outgassing may also introduce additional gases into the chamber, the purity of the vacuum is diminished. This compromises the efficiency of processes that depend on high-quality vacuum, such as manufacturing semiconductors and electron microscopy. Outgassed gases may also interact with other materials inside the chamber at the wrong time, leading to chemical reactions and other undesired side effects.
Sources of Outgassing
There are four highlight sources of this phenomenon:
- Vaporization: Matter molecules releasing from their surface.
- Desorption: Gas molecules already absorbed on the surface get released due to heat, electric, or optimal stimulation.
- Diffusion: Gaseous molecules releasing from most parts of the material.
- Permeation: Air atoms entering from out of the vacuum chamber into it.
Proven Methods to Reduce Outgassing
Fortunately, there are ways you can execute to reduce outgassing and its ill-effects. Let’s go into these approaches through this chart:
| Approach | Material | Application | Not Effective For: | Vacuum Level | Duration |
| Active Coating | Hafnium, Zirconium, Titanium, Palladium, Vanadium, and combinations | H2, H2O, CO, O2, N2, and small spaces | Hydrocarbons, inert gas, and continualoperations | Outgassing reduced to <10−13 with no bake | Based on size |
| Air Bake | Air | H2, CO, CO2, CH4, stainless steel, andaluminum | Cadmium plating, plastic, and components sensitive to temperature | Reduces outgassing of H2 to <10−14 | Two to 400 hours |
| Blowing | Air, nitrogen, or other dry inert gas | Gross or fine contaminants, plus loosely bound heavy molecules | Grease | < 30 min | |
| Chemical Treatment | H2O, HCl, HNO3, or HF | Rough surfaces | Order of magnitude reduction in outgassing rate | < 30 min | |
| Glow Discharge | Ar/5-10%O2, Ar, O2, N2, and H2 | C or O based molecules, large surface areas, and reconditioning after atmospheric exposure | Huge components | Reduces outgassing rate 13 times | Around two hours |
| Passive Coating | Si, TiN, BN, Al2O3, and ZrO3 | H2 from metals, CO, CO2, and H2O | H2 outgassing reduction by 0.1 to 100 times | Based on size | |
| Reactive Gas | O2 or NO for oxidation, and H2 or NH3 for reduction | Hydrocarbons | May form unwanted oxides | Outgassing rate reduction by 50 percent | 30 minutes to two hours |
| Vacuum Bake | H20, metals, and UHV | Components sensitive to temperature | H2 outgassing reduction to <10 to 14 | Two to 400 hours | |
| Vapor Degrease | Heated solvent | Gross or fine contaminants, and loosely bound heavy molecules | Inaccessible and large areas | Order of magnitude reduction in outgassing | Less than an hour |
| Wash | Hot water or solvent, and detergent | Gross or fine contaminants | Grease | Pressures >10-3mbar | Less than 30 minutes |
Conclusion
Outgassing is not something you want to encounter if you’d like your industry to keep operating smoothly. It is the unwanted and hindering release of gases that may mainly introduce contaminants into your vacuum chamber. However, there are methods you can implement to solve this issue, such as washing, chemical treatment, and glow discharge, among a wide range of others.
Another effective method to address this is by using vacuum plasma treatment systems, such as those by KeyLink. The brand’s state-of-the-art equipment won’t just resolve contamination, but also work toward surface activation, surface etching, and wettability enhancement. Get to know how you can acquire this technology by connecting with their team today.
