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Vacuum Plasma Cleaning: What Is It And How It Works

Fighting organic matter through the use of plasma at the nano-level sounds like something straight out of science fiction. However, with 21st-century technology, scientists have been able to harness the new plasma cleaning process for everyday usage.

In general, plasma cleaning is an environmentally friendly, cost-effective, and powerful method of removing unwanted contagions from objects. Let's take you through all you need to know about vacuum plasma cleaning and whether it's right for your needs.

What is Plasma Cleaning?

Plasma is usually defined as the fourth state of matter. Even though everyone understands the first three states of matter being: solid, liquid, and gas, plasma is often not well understood. To use a simple definition, plasma is an ionized gas. That is a gas that contains free electrons and positive ions.

Plasma cleaning involves using plasma to efficiently remove contamination from the surface of an object. It is considered an environmentally safe process as it doesn’t release any harmful chemicals in the environment in substantial quantities. It can easily remove organic matter as the plasma cleaning process is able to break down the organic bonds of the surface contamination that needs to be removed.

The reason plasma cleaning is rising in popularity is due to its high effectiveness and its advantages over traditional industrial cleaning methods. For example, chemical cleaning can remove unwanted contaminations but leaves behind residues that will alter the surface. Plasma cleaning, on the other hand, leaves the treated surfaces completely exposed and does not leave any form of residue.

Plasma cleaning has major advantages in that it is entirely non-toxic to the user, it does not pollute, and it leaves behind absolutely no trace. Due to the nature of plasma cleaning, it will even reach areas that solvents are unable to.

How does Plasma Cleaning Work?

The objects that need to be cleaned are placed into a vacuum chamber. The vacuum chamber is typically a metal enclosure where all the air is pumped out with the help of a vacuum pump until the desired level of vacuum is reached. For plasma cleaning applications, the vacuum level is typically between 0.1 - 1.0 bar (75 - 750 mTorr).

After the correct vacuum is established, one or more process gases will be introduced in the plasma chamber, these gases will be the starting materials to generate the plasma (the ionized gas).

To generate the plasma, a current source is used. This source can be

  • DC (Direct Current),

  • MW (Microwave at 2.54 GHz), or

  • RF (Radio-Frequency typically at 13.56MHz)

The current source is able to break down and ionize the process gas generating the plasma.

The plasma, being highly reactive, will start to interact with the objects’ surfaces and especially with the contamination breaking down its chemical bonds. The by-products of this physicochemical reaction are smaller organic molecules that can be vaporized at the operating vacuum pressure of the process.

This means that these molecules will leave the objects’ surfaces and go into the gas phase immediately after. They will be removed by the gas flow through the vacuum pump exhaust.

In simple terms, plasma cleaners vaporize the contamination that should not be on an object through the help of plasma. This leaves behind no residue, chemicals, or toxicity.

3 Types of Plasma Cleaning Processes

1. Oxygen Plasma Cleaning

The oxygen plasma cleaning process involves generating plasma starting from pure oxygen gas. The characteristic of oxygen plasma is that it is highly oxidative.

This means that it will easily break down organic contaminants as the plasma works with chemical reactions similar to those involved in combustion.

Being highly oxidative, the oxygen plasma should not be used when the objects to be cleaned are made out of sensitive materials like copper or silver or, in general, when the object should not have an oxidation layer after the plasma cleaning process.

2. Hydrogen Plasma Cleaning

The hydrogen plasma cleaning process involves generating plasma starting from pure hydrogen gas. The characteristic of hydrogen plasma is that it is highly reductive, which is the opposite effect of what oxygen plasma would do.

Although hydrogen plasma produces a reducing environment, it can still be used to remove organic contaminants. The chemistry involved will be different, but the overall mechanisms are the same: hydrogen plasma will produce smaller molecules that will evaporate from the objects’ surface and be removed by the gas flow.

An important application of hydrogen plasma is oxide removal. Since the hydrogen plasma will promote reduction reactions it is able to reverse the oxidation reactions that lead to the presence of surface oxides.

In oxidized metals, this means that after the hydrogen plasma process, the metal will be brought back to its pure form, exposing its surface directly to the environment.

3. Argon Plasma Cleaning

Argon plasma cleaning is a bit different than oxygen or hydrogen plasma as the argon plasma does not chemically react with the organic contamination but simply exchanges energy through inelastic collisions.

Argon is a heavy element compared to carbon, oxygen, or nitrogen, the components of organic contamination. Argon-positive ions present in the argon plasma can be accelerated and targeted to the organic contamination breaking it down into smaller molecules. These molecules, like in the other processes, evaporate and are removed by the process gas flow.

The argon plasma cleaning process, with its small variants, is the most used process in the semiconductor and automotive industries. The argon plasma process produces outstanding results in terms of adhesion.

Plasma Cleaning Equipment and Resources

Many people struggle to picture what plasma cleaning would even look like. Luckily, we have resources that help us envision the process. SCI Plasma has expertly written guides in addition to its plasma cleaning equipment.

Curious people and prospective buyers can peruse plasma cleaning equipment solutions which include vacuum process technology such as Batch Plasma, Inline Plasma, or Strip Plasma.

Regardless of one’s specific needs, there will be a specialized solution. Because there are so many different machines and techniques to achieve one’s goals, it would be best to consult an expert to discuss what the best path forward is. That way, a prospective client can get a specialized resolution for their precise issue.

Final Thoughts

Most cleaning materials will leave behind residue, which can be toxic for both humans and the environment, but this problem can be fixed through modern 21st-century technology.

Plasma cleaning offers a secure, environmentally-conscious, and efficient means of removing undesired materials from any object's surface. By employing plasma, the process breaks down oils and contaminants and removes them as gas, resulting in a cost-effective solution.


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