Plasma can be defined as an ionized gas, which is a gas that contains free electrons, free ions, and occasionally free radicals. The plasma state can be produced for industrial application inside vacuum plasma chambers.
In these chambers, the operating pressure is below the atmospheric pressure, for example, vacuum plasma chambers can work at 0.001 bar, which is times less than the atmospheric pressure of 1 bar.
When plasma is created in these conditions, its properties can be exploited for a number of different industrial applications, such as plasma surface modification, plasma polymerization, enhanced surface bonding, plasma etching of electronics, plasma cleaning, and many more.
Plasma technology usage has been growing since the s, and now it is used in many different industries like the semiconductors manufacturing or the automotive industries.
A vacuum plasma system is an industrial piece of machinery that can produce plasma inside a vacuum plasma chamber. The engineering of the plasma chamber is such that the properties of the generated plasma can be directed to fulfill a specific process requirement.
There are various types of equipment that can produce industrially useful plasma. Additionally, there are numerous different solutions depending on the process and organizational requirements. These solutions can be categorized as Batch Plasma Systems, Inline Plasma Systems, or Strip Plasma Systems.
It is best to consult an expert to properly choose which system is most adapted for one’s application.
Vacuum plasma treatments work more or less with the same process steps.
The first step is to introduce the parts to be treated into the plasma chamber. Then the plasma chamber is evacuated from the atmospheric air in the step called pump down. Once the selected vacuum level is reached, a process gas is introduced into the plasma chamber, these gases are typically Argon, Oxygen, or Hydrogen.
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Once the process pressure is stabilized, the process gas is ignited into a plasma.
This plasma can be used, for example, to clean contaminations on the surface of an object if one is seeking plasma cleaning. Other applications may require this plasma treatment to increase surface adhesion or bonding strength.
There are three common types of vacuum plasma processes. See below for a description of each type and how plasma performs the process.
Plasma cleaning in a vacuum plasma system is a process in which unwanted organic contamination is removed from the surface of an object. The plasma can remove the contamination by breaking it down into small molecules that can evaporate from the object’s surface at the given vacuum level. This cleaning process extracts and removes contaminations without leaving any traces.
It is non-toxic, unlike other chemical cleaners, and will even reach areas where other solvents are unable to be used. This is a powerful tool to ensure objects are cleaned entirely of organic contamination.
The plasma process can be configured to improve adhesion or bonding strength between surfaces that normally have trouble bonding together. This is typically due to the fact that primary or secondary bonds can occur on different materials surfaces only if chemical compatibility is guaranteed.
Plasma can modify the surface only of the materials that need to be bonded, allowing good chemistry to happen between them without impacting the bulk properties of the materials.
In this process, the plasma ions and radicals, being reactive species, will interact with the object's surfaces and chemically modify them.
The objective of plasma polymerization is to produce polymers and direct use them to coat objects inside the vacuum plasma chamber.
During plasma polymerization, a monomer is introduced into the vacuum plasma chamber while the plasma is ignited. This allows the monomer to be activated and be able to react with itself in a self-sustained recursive reaction to produce longer and longer molecules, i.e. polymers.
The polymerization happens in a clean and controlled environment
The polymer films that are produced will coat evenly oddly shaped substrates thanks to the plasma medium
Tuning the plasma parameters can lead to polymer films with different properties (chemical composition, thickness, and surface morphology)
The process can be done at low temperatures allowing, therefore, the coating of temperature-sensitive devices
The process is a dry process, i.e., it does not use any solvents, reducing the environmental impact of the polymerization process
The adhesion between the polymer and the target objects is quite strong as the plasma activation process happens at the same time as the polymerization. This leaves the target object's surface extremely clean and active and ready to bond with the created polymer.
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