What is Plasma?

Plasma coating is the application of a nano-coating material onto a surface via a plasma.

The material is injected into the plasma via a jet nozzle. The plasma excites the coating material and this increases the coatings reactivity.

The plasma coating is then applied to the surface. Due to the excited nature of the coating, the material coverage is optimised and the bonding is improved.

The plasma coating process can be used to coat different materials like metals, glass, ceramics and plastics. It can be adjusted individually to the substrate.

These nano coatings can be made to be hydrophobic (water repellent) and hydrophillic (water absorbant) depending on your requirements.

Examples of plasma coating applications include:

  • Improvement of barrier characteristics of plastics for packaging
  • Improved paint application with long-term stability and resulting high flexibility in manufacturing
  • PT Release coatings, for injection molding tools, allow a high number of process cycles without the components having to be stressed with release agents that contain silicone.
  • PT Bond coatings assuring long-term adhesion in the adhesive joint.
  • Corrosion protection coatings that offer extremely high corrosion protection with long term resistance to corrosive electrolytes (especially for aluminum alloys) because of their good barrier effect

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How does Plasma work?

Plasma technology is based on a simple physical principle.

Matter changes its state when energy is supplied to it. Solids become liquid. Liquids become gas.

If additional energy is then fed into a gas by means of electrical discharge it eventually ionizes and goes into the energy-rich plasma state, the fourth state of matter.

Plasma is created.

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How can Plasma be used to improve the performance of the coating on the surface?

Plasma treatment can clean, activate or coat nearly all surfaces. These surfaces include plastics, metals, (e.g., aluminum), glass, recycled materials and composite materials.

This means the plasma process can be highly effective on many different products.

Plasma cleaning treatment can be used in two highly effective ways.

It could be used to:

  1. Clean the surface to be 100% contamination free. The surface will be free of residues and contamination.
  2. Activate the surface by changing the surface energy. This would allow easier bonding and better adhesion to the surface.

These properties make it a highly practical technique for improving the surface performance of a product.

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What are the typical plasma processes available for surface treatment?

There are traditionally three types of plasma treatment:

  1. Low-pressure plasma
  2. Corona treatment
  3. Atmospheric pressure plasma

Low-pressure plasma

These plasmas are generated in closed chambers in a vacuum (10-3 to 10-9 bar).

Corona treatment

Corona treatment (corona process) is a physical process involving high voltage and is mainly used for treatment of films.

Atmospheric pressure plasma

Atmospheric plasma is generated under normal pressure. This means that low-pressure chambers are not required.

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What are the advantages of plasma cleaning treatment?

  • Plasma cleaning can clean surfaces of the circuit board 100% to improve adhesion and surface energy of the product.
  • Many wet chemistry cleaning processes can be eliminated. Methods using cleaning chemistries, water processing and drying energy are unnecessary.
  • The significant improvement in adhesion enables the use of alternative conformal coatings and other chemical vapour deposition coatings (CVD) that may have difficulty adhering to circuit boards without the treatment.
  • The plasma process is a simple, safe and environmentally friendly technology.
  • The plasma process has inline capability.

As a result, plasma is in use in almost all areas of industrial manufacturing.

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How can plasma treatment help my conformal coating process?

Cleaning and conformal coating circuit boards for long-term protection has taken place for many years.

The reasons for doing this have always remained the same:

  • Improve the surface cleanliness of the circuit to protect against corrosion and the effects of contamination on the surface from the process.
  • Add the conformal coating to protect the surface cleanliness and ensure it continues in the long term.
  • Change the characteristics of the surface of the circuit board.
  • Improve the surface energy of the surface to improve the adhesion of conformal coating.

Traditionally, cleaning and adhesion promotion has been achieved by either using a wet chemistry treatment like washing or applying extra undercoats (priming).

Now, there are new methods and techniques appearing on the market for improving cleaning, adhesion and actually coating circuit boards differently to the traditional methods.

One of these techniques is plasma treatment.

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How is the plasma applied to clean a circuit board ready for coating?

Typical plasma components are the plasma jets (nozzles), the generators, and process monitoring.

  • The jets apply the plasma to the surface of the circuit board. They could be controlled by a robotic system.
  • The plasma generators create the plasma to clean or supply the coatings as required. They provide output power and, in conjunction with complete pretreatment stations, assume various control functions
  • The process monitoring controls the nozzles, the movement of the system and the quality of the output.

Normally, the plasma systems for customised surface treatment can be integrated inline in existing manufacturing processes with excellent results.

This makes it highly effective for electronic inline processing.

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What does the plasma technique actually do to the surface of the circuit board?

Plasma treatment can clean, activate or coat nearly all surfaces. These surfaces include plastics, metals, (e.g., aluminum), glass, recycled materials and composite materials.

This means the plasma process can be highly effective on devices like circuit board assemblies.

Cleaning and activation

The cleaning and activation processes can help in many ways:

  • Increase adhesion and wettability of the circuit board surface. This increase in adhesion and wetting helps conformal coatings and Parylene stick.
  • In some cases it can make materials bond where it was previously impossible.
  • It can change the surface energy of the circuit board to ensure complete adhesion is possible.
  • It can clean the circuit boards 100% free of residues and contamination including release agents and additives.
  • It can eliminate pre-coating cleaning and priming processes.

Coating

Coatings applied by plasma can change surface characteristics to meet special product requirements that include:

  • Adhesion promotion
  • Corrosion protection
  • Hydrophobic
  • Barrier (Gas and liquid)
  • Electrically-conductive
  • Hydrophilic
  • Anti-adherent

This results in a high efficiency layer that can give the circuit board completely new properties.

Depending on the application, plasma coating deposits a coating down into the microstructures of the material surface. The coating is effectively bonded into the surface and is not a layered coating like a conformal coating or Parylene is.

This can be highly effective for electronic circuit boards.

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What sectors is plasma treatment used for cleaning?

There are many sectors and they include:

  • Automotive
  • Aerospace
  • Military
  • Transport
  • Electronics manufacturing
  • Packaging technology
  • Consumer goods
  • Life sciences
  • Textiles
  • New forms of energy

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