FAQs

Here are some of the common questions we receive at Surfx Technologies. Contact us if you have any additional ones.

What is plasma?
Does the plasma generate UV light
How fast will the plasma activate the surface?
How is surface activation measured?
Can I send you samples to treat and see if it works?
What is the difference between downstream and direct plasma processing?
What hardware is used to generate plasma?
What is the advantage of atmospheric pressure operation and can I use the Atomflo™ in a vacuum system if I want to?
What safety concerns should I be aware of when operating the Atomflo?
What types of gases can I feed to the plasma source?
Where do I place the plasma source relative to my sample surface?
Do any parts of the plasma source wear out?
Can I rent a system to test at my facility?

 

 

What is a plasma?

Plasmas are said to be the fourth state of matter and are among the most widely studied subjects in modern science. Stated simply, a plasma is an ionized gas that conducts electricity.

Plasmas come in many forms, ranging from a welding torch to a fluorescent light bulb. As show in Fig. 01, they may be identified by their relationship between the neutral gas temperature and the electron temperature in the plasma (1 eV ~11,000 ºC). In a torch, an arc forms between the electrodes resulting in complete ionization of the gas and a temperature rise >4,000 ºC. Atmospheric plasma spray guns take advantage of the high temperatures found in arcs. These devices are able to vaporize many materials, and coat them at high speed onto surfaces.

The fluorescent light bulb, by contrast, contains a low pressure glow discharge. The vacuum inside the bulb is essential, because it allows the gas to be weakly ionized with low power input. Such weakly ionized plasmas are not at thermal equilibrium, i.e., the neutral molecules are close to 25 ºC, while the free electrons are above 10,000 ºC. The high-energy electrons collide with the neutral molecules, dissociating them into atoms and radicals, thereby yielding a reactive gas mixture. Most plasmas used for materials processing at low temperature are weakly ionized and produced in a vacuum.

Using plasmas for materials processing requires expertise in chemistry. The Atomflo™ atmospheric plasma is a source of atoms and radicals that are carefully selected for surface treatment, cleaning, etching, or depositing thin coatings. For example, a hydrogen plasma may be used to cure polymer films, whereas a nitrogen plasma may be combined with silane to deposit a silicon nitride plasma coating. The key in all these applications is combining the right hardware with the right chemistry to achieve the desired results.
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Does the plasma generate UV light?

Ultraviolet light is generated by the plasma, but its intensity is very low, and we have not heard of it ever causing any damage to treated parts.
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How fast will the plasma activate the surface?

The speed depends on the application and the sample composition. Most plastic surfaces are activated for adhesion in a few tenths of a second with no appreciable heating of the sample. Many customers are extremely satisfied with the throughput of Surfx plasma tools.
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How is surface activation measured?

The common method of measuring surface activation is water contact angle (WCA). The WCA is directly related to the surface energy of the solid-water interface.
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Can I send you samples to treat and see if it works?

Yes! We offer one free demo to new customers and provide an Application Report when we send the samples back.Please contact us for further information.
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What is the difference between downstream and direct plasma processing?

Our pictures of the Atomflo™ show the plasma flowing out of the device. Actually, at this point the gas is no longer strictly a plasma, because practically all of the electrons and ions have been stripped away. Our products are used for downstream plasma processing. The plasma is sustained between the electrodes inside the device. What flows out is primarily neutral species, i.e., atoms, radicals and metastable molecules. These reactive neutral species are responsible for the reactions that occur on the substrate surface.
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What hardware is used to generate plasma?

One must apply an electrical field to the gas to generate a plasma. In a vacuum chamber, where the ions and electrons have long lifetimes, it is relatively easy to do this. Radio frequency power can be applied to two metal plates immersed in the vessel creating a capacitive discharge. Alternatively, RF power may be deposited into a coil mounted on the chamber walls, thereby producing an inductively coupled plasma. The gas also may be ionized by application of microwave power at 2.45 GHz to a specially designed cavity or horn.

In an atmospheric plasma, a variety of power supplies may be used from DC to RF. Here, the challenge is to design the electrodes and gas flow to yield intimate contact between the reactive gases and the substrate. At high pressure, the atoms and radicals are quickly consumed by collisions in the gas, so the transit time from the plasma to the surface must be short. If one wishes to achieve low temperature operation with atmospheric plasmas, then special precautions must be taken to prevent arcing between the electrodes.

A wide variety of plasma tools are available today, reflecting the broad spectrum of materials applications being tackled by these remarkable products. To the end user, the choices can be bewildering, making the task of product selection challenging at best. We encourage you to contact Surfx Technologies so that our engineers may assist you with the selection process.
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What is the advantage of atmospheric pressure operation and can I use the Atomflo™ in a vacuum system if I want to?

The advantage of atmospheric plasmas is their ease of use, cost effectiveness, and ability to continuously treat materials of any size and shape. Furthermore, the reactive gas flows out of the plasma source and around and through complex parts, such as MEMS. The Atomflo™ is unique in that it is a particle-free plasma source, and generates significantly less particle contamination than vacuum plasmas.
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What safety concerns should I be aware of when operating the Atomflo?

Oxygen plasmas generate a small amount of ozone, so you should operate the source under adequate ventilation, such as inside a hood. The plasma source does not present an electrical shock hazard. However, it can get hot to the touch. Please employ standard safety precautions as you would with any equipment that uses electricity and compressed gases. Read the manual and follow the instructions. Always wear safety glasses!
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What types of gases can I feed to the plasma source?

Generally, you feed argon or helium and up to 2 vol.% of molecular gases, such as oxygen, nitrogen, hydrogen, and carbon tetrafluoride. The molecules will be dissociated by the plasma into atoms, e.g., O, N, H or F. The inert gas allows you to have complete control over the plasma chemistry.
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Where do I place the plasma source relative to my sample surface?

If possible, the plasma source should be placed within 5 mm of the sample surface. The reactive atoms generated by the plasma are quickly consumed at atmospheric pressure. Moving the source farther away from the surface increases the process time.
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Do any parts of the plasma source wear out?

No. Provided the Atomflo™ is operated properly, it will not wear out under continuous use in high volume manufacturing. The RF plasma does not erode the electrodes such as occurs in thermal plasma torches.
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Can I rent a system to test at my facility?

Yes! We offer monthly rentals of our systems. For a quote, please contact a Surfx representative.
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