Five key facts about plasma cleaning for conformal coating processing

  1. Plasma cleaning can clean surfaces of the circuit board 100% to improve adhesion and surface energy of the product. Generally, conformal coatings must exhibit good adhesion in order to be effective.
  2. There is no single theory that describes the property of adhesion for coatings. There are several basic mechanisms for coatings that are known to define good adhesion. They are adsorption, chemical bonding, and mechanical interlocking:
  • Adsorption is where the molecules in the conformal coating wet or flow freely over the substrate and make intimate contact with the substrate. This forms interfacial (electrostatic) bonds with van-der-Waal forces.
  • Chemical bonds are formed at the interface between the conformal coating and the substrate.
  • The conformal coating film penetrates the roughness on the substrate surface. This results in mechanical interlocking once the coating dries.

All three of mechanisms do not have to occur to form good adhesion. Depending on the specific conformal coating system, substrate, and application method, different mechanisms could work. However, good wetting or adsorption is normally required.

  1. Many wet chemistry cleaning processes can be eliminated. Methods using cleaning chemistries, water processing and drying energy become unnecessary.
  2. 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.
  3. The plasma cleaning process is a simple, safe and environmentally friendly technology.

Plasmatreatment of circuits collage

Plasma cleaning can clean surfaces of the circuit board 100% to improve adhesion and surface energy of the product. Generally, conformal coatings must exhibit good adhesion in order to be effective.

 


Need to find out more?

For further information on plasma cleaning for conformal coating processing then contact us directly.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page or our free conformal coating ebook.

 

Five key facts about ultra-thin, nano- coatings used in electronics protection

  1. Water repelling (hydrophobic) Properties – An ultra-thin coating is normally hydrophobic. This is because it is normally a fluoropolymer technology. The coating does not allow the water to wet on the on the surface of the coating. It modifies the surface and changes its dyne energy. A typical conformal coating like an acrylic or polyurethane is not water repellent and water wets the surface. nano coating
  2. Ultra-thin –Typical coating thickness is 1-2um for a coating (depending on application) compared to the acrylic, urethane and silicone conformal coatings that are applied at >25um.
  3. No masking of connectors required – The circuit board can be completely submerged in the coating liquid with no masking applied. Due to the extremely thin coating applied (<1-2um), the components can be connected together and the electrical connection is easily made. This would not be possible for a standard conformal coating. So, costs of processing are extremely low.
  4. Simple application process – The ultra-thin coating can be applied by dip, brush or spray.  But, the simplest method is dipping. Since there is no masking then the dip process is simple and is an extremely cost effective application method.
  5. Fast drying – Since the coating is ultra-thin and the solvents normally used are fast drying then the fluoropolymer coating dries extremely quickly. The coating can be dry in seconds and ready for use in a few minutes.

Need to find out more?

For further information on the ultra-thin, nano- coatings then contact us directly.

Or, you can go to our free eBook by clicking fluoropolymer coating materials now.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page.

 

Which conformal coating standards do you need in the production process?

For conformal coating processing and inspection there are many different types of standards.

They include international, national, national trade bodies and internal company standards.

The purpose of standards is to give guidance for users on the quality of the conformal coating process.

For conformal coating standards there are two areas that they address.

These are:

  • Conformal coating manufacture
  • Conformal coating production process

These two areas are distinctly different.

Standards for conformal coating manufacture

These standards are used for the manufacture of the conformal coating.

They include:

  • MIL-I-46058C
  • Underwriters Laboratories (UL)
  • IPC-CC-830B
  • IEC 61086-1 ed2.0

These standards are used to test the quality of the conformal coating before use.

The standards can also be split in two other ways.

  • Self-Certification: Those that the manufacturer follows and completes the testing themselves on their own conformal coatings.
  • Independent: Those standards that are completed by independent laboratories on the customer coatings.

For further information click conformal coating standards now.

Standards for the conformal coating process

The standards for processing conformal coatings are used by the end user of the coating in the production environment.

They include:

  • IPC A 610 Acceptability of Electronic Assemblies
  • IPC-HDBK-830 Guidelines for Design, Selection and Application of Conformal Coatings

Both standards are self-certifying and help the production team control their conformal coating processes.


If further information on these topics and the key question you can go to our free eBook by clicking conformal coating standards now.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page.


Dr Lee Hitchens, Author of Nexus website and ebook
Dr Lee Hitchens, Author of Nexus

Dr Lee Hitchens is the author of the Nexus conformal coating website and eBook.

Send me an email at lhitchens@nexus3c.com and let me know what you think?

 

What are the key questions to ask when cleaning for conformal coating?

Of all the questions I am asked related to cleaning the most frequent is

“Do I need to clean my circuit board before conformal coating?”.

If only it was simple to answer!

Generally, cleaning of a circuit board before conformal coating application is desirable. For Parylene this requirement may be even more important due to the bonding issues of the material.

However, it may not be essential.

Ultimately, the cleanliness of the circuit can be crucial for both the short-term production process and the long-term reliability of the circuit.

But, its difficult to know for sure if you need to clean until you complete some trials.

For the process it is difficult to know until you attempt to apply the conformal coating in production.

Then you will know immediately if you need cleaning since if you have problems you will see conformal coating defects like de-wetting, de-lamination and poor adhesion.

For the long-term reliability unless you want to wait until your product fails then some sort of reliability testing should be tried.

After all the purpose of the application of the conformal coating is to improve reliability.

It has less value unless the board is clean enough in the first place.


Other key questions in cleaning

There are many questions relating to conformal coating and cleanliness that are regularly asked.

These include:

  • What is being cleaned when circuit boards are washed?
  • How should I clean my electronic circuit board?
  • How do I validate my cleaning process?

If further information on these topics and the key question you can go to our free eBook by clicking Nexus conformal coating and cleaning.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page.


Dr Lee Hitchens, Author of Nexus website and ebook
Dr Lee Hitchens, Author of Nexus

Dr Lee Hitchens is the author of the Nexus conformal coating website and eBook.

Send me an email at lhitchens@nexus3c.com and let me know what you think?

 

What are the important physical properties of a conformal coating material?

When thinking about a conformal coating’s physical properties then I always consider that there are three states.

They are the properties during the:

  • Liquid Stage (When the conformal coating is a liquid ready for production).
  • Process Stage (During the conformal coating process).
  • Dry Stage (When the conformal coating has dried and or cured).

The key properties will vary depending on which state you are looking for.

For example, for the liquid state the critical properties for the conformal coating  include:

  • Flash point
  • Storage lifetime
  • Appearance and colour
  • Density
  • Solids content
  • Viscosity

These properties are important for the conformal coating process and completely influence the outcome of the production line.

However, for the process state the critical properties the conformal coating exhibits include:

  • Wetting
  • Capillary
  • Viscosity
  • Wet Film Thickness
  • Surface Tension
  • Pot life
  • Drying and curing

These properties of the conformal coating material will again influence the final outcome.

Finally, for the dry state the critical properties of the conformal coating include:

  • Abrasion Resistance
  • Chemical Compatibility and Resistance
  • Coefficient of Thermal Expansion
  • Corrosion Resistance
  • Edge Loss
  • Flammability
  • Flexibility
  • Fungus Resistance
  • Glass Transition Temperature
  • Hydrolysis Stability
  • Outgassing
  • Permeability
  • Refractive Index
  • Temperature Gradient
  • Thermal Shock
  • Thermal Stability
  • UV Stability

Note, there are a lot of physical properties but many not be important to you.

Also, most of these physical properties may be defined by the manufacturer and contained on a data sheet.

However, many other properties may be required and you may need to test.

To find out more click key physical states for conformal coating.

Or Contact Nexus now and let us show you how we can help you.


Dr Lee Hitchens, Author of Nexus website and ebook

Dr Lee Hitchens is the Author of the Nexus eBook and a main contributor to Nexus.

NEW conformal coating Process Control section for eBook

 

Nexus are preparing a new section for its eBook on conformal coating Process Control.

We are aiming to publish this in September 2016.

The section will cover all aspects of the topic including all of the key process control variables that affect production including the equipment, materials and people involved.

viscometer image 500.jpeg
The Nexus eBook section on Process Control of conformal coatings will examine many of the areas that give you the key to the perfect production line.

Since Nexus is peer reviewed and we want the content to be relevant we are asking if anyone would like to add input into the section?

Help could be given in the form of guidance on topics and technical input and expertise on a particular area.

Let us know if this is of interest and get in touch with me directly by email lhitchens@nexus3c.com or mobile +44 7862 253321.

I can show you what we are planning and perhaps you can guide us in the final format.

Contact Nexus now and let us show you how we can help you.


Dr Lee Hitchens, Author of Nexus website and ebook

Dr Lee Hitchens is the Author of the Nexus eBook and a main contributor to Nexus.

 

What is the right removal process for conformal coating removal?

There are several reasons why a conformal coating may need to be removed from a printed circuit board or component.

However, the two main reasons I normally see are:

  • The board or component may need to be reworked for electrical repair or improvement of functionality
  • Poor conformal coating application has led to the requirement to repair the material and reapply the coating

Whatever the reason for removing the conformal coating the process is a challenge.

Whether it has been a localised repair to a component or a complete strip of the conformal coating it has always been difficult for the unlucky technician stuck with the job.

Manual conformal coating removal 500.jpg


What are options for conformal coating repair and removal?

There are several main methods now available for both localised repair and complete stripping of the conformal coating.

These include:

  • Soldering through the coating
  • Chemical stripping of the material
  • Mechanical abrasion with a tool like a blade
  • Micro abrasion using particulates to “shot blast” the coating
  • Plasma processing using a plasma gas for removal

So which is the right removal process for conformal coating?

None of the options are perfect.

All of them have there advantages and disadvantages. The key is to review the circuit board and its needs on an individual basis.

Some of the factors that influence the conformal coating removal process include:

  • Conformal coating material type
  • The size of the area to repair
  • The components sensitivity to the repair process (will they get damaged?)
  • The cost of the repair versus the value of the circuit board
  • The health and safety implications to the operator carrying out the repair

All of these factors and more can influence the choice or even whether the operation takes place.

After all, the cost of most electronics nowadays can be so low that the repair process is not cost effective!

To find out more go to the Nexus eBook section on conformal coating removal or contact us directly and we can help.


Need help with your conformal coating process?

Contact Nexus now and let us show you how we can help you.


Dr Lee Hitchens, Author of Nexus website and ebook

Dr Lee Hitchens is the Author of the Nexus eBook and a main contributor to Nexus.