How do I brush coat my conformal coating?

The application of a conformal coating using a brush to “paint” on the material to the circuit board is a common practice all over the world.

Generally, it is done as a final touch up process after the main application method is used.

However, it can also be done in mainstream production.

Conformal coating brushing in an inspection booth_NEXUS1

Applying the conformal coating

The operator according to the requirements of the circuit board applies the conformal coating selectively with the brush.

Areas not be coated are avoided.

The key for success with brushing conformal coating is the technique of application.

The correct method is to flow the coating on. The coating should be loaded on to the brush and flowed onto the circuit.

The material should not be brushed on like paint.

Screenshot of Nexus brush coating
Watch a video on brushing conformal coating.

Need to find out more?

Click conformal coating brushing for further information or contact us directly and we can help you.

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 important facts about acrylic conformal coatings

conformal coated PCBs Collage 640x480_Nexus

The  majority of conformal coatings used in the world are organic coatings.

The acrylic conformal coatings are part of that group.

Here are five reasons to use acrylic conformal coatings:

  1. Acrylic conformal coatings have excellent humidity resistance. This is the number one use for using an acrylic conformal coating.
  2. Solvent based acrylic conformal coatings are one of the easiest materials to apply to printed circuit boards. They are easily applied using every method including spraying, dipping and brushing.
  3. Acrylic solvent-based coatings dry quicker than nearly all other types of coatings. They dry within minutes. This is because the acrylic resin does not polymerise (does not cure) and actually just dries out as the solvent evaporates away. They are also very easy to dry artificially using heat and can reach optimum properties very quickly.
  4. Acrylic coatings are very easy to repair and rework since they have very little chemical resistance. They are easily chemically removed and stripping a complete board is relatively straightforward.
  5. Finally, acrylic coatings have excellent pot life compared to many other types.

Need to find out more?

Click for further information on organic and acrylic conformal coatings or contact us directly and we can help you.

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.

 

What is Parylene?

Parylene is the trade name for a variety of chemical vapor deposited poly (p-xylylene) polymers used as moisture and dielectric barriers.

Although Parylene is a conformal coating it is different compared to the standard “wet” liquid conformal coatings in that it is deposited as a gas in a vacuum chamber and it is a dry process.

nexusphoto1Although Parylene is a conformal coating it is different compared to the standard “wet” liquid conformal coatings in that it is deposited as a gas in a vacuum chamber and it is a dry process. Image courtesy of Plasma Rugged Solutions

This method of chemical vapour deposition (CVD) and the Parylene dimer material itself give Parylene unique properties compared to other traditional conformal coatings.

For Parylene there are five key areas that Nexus can help with.

These are:


Need to find out more?

For further information on Parylene then contact us directly or go to our Parylene section in Nexus. See how we can help you.

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 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.

 

What application methods are available for applying conformal coating?

 

Conformal coatings can be applied to printed circuit boards (PCBs) in the production process environment in many different ways.

Listed below are the common methods of applying conformal coating materials:

Click on each to review each conformal coating application technique in our free ebook online.

Nexus
Conformal coatings can be applied to printed circuit boards (PCBs) in the production process environment in many different ways including spraying selectively, batch spraying and dipping.

The holistic approach to conformal coating application methods 

It is possible to split the different application methods and their suitability in many different ways including:

  • Compatibility with the conformal coating material
  • Design of the circuit board
  • Suitability to low, medium and high volume
  • Manual versus automatic process
  • Type of method of application
  • Level of control required

Each of the various coating methods has different advantages and disadvantages.

This relates to the holistic approach to conformal coating processing. It states that you should consider the conformal coating material itself, the application process and the circuit board together and not as three separate entities.

However, when considering the application methods it is possible to make some assumptions that help in selection.


Need to find out more?

For further information on conformal coating application methods then contact us directly and we can help you.

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.

 

How thick should I apply my conformal coating?

 

positector

The measurement of the conformal coating thickness on a printed circuit board (PCB) to ensure internal and international standards are met is now a standard process in production.

There are several methods for measurement of conformal coating thickness including dry and wet film processing. However, the most important factor is how thick should the coating be?

First, you can reference both internal and international standards like IPC A 610 for conformal coating application.  They can help a lot.

These standards will help guide you in the coating thickness required for a particular coating materials since the coating thickness suggested will be dependent on the resin of the conformal coating.

For example, an acrylic or polyurethane based conformal coating has a different coating thickness requirement to silicone-based materials.

Below are the suggested conformal coating thicknesses from the IPC A 610 standard:

  • Acrylic            30-130 μm
  • Urethane        30-130 μm
  • Epoxy             30-130 μm
  • Silicone          50-210 μm
  • Parylene        10-50 μm

Note, that this is the average thickness across the circuit board. It is almost impossible to achieve a homogeneous coating thickness with the liquid conformal coatings due to surface tension issues during drying.

Using this information you can now move forward and look at the application of the conformal coating.


Need to find out more?       

For further information on process control and conformal coating thickness 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.

Things you should know about Parylene

What is Parylene?

Parylene is a conformal coating that is deposited as a gas in a vacuum chamber.

It is a completely different process to the liquid conformal coatings and its properties offer advantages and disadvantages in comparison.

Parylene is a dry process compared to the standard “wet” liquid conformal coatings.

Since Parylene is deposited as a gas its thickness is almost uniform across the whole circuit board.

 

The ABCs of Parylene

Parylene is an organic polymer conformal coating that is deposited as a gas in a vacuum chamber.

Therefore, the Parylene application process is a completely different process to the liquid conformal coatings.

This gives Parylene unique properties that are not possible with the typical liquid conformal coatings normally used in electronics protection.

 

Five key facts about Parylene

  1. Parylene is the trade name for a variety of poly(p-xylylene) polymers
  2. It is a conformal coating that is deposited as a gas in a vacuum chamber. This is different to liquid conformal coatings.
  3. The Parylene film is created via a controlled Chemical Vapor Deposition (CVD) process.
  4. It is a dry process compared to the standard “wet” liquid conformal coatings.
  5. This process makes Parylene a highly effective moisture and dielectric barrier that outperforms most liquid conformal coatings.

 

Three important points you should know about Parylene

  1. Parylene has unique properties that are not possible with the liquid conformal coatings.
  2. Parylene is a conformal coating that is deposited as a gas in a vacuum chamber.
  3. This is different to liquid conformal coatings that can be brushed, dipped or sprayed.