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.

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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.

 

Why use conformal coatings to protect a printed circuit board?

 

There are a lot of different reasons for using a conformal coating material or Parylene to protect a printed circuit board (PCB).

These reasons can include:

  • Barrier protection
  • High insulation protection
  • High moisture and humidity protection
  • Chemical and temperature resistance
  • Ruggedising
  • Improve dielectric properties
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There are a lot of different reasons for using a conformal coating material to protect a circuit board including barrier protection, increased insulation resistance, chemical protection and increased dielectric properties

Barrier protection

A conformal coating can create a barrier against attack during the lifetime of the circuit board.

The coating material can prevent various types of particulate contamination reaching the surface of the circuit board, which can lead to problems such as corrosion.


High insulation protection

Conformal coatings can provide a high degree of insulation protection for the circuit board during its lifetime when applied as a protective lacquer.

The circuit board normally starts with a high level of insulation when it is first manufacture as it is normally clean.

However, with time in the field and its natural environment the circuit can degrade in different ways.

The conformal coating can slow this degradation down.


High moisture and humidity protection

Printed circuit boards can be vulnerable to moisture and humidity whilst in the field during its lifetime.

Most conformal coatings are highly resistant to moisture and humidity and this can lead to a reduction in leakage currents, cross talk, electrochemical migration, dendrite growth and arcing across the circuit board.


Chemical and temperature resistance

Some conformal coatings can be highly resistant to many types of solvents, chemical attack and be heat resistant.

Normally, a circuit board exposed to chemically aggressive environment would be attacked but the conformal coating can slow down the effects or even prevent them.


Ruggedising

Conformal coating can prevent damage from rough handling, installation and reduction of mechanical and thermal stress.


Improved dielectric properties

Just as the conformal coating can protect the circuit from moisture it can also help to increase the dielectric strength on the circuit board between components and lead interconnects.

This enables the design of the PCB to be more compact and small.


Need to find out more?

For further information on using conformal coatings 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.

 

Conformal coatings used in transport protection

Conformal coatings are used all over the world in so many diverse applications.

One of the largest areas is in transportation.

Conformal coatings protect circuit boards in many sectors of the transport market for both commercial and military applications.

These include:

  • Aerospace (Planes, UAV, rockets)
  • Automotive (cars, motorcycles & commercial vehicles)
  • Rail (Passenger and freight)
  • Sea (Ships of all descriptions)

Of course the reasons for the use of conformal coating are for safety critical reliability improvement and not just inconvenience to the user if the electronics fail.

This makes transport one of the largest sectors for conformal coating use in the world.

It also has some of the most stringent conformal coating standards for the materials to pass.

Conformal coatings protect many different transportation systems including air, land and sea
Conformal coatings protect many different transportation systems

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.

 

Where are conformal coatings being used?

Conformal coatings are being used as protection in ever increasing electronic applications across a wide range of market sectors.

In the past, conformal coating was only applied to military and safety critical products like medical devices as the cost and the process of doing this was high.

However, the emphasis on reliability has changed.

In recent years, the development in materials and new processes, linked with the customer requirement of a reliable electronic product that isn’t safety critical, has meant consumer electronics products must now be protected as well.

With the new technologies like wearable electronics becoming more popular then this trend will only increase and protecting the electronics with a coating of some description will become even more commonplace.

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Traditional markets like aerospace, automotive and military sectors still use conformal coatings. However, the growth in use across many other sectors is significant due to customers requiring reliable products for consumer electronics

So what sectors are using conformal coatings and other thin film technologies?

Due to the fact that conformal coatings provide several key benefits including moisture and insulation properties, chemical resistance and particulate protection, this means they can be used anywhere there is a need for a higher reliability than that which is achieved without the coating.

It is possible to identify both traditional and emerging sectors where conformal coatings are being applied.

These include sectors such as:

  • Aerospace
  • Defence
  • Automotive
  • Telecommunications
  • Wearable technologies
  • Consumer electronics
  • Tablets and computers
  • Industrial Engineering
  • Transport
  • White Goods
  • Geothermal
  • LEDs
  • Solar Panels
  • Marine and Coastal Environment
  • Space
  • Medical

Each market sector has a distinct set of requirements in terms of standards, operating environments as well as other factors that impact on the requirements.

The challenge is for the engineer to define the requirements and the suppliers to provide the protection at a commercially effective price.

To find out more click conformal coating basics to discover why conformal coatings are used and what they actually do to protect the circuit boards and products.


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.

Why use a conformal coating to protect a circuit board?

A fundamental question asked quite often is why do I need to coat?

After all, it costs money and it can be difficult to process. Not very attractive to use it!

However, there are several reasons why a traditional liquid conformal coating or Parylene could be used to protect a printed circuit board (PCB).

These reasons include:

  • Improving the insulation protection of the circuit
  • Increasing the protection of the circuit from attack from high moisture and humidity
  • Increasing the circuits chemical and temperature resistance
  • Making the circuit board more resilient through ruggedisation
  • Improving the dielectric properties of the printed circuit board
  • Creating barrier protection from liquids such as water, blood etc
  • Stopping the board surface getting dirty from contamination that can lead to corrosion long term

To find out more about these reasons read our section why use a conformal coating?


How can we improve Nexus?

Let me know your thoughts on the content and how we can improve our services ?

Contact me directly by email lhitchens@nexus3c.com now.

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

How do I select a conformal coating?

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

I am regularly asked how I would go about choosing a conformal coating?

I normally respond to the person involved by asking an awful lot of questions and they wonder what they got themselves in to!

Why do I have to ask a lot of questions?

The questions are there because choosing a conformal coating process is a complicated process usually balancing a lot of important trade-offs and compromises.

When I consider the question I actually see three major parts of the complete process.

These parts are:

  1. The conformal coating material
  2. The application method
  3. The circuit board design

When you consider these three points you have to balance them to create the best compromise process solution that suits your requirements.

This is what I call the Holistic Approach to conformal coating.

So, what should you do next?

It is tempting to consider one of these parts in isolation.

However, this could be a mistake.

After all, the wrong choice can be devastating to the conformal coating production process as a whole and even worse, the reliability of your product.

 

I feel that to identify the best conformal coating material and application process there are several key factors that you need to consider that, if you are lucky, will add up to at least one sensible process choice.

Factors to be considered include:

  • Temperature operating range
  • International, customer or National Standards
  • Environmental considerations of the circuit board
  • Requirement to rework the conformal coating
  • Conformal coating material type
  • Application process considerations
  • Curing the conformal coating
  • National, State, Regional Legislation and Insurance
  • Supplier performance and availability
  • Price

To find out more about these factors visit Nexus and see how we recommend you select a conformal coating through the holistic approach.