How do I selective apply my conformal coating without using masking?

Selective spraying of conformal coating using an automated robot system is one of the widest used application methods in high volume processing.

The principle is that the conformal coating is applied selectively by a small spray gun to the circuit board to the areas requiring coating only.

The selective process deliberately does not apply the conformal coating to areas that normally require masking such as connectors and other components.

This selective application of the conformal coating to the circuit board can avoid using a time consuming masking process and costs can normally be reduced.

What equipment do you need for selective spraying?

A specialist robotic system designed for application of conformal coatings is normally required for selective coating.

The robotic system will be fitted with various conformal coating spray valves that apply the different types of conformal coating material to the circuit board using different spray patterns.

The level of movement of the robot can vary with systems having three, four, five and even six axes of movement for the spray valves.

Want to find out more about application of conformal coatings to circuit boards by selective robots?

Click to find out more about questions such as:

  1. What equipment do you need for selective spraying?
  2. What specialist valves are required for applying different types of conformal coating?
  3. Which conformal coatings can be used in selective spraying?
  4. Is selective spraying of conformal coating a complex process?
  5. How cost effective is selective spraying of conformal coating as a process?
  6. What variables control the quality of the conformal coating finish in selective spraying?
  7. What are five advantages of the selective spray conformal coating process?
  8. What are five disadvantages of the selective spray conformal coating process?

Need to find out more?

Go directly to our conformal coating selective spray application section 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.

Images 1 and 2 courtesy of PVA (Precision Valve Automation).

How thick should I apply my conformal coating?



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.

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 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.


Where to start in Nexus?

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

My name is Dr Lee Hitchens and I am the author of the Nexus conformal coating website and eBook.

If you’re reading this blog then the chances are you are looking for a piece of information on some area of conformal coating and this is exactly what Nexus was written for.

To start with I thought I would try and answer a few of the basic questions you may have so you can understand what Nexus and I stand for?

What is Nexus?

Nexus is an independent website and eBook dedicated to providing information on all areas of conformal coating and the related topics connected to the process.

This includes Parylene and other deposition processes, fluoropolymer technologies plus the traditional conformal coating materials.

It is made up of a lot of knowledge from many different people from the world of conformal coating that you should find useful.

Why create Nexus?

I have been working in the area of conformal coatings and electronics high reliability for over 25 years in various areas including sales and technical support.

I have also been training people in all areas of conformal coating for almost the same amount of time.

A few years ago I decided that people needed a specific place where they could find all of the useful knowledge on conformal coatings and use in their own production process.

So, Nexus was created and I began writing the website.

I explain a little more here on why I wrote Nexus?

Nexus is Peer Reviewed

This year I decided to re-launch Nexus and create an online eBook.

The major difference with the new site was that the information added was all peer reviewed.

That is people from all over the industry are helping with the quality of the content and helping peer review the information.

This is so the conformal coating knowledge you have from Nexus is as independent as it can ever be and should be able to guide you through most issues without risk of commercial bias.

I hope that you find it the case and the information you find is useful.

So where to start with Nexus?

If you are new to Nexus then a good place to go is our Start Here page.

When people visit our site they go to certain areas. I have tried to indicate these pages directly and help you save some time.

I hope that it works for you.

Finally, this is a continuous project and I am always looking to improve the content. If you need anything specific then let me know and I will be more than happy to help out.

I hope that you find this the case and that you will find all the knowledge you need on understanding conformal coatings and being successful in their application.

Let me know what you think?

Design Rules for Conformal Coating that could save you money, time and heartache

Unfortunately, for too many designers, conformal coating is simply a part number to apply to printed circuit boards.

Unfortunately, for too many designers, conformal coating is simply a part number to apply to printed circuit boards.

For manufacturers embracing lean philosophies and applying conformal coatings, a failure to appreciate the subtleties of the application process can result in an un-coatable (at least as specified) assembly process.


selective coated PCB 500
Unfortunately, too many designers see conformal coating as a part number and do not understand the application process

Nexus have split the conformal coating Design Rules into 4 sections.

These are:

  • General Design
  • Selective Robot
  • Dipping
  • Batch Spraying

The design rules for conformal coating are generally straightforward.

Follow them and you can save money and time in your application process.

However, if the rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.


To find our more click Conformal Coating Design Rules for a Successful Process

What is mealing in conformal coating processing?

Mealing is delamination under the conformal coating that causes a blister

Mealing is a form of delamination of the conformal coating that occurs across the circuit board.

It is a blistering (vesication) affect.

There are several causes for mealing that are similar to de-lamination.

These include:

  • Cleanliness
  • Material Compatibility
  • Permeability to moisture of the coating
  • Degree of coating cure

Click to find out more about how you can prevent the mealing defect in conformal coating.

Need help with your process?

Contact us at Nexus and we can help solve your issues.

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