Factors to consider when setting up a conformal coating production line for printed circuit boards

The conformal coating production line, whether it is an operator manually brush coating printed circuit boards (PCBs) or an inline robotic spray coating process is typically made up of several stages.

However, not all the stages are mandatory or may be required. These stages are shown below:

 

Chart

Consider each stage below.


Boards In / Boards Out

This is very straightforward. The PCBs are delivered to the conformal coating area ready for processing.


Inspection

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Inspecting the circuit boards before starting the conformal coating application process starts helps avoid stopping the line if there is a problem.

The initial inspection process can also identify which PCBs are to be coated, the material to be used and how they are to be coated.

This can be done automatically as part of the production process or completed by the operator.


Cleaning

Cleaning the circuit boards before application of conformal coating may or may not be required.

This is a decision that should be made earlier on in the design stage before production actually starts.

However, if you do decide to clean then consider these guidelines:

  • Ensure that the cleaning process does not add more contaminants to the PCB than it started with due to entrapment of cleaning fluids.
  • Make sure the PCBs are dry enough for the conformal coating process and the cleaning process not leave water entrapped under components that could impede the application.
  • Ensure the cleaning process actually removes residues that may cause defects like de-wetting to minimise finishing at the end of the process.

Again, cleaning is for the engineers to decide.  The option of whether you need to clean your circuit boards for conformal coating is a whole topic on its own.


Masking

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Masking may not be required on the circuit board.  However, generally there are very few circuit board assemblies that can be completely coated and have no areas that must not be conformal coated.

Some components on PCBs generally need to avoid having conformal coating applied to them.

This leaves three options:

  1. You can avoid coating the component or area using a selective application process.
  2. You can apply some form of masking that the conformal coating can be applied to and remove the masking materials after application.
  3. You can apply a conformal coating that does not need masking against.

Again, engineers need to consider their options on whether to use conformal coating masking as soon as possible.


Pre-Coating Inspection

Generally, it is more efficient to double check the masking process is correct before conformal coating application rather than repair the PCB after the process goes wrong because the masking process was incorrect.

This check can be manual or automated but it is highly valuable.


Coating Application

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The one stage that cannot be avoided is the conformal coating applied to the PCB.

There are many different methods for applying conformal coatings and probably the most important factor in all of them is training. The operator needs to understand the process to be able to work correctly.


Drying and Curing

A conformal coating is a wet process (unless you use Parylene) and therefore the coating has to dry.

The difference between drying and curing in conformal coating is very different. However the process required depends on the conformal coating itself.

Care needs to be taken in deciding how to achieve the right result.


De-masking

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Like masking, there is skill in removing the masking materials from the circuit board and not damaging the coating.

This is also where touch up (finishing) is carried out to ensure the final finished PCB is fit to pass the inspection criteria.

Work instructions are needed along with training on the specific methods of finishing to ensure this can be achieved.

Again, the work environment can be critical to achieve the right results.


Inspection

When the PCB is conformal coated and finished, you need to know if the product meets the inspection criteria.

The conformal coating inspection process can be done manually or automatically. This can depend on the volume of PCBs and the level of sophistication required.

Again, it is down to operator training and using the right equipment to ensure that this is possible.

Also, at this stage it is possible to measure process factors like coating conformal thickness to check that the criteria are met.


Other factors to consider

The set up of a conformal coating production line regardless of the application method has many similar characteristics.

General requirements

Any coating facility will need the basic requirements put in place that would be standard for any piece of electronic manufacturing process. These include ESD systems, facilities for the machines, the environmental requirements and the normal Health & Safety (HSE) considerations.

Health & Safety (HSE)

HSE tends to be more important for conformal coatings since in general the coatings themselves are hazardous, or the way they are applied makes them potentially harmful to operators

Environment

Conformal coatings are sensitive to the environment that they are processed. Cleanliness could be critical, as can temperature and humidity.


Summary

Setting up a conformal coating production facility can be a straightforward process as long as all factors are considered.

Get this right and many of the problems that could occur during production will be avoided.


Need to find out more?

Click conformal coating production processes 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.r

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.

 

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.

Where to start with Nexus and conformal coating

If you are new to Nexus and our work on conformal coatings 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.

It also tells you a little bit more about why Nexus was written.

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, technical support and training.

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.

Why is Nexus independent?

People from all over the conformal coating 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.

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.

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


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.

Nexus is an Independent Conformal Coating Resource and Database

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focussed on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

One of the founder members of Nexus is Dr Lee Hitchens PhD who has worked within the conformal coating industry for over 18 years. Until recently Dr Hitchens’ work included sales of conformal coating materials and capital robotic equipment in all areas of the world. However, he decided to form Nexus and become independent.

Dr Hitchens sums up Nexus,

“The demands on conformal coatings and the processes that apply them are becoming more and more complex with the exponential growth in electronics. Couple this with the knowledge gap and the lack of time to learn in most companies and you find a very difficult situation for most users.

Nexus is here to bridge the gap. Independent of all material and major capital equipment suppliers, our consultants can offer a unique perspective into conformal coating that users can tap into, as much or as little as needed. We can champion the user but also offer help to the supplier who needs to educate a rapidly growing market across the globe.”

Want to find out more about Nexus? Join us at Nexus3c.com

Conformal Coating Polls – Join in to help understand Global Conformal Coating Processes for the Electronics Industry

Complete the Polls on the Home Page of the Nexus and help Nexus understand what information is required to support companies and the results are published

Nexus3C have launched a monthly conformal coating poll so users of the service can gain insight on key processing issues, trends and markets to help them in the future.

Topics in the near future will include conformal coating rework, parylene versus liquid coating and trends towards environmentally friendly conformal coatings.

Contact Nexus3C to view our conformal coating poll and submit your vote

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