Where to start when selecting a conformal coating application process

Article Author

  • Dr Lee Hitchens, Nexus

Understanding which conformal coating application technique is the right solution for your circuit board, material and production process can make a huge difference to the final costs.Choosing a process for coating your circuit boards may seem simple.

But, choosing the wrong process can cost a lot of money. Its also surprisingly easy to do.

There are at least five different standard methods for applying conformal coatings.

They include brushing, dipping, spraying, selective robot and vapour deposition.

Understanding which technique is the right one for your circuit board, conformal coating and process, and ultimately your company can make a huge difference to the bottom line.


So where do you begin?

Its always worth applying the holistic approach to the conformal coating process.

That is you should consider that there are actually three parts to the jigsaw puzzle of your production line and not just the application system you require to buy.

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 solution for your conformal coating production process that suits all of your requirements.

This is because these three major parts can create difficult choices for you for the equipment selection.

Neglecting any one of them could be highly costly.

This is the holistic approach to conformal coating.

There are actually three parts to the jigsaw puzzle of your conformal coating production line and not just the application system you require to use. Using the holistic approach helps you select the right conformal coating application process.
There are actually three parts to the jigsaw puzzle of your conformal coating production line and not just the application system you require to use. Using the holistic approach helps you select the right conformal coating application process.

So how do you apply the holistic approach to the equipment selection?

I would personally start with three key points.

They are the:

  1. Circuit board design
  2. Number of boards required to be coated
  3. The protection requirements of the PCB

The first two points of board design and volume allows you to ask the right questions and make some decisions on the types of application equipment you could use.

You can also eliminate some of the options that just don’t work practically or economically.


What are the right questions to ask?

Consider the following questions against all the different methods of application you could use:

  • Does the volume of circuit boards required to be coated work economically and practically with each of the different application methods?
  • Is the board design suited for each of the application techniques? For example, can a selective robot coat this particular board design or is it more suited to dipping?
  • Can you use currently available equipment or will you need a new production process?
  • What are the additional costs for using a particular technique? For example, what are the masking and curing requirements and their associated costs both financially and in terms of process time?

These questions will allow you to examine each of the application techniques and grade their suitability.

You can then move on to the next stage.

Low volume electronics may not be suited to selective robotic conformal coating processing and alternative methods like batch spray my be more suitable
Low volume electronics like complex one off avionics may not be suited commercially to selective robotic conformal coating processing and alternative methods like batch spray may be more suitable.

Selecting a range of conformal coatings that meet your protection requirements

This point is important.

A range of conformal coatings should be selected if at all possible.

It is okay to be biased towards a form of material. It may be environmentally friendly or offer high speed processing.

After all, this is part of the selection process.

However, having options for your final conformal coating material allows you to cross-reference the material options with the application type options to see if you have a viable solution.


The final step

Now, you get to compare your different equipment options with the suitable conformal coatings that protect your circuit.

If you are lucky you have the perfect match.

If you don’t then some compromises will be required and you need apply the holistic approach again to review all three points.

This is where it gets tricky!


Dr Lee Hitchens, Nexus Conformal Coating ConsultantDr Lee Hitchens is the author of the Nexus eBook and a regular contributor to conformal coating topics.

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