The critical areas of designing for conformal coating

Article Author

  • Dr Lee Hitchens, Nexus

Are these phrases familiar on the conformal coating production line to you?

“Who designed this process?”

“This is impossible. We can’t meet their requirements”

“How did they decide to coat this board this way?”

I am sure they are to a few engineers out there and it wouldn’t have to be automatically about conformal coating either!

In fact, I wish I could be paid a dollar or pounds for the each time I have heard a similar phrase on the shop floor like this relating to the conformal coating production line.

I wouldn’t be rich but I would get enough for a great dinner or two.

Should it occur nowadays with our knowledge?

You would think not when Design for Manufacturing (DfM) is understood so well by so many.

However, it still occurs and with a frequency that can be alarming.

So, how can we prevent it happening on the production line?

We have to start right at the beginning with the design stage.

So, lets examine the design stages that matter to the conformal coating.

The two key areas of designing for conformal coating

When conformal coating is discussed at the design stage then we are really talking about two areas of design.

These are designing for reliability and designing for processing.

Designing for reliability

Designing for reliability of the product is ensuring the product functions correctly in the environment it was designed for the right length of time.

Get the reliability wrong and the product may fail in the long term before the expected lifetime is reached.

Designing for processing

Designing for conformal coating processing is ensuring the engineers can successfully coat the board and not ruin a perfectly good product.

Fail to design for the conformal coating process correctly and the product may not even reach the field due to excessive costs.

Defining both design criteria can be critical to the success of the product.

When we discuss conformal coating and the issue of design, then we are really talking about two areas of design. These are design for reliability and design for processing.
Get the conformal coating design for reliability wrong and the product may fail in the long term before the expected lifetime is reached. Fail to design for the conformal coating process correctly and the product may not even reach the field due to excessive costs.

Designing for conformal coating reliability

Understanding the design requirements of the circuit board to be protected by the conformal coating is one of the most fundamental questions that can be asked.

After all, the purpose of the conformal coating is to protect the electronics, by extending and preserving the life of the product.

When designing for reliability then there are several important areas to consider for the product.

These include:

  • Reliability Requirements
  • Life Cycle
  • Environment
  • Materials and Parts selection
  • Electrical Effects

Considering each area separately can be crucial for the reliability of the product.

Designing for conformal coating process

Once the product reliability requirements have been defined as part of the conformal coating design procedure then the resulting information needs to be combined with the data from the holistic approach.

The holistic approach examines many factors that when combined with the product reliability requirements give us exact information for designing for process.

Combining reliability requirements and holistic information gives us the following information:

  • Conformal coating material to be used
  • Application method that is suitable for the material and circuit board
  • Masking requirements if necessary
  • Production line stages required
  • Process parameters to be met
  • Inspection criteria to be used

This data is then combined into a set of conformal coating instructions that can be used to implement the conformal coating process.

Click to find out more about designing for conformal coating process.

Conclusions

Want to avoid those dreaded words on the production line that announce that the process is costing you way more than it should?

Then design for reliability and design for processing.

It can only help you in the long run!


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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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