PCB Enviromental Protection

What is the environment?

If the environment is saltwater/marine, place the board in a sized box and pot it (fill with waterproof material and let dry). If the environment is not extremely harsh, there are clear plastic sprays that work great. If occasional humidity (even rain) is an issue, several coats of this spray will work.

In order of humidity resistance:

Acrylics are easily repairable but give the least protection (Krylon is acrylic)

Polyurethanes give better protection

Epoxies are probably the most durable and difficult to repair.

Poly para xylene(parylene) gives the most complete coverage. It's vacuum deposited and a pain to mask off areas you don't want coated.

Dipping is the only way to get complete coating coverage, even under components, no matter what the choice.

More details will get you a better answer.

There are many coatings suppliers that will give you advice in the hope of making a sale.

Potting, as mentioned above, is effective but almost impossible to repair.

Thanks lyn - Why would I want to use parylene coating? I understand that it is quite a specialized process and expensive.

You probably don't need Parylene, but it will give the best coverage because it's vacuum deposited and it is recognized as a conformal coating.

I'd suggest that you look at moisture vapor transmission rates of the various materials, if moisture protection is the goal.

BTW,all these coatings allow some moisture to pass through them.

Tell us what your environment is. Temp cycle/maximum humidity/and vibration amplitude(if you want the coating to attach/stake the components to the board)

We have a customer that spec's parylene. At this point I'm sure that anyone knows why. It won't be in water, but it will see very high humidities.

If your customer specs it, you need to use it. It's expensive and very difficult to de-mask after coating. In case it matters to you, Parylene is a good UV filter, compared to the other coatings.

What's the maximum temperature the device will see.

Military?

Orbital?

From what I have seen previously, we usually try to protect the environment from PCBs (polychlorinated biphenyls). But then I guess PCBs were used to protect electrical components from the environment....

There's a hole in the bucket, dear Liza....

Tornado, different PCB's, in this case; Printed Circuit Boards

Tom D. (PCB Designer - The green kind, not the chemicals)