Conformal coating

[mary meullion]

Does anybody out there conformal coat their boards, why, how much does it cost, and do you have any information on the subject.

[Tom]

Mary,

The most popular reason why someone would add conformal coating to a board is to keep moisture out. Every assembled PCB that is exposed or possible exposure to the outside elements gets conformal coating.

Conformal coating in done at the assembly shop, after the board in fully assembled and passes test.

You need to call a couple of assembly shops to get the cost because there are several different types of coating and each assembly shop has their own application method. Use the PCBServices Info Bank to contact multiple assembly shops. You can locate the info bank at:

http://www.pcbstandards.org/downloads/Metric%20Environment/Documentation/PCB%20Stuff/PCB%20Services%20Info%20Bank/

[randychase]

Another reason for comformal coating is to increase the voltage spacing distance. It's been a while since I used it, but we did this for military work. Also, I have used a black conformal coating to make an assembly harder to reverse engineer.

[dclegg]

randychase -

i'm interested in black conformal coating on electronic hardware that will ultimately operate in an outdoor environment. can you make any recommendations?

[randychase]

I think Humiseal was the most common manufacturer of potting compounds and conformal coatings.

Also check out-

http://www.mgchemicals.com/products/832b.html

[dclegg]

thanks.

is there any need to apply conformal coating prior to potting a pcb in a 2 part polyurethane? does the coating provide any necessary relief from the potting (mechanical, shrinkage or thermal)? and does that define whether the coating should be soft or hard? i would like to use the black coating but noted in at least one specification that its harder than clear coating. would that matter?

thanks for any help.