Conformal coating Sockets ?

[DZ12488]

I have this very expensive pcb that has no protective coating on it and since it is to be deployed in a temp changing environment , it will se some condensation . SO my question is WOULD YOU put conformal coating on PIC Chips that are plugged in a socket ? I know that is where the corrosion will start . Murphy's law . I am using Mg Chemicals silicone coating Part# 422B and brushing it on . Any insight would greatly be appreciated from those of you that are more experienced than me . Thanks

 

[dknguyen]

I would say no because using sockets in a harsh environment seems like bad practice to begin with. I would use contact lubricant at like the MG Chemicals Super Contact Cleaner with PPE. The PPE part is important because that's the sealing lubricant part.

Applying conformal coating to the chips after they're plugged into the sockets essentially makes the installation permanent, in which case you might as well do away with the socket and just conformal coat.

Furthermore, with silicone conformal coating, any air gaps underneath the coating (and there will be air gaps in something like a socket) will allow moisture to collect and not escape. Silicone conformal coating does offer protection against moisture but since it is slightly permeable, any air gaps will result in water collection.

"One key point here to remark is that silicone coatings exhibit high water vapor permeability, combined with excellent water repellency. In terms of protection, this is the ideal scenario, as on one hand silicones are assisting the easy elimination of surface moisture on the substrate after application. On the other hand they protect the surface from any liquid water ingress."

That snippet portrays high permeability as a positive, though other articles portray it as a negative. It's definitely a negative though if you have air bubbles.

 

[unclejed613]

I have this very expensive pcb that has no protective coating on it and since it is to be deployed in a temp changing environment , it will se some condensation . SO my question is WOULD YOU put conformal coating on PIC Chips that are plugged in a socket ? I know that is where the corrosion will start . Murphy's law . I am using Mg Chemicals silicone coating Part# 422B and brushing it on . Any insight would greatly be appreciated from those of you that are more experienced than me . Thanks

looking at that picture, it looks as if it's already conformal coated, or at least most of it is.

 

[DZ12488]

OK yes I did coat the board as you can see in the picture of the first post , however I had intended to coat the PIC in the sockets on the lower left corner of the picture with the chip in place then coating it . But my gut feeling tells me not to coat it and I would like professional advice out there.

 

[dknguyen]

Also, there are other contact lubricants that will seal the connections other than PPE. It's just the one I know.

Read this:
https://www.circuitspecialists.com/pdf/801B_faq.pdf

This is also pretty cool too:
https://www.chemassociates.com/products/findett/PPEs_LubEng.pdf

 

[DZ12488]

Great Thank you for your advice !!