Conformal coating and socketed parts

[CodeMonk]

Several places If worked over the years (started working in electronics in 1981) used conformal coating.
Most was spray on, one place (JPL) we brushed it on then stuck the board in a vacuum chamber to remove the bubbles.
But, speaking from memory, all the parts were soldered in. None that I recall were socketed.
I worry about the conformal coating seeping in and messing up the contact with socketed parts.

Anyone have any thoughts on this?

[chi_boy]

What is conformal coating?

Is the coating permanent?  Or can it be removed?

If it's permanent, why not just touch a little solder in the socket?

[CodeMonk]

Think of it as a clear coat that you would out on an enclosure (but generally a softer material).
Its mainly used to prevent corrosion.

And yeah, it can be removed.
I once had to replace an IC on a board that had a good 1/8 thick layer of the stuff. Took me 2 days to replace that part. But hey, that was for NASA, and they are VERY picky. Wanted no scratches on the board or any of the surrounding coating disturbed.
Theres probably something you can soak the board in the remove it.

[chi_boy]

If it took 2 days to change an IC, I would say it's permanent.  I assume you are talking day job hours too, so ~12 hours of effort?  I wouldn't think you would want to use that on a board you are considering modifying later.  Based on the amount of available "fun" time I have, I would sooner buy a new board and rebuild before spending that much time just to get to a part.

Also, if the material if fairly thick in consistency, I would guess that it wouldn't be able to wick into the contacts of a socket to be a problem.  I would test it to be sure though.  Some sockets on a perfboard with wires to make a continuous circuit should make a good enough test.  Test for continuity before and after coating.

[John Lyons]

After the conformal coating is dry/cured it's stable isn't it?
It should not creep into other areas I would not think.
A lot of ICs use sockets and conformal coatings right?
Should be ok I think.

john

[anchovie]

My last job before my current one was for a company that made all sorts of electronic assemblies as a subcontractor and many of the military jobs required conformal coating - brush-on, spray-on or dipped. Components such as sockets and PCB-mount connectors were simply masked off with tape, or in certain cases the pads on the PCB would be covered with peelable mask on both sides, and the component would be soldered in after the coating had cured and touch-up would be done with a small brush if necessary. As long as sockets are properly masked there shouldn't be a problem, and in the case of connector pins any stray coating can be easily removed with a scalpel blade.

[Paul Perry (Frostwave)]

There is special stuff you can use for masking, it's a latex rubber solution used in spray painting.
I've even seen it used to close off a part of a circuit board before it is wave soldered (in this case, some through hole pots were put on the solder side of the board, so that section had to be masked off while the majority of components were being soldered).
Note that when one is gunking a circuit, unless the circuit board & components are REALLY CLEAN and DRY you are likely sealing in problems!

[CodeMonk]

If it took 2 days to change an IC, I would say it's permanent.  I assume you are talking day job hours too, so ~12 hours of effort?  I wouldn't think you would want to use that on a board you are considering modifying later.  Based on the amount of available "fun" time I have, I would sooner buy a new board and rebuild before spending that much time just to get to a part.

Also, if the material if fairly thick in consistency, I would guess that it wouldn't be able to wick into the contacts of a socket to be a problem.  I would test it to be sure though.  Some sockets on a perfboard with wires to make a continuous circuit should make a good enough test.  Test for continuity before and after coating.

That was NASA. They do pretty much everything in the extreme.
Most conformal coating is not much thicker than a single clear coat you would put on an enclosure.

As I was driving home from a job tonight, I was thinking about this.
One place I worked at years ago, we used these little rubber pieces (various shaped tubing) and such to cover pieces that we did not want coated.

[drewl]

just be careful, most of that stuff is toxic especially when you go heating with an iron.
I've also worked with it alot, mostly on MIL-Spec stuff, we actually had a gas mask for applying it with a vented booth one place I worked.