What's the stuff covering boutique pedal circuit boards?

[skiraly017]

And where can I get some? Thanks.

Scott

[markr04]

If you're talking about the "clear coat" stuff, it's called "conformal coating". It's like a spray paint, but very pure to prevent conductivity. It's applied to almost all manufactured PCBs from computer motherboards to stompboxes to prevent corrosion, accidental grounding, etc.

http://www.mgchemicals.com/products/protcoat.html

I use a different brand and I can't think of the name right now. In my area, all of the electronic supply places carry it. Fry's Electronics does too. I bet you can order it from many online places too.

[aron]

If it's a big lump of stuff, it might be epoxy glue.

[cd]

If it's a big lump of stuff, it might be epoxy glue.

Bingo.  If you're talking about the black stuff, it's epoxy.  Clear conformal coating won't give anyone any trouble to copy anything  Epoxy is usually in two parts, the resin (plastic) and a hardener - mix the two together, and it hardens to a rock in a few minutes to a few hours, depending on the type you get.  I would use the "in hours" type (i.e. not 5-minute) since it's usually very liquidy, and to place it properly, you have to let it set until it's a bit like chewing gum, then carefully put it on your PCB.  Otherwise it runs.  The clear type is available all over the place (Wal Mart, Pep Boys, Home Depot, etc.) the black colored stuff is available, but tougher to find.  It's possible to color the clear stuff too - there is a specific epoxy coloring pigment.

You can also use JB Weld, which is ostensibly for car repair and whatnot, it dries grey and is impossible to get off without 600+ degree heat (or so the manufacturer says).

I have also seen that "dip grip" type stuff used for gooping (i.e. the kind of stuff you dip your hand tools into to give them a plastic grip... can't remember what it's called), also home weatherstripping/bathtub caulking (careful, may contain volatile chemicals), wood glue, etc. etc.

[petemoore]

Here's my own, personal, [never heard of it anyway]. mojo ground blanket [patented] idea  :idea:
 I typed about this before so please excuse the duplicity...
 Take the pure paint Markr4 mentioned, use about three coats of it, very particular to cover everything...then once over for good measure, then use shielding paint over that and ground it.
 It might do the inductance thing, that's Where the 'problem or mojo' lies in it I think [besides the cost of paints, circuits and time].
 otherwise it might do something for keeping outside interference out.

[Paul Perry (Frostwave)]

If the original poster meant big blobs of black stuff, yes that's epoxy. But if he meant the (usually green) stuff that covers the tracks of a PCB, that is "solder resist" and it is screen printed on at the PCB factory, except where you want solder to stick. I gotta say, it sure helps make hand soldering a breeze! and it makes automated solderign possible

[markr04]

I've seen that stuff too, Paul, but I didn't know what it was. So there could be at least three different substances applied to the top layer of a board? Or would solder resist be used instead of conformal coating at a high-volume PCB manufacturer?

[Paul Perry (Frostwave)]

If you get boards made commercially, it is almost certain you would get the solder resist. (if the board is going to be hand soldered, you want it because the solder tends not to stick to it, & that makes bridging less likely. The PCB layout programs automatically design the resist pattern.
Also, it stops the traces witout solder from tarnishing & helps keep moisture away.
If you are trying to hide the design, then the epoxy goes all over the whole deal.. but as we know, that just encourages people to get out the hot air gun and dental pick. (AllElectronics do a good range of cheap Pakistani dental picks.)

[gez]

It seems to me a lot of time the epoxy is used to disguise the fact that the 'designer' has ripped off someone else's work!  

Blow torch will come in handy when it comes to replacing the electrolytics once they fail...

[Doug_H]

It seems to me a lot of time the epoxy is used to disguise the fact that the 'designer' has ripped off someone else's work!  

That's probably true in some cases. If you look at the pedal biz though, everyone and his brother seems to be building stuff. And when you look at it really closely it is amazing how much of it is based on clones and derivatives of a relatively short list of popular ideas. Anyone with any inkling of a relatively unique idea at all should take some measures to protect themselves. Not that "gooping" a circuit board is any guarantee...

Re. the original subject: I've used JB Weld and it seems to work pretty well.  There are a number of potting compounds available from supply houses. But you have to be careful because some of them get hot (i.e. generate heat) when activated- not necessarily good for temperature sensitive components.

Doug

[Bernardduur]

Is that that stuff that vaporises when you put a hot soldering iron to it?