"Dried" electrolyte or conformal coating?

[eccerr0r]

I was wondering when I was trying to remove/replace SMT caps. As I am using a hot air rework, it heats up much more than just the solder joint. What I noticed is that the once normal looking board is browning up where I point the hot air.

The cap was dead and still dead, but is the stuff on the board that turned brown (must be some sort of organic?) or some conformal coating?

I still cant believe virtually *all* of the caps are bad and not just one or two...

[kc8adu]

Re: "Dried" electrolyte or conformal coating?

common.
they stink too.
just replaced all in an icom 2100h.
they stained the board.

[eccerr0r]

Re: "Dried" electrolyte or conformal coating?

I guess I find it weird, is this stuff conformal coating or cap guts. It's clear before heating... If it stinks it's capacitor guts?

[stj]

Re: "Dried" electrolyte or conformal coating?

it could also be flux,
some comany's used to spray the whole pcb with a layer of flux and not clean it off after.

[Behemot]

Re: "Dried" electrolyte or conformal coating?

Or insulation lackquer they spray on the board after it's finished?

Hot air gun is very bad tool for this. If you point it too long onto single spot, the *board iself* will start burning. If you have rwork station, that is better as it is much more focused, but still can burn the board. Grab TWO solder guns and heat both the electrodes simultaneously. That way you can unsolder them easily.

[SteveNielsen]

Re: "Dried" electrolyte or conformal coating?

Some tool maker oughta make a special solder tip with a gap so it's like two tips, and possibly make it adjustable or like tweezers for different side smt sizes. That'd be a trick, huh?

Using hot air also loosens unintended parts nearby and I've lost a couple that way. Then you're screwed if they aren't marked and have no schematic.

Some flux compounds are really stinky and nasty. I worked in a circuit board factory that used some horrible flux that I developed an acute sensitivity to. It made me physically ill and I had to leave that job because of it.

[stj]

Re: "Dried" electrolyte or conformal coating?

Some tool maker oughta make a special solder tip with a gap so it's like two tips, and possibly make it adjustable or like tweezers for different side smt sizes. That'd be a trick, huh?

http://www.jbctools.com/pa120-a-micr...roduct-49.html

[Behemot]

Re: "Dried" electrolyte or conformal coating?

That can do, if it provides enough power. These tiny tips, especially with only 40 W heating element, are usually pain in the ass to work with slightly larger components. The tip cools down immediatelly and than you have to heat it who knows how long to melt the solder. So I am afraid that for D8-D10 SMD caps it will be quite useless anyway.

[SteveNielsen]

Re: "Dried" electrolyte or conformal coating?

Well there we have it then. Very nice.

[eccerr0r]

Re: "Dried" electrolyte or conformal coating?

Ugh I think I killed it. You're right, might be dangerous to use hot air rework. I didn't see the other side of the board...

Albeit it looks like things are still OK, but who knows...

[psychophat]

Re: "Dried" electrolyte or conformal coating?

Did you preheat the bottom area before doing it, that helps quite a bit (around the base 100c for a min). On top set the air to low, very low if there are small components very near. And use a small tip and run it around the cap base diagonally.