When yellow glue goes brown ...

Sounds a bit like one of those late night cable programs "When Good Snakes Go Bad" :-)

We have discussed this topic on here a number of times, and one thing that usually comes up is how you get the stuff off. There's a switcher that I do which has a pair of small radial electrolytics 'folded over' and glued down on top of a whole bunch of surface mount components on the small drive / control sub-board. Some of the components that are under the glue run quite hot - a zener for instance - and this has a double whammy effect on the board in that first it turns the glue brown, which then becomes conductive, and then it also does a nice job of conducting the heat into the caps, to ultimately twat those as well.

The glue gets right down between the pins of the PWM / driver IC amongst other places, and is an absolute bitch to remove, without damaging assorted gnat's-bollock sized support components in the vicinity.

Well, today, quite by accident, I discovered that my favoured flux removal chemical - Servisol Deflux 160 aerosol - does a nice job of softening the glue up. Not quite to the point of actually dissolving it, but enough that it can then be fairly easily picked off with a fine scalpel blade, and then scrubbed off with an old toothbrush, once you've got the thick of it off.

Arfa

Reply to
Arfa Daily
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En el artículo , Arfa Daily escribió:

I've used IPA (isopropanol) and a half-inch paintbrush with all but an inch of the bristles cut off for years. No scraping needed.

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Reply to
Mike Tomlinson

I reckon you must be using either different IPA than me, or dealing with a different yellow glue then ! Before this week's discovery that Servisol 160 has at least a 'softening' effect, and loosens its attachment to the board and the components that it has stuck to, I've never found anything readily to hand that as much as touches it - and I use loads of electronics grade IPA for board and general cleaning. Have I just been unlucky ? Has anyone else found that they can get the stuff off with IPA ? There has been a lot of discussion over the years on this glue, and the effects of it ageing and turning brown, and one of the recurring questions in the threads has always been how to get the stuff off without inflicting damage on the board, hence the reason that I thought it worth passing on this latest finding ...

Arfa

Reply to
Arfa Daily

removal

the

160

and

always

hence

You've omitted the biggest problem , itself or its breakdown product going conductive over time.

Reply to
N_Cook

En el artículo , Arfa Daily escribió:

Possibly. I'll look up the RS part number when I get back into work and post back here with it.

Just gentle scrubbing with the paintbrush and plenty of IPA, leave it a while, go back and it (the brown/yellow goo) falls off. It doesn't dissolve. The silicone-based stuff is another story, however...

Hell yeah, tips always welcome :-)

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Reply to
Mike Tomlinson

In article , Mike Tomlinson writes

This is the stuff that works

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The main constituent seems to be cyclohexane.

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Reply to
Mike Tomlinson

Noted. Cheers

Arfa

Reply to
Arfa Daily

Ah. So are you saying that it's not in fact IPA that you are using ?

Arfa

Reply to
Arfa Daily

En el artículo , Arfa Daily escribió:

Yes, apologies. I have both IPA and the above stuff on my bench. The 'stuff' is what works to get rid of the brown goop.

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Reply to
Mike Tomlinson

OK. That makes sense then, Mike. I thought I wasn't going mad ! I use a lot of IPA, and I was certain that it didn't touch the yellow glue. Seems like the stuff from RS that you are using, acts on it in much the same way as the Servisol 160 - that is that it sort of softens it to 'marzipan', and breaks its bond to whatever it's stuck to. Not perfect by any means, but better than trying to just pick the stuff off ...

Arfa

Reply to
Arfa Daily

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