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dfidler 12th December 2010 07:31 AM

What is this stuff?
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Hey Guys,

As part of my education in electronics, I recently bought a used amp to take apart and see how it ticks (I've tried reading books but without something to dig through with a DMM, the knowledge wasn't sticking).

Anyways, in the attached picture, there is some kind of solid blue thermal compound holding an IC to a heatsink. By solid, I mean really hard; hard enough to resist scoring by my thumbnail and it's properly bonded to the heatsink.

Does anyone know what this stuff is (brand name too?) and how to safely remove it from the IC?


Note: Due to the limited gamut of sRGB, the blue has come out a little wierd; the actually blue colour is actually a little lighter than pictured. I also realize that a question like "what is this blue stuff" is probably a shot in the dark but google hasn't given me any real contenders so....

peranders 12th December 2010 07:34 AM

This is a transistor which is a part of circuit for bias adjustment vs. temperature. The blue may be some epoxy glue. The stuff for this isn't critical. It should also hold for 100 degress C or so and be able to hold a small transistor.

ostripper 12th December 2010 07:34 AM

Looks like thermal epoxy ... try Acetone.

dfidler 12th December 2010 09:39 AM

Thanks guys. I was assuming that it was thermal compound because it's mounted to the heatsink and was thinking along the lines of it being a temp sensor as well. Would regular epoxy glue really be a sufficient heat transfer medium for this kind of application?

If so, I'll go through a few brands to see if I can find one whose color matches.

@OS - re: acetone, thanks! :)

Note: I noticed some scoring on the heatsink just under the 'epoxy', presumably to help it hold so I think you're right, it's probably just epoxy. I'm just worried about the specific properties of it.

I want to be able to remount this thing when i'm done fiddling with the PCB so I want to make sure that I don't cook it (or change the sound) by putting the wrong stuff on there. :)

dfidler 12th December 2010 09:42 AM

I wonder if this (or something like it) isn't the stuff here: Alchemie Limited: Epoxy Resins

Boscoe 12th December 2010 10:05 AM

Is it brittle? Can you crack it or perhaps knock the top of it softly to see if will break?

968driver 12th December 2010 10:07 AM

blue compound
this is an adhesive with good thermal conductivity. Farnell has some blue adhesive with these thermal properties.

dfidler 12th December 2010 02:59 PM

yes, it's quite brittle; it's coming off in little bits (flying across the room); so it's quite hard.

dfidler 12th December 2010 03:07 PM

@968driver - thanks, I'll have a look :)

TMHutson 23rd December 2010 09:49 PM

Thanks for the idea of buying amp to take apart. I go to local swap meets all the time, and find good deals. Got a yamaha HTR5540 for 30 bucks. I have seen old tube amps, SS amps, recievers, THX elite pioneer stuff.
Did you buy a working, good amp, or bad one?
Thanks.. Todd

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