Is instant glue safe for use in electronics?

[SeanB]

Re: Is instant glue safe for use in electronics?

I use a 2 part epoxy to hold heatsinks to chips. I prefer Pratley quickset steel, but you can use Araldite quickset white epoxy or pretty much any other 2 part epoxy as well. Clean both surfaces, then sand the heatsink and chip top lightly with 220 grit waterpaper and wipe both sides down afterwards with solvent ( acetone, IPA or even methylated spirits, then mix a little eopxy and apply a thin layer to one surface, then clamp the 2 together until cured. I tend to just mix a match head sized bead of each tube on the top of the chip in the middle with a paper clip, then place the heatsink on it and press down to spread it out to cover the chip. then place a small weight on top and leave for a half hour till cured past gel state. then you preferably leave for 24 hours or gently heat to 70c to hasten the cure. Generally you get a 30C drop in chip temperature, using a small heatsink with fins about 20mm tall covering the entire chip top. Common source of the heatsinks are old motherboards, taking the north bridge, south bridge and memory heatsinks.

[Topcat]

Re: Is instant glue safe for use in electronics?

That's what I am most afraid of.
I have several motherboards that could benefit from some heatsinks on some of their MOSFETs... but I don't know what to glue down the heatsinks with. AS thermal adhesive is $15 for 7g - too much for fixing up an old motherboard that's probably not worth even that much.

Wood glue seems like it will crack with the heat-cycles, thus causing the same problem you mentioned. I haven't tried it, though. (But I am pretty sure that is what's going to happen.)

Hot glue melts at too low of a temperature and becomes quite gooey even at under 100C.

Bathroom silicone releases acetic acid IIRC, so that's likely a no-go on heatsinks and electronics, I think.

Guerrilla Glue? Anyone try that before?

JB Weld. Done many that way.

[momaka]

Re: Is instant glue safe for use in electronics?

JB Weld. Done many that way.

Sweet!
$6 for 50 grams? I'll take that any day over the AS adhesive. Thanks for the suggestion.

but what have you go in mind?
most of the heatsinks you see on mobo fet are for looks.
the resin package is a thermal insulator - your heatsink would need to go onto the tab.

if you look where the fets are soldered, you will see a shitload of copper via's to the back of the board,
and these go into big tracks.

this is a form of heatsink embedding

Right. But there are situations where either the copper planes on which the MOSFET is soldered to is too small or the heat dissipation by the MOSFET is just unrealistic for an embedded copper plane heatsink to take care of. I have the latter (stupid ASUS design on a AsRock motherboard), and the MOSFET's case temperature is anywhere between 70C and 80C depending on the room temperature. There are two caps next to it. They used to be small 8x12 mm OSTs and they would get cooked. I replaced them with tall 8x25 mm Panasonic FJ. They still get insanely hot, but the MOSFET is about 5C cooler on average. I think a large enough heatsink with decent thermal coupling to the MOSFET should help at least another 5C.

[Behemot]

Re: Is instant glue safe for use in electronics?

Does that JB Weld thing have high enough heat conductivity?

I use akasa thermal pads lately, they are those soft types with adhesive on both sides, seems to work OK so far, I'll see in a few years if it is OK or not cooling insanely hot FETs in displays

BTW check this improvisation of mine

[Topcat]

Re: Is instant glue safe for use in electronics?

Does that JB Weld thing have high enough heat conductivity?

I use akasa thermal pads lately, they are those soft types with adhesive on both sides, seems to work OK so far, I'll see in a few years if it is OK or not cooling insanely hot FETs in displays

BTW check this improvisation of mine

Yes, it does conduct quite well. See my old DVD266URN thread... Thanks to JB weld and some properly placed heatsinks, it brought a pretty much unusable board to perfectly stable.

Now, I do like your improvisation there.....soldering washers to diodes and transistors. I'd have never thought of that. If theres just a little air moving, that would make a noticeable difference I'm sure.

[stj]

Re: Is instant glue safe for use in electronics?

Right. But there are situations where either the copper planes on which the MOSFET is soldered to is too small

then maybe you could create some heatsinks with a stepped side on them that makes contact with the top of the tab.

[Behemot]

Re: Is instant glue safe for use in electronics?

It was the only thing I have come up for cooling these small TO-251 transistors, they are too small to atach any heatsink to them (I also did not have any glue or adhesive by that time). And as for diodes, only solution I have seen in old electronics was either using bigger diodes (which also have too thinck electrodes), or soldering them to something (also applied for TO-220 transistors, it was not that uncommon back in 90s). So I just soldered something to them

then maybe you could create some heatsinks with a stepped side on them that makes contact with the top of the tab.

Quite many displays, especially Samsung and LG, use some thin sheetmetal, as a heatsink. It is soldered few centimeters away from transistor, the heat is transfered from pad to copper layer on PCB and from there to those heatsinks. At some boards there are only the spots for them. Check for example http://diit.cz/clanek/lg-flatron-w22...ertorem-oprava

[momaka]

Re: Is instant glue safe for use in electronics?

BTW check this improvisation of mine
http://diit.cz/sites/default/files/chlazeni.jpeg

0.o that's ghetto mod territory right there! But I like it .

I did something similar on a Dell LCD monitor - I soldered a long piece of used desoldering braid to the pads of the transistors and bent them like a heatsink.
Here's another variation of that I did afterwards:
https://www.badcaps.net/forum/attach...5&d=1357084641

then maybe you could create some heatsinks with a stepped side on them that makes contact with the top of the tab.

No space to solder to the tab - it's backed up against the memory slots.

[PeteS in CA]

Re: Is instant glue safe for use in electronics?

Like the washers adaptation. The plating on the washers have to be solderable (e.g. tin-plated). A good variant might be to use solder/crimp ring lugs, which are tin-plated and available in a wide variety of sizes.

[stj]

Re: Is instant glue safe for use in electronics?

go to a plumbing shop & get copper washers.

[Behemot]

Re: Is instant glue safe for use in electronics?

No need for that, just use high-enough powerfull soldering iron and enough sodlering flux. I think these are native iron washers. Maybe nickel-plated but I don't think so.