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darthrazz

macrumors newbie
Original poster
Jun 13, 2022
5
0
Hi , I recently reapplied thermal paste to my GPU cards and noticed a few spots on the copper were fading, will this affect the card in any way or cause it to not cool properly?
 

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tsialex

Contributor
Jun 13, 2016
13,064
13,274
Seems that the copper oxidized, did you tried polishing it?

While works fine for MacPro5,1 heatsinks, I've never tried for a MacPro6,1 one, but a light polishing without any copper removal should work.
 

julik_tar

macrumors newbie
Mar 23, 2017
29
4
I have something similar on one of the GPU copper plates, it's even more sever. At first sight it looked like caked thermal compound (the machine hasn't been disassembled for 5 years or more), but I could not scrub it off. There is also something looking like a fissure. I reapplied the thermal compound, but it looked strange - maybe corrosion? It did feel like the patch was recessed into the copper plate, so for now I just filled it with thermal compound, but...
 

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loby

macrumors 68000
Jul 1, 2010
1,831
1,453
The unit does (or did have an overheating problem, can't imagine the copper frying.

Maybe also cheaper parts...? Would not be surprised...
 

tsialex

Contributor
Jun 13, 2016
13,064
13,274
I have something similar on one of the GPU copper plates, it's even more sever. At first sight it looked like caked thermal compound (the machine hasn't been disassembled for 5 years or more), but I could not scrub it off. There is also something looking like a fissure. I reapplied the thermal compound, but it looked strange - maybe corrosion? It did feel like the patch was recessed into the copper plate, so for now I just filled it with thermal compound, but...
The unit does (or did have an overheating problem, can't imagine the copper frying.

Maybe also cheaper parts...? Would not be surprised...

I've seen corrosion like this in the past, my bet is on a drop of sweat from the person that was installing it and was not cleaned, then the copper corroded over time. Weird, but happens. You should clean and lap it with a 600 then polish with 2000 wet sandpaper.

This type of corrosion is more frequent seen with HVAC parts that had flux applied for soldering/brazing, if you do not clean it thoroughly, the copper will corrode and some times even disintegrate over a long period of time.
 
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julik_tar

macrumors newbie
Mar 23, 2017
29
4
I was thinking about buffing it in some way but I'm a bit worried that I will take too much off - so there would be a cavity - and I don't know how thick the copper plating is. I presume the thermal core is not entirely copper right?

That said, I see used thermal cores on eBay for about 20-30 euros, might be cheaper and easier than cleaning.
 

tsialex

Contributor
Jun 13, 2016
13,064
13,274
I was thinking about buffing it in some way but I'm a bit worried that I will take too much off

Just remove the corrosion, should be just a light lap/polish with a wet sandpaper.

I usually start with an already used wet sandpaper to see if I can remove the corrosion without removing any of the good copper around, then after the corrosion is removed I start the lapping process - there are lot's of YouTube videos about this process.

- so there would be a cavity - and I don't know how thick the copper plating is. I presume the thermal core is not entirely copper right?

I never inspected this heatsink assembly thoroughly , but usually Apple heatsinks are full copper core and not just plated aluminium.

That said, I see used thermal cores on eBay for about 20-30 euros, might be cheaper and easier than cleaning.

Yes, you don't already have the wet sandpaper, buffing compound and lot's of time, it's probably better to buy the whole assembly if you can find it for just €30.
 
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julik_tar

macrumors newbie
Mar 23, 2017
29
4
Fwiw some folks say there is a vapor chamber underneath 😱 might just replace the thermal core.
 

julik_tar

macrumors newbie
Mar 23, 2017
29
4
Hmm - it felt like the corroded recession in the coldplate was not microns thick, more like a third of a millimeter. So what kinda scared me is that you have to take material off all over the plate, and quite a bit of it. Either way - I agree with you that it is probably more cost-effective to replace the thermal core. Just need to find the right thermal pads.
 

julik_tar

macrumors newbie
Mar 23, 2017
29
4
Decided to replace the entire thermal core to be on the safe side, reused the old thermal pads. All seems to be working.
 
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