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Old Jul 28, 2013, 01:17 AM   #1
fotophil
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Heat sink detached 2008 Max Pro Logic Board

I opened my 2008 Mac Pro for dust removal and noticed that a large (2 1/2 inches x 1 1/2 inches) black heat sink was laying on the left end of my video card. The heat sink apparently fell off a logic board component located to the left of the four PCI slots. There are two chrome plated spring clips attached to the heat sink. I located a photograph of a 2008 Mac Pro logic board that shows the heat sink being attached to the logic board in which the chrome clips appear to hook into the logic board. My logic board appears to have only one of the two necessary hooks so I don't know how to reattach the heat sink. I have owned the computer since new and it has been in the shop only once about a year ago for some sort of logic board service. Since I have not had the machine open, I assume the heat sink sink fell off during service. I use the computer for 8 ton 10 hours daily and it runs fine with no apparant overheating. Can anyone identify the component?

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Old Jul 28, 2013, 01:25 AM   #2
666sheep
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It's the southbridge. You can use adhesive thermal pad/tape to place the heatsink back on chip.

Last edited by 666sheep; Jul 28, 2013 at 01:36 AM.
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Old Jul 28, 2013, 06:15 AM   #3
DanielCoffey
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There is also the Arctic Silver Thermal Adhesive. It is a permanent adhesive in two parts like an epoxy.

http://www.arcticsilver.com/arctic_s...l_adhesive.htm

Regardless of whether you used the thermal epoxy or an adhesive pad, you would still have to thoroughly clean both the underside of the heat sink and the southbridge chip. Personally I would use ArctiClean for that but there are plenty of alternatives.
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Old Jul 28, 2013, 10:18 AM   #4
fotophil
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Heat sink detached 2008 Mac Pro Logic Board

Thanks for the input. Given the tight space surrounding the logic board I would feel more comtortable using an adhesive tape product rather than the epoxy. It will difficoult to hold the heat sink in place while the epoxy sets as well as the possibility of excess epoxy causing problems. I assume that the tape product will hold the heat sink in place immediately upon placement.
I searched the web and found a line of thermal adhesive tapes made by 3M Company. There are several thicknesses and several thermal conductivity to choose from. Any suggestions? The heat sink and matting surface of the chip are covered with silver paste which is soft. What type of solvent would be good for removal of the base.
What is the functiion of the "southbridge" component? Since mine southbridge may have been running all day, everyday for over a year without the heat sink I wonder what damage way already have occurred? I don'tunderstand how the heat sink became detached. I can see the one loop on my logic board which would have held one of the clips but thee is no sign of the other loop. I would if the technician broke off the loop while servicing the logic board. Anyway what is done is done so now I need to reinstall the heat sink.
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Old Jul 28, 2013, 11:08 AM   #5
666sheep
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See attached picture. It's 2006 board but southbridge heatsink on 2008 one is mounted in that same way.

Clean old thermal paste with rubbing alcohol/isopropanol. For thermal pad choose one with maximum possible thermal conductivity, but not very thick. Kinda compromise one.
Southbridge maintains I/O functions (in general) and does not run particularly hot. But if they put a heatsink on it, it's certainly not without a purpose. If you're not experiencing any USB or disk problems, most likely no damage is done.

Thumb resize.
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Old Jul 28, 2013, 11:55 AM   #6
fotophil
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Heat Sink detached 2008 Mac Pro Logic Board

The 2006 photo shows the same setup as my 2008. Although the heat sink is rather larger (1 1/2 x 2 1/2) the actual contact area cover ed with silver paste is only 1 square inch.Although I have not yet been able to locate a source of small quantities of 3M tape, there are sources fora variety heat sink assemblies including tape but none are my size. Thanks for the alcohol cleaning tip 0 now all I need is the tape. I wonder if the epoxy heaat transfer materials are quick setting. I could probably hold the heat sink in place for a couple minutes. I have not experience any disc problems so maybe I have been lucky.
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Old Jul 28, 2013, 12:23 PM   #7
666sheep
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If you're in the US, try here.

Regarding application of Arctic Adhesive: http://www.arcticsilver.com/pdf/appi.../ins_aapxy.pdf
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Old Jul 28, 2013, 12:40 PM   #8
fotophil
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Heat sink detached 2008 Mac Pro Logic Board

Thanks for the links. Artic Silver makes both analumina ceramic thermal adhesive and a silver thermal adhesive. The curing times seem similar - like an hour. What are the differences for the South Bridge application? In reading the forums, it seems that the thermal tape products can also be difficult to work with - especiaaly removal of the backing paper. Do you have any experience with the 3M tape product? I really am concerned about maintaining good contact pressure during the hour curing time of the epoxy. There is no way to use clamps and the original spring clips will not work.
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Old Jul 28, 2013, 01:00 PM   #9
DanielCoffey
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Lay the MP down on its side so the logic board is horizontal - then you don't need to apply constant pressure.

You only need the tiniest amount of the epoxy as it spreads thinly. I would suggest mixing somewhat more than you need to get it well combined - I used a flattened satay stick on a piece of hard plastic as a mixing board.

Then apply about two rice grains worth to the centre of the chip and spread it almost to the edges. When the heatsink is pressed on it will spread it the rest of the way. Don't rotate the heatsink - just put in place, press it lightly then let it cure.

You will have about a 5-minute working window after mixing the epoxy to it becoming tacky so get everything you need ready first.

EDIT : my use of the epoxy was on fitting a third-party cooler and heatsinks to my stock Apple 5870 about two and a half years ago and it has been working perfectly until I retired it by fitting a flashed 7950 3Gb card.

LINK : http://forums.macrumors.com/showthread.php?t=1097022
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Old Aug 2, 2013, 12:43 AM   #10
fotophil
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Heat sink detached 2008 Mac Pro Logic Board

Thanks to my forum friends I was able to reattach the heat sink to my Southbridge. I ended up using the ceramic epoxy Artic Product. Although I was able to locate 2 inch squares of the 3M thermal conductive adhesive tape, it seemed that proper positioning the heat sink with tape would more difficult.
Thanks again for the help
Phil Lindsay
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