Alvin777

Q: Thermal Pad Thickness, Brand and Type of GPU Memory (Surrounds the GPU Chip) of Late 2009 iMac?

Hi. I will be repairing (and cleaning after 6 years) the late 2009 iMac coz' the screen has five 2cm thick, evenly distributed,  striped vertical lines (it is still useable in Safe Mode) which indicates a good GPU chip (used to pass all stress tests for GPU and GPU memory) but a subcomponent surrounding it has solder joint fracture coz' it may have overheated during summer (which was a record high, 36 to 42 Celsius) and OS X may have not revved up the fans enough which may have helped cause the solder joint fracture.

 

When I open the iMac on monday, the thermal pads for the GPU's memories (surrounds the GPU chip which I'm gonna use a thermal paste with) may not be in good condition anymore. I was wondering what thickness should the pad be for this iMac's GPU (an ATI Radeon HD 4850  512MB ), what brand and what type (though the thickness may be the most important)?

 

Thank you. God bless. Rev. 21:4

iMac, OS X El Capitan (10.11.1), iMac Late 2009

Posted on Jul 16, 2016 5:49 AM

Close

Q: Thermal Pad Thickness, Brand and Type of GPU Memory (Surrounds the GPU Chip) of Late 2009 iMac?

  • All replies
  • Helpful answers

  • by dialabrain,

    dialabrain dialabrain Jul 16, 2016 6:46 AM in response to Alvin777
    Level 5 (5,890 points)
    Mac App Store
    Jul 16, 2016 6:46 AM in response to Alvin777

    I would contact https://www.ifixit.com/

    If anyone should know…

  • by Alvin777,Solvedanswer

    Alvin777 Alvin777 Jul 22, 2016 10:38 AM in response to Alvin777
    Level 1 (72 points)
    Desktops
    Jul 22, 2016 10:38 AM in response to Alvin777

    Hi. The 3M thermal pad (I may have wanted the Gelid brand more may be on par with Gelid's best performing thermal compund) seller I bought from says it's 1.5mm (from Ati hd4200 series up to 5 series), though when I tested the gaps between the ram chips and the other chips (that are not GPU) that was covered with thermal compound, 0.5mm already wouldn't slip through the chip with the widest gap (measured the by folding strips of paper and by using a digital caliper to measure the folded paper); but seller knows best- I'll go with 1.5mm. It may need 3 times my calculation for the chips to get a good pressure, I guess, coz' the vram and other chips don't have the spring loaded clamp that the GPU has.

     

    God bless. Matt. 16:18

  • by Alvin777,

    Alvin777 Alvin777 Jul 26, 2016 6:16 AM in response to Alvin777
    Level 1 (72 points)
    Desktops
    Jul 26, 2016 6:16 AM in response to Alvin777

    Hi. Correction it seems it needs two thermal pad sizes 0.5mm for the GPU VRAMs (usually Samsung) and for the small square chips at the back (part of voltage regulator I believe) and then 1mm for the MOSFETs, the bigger square ones (I believe it's also part of the voltage regulator). GPU could be a very good think spread of thermal paste.

     

    God bless, Rev. 21:4

  • by josuamiliiii,

    josuamiliiii josuamiliiii Sep 7, 2016 4:40 AM in response to Alvin777
    Level 1 (4 points)
    Sep 7, 2016 4:40 AM in response to Alvin777

    Personally I use k5 pro to replace thermal pads. It is a thermal pastes but it was designed to replace pads ONLY (since it is thicker than the others).

    This way you won't ever have to worry about thickness or size