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Do I Need More CPU Thermal Paste?

  1. Jul 29, 2009 #1

    minger

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    I just installed a new power supply for my desktop last night. In the process I needed to remove the CPU heat sink. With no thermal paste on hand, I just reassembled the heat sink. The question is simply do I need to clean the CPU and reapply thermal paste since the heat sink was unseated?
     
  2. jcsd
  3. Jul 29, 2009 #2
    You probably should, the thermal paste is designed to fill in the air gaps between the sink and the chip and taking it apart probably unsettled it quite a fair bit.
     
  4. Jul 29, 2009 #3
    Unless you want to fry your CPU, you need to have some kind of thermal compound between the die and the heat sink. Unless of course you have a lapped heat spreader, then you don't need to worry about it.

    If you apply thermal paste, make sure its a very thin layer. Did you remove the thermal pad that was there originally?
     
  5. Jul 29, 2009 #4
    Definitely clean it and apply more paste. I only use an amount about the size of a grain of rice, then spread it evenly with a credit card or something like it. Unless both your processor and heatsink are considerably off from completely flat, it only takes just a little bit of grease. Less than you think.
     
  6. Jul 29, 2009 #5
    Keep in mind that the thermal paste doesn't last forever, even if you never unseat the CPU...it will need to be re-applied in a couple years or so
     
  7. Jul 30, 2009 #6

    minger

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    What is commonly used to remove the old stuff?

    (right now the box is sitting right under by my A/C unit so I'm not too worried for the time being)
     
  8. Jul 30, 2009 #7
  9. Jul 30, 2009 #8
    I always use regular old rubbing alcohol. It's cheap, removes every last speck, and leaves no residue.
     
  10. Jul 31, 2009 #9

    rcgldr

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    Some rubbing alcohols have oils. You can get 91% or higher isopropyl alcohol from most pharmacies.
     
    Last edited: Jul 31, 2009
  11. Jul 31, 2009 #10
    It depends on what you intend to do with it. 91% is perfect for what we're talking about here.
     
  12. Jul 31, 2009 #11

    rcgldr

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    Rubbing alcohol (70%) typically has some oil in it. 91% isopropyl alcohol typically only has water. I've seen higher percentages in the past at pharmacies, but not recently.

    On a side note, I recently discovered that (electric) leaf blowers do a good job of removing dust from a computer.
     
  13. Jul 31, 2009 #12
    91% is the highest i've seen since i've been paying attention. If you want to spend a few extra dollars you could go ahead and get anhydrous isopropanol which is 99% pure...

    http://www.parts-express.com/pe/showdetl.cfm?partnumber=341-407

    I'm not sure if I would advise using a leafblower. With a leaf blower large amounts of air along with small bits of dust and debris are blown onto the motherboards surface which can cause static buildup. With small compressed air cans, there's no high velocity debris to worry about and you can more easily spot-clean needed areas.
     
  14. Aug 1, 2009 #13

    rcgldr

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    Although I've done this a few times myself, it was more of a note that it's possible rather than a recommendation. I did this with the case sides off. I didn't see any residual dust anywhere. Initally I tested on an opened power supply, then I tried it on opened desktop cases. You need to make sure there isn't anything that could be damaged from the high speed flow, like loosely connected wires or any debris of significant size. Also I would avoid over-revving any fans with the air stream.

    Regarding isopropyl alcohol, I think 97% used to be availble decades ago at pharmacies, but I did a web search for it and don't find any hits. You can get 95% ethanol mixed with various toxic chemicals at some stores, and 99% isopropyl at some stores or online.
     
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