I use the thin spread method, if the paste is still in good shape, I just re-spread it really thin again, cleanup any small ammounts of goop comming out the sides, and squish it back down again. If it is aged, looking dry, hardening or the cpu did not remove easily , then it is time to refresh it.
Because I will check the "seating" and the metal to metal contact and lean and pressure , by testing it , I get oppertunity to reuse it. When there is a lot of Time that it is removed for, I cover both sides with plastic, then when it is about to go back together, I decide then if I am going to refresh it or not.
There are different themal interfaces that act, and are different, some are not reusable. There is also the thermal setting/shifting, I figure if it "thermally" changed once and I can get it in place again, it can thermally change again :-) . I have not had any problems re-using the normal stuff they sell us.
If your using the "cross" (strips of goop in a X pattern) pea drop (blob in the center squished out) or Line (Line that gets squished out) methods. These methods are used to keep air out, as the pressure is applied the thermal compound squeezes out from central areas, so air is less likely trapped, pushing thermal compound out of areas. All of these methods would prefer the majority of the thermal compound to be removed. Once removed nobody is going to reuse that.
The above methods work great for keeping air gaps out, but also require that the correct ammount be used, and that the sink be applied straight down, and in one move. This works great when you have lots of working space, 4 hands, and mounting designs that have it comming down straight and easy.
1Why do you keep removing the heatsink? – Daniel R Hicks – 2012-02-06T01:40:56.543
@DanH Vigorous movement seems to jar it loose, so I have to remove it and remount it occasionally ... – C. Ross – 2012-02-06T02:03:13.097
3Then the question is why is the computer being shaken so hard that the heatsink actually comes loose? They are specifically designed to hold tight against the CPU. Consider checking if it is correctly attached (eg tabs are all in place/screws are screwed down/etc. depending on what socket CPU it is). – Synetech – 2012-02-06T02:13:13.480
@Synetech I'm working on that, I think the pins are having difficulty. – C. Ross – 2012-02-06T13:43:40.503
What pins‽ The pins on the CPU?
o.O
If so, you may have bigger problems. – Synetech – 2012-02-06T19:40:38.000@Synetech No, no, it's a Socket 775. The Pins that hold the heatsink and fan on. I already broke one assembly by breaking a pin. – C. Ross – 2012-02-06T19:55:13.077
1Ah okay, I see. Then your priority should probably be to get a new heatsink, otherwise you’ll just end up wasting a lot of thermal compound, really quickly (which will end up more expensive than a new heatsink). Also, check local classifieds (especially online ones like Kijiji/eBay Classifieds) to see if anyone in town as one they can give you for free or a couple of bucks). – Synetech – 2012-02-06T20:00:26.690
1Depending on the type of paste it can be re-used reliably. – Moab – 2012-02-07T00:29:16.387