thermal pad vs copper shim usage and thickness

[cov3rt]

i was wondering if anyone knows if it's possible to substitute a thermal pad with a copper shim for gpu cooling if the thermal pad was used as the original part? since the shim would not compress, it would seem that i would need one considerably thinner than the thermal pad, but there are other issues. for one, a lot of manufacturers don't list the specs of the exact thickness of the thermal pads they use for the gpu or chipset, another thing that is unclear is whether or not i could use a copper shim if the heatsink already has copper surfacing for the gpu and / or chipset portions. what i mean by this is, would it be ok if i used thermal paste between gpu and chipset die, placed shims on top of them, and then thermal paste on top of the existing copper surface, or would this be an issue? the only experience i've had with using copper shims was on the dell latitude d630 where i replaced the thermal pads with shims for the gpu and chipset portions with thermal paste, and it ran a lot cooler, but the heatsink's surfaces weren't copper plated, just normal. the copper shims i used were 1.2mm in thickness. also, i was wondering if it's ok if the either the thermal padding or copper shims are larger than the die itself for the gpu or chipset? i mean, it would be impractical to have to buy separate sized shims or pads, just so they can fit only in the die portion. the reason why i would wan't to use the bigger ones is better universal compatibility and if possible, by using a shim or thermal pad that is a little bigger than the original ones, could possibly provide slightly better cooling on smaller dies, especially in the case of poorly designed systems that makes it harder to achieve decent temperatures.

but to not forget, the 1.2mm shim may not work on let's say a system that originally used a 1mm thermal pad ( and i don't have a measure to check the thickness in millimetres ). i was wondering, with the thermal pads squishing, how much thinner does this make it? like if i were to buy a 1.5mm thermal pad, how much thinner can it get when bolted down by heatsink? because if i can get a more rough set measurement estimate, it may be possible to get a more "universal" copper shim with use of thermal paste, instead of thermal padding ( which i'd assume would be better than just using thermal pads ). so if originally the thermal pads were 1.5mm, and i buy the 1mm copper shims, then they should be fine, or would 1.2mm be a better "universal" size? 

[dencorso]

Artic Silver rings any bells?

[cov3rt]

3 hours ago, dencorso said:

Artic Silver rings any bells?

if i forget to mention, clearance issues makes thermal paste alone is not a option, as there would be a gap and would cause overheating. that's why i was asking what would be the better of the two, the copper shims + high quality thermal paste or thermal pad, and specifically factoring in for universal usage, thickness, etc. 

[dencorso]

Aluminum foil, tin foil or lead foil + artic silver. Problem is with the paranoia people has about lead, it'd be difficult to get but I think it's the best option for a shim. It has been used for gaskets for a long time, before the paranoia set in.

[jaclaz]

I am clearly missing something, but a (larger) copper shim can be cut to measure, can't it?

About thickness of the thermal pad, I believe we are talking between 5% and 20% , that is, starting from 1.5 mm the final, tightened, thickness will be anything between 1.2 and 1.4 mm, but I am perplexed by your expected precision, it is not a (Swiss) mechanical watch, 0.2 mm (two tenths of a millimeter) difference in thickness is unnoticeable/irrelevant, and it also depend on how tightly you screw the heatsink down.

@dencorso

Sure, sometimes I wonder how we managed to survive[1] at all, with all the lead and asbesto we must have been in contact with in our youth (nevermind no car seat belts, no helmets, no safety breakers on mains, no "use by date" on food, free roaming on the roads as kids, etc.).

 

jaclaz

[1] there must be a reason why it is called "survivor bias"

 

[cov3rt]

assuming the original thermal pad in the previous laptop i worked with was 1.5mm, using that reference and jaclaz's points, and factoring in thermal paste in between the chips and heatsink, it would roughly put it around 1.3mm or so which is within the specifications that jaclaz also mentioned, which likely would allow adequate functioning. the reason why i went with the copper shims vs thermal pads was because i couldn't find a good deal for any of thermal pads and / or felt that the padding in general would be less durable or more inferior than the shims. i got (20) 15mm x 15mm x 1.2mm copper shims from amazon for $8.54 shipped, though from amazon free prime trial offered the free 2-3 day shipping or else it would have been almost $13 with very slow shipping. the trial is only 1 week so i need to make sure to cancel it before that time ends. 

[Molly Dawn]

artic silver or artic silver + copper shim definately. thermal pads have been obsolete since the first pentium-mmx hit 233mhz. OEM's just use them cause they're cheap.