How thick is the gap between GPU & heatsink?

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Badger · #1 Post by **Badger** » Sat Dec 19, 2009 4:31 pm

Does anyone know exactly how thick the gap is between the heatsink and the GPU on the T60? I removed the thermal pads that fill the gap and replaced them with thermal paste, but it didn't do much for temperatures so I'd like to place a copper or aluminum shim in there instead. I've read on here anywhere from 1.5mm (0.06 inches) to ~3mm (0.125 inches) is the distance. Wondering what the best thickness for the shim would be.

Thanks!

#2 Post by **richk** » Sat Dec 19, 2009 5:50 pm

If I need to replace thermal pads, I use 2mm. I suggest that the pads are better because they don't need to be as precise.

crazyfrog · #3 Post by **crazyfrog** » Sun Dec 20, 2009 3:14 am

Badger wrote:... I've read on here anywhere from 1.5mm (0.06 inches) to ~3mm (0.125 inches) is the distance. ...

It is not that thick. I've opend up several T60/p. My estimation is between 0.5mm to 1.0mm judged from where the GPU core is.

JesseKnows · #4 Post by **JesseKnows** » Wed Dec 23, 2009 10:33 pm

Be careful! There's a reason why a thermal pad was used rather than the HS shaped to touch the GPU.

The logic is that the CPU is more crucial to cool. If a shim (or shape) was used, small mechanical tolerances could cause the GPU to push the HS such that it doesn't touch the CPU with the necessary tightness.

So, be careful that the shim would not stress the HS away from the CPU.

misfit · #5 Post by **misfit** » Fri Jan 01, 2010 9:14 pm

JesseKnows wrote:Be careful! There's a reason why a thermal pad was used rather than the HS shaped to touch the GPU.

The logic is that the CPU is more crucial to cool. If a shim (or shape) was used, small mechanical tolerances could cause the GPU to push the HS such that it doesn't touch the CPU with the necessary tightness.

So, be careful that the shim would not stress the HS away from the CPU.

I hardly think that likely as they're only connected with a quite flexible heatpipe and the CPU part is held down with several spring-loaded screws. Also the CPU has thermal overload protection so, even if the above scenario were to happened the CPU would just throttle itself. Heck, if the HS were removed completely the CPU would survive but the GPU wouldn't.

IMO the reason that the HS wasn't shaped to fit the GPU better is because it's an extra step on the production line and makes assembly more complex. HS pads are, thermally speaking, rubbish and only used to compensate for design flaws. Considering that the GPU in a T60/p gets far hotter than the CPU, is more centrally located in the laptop and doesn't have thermal throttling / protection a slight user modification to the HS assembly to better cool it is a must. IMO.

I've bent the heatpipe (be very careful, they're under vacuum so *really* want to collapse on themselves) on my HS so that it's in contact with the GPU and NB tops, used AS5 and shimmed (coins of different thickness) the retention clip. It works fine. GPU runs significantly cooler and so the fan doesn't run as often. The CPU doesn't run any hotter.

#6 Post by **richk** » Sat Jan 02, 2010 8:19 pm

I believe the flexible heatpipe would guarantee a bad connection to the GPU if the level isn't EXACTLY right. You really should not use a hard shim

thinkpac · #7 Post by **thinkpac** » Sun Apr 24, 2011 10:45 pm

richk wrote:If I need to replace thermal pads, I use 2mm. I suggest that the pads are better because they don't need to be as precise.

What if you only have 1mm thermal pads? Is it OK to just put 2 of them on top of each other, to effectively form a 2mm thermal pad?

ThinkPadophile · #8 Post by **ThinkPadophile** » Mon Apr 25, 2011 9:15 am

Before I had actually tried it, I had the same misgivings that some are voicing. I even wrote a lengthy post some time ago warning about these concerns.

When I tried it I found that my concerns were baseless. I've now modded serveral and have never had a problem. Yes, one has to be careful when bending the heat tube, but I find that it is generally unnecessary to do so, and if any bending is required it is quite slight. Also, there has been no problem with CPU overheating. In every case this simple mod lowered GPU temperatures by 35-40 degrees F.

Regarding the thickness, 1.5 mm seems best, but the heat tube and spring clip will normally conform itself to take up the slack. One person on this forum even modded his T60p by simply removing the thermal conductive pad and then bending the heat tube to make direct contact with the GPU. That's a bit too risky for me, but it worked for him. My point is, the tolerances are not so critical as I once feared.

thinkpac · #9 Post by **thinkpac** » Mon Apr 25, 2011 10:17 am

ThinkPadophile - just to be sure I'm clear on what you're talking about - you're talking about using a 1.5mm copper shim between the GPU and heatsink? What about the Northbridge chip?

ThinkPadophile · #10 Post by **ThinkPadophile** » Mon Apr 25, 2011 6:54 pm

Yes on the copper shim. Regarding the Northbridge chip, just re-use the thermal conductive pad. There does not seem to be a heat problem with the Northbridge chips.

Bibin · #11 Post by **Bibin** » Mon Apr 25, 2011 11:12 pm

Just yesterday I removed the pad, bent down the pipe a little, and took a square of copper off of a spare T60p heatsink I had lying about since I had replaced it - the square is welded to the part where the GPU thermal pad was; using pliers, by bending the larger piece it was attached to I got it to pop off. I put thermal paste between this new copper shim and the installed heatsink, then some thermal paste on the GPU. I then made sure that the silver retention bracket was pushing down with enough force on the GPU to keep it all in place.

Previously, the GPU idled around 71 Celcius and shot up to 110 Celcius after 40 seconds of a game of Team Fortress 2 (though it didn't shut down)

Now, the GPU idles around 65 Celcius and won't shoot past the high eighties after ten minutes of playing the same game. This is a definite improvement.

When bending the heat pipe be sure to gently bend it, and not crimp it. If you crimp it the flow will be internally inhibited. It is worth noting that once you overcome the static coefficient of tension while bending it the resistance to bending is suddenly reduced, so it will feel like you have crimped it even if you haven't.

thinkpac · #12 Post by **thinkpac** » Tue Apr 26, 2011 2:30 pm

Thanks for the reply. I initially dismissed the idea of using a shim, since I thought the thickness would need to be exact. I thought if it was too thick, then trying to put the heatsink on might result in the GPU being (slightly) crushed. I also thought if it was too thin, then there might still be too much space between the heatsink/shim/GPU, and also the shim could slip out if the ThinkPad suffered a fall or other sudden strong movement.

I'm not comfortable with this idea of bending the heatsink, and hopefully it won't be necessary. It just seems like the heatsink as it is now will allow the surface to rest completely flat/parallel against the CPU/GPU, but if you were to bend it, then the surface may be at a slight angle and will no longer rest flat/parallel against the CPU/GPU.

Bibin · #13 Post by **Bibin** » Tue Apr 26, 2011 4:36 pm

thinkpac wrote:Thanks for the reply. I initially dismissed the idea of using a shim, since I thought the thickness would need to be exact. I thought if it was too thick, then trying to put the heatsink on might result in the GPU being (slightly) crushed. I also thought if it was too thin, then there might still be too much space between the heatsink/shim/GPU, and also the shim could slip out if the ThinkPad suffered a fall or other sudden strong movement.

I'm not comfortable with this idea of bending the heatsink, and hopefully it won't be necessary. It just seems like the heatsink as it is now will allow the surface to rest completely flat/parallel against the CPU/GPU, but if you were to bend it, then the surface may be at a slight angle and will no longer rest flat/parallel against the CPU/GPU.

If you do find a thick shim, then use it by all means. Bending the heat pipe is not an ideal solution.

If you find out the correct thickness please do share it, as I'd like to re-do this without bending it.

thinkpac · #14 Post by **thinkpac** » Tue Apr 26, 2011 4:49 pm

ThinkPadophile said the thickness doesn't matter much, since there are springs in the heatsink. I've never removed the heatsink, so I'm not familiar with how it all works. If the springs do compensate for various widths, then the thickness shouldn't matter. Then again, the fact that we need to use a shim means that the springs cannot compensate for zero thickness, and that there is a minimum thickness required.

I also don't know how I would be able to tell if the shim is the correct thickness, as once you put the shim down and then the heatsink over it, it's not like you can actually see whether everything is lying perfectly flat or not. Makes me wonder about the thermal grease too - you're supposed to only use a tiny dot, but what if it's not enough to cover the entire GPU surface? You won't be able to tell if that's the case.

Bibin · #15 Post by **Bibin** » Tue Apr 26, 2011 5:33 pm

The CPU heatsink is spring mounted, but the GPU heatsink, without bending the heat pipe, relies on a certain distance between the core and the copper plate.

thinkpac · #16 Post by **thinkpac** » Fri Apr 29, 2011 7:55 am

OK I was able to get an ebay seller to sell me 5 different thicknesses of shims: 0.5mm, 0.55mm, 1.0mm, 1.2mm, and 1.5mm. Will take a few days for them to arrive.

Looking at photos of the T60 internals, it seems there will be memory chips right next to the GPU core. These copper shims I ordered are 2cm x 2cm, and so the copper shim will probably touch both the GPU core and adjacent memory chips - I assume there's no problem with that? Or is the GPU core taller than the memory chips, so the shim wouldn't touch them anyway?

Also, I still am not sure how I will know what the exact thickness required is, since once I put the heatsink down, it's not like I'll be able to tell with my eyes. Should I just go from thinnest shim to thickest shim (without using thermal paste - just to test out the sizes), and shake the laptop and if the shim falls out, I know it's too small, and if it doesn't fall out then that must be the right size (or close enough)?

thinkpac · #17 Post by **thinkpac** » Mon May 02, 2011 6:59 pm

Bibin wrote:If you do find a thick shim, then use it by all means. Bending the heat pipe is not an ideal solution.

If you find out the correct thickness please do share it, as I'd like to re-do this without bending it.

I just received the 5 different sized shims. They don't appear to be 100% flat, as they have some slight curvature, so I'm not sure how effective they will be.

Also, the thicker ones seem to be relatively heavy, which gives me concern that they could actually slip out if the ThinkPad is on its side (like if you are carrying it in a laptop bag). Maybe I'll have to look into bending the heatsink after all...

ThinkPadophile · #18 Post by **ThinkPadophile** » Mon May 02, 2011 9:00 pm

Try making your own. You can buy a copper sheet at a hardware store for around $10, or a bronze sheet even cheaper. Copper is the better heat conductor by a factor of about 2, but bronze is cheaper and it has worked fine for me. Get one anywhere between 1-2mm thick. The thickness isn't critical since the spring clip will adjust to its actual height. Use a hacksaw to saw off a small piece, and file the edges to remove the burrs. Then, coat it with Arctic Silver on both sides and install it in place of the thermal pad. The pressure from the spring, and the stickiness of the Arctic Silver, are more than enough to hold it securely in place.

thinkpac · #19 Post by **thinkpac** » Wed Jun 01, 2011 12:55 am

Got around to replacing the fan this weekend. The thermal pad between the GPU and heatsink is 1.0mm, with an indentation of about 0.4-0.5mm caused by the GPU, meaning the actual gap between the GPU and heatsink is 0.5-0.6mm. So I used a 0.5mm copper shim. I also used MX-2 thermal paste, which is one of the new generation of thermal pastes people are recommending on the overclocking boards instead of Arctic Silver 5. (It is not capacitive and does not require a break-in period, unlike AS5, and also lasts 8 years.) I did not replace the heatsink (just the fan), nor did I bend it at all.

Seems to have been successful, as my CPU now idles at 52 (celcius) and the GPU idles at 69. I'd never seen the CPU under 60 or the GPU under 80 before. Before the putting in the shim, I ran a 3DMark graphics benchmark, and the CPU got up to 87 and the GPU got up to 100. After installing the shim, the CPU only got up to 67 and the GPU only got up to 79 after the same 3DMark benchmark. Before installing the shim, I also ran the Prime95 torture test, and the CPU got up to 94 and the GPU got up to 97 (didn't know that Prime95 would exercise the graphics processing unit?). Then after installing the shim, the CPU only got up to 76 and the GPU only got up to 79 after the same Prime95 test.

Looks like the type of thermal paste you use will also have a significant impact on the CPU. I'd read people saying that when they switched thermal pastes, they only gained a few degrees of benefit. So the stock thermal paste on the heatsink must be extremely low quality.

The only thing I don't know about is how tight the shim is being pressed against the GPU. Hope it doesn't fall out!

Thanks for the replies, everyone.

#20 Post by **Johan** » Wed Jun 01, 2011 5:50 am

thinkpac wrote:... meaning the actual gap between the GPU and heatsink is 0.5-0.6 mm. So I used a 0.5 mm copper shim.

... my CPU now idles at 52 (celcius) and the GPU idles at 69. I'd never seen the CPU under 60 or the GPU under 80 before.

Thanks very much for sharing this highly interesting information! One question however: What model T60/p do you have? (what CPU, what GPU and what fan assembly?)

Compared to the idle temperatures of a T60 of mine (this my T60 being a 2007-5BU with an ATI X1300 GPU and a Core Duo T2400) your idle temperatures sound very, very high. Does your fan run when you record these idle temperaturs, or have you perhaps disabled the fan during this "idle temperature recording"?

PS: Maybe there is a potential business case for selling such pre-cut 0.5 mm copper shims specificly intended for T60/p fans here on our own Marketplace?? Someone wants to make some nice extra $$$?

Thanks!

Johan

thinkpac · #21 Post by **thinkpac** » Wed Jun 01, 2011 8:03 am

Johan wrote:Thanks very much for sharing this highly interesting information! One question however: What model T60/p do you have? (what CPU, what GPU and what fan assembly?)

I have a 2007-CTO with T2500 2.0 GHz CPU, X1400 128 MB GPU, and 41V9932 heatsink/fan.

Compared to the idle temperatures of a T60 of mine (this my T60 being a 2007-5BU with an ATI X1300 GPU and a Core Duo T2400) your idle temperatures sound very, very high. Does your fan run when you record these idle temperaturs, or have you perhaps disabled the fan during this "idle temperature recording"?

Yes the fan does run when it is idle (somewhere around 3500 RPM).

#22 Post by **Johan** » Mon Jun 06, 2011 4:10 pm

thinkpac wrote:I have a 2007-CTO with T2500 2.0 GHz CPU, X1400 128 MB GPU, and 41V9932 heatsink/fan.

Yes the fan does run when it is idle (somewhere around 3500 RPM).

Thanks for this information. Final question which just came to mind: Does your CPU run in "balanced" or "adaptive" mode (and hence automatically throttling down the clock down to the lowest possible, when in idle mode), or have you perhaps set the CPU to run at "Maximum speed"? The reason for asking is that your idle temperatures ("CPU now idles at 52 [Celcius] and the GPU idles at 69") seems quite high to me... (also: Do you have PowerPlay enabled while running on mains? If not, your GPU speed may perhaps be "too high" to allow a lower temperature?).

A hint perhaps of interest for someone: I just discovered this eBay advertisement: IBM T60 T60p T61 Heatsink GPU Thermal Pad Copper Shim while searching on eBay for "heatsink thermal pad copper shim". There are quite a few of these to get (in various dimensions), making this modification fairly easy to get along with!

Johan

goofyGAguy · #23 Post by **goofyGAguy** » Mon Jun 06, 2011 5:53 pm

Johan wrote:
A hint perhaps of interest for someone: I just discovered this eBay advertisement: IBM T60 T60p T61 Heatsink GPU Thermal Pad Copper Shim while searching on eBay for "heatsink thermal pad copper shim". There are quite a few of these to get (in various dimensions), making this modification fairly easy to get along with!

Thanks for the link.

thinkpac · #24 Post by **thinkpac** » Mon Jun 06, 2011 11:43 pm

Johan wrote:Final question which just came to mind: Does your CPU run in "balanced" or "adaptive" mode (and hence automatically throttling down the clock down to the lowest possible, when in idle mode), or have you perhaps set the CPU to run at "Maximum speed"?

I have it set to maximum.

(also: Do you have PowerPlay enabled while running on mains? If not, your GPU speed may perhaps be "too high" to allow a lower temperature?).

I don't know what PowerPlay is.

LegendaryKA8 · #25 Post by **LegendaryKA8** » Tue Jun 14, 2011 10:01 pm

Sorry in advance for the slight bump.

I remember doing pretty much the same with my old T60p a while ago. I was receiving scorching temps whilst gaming(I think they were high-90s to low-100C) and I wasn't comfortable with that at all. I dug up an old thread I posted a while back and came up with some good info about modding the heatsinks and different FRUs. I assume that it might give some decent info to those wanting to do the same to their T60/p's:

http://forums.thinkpads.com/viewtopic.php?f=29&t=79473

IIRC I used a shim already on a T4x 'long fan' I had laying around for the copper shim. Arctic Silver had a thermal adhesive that I used to 'glue' it onto the T60p heatsink I had... my main issue was getting the proper fan/heatsink for the V5250/T7200 combo I was running(I had put a T60p motherboard into my existing T60 chassis which had been modified with a T7200 and a UXGA Flexview before I purchased it). For as long as I had it it worked very well.

misfit · #26 Post by **misfit** » Sat Sep 14, 2013 11:04 pm

LegendaryKA8 wrote:Sorry in advance for the slight bump.

Heh! Also from me.

However I'm moving parts including motherboards between four T60s at the moment so am modding the coolers as I go - Hence reading this thread.

LegendaryKA8 wrote:I remember doing pretty much the same with my old T60p a while ago. I was receiving scorching temps whilst gaming(I think they were high-90s to low-100C) and I wasn't comfortable with that at all. I dug up an old thread I posted a while back and came up with some good info about modding the heatsinks and different FRUs. I assume that it might give some decent info to those wanting to do the same to their T60/p's:

http://forums.thinkpads.com/viewtopic.php?f=29&t=79473

That URL is wrong - The correct one is:

http://forum.thinkpads.com/viewtopic.php?f=29&t=79473

How thick is the gap between GPU & heatsink?

How thick is the gap between GPU & heatsink?

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