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Opinions on Thermal Adhesive
Im working on passively cooling a VIA C3 I've got laying around and I'm
considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. -Dylan C |
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Opinions on Thermal Adhesive
On Wed, 11 Oct 2006 09:55:37 -0500, Dylan C wrote:
Im working on passively cooling a VIA C3 I've got laying around and I'm considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. Neven tried expoxy for a HS, but I've worked with it a lot building my on golf clubs. The problem you may have with epoxy is that when it heats up the bond is brokem. IOW's I use a heat gun blowing on the glubhead hossle and the club shaft to remove remove the clubhead. I think most modren cpu's would reach the temps required to break the bond. It's possible that the epoxy supplied with the cooler might work, but I'd watch it closely. I have heard of using superglue on the corners to hold a HS in place and from what I recall it works well. Just don't get too much on each corner if you ever want to break the bond. -- Want the ultimate in free OTA SD/HDTV Recorder? http://mythtv.org http://mysettopbox.tv/knoppmyth.html Usenet alt.video.ptv.mythtv My server http://wesnewell.no-ip.com/cpu.php HD Tivo S3 compared http://wesnewell.no-ip.com/mythtivo.htm |
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Opinions on Thermal Adhesive
In article , Dylan C
wrote: Im working on passively cooling a VIA C3 I've got laying around and I'm considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. -Dylan C Do you see two holes next to the processor, like the C3 in this picture ? The C3 in the upper right, has a hole on the left and the right, and maybe those line up with a Northbridge type cooler ? http://www.xbitlabs.com/images/edito...ill-via-c3.jpg Some coolers have adjustable arms, and they can adapt to a small range of relationships between the holes and the chip to be cooled. http://www.zalman.co.kr/eng/product/...dx=71&code=014 This is another example of a Northbridge cooler, only this has a fan on it. This one has an exceptionally good theta_R (thermal resistance) of 1.26C/W. Which is good enough to cool a Tualatin, let alone a Northbridge. The mounting scheme on this one (AMD version) can handle center to center on the holes, of 52.1mm to 61.4mm. http://www.swiftnets.com/products/mcx159.asp The risk with thermal epoxy, is you only get one chance to get it right. People who have tried to remove a heatsink that used thermal epoxy, basically ripped the chip underneath to shreds when trying. And some people managed to fit the heatsink crooked (not parallel to the surface of the chip), and regret the mess they made. It might help to practice gluing two representative objects together first with the epoxy, so you can get a feel for how tough it is to get right. Paul |
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Opinions on Thermal Adhesive
Paul wrote:
In article , Dylan C wrote: Im working on passively cooling a VIA C3 I've got laying around and I'm considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. -Dylan C Do you see two holes next to the processor, like the C3 in this picture ? The C3 in the upper right, has a hole on the left and the right, and maybe those line up with a Northbridge type cooler ? http://www.xbitlabs.com/images/edito...ill-via-c3.jpg I have these holes, but the oversized heatsink covers them both up. Some coolers have adjustable arms, and they can adapt to a small range of relationships between the holes and the chip to be cooled. http://www.zalman.co.kr/eng/product/...dx=71&code=014 This is very similar to the heatsink I installed on my Abit AN7. The problem is that If i want to passively cool it, I need to use a heatsink substantially larger than one designed to cool a NB. The one I have in mind is ~60mm x 60mm CPU heatsink with the fan removed. See a similar 80mm model he http://images10.newegg.com/NeweggIma...103-166-01.jpg It would not be impossible to modify it to use the existing holes, but I'd rather just glue it on if I can. This is another example of a Northbridge cooler, only this has a fan on it. This one has an exceptionally good theta_R (thermal resistance) of 1.26C/W. Which is good enough to cool a Tualatin, let alone a Northbridge. The mounting scheme on this one (AMD version) can handle center to center on the holes, of 52.1mm to 61.4mm. http://www.swiftnets.com/products/mcx159.asp The risk with thermal epoxy, is you only get one chance to get it right. People who have tried to remove a heatsink that used thermal epoxy, basically ripped the chip underneath to shreds when trying. And some people managed to fit the heatsink crooked (not parallel to the surface of the chip), and regret the mess they made. It might help to practice gluing two representative objects together first with the epoxy, so you can get a feel for how tough it is to get right. Paul What I'm worried about is how well the epoxy (designed for a NB) would perform on a CPU. I'd hate to fry the thing. And if the temps did get too hot...I'd like to be able to replace it. -Dylan C |
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Opinions on Thermal Adhesive
Wes Newell wrote:
On Wed, 11 Oct 2006 09:55:37 -0500, Dylan C wrote: Im working on passively cooling a VIA C3 I've got laying around and I'm considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. Neven tried expoxy for a HS, but I've worked with it a lot building my on golf clubs. The problem you may have with epoxy is that when it heats up the bond is brokem. IOW's I use a heat gun blowing on the glubhead hossle and the club shaft to remove remove the clubhead. I think most modren cpu's would reach the temps required to break the bond. It's possible that the epoxy supplied with the cooler might work, but I'd watch it closely. I have heard of using superglue on the corners to hold a HS in place and from what I recall it works well. Just don't get too much on each corner if you ever want to break the bond. Thats a decent idea. I suppose I could try using two-sided tape as well. Thats what held the original heatsink on. Maybe I could put a small drop of silicon adhesive on opposite corners, and a thin coat of grease over the rest. Or just omit the grease and use all silicon. I'm willing to take a few risks with the thing. I bought the board/CPU over 3 years ago for $5 at tigerdirect. Since then its just sat in my closet, so If i wreck it I'm not out much. -Dylan C |
#6
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Opinions on Thermal Adhesive
In article , Dylan C
wrote: Paul wrote: In article , Dylan C wrote: Im working on passively cooling a VIA C3 I've got laying around and I'm considering using a two part epoxy-like thermal adhesive to attach an oversized heatsink to the CPU. The CPU is integrated, so there is no socket to clip the heatsink to, similar to a NB chip. The only other alternative is to drastically mod the heatsink so I can mount it to the board. I'm 90% certain that the oversize passive heatsink will work, but I'd like to know how well the adhesive will perform before I permanently attach it. Anyone have experience with this stuff? The adhesive I have was provided with a Zalman NB heatsink, if it matters. -Dylan C Do you see two holes next to the processor, like the C3 in this picture ? The C3 in the upper right, has a hole on the left and the right, and maybe those line up with a Northbridge type cooler ? http://www.xbitlabs.com/images/edito...ill-via-c3.jpg I have these holes, but the oversized heatsink covers them both up. Some coolers have adjustable arms, and they can adapt to a small range of relationships between the holes and the chip to be cooled. http://www.zalman.co.kr/eng/product/...dx=71&code=014 This is very similar to the heatsink I installed on my Abit AN7. The problem is that If i want to passively cool it, I need to use a heatsink substantially larger than one designed to cool a NB. The one I have in mind is ~60mm x 60mm CPU heatsink with the fan removed. See a similar 80mm model he http://images10.newegg.com/NeweggIma...103-166-01.jpg It would not be impossible to modify it to use the existing holes, but I'd rather just glue it on if I can. This is another example of a Northbridge cooler, only this has a fan on it. This one has an exceptionally good theta_R (thermal resistance) of 1.26C/W. Which is good enough to cool a Tualatin, let alone a Northbridge. The mounting scheme on this one (AMD version) can handle center to center on the holes, of 52.1mm to 61.4mm. http://www.swiftnets.com/products/mcx159.asp The risk with thermal epoxy, is you only get one chance to get it right. People who have tried to remove a heatsink that used thermal epoxy, basically ripped the chip underneath to shreds when trying. And some people managed to fit the heatsink crooked (not parallel to the surface of the chip), and regret the mess they made. It might help to practice gluing two representative objects together first with the epoxy, so you can get a feel for how tough it is to get right. Paul What I'm worried about is how well the epoxy (designed for a NB) would perform on a CPU. I'd hate to fry the thing. And if the temps did get too hot...I'd like to be able to replace it. -Dylan C The C3 at the bottom of this page, is listed as 10W max. I don't know which C3 you might have, but it might be 10W or less. The Intel 865/875 generation Northbridges were 10-12W, so in fact that Northbridge is in the same ballpark. And some of the Nvidia chipsets like Nforce4 are likely higher again in power (which is why they all tend to ship with fans on them). http://www.cpu-world.com/CPUs/C3/index.html This is a table of data I've used a few times. Aavid has some heatsinks for BGA packages, and these are some samples: Length Width Height still with mm mm mm air fan 200LFM 35x35 374624B60024 35.00 35.00 10.00 23.40 7.55 Black anodize 35x35 374724B60024 35.00 35.00 18.00 15.30 5.15 Black anodize 35x35 374824B60024 35.00 35.00 25.00 12.00 4.27 Black anodize The Zalman NB47J is taller than these heatsinks. As the fins get longer, the added length contributes less to performance, so there should be an asymtotic limit as the heatsink becomes higher. You can plot the thermal resistance number (like the 23.40 number, in units of degrees C per watt) in Excel, and extrapolate how much height it would take to get good still air performance. The Zalman NB47J is getting close to the right value, but it would be really nice if Zalman would actually quote a number themselves, instead of me trying to guess at it this way. The NB47J only has taller central fins, which means the fin length is not uniform across the whole 35x35 surface. If we aimed for a 70C processor temperature, and ambient was 25C, then we'd have 45C to play with. At 10W power, the thermal resistance could not be higher than 4.5C/W. Then 25C + 4.5C/W * 10W would give the 70C chip case temp. Plotting those values, in a 35mm x 35mm heatsink, and extrapolating, doesn't leave much room for error. So you are probably right to stick with your larger heatsink. If you want to get some idea of the heatsink performance, have a look at the Aavid web site. There is a section on extrusions, and looking in there can give you some ideas on how effective your passive heatsink will be. http://www.aavidthermalloy.com/products/heatsinks.shtml And to fit your heatsink, all you need to do, is measure the diagonal from hole to hole on your motherboard. Then take a ruler, and eyeball with respect to the fins, whether two holes can be placed between fins, such that the holes have the same diagonal spacing. Purchase a couple of nylon screws and nuts, as there is less chance of shorting something by using Nylon. If the heatsink is big enough, the heatsink temp should not be high enough to bother the nylon. Once the first hole is drilled in the sink, you can transfer a centerline from the trough between fins on one side of the sink, over onto the flat side, allowing you to draw a diagonal line from the first hole, to a point intersecting the centerline you transferred. Drilling the second hole should be reasonably accurate then. And if you get it wrong, there is plenty of heatsink material to try again :-) A couple of other notes on heatsinks. One performance issue is called spreading angle. Basically, the base of the heatsink has to be thick enough, to effective transfer heat from a hot central spot, to the outer fins. Some heatsinks may look impressively large, but if enough material was not used for the base, the outer fins are not really that effective. The other issue is mass. Years ago, for an application like this, I was told not to adhere a heatsink larger than 50 grams to the top of a 35x35 chip. If your heatsink really is as large as you describe, securing it with screws might prevent a sudden shock from decapitating the chip. Epoxying a heavy heatsink, might mean damage if the board receives a shock from being dropped a short distance. Paul |
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Opinions on Thermal Adhesive
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