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Thermal pad or compound?

by barry_e_m / February 13, 2005 9:14 PM PST

The AMD website has a tutorial (http://www.amd.com/us-en/assets/content_type/DownloadableAssets/section5-high.wmv) that states the following:
"Use a thermal pad for long-term production installations..."
"...Thermal grease is only recommended for development, test and validation purposes. In a production evironment, thermal grease may disperse over time, leaving no interface material between the heatsink and processor. Only use thermal grease when the heatsink needs to be replaced multiple times over a short period."

I intend to attach a heatsink permanently to a CPU, so heeding the above advice I visited a couple of computer stores asking for a thermal pad. Unfortunately, all they had was thermal paste in syringe-type dispensors. In fact they did not appear to have heard of thermal pads.

There are still one or two few computer supplies stores in my city that I did not have time to check, but if it turns out that they too do not sell thermal pads, then am I best advised to adhere strictly to AMD's dictum and place an order for one, or is the grease really just as effective?

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I doubt very much that the Thermaltake
by Ray Harinec / February 13, 2005 9:35 PM PST

was put on with a thermal pad [also known as a phase change pad], basically the heat from the CPU changes its state from a solid to a paste. Just checked, http://www.cyberguys.com has the tape as item 148 0012.

I would worry not, though. I have bought Retail box AMD CPU's [they include the HSF], some had the pad, some had the paste. The ones with paste appeared to be a pad until I touched the stuff, and found it was paste, it is put on so perfectly in a square.

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It had a white paste,
by barry_e_m / February 13, 2005 11:04 PM PST

which might have started out as a pad, I suppose (I cleaned it all off). In any case I bought it used, so the heatsink may well have been attached by a previous owner for all I know.

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Try this...
by Willy / February 14, 2005 4:10 AM PST
In reply to: It had a white paste,

I wouldn'y worry too much about finding the "thermal pad" if you find another source, great but the HS compound no matter what names found on tube, works just as well. The big stink is many a user place too much or those that contain metaltic based sustances can find thier way into circuit paths, if too much used or improperly placed. A litte dab goes a long way and overall that's more than capable for thermal pad replacement. One reason thermal pads are widely used for OEM installs or as part of the install kit, it's "already measured" for application, thus reduce user boo-boos.

enjoy Happy -----Willy

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If I were using the grease,
by barry_e_m / February 14, 2005 2:13 PM PST
In reply to: Try this...

then I certainly would ensure that I did not apply an excessive amount.
Perhaps I am worrying unnecessarily, when when I see a warning such as, "thermal grease may disperse over time, leaving no interface material between the heatsink and processor", then I am concerned. I would not want to risk such a condition occurring.

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Ok, try this...
by Willy / February 15, 2005 6:02 AM PST

I've used such thermal grease on other uses besides for cpu. They work for "years". What may happen is a tendency to dry out and then only if the item being thermally protected is sustain beyond the norm and/or extreme usage. Typical pc users shouldn't ever get into extreme situations if used as supported, NO overclocking, etc. and even then that won't be that harmful to the grease but maybe to the cpu. Sad Overall, it isn't a real concern, just apply a normal amount. Here's a link for such insight:

enjoy -----Willy Happy

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follow these instructions and you can't go wrong
by maximus7001 / February 19, 2005 10:47 AM PST

Being an operator of a computer mod shop, I have extensively experimented with this subject. The temperature difference between a stock pad and proper application of a quality thermal interface material(t.i.m) can and will be greater than anyone could guess. Were talking about between 2c and 10c drop in temperature, usually around the 5c mark when directly compared with the junk that comes on a heatsink. Needless to say, I would never let a computer leave my shop without a proper application of atctic silver ceramique(non conductive) on all things that need it like the cpu, gfx card, and northbridge heatsinks. http://www.arcticsilver.com/arctic_silver_instructions.htm

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I Totally Agree!
by Robert K / February 21, 2005 9:42 PM PST
In reply to: Try this...

Thermal paste works equally as well as the pads. In fact, for the person not familiar with replacing the heat sink to a processor would be much more likely to cause a problem with the pad than using paste. If the pad contacts anything other than the exact spot on the processor where it belongs, the thermal conductivity will have a void where it is supposed to contact the processor when it is finally clamped. Also, none of the fancy thermal paste works any better than the plain old white heat sink compound.

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Re: Thermal pads
by JamesJ / February 14, 2005 6:43 PM PST

If you have a CompUSA nearby, have you tried there? I picked up a pack of thermal pads at a local CompUSA a while back. They were in the same area as other computer parts like cases, power supplies, case screws, fan grills, etc.


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No CompUSA here
by barry_e_m / February 15, 2005 10:11 AM PST
In reply to: Re: Thermal pads

Thanks for the tip James, but I am in Wellington, New Zealand. We only have a handful of computer supplies store here. I've checked them all now, and they only have thermal paste.

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No, I guess not
by JamesJ / February 15, 2005 6:00 PM PST
In reply to: No CompUSA here

I suppose they would be a bit out of the way from there. Happy

I guess you have to decide between getting the paste locally or ordering pads from somewhere and waiting for them to arrive. Personally, I'm afraid that if I used the paste I'd get the amount wrong. My impression is that it's a fairly precise thing. As it happens, I've got a replacement CPU that I'm going to put in my system when I get around to it. My old heatsink and fan should be more than adequate for the new CPU, but I'm thinking that I'll just get new ones and look for something with a thermal pad, so I don't have to deal with the paste.

Good luck with whatever you decide to do.


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I provided a link to buy it
by Ray Harinec / February 16, 2005 3:15 AM PST
In reply to: No CompUSA here

in US via internet. However I assure you that the tape is in no way worth that much over thermal compound. I really think that they recco the tape because it is a controlled thickness. If one puts too much compound on it becomes a heat transfer impediment.

The compound is only intended to fill microscopic departure of flatness of the mating surfaces.

Use the compound!!!!!!!!!!!!!

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Perspective of an old codger
by wes_bullis / February 17, 2005 9:24 PM PST

I've been using thermal heat sink compound ever since I started building solid state power supplies using switching transisters back in the 1980's. I have built some stuff which I designed poorly and got pretty hot, and I've never had heat sink compound disperse to the point that it was no longer effective, even in stuff I've torn apart after 15 or 20 years of use.

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Aussie Perspective
by Flirkann / February 17, 2005 10:03 PM PST

I've never seen thermal compound go past its use either. I suspect the AMD article was written by some one with experience with actual thermal 'grease' which was used often in prototypes because it was easier to clean up than the thermal paste and allowed for quick evaluations if the prototype failed for some reason.
If you're going to use paste, a silicon based paste is the safest as it isn't electrically conductive so you can't accidentaly short something out if you apply too much. it is readily available at places like Tandy or **** Smith. I think you should have those in NZ.

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Thermal paste?
by rub / February 19, 2005 2:45 AM PST

I too go way back with big extruded finned heat sinks, vent fans for the cabinets, mica washers, kapton washers, beryllia washers and paste, etc. But we didn't use fans ( with vibration ) on the cases. I never saw migration of the solids, only the silicone, but that was under substantially different conditions. I believe that constant monitoring of temp with thermal shutdown is the only way to go.

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My problem with thermal tape & how to use thermal paste
by xomegax1 / February 17, 2005 11:36 PM PST

My problem with thermal tape is that on occasion, it will act as adhesive and cause the heatsink to stick to the CPU. If this happens and you need to remove the heatsink/CPU for any reason, you run the risk of damaging the CPU. While a metallic-based paste may cause issues if you use too much, it is easily the best way to go. Thermal paste lasts basically forever (i.e., the CPU will die before the paste will). When applying the paste, a good rule of thumb to use is to apply a small dab the size of a grain of rice dead center of the CPU.

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by jim powell / February 17, 2005 11:51 PM PST

when useing thermal grease use just a dab, do not put on a layer thick.
less is more

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paste vrs pads
by ParnaoidGuy / February 17, 2005 11:59 PM PST

There are lots of great posts here, so I will be brief and tell you of my experiences.

Pads are fine. Sometimes they stick.

Grease is my preferance. I have taken a heat sink off of a seven year old PPro processor and still found it to be gummy and nasty.

For those of you have never used an old Pentium Pro system, they ran hot. Really hot! A P Pro with no heat sink on it that was at ambient temperature would typically crack if powered on they heated so fast.

P Pro processors were also responsible for many bonehead server closet fires. Example: from about 1995 to 1998 most CompUSA stores had a kids software station shaped like a rocket ship.
>> Anyone remember that thing?
Inside was a PPro server that housed all the "stuff" and controlled the three or four terminal around it.
It was small, cramped, badly ventilated, on carpet, and fulled with dust and junk. Then one of them eventually caught fire(smoldered actually) and covered one stores 1.3 million dollar inventory with 2 inches of water.

hehe, good times.

It was the King of Prussia store I think.

But in any case, I am going off topic.

The grease from these evil hot processors has stood the test of time for seven and eight years.

It?s cheap and easy to use.

Just don't use more that a small dabber. Rice size I think one poster said and they were exactly right.

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Stick with the thermal compound
by gswonsn / February 18, 2005 12:00 AM PST

I have never seen thermal compound dissipate over time. I also have never found a thermal pad with the conductivity of compounds such as Artic Silver. The polysynthetic silver does a much better job of conducting the heat away from your processor than do the pads. If you ever have a problem with processor or heat sink fan with the compound you can more easily change your set up than with the pads. I do not reccomend simply any thermal compound but one that has a very high concentration of polysynthetic silver such as Artic Silver 5. It is a very good investment in your system.

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Definitely Thermal Paste
by clem3100 / February 18, 2005 12:28 AM PST

I have installed several CPU?s, all AMD Athlon XP models; I always ordered a package of thermal paste with it. In 3 systems built, and several upgrades (CPU/Motherboard), I have never had any issues concerning thermal paste.
As far as how much to use, that takes a little practice but a grain of rice is a very helpful guideline. I have used more than that and had no problems (there was just a blob of the paste around the CPU die but none made it out to any circuits (that would take quite a bit more than a grain of rice).

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Thermal Paste
by edjcox / February 18, 2005 12:50 AM PST

Thermal paste is the preferred method for a simple thermodynamic reason.

Oil ie hydrocarbons in a compund wlll transfer heat readily to the heatsink and allow excess heat to be more rapidly dissapated. A heat pad will rely on physical contact and that contact is dependent upon the surfaces and the method of mating the two surfaces together. Thermal past bridges the gap with a heat conductive material and assures continuous heat transfer throughout it's working life. You might go back and remove the CPU in 3 years time clean and re-apply new compound.

I have several CPU's that are affixed in this manner and have had no thermal issues. Several tips to follow:

Clean the fan entry point and the fan blades annualy using a vacuum and Medical Q-tips ( the type on wooden sticks). Turn off and unplug machine first. Carefully vacuumte interiorof te case to remove dust, hair, etc. Use a Q-Tip to loosen materials and vaccum away. Do not contact memory chips or other board circuitry with vacuum head as the vacuum may posess a huge static charge that could damage your components.

Keep the area around the computer case clean and free of air obstructions. No papers, stickers, etc covering air ports, opening etc.

Place a small fan to provide air circulation on hot days to the computer or run the machine in a AC enviornment.

Keep the area at the base of the machine clean as many of the new cases draw air in at the base and expell itat the top, a natural chimney process.

Good luck.

E J Cox

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Thermal paste vs thermal pads--mind the gap
by John Sawyer / February 2, 2008 9:10 AM PST
In reply to: Thermal Paste

edjcox says:

"A heat pad will rely on physical contact, and that contact is dependent upon the surfaces and the method of mating the two surfaces together. Thermal paste bridges the gap with a heat conductive material and assures continuous heat transfer throughout its working life."

But thermal paste also relies on physical contact. What he's trying to say is that thermal paste fills in scratches on the bottom of the heat sink better than thermal pads, in cases where the heat sink isn't polished. I don't know how crucial that is, since a thermal pad, when it gets squeezed between the chip and the heat sink, when the heat sink is firmly clipped to the chip, probably fills in the scratches well enough. The difference in thermal conductivity, between thermal pads and thermal grease, is probably more dependent on the type of material used in both. From everything I've read, good thermal paste like Arctic Silver has better thermal conductivity than most (all?) thermal pads.

Also, from what I've read, you should apply a layer of thermal paste that's as thin as you can make it, since a thicker layer can actually impede thermal transfer--all it's intended to do, is to fill the microscopic air gap between the chip and its heat sink, including any scratches. Some people recommend a layer that's almost translucent, and you see layers as thin as this on some new heat sinks, but a little thicker is probably OK. I spread it out using a "tool" made from a few layers of Post-It notes, which I can throw away when I'm done with it.

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The post you replied to was from Feb 2005 ..
by VAPCMD / February 2, 2008 10:17 AM PST

doubt he/she will ever see the response.


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Already a given
by John Sawyer / February 23, 2008 5:27 AM PST

That's taken for granted. The point in posting responses to old threads, is to help people who read the threads later, as you did.

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Thermal Pads or Grease? It depends!
by rlafford / February 18, 2005 1:52 AM PST

I'm a product support engineer for a large medical device manufacturer and we have this subject come up from time to time.

Really both methods work and can work well. BUT, and this is a big expensive but for industry, how do you assure the grease is applied in a way that lets it make an optimal thermal path? This is a challenge even with good training and often the result is high repair cost and an unhappy customer. Because of this, we typically go to the phase change pads, which do a very good job of flowing out and transferring heat between the parts.

I agree that none of the phase change materials can equal the silver compounds when the silver compound is applied correctly. As someone said, thicker is not better, it's almost worse than no thermal interface at all. When evenly distributed and as thin as possible, the silver greases do an exceptional job. As with many things, the devil is in the details, so in the manufacturing world, we usually chicken out and go for the sure thing - phase change thermal transfer pads.

Best of luck with your project.


BTW: Our most challenging thermal transfer components aren't microprocessors; they are thermoelectric coolers. We originally used Artic Silver but had uneven performance. We found that by improving the heatsink design, the thermal pads were more than adequate.

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Well the enthusiast market mostly shuns thermal pads...
by Sadler / February 18, 2005 3:02 AM PST

In the enthusiast arena, thermal paste(high performance silver or ceramic based, not the generic thermal compound in a disposable plastic packet) is "the order of the day". The trick is to apply it evenly but not to goop it on, potentially causing an insulating effect and excess to ooze out from the sides, and possibly onto sensative circuits, which is unwanted, especially with silver based compounds(they're conductive), both of which can lead to minor and major component failures/breakdowns. In practice, with patience and a steady hand, I've found that an old ID or credit card, or even a nice stiff business card makes a suitable "spreader" for thermal paste. In general the enthusiast population has the general consensus that when you can you should use some form of high performance thermal paste, and save "Frag Tape" (thermal pads) for applications which don't have a mechanical means of securing the heatsink such as video RAM, motherboard chipsets, and system RAM. I have only used thermal pads for video and system RAM, and in some cases for video RAM I used Thermal Adhesive like Artic Silver Alumina(ceramic based two part epoxy) it's non-conductive but still not recommended to be left on electrical connections or traces. For example my GeForce 4 Ti4200 has Nickel plated copper RAMsinks bonded on it's TSOP(surface mount not BGA RAM) chips for life. And the reason you're unable to find "Frag Tape" locally is that most new Heatsinks for CPUs already have a piece attached and most memory heatsink kits will include either pre-attached or loose pieces of "Frag Tape", yes it can be bought at "select" PC specialty stores, most are typically regional like SE Wisconsins MPC(Milwaukee PC) stores or affiliate/satelite stores of online retailers like TigerDirect.com(has several regional stores check website for closest one) and Outpost.com(Fry's). If you doubt your ability to apply thermal paste, I'm sure the shops that stock it would gladly do it for anywhere from the cost of the product, if you're a regular customer, to the cost of the product plus a minimum labor charge, also they may have rates for specific servicesa and simply charge the flat rate for a CPU install as that includes the cost of needed thermal paste. Sorry so log-wided wanted to be complete in my explainations.

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Thermal pad smad :)
by Dilo / February 18, 2005 6:41 AM PST

Thermal paste is by far the best solution for interfacing a heatsink with a CPU. Anything which sits between the CPU and the heatsink, such as air or impurities, increases the thermal resistance and reduces the amount of heat transferred. Good quality paste can squeeze down to a tiny width where all the pads I have seen after heatsink removal remain quite thick in comparison.

Naturally the pad doesn't require any more knowledge for installation than being able to stick something in the right place but properly applied good quality paste (such as the silver compounds around) will beat it for heat transferring capacity.

If you want the best thermal connection you can go as far as using wet and dry to buff the heat spreader on the CPU and the base of the heatsink to a mirror shine before applying a smear of paste. Over the top perhaps but even the oxide layer on the heatsink can increase thermal resistance.

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Grease vs Pads
by rub / February 19, 2005 2:37 AM PST

I read AMD's dictum also. I have great respect for AMD. I worked closely with them 30 years ago and they always ran a first class act. While most tech memos are "this is how it works", some are "this is how to do it" in which the author shifts gears and tries to figure out how the dummies reading it will screw up, and how to minimize the consequences. Thermal grease has always required care and understanding. Surfaces have to be clean and plane - no high spots. The grease can have no lumps, forget about wood and plastic tools. Metal cleaned with abrasive is the way to go, and don't dry it with cloth or paper. The application must be thin and uniform, in a place with no drafts to blow dust or dirt onto the suraces. I replaced my XP2800 and there was no pad accompanying the new CPU so I used my 25 year old grease, with aluumina. I previously had used silicone/beryllia ( beryllia has thermal conductivity about 10 times better, same as aluminum ) but couldn't find it. I'm not familiar with silver but it should be good unless it tends to clump. Anyway, the CPU temp had been about 58-60 C ( 25 room ambient ) with a pretty sorry looking thermal pad attached, but the new one, with all surfaces carefully cleaned and examined for high spots, ran about 45 C, and continues at that level for the last 6 months. So much for thermal pads. If you monitor the CPU temp, and I wouldn't have dared if I hadn't been able to, you'll soon know whether you have a problem. Even a poor thermal installation won't burn up the CPU immediately, but be ready to cut power.

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Paste It
by mcgilbdd / February 19, 2005 5:42 AM PST

Just use the thermal paste available at your local computer store, get the higher quality if they have different types. It normally comes in a syrenge applicator. Spread evenly, about the thickness of a sheet of printer paper using an old credit card or similar tool.An artistic, steady hand is helpful. Start with a small amount, and add as necessary to get even coverage. Mount the heat sink, and forget it. It will work just fine. It is not something to get too reved up about, unless you are into extreme overclocking. Then....the finer points come into play, just like building a race car.

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free 4"X4" samples
by bobfrompips / March 2, 2005 1:09 AM PST
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I think use phase-change materials is better
by justinhotban / July 29, 2013 10:54 AM PDT
In reply to: free 4"X4" samples

I think use phase-change materials and thermal pad is better than thermal grease, you can find many thermal interface materials from AOK Technology, It's a leading Chinese thermal management solutions providers

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