PC hardware forum: Thermal pad or compound?

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.

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 -----Willy

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. Overall, it isn't a real concern, just apply a normal amount. Here's a link for such insight:
http://www.heatsink-guide.com/compound.htm

enjoy -----Willy

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.

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.

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!!!!!!!!!!!!!

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 Dick Smith. I think you should have those in NZ.

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.

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.

Its 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.

I have installed several CPUs, 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).

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.

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.

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.

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.

Follow this link and you can receive 2 samples which should be more than enough for several cpus.


http://www.chomerics.com/products/thermattachT404_405_412.htm