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Nov 04 2010
By: curiousecat Uncharted Territory 1475 posts
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a Word about Thermal Grease

19 replies 490 views Edited Nov 4, 2010

Call it thermal grease as that is what it is!

 There are a great deal of threads being posted about thermal grease..and we over clockers love the stuff.

 But on this Topic with regards  to the PS3. if you want Sony to repair or replace your Out of warnaty unit. Don't open it.

 

 

 

Thermal grease, to be exact. "Thermal transfer compound", if you want to be formal. It's the stuff you put between your CPU and your CPU cooler, to aid in the transfer of heat from the former to the latter.

All modern PC CPUs produce enough heat that they need a heat sink. Almost all of them need a heat sink with a fan. Many heat sinks come with some sort of thermal transfer thingy pre-applied - a patch of grease, or a square of chewing-gum-like semi-solid material, or just a rubbery pad for the low performance units. Most CPUs don't produce enough heat that the stuff you put between the chip package and the heat sink matters very much, as long as the computer case has decent ventilation and the ambient temperature isn't sauna-like. There just has to be something between CPU and heat sink.

The reason why there has to be something there is that the two mating surfaces of processor and sink aren't flat. They may look flat. They may have a mirror polish. But, on the microscopic scale, they look like a scale model of the Andes. And the mountains on one item do not match the valleys on the other.

Without thermal transfer compound, everywhere heat sink metal doesn't mate with CPU package material is a teeny-tiny air gap. Air is a good thermal insulator. As long as your heat sink looks flat when you lay a ruler on it then there'll be a decent amount of actual contact, of course, but the amount of heat that'll actually make it around the air gaps may be surprisingly small.

Hence, thermal compound. It's grease with lots of minuscule thermally conductive particles mixed into it, basically. It doesn't conduct heat as well as direct contact, but it's a heck of a lot better than air gaps.

A popular view among those of us who've spent more time cleaning thermal grease off our hands than we'd care to remember is that it doesn't really matter much what kind of thermal grease you use. Plain cheap white zinc-oxide grease, fancy silver grease, ultra-fancy super-exotic better-than-the-stuff-NASA-uses grease; they're all much the same. As long as you apply the stuff reasonably sparingly.

I'd never actually tested this, though. Perhaps the marketing  for the current crop of exotic super-greases was right; perhaps they really are spectacularly better than plain cheap white thermal goop. Perhaps the fancy greases have advantages beyond their thermal performance, too.

 

 

Aditional information you maynot be aware of:

 

Thermal greases use one or more different thermally conductive substances:

  • Ceramic-based thermal grease has generally good thermal conductivity and is usually composed of a ceramic powder suspended in a liquid or gelatinous silicone compound, which may be described as 'silicone paste' or 'silicone thermal compound'. The most commonly used ceramics and their thermal conductivities (in units of W/(m ·K)) are: beryllium oxide (218), aluminum nitride (170), aluminum oxide (39), zinc oxide (21), and silicon dioxide (1). Thermal grease is usually white in colour since these ceramics are all white in powder form.
  • Metal-based thermal grease contain solid metal particles (usually silver or aluminum). It has a better thermal conductivity (and is more expensive) than ceramic-based grease.
  • Carbon based. There are products based on with carbon-based conductors, using diamond powder, or short carbon fibers , they have the best thermal conductivity and are generally more expensive than metal-based thermal grease.
  • Liquid metal based. Some thermal pastes are made of liquid metal alloys of gallium. These are rare and expensive.

All but the last classification of compound usually use silicone grease as a medium, a heat conductor in itself, though some manufacturers prefer use of fractions of mineral oil.

Purpose

Thermal grease is primarily used in the electronics and computer industries to assist a heat sink to draw heat away from a semiconductor component such as an integrated circuit or transistor.

Thermally conductive paste improves the efficiency of a heatsink by filling air gaps that occur when the irregular surface of a heat generating component is pressed against the irregular surface of a heatsink, air being approximately 8000 times less efficient at conducting heat (see thermal conductivity) than, for example, aluminum, a common heatsink material. Surface imperfections inherently arise from limitations in manufacturing technology and range in size from visible and tactile flaws such as machining marks or casting irregularities to sub-microscopic ones not visible to the naked eye.

As such, both the thermal conductivity and the "conformability" (i.e., the ability of the material to conform to irregular surfaces) are the important characteristics of thermal grease.

Both high power handling transistors, like those in a conventional audio amplifier, and high speed integrated circuits, such as the central processing unit (CPU) of a personal computer, generate sufficient heat to require the use of thermal grease in addition to the heatsink. High temperatures cause semiconductors to change their switching properties to the point of failure while CPU power dissipation overheating causes logic errors as heat raises electrical resistance on the multi-nanometer wide circuits of the CPU core.

Properties

The metal oxide and nitride particles suspended in silicone thermal compounds have thermal conductivities of up to 220 W/(m·K). (In comparison, the thermal conductivity of metals used particle additions, copper is 380 W/(m·K), silver 429 and aluminum 237.) The typical thermal conductivities of the silicone compounds are 0.7 to 3 W/(m·K). Silver thermal compounds may have a conductivity of 3 to 8 W/(m·K) or more.

In compounds containing suspended particles, the properties of the fluid may well be the most important. As seen by the thermal conductivity measures above, the conductivity is closer to that of the fluid components rather than the ceramic or metal components. Other properties of fluid components that are important for thermal grease might be:

  1. How well it fills the gaps and conforms to both the component's and the heat sink's uneven surfaces.
  2. How well it adheres to those surfaces
  3. How well it maintains its consistency over the required temperature range
  4. How well it resists drying out or flaking over time
  5. Whether it degrades with oxidation or breaks down over time

The compound must also be smooth and creamy so that it is easy to apply in a very thin layer.

 Practical Use

In one test, a commercial silicone heatsink grease was compared to ordinary 20% zinc oxide USP ointment (available in any pharmacy and often used for diaper rash). There was no difference in performance: both greases showed a temperature of 63C for the same Pentium 4, 3.4 GHz processor in the same computer under the same load conditions.

Another test concludes that the practical difference between different products is only marginal.

Application and removal

Computer processor heatsinks utilize a variety of designs to promote better thermal transfer between components. Some thermal greases have a durability up to at least 8 years. Flat and smooth surfaces may use a small line method to apply material, and exposed heat-pipe surfaces will be best prepared with multiple lines.

Excess grease separating the metal surfaces more than the minimum necessary to exclude air gaps will only degrade conductivity, increasing the risk of overheating. It should also be noted that silver-based thermal grease can also be slightly electrically conductive. If excess were to flow onto the circuits, it could cause a short circuit.

Over time, some thermal greases may dry out, loose some of its heat transferring capabilities, set like glue and make it difficult to remove the heat sink. If too much force is applied the processor may be damaged. Heating the grease by turning the processor on for a short period often softens the adhesion. If you put the heatsink on, then take it off, you should reapply the thermal grease. First, wet compound that's dried out won't have the density, and thus the thermal conductivity, that it had when it was wet. These compounds aren't a solution, they're a mixture; remove the liquid from them and you end up with lots of little spaces where the liquid was, which is bad.

The preferred way to remove typical silicone oil-based thermal grease from a component or heat sink is by using isopropyl alcohol (rubbing alcohol). If none is available, pure acetone is also a valid method of removal. There are also special purpose cleaners made for removing the grease and purifying the surfaces of the contacts.

 

I hope you find this informative andIhope it opens youeyes to a few things.

SCEA’s decision to implement Update 3.21 placed Plaintiffs and Class members in a “Hobson’s Choice.” PS3 owners who chose not to install Update 3.21 could no longer access
many of the other important PS3 features including the PSN, the ability to play games online, the ability to access online features, or the ability to play newer PS3 games and/or Blu-ray discs that required Update 3.21. On the other hand, PS3 owners who did install Update 3.21 lost all access to the computer functionality of the PS3’s “Other OS” feature.
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Treasure Hunter
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Re: a Word about Thermal Grease

Nov 4, 2010

curiousecat wrote:

 

 But on this Topic with regards  to the PS3. if you want Sony to repair or replace your Out of warnaty unit. Don't open it.

 

 

 

 

if your warrenty is over, and you are paying, sony will still repair/replace a system that has been opened.

as long as all the parts are there and there are no obvious signs of abuse.

 

 

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Uncharted Territory
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Re: a Word about Thermal Grease

Nov 4, 2010

didnt know this but..fromwhat the operator toldme over the phone, she empahsized if the console was opend...maybe she was wrong?

SCEA’s decision to implement Update 3.21 placed Plaintiffs and Class members in a “Hobson’s Choice.” PS3 owners who chose not to install Update 3.21 could no longer access
many of the other important PS3 features including the PSN, the ability to play games online, the ability to access online features, or the ability to play newer PS3 games and/or Blu-ray discs that required Update 3.21. On the other hand, PS3 owners who did install Update 3.21 lost all access to the computer functionality of the PS3’s “Other OS” feature.
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Treasure Hunter
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Re: a Word about Thermal Grease

Nov 4, 2010

curiousecat wrote:

didnt know this but..fromwhat the operator toldme over the phone, she empahsized if the console was opend...maybe she was wrong?


she must have been thinking of a repair under warrenty. my friends 60gig was replaced with a refurb after we had opened it. 

he asked about it before he sent it and was told that they would still repair/replace it as long as nothing was missing, and there was no user caused damage.

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Uncharted Territory
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Re: a Word about Thermal Grease

Nov 4, 2010

ah makes sence so thenI guess wecan open it if it is out of warnety to at least clean the thing...well that is nice to know cause using air,some times just doesnotcut themustard lol.

 

eh how the heck did this happen, ? I posted on the other topic and it showed up here? Unless one was replying while reading this at the same time?


Chingkwee wrote:

curiousecat wrote:

didnt know this but..fromwhat the operator toldme over the phone, she empahsized if the console was opend...maybe she was wrong?


she must have been thinking of a repair under warrenty. my friends 60gig was replaced with a refurb after we had opened it. 

he asked about it before he sent it and was told that they would still repair/replace it as long as nothing was missing, and there was no user caused damage.


 

SCEA’s decision to implement Update 3.21 placed Plaintiffs and Class members in a “Hobson’s Choice.” PS3 owners who chose not to install Update 3.21 could no longer access
many of the other important PS3 features including the PSN, the ability to play games online, the ability to access online features, or the ability to play newer PS3 games and/or Blu-ray discs that required Update 3.21. On the other hand, PS3 owners who did install Update 3.21 lost all access to the computer functionality of the PS3’s “Other OS” feature.
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Lombax Warrior
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Re: a Word about Thermal Grease

Nov 4, 2010

I think the biggest improvement on high quality thermal paste over cheap ones is that they last for years and never dries out and they offer slightly better performance(lower temperatures).

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Wastelander
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Re: a Word about Thermal Grease

Nov 4, 2010

 


Chingkwee wrote:

curiousecat wrote:

 

 But on this Topic with regards  to the PS3. if you want Sony to repair or replace your Out of warnaty unit. Don't open it.

 

 

 

 

if your warrenty is over, and you are paying, sony will still repair/replace a system that has been opened.

as long as all the parts are there and there are no obvious signs of abuse.

 

 


Didn't know that! Thanks for the info!

 

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PIayStation MVP
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Re: a Word about Thermal Grease

Nov 4, 2010

curiousecat wrote:

Call it thermal grease as that is what it is!

 There are a great deal of threads being posted about thermal grease..and we over clockers love the stuff.

 But on this Topic with regards  to the PS3. if you want Sony to repair or replace your Out of warnaty unit. Don't open it.

 

 

 

Thermal grease, to be exact. "Thermal transfer compound", if you want to be formal. It's the stuff you put between your CPU and your CPU cooler, to aid in the transfer of heat from the former to the latter.

All modern PC CPUs produce enough heat that they need a heat sink. Almost all of them need a heat sink with a fan. Many heat sinks come with some sort of thermal transfer thingy pre-applied - a patch of grease, or a square of chewing-gum-like semi-solid material, or just a rubbery pad for the low performance units. Most CPUs don't produce enough heat that the stuff you put between the chip package and the heat sink matters very much, as long as the computer case has decent ventilation and the ambient temperature isn't sauna-like. There just has to be something between CPU and heat sink.

The reason why there has to be something there is that the two mating surfaces of processor and sink aren't flat. They may look flat. They may have a mirror polish. But, on the microscopic scale, they look like a scale model of the Andes. And the mountains on one item do not match the valleys on the other.

Without thermal transfer compound, everywhere heat sink metal doesn't mate with CPU package material is a teeny-tiny air gap. Air is a good thermal insulator. As long as your heat sink looks flat when you lay a ruler on it then there'll be a decent amount of actual contact, of course, but the amount of heat that'll actually make it around the air gaps may be surprisingly small.

Hence, thermal compound. It's grease with lots of minuscule thermally conductive particles mixed into it, basically. It doesn't conduct heat as well as direct contact, but it's a heck of a lot better than air gaps.

A popular view among those of us who've spent more time cleaning thermal grease off our hands than we'd care to remember is that it doesn't really matter much what kind of thermal grease you use. Plain cheap white zinc-oxide grease, fancy silver grease, ultra-fancy super-exotic better-than-the-stuff-NASA-uses grease; they're all much the same. As long as you apply the stuff reasonably sparingly.

I'd never actually tested this, though. Perhaps the marketing  for the current crop of exotic super-greases was right; perhaps they really are spectacularly better than plain cheap white thermal goop. Perhaps the fancy greases have advantages beyond their thermal performance, too.

 


There have been independent tests made that shows a difference in performance of the thermal paste(s). The cheap stuff doesn't hold up to the more expensive pastes, as we can see with the stuff that Sony uses, so they are not all the same. The cheap stuff averages about $3, while the more expensive stuff averages $10. Not that much of a cost difference seeing that there is a significant performance and duability difference...

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Fender Bender
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Re: a Word about Thermal Grease

Nov 5, 2010

alzubieri wrote:

 

I think the biggest improvement on high quality thermal paste over cheap ones is that they last for years and never dries out and they offer slightly better performance(lower temperatures).


They all dry out. Almost any thermal compound you're likely to use has silicone grease as the medium, and that can and will dry out.

 

 


Logical_Dolphin wrote:

 

There have been independent tests made that shows a difference in performance of the thermal paste(s). The cheap stuff doesn't hold up to the more expensive pastes, as we can see with the stuff that Sony uses, so they are not all the same. The cheap stuff averages about $3, while the more expensive stuff averages $10. Not that much of a cost difference seeing that there is a significant performance and duability difference...


If you check out those independent tests, you'll notice that the actual difference in performance is fairly minor. It's measurable, sure, and every little bit helps, but it doesn't mean that the ones at the bottom of the list are "bad". I think you'd agree that it's far more important to replace the thermal compound periodically, even if it's the "bad" stuff, rather than use the good stuff once and never replace it.

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PIayStation MVP
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Re: a Word about Thermal Grease

Nov 5, 2010

PyrrhusRex wrote:

alzubieri wrote:

 

I think the biggest improvement on high quality thermal paste over cheap ones is that they last for years and never dries out and they offer slightly better performance(lower temperatures).


They all dry out. Almost any thermal compound you're likely to use has silicone grease as the medium, and that can and will dry out.

 

 


Logical_Dolphin wrote:

 

There have been independent tests made that shows a difference in performance of the thermal paste(s). The cheap stuff doesn't hold up to the more expensive pastes, as we can see with the stuff that Sony uses, so they are not all the same. The cheap stuff averages about $3, while the more expensive stuff averages $10. Not that much of a cost difference seeing that there is a significant performance and duability difference...


If you check out those independent tests, you'll notice that the actual difference in performance is fairly minor. It's measurable, sure, and every little bit helps, but it doesn't mean that the ones at the bottom of the list are "bad". I think you'd agree that it's far more important to replace the thermal compound periodically, even if it's the "bad" stuff, rather than use the good stuff once and never replace it.


I disagree. AS5 and IC7 have been stated by the manufacturer that they are very stable compounds, and they shouldn't need periodic application. Even if it did eventually dry out, it should last long enough to take me to the PS4.  Although the temp decreases may seem minor, it is considered significant in the PC building community. AS5 can get a processor up to 10 degrees cooler than the cheap grease, and IC7 averages 4 degrees better than AS5...

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