Types of thermal paste - Page 1
Forum section: electronics / general

author: GreyWoolfe
author_rank: Unknown
timestamp: November 25, 2013, 02:16:17 am
content: I was looking on the internet and couldn't quite find my answer. Can the same Thermal paste/grease used for computer CPUs be used for voltage regulators and their heatsinks? I would think that thermal paste is thermal paste. I would appreciate any edification on this.Tom, NW0LF

author: IanB
author_rank: Super Contributor
timestamp: November 25, 2013, 02:26:15 am
content: Yes, I would think so.There doesn't seem to be any magic to thermal paste.Its most important job is to exclude air from the mating surfaces (since air is an insulator).Then it needs to be stable, so that it does not degrade and change its properties with heat or time.After that it needs to be inert and non-corrosive.Once it has those properties there is nothing much special about it.

author: mariush
author_rank: Super Contributor
timestamp: November 25, 2013, 02:27:20 am
content: Yes, cpu thermal paste can be used on other heatsinks including voltage regulators and other chips.It's basically a paste that's designed to be applied as a thin film between the metal of the chip and the metal of the heatsink, thus eliminating pockets of air between metals (air is insulator) and conducting heat better.There are various types of pastes, some are conductive, some aren't. Most cpu pastes aren't conductive but there's a distinction between "not conductive" and insulators - if you want to have the tab of a chip insulated electrically from the heatsink you don't use pastes, you use mica or ceramic films or films designed to be isolatingSee this as an inspiration:http://uk.farnell.com/jsp/search/browse.jsp?N=204099&ref=lookahead

author: GreyWoolfe
author_rank: Unknown
timestamp: November 25, 2013, 02:32:55 am
content: I am making a small circuit with a LM7809 to power a DPM. The heatsinks that bought have the mica insulator. Mariush, you're saying I should be fine without the thermal grease?

author: IanB
author_rank: Super Contributor
timestamp: November 25, 2013, 02:37:18 am
content: Insulators are for insulation. Thermal grease is for improved heat conduction. You can use both together...(And you can drop the insulator if the part does not need to be electrically isolated from the heat sink.)

author: mariush
author_rank: Super Contributor
timestamp: November 25, 2013, 02:52:04 am
content: In some cases, you may wish to put several chips onto a single heatsink .. to save costs, to make sure both chips are warming up evenly and so on.For such situations, you use an insulator between the chip tab and the heatsink, and you generally also use a nylon/plastic "spacer" to make sure the screw pressing the chip against the heatsink does not touch the metal tab of the chip.Here's an example of such a system:That plastic ring also goes down separating the screw from the metal tab. That foil is heat conductive but is also an insulator. With this particular foil, there's no need for extra thermal paste, but if this was a mica or another type of foil, there could have been a benefit to put a drop of thermal paste between the foil and the chip tab.If your parts don't have to be isolated from the heatsink, then you can just use a cheaper paste or a basic pad and just press the chip directly on the heatsink with the screw or a clamp, like in this picture for example:

author: xrunner
author_rank: Super Contributor
timestamp: November 25, 2013, 02:59:14 am
content: Good question.The paste I bought a while back for computer use was silver.The paste I got off Ebay to repair a VHF amp was white.I have no idea why they are different colors. It can't be for looks, because who would care?

author: peter.mitchell
author_rank: Super Contributor
timestamp: November 25, 2013, 03:23:09 am
content: Quote from: xrunner on November 25, 2013, 02:59:14 amJust made of different stuff, does the same thing though.There is also another type of thermal paste, which is thermal adhesive, which both conducts heat and attaches the thing to heatsink to the package, often used on packages that aren't designed for heatsink usage or packages where they have a low thermal output.

author: mariush
author_rank: Super Contributor
timestamp: November 25, 2013, 03:25:36 am
content: Tom's Hardware recently did a sort of review/benchmark of thermal pastes available on the market:http://www.tomshardware.com/reviews/thermal-paste-performance-benchmark,3616.htmlIf you're interested, you can copy the paste names and then google them, go to the product page and read the chemical composition. Silver pastes have silver particles in them obviously, those white pastes don't, but they're cheaper and in some cases good enough... some pastes use silicone, others use zinc oxides, others use microscopic industrial diamonds, few use graphite..You may also want to have a look at the wikipedia article :http://en.wikipedia.org/wiki/Thermal_greasebut do note this... stay away from stuff with beryllium, it's very toxic... often not worth risking your health, other pastes are good enough.

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: November 25, 2013, 04:14:55 am
content: For pc`s i use the tried and trusted Arctic silver 5 for cpu heatsinks,sekisui thermal tape for small heatsinks and some gpu memory heatsinks.,and phobya thermal pads .For electronics heatsinks i just use servisol thermal paste,cheap and does the job.PCPerspective did a thermal compound test some months ago using " Mayonaisse " !http://www.pcper.com/news/General-Tech/Does-computer-smell-rotting-mayo-you

author: WarSim
author_rank: Frequent Contributor
timestamp: November 25, 2013, 04:46:12 am
content: There are many types of thermal glue/paste/grease some very common some very exotic.But unless your use is very specific it is very unlikely you will need to be concerned with most of it.In almost all cases just chose between paste, glue, grease.Then stick with insulating if you need conduction that can be added with a wire or trace.Sent from my iPad usingTapatalk

author: amyk
author_rank: Super Contributor
timestamp: November 25, 2013, 07:32:03 am
content: ...and on the topic of unusual TIM, here's another test:http://www.dansdata.com/goop.htm

author: G7PSK
author_rank: Super Contributor
timestamp: November 25, 2013, 09:47:22 am
content: I have used graphite grease in the past, it works but I did not run any tests to see if it's as good as the proper stuff. I think that there is a big market for so called special cpu heat transfer compound (or should that be conpound) aimed at the computer geeks, the criteria appears to be the more expensive the better it must be.

author: Kjelt
author_rank: Super Contributor
timestamp: November 25, 2013, 10:17:40 am
content: Quote from: GreyWoolfe on November 25, 2013, 02:32:55 amThere are also heat conducting electrically isolating materials, they vary in thickness and look like stickers (the thin ones) to bubblegum (the thick ones),firms that make them are 3M, BERGQUIST, FISHER ELEKTRONIK, AMEC THERMASOLThey name their product differently: "Thermally conductive foil" "SIL pad" "Filler pad" for instance.These are somewhat less thermal conductive then the usual thermal paste BUT probably better thermal conductive then when you add the mica insulator. Ceramic isolator might be better in that case. Also these products make a lot less of a mess which is also very very nice.and some are also available in adhesive form, although I would always use some form of a mechanical fastener myself just in case (clip, screw).Oh yeah just in case but you probably know it already: most if not all thermal pastes are very poisonous, so use proper handling/precaution.

author: rollatorwieltje
author_rank: Unknown
timestamp: November 25, 2013, 12:03:29 pm
content: Quote from: Kjelt on November 25, 2013, 10:17:40 amAfaik the LD50 of modern thermal paste is ingesting several kilos for an average person, about as dangerous as table salt. Beryllium was phased out decades ago, it is now based on boron nitride.

author: Kjelt
author_rank: Super Contributor
timestamp: November 25, 2013, 01:24:35 pm
content: Quote from: rollatorwieltje on November 25, 2013, 12:03:29 pmOk I was taught that "decades ago" so that would make sense

author: GreyWoolfe
author_rank: Unknown
timestamp: November 25, 2013, 06:11:13 pm
content: I will go ahead and use both. Looking at the data sheet, I can't tell if the pins are isolated from the mounting plate. In the Elenco XP-720K power supply kit I built, the 7805 was isolated from the heatsink which was attached to the case which provided a grounding point. The heatsink on my project will not be electrically attached to anything. It will simply have its own solder pads to hold it to the pcb that I will make.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: November 25, 2013, 09:09:00 pm
content: Note that CPU thermal paste is often overpriced. The delta between a mid-range paste ($2/gram) and a premium paste ($5-10/gram) is usually only 3-4 degrees Celsius. It's worth stepping up from the silicone paste if you want something with good long-term reliability; in addition to having mediocre heat conduction, the silicone paste also tends to dry up and crumble away after a few years. Zinc oxide is a little bit better. The silver and ceramic based compounds are pretty solid, but require a curing period (usually ~100hrs at a specified temperature), and until then perform about the same as silicone. Graphite paste is good. Diamond particle paste performs very well, but is stupid expensive. There are also dozens of proprietary formulas...

author: Fsck
author_rank: Super Contributor
timestamp: November 25, 2013, 11:28:58 pm
content: Quote from: Phaedrus on November 25, 2013, 09:09:00 pmyou can also roll your own diamond paste with a carrier and industrial diamond dust. it's not all that expensive, especially if you don't care about the colour of the dust.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 26, 2013, 03:27:32 am
content: I ended up buying Arctic Silver 5. The 3.5 gram tube was $6.83 shipped. I don't need it but only occasionally so that should last a while. The circuit is a simple 9 volt power supply that I will use the 12.6 VAC to power it. The circuit will power the LCD DPM I am adding to my Elenco XP-720K power supply kit that I built. I probably don't need the heatsink but I am adding it as my construction worker father, may he rest in peace, taught me to overbuild so it lasts. Thanks for all the input.Tom, NW0LF

author: senso
author_rank: Frequent Contributor
timestamp: April 19, 2018, 02:15:32 pm
content: Quote from: GreyWoolfe on November 26, 2013, 03:27:32 amFor less than 20$ you can buy a tube of 20gr of Artic-MX4, love using it for electronics, as well as for repaste jobs on pc's, as good, or better than Artic Silver, and much cheaper.

author: Ampera
author_rank: Super Contributor
timestamp: April 19, 2018, 03:20:41 pm
content: nobody here has yet realized this is a necrobump from 2013?This is almost five years ago.

author: raptor1956
author_rank: Frequent Contributor
timestamp: April 19, 2018, 09:01:16 pm
content: One thing I'd like to see is commentators being more specific with some of the terminology. For example, saying a foil or paste is non-conductive could be misleading given the fact that when it pulls heat from a component it is doing so via conduction. Best to say it is electrically non-conductive if that's what you meant. Even better would be electrically non-conductive but thermally conductive.Brian