Recommended thermal paste

[Edwar65]

Hi, what reasonably priced thermal pastes can forum members recommend?
I'd like to use it on some heatsinks that have some transistors mounted on them.
The original stuff is white and rather sticky. Do I need to remove this before I re-apply and how is this removed if so?? Or can I just leave original paste on there and reclamp down to cabinet??
Thanks all.

[Edwar65]

Sorry about title,****** phone!!!!!

[Skywave]

Remove it using a clean rag and I.P.A. (Isopropyl alcohol).

Al,

[G6Tanuki]

I use this:

https://uk.rs-online.com/web/p/thermal-grease/2173835/

It's good to wipe away any old dried-out and possibly crumbly heatsink-paste from the face of the heatsink and the device-to-be-heatsinked. Car brake-cleaner aerosol is a suitable solvent. Be careful though not to damage any Mica 'shim' insulator between the device and the heatsink: when I was working with TO3-cased bipolar RF-amplifier transistors the capacitance from the transistor case [collector] to the earthed heatsink was part of the calculation for the output tank-circuit and changes due to damage to the mica could detune this.

[Edwar65]

It's being used between an aluminium u shaped heat sink and the chassis of amplifier that 2 transistors are mounted on.
Thanks for the input.

[ionburn]

It is a while ago when I bought it now and it was probably not cheap. but lasts a long time. I got some silver based paste intended for cpu heatsinks on computers. It is in a small syringe. I work on the therory of minimal thermal barrier as the paste is the weak link in the cooling chain. Maybe there are other methods than a mica shim around now too for better heat flow. I have not used a T03 for some time now so haven't looked.

[MrBungle]

I'm using this stuff for thermal paste: https://www.amazon.co.uk/dp/B0087X728K - it doesn't crack when it sets like the white stuff. Tube has lasted about 5 years so far!

Must get rid of the old stuff entirely first. Use IPA then polish the surfaces with any cheap bathroom cream cleaner (only a very tiny bit) then IPA again to get any residue off.

Also don't reuse any mica products. They tend to crack when you use them the second time. Get rid of them and buy new ones. You can get new mounting kits here without having to buy thousands at once: https://www.bitsbox.co.uk/index.php?...oducts_id=2419

Edit: ionburn - snap!

[Diabolical Artificer]

I last bought some Servisol paste off Farnell that comes in a syringe having got completely fed up with tubes splitting and the bldy stuff going everywhere.

Meths gets it off too.

Andy.

[Edwar65]

I bought this stuff from rs made by electrolube, should do the trick at £3.39.
https://uk.rs-online.com/mobile/p/th...rease/1127229/
On another note before I reconnect the amplifier boards after checking the bias, I need to connect to the power supply boards and confirm the capacitors are discharged so.i don't damage the boards.
Is there a simple method anyone can advise on to discharge the positive and negative sides of the caps?

[G8HQP Dave]

If the equipment has been off for a while then you can discharge with a short circuit across the caps; leakage current should have already reduced the voltage to a fairly safe level. If the item has been recently powered up then use a suitable resistor to discharge them a bit more slowly; fully charged electrolytics do not always like a short applied, unless they are designed to cope with this. In either case if the voltage is more than a few tens of volts make sure you don't touch the metal yourself.

[bobskie]

Originally Posted by MrBungle

I'm using this stuff for thermal paste: https://www.amazon.co.uk/dp/B0087X728K - it doesn't crack when it sets like the white stuff. Tube has lasted about 5 years so far!

This is the stuff I use too, works very well. It's still quite cheap compared to some and is tried and tested by many.

[McMurdo]

I generally use Dow Corning 340, it's not cheap but a little goes a long way. I use it for industrial thyristors and IGBTs that can pass 300-odd amps per device so it has to be reasonable quality.

I'm not a fan of the servisol stuff, it feels thin and oily although probably fine for the occasional use. I've had stuff back where it's got hot and the clear silicone oil has drained away and left very sporadic bits of the white oxide.

[gritty_dee]

I did some 'ring of death' repairs on old XBoxes and the 'arctic silver' paste was the only one which really prevented overheating. Not cheap but since then I only use that type on repairs.

[Maarten]

Originally Posted by ionburn

It is a while ago when I bought it now and it was probably not cheap. but lasts a long time. I got some silver based paste intended for cpu heatsinks on computers. It is in a small syringe. I work on the therory of minimal thermal barrier as the paste is the weak link in the cooling chain. Maybe there are other methods than a mica shim around now too for better heat flow. I have not used a T03 for some time now so haven't looked.

I wouldn't use silver based paste where isolation between the device and the heatsink is required. Even if applied carefully I feel there is an increased chance of a leakage path. Zinc oxide or aluminium oxide are in any case better isolators.

[ITAM805]

I use the Servisol paste, does anyone have an opinion on whether this is suitable for CPU/GPU's heat sinking? I ask because they always appear to use the silver/grey stuff

[ionburn]

Originally Posted by Maarten

I wouldn't use silver based paste where isolation between the device and the heatsink is required. Even if applied carefully I feel there is an increased chance of a leakage path. Zinc oxide or aluminium oxide are in any case better isolators.

I would agree. If isolation is required I add a suitable insulating pad (usually a quality type with good thermal conduction). I only rely on the paste to provide good contact. For that I suppose in theory a lapped contact with no paste would be better.

[suebutcher]

I bought some zinc oxide thermal paste from RS recently, and it came with a nine page hazardous material warning! Apparently I need gumboots, goggles, gloves and thick overalls to use it, and take care to avoid breathing the fumes, even though it's just a small tube of stiff paste. This is the same stuff that's used to treat nappy rash and is smeared over swimmers' faces in summer. OK, it is hazardous to marine life, and I won't dump the unused portion in the lake, but this is all a bit over the top and makes me wish I hadn't bought the stuff.

[MrBungle]

Same happens if you buy some solder wick. Comes in a massive box stuffed full of paperwork. It's good really as the box with solder wick in it including delivery is cheaper than the boxes are from the post office near me!

[Radio Wrangler]

Zinc oxide has serious implications if inhaled as fumes from welding. Symptoms start with mild flu, getting worse to staggering and shaking if the exposure is greater and possibly death.

Don't weld galvanised steel without a good supply of clean air.

Heatsink temperatures are far less than this! so I assume it's just a standard safety sheet for the material that's been trotted-out without any thought to the application, or the waste of paper resources.

David

[Nickthedentist]

And we use it in dentistry every day without any problems.