Silicone based Thermal Grease/heat sink comound

[netwolf]

Hi All

I am in need of some Dow Corning 340 heatsink compound. I need it to go between a CCD sensor and the peltier and also between the peltier and heat sink. I have recently acquired a SXVF-H9 body to install a previously acquired ICX285AL sensor. This T-340 is often supplied with computer CPU and GPU 3rd party fan/heatsink mods. But I am not sure where i can directly purchase it from locally in Australia. In the UK you can buy a 145gram tube or larger quantities. I am open to alternatives that have similar properties, the most crucial being that they do not conduct electric current.


Thanks and Regards

[bojan]

Heat-sink grease is very seldom used nowadays..
The excellent alternatives arenon-silicone-based pads and patches (http://www.lightfab.com/products/gasket_cushion_seal/3M_5590H_Acrylic_Interface_pads:209 ) the thermal conductivity is the same or better, but since this is not a grease, it is clean :-) (It is unbelievable how that ugly white grease manages to be on everything I touched, it even finds its way to things I have not touched :-) )
You ca try any computer h/w shop, they are usually delivered with every processor yo buy. Once used (compressed between heat-sink and CCD or whatever you are cooling) you can not re-use it since it will be damaged too much, so you have to apply a new patch.

Good alternative could also be araldite mixed with metal powder, or electrically conductive paint (sold in spray bottles).
And, if you can not find anything from above, just silicone rubber (non-acid type) or silicone grease can be used (very thin layer will have good conductivity and the important thing her eis to remove the layer of air between the two surfaces.. Air is very good isolator (when it is not moving.. and it does not when in thin layers).

[monoxide]

Hi mate,
i've worked with all sorts of thermal pastes in my extreme pc cooling days (liquid and phase change cooling) and the best thermal paste you can get is this stuff:
http://www.scorptec.com.au/computer/27889-as-as5-12g

theres also an adhesive (epoxy) version of it here:
http://www.scorptec.com.au/computer/27890-as-asta-7g

and here is their website:
http://www.arcticsilver.com/as5.htm

[MrB]

guys:

[acropolite]

I wouldn't be relying on heat sink grease if that's the only method of electrical isolation. It is usual to have an electrical barrier in cases where electrical isolation is required often mica with the heatsink compound applied to both sides. You should be able to buy heat sink compound from Jaycar or Altronics, even DSE; it's common, there's even some listed on ebay, just google for heatsink compound. I have also seen Kapton Tape used as a heatsink barrier in inverters, although how effective it is, compared with Silicone heatsink compound I'm not sure.

[monoxide]

Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)


if you want to insulate something use dielectric grease not thermal paste!

dielectric grease = for insulating and protecting
thermal paste = a thermal transfer medium

if you are using enough thermal paste to touch any traces or electrical contacts you either arent using it in the right place or are using way too much, refer to the instructions for how to apply it properly.

[netwolf]

Pads would be ok I guess as long as they do not conduct electricity. Here is a picture of the Camera, the White square is the Peltier. The only concern is not to use a electrical current conducting substance, just in case the substance spreads to the CCD pins and causes a Short Circuit.

[netwolf]

Tj, Artic silver is one i have used before for CPU installations I have done. However I need one that has excellent thermal conductive properties but acts as a insulator for Electric currents. I think you can get one that does both.

[monoxide]

if you really need to make sure that everything is insulated though and want to make sure 100% that you wont have any problems with condensation etc get a pot of liquid electrical tape and paint the whole pcb (except for the ccd of course)

this is a method i have used to protect a mainboard when cooling a cpu to -45c and it works well, ice was formed over the top of the liquid electrical tape but i had no problems at all.

[kinetic]

Why do you need to insulate the peltier from the heatsink electrically?
Peltiers have a ceramic(insulator) wafer either side.
When you add your heatsink metal to that, it should still be electrically
insulated?

I think....

At least that's my experience with them.

Steve

[bojan]

Yes, Peltiers are ceramic, so that is not the problem.
Fahim's problem is probably because he wants to be sure two pins are not un-intentionally shorted. ...
Fahim, thermal pads are electrical isolators, so no worries..
With thermally conductive paint, you just have to use very small amount, only where it is needed and be careful not to mess everything with with it (which is sometimes very hard to do..)

[bmitchell82]

I think with the artic silver stuff its extremely good, and in the instructions it says less is more! if you have enough of it to contact other bits then you have stuffed up, like monoxide has said put it in the right place and the right amount, and it will work a dream.

[netwolf]

Thanks TJ, found this also on Scorptec's site this looks like another alternative. No silver in this one.
http://www.scorptec.com.au/computer/26993-ocztfrztc
I have used something very similar to the Artic stuff at work when replacing system boards in laptops and desktops. I used the Artic stuff when i built my own AMD based pc some years back. AMD processors back then tended to need that extra bit of cooling.

Or I think i could go with this one
http://jaycar.com.au/productView.asp?ID=NM2010&CATID=&keywords=thermal&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

This seems to be similar in properties to the Dow Corning 340 product.

Thanks everyone for your help and advise I appreciate it.

[monoxide]

ahh i remember the Unick stuff, you could squeeze the whole tube over something and still have no problems, it was sometimes used in place of dielectric grease to fill the socket on a board before a cpu went in for cascade phase change cooling (-100c or lower)

what wattage is the peltier and how are you cooling the hot side?
if it goes sub zero you will need or atleast really want to protect the pcb from condensation/ice, theres a lot of ways to do this but one of the best and easiest i found was to paint the entire pcb with liquid electrical tape which seals everything against moisture etc

you can buy the Unick stuff from DSE too

heres the liqiud electrical tape: http://www.batteriesplus.com.au/pd/935/286/liquid-electrical-tape-red/

[MrB]

DSE are likely to tell you to go elsewhere if you ask a staff member where something is, even if they have it, so hunt for it.
They are now officially out of the electronics game, they're focused solely on consumer electronics now, tv's, dvd's, pc's, toys, etc etc.

BTW, Jaycar also sell the liquid tape.
No offiliation.... oh ahhh, yes, but your unlikely to wander into my store so it doesn't matter. :)
I reckon 1/3 of our customers lately have told me they've been sent to us by DSE. And for stuff I have seen on their shelf!

[bmitchell82]

DSE suck the perverbial. Its so hard because nobody looks after the components part, you have to hunt for it and it could be anywhere. I asked one of the kids that asked if he could help me where they kept the battery packs to hold batterys, and he couldn't comprehend what i was trying to ask for.

meh. Jaycar is the new Dicksmiths.!