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Old 17th October 2006, 10:20 AM   #51
EUVL is offline EUVL  Europe
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Thermal conductivity of Aluminium oxide is 18W/m/C.
Thermal conductivity of Aluminium nitride is 180W/m/C.

But they usually come in 1mm thickness, 0.5mm perhaps if you are lucky. And because they are rigid, you still need a grease (or arctic silver, or Aavid Ultrastick, or .....) to fill the gaps on both sides of the insulation to transistor / heatsink. Which increases the thermal resistance.

You may therefore consider this :

Keratherm 86/90
www.kerafol.com
http://kerafol.de/jml/pdfdocs/therma...er_serie_e.pdf

Thermal conductivity 10W/m/C (no big deal).
Standard thickness 0.1mm (hence factor of 5 better than 1mm Al2O3).
It is flexible (to an extent) like Silpad, so no need for additional thermal compound.

Datasheet too large to attach, unfortunately.
And a bit tricky to use (fragile to handle). Be warned.


Cheers,
Patrick
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Old 17th October 2006, 10:34 AM   #52
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Patrick,

interesting stuff.
Any idea of a corporate distributor of Kerafol products in Deutschland ? (can't seem to find any on their website)
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Old 17th October 2006, 11:13 AM   #53
lineup is offline lineup  Sweden
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Default Aluminium Oxide thermal resistance

Quote:
Originally posted by jacco vermeulen
Thermalloy AL2O3s,
......

Much better than Mica, Kapton, Bergquist K-10 samples.
Or any other silicone pad/sheet i've tried in 20 years time, starting with the 0.25mm V6245 silicone sheet i bought at Brklin for $45.

(700 watts from 24 devices, with <0.1 C/W on an MT200 device)
jacco is right
Aluminium Oxide has got low thermal resistance!

It is not as easy to use as silicon sheets or pieces.
For AlO You have to use correct amount of thermal grease on both sides.

A compromise would be to use some silicone sheets for lower power applications
and use Aluminium Oxide bricks for High Power major projects
like Class A, where heating is really a factor.

http://www.elfa.se/en/
Electromechanics/Pneumatics
Heatsinks
Installation accessories
http://www.elfa.se/elfa-bin/lt.pl?la...474382&1474386

Click the image to open in full size.
Thickness is 3 mm and for TO-220 1.5 mm.
Quote:
Manufacturer: Austerlitz
Aluminium oxide washers have a significantly lower thermal resistance than both mica, kapton and silicone rubber. The insulation voltage is also lower. Thickness: 3 mm for ALO-3 and ALO-P3-3, and 1.5 mm for ALO- 220.
Thermal resistance: <0.3 /W
Isolation voltage: 30 kV
Temperature resistance: >400 C
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Old 17th October 2006, 12:42 PM   #54
EUVL is offline EUVL  Europe
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> Any idea of a corporate distributor of Kerafol products in Deutschland ? (can't seem to find any on their website)

Just call or email them direct. They'll tell you who to contact.

Patrick
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Old 18th October 2006, 12:27 AM   #55
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Quote:
Originally posted by JacekPlacek



Hi ! Do You really need pads based on pure AL ? What about mentioned by me pads based on pure Al2O3 ? If You are interested , go to Polish site www.tme.com.pl ( german and english languages supported as well ). There are few types of Al203 pads in different shapes with cost no more than 1.5 Euro. I checked today and they are on stock. I do not know if TME do exports packages but check it.

Regards
Jacek
Jacek,

dziekuje bardzo for the link but this is not what I look for, because thats pure Al2O3!
This I can get in Berlin laser cut with a thickness of 0.635mm.

But anyway thank You for this link, because my 2. home is at Wroclaw I am always interested about polish electronic traders!
Please can You give me a link to polish electronic magazines?

Regards
Heinz!
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Old 18th October 2006, 12:37 AM   #56
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Quote:
Originally posted by EUVL
Thermal conductivity of Aluminium oxide is 18W/m/C.
Thermal conductivity of Aluminium nitride is 180W/m/C.

But they usually come in 1mm thickness, 0.5mm perhaps if you are lucky. And because they are rigid, you still need a grease (or arctic silver, or Aavid Ultrastick, or .....) to fill the gaps on both sides of the insulation to transistor / heatsink. Which increases the thermal resistance.

You may therefore consider this :

Keratherm 86/90
www.kerafol.com
http://kerafol.de/jml/pdfdocs/therma...er_serie_e.pdf

Thermal conductivity 10W/m/C (no big deal).
Standard thickness 0.1mm (hence factor of 5 better than 1mm Al2O3).
It is flexible (to an extent) like Silpad, so no need for additional thermal compound.

Datasheet too large to attach, unfortunately.
And a bit tricky to use (fragile to handle). Be warned.


Cheers,
Patrick
Patrick,
thank You for this link!
0.1mm near pure Al2O3 is REALLY interesting!

BTW kerafol call for pure Al2O3 also 24W/m/K.

Regards
Heinz!
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Old 19th October 2006, 02:51 AM   #57
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Default Artik Silver

Evening All,

1. I was under the impression that Artik Silver was conductive rather than non-conductive. Can anyone verify one way or t'other, please.

2. Is the silicone goop conductive or non-conductive. I have only finished one power amp requiring insulation of output devices so far, and it sent me absolutely spare trying to ensure that there was no grease contacting front and back surfaces of the mica, and yet still have lots of grease to ensure good contact. I was using a silicon grease, I think ... came with a kit!)

Was I wasting my time??

Regards,
George.
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Old 19th October 2006, 03:52 AM   #58
KBK is offline KBK  Canada
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How expensive are those oxide insulators?

I remember speaking with a designer (we were sharing cool ideas) of $80K+ items. I had found a item for use in their circuitry that would be 1/4 of the price of what he was paying... for 4x the performance. There were literally 100's of these items in this piece of gear. In the end, after he knew that the new part was superior, he refused. He explaind that his pricing was a factor of costs,and he's have to lower his prices..and make less per item.

I think these are likely to be 'de riguer' for high end amps.
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Old 19th October 2006, 04:36 AM   #59
GD3 is offline GD3  United States
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Here's an idea

On a flat anodized surface, I mounted some TO-220's directly using automotive RTV as an adhesive. This was in a case where I had no pre-drilled holes for screw mount.

I don't have any data or measurements, but the thin layer (pressure applied while it cured) of silicone that remained after most of it oozed out appears to work well. As long as there are no burrs to pierce the anodizing.

Also, here's a cleaning tip: White silicone goop is easily dissolved with WD-40

In a severe pinch, I've even used it to revive dried goop on an old part...
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Old 19th October 2006, 07:25 AM   #60
awpagan is offline awpagan  Australia
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Default Re: Artik Silver

Quote:
Originally posted by GeorgeBoles
Evening All,

1. I was under the impression that Artik Silver was conductive rather than non-conductive. Can anyone verify one way or t'other, please.

2. Is the silicone goop conductive or non-conductive. I have only finished one power amp requiring insulation of output devices so far, and it sent me absolutely spare trying to ensure that there was no grease contacting front and back surfaces of the mica, and yet still have lots of grease to ensure good contact. I was using a silicon grease, I think ... came with a kit!)

Was I wasting my time??

Regards,
George.
apparently capactive
http://www.arcticsilver.com/as5.htm

I would like to know if anyone has tried it i audio applications.
and of any suggestions

allan
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