Nothing beats anodized aluminium in performance, but you must specify/check enough thick layer. Once I checked some brick-sized thick-anodized heatsinks that I had laying around: Dielectric strenght more than 2kV dc. Pretty impressive.Nelson Pass said:Anodizing is a pretty good insulator, but I'd still use goop.
It is not grease.
The mica layer inbetween is thinner than i have ever seen, the white stuff seems to protect the mica layer.
It doesn't feel like thermal grease, it is some sort of coating.
The insulators were in a separate plastic bag in the sealed bag of equal number power devices.
(hope you dont mind me not mentioning the device type, everytime i do that i get emails asking if i am willing to sell)
I dropped an opened pound jar of grease once, i do know thermal grease.
The mica layer inbetween is thinner than i have ever seen, the white stuff seems to protect the mica layer.
It doesn't feel like thermal grease, it is some sort of coating.
The insulators were in a separate plastic bag in the sealed bag of equal number power devices.
(hope you dont mind me not mentioning the device type, everytime i do that i get emails asking if i am willing to sell)
I dropped an opened pound jar of grease once, i do know thermal grease.
alternative to goop
back in Nov 2002 I posted this entry about a Thermalloy product that is better than grease. Check this product out. You will never mess with zinc goop again (unless you put it on your nose at the beach to avoid sunburn)
In an effort to avoid that messy grease, I found an Aavid Thermalloy product (Wakefield makes one too) that is much neater; its a waxy stick that comes in a push out applicator (kinda like a small rectangular stick deoderant!) that goes on real easy. Product spec's indicate It is 20% more efficient than grease, with no runout or "bleeding", expands once it hits 160 degree F (undergoes phase change), and cleans up easily. You can use it on any two surfaces that you would use the grease on, I think.
DigiKey carries it on the same page as other Thermalloy stuff. Look for the picture in upper left catalog page [in 2002]. Not sure if it has a number. Only drawback: costs about $17 per stick, good for 1000 sq. inches. I used it to interface some heat sink modules to a big thick aluminum plate, after getting rid of the grease that used to provide the thermal interface.
back in Nov 2002 I posted this entry about a Thermalloy product that is better than grease. Check this product out. You will never mess with zinc goop again (unless you put it on your nose at the beach to avoid sunburn)
In an effort to avoid that messy grease, I found an Aavid Thermalloy product (Wakefield makes one too) that is much neater; its a waxy stick that comes in a push out applicator (kinda like a small rectangular stick deoderant!) that goes on real easy. Product spec's indicate It is 20% more efficient than grease, with no runout or "bleeding", expands once it hits 160 degree F (undergoes phase change), and cleans up easily. You can use it on any two surfaces that you would use the grease on, I think.
DigiKey carries it on the same page as other Thermalloy stuff. Look for the picture in upper left catalog page [in 2002]. Not sure if it has a number. Only drawback: costs about $17 per stick, good for 1000 sq. inches. I used it to interface some heat sink modules to a big thick aluminum plate, after getting rid of the grease that used to provide the thermal interface.
HBarske said:
Holger,
there is a lot misinformation on web and also in the eg
"Fischer-Catalog" !
Al2O3 has a thermal conductivity of about 24W/mK
Kapton has a thermal conductivity of 0.12W/mK (Dupont)
that means Kapton is 200 times poorer.
If You calculate a TO247 base at 3.36 cm2 and You like to transfer 40W and You don´t consider the two crossings:
With Al2O3 thickness 1mm You will get a temperature difference of about 5K!
With Kapton thickness 0.05mm You will get a temperature difference of about 49.6K !
BTW in the 70ths I try Kapton with 20um and 10um (I get samples from a capacitor manufacturer) but this was mechanically not strong enough and also a mess together with the "goop"
Regards
Heinz!
JacekPlacek said:
These parts are indeed interesting.
But as already mentioned it is near impossible to get it.
Long years ago I got some samples from a manufacturer from USA (name ?) and I remember they should withstand 500V !
They consist of a 1mm Al panel witch was on both sides covered with a special hard anodic oxidation, which differs much from the normal anodic oxidation!
I found only one company in Germany which can produce this kind of oxidation but it was too expensive!
Does anyone know this kind of isolators and know where to buy nowadays?
Regards
Heinz!
ive also found that mica+heatsink grease have lower thermal
resistance then silicon washers but they wont last as long
as the silicon washers, i dont know why that is, i guess there
is some cheap mica and grease around that contributed to
these findings-inconclusive related to quality
regards
john
resistance then silicon washers but they wont last as long
as the silicon washers, i dont know why that is, i guess there
is some cheap mica and grease around that contributed to
these findings-inconclusive related to quality
regards
john
powerbecker said:
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
www.diyaudio.com/forums/showthread.php?postid=777532#post777532
Avid Thermalloy AL2O3s, thanks to the help of Mark Gulbrandsen.
Cut to size with a diamond blade.
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 Bürklin for $45.
(700 watts from 24 devices, with <0.1 C/W on an MT200 device)
Avid Thermalloy AL2O3s, thanks to the help of Mark Gulbrandsen.
Cut to size with a diamond blade.
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 Bürklin for $45.
(700 watts from 24 devices, with <0.1 C/W on an MT200 device)
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/thermalmanagement/90er_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
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/thermalmanagement/90er_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
Aluminium Oxide thermal resistance
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?lang=en&sort=&pics=&vat=0&1474242&1474382&1474386
Thickness is 3 mm and for TO-220 1.5 mm.
lineup
audio knowledge bank
jacco vermeulen said:
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?lang=en&sort=&pics=&vat=0&1474242&1474382&1474386
An externally hosted image should be here but it was not working when we last tested it.
Thickness is 3 mm and for TO-220 1.5 mm.
lineup
audio knowledge bank
JacekPlacek said:
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
Regards
Jacek
Jacek,
dziekuje bardzo for the link but this is not what I look for, because that´s 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!
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.
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.
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.
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.
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...
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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