Hello all!
What is the best method for electrical isolation and heat dissipation in a final stage heating much?
I personally did not know that the traditional mica more silicone grease but I found other methods.
http://www.bomberg.com/Log/Files/Keratherm_eng.pdf
thank you.
Sorry for my english!
What is the best method for electrical isolation and heat dissipation in a final stage heating much?
I personally did not know that the traditional mica more silicone grease but I found other methods.
http://www.bomberg.com/Log/Files/Keratherm_eng.pdf
thank you.
Sorry for my english!
I take that graph to mean that just thermal grease was more thermally conductive.
Nothing is mentioned about the mica as far as I can see.
Best,
N-Brock
You are right, they don't *specifically* mention mica, ... and why would they?
Who wants to push "competition"?
But mica is not a "mystery" material, being the standard for many years now against which all others are compared to.
And its value can be "read" (or better said, "interpolated") from that graph easy enough.
A typical Rth value for Mica is around twice what would be achieved by grease alone, as in the old rating shown over and over in datasheets, since when Germanium Transistors were the Industry standard.
As in: "Thermal resistance case to heat sink, 0.5ºC/W with grease alone ; add 1ºC extra if mica (+ grease, of course) is used"
So I consider (for quick comparison, of course) mica +grease=3X grease alone.
And even Keratherm red does nor seem to beat that.
Can't be more precise, because that is not a proper Rth graph but a 3D bar/columns graph, so you can't exactly match column height to the scale on the left.
They do show a product which seems to beat grease + mica, which is some kind of wax (PCM).
Probably it's useful in some very special situations, but I would be very nervous using a thermal/insulating material that melts between 48 and 60ºC
Who wants to push "competition"?
But mica is not a "mystery" material, being the standard for many years now against which all others are compared to.
And its value can be "read" (or better said, "interpolated") from that graph easy enough.
A typical Rth value for Mica is around twice what would be achieved by grease alone, as in the old rating shown over and over in datasheets, since when Germanium Transistors were the Industry standard.
As in: "Thermal resistance case to heat sink, 0.5ºC/W with grease alone ; add 1ºC extra if mica (+ grease, of course) is used"
So I consider (for quick comparison, of course) mica +grease=3X grease alone.
And even Keratherm red does nor seem to beat that.
Can't be more precise, because that is not a proper Rth graph but a 3D bar/columns graph, so you can't exactly match column height to the scale on the left.
They do show a product which seems to beat grease + mica, which is some kind of wax (PCM).
Probably it's useful in some very special situations, but I would be very nervous using a thermal/insulating material that melts between 48 and 60ºC
Most modern replacement for mica+grease are aimed at quicker or more convenient assembly in a factory, not better performance. It may be that they work better when badly used, while the mica method needs to be done properly: flat heatsink (no burrs etc.), very thin layer of grease, no air pockets.
Heavy emphasis on the carefully.
If you don't get even layers then you will stress the package during mounting.
But a good idea for lower thermal resistance.
Well, I recently have been getting incredibly consistent thin micas.
But if now and then I get a thicker one, I save it in a little separate bag ... which I keep in the larger "bulk" bag anyway.
Whenever I have 20 or 30 (or more) "thick" ones, whenever I am bored doing nothing , as in waiting for my coffee to brew, I split them in half.
Easy to do once you practice a little.
A few (very few thanks God) split unevenly , meaning a thicker half and a too thin one, which sometimes cracks.
To the junkbin it goes.
But if now and then I get a thicker one, I save it in a little separate bag ... which I keep in the larger "bulk" bag anyway.
Whenever I have 20 or 30 (or more) "thick" ones, whenever I am bored doing nothing , as in waiting for my coffee to brew, I split them in half.
Easy to do once you practice a little.
A few (very few thanks God) split unevenly , meaning a thicker half and a too thin one, which sometimes cracks.
To the junkbin it goes.
The copper added to the semi increases the contact area if it is bigger and also is an immediate heatsink without the insulator, so more effective.
See my triamp. Look near the top capacitor on the left.
http://www.diyaudio.com/forums/solid-state/103152-tri-amp-completed.html
Gajanan Phadte
See my triamp. Look near the top capacitor on the left.
http://www.diyaudio.com/forums/solid-state/103152-tri-amp-completed.html
Gajanan Phadte
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