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! 😀
You might consider using copper plate fixed to your heatsink, to improve heat dissipation.
Gajanan Phadte
Gajanan Phadte
From the Keratherm graph on Page 7, mica + grease is better than even the best of their materials , Keratherm Red , so ... I'll keep using mica + grease in the foreseeable future.
From the Keratherm graph on Page 7, mica + grease is better than even the best of their materials , Keratherm Red , so ... I'll keep using mica + grease in the foreseeable future.
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.
I will also stick with mica.
You should realise though that "standard" mica washers are much thicker and have a much higher voltage breakdown than is normally needed.
You can carefully de-laminate mica washers to reduce their thickness considerably and thus reduce Rth.
Frank
You should realise though that "standard" mica washers are much thicker and have a much higher voltage breakdown than is normally needed.
You can carefully de-laminate mica washers to reduce their thickness considerably and thus reduce Rth.
Frank
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.
Fully agree #2
...You can carefully de-laminate mica washers to reduce their thickness considerably and thus reduce Rth.
Frank
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.
Mount devices to copper heat spreaders that are electrically insulated from the main heatsink.
Do you have an example to show us? 🙄
In the lab we use sapphire plates due to their excellent electrical insulation properties while still having high thermal conductivity - but maybe no realistic DIY option...
Rundmaus
Rundmaus
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
- Status
- Not open for further replies.
- Home
- Design & Build
- Construction Tips
- heat dissipation method