VEry Important question for you who already used this two kind of insulators:
Which of this two are beter to use Aluminim Oxide or Silicon Pads insulators?
I am getting ready to install output transistors on heatsink and after I researched this topic could not make decision.
Aluminum Oxide pads are 2mm thick made for TO-247.
Silicon Pad Insulators I would need to make (cut) from 6" x 6" sheet I have.
Answer from your personall experience ,please!!
Regards
Which of this two are beter to use Aluminim Oxide or Silicon Pads insulators?
I am getting ready to install output transistors on heatsink and after I researched this topic could not make decision.
Aluminum Oxide pads are 2mm thick made for TO-247.
Silicon Pad Insulators I would need to make (cut) from 6" x 6" sheet I have.
Answer from your personall experience ,please!!
Regards
Aluminum Oxide has superior conductivity compared to silicone and mica. The only real caveat is the brittle nature of the aluminum oxide. The heatsink needs to be flat and without burrs (Aaron or Raymond or otherwise). You also need to be careful about the torque when you tignten down on aluminum oxide, or you will crack it for sure.
I have problem with understanding this whole temperature thing on Aluminum Oxide PAds.This is a sentence I found about Al Oxide: "Aluminium oxide is an excellent thermal and electrical insulator".
So fact that Aluminum Oxide is "excellent thermal insulator" is making him BAD or GOOD for temperature transfer.
In Amplifier Transistor is source of heat that needs to be transfer to heatsink.Between transistor and heatsink I need to insert Aluminum Oxide which is claimedn as "excellent thermal insulator".How will heat get transfered from transistor to heatsink thru thermal insulator.
Another spec.:The thermal conductivity of aluminum oxide is 15.06 W/mK at 75° (167° F)
?????
PLease help to clear this up!!!!
So fact that Aluminum Oxide is "excellent thermal insulator" is making him BAD or GOOD for temperature transfer.
In Amplifier Transistor is source of heat that needs to be transfer to heatsink.Between transistor and heatsink I need to insert Aluminum Oxide which is claimedn as "excellent thermal insulator".How will heat get transfered from transistor to heatsink thru thermal insulator.
Another spec.:The thermal conductivity of aluminum oxide is 15.06 W/mK at 75° (167° F)
?????
PLease help to clear this up!!!!
AndrewT said:
Thermal conductivity, percent of copper:
Copper 100%
Gold 78%
Beryllia 61%
Aluminum 53%
Aluminum nitride 27-42%
Alumina (99%) 9.4%
Kapton, quite low.
Mica, no data on file...sorry
Cheers, John
ps..almost forgot..
To reallly compare the two accurately, you need the dimensions of the silicon die, the die attach thickness (you can assume 3 mils as a default), and the case plate thickness of copper. The interface to the insulators will be the same on the die side of the insulator, but the thicker alumina spreads the heat horizontally more at the heatsing interface, giving an overall advantage to the alumina..simply comparing the total thermal resistance of the material is inadequate, you have to either use a 45 degree spread model, or mount and test the same device with both methods.
The alumina is better than mica/silpad thermally, but I typically use the latter(s).
Cheers, John
Still no answer on main question:
"I have problem with understanding this whole temperature thing on Aluminum Oxide PAds.This is a sentence I found about Al Oxide: "Aluminium oxide is an excellent thermal and electrical insulator".
So fact that Aluminum Oxide is "excellent thermal insulator" is making him BAD or GOOD for temperature transfer.
In Amplifier Transistor is source of heat that needs to be transfer to heatsink.Between transistor and heatsink I need to insert Aluminum Oxide which is claimedn as "excellent thermal insulator".How will heat get transfered from transistor to heatsink thru thermal insulator.
Another spec.:The thermal conductivity of aluminum oxide is 15.06 W/mK at 75° (167° F)
?????
PLease help to clear this up!!!!
"I have problem with understanding this whole temperature thing on Aluminum Oxide PAds.This is a sentence I found about Al Oxide: "Aluminium oxide is an excellent thermal and electrical insulator".
So fact that Aluminum Oxide is "excellent thermal insulator" is making him BAD or GOOD for temperature transfer.
In Amplifier Transistor is source of heat that needs to be transfer to heatsink.Between transistor and heatsink I need to insert Aluminum Oxide which is claimedn as "excellent thermal insulator".How will heat get transfered from transistor to heatsink thru thermal insulator.
Another spec.:The thermal conductivity of aluminum oxide is 15.06 W/mK at 75° (167° F)
?????
PLease help to clear this up!!!!
zox2003 said:
That statement is incorrect.
Aluminum oxide is an excellent electrical insulator, which also has a very high thermal conductivity (high with respect to other electrical insulators).
Aluminum nitride can be better, and beryllia is much better. But they are expensive, BeO has machining related toxicity issues.
Cheers, John
Hi,
from the Wiki Pedia link
WikiPedia is wrong.
That's the problem with the open database that can be written and altered by all.
Alu Oxide is an excellent electrical insulator.
Alu Oxide is an excellent thermal conductor.
The difficulty is that as a sheet thermal transfer layer it is usually quite thick, resulting in a significant thermal resistance as the thickness becomes even greater.
I would still like to know what thickness alu oxide can approach before it becomes worse than 0.002inch Mica.
I understand JN and the heat spreader complication, but I would like real numbers from someone that knows.
from the Wiki Pedia link
I see the problem you are having.
WikiPedia is wrong.
That's the problem with the open database that can be written and altered by all.
Alu Oxide is an excellent electrical insulator.
Alu Oxide is an excellent thermal conductor.
The difficulty is that as a sheet thermal transfer layer it is usually quite thick, resulting in a significant thermal resistance as the thickness becomes even greater.
I would still like to know what thickness alu oxide can approach before it becomes worse than 0.002inch Mica.
I understand JN and the heat spreader complication, but I would like real numbers from someone that knows.
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