Quote:
Originally Posted by CamLight
With the heat sinks used in my 400W electronic loads, using four TO-264 MOSFETs, the sink-to-ambient thermal resistance (of my heat sink and fan combo) was increased approximately 0.04C/W over the bare aluminum number. This is at least 10x better than any other material that can be used.
Don't underestimate the power of being thin. 
Type III anodizing, while being a VERY efficient insulator (electrically and thermally) is so thin when applied to a heat sink that it really doesn't matter. Yea, if you increase the thickness you can probably block a blowtorch, but when thin, it allows enough heat to flow vs. its dielectric strength (ability to electricall insulate) that there's just about no other material that can match it. Certainly not any thermal pad, mica, kapton tape, etc. They might be able to if they were 1/2 mil thick...but they're not. 
Do you know how thick the Type III lining was for those ICE piston? I suspect it's more for reduced friction and wear-resistance than heat-flow blocking...unless a very thick layer was applied. |
Sounds like you've done your homework CamLight...I like those numbers. I do agree with you though to go as thin as possible while still being effective as an electrical insulator. In the Piston example the coating was much thicker than 1/2 a mil, and you're talking about primarily radiant heat transfer rather than conduction, which might account for a significant difference.
At 1/2 a mil are you really talking about Type II coating at that point? I thought the primary difference between Type II and Type III anodizing was the thickness...with a "hard coat" starting at around 2 mils.