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new 10.125" wide heatsink

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One reason why there will never be any perfectly smooth heatsink could be due to the finning on one side
Another reason could be the pace in production, to keep cost down
But I dont know

Ironically the bigger case trannies will have the worst issues:bawling:
Or when using mounting angles

Wonder if theres any measuremnts/specs as to how much a heatsink gets out of shape when very hot, due to the finning on one side
Or is it a complete non issue :scratch:
 
tinitus said:
One reason why there will never be any perfectly smooth heatsink could be due to the finning on one side
Another reason could be the pace in production, to keep cost down
But I dont know

Ironically the bigger case trannies will have the worst issues:bawling:
Or when using mounting angles

Wonder if theres any measuremnts/specs as to how much a heatsink gets out of shape when very hot, due to the finning on one side
Or is it a complete non issue :scratch:


Tinitus,

You pose a very sound question. Speaking from complete unauthority, it would seem that warping / cupping would be an inherent problem due to the fins. By design, the fins cool down first and the thickest part cools slowest. I would tend to think that the HS would warp on it's own.
Milling would be required for a flat surface. Although we only need a flat surface the size of the Mosfet(s).

Ron
 
Hello diy guys
the reason the flatness is off a little is they are trying to get the feed into the die at the correct speed and also getting the cooling at the correct speed,and type.
its a 98% feed issue at this point most of the hot aluminum flows out of the base first because of less restriction so they block that part off to get the fins to fill at the same rate as the base.when the die runs correctly it will be flat.within industry standard tolerances.
the wider the part the more lax the tolerances are
Hope this helps
Russ
 
Hi,
imagine a circle approximated by short straight chords around the perimeter/circumference.
The shorter each chord length relative to the diameter, the closer the approximation to the true circle.

Look at the curvature on the baseplate of a heatsink. How large is the diameter that such a curvature will define?

How short are the chords of that flat(straight) surface of a transistor relative to that extremely large diameter? 1:100, or 1:1000, or 1:10000?

Whether the curve of the heatsink mounting surface is caused during manufacture or as a result of differential temperature across the thickness of the backplate, the out of straightness of the heat conducting interface is inconsequential, if the isolator/conductor has just a little compliance.

Much more important is the smoothness of the interfaces and exclusion of air from the interface.
 
Hi everyone,
I just purchased some of these heat-sinks last month and the problem mentioned before on post 57 is still present. They are concave by 1/32nd of an inch or .8mm in the middle of the 10 inch with. It was not mentioned anywhere on their site, just tough some of you guy's might want to know.
Eric
 
Hi everyone,
I just purchased some of these heat-sinks last month and the problem mentioned before on post 57 is still present. They are concave by 1/32nd of an inch or .8mm in the middle of the 10 inch with. It was not mentioned anywhere on their site, just tough some of you guy's might want to know.
Eric
In response to the 1/32" (0.03125) concave base on our 10.080" profile heatsinks; I would like to point out that the standard Aluminum Industry Standard for this width profile is .08064". So, providing you are measuring with a pin gauge on a flatness table, your measurment is well below the allowed tolerence for this profile. Quoting responses to this thread before, no extrusion (especially on a 10.080" wide and 2.875" tall) heatsink will ever be perfectly flat due to the very nature of the extrusion process itself. I do however agree with the poster about putting this information on the website, we will make this information available asap. If a person is not familiar with the Aluminum Industry, they would have no reason to be familiar with industry tolerences.
 
Hi,
30thou (=0.03" = 30mil = 0.762mm) of curvature in a 10.08" plate is roughly equivalent to a 35' radius on that plate. (actually, radius = 423.345")

If you take a 1" wide heat source, say a To264 device and calculate what effect that radius has on the out of flatness between the sink and the device you will find that over the 1" of contact width, the maximum gap to be filled with conductive paste is ~0.3thou.
Firstly the bolting of the device to the heatsink will pull in all of that gap (due to radius) to near zero.
Secondly, the aluminium plate can have much of this radius eliminated by clamping a bar across the backplate.

The force required and the stress set up in the aluminium can be derived from M/I = E/R = sigma/half thickness. sigma is the stress in the outer most fibre of the aluminium beam formed by the ~10mm thick plate.

The only effect of that radius is aesthetic and can easily be solved by gently bolting the backplate to a properly machined case that has been manufactured to meet the users required tolerances.
 
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