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LAN_403

dmg

Wed Jul 13 2011, 11:01PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

I didn't want to put this in the general or TC section, as I feel this has no real techincal relevance worth to those forums.. mostly just a layout suggestion.

As simple and silly as this problem is, I am looking for some suggestions. I kind of cannot make up my mind how to layout some IGBTs on a heatsink,
I guess this is more of an aesthetic matter rather then a practical one, as contact on the heatsink will not really change either way, its just my heatsink has grooves to it, originally made for mounting bars, but I guess I can't deside weather to place them forward or on the side.

#1

IGBTlayout001

So make up my mind for me please, #1 or #2?
Right now the heatsink is a bit warped and uneven, so Ill mill it flat later, and bolt some fans on.

Thanks.

Killa-X

Thu Jul 14 2011, 02:05AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Probably doesnt matter much, I only pick 1 because you dont have a non-contact line going down the middle of the igbt. Option one looks like you have full contact with the IGBT to the heatsink. Option two, you loose that small middle area. Plus, the IGBTs run with the lines, length wise...so...I pick 1.

rp181

Thu Jul 14 2011, 03:35AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

I agree with arcstarter, but I pick two. Doesn't look like one even leaves enough room to drill and tap a complete hole, it will hit the groove.

Arcstarter

Thu Jul 14 2011, 03:45AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

rp181 wrote ...

I agree with arcstarter, but I pick two. Doesn't look like one even leaves enough room to drill and tap a complete hole, it will hit the groove.

Do you now? Thanks for the link GBD, it was so worth it!

But yea, i would also go with two

dmg

Thu Jul 14 2011, 03:50AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

Yeah, it was an an awsome machine you got there 101111, I really look forward to seeing the end result.

But yeah, id also go with #2

Oh wai...

Sulaiman

Thu Jul 14 2011, 12:26PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Not just aesthetics,
the heatsinks will work best when the airflow is parallel to the fins
so align the igbts to allow the fins to be vertical if free-air cooling is planned
or consider where the fans will be if forced-air cooled.

Ash Small

Thu Jul 14 2011, 12:49PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Sulaiman wrote ...

Not just aesthetics,
the heatsinks will work best when the airflow is parallel to the fins
so align the igbts to allow the fins to be vertical if free-air cooling is planned
or consider where the fans will be if forced-air cooled.

Turbulence is also a large factor here, if the air is just flowing through the fins, only a small percentage of the air molecules come into contact with the fins, and extract heat energy. a turbulent airflow means more air molecules will carry heat away, even if the turbulence results in a (slightly) smaller volume of air being moved in total. (this is one of the main things I tried to design into my fan cooled heatsinks that I will be posting details of very soon)

Sulaiman

Thu Jul 14 2011, 07:46PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

You would have great difficulty preventing turbulence!

The 'best' way to mount a fan on a heatsink like this is to have it blow into the center of the finned area, like cpu coolers, plenty of turbulence.
e.g. in the above photo's the fan would be beneath the heatsink blowing upwards.

Marko

Thu Jul 14 2011, 08:55PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I'd go for 1 but with igbt's moved a bit apart so that outer bolts go exactly into those grooves and the inner ones avoid the central groove. Should be easier to drill than drilling a hole that is on the edge of a groove and avoids places of no thermal contact on the middle of the igbt.

Marko

Killa-X

Fri Jul 15 2011, 01:10AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

rp181 wrote ...

I agree with arcstarter, but I pick two. Doesn't look like one even leaves enough room to drill and tap a complete hole, it will hit the groove.

Really it depends how thick his heatsink is. I had to mount an IGBT on a heatsink with over 30 fins, it was a 7" x 10" x 3 inch heatsink. Obviously, you can drill without going through fins. But the base was 1CM thick, maybe 12mm. I was able to drill and tap for 1/4" bolts, and it worked out just fine..I was able to screw the IGBT down very tight, and all was well.

Yes, its easier to drill straight through when you have the ability to, I'm just saying its not really a need if the base is thick enough, and your drill press has measurements to stop at, so you can make sure you dont punch through to the fins.

Both are well designs, I just felt like pointing that case out =D

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