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Using a TO-220 heat sink

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Guest

Thu May 03, 2018 8:45 pm   



>"If you have grease, use it and throw the pad away. "

Then you have to float the sink.


Guest

Thu May 03, 2018 8:45 pm   



>"** The TO220 heatsinks in the pic are only good for a couple of watts in free air - so device dissipation is low"

With all them pictures in there who knows exactly what you're getting ? Is it 5 of the finned pieces and 5 of the ones bent in a rectangle ?

>"Device temp will only vary a few degrees using different mounting interfaces. "

Yeah, because they're not dissipating shit. There isn't enough square area there to make it even worth figuring out. I wouldn't go over about double free air with those. And if they sit down flat on a PC board that will impede the airflow.


Guest

Thu May 03, 2018 8:45 pm   



>"That's why I prefer the old mica pads. "

They're no better, in fact worse. Their saving grace is dieletric strength.

George Herold
Guest

Fri May 04, 2018 12:45 am   



On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
Quote:
jurb6006_at_gmail.com wrote:
"If you have grease, use it and throw the pad away. "

Then you have to float the sink.

Why would that be difficult?


I've got boxes where the best place for the pass element
is the back panel, which is typically grounded.
(It depends on power... I'm a class A type of guy. :^)

George H.

Tom Del Rosso
Guest

Fri May 04, 2018 12:45 am   



George Herold wrote:
Quote:
On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006_at_gmail.com wrote:
"If you have grease, use it and throw the pad away. "

Then you have to float the sink.

Why would that be difficult?

I've got boxes where the best place for the pass element
is the back panel, which is typically grounded.


That's if the panel is the heat sink, but for a separate hunk of metal
(which is small like a TO-220) it should usually be possible to float
it. I would think.


> (It depends on power... I'm a class A type of guy. :^)

I can tell.

George Herold
Guest

Fri May 04, 2018 1:45 am   



On Thursday, May 3, 2018 at 7:25:39 PM UTC-4, Tom Del Rosso wrote:
Quote:
George Herold wrote:
On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006_at_gmail.com wrote:
"If you have grease, use it and throw the pad away. "

Then you have to float the sink.

Why would that be difficult?

I've got boxes where the best place for the pass element
is the back panel, which is typically grounded.

That's if the panel is the heat sink, but for a separate hunk of metal
(which is small like a TO-220) it should usually be possible to float
it. I would think.

Well at some point the heat has to make it's way to the outside
world. My first instrument at my CPoE has a bunch of floating
heat sinks. I had to add a fan. As bad as sil pad is, it's better
than air. (I've got dreams of redesigning my first instrument...
well and all the others too. :^)
Quote:


(It depends on power... I'm a class A type of guy. :^)

I can tell.

Grin,
George H.


Guest

Fri May 04, 2018 3:45 am   



>"Why would that be difficult? "

Probably isn't, but in some layouts might not be a good idea. I wonder why not just get the all plastic version.


Guest

Fri May 04, 2018 8:45 am   



On Sunday, April 29, 2018 at 1:16:29 PM UTC-4, Cursitor Doom wrote:
Quote:
On Sun, 29 Apr 2018 11:50:39 -0400, Phil Hobbs wrote:

On 04/29/18 10:19, Cursitor Doom wrote:
On Sat, 28 Apr 2018 12:09:43 -0400, Phil Hobbs wrote:

I'd compare it to a real silpad and see. If the pad itself has poor
thermal conductivity, grease won't help.

That's why I prefer the old mica pads.

Mica is OK, and so is hard anodized aluminum plus grease.

Not if you need electrical isolation.


Just so I'm getting confused, is this AC with the neutral connection going to a different panel?

John Larkin
Guest

Sat May 05, 2018 3:45 am   



On Thu, 3 May 2018 19:24:13 -0400, "Tom Del Rosso"
<fizzbintuesday_at_that-google-mail-domain.com> wrote:

Quote:
George Herold wrote:
On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006_at_gmail.com wrote:
"If you have grease, use it and throw the pad away. "

Then you have to float the sink.

Why would that be difficult?

I've got boxes where the best place for the pass element
is the back panel, which is typically grounded.

That's if the panel is the heat sink, but for a separate hunk of metal
(which is small like a TO-220) it should usually be possible to float
it. I would think.


(It depends on power... I'm a class A type of guy. :^)

I can tell.



Here's a floating heat sink. The drains of 32 mosfets (16 p-channel,
16 n-channel) are clamped to copper heat spreaders which are bolted to
the main aluminum heat sink.

The whole thing is isolated from the chassis by big plastic blocks.

https://www.dropbox.com/s/lrrhgp564oefyi8/Amp.jpg?raw=1




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Adam Funk
Guest

Tue May 08, 2018 10:45 am   



On 2018-05-03, Tom Del Rosso wrote:

Quote:
Adam Funk wrote:
Hi,

To attach an LM317 (for example) in the TO-220 format to the
corresponding heat sink (see link below), is it useful to apply any
thermal paste in addition to the flexible mat that comes with the heat
sink?

https://www.aliexpress.com/item/VAKIND-10pcs-lot-Computer-Cooling-Accessories-Heatsink-Heat-Sink-With-Screw-Sets-15-20mm-For-TO/32802123591.html

Thanks.

Obviously the purpose of either of them is to reduce thermal resistance
by conforming to imperfections in the two surfaces, but obviously using
both would have more thermal resistance than either alone.

If you have grease, use it and throw the pad away. The pad is 10 times
as thick as a layer of grease, and has 10 times the thermal resistance.


I figured the pad is only for situations where you need electrical
insulation there.


--
It's like a pair of eyes. You're looking at the umlaut, and it's
looking at you. ---David St. Hubbins

Tom Del Rosso
Guest

Tue May 08, 2018 4:45 pm   



Adam Funk wrote:
Quote:
On 2018-05-03, Tom Del Rosso wrote:

Adam Funk wrote:
Hi,

To attach an LM317 (for example) in the TO-220 format to the
corresponding heat sink (see link below), is it useful to apply any
thermal paste in addition to the flexible mat that comes with the
heat sink?

https://www.aliexpress.com/item/VAKIND-10pcs-lot-Computer-Cooling-Accessories-Heatsink-Heat-Sink-With-Screw-Sets-15-20mm-For-TO/32802123591.html

Thanks.

Obviously the purpose of either of them is to reduce thermal
resistance by conforming to imperfections in the two surfaces, but
obviously using both would have more thermal resistance than either
alone.

If you have grease, use it and throw the pad away. The pad is 10
times as thick as a layer of grease, and has 10 times the thermal
resistance.

I figured the pad is only for situations where you need electrical
insulation there.


I assumed a small heat sink can always be isolated, especially in hobby
projects (which SEB posts are usually about).

Adam Funk
Guest

Wed May 09, 2018 10:45 am   



On 2018-05-08, Tom Del Rosso wrote:

Quote:
Adam Funk wrote:
On 2018-05-03, Tom Del Rosso wrote:

Adam Funk wrote:
Hi,

To attach an LM317 (for example) in the TO-220 format to the
corresponding heat sink (see link below), is it useful to apply any
thermal paste in addition to the flexible mat that comes with the
heat sink?

https://www.aliexpress.com/item/VAKIND-10pcs-lot-Computer-Cooling-Accessories-Heatsink-Heat-Sink-With-Screw-Sets-15-20mm-For-TO/32802123591.html

Thanks.

Obviously the purpose of either of them is to reduce thermal
resistance by conforming to imperfections in the two surfaces, but
obviously using both would have more thermal resistance than either
alone.

If you have grease, use it and throw the pad away. The pad is 10
times as thick as a layer of grease, and has 10 times the thermal
resistance.

I figured the pad is only for situations where you need electrical
insulation there.

I assumed a small heat sink can always be isolated, especially in hobby
projects (which SEB posts are usually about).


Fair point!

--
svn ci -m 'come back make, all is forgiven!' build.xml

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