Using a TO-220 heat sink

[John Larkin]

On Sat, 28 Apr 2018 21:11:01 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

On 2018-04-26, Adam Funk <a24061@ducksburg.com> 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

I'd use paste only, unless an electrical connection between regulator
and heatsink would cause problems. That rubber stuff is for when you
need an insulator between the TO220 and the heatsink.

That's a tiny heat sink, so the sil-pad theta shouldn't matter much.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Sun, 29 Apr 2018 11:50:39 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> 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.

Cheers

Phil Hobbs

AlN is incredible. It conducts heat almost as well as aluminum.

https://www.dropbox.com/s/vsumcjjawrtiu0o/AlXX.JPG?raw=1




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Mon, 30 Apr 2018 09:58:45 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Sunday, April 29, 2018 at 5:09:13 PM UTC-4, Phil Hobbs wrote:
On 04/29/18 16:56, Ralph Mowery wrote:
In article <pc4ulb$5oo$25@dont-email.me>, curd@notformail.com says...
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.




The only reason I know of to use mica or the anoidized aluminum plus
grease for them is when you need electrical isolation, otherwise just
use the grease or one of the rubber type pads. The pads are good for
isolation or heat transfer.

Hopefully both, but either way they're inferior to mica + good HS
grease. A lot cleaner and more convenient though!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Is mica any better than a sil pad? I thought it was worse.
I found this,
http://www.ti.com/lit/an/sboa020/sboa020.pdf
there's a table on page 2. But inconclusive... maybe mica is better.

George H.

Mica is good because it's thin. Anodized aluminum is even thinner.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[whit3rd]

On Monday, April 30, 2018 at 9:58:48 AM UTC-7, George Herold wrote:

Is mica any better than a sil pad? I thought it was worse.
I found this,
http://www.ti.com/lit/an/sboa020/sboa020.pdf
there's a table on page 2. But inconclusive... maybe mica is better.

Mica and silpads require, in addition, a bolt with shoulder washer and
insulating sleeve, nut, maybe washer, or nylon hardware. A 'fulpack'
variant TO220 just takes a screw or rivet, or a spring clip.

 

[Adam Funk]

On 2018-04-26, George Herold wrote:

On Thursday, April 26, 2018 at 5:30:07 AM UTC-4, 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.

How much heat are you dissipating? (can you float the heat sink?)
I usually don't use any thermal paste with a sil pad.

The LM317 will only be powered for short periods, so it probably
doesn't matter match.


--
Apparently I lack some particular perversion which today's
employer is seeking. --- Ignatius J Reilly

 

[George Herold]

On Monday, April 30, 2018 at 5:58:55 PM UTC-4, Ralph Mowery wrote:

In article <a9ac8b2f-d5d8-4059-88f5-3329fe7dbf3c@googlegroups.com>,
gherold@teachspin.com says...

OK the only thing I ever tested was a sil pad versus Kapton tape.
(TO-220) I didn't use any goop on the tape. (and it was tape with a
layer of adhesive on one side.) The sil pad worked better. I think it
was 1 mil tape (0.001"), but we have 2 mil tape too and it might have been
that.

George H.



I thought Kapton was more of a heat insulator. I have only used it as a
heat shield when using the hot air wand on surface mounted devices so
don't know much about its properties.

Right, I used it as an electrical insulator. I thought because it's
thin it might be better than a thicker sil pad. It wasn't.

George h.

 

[George Herold]

On Monday, April 30, 2018 at 7:50:26 PM UTC-4, John Larkin wrote:

On Sun, 29 Apr 2018 11:50:39 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> 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.

Cheers

Phil Hobbs

AlN is incredible. It conducts heat almost as well as aluminum.

https://www.dropbox.com/s/vsumcjjawrtiu0o/AlXX.JPG?raw=1
Nice, where did you get them? and how much?

George H.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Tue, 1 May 2018 09:56:50 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Monday, April 30, 2018 at 7:50:26 PM UTC-4, John Larkin wrote:
On Sun, 29 Apr 2018 11:50:39 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> 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.

Cheers

Phil Hobbs

AlN is incredible. It conducts heat almost as well as aluminum.

https://www.dropbox.com/s/vsumcjjawrtiu0o/AlXX.JPG?raw=1
Nice, where did you get them? and how much?

George H.

I got samples from St Gobain, but I'm having a hard time buying more.

I'm having some custom made from machinable AlN, which is actually a
mix of AlN and BN, which doesn't conduct heat quite as well. They
haven't come in yet.

I got one quote for pure AlN TO-220 insulators at $25 each. The custom
parts will be $5 each. One Chinese source claims 80 cents.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Tom Del Rosso]

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.

 

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

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

 

>"** 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.

 

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

Then you have to float the sink.

 

[Tom Del Rosso]

jurb6006@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?

 

[George Herold]

On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:

jurb6006@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]

George Herold wrote:

On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006@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]

On Thursday, May 3, 2018 at 7:25:39 PM UTC-4, Tom Del Rosso wrote:

George Herold wrote:
On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006@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. :^)

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

I can tell.

Grin,
George H.

 

>"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.

 

On Sunday, April 29, 2018 at 1:16:29 PM UTC-4, Cursitor Doom wrote:

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]

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

George Herold wrote:
On Thursday, May 3, 2018 at 3:44:21 PM UTC-4, Tom Del Rosso wrote:
jurb6006@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]

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.


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