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removing heat with thermal tape and small heatsinks

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Winfield Hill
Guest

Mon Feb 04, 2019 11:45 pm   



John Larkin wrote...
Quote:

Winfield Hill wrote:
John Larkin wrote...
Phil Hobbs wrote:

So what are you using exactly? 6 W/m/k is quite decent.

TW-T600-2MM from 3G Shielding. I start with 2mm material
and squash it down to 1mm, which doesn't take a lot of force.

I've tested it and the thermal conductivity really is
close to 6, compressed.

I got some T600 samples last week. I wonder, does the
thermal conductivity have full inverse proportionality
to squashed thickness? They don't address compression
on the datasheet, although thickness is in the formula.

https://www.dropbox.com/s/bt8jrz77m159327/3G_TW_3.JPG?dl=0

Those measurements are obviously pretty rough.

Of course, squashing reduces both specific thermal conductivity
and thickness. That's a double whammy on theta.

The dielectric strength is 6 KV/mm.

It's fun stuff, strongly resembling used chewing gum.


Thanks, John, I look forward to playing with it.


--
Thanks,
- Win


Guest

Mon Feb 04, 2019 11:45 pm   



Winfield Hill <hill_at_rowland.harvard.edu> wrote in
news:q38bqj0acr_at_drn.newsguy.com:

Quote:
DecadentLinuxUserNumeroUno_at_decadence.org wrote...

The cost (of hard anodizing) prohibits most Mfgr's designs to
incorporate it, so most off the shelf sinks are chem etch or
simple anodize treatment, which is not insulative.

Should we be questioning the HV insulating properties of
tapes, thermally-conductive pads, gap pads, etc.?



I am not sure. It depends on just how high that voltage is. Less
than 2kV is usually worry free (read less worrysome). If you have a
truly HV circuit there. then corona and other effects start to
become worrysome even without added sinking elements. I know that
did not address your actual question. I guess it is me asking for
more particulars about the circuit.

I guess my answer is that it varies from maker to maker and
application to application. One would think that they are mostly
targetting insulative materials.

There are thermal epoxies that are also electrically conductive
though.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:pmef5ep7i43lkn4lt0qfqic2h9cel11ori_at_4ax.com:

Quote:
Sorry, I use numbers when I do engineering.



Funny, you have yet to show any numbers that have anything to do with
this application.

If you think I am wrong, why don't you call berquist and find out.

A gap pad is the wrong choice to provide a solution for this
application.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:u1ff5ehhiqrsnclplf9r0evc2i676ugghq_at_4ax.com:

Quote:
Hard anodize is reliable up to about 200 volts. It's a pretty good
thermal conductor (because it's thin) but also adds a lot of
capacitance.



You are an idiot, and obviously know nothing or even less than nothing
about hard anodized Aluminum properties.

You claiming to be scientific, and then spewing stupid cracks like
this are more proof that you stopped learning decades agao.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:5egf5e5lklq6agedgmqtce5b57b6nmuefa_at_4ax.com:

Quote:
Most IR imagers are designed for architectural use; they won't focus
closer than a few feet, and the pixel counts are pitiful. The low-end
Flir units aren't much good for electronics.



You're an abject idiot.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:5egf5e5lklq6agedgmqtce5b57b6nmuefa_at_4ax.com:

Quote:
My Flir E45 can resolve the hot spot on an 0603 resistor. It has a
$3000 germanium lens that will focus on a part that it touches.


The lens was $3000?

The IR Imager was $3000?

Which is it, Johnny?

Because if you paid $3000 for a Ge lens you are a true idiot.
I am quite sure they saw you coming.

The lens does not change the focus or resolution ya dopey dipshit.
ALL a Ge lens does is limit the spectrum the unit's IR imaging plane
gets presented to it.

And yes, I DO know. I worked in IR thermometry back when imagers
had to have an LN bath behind the image plane to cool it. and they
were only 4 frames per second at 640 x 320.

You say some of the most childish things here, and make some of
the most lame, underinformed, or even UNinformed claims and
statements I have ever seen anyone claiming to be a scientist make.

Why don't you post something derrogatory about NASA or the space
shuttle program or the ISS?


Guest

Tue Feb 05, 2019 12:45 am   



Robert Baer <robertbaer_at_localnet.com> wrote in news:KYQ5E.234980
$Ap2.158615_at_fx23.iad:

Quote:
I presume that you know that "thermally conductive" means "slightly
better than nothing".


You say some of the most stupid things ever. Are you competing with
Larkin for a stupid fuck in sed award?


Guest

Tue Feb 05, 2019 12:45 am   



Winfield Hill <hill_at_rowland.harvard.edu> wrote in
news:q3a4b9032a_at_drn.newsguy.com:

Quote:
John Larkin wrote...
Phil Hobbs wrote:

So what are you using exactly? 6 W/m/k is quite decent.

TW-T600-2MM from 3G Shielding. I start with 2mm material
and squash it down to 1mm, which doesn't take a lot of force.

I've tested it and the thermal conductivity really is
close to 6, compressed.

I got some T600 samples last week. I wonder, does the
thermal conductivity have full inverse proportionality
to squashed thickness? They don't address compression
on the datasheet, although thickness is in the formula.



Yes, the cross-sectional thickness of the compressed area of the
pad wituated over the element to be sinked matters. Thinner is
better.

The stuff is usually very expensive though, and we had to have
ours dies cut for uniformity in mil spec device mfgr. They came
with a thick foil sheet bonded to one side to interface with the
product enclosure.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:f8ef5e53v447p1kqj5v63fc2tjfu50de1q_at_4ax.com:

Quote:
One square inch if the stuff that I use, compressed to 1 mm thick, is
0.25 K/W.


We had gap pads that were the size of a 3.5 inch hard drive and they
were a quarter inch thick. The compressed cross-sectional thickness
over the areas to be sinked is the most critical because the stuff
simply is not as good as hard, intimate epoxied matings.

The level of heat being produced in his application in not something
a mushy gap pad is going to be comfortable with, even after you
compress it down to a mm thikness.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:f8ef5e53v447p1kqj5v63fc2tjfu50de1q_at_4ax.com:

Quote:
I referenced the correct action when I mentioned thermally
CONDUCTIVE
epoxy.

Messy, and hard to repair.


It is only 'messy' when a less than adept person such as yourself I
suppose is at the helm.

Look at IC chips with metal sinking attachment lids. They are ALL
attached to the die element with electrically and thermally conductive
epoxy.

Specifically Epotek H20E.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:f8ef5e53v447p1kqj5v63fc2tjfu50de1q_at_4ax.com:

Quote:

Filled epoxy isn't a good thermal conductor because it's still mostly
epoxy.


You are not very bright. Your inane lean toward thinking that no one
else in the world has any brains is as annoying as it gets.

The industry has apparently been miles ahead of your inane first use
decisions about it. You obviousLY never scientifically research
anything. .

You are a punk, at best.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:pmef5ep7i43lkn4lt0qfqic2h9cel11ori_at_4ax.com:

Quote:
But a PCB has traces and vias and connector pins. Win's board also
has surface-mount parts on the bottom side. A gap-pad conforms to
all that.


You failed to note the level of heat his parts are producing. It is
not that the gap pad would not pull heat away. The problem is that it
would not/will not/can not pull it off fast enough for that
application.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:pmef5ep7i43lkn4lt0qfqic2h9cel11ori_at_4ax.com:

Quote:
Extruded heat sinks tend to not be flat, unless you do a secondary
fly-cut pass on them. A gap-pad fixed that problem too.


His application is so small in size that any non-planarity your wee
wittle bwain attempts to come up with has exactly NIL effect

You should also try using an extruder company that actually knows
what they are doing.

YOURE extruder selection produces that crap. MINE does NOT.


Guest

Tue Feb 05, 2019 12:45 am   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:pmef5ep7i43lkn4lt0qfqic2h9cel11ori_at_4ax.com:

Quote:
Oh. I just use them to keep parts from frying.



You should have gotten one for your brain decades ago, because you
are a crispy critter, Larkin.

John Larkin
Guest

Tue Feb 05, 2019 1:45 am   



On Mon, 4 Feb 2019 23:09:05 +0000 (UTC),
DecadentLinuxUserNumeroUno_at_decadence.org wrote:

Quote:
John Larkin <jjlarkin_at_highlandtechnology.com> wrote in
news:5egf5e5lklq6agedgmqtce5b57b6nmuefa_at_4ax.com:

My Flir E45 can resolve the hot spot on an 0603 resistor. It has a
$3000 germanium lens that will focus on a part that it touches.

The lens was $3000?

The IR Imager was $3000?

Which is it, Johnny?


I clearly said "lens". The whole thing was $14K.

It was well worth it.

https://www.dropbox.com/s/zdgjg8lv39s586d/UPA800_80mW_one-side.jpg?dl=0

https://www.dropbox.com/s/rxk5dd8i6gr74nq/PCB_Short.jpg?dl=0


Quote:

Because if you paid $3000 for a Ge lens you are a true idiot.
I am quite sure they saw you coming.

The lens does not change the focus or resolution ya dopey dipshit.
ALL a Ge lens does is limit the spectrum the unit's IR imaging plane
gets presented to it.


Lenses don't focus images? Interesting claim.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

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