OT: Has anyone tried this product for heat-sink compound?

[Bob Villa]

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.htm

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

 

[N_Cook]

Bob Villa <pheeh.zero@gmail.com> wrote in message
news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_make

rs/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.
htm

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

What is it like when it ends up on your clothing if assemblers use handfulls
of the stuff rather than ,all that is necessary, pin-head amounts. Let alone
large area bolted together Al to Al , H/S to chassis etc - can anyone
explain why its necessary there at all let alone handfulls of it

 

[Jeff Liebermann]

On Sun, 24 Apr 2011 06:22:19 -0700 (PDT), Bob Villa
<pheeh.zero@gmail.com> wrote:

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.htm

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

I've never tried it. However, looking at the MSDS sheet at:
<http://www.permatex.com/documents/msds/01_USA-English/81878.pdf>
there doesn't seem to be any copper in the mix. I can't even figure
out which of the ingredients give it the copper color. Also, the data
sheet includes all kinds of interesting characteristics, but
conveniently leaves out thermal conductivity.
<http://www.permatex.com/documents/tds/Automotive/81878.pdf>

Since 80% of the contents are silicon greases, and the rest is a mix
of silicon dioxide (ceramic) and mica, it would appear that the
thermal conductivity is primarily controlled by these additives. Both
are good thermal conductors, but in order to be really superior, the
flakes or gains need to touch and overlap in order to conduct the
heat. With less than 20% concentration, that's not going to happen.

Note the thermal conductivity of silicon grease as compared to various
metals, which are about 100 times more thermally conductive:
<http://upload.wikimedia.org/wikipedia/commons/1/1e/Thermal_conductivity.svg>
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Bob Villa]

On Apr 24, 8:48 am, "N_Cook" <dive...@tcp.co.uk> wrote:

Bob Villa <pheeh.z...@gmail.com> wrote in message

news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gask...
rs/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.
htm



It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

What is it like when it ends up on your clothing if assemblers use handfulls
of the stuff rather than ,all that is necessary, pin-head amounts. Let alone
large area bolted together Al to Al , H/S to chassis etc - can anyone
explain why its necessary there at all let alone handfulls of it

It handles the same (consistency wise) as any thermal grease. It's gel-
like but "hardens" to a flexible but non-bonding constituent.

 

On Sun, 24 Apr 2011 06:22:19 -0700 (PDT), Bob Villa
<pheeh.zero@gmail.com> wrote:

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.htm

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v
I haven't tried it. It obviously was formulated as a substiture for

or improvement to gaskets in applications like automobile thermostat
housings. As such, it was designed more for stability at high
temperatures rather than for good thermal transfer properties.

Perhaps by using it between an older CPU and heat sink you can
determine it's heat transfer properties. Let's face it, if someone
had said "I tried it on my now computer, and the CPU runs 20°C
cooler." would you use it wthout confirming the performance?

PlainBill

 

[Bob Villa]

On Apr 24, 11:00 am, Jeff Liebermann <je...@cruzio.com> wrote:

On Sun, 24 Apr 2011 06:22:19 -0700 (PDT), Bob Villa

pheeh.z...@gmail.com> wrote:
http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

I've never tried it.  However, looking at the MSDS sheet at:
http://www.permatex.com/documents/msds/01_USA-English/81878.pdf
there doesn't seem to be any copper in the mix.  I can't even figure
out which of the ingredients give it the copper color.  Also, the data
sheet includes all kinds of interesting characteristics, but
conveniently leaves out thermal conductivity.
http://www.permatex.com/documents/tds/Automotive/81878.pdf

Since 80% of the contents are silicon greases, and the rest is a mix
of silicon dioxide (ceramic) and mica, it would appear that the
thermal conductivity is primarily controlled by these additives.  Both
are good thermal conductors, but in order to be really superior, the
flakes or gains need to touch and overlap in order to conduct the
heat.  With less than 20% concentration, that's not going to happen.

Note the thermal conductivity of silicon grease as compared to various
metals, which are about 100 times more thermally conductive:
http://upload.wikimedia.org/wikipedia/commons/1/1e/Thermal_conductivi...
--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

The reason I think it's a possible a good substitute is...it squeezes
down to an extremely thin film. If surfaces are nearly perfect...there
would be almost nothing between them.
Thanks for your input.

 

[Jeff Liebermann]

On Sun, 24 Apr 2011 10:12:28 -0700 (PDT), Bob Villa
<pheeh.zero@gmail.com> wrote:

The reason I think it's a possible a good substitute is...it squeezes
down to an extremely thin film. If surfaces are nearly perfect...there
would be almost nothing between them.

Have you ever measured the thermal transmission characteristics of
various heat sink mounting methods and the effects of thermal grease?
I have (in about 1993) using a home made fixture[1]. I have the
report buried somewhere, but as I vaguely recall, the best thermal
conductivity was achieved when both the device and the aluminum heat
sink were polished flat until they looked like mirrors, with no
thermal grease in between.

Second best was the usual rough and warped heat sink surface, with a
sheet of silver leaf in between and no grease. Silver is very very
very malleable and will fill the cracks, gouges, and small pits very
nicely. However, it's rather expensive mostly because it can't be
beaten into a thin enough sheet. Gold leaf can do this, was available
in very thin sheets, and worked almost as well as silver. Oddly, gold
leaf on polished heat sinks make things worse. Some RF xsistors had
gold plated copper bases, but as these were rough and warped, the gold
did little to improve thermal conductivity.

The absolute worst was a massive heap of silicon grease, as found on
most CPU tops. This prevents metal to metal contact, which is really
what you're trying to achieve. The grease just fills in the cracks,
evaporates somewhat, and leaves aluminum oxide dust in the crack to
provide some additional heat sinking. By itself, aluminum oxide doped
silicon grease is not very heat conductive. I didn't have any Arctic
Silver available in 1993 to test.

This test was to see what could be done to get more heat out of
commonly available RF power transistors. The use of thermal grease
resulted in extremely erratic xsistor temperatures, as different
assemblers would apply radically different amounts. One surprise was
that the most important consideration was RF transistor base warpage.
The final procedure was to polish the xsistor bases on fine sand paper
until the gold was gone and the copper base was bright and shinny.
Same with the heat sink except it was done on a buffer.

The same method will probably be useful for CPU cooling. The newer
CPU packages are already have a shiny flat mating surface. All that
would be necessary is to polish the mating heat sink. However, unlike
the RF power xsistors I was testing, most CPU sockets do not have the
luxury of compression screws, which will squeeze the gold into the
cracks and crevasses.

[1] <http://en.wikipedia.org/wiki/Thermal_conductivity_measurement>
I didn't use these methods. I was only interested in the temperature
differential across the power transistor to heat sink junction. I
heated up the transistor, and measured the differential temperature
across the gap after the heat sink temperature had stabilized. To get
a decent reading, the test heat sinks were identical solid blocks of
aluminum, cooled with chilled water running through the block.

[2] Gold leaf is not as expensive as you might thing, but is a major
handling problem. Touch it with anything and it will stick. You
can't manually handle it or it will tear. Watch out that you're not
buying "imitation" gold leaf (Dutch gold), which is thicker, and is
mostly brass, but not as thermally conductive.
<http://en.wikipedia.org/wiki/Gold_leaf>
<http://www.google.com/search?q=gold+leaf&tbs=shop%3A1&aq=f&oq=&aq=f>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[boardjunkie1]

On Apr 24, 2:22 pm, Bob Villa <pheeh.z...@gmail.com> wrote:

http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

Wow....really? You actually *want* to glue the parts to the heatsink?
Whatta mess that would make.

 

[Bob Villa]

On Apr 24, 12:43 pm, boardjunkie1 <boardjunk...@gmail.com> wrote:

On Apr 24, 2:22 pm, Bob Villa <pheeh.z...@gmail.com> wrote:

http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

Wow....really? You actually *want* to glue the parts to the heatsink?
Whatta mess that would make.

This is a non-bonding type of silicone used for sealing instead of a
gasket. Parts can be easily disassembled.

 

[N_Cook]

Jeff Liebermann <jeffl@cruzio.com> wrote in message
news:0br8r61i4pvjlsmto9pfpjka201io2fnvo@4ax.com...

On Sun, 24 Apr 2011 10:12:28 -0700 (PDT), Bob Villa
pheeh.zero@gmail.com> wrote:

The reason I think it's a possible a good substitute is...it squeezes
down to an extremely thin film. If surfaces are nearly perfect...there
would be almost nothing between them.

Have you ever measured the thermal transmission characteristics of
various heat sink mounting methods and the effects of thermal grease?
I have (in about 1993) using a home made fixture[1]. I have the
report buried somewhere, but as I vaguely recall, the best thermal
conductivity was achieved when both the device and the aluminum heat
sink were polished flat until they looked like mirrors, with no
thermal grease in between.

Second best was the usual rough and warped heat sink surface, with a
sheet of silver leaf in between and no grease. Silver is very very
very malleable and will fill the cracks, gouges, and small pits very
nicely. However, it's rather expensive mostly because it can't be
beaten into a thin enough sheet. Gold leaf can do this, was available
in very thin sheets, and worked almost as well as silver. Oddly, gold
leaf on polished heat sinks make things worse. Some RF xsistors had
gold plated copper bases, but as these were rough and warped, the gold
did little to improve thermal conductivity.

The absolute worst was a massive heap of silicon grease, as found on
most CPU tops. This prevents metal to metal contact, which is really
what you're trying to achieve. The grease just fills in the cracks,
evaporates somewhat, and leaves aluminum oxide dust in the crack to
provide some additional heat sinking. By itself, aluminum oxide doped
silicon grease is not very heat conductive. I didn't have any Arctic
Silver available in 1993 to test.

This test was to see what could be done to get more heat out of
commonly available RF power transistors. The use of thermal grease
resulted in extremely erratic xsistor temperatures, as different
assemblers would apply radically different amounts. One surprise was
that the most important consideration was RF transistor base warpage.
The final procedure was to polish the xsistor bases on fine sand paper
until the gold was gone and the copper base was bright and shinny.
Same with the heat sink except it was done on a buffer.

The same method will probably be useful for CPU cooling. The newer
CPU packages are already have a shiny flat mating surface. All that
would be necessary is to polish the mating heat sink. However, unlike
the RF power xsistors I was testing, most CPU sockets do not have the
luxury of compression screws, which will squeeze the gold into the
cracks and crevasses.

[1] <http://en.wikipedia.org/wiki/Thermal_conductivity_measurement
I didn't use these methods. I was only interested in the temperature
differential across the power transistor to heat sink junction. I
heated up the transistor, and measured the differential temperature
across the gap after the heat sink temperature had stabilized. To get
a decent reading, the test heat sinks were identical solid blocks of
aluminum, cooled with chilled water running through the block.

[2] Gold leaf is not as expensive as you might thing, but is a major
handling problem. Touch it with anything and it will stick. You
can't manually handle it or it will tear. Watch out that you're not
buying "imitation" gold leaf (Dutch gold), which is thicker, and is
mostly brass, but not as thermally conductive.
http://en.wikipedia.org/wiki/Gold_leaf
http://www.google.com/search?q=gold+leaf&tbs=shop%3A1&aq=f&oq=&aq=f

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Did you try silipads in your comparison study ? where they around in 93 ?

 

[Meat Plow]

On Sun, 24 Apr 2011 10:12:28 -0700, Bob Villa wrote:

On Apr 24, 11:00 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Sun, 24 Apr 2011 06:22:19 -0700 (PDT), Bob Villa

pheeh.z...@gmail.com> wrote:
http://www.permatex.com/products/automotive/automotive_gasketing/
gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

I've never tried it.  However, looking at the MSDS sheet at:
http://www.permatex.com/documents/msds/01_USA-English/81878.pdf> there
doesn't seem to be any copper in the mix.  I can't even figure out
which of the ingredients give it the copper color.  Also, the data
sheet includes all kinds of interesting characteristics, but
conveniently leaves out thermal conductivity.
http://www.permatex.com/documents/tds/Automotive/81878.pdf

Since 80% of the contents are silicon greases, and the rest is a mix of
silicon dioxide (ceramic) and mica, it would appear that the thermal
conductivity is primarily controlled by these additives.  Both are good
thermal conductors, but in order to be really superior, the flakes or
gains need to touch and overlap in order to conduct the heat.  With
less than 20% concentration, that's not going to happen.

Note the thermal conductivity of silicon grease as compared to various
metals, which are about 100 times more thermally conductive:
http://upload.wikimedia.org/wikipedia/commons/1/1e/
Thermal_conductivi...
--
Jeff Liebermann     je...@cruzio.com 150 Felker St #D  
 http://www.LearnByDestroying.com Santa Cruz CA
95060http://802.11junk.com Skype: JeffLiebermann     AE6KS  
 831-336-2558

The reason I think it's a possible a good substitute is...it squeezes
down to an extremely thin film. If surfaces are nearly perfect...there
would be almost nothing between them. Thanks for your input.

The best compound is one of micronized silver and ceramic particles.
After all you are trying to fill microscopic voids between device and
heatsink so they need to fit.



--
Live Fast Die Young, Leave A Pretty Corpse

 

[Jeff Liebermann]

On Sun, 24 Apr 2011 21:29:01 +0100, "N_Cook" <diverse@tcp.co.uk>
wrote:

Did you try silipads in your comparison study ? where they around in 93 ?

Memory fault and I goofed. It was about 1983. I thought I had
scanned and posted the manual for the Intech M3600 radio, but I guess
not.

<http://www.bergquistcompany.com/thermal_materials/sil-pad.htm>
Yes. They were a total disaster. Berquest and Thermalloy were making
them in one thickness and material type at the time. I don't recall
what it was, but might be able to find the data in my "archives". What
Sil-pads were good for was the ease of handling, consistency, and
cleanliness. I would have used them if they were suitable. Well, I
did use them for TO-3 and other non-RF power devices. However, this
was a performance problem, not a manufacturing exercise. The price
you pay for the benefits of silpads is a modest thermal resistance,
which was unacceptable.

We were trying to squeeze as much power out of a pair of transistors,
that would normally dissipate about 175 watts each. This had to pass
through a 30 mm^2 base to a much larger heat sink. Almost any thermal
resistance between the xsistor base and heat sink would raise the
xsistor temperature enough to initiate a thermal shutdown. Under
ideal circumstances, the heat sink should be very close to the
temperature of the transistor base. It was, but when a few degrees of
differential temperature translates into many watts LESS of RF output,
any difference was considered a bad thing. The transistors could
produce almost any RF power output desired, if only they could be kept
sufficiently cool. The other incentive was above a certain junction
temperature (which I've forgotten), thermal runaway is a real problem.

There was another problem with silpads. The base of the xistor was a
round disk with ears. We had several bases, but this was the problem
maker:
<http://www.qsl.net/df7tv/datasheets/sd1487.pdf>
When we torqued down on the mounting screws, the sil-pad material
tended to bunch together near the mounting holes, resulting in the
base taking the shape of a "bow" with less pressure in the middle. Of
course, the place where we needed the most compression was in the
middle. I contrived a layered spacer that sorta worked, but it
increased the thermal resistance even more by increasing the gap.

Incidentally, I also tried beryllium oxide insulators, mica
insulators, aluminum foil, brass shims, and various home made mixes of
aluminum oxide dust. All of them worked when properly applied and
with proper compression. However, direct metal to metal polished
contact worked best.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sun, 24 Apr 2011 19:27:39 +0000 (UTC), Meat Plow
<mhywattt@yahoo.com> wrote:

The best compound is one of micronized silver and ceramic particles.
After all you are trying to fill microscopic voids between device and
heatsink so they need to fit.

If you must use a compound, I suggest a mix of some kind of grease
that will vaporize when the heat is applied (hopefully leaving little
residue), and diamond dust:
<http://en.wikipedia.org/wiki/Material_properties_of_diamond#Thermal_conductivity>
Silver is good, but diamonds are much better.

However, the ultimate in thermal conductivity is still metal to metal.
A good example are the diodes used in automotive alternators and
industrial power equipment. These diodes are press fitted with an
arbor press into the heat sink. Metal to metal at it best with not
even microscopic gaps. I tried to get the RF power xsistor vendors
interested in an interferenc fit package, but because I didn't have a
sufficiently large purchase order, they weren't interested.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Barry]

"Bob Villa" <pheeh.zero@gmail.com> wrote in message
news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.htm

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

This stuff is NOT a silicone grease but rather a room temperature
vulcanizing silicone rubber. There is no copper in it, and it is a poor
heat conductor. General Electric used to be the manufacturer, but it
appears that they have sold out to a Chinese company. If memory serves
it used to be either RTV-60, RTV-650, or RTV-106. I cannot remember
which is the two-part and which is the one-part material. MG Chemicals
is a distributor for Momentive Performance Materials, the _obviously_
Chinese company that makes it now. They do make two higher thermal
conductivity silicones known as TSE3331 and TSE3941. The former is a
grey potting and encapsulating compound while the latter is a white
adhesive.

As Jeff Liebermann <jeffl@cruzio.com> pointed out, the smoother the
surfaces are and the closer they fit, the better the heat transfer will
be. All the silicone heat transfer grease does is fill the microscopic
void spaces (dead air space is a good thermal insulator).

Working around chemists, I had easy access to silicone vacuum stopcock
grease. I have used it in a pinch for thermal grease and it worked well.
You can find a similar grease in the plumbing department of Lowes and
Home Depot. It is used to lubricate valve stems, rubber seals, and those
ungodly expensive ceramic Price-Pfister faucets. It will work far better
than any Permatex product as a heat transfer grease.

Oh, and one other reason to not use Permatex in this application. This
silicone is an acetoxy cure which means it releases corrosive acetic acid
when it cures.

Dr. Barry L. Ornitz WA4VZQ ham_call_letters at live.com

 

[Rich Webb]

On Sun, 24 Apr 2011 12:12:58 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Sun, 24 Apr 2011 10:12:28 -0700 (PDT), Bob Villa
pheeh.zero@gmail.com> wrote:

The reason I think it's a possible a good substitute is...it squeezes
down to an extremely thin film. If surfaces are nearly perfect...there
would be almost nothing between them.

Have you ever measured the thermal transmission characteristics of
various heat sink mounting methods and the effects of thermal grease?
I have (in about 1993) using a home made fixture[1]. I have the
report buried somewhere, but as I vaguely recall, the best thermal
conductivity was achieved when both the device and the aluminum heat
sink were polished flat until they looked like mirrors, with no
thermal grease in between.

Overclockers used to (and may still; I don't play any more) spend a fair
amount of time on this for CPU heatsinks. I gave it a spin once, using a
polished marble building tile for the reference surface, successive
grades of wet-work polishing paper, and a lot of water. Much work for
just a few degrees change in delta-T but it was instructive. Also, it
was pretty cool to see just how well-polished one could get a copper
surface.

--
Rich Webb Norfolk, VA

 

[Bob Villa]

On Apr 24, 10:07 pm, "Barry" <n...@nospam.org> wrote:

"Bob Villa" <pheeh.z...@gmail.com> wrote in message

news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

This stuff is NOT a silicone grease but rather a room temperature
vulcanizing silicone rubber.  There is no copper in it, and it is a poor
heat conductor.  General Electric used to be the manufacturer, but it
appears that they have sold out to a Chinese company.  If memory serves
it used to be either RTV-60, RTV-650, or RTV-106.  I cannot remember
which is the two-part and which is the one-part material.  MG Chemicals
is a distributor for Momentive Performance Materials, the _obviously_
Chinese company that makes it now.  They do make two higher thermal
conductivity silicones known as TSE3331 and TSE3941.  The former is a
grey potting and encapsulating compound while the latter is a white
adhesive.

As Jeff Liebermann <je...@cruzio.com> pointed out, the smoother the
surfaces are and the closer they fit, the better the heat transfer will
be.  All the silicone heat transfer grease does is fill the microscopic
void spaces (dead air space is a good thermal insulator).

Working around chemists, I had easy access to silicone vacuum stopcock
grease.  I have used it in a pinch for thermal grease and it worked well.
You can find a similar grease in the plumbing department of Lowes and
Home Depot.  It is used to lubricate valve stems, rubber seals, and those
ungodly expensive ceramic Price-Pfister faucets.  It will work far better
than any Permatex product as a heat transfer grease.

Oh, and one other reason to not use Permatex in this application. This
silicone is an acetoxy cure which means it releases corrosive acetic acid
when it cures.

        Dr. Barry L. Ornitz     WA4VZQ    ham_call_letters at live.com

Thank you, Dr.

 

[Meat Plow]

On Sun, 24 Apr 2011 19:28:00 -0700, Jeff Liebermann wrote:

On Sun, 24 Apr 2011 19:27:39 +0000 (UTC), Meat Plow <mhywattt@yahoo.com
wrote:

The best compound is one of micronized silver and ceramic particles.
After all you are trying to fill microscopic voids between device and
heatsink so they need to fit.

If you must use a compound, I suggest a mix of some kind of grease that
will vaporize when the heat is applied (hopefully leaving little
residue), and diamond dust:
http://en.wikipedia.org/wiki/
Material_properties_of_diamond#Thermal_conductivity
Silver is good, but diamonds are much better.

However, the ultimate in thermal conductivity is still metal to metal. A
good example are the diodes used in automotive alternators and
industrial power equipment. These diodes are press fitted with an arbor
press into the heat sink. Metal to metal at it best with not even
microscopic gaps. I tried to get the RF power xsistor vendors
interested in an interferenc fit package, but because I didn't have a
sufficiently large purchase order, they weren't interested.

Yep the best is no need for any compound. But in an imperfect world it's
not possible on much consumer grade electronics. I switched to the Arctic
Silver paste after using a generic white compound on my new PC CPU. It's
a 120 watt quad core AMD overclocked from 3.2 to 4 ghz. I noticed the CPU
running very near its upper limit so I removed the compound and applied
the Arctic paste. The results were a 5-7 degree Celsius drop in idle and
load temperatures. The cooling apparatus was packaged with the CPU so I
know it was designed specifically for it. No it's not a drastic drop
in temp but enough to convince me that for my purposes it's the best
choice of pastes.



--
Live Fast Die Young, Leave A Pretty Corpse

 

[Barry]

"Bob Villa" <pheeh.zero@gmail.com> wrote in message
news:a42aa133-7d44-4573-85b0-6cf2fd911fb4@q32g2000yqn.googlegroups.com...
On Apr 24, 10:07 pm, "Barry" <n...@nospam.org> wrote:

"Bob Villa" <pheeh.z...@gmail.com> wrote in message

news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

This stuff is NOT a silicone grease but rather a room temperature
vulcanizing silicone rubber. There is no copper in it, and it is a poor
heat conductor. General Electric used to be the manufacturer, but it
appears that they have sold out to a Chinese company. If memory serves
it used to be either RTV-60, RTV-650, or RTV-106. I cannot remember
which is the two-part and which is the one-part material. MG Chemicals
is a distributor for Momentive Performance Materials, the _obviously_
Chinese company that makes it now. They do make two higher thermal
conductivity silicones known as TSE3331 and TSE3941. The former is a
grey potting and encapsulating compound while the latter is a white
adhesive.

~The tube I have says, "Made in USA".

I suspect Permatex used to buy from GE because their sales would be too
small to manufacture it themselves. If you look for GE silicones, many
companies still stock them. However if it is made in China and sold in
bulk and Permatex packages it for sale, I think they can get away with
calling it "Made in the USA."

If you go to a gardening supply and buy genuine Holland tulip bulbs, you
will likely get bulbs grown in Washington state. These bulbs are shipped
to the Netherlands and packaged. This allows them to be called "imported
from Holland."

Most pharmaceutical intermediates are today made in India or China, and
many drugs are totally made there and shipped to U.S. manufacturers who
compound the drugs with fillers and then stamp out the pills. They then
qualify as U.S. made pills.

As you no doubt can tell, I am not very enamored with the pharmaceutical
industry. I take colchicine for ankylosing spondylitis. As a drug, it
has been around for over 2000 years and is normally used to treat gout.
My usage is "off-label" meaning it was prescribed for other than its
approved use. My rheumatologist gave it to me for its anti-inflammatory
properties since my congestive heart failure prevents me from using
NSAIDs (non-steroidal anti-inflammatory drugs reduce your kidney
function). A number of generic drug manufacturers made it and a three
month supply cost less than $10. One "unnamed" pharmaceutical
manufacturer decided to go through the FDA testing and got it approved.
They then were able to get the FDA to force all the generic houses to
stop selling it. That three month supply is now well over $400. By the
way, these numbers are AFTER insurance.

"Made in the United States of America" somehow doesn't mean what it once
did.

73, Dr. Barry L. Ornitz WA4VZQ ham_call_letters at
live.com

 

[Bob Villa]

On Apr 24, 10:07 pm, "Barry" <n...@nospam.org> wrote:

"Bob Villa" <pheeh.z...@gmail.com> wrote in message

news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com...

http://www.permatex.com/products/automotive/automotive_gasketing/gask...

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

This stuff is NOT a silicone grease but rather a room temperature
vulcanizing silicone rubber.  There is no copper in it, and it is a poor
heat conductor.  General Electric used to be the manufacturer, but it
appears that they have sold out to a Chinese company.  If memory serves
it used to be either RTV-60, RTV-650, or RTV-106.  I cannot remember
which is the two-part and which is the one-part material.  MG Chemicals
is a distributor for Momentive Performance Materials, the _obviously_
Chinese company that makes it now.  They do make two higher thermal
conductivity silicones known as TSE3331 and TSE3941.  The former is a
grey potting and encapsulating compound while the latter is a white
adhesive.

As Jeff Liebermann <je...@cruzio.com> pointed out, the smoother the
surfaces are and the closer they fit, the better the heat transfer will
be.  All the silicone heat transfer grease does is fill the microscopic
void spaces (dead air space is a good thermal insulator).

Working around chemists, I had easy access to silicone vacuum stopcock
grease.  I have used it in a pinch for thermal grease and it worked well.
You can find a similar grease in the plumbing department of Lowes and
Home Depot.  It is used to lubricate valve stems, rubber seals, and those
ungodly expensive ceramic Price-Pfister faucets.  It will work far better
than any Permatex product as a heat transfer grease.

Oh, and one other reason to not use Permatex in this application. This
silicone is an acetoxy cure which means it releases corrosive acetic acid
when it cures.

        Dr. Barry L. Ornitz     WA4VZQ    ham_call_letters at live.com

The tube I have says, "Made in USA".

 

[larry moe 'n curly]

Bob Villa wrote:

On Apr 24, 10:07 pm, "Barry" <n...@nospam.org> wrote:
"Bob Villa" <pheeh.z...@gmail.com> wrote in message

news:0a0e4aa2-74a4-4c20-bb66-5b2b021bec7f@u15g2000vby.googlegroups.com....

http://www.permatex.com/products/automotive/automotive_gasketing/gask....

It would "seem" to have good properties for filling minute gaps;
copper for heat transfer; can't dry-out; not a bonding type on
silicone.

Thanks
bob_v

This stuff is NOT a silicone grease but rather a room temperature
vulcanizing silicone rubber.  There is no copper in it, and it is a poor
heat conductor.  General Electric used to be the manufacturer, but it
appears that they have sold out to a Chinese company.  If memory serves
it used to be either RTV-60, RTV-650, or RTV-106.  I cannot remember
which is the two-part and which is the one-part material.  MG Chemicals
is a distributor for Momentive Performance Materials, the _obviously_
Chinese company that makes it now.  They do make two higher thermal
conductivity silicones known as TSE3331 and TSE3941.  The former is a
grey potting and encapsulating compound while the latter is a white
adhesive.

As Jeff Liebermann <je...@cruzio.com> pointed out, the smoother the
surfaces are and the closer they fit, the better the heat transfer will
be.  All the silicone heat transfer grease does is fill the microscopic
void spaces (dead air space is a good thermal insulator).

Working around chemists, I had easy access to silicone vacuum stopcock
grease.  I have used it in a pinch for thermal grease and it worked well.
You can find a similar grease in the plumbing department of Lowes and
Home Depot.  It is used to lubricate valve stems, rubber seals, and those
ungodly expensive ceramic Price-Pfister faucets.  It will work far better
than any Permatex product as a heat transfer grease.

Oh, and one other reason to not use Permatex in this application. This
silicone is an acetoxy cure which means it releases corrosive acetic acid
when it cures.

        Dr. Barry L. Ornitz     WA4VZQ    ham_call_letters at live.com

Thank you, Dr.

The Dr. is right, except for possibly one point: Ultra Copper does
NOT release acetic acid when it cures because it's instead alcohol-
based to be safe for use in cars equipped with exhaust oxygen
sensors. All of the Permatex silicone RTVs with the word "Ultra" in
their names are made for oxygen sensor compatibility, and all of them
smell like alcohol before they're cured. Also "Copper" refers only to
the color (actually reddish brown) and physical characteristics and is
not an indication of any copper content (none). BTW Permatex doesn't
produce silicone RTV in different colors merely for cosmetic purposes,
and many if not all of the colors indicate different physical
characteristics. For example, Ultra Copper is made to withstand
higher temperatures than any of their other RTVs, while Ultra Grey is
for gaskets with bolts that are close together, and they have others
made for withstanding gear oil or antifreeze:

www.permatex.com/products/Automotive/automotive_gasketing/gasket_makers.htm