Topics

Tek 603 - question on transistor heatsinking material

toby@...
 

Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

Mlynch001
 

Toby,

I believe that is Mylar. You can find this out for certain in one of the many resources in TekWiki.

Most I have seen have some sort of thermal compound.

--
Michael Lynch
Dardanelle, AR

John Gord
 

Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

John Gord
 

Toby,
It looks like the part number is 342-0082-00, described as an insulator plate, 0.52" x 0.52" x 0.015", material: alumina (aluminum oxide).
It is likely used with thermal compound added,
--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

toby@...
 

On 2020-07-02 1:00 a.m., John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards.
That sounds probable. It sure is brittle, while this board was hard to
remove, there would have been no major shocks, so I was surprised to see
it shattered.

Hope I can replace it, or is there a better alternative now?


--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

toby@...
 

On 2020-07-02 1:29 a.m., John Gord via groups.io wrote:
Toby,
It looks like the part number is 342-0082-00, described as an insulator plate, 0.52" x 0.52" x 0.015", material: alumina (aluminum oxide).
It is likely used with thermal compound added,
Unless Walter at Sphere has the alumina, I might have to go with mica --
Digikey has some reasonably compatible rectangular pieces.

https://www.digikey.ca/en/products/filter/thermal-pads-sheets/218

Thanks a lot, John. It was lazy of me not to consult the parts list
before posting...

--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

John Gord
 

Toby,
It looks like there are several devices held in place with a common clamp bar. If that is the case, you need to match thickness fairly well, or perhaps use a thinner insulator like mica while adding a resilient spacer under the clamp bar to compensate for the difference.
--John

On Wed, Jul 1, 2020 at 11:09 PM, <toby@...> wrote:


On 2020-07-02 1:29 a.m., John Gord via groups.io wrote:
Toby,
It looks like the part number is 342-0082-00, described as an insulator
plate, 0.52" x 0.52" x 0.015", material: alumina (aluminum oxide).
It is likely used with thermal compound added,
Unless Walter at Sphere has the alumina, I might have to go with mica --
Digikey has some reasonably compatible rectangular pieces.

https://www.digikey.ca/en/products/filter/thermal-pads-sheets/218

Thanks a lot, John. It was lazy of me not to consult the parts list
before posting...

--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby

Chuck Harris
 

It has been reported that Tektronix used BeO ceramic all
over the place.

Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.

They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.

This particular heat sink insulator looks probable to me.

Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.

You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.

Regardless of what it is, you will need heatsink compound.

The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.

About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.

-Chuck Harris

John Gord via groups.io wrote:

Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby


Chuck Harris
 

It probably shattered when it was tightened. It will do that in
a blink if the aluminum under it is not perfectly flat.

I would goop it up, and put the pieces back into service.

I you can't, or are unwilling to do that, replace them all with a
thick silicone heatsink pad. The down side is anything but the
ceramic will have different a different dielectric constant, and
will change the capacitance to ground. That may, or may not be
important.

-Chuck Harris

toby@... wrote:

On 2020-07-02 1:00 a.m., John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards.
That sounds probable. It sure is brittle, while this board was hard to
remove, there would have been no major shocks, so I was surprised to see
it shattered.

Hope I can replace it, or is there a better alternative now?


--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby




stevenhorii
 

Beryllium and compounds have an unusual toxicity profile. Beryllium is not
directly toxic as, say, arsenic is. However, how it harms you is to cause
an intense allergic reaction. In the lungs, this results in fibrosis from
the inflammation and severely affects lung function. Chuck is correct in
that most companies tinted BeO parts pink but I have certainly seen
non-tinted parts. I once found some long white pipes in a surplus yard.
Though they were not pink, they had a warning label on them. I alerted the
owner to this and he said he’d be careful, but he was somewhat pleased
because beryllia scraps out at a higher price than alumina.

Chuck is also correct in that beryllium and its compounds are safe if you
don’t create dust or fumes from them (no grinding or welding). Slivers of
beryllium can cause an allergic reaction in your skin around the sliver.
You should be safe using the heatsink pad as intended but it does need
heatsink compound to be effective.

Steve H.

On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:

It has been reported that Tektronix used BeO ceramic all
over the place.

Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.

They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.

This particular heat sink insulator looks probable to me.

Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.

You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.

Regardless of what it is, you will need heatsink compound.

The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.

About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.

-Chuck Harris

John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina
(aluminum oxide). It is a good electrical insulator and a reasonably good
thermal conductor. Beryllium oxide looks similar, but is unlikely here
because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby




toby@...
 

On 2020-07-02 9:24 a.m., Chuck Harris wrote:
It probably shattered when it was tightened. It will do that in
a blink if the aluminum under it is not perfectly flat.

I would goop it up, and put the pieces back into service.

I you can't, or are unwilling to do that, replace them all with a
thick silicone heatsink pad. The down side is anything but the
ceramic will have different a different dielectric constant, and
will change the capacitance to ground. That may, or may not be
important.
Thanks as always, Chuck!

These pads are under the low voltage (< 45V) TO-202 Darlingtons. Most
likely I can reuse them.

--Toby


-Chuck Harris

toby@... wrote:
On 2020-07-02 1:00 a.m., John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards.
That sounds probable. It sure is brittle, while this board was hard to
remove, there would have been no major shocks, so I was surprised to see
it shattered.

Hope I can replace it, or is there a better alternative now?


--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby





toby@...
 

On 2020-07-02 2:46 a.m., John Gord via groups.io wrote:
Toby,
It looks like there are several devices held in place with a common clamp bar. If that is the case, you need to match thickness fairly well, or perhaps use a thinner insulator like mica while adding a resilient spacer under the clamp bar to compensate for the difference.
That is correct. If I went with the mica, I can always use 2 pieces; I
ordered some anyway, it's quite cheap at Digikey. I guess a bonus is
that it's unlikely to break when clamped.

--Toby

--John

On Wed, Jul 1, 2020 at 11:09 PM, <toby@...> wrote:


On 2020-07-02 1:29 a.m., John Gord via groups.io wrote:
Toby,
It looks like the part number is 342-0082-00, described as an insulator
plate, 0.52" x 0.52" x 0.015", material: alumina (aluminum oxide).
It is likely used with thermal compound added,
Unless Walter at Sphere has the alumina, I might have to go with mica --
Digikey has some reasonably compatible rectangular pieces.

https://www.digikey.ca/en/products/filter/thermal-pads-sheets/218

Thanks a lot, John. It was lazy of me not to consult the parts list
before posting...

--Toby


--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby


Bruce Griffiths
 

I have some pink tinted alumina TO3 insulators as well as some blue tinted beryllia ones from the 1970's.
The beryllia ones are much colder to the touch than the alumina ones.

Bruce

On 03 July 2020 at 02:19 stevenhorii <sonodocsch@...> wrote:


Beryllium and compounds have an unusual toxicity profile. Beryllium is not
directly toxic as, say, arsenic is. However, how it harms you is to cause
an intense allergic reaction. In the lungs, this results in fibrosis from
the inflammation and severely affects lung function. Chuck is correct in
that most companies tinted BeO parts pink but I have certainly seen
non-tinted parts. I once found some long white pipes in a surplus yard.
Though they were not pink, they had a warning label on them. I alerted the
owner to this and he said he’d be careful, but he was somewhat pleased
because beryllia scraps out at a higher price than alumina.

Chuck is also correct in that beryllium and its compounds are safe if you
don’t create dust or fumes from them (no grinding or welding). Slivers of
beryllium can cause an allergic reaction in your skin around the sliver.
You should be safe using the heatsink pad as intended but it does need
heatsink compound to be effective.

Steve H.

On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:

It has been reported that Tektronix used BeO ceramic all
over the place.

Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.

They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.

This particular heat sink insulator looks probable to me.

Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.

You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.

Regardless of what it is, you will need heatsink compound.

The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.

About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.

-Chuck Harris

John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina
(aluminum oxide). It is a good electrical insulator and a reasonably good
thermal conductor. Beryllium oxide looks similar, but is unlikely here
because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby





scm@...
 

There exists (existed?) a product called beryllia microspheres which can be used safely to increase the thermal conductivity of epoxy, silicone encapsulants, etc. They are also suitable for mixing into silicone grease; and (I think) they are the critical ingredient in high quality white thermal greases. They are very small but not as small as dust, which is the dangerous form. Also, they have smooth surfaces without dangerous microscopic roughness. I think they were developed in the 1960s or 1970s (a quick google search of patents turns up some filings in that time period). They were not cheap (I bought a pound around 1970 and the price, as I recollect, was not in the budget class - at least for a graduate student). They have come in very handy over the years.

Stephen

Chuck Harris
 

Beryllium ceramic is fascinating stuff. We all would use it a lot
more but for the liability issues.

It feels a lot like aluminum in that it draws the heat away from your
skin very quickly, making it feel perpetually cool when all but the
part that is touching you, is at room temperature. Most other
ceramics are pretty good insulators, so they feel warm and cozy as
their surface warms quickly to your skin temperature.

Another fun ceramic is the foamed stuff used for the space shuttle's
heat shield. This stuff heats up instantly bright yellow when you
play a propane torch on its surface, but take the flame off of the
tile, and you can touch it immediately, and it doesn't even feel more
than warm.

-Chuck Harris

Bruce Griffiths wrote:

I have some pink tinted alumina TO3 insulators as well as some blue tinted beryllia ones from the 1970's.
The beryllia ones are much colder to the touch than the alumina ones.

Bruce

On 03 July 2020 at 02:19 stevenhorii <sonodocsch@...> wrote:


Beryllium and compounds have an unusual toxicity profile. Beryllium is not
directly toxic as, say, arsenic is. However, how it harms you is to cause
an intense allergic reaction. In the lungs, this results in fibrosis from
the inflammation and severely affects lung function. Chuck is correct in
that most companies tinted BeO parts pink but I have certainly seen
non-tinted parts. I once found some long white pipes in a surplus yard.
Though they were not pink, they had a warning label on them. I alerted the
owner to this and he said he’d be careful, but he was somewhat pleased
because beryllia scraps out at a higher price than alumina.

Chuck is also correct in that beryllium and its compounds are safe if you
don’t create dust or fumes from them (no grinding or welding). Slivers of
beryllium can cause an allergic reaction in your skin around the sliver.
You should be safe using the heatsink pad as intended but it does need
heatsink compound to be effective.

Steve H.

On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:

It has been reported that Tektronix used BeO ceramic all
over the place.

Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.

They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.

This particular heat sink insulator looks probable to me.

Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.

You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.

Regardless of what it is, you will need heatsink compound.

The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.

About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.

-Chuck Harris

John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina
(aluminum oxide). It is a good electrical insulator and a reasonably good
thermal conductor. Beryllium oxide looks similar, but is unlikely here
because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby







stevenhorii
 

We see cases of berylliosis (the beryllium lung disease) around here
because there were a couple of aerospace manufacturers in the area.
Beryllium is widely used in aerospace applications because of its light
weight and high rigidity. Like aluminum, it forms an oxide layer quickly
which helps it resist further oxidation. I have seen beryllium parts that
are black anodized so without a warning label, you would not know it (these
were used in the optical equipment for the Apollo spacecraft). The Apollo
command module optical unit that housed the sextant and scanning telescope
and the Alignment Optical Telescope used in the Lunar module were mostly
beryllium. Unfortunately, scrap dealers found this out and equipment that
was sold off as excess after the Apollo program was canceled was scrapped
for the beryllium. I saw the results of this myself, so I know it happened.
I visited a surplus dealer who also scrapped stuff. I found the
non-beryllium remnants of three of the Apollo command module optical units
and four of the LM AOTs. He still had the transit cases for the telescopes.
All of this was brand new stuff. Kollsman Instrument was the contractor
for the Apollo optical equipment and he had purchased it from them.
Beryllium was scrapping at about $120 a pound then. The Command Module
optical unit weighed about 70 pounds and at least 60 pounds of that was
beryllium. The method of scrapping was not disassembly - it was to smash
things with hammers. Sad.

On Thu, Jul 2, 2020 at 11:10 Chuck Harris <cfharris@...> wrote:

Beryllium ceramic is fascinating stuff. We all would use it a lot
more but for the liability issues.

It feels a lot like aluminum in that it draws the heat away from your
skin very quickly, making it feel perpetually cool when all but the
part that is touching you, is at room temperature. Most other
ceramics are pretty good insulators, so they feel warm and cozy as
their surface warms quickly to your skin temperature.

Another fun ceramic is the foamed stuff used for the space shuttle's
heat shield. This stuff heats up instantly bright yellow when you
play a propane torch on its surface, but take the flame off of the
tile, and you can touch it immediately, and it doesn't even feel more
than warm.

-Chuck Harris

Bruce Griffiths wrote:
I have some pink tinted alumina TO3 insulators as well as some blue
tinted beryllia ones from the 1970's.
The beryllia ones are much colder to the touch than the alumina ones.

Bruce

On 03 July 2020 at 02:19 stevenhorii <sonodocsch@...> wrote:


Beryllium and compounds have an unusual toxicity profile. Beryllium is
not
directly toxic as, say, arsenic is. However, how it harms you is to
cause
an intense allergic reaction. In the lungs, this results in fibrosis
from
the inflammation and severely affects lung function. Chuck is correct in
that most companies tinted BeO parts pink but I have certainly seen
non-tinted parts. I once found some long white pipes in a surplus yard.
Though they were not pink, they had a warning label on them. I alerted
the
owner to this and he said he’d be careful, but he was somewhat pleased
because beryllia scraps out at a higher price than alumina.

Chuck is also correct in that beryllium and its compounds are safe if
you
don’t create dust or fumes from them (no grinding or welding). Slivers
of
beryllium can cause an allergic reaction in your skin around the sliver.
You should be safe using the heatsink pad as intended but it does need
heatsink compound to be effective.

Steve H.

On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:

It has been reported that Tektronix used BeO ceramic all
over the place.

Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.

They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.

This particular heat sink insulator looks probable to me.

Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.

You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.

Regardless of what it is, you will need heatsink compound.

The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.

About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.

-Chuck Harris

John Gord via groups.io wrote:
Toby,

If it is a hard, brittle ceramic-like slab, it is probably alumina
(aluminum oxide). It is a good electrical insulator and a reasonably
good
thermal conductor. Beryllium oxide looks similar, but is unlikely here
because of its hazards.

--John Gord

On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:


Hi,

In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).

What is this material?
https://groups.io/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0

Should it be used with thermal paste or not?

Thanks
--Toby









teamlarryohio
 

Page 5-48 of a widely accessible version of the yellow book says 342-0082-00 is alumina. Were it me, I's use silicone pads under all the transistors on that mounting bar. They're series pass elements, so C is no big deal.

Greg Muir
 

Bergquist (now Henkel/Bergquist) manufactures an array of thermal management products. One of these, “Silpads” is a product I have been using for replacement purposes. It is a flexible, rubbery material that many OEM manufacturers use instead of mica.

The neat thing about this product is that you don’t need to apply any thermal compound. And it can be purchased from many distributors in the common shapes for transistor heatsinking, etc.

As for your application, you might try contacting the manufacturer to see if you might be able to obtain a small sample of a sheet to cut up and fit in the unit.

https://www.henkel-adhesives.com/us/en/products/thermal-management-materials.html

Greg

stevenhorii
 

I found these at DigiKey:

https://www.digikey.com/products/en?keywords=NTE%20TP0001

Note that they are an insulating pad which it sounds like what you
originally found. For boards that connect to the transistor case via a pad
on the board, you would need a conductive pad. I have no financial
connection to DigiKey other than being a customer. They do sell in small
quantities.

I think that DigiKey also sells the Bergquist-Henkel (I searched under
Bergquist) versions of these, both the insulating and conductive ones, but
it's hard to find them without a product number.

If the transistor is not in a TO-3 case, if you can figure out the case
type, search "heat sink pad XXX transistor case" and you will likely find
links to products.

Steve H

On Thu, Jul 2, 2020 at 12:20 PM Greg Muir via groups.io <big_sky_explorer=
yahoo.com@groups.io> wrote:

Bergquist (now Henkel/Bergquist) manufactures an array of thermal
management products. One of these, “Silpads” is a product I have been
using for replacement purposes. It is a flexible, rubbery material that
many OEM manufacturers use instead of mica.

The neat thing about this product is that you don’t need to apply any
thermal compound. And it can be purchased from many distributors in the
common shapes for transistor heatsinking, etc.

As for your application, you might try contacting the manufacturer to see
if you might be able to obtain a small sample of a sheet to cut up and fit
in the unit.


https://www.henkel-adhesives.com/us/en/products/thermal-management-materials.html

Greg



Greg Muir
 

Steve,

I guess in all the years I have never seen a semiconductor mounted via a conductive pad when connection to the thermal surface is required or desired. Usually the device is directly mounted to the cooling surface especially if a low resistance path is required. There have been some applications I have dealt with where the entire heat conducting surface (heat sink) is insulated above the chassis when the attached semiconductor is above ground potential and mounted without any insulating pad. This is usually done when other devices are attached to the same heat sink and need to “talk” to each other electrically.

Greg