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Old 23rd Oct 2020, 5:26 pm   #21
kalee20
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Default Re: Heatsink compound - refresh or not?

I'd say, if in place, leave it! Unless replacing the transistor anyway.

It's there to fill voids. And the compound is powdered zinc or aluminium oxide, good as a thermal conductor, and which needs an additional substance to make a paste but which can, in principle, slowly evaporate or otherwise migrate away leaving the active particles trapped where they need to be.

Quote:
Originally Posted by Peter F4VSA View Post
I would very much hope that no heat sink compound would ever contain beryllium oxide, far too dangerous.
Me too! And it's not cheap either. So only used where its performance could be justified, which is in a low-capacitance or high-voltage insulator, which needs to be thick for those reasons, and hence where excellent thermal conductivity is important.
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Old 23rd Oct 2020, 5:44 pm   #22
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Default Re: Heatsink compound - refresh or not?

I 100% agree with this ^^^ Kalee20
No point disturbing existing circuitry unless it it needs to be disturbed for whatever reason.
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Old 23rd Oct 2020, 10:50 pm   #23
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Quote:
Originally Posted by MrBungle View Post
Can recommend Arctic Silver MX4 which is about £5 for a reasonable syringe full on amazon. Designed for CPUs but works very very well compared to much more expensive stuff.
Arctic silver could possibly be problematic, as it may be somewhat conductive. I only use it when there's not insulation between the device and the heat sink. I use the regular white alumina compound when insulation is needed.
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Old 23rd Oct 2020, 11:01 pm   #24
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Default Re: Heatsink compound - refresh or not?

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Originally Posted by MrBungle View Post
Too late on the audiophile heatsink compound - someone thought of it already!

https://www.overclockers.co.uk/therm...th-02j-tg.html
That isn't audiophile stuff, it's for CPU cooling with a large temperature range. It seems at least somewhat rationally justified to me.
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Old 23rd Oct 2020, 11:04 pm   #25
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Default Re: Heatsink compound - refresh or not?

Quote:
Originally Posted by Philips210 View Post
That was my understanding too, I always thought it was mostly zinc oxide.
BeO heat transfer pads do seem to have been used fairly widely though. They have the appearance of ceramic. I have a few of the white and also pink coloured pads salvaged from old equipment, safely stored in polythene bags.
From your description they look exactly like their alumina counterparts, at least the white ones. That sounds quite dangerous. What equipment were they from?
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Old 23rd Oct 2020, 11:16 pm   #26
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Default Re: Heatsink compound - refresh or not?

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Originally Posted by Maarten View Post
Arctic silver could possibly be problematic, as it may be somewhat conductive. I only use it when there's not insulation between the device and the heat sink. I use the regular white alumina compound when insulation is needed.
It's not conductive at all. Have independently confirmed it up to around 400V.
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Old 24th Oct 2020, 10:57 am   #27
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Quote:
Originally Posted by Maarten View Post
From your description they look exactly like their alumina counterparts, at least the white ones. That sounds quite dangerous. What equipment were they from?
Hi.

Perhaps they're not made from BeO then. Please see attached pics.

I think the TO-220 thin ones came from a Philips VR2020 PSU.
The thick TO-220 spacers were possibly from miscellaneous parts obtained from Sendz components back in the 1980s.
The pink TO-220 spacer came from I believe an ITT CVC40 CTV. On that chassis, the line output and chopper transistors plug in and I seem to remember the thick pink heat transfer spacer. Are they safe to use?

Regards,
Symon
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Old 24th Oct 2020, 1:14 pm   #28
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Default Re: Heatsink compound - refresh or not?

I can't find my reference books from my Army days with reference to this but there was quite hefty warnings about BeO heat sink compounds used in some radio equipment that I worked on.
I have it in my mind that the relevant radios were from the USA.
One that does come to mind is a GRC-106 transmitter/ receiver and RTTY modem.
I am talking about 1960s sort of stuff.

"Let sleeping dogs lie".
My thoughts are that heat sink compound is used to fill minor voids between a component and the heat sink.
The original application of heat sink compound should have been enough to do the job. If I have doubts about that then I will replace the compound. Especially when other components within the same device are showing heat stress or failure. As stated by other posters it is the solid component that does the job and not the grease part.
One other thought is that to get to the stage where it is possible to replace the heat sink compound yo9u have to sometimes disturb quite a bit of circuitry and this, on old stuff, will generate it's own dramas.

"Been there, done that".
When the lead snaps off the un-obtanium transistor because I wanted to replace the compound.
"Oh why on earth did I want to do that for"!!!!!!!! Much swearing.

Just my thoughts.
Cheers,
Robert.

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Old 24th Oct 2020, 1:51 pm   #29
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Originally Posted by Philips210 View Post
The pink TO-220 spacer
Hi.

Should read pink TO-3 spacer, sorry.

Regards,
Symon
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Old 24th Oct 2020, 7:03 pm   #30
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Default Re: Heatsink compound - refresh or not?

I don't know for sure out what material the pink ones are made, but BeO wasn't used in simple consumer electronics due to high cost, being hazardous and not needed for the purpose. Philips used those ceramic plates in a lot of consumer electronics and they're almost certainly alumina.
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Old 24th Oct 2020, 7:20 pm   #31
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Hi.

That's more reassuring. Yes, I've encountered many of those thin white heat tranfer plates in various Philips TVs etc.

It does seem reasonable, for run-of-the mill consumer equipment, to not generally use pads made from beryllium oxide, not just on safety grounds but cost as you point out.

Regarding the pink TO-3 pad, probably from an ITT CVC40 CTV, then best to err on the side of caution and not to use it. It would be good to find out if it is BeO though. Thanks for your reply.

Regards,
Symon
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Old 24th Oct 2020, 8:04 pm   #32
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Default Re: Heatsink compound - refresh or not?

Years ago when I was building and repairing computers, replacing heat sink compound was often the repair.
About a month ago, my wife's laptop started playing up, slowing, restarting etc.
I added some RAM, fitted an SSD hard drive, but the fault persisted.
Eventually, I removed the micom's heatsink, cleaned it and the micom, added a small quantity of HSC, saved from my pre-retirement time and replaced the heat sink.
It has not missed a beat since.
If I have a transistor out for any reason, and it has old, dry HSC, I replace on sight.
Les.
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Old 24th Oct 2020, 11:04 pm   #33
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Default Re: Heatsink compound - refresh or not?

Beryllium oxide heatsink insulating washers are perfectly safe to use, and perform well. The problems occur if you start grinding them up or otherwise creating particles. Beryllium and human body chemistry are just incompatible. So, disposing of them is a responsibility, going into the crusher is just a no-no.

They're unlikely to be used except in specialised equipment owing to cost. AFAIK the only electrical insulator that is a better heat conductor than beryllia, is diamond - which has no adverse effects on health. Down side is it's difficult to saw into slabs - and it's even more expensive...
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Old 25th Oct 2020, 1:04 pm   #34
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Quote:
Originally Posted by kalee20 View Post
Beryllium and human body chemistry are just incompatible. So, disposing of them is a responsibility, going into the crusher is just a no-no.
Hi.

I quite agree. I wouldn't dream of just putting them out for the dustmen. I always take any hazardous/potentially hazardous components/chemicals to the recycling centre where they have a facility to accept chemicals etc. As is obvious, any such items should be clearly labelled.
I also take old faulty components, other electronic scrap, and also batteries for recycling rather than placing in the bin.

Regards,
Symon
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Old 25th Oct 2020, 3:51 pm   #35
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Default Re: Heatsink compound - refresh or not?

You might find that you need specialist handlers for BeO. The local recycling centre here refuses a lot of stuff.
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Old 25th Oct 2020, 7:17 pm   #36
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Default Re: Heatsink compound - refresh or not?

I searched for pink alumina and found this: https://alchemymineral.com/pink-aluminum-oxide

The pink stuff might contain chrome, which is also unhealthy when you chop it up and breathe it in, but significantly less unhealthy than berillium.

I've seen similar stuff used in the antenna on household magnetron tubes as well.
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Old 25th Oct 2020, 7:21 pm   #37
Maarten
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Default Re: Heatsink compound - refresh or not?

Quote:
Originally Posted by MotorBikeLes View Post
Years ago when I was building and repairing computers, replacing heat sink compound was often the repair.
About a month ago, my wife's laptop started playing up, slowing, restarting etc.
I added some RAM, fitted an SSD hard drive, but the fault persisted.
Eventually, I removed the micom's heatsink, cleaned it and the micom, added a small quantity of HSC, saved from my pre-retirement time and replaced the heat sink.
It has not missed a beat since.
If I have a transistor out for any reason, and it has old, dry HSC, I replace on sight.
Les.
Computers often use stuff that melts in place when it heats up. I think it deteriorates chemically or physically without leaving the actively heat conducting materials in place as would be the case with normal thermal paste.
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Old 25th Oct 2020, 7:54 pm   #38
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Hi Maarten.

Thanks for the link.

I've been trying to find any information on pink insulating pads and came across this https://www.silicon-ark.co.uk/discou...ulator-alumina which appears to be the same as mine. So pink alumina exists after all, you learn something everyday!
I was aware about the pink insulating material on magnetrons which I believe is beryllium oxide.

It would seem fairly likely then, that ITT would not use beryllium oxide in their late 1970s television receivers. So I think I'll use the T0-3 pad for a project.

Regards,
Symon
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Old 26th Oct 2020, 11:21 pm   #39
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Default Re: Heatsink compound - refresh or not?

I was looking at this circuit a couple of days ago, a mid 1980s ITT Prestel decoder, you can see my hand-written annotation I made on the training course.

The big distinction of course, it referred to the BeO inside the device package.
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Old 26th Oct 2020, 11:28 pm   #40
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Default Re: Heatsink compound - refresh or not?

Quote:
Originally Posted by rambo1152 View Post
I was looking at this circuit a couple of days ago, a mid 1980s ITT Prestel decoder, you can see my hand-written annotation I made on the training course.

The big distinction of course, it referred to the BeO inside the device package.
Your annotation actually refers to barium oxide not berylium.

B
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