Thermal/silicon compound identification help...

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z1ppy
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Thermal/silicon compound identification help...

I’ve done a search, but many of the results get very technical and don’t answer my query, so apologies if it’s been covered previously (just point me in the right direction).

I’ve disassembled a friends Inton dual XML headlight, in order to fix a short on the cable just where it enter the head unit. To do this I took the head unit apart, and found it was full/filled with this stuff:

When the short has been fixed I’m looking for some replacement compound to refill the unit with… but it needs to be a similar type of compound to support the circuit board and I imagine transfer heat. The internals came out easily, not sticky and solid lump that was easy to pull apart, so there was no damage to the circuit board or connecting cables. Does anyone know of a similar compound I can use?

A friend has suggested it is some sort of silicon foam, but try searching for that doesn’t give a clear answer (and lot of unrelated options).

Any help would be great, cheers

Chloe
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Hi z1ppy, generally best to only use thermal compound sparingly between more conductive materials like aluminium or copper.

You can try these squares:
http://www.fasttech.com/products/0/10003973/1285500-thermal-conduction-s...

z1ppy
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Cheers for the link, interesting stuff, though what I think I want/need is the ‘liquid’ version of that (edit: reading the discussion link, it’s suggested it more clay like, but there no reply as to whether it sets – maybe it is what I need)… and given me new avenue to search

I understand your warning, but maybe I’ve overstated the thermal transfer requirement, maybe what I need is a “heat resistant” silicon that sets solid but not so solid it can’t be peeled off for repairs.

ruffles
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I can’t for the life of me remember why, but others (presumably more knowledgeable than me) suggest a neutral cure silicone to avoid corroding electronic parts. (Has something to do with the fact that a typical silicone has acetic acid.)

I couldn’t find a specifically ‘high temperature’ silicone that’s also neutral cure, but I did find an example of a neutral cure that’s good up to 200 degrees C (http://www.americansealantsinc.com/asi-335-neutral-cure-silicone-sealant...), so they’re out there.

A bog standard neutral, like Bond-it WP70 is listed to have a service temperature up to 100 deg. C, which might be adequate.


 

Chloe
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Acetic acid can’t be good for some metals. I’ve used vinegar to oxide carbon steel…

Strick9
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rojos
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Acetic acid can etch pcb.

Afaik Fujik is neutral cure silicone. I’m not sure that it would be the best stuff to use here, but it would be the cheapest I believe. Legit potting compounds can get pricey.

PilotPTK
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I would be pretty certain that the stuff you show there is Dow Corning Sylgard Q3-3600.  It's a two-part thermally conductive encapsulant, and when cured, it looks just like what you show.  It's 'flaky' to some extent - for example, if you bend it, it should 'snap'.

http://www2.dowcorning.com/DataFiles/090007c8803b9c6a.pdf

I am currently extremely busy with work. Please do not expect a response from me quickly. I will be dropping in as time permits, but the amount of time I can dedicate to responding to topics and PMs is very limited.

texaspyro
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PilotPTK wrote:

I would be pretty certain that the stuff you show there is Dow Corning Sylgard Q3-3600.

Yep, and it will cost you more than the flashlight… plus, for maximum effectiveness, you should vacuum process it to remove any air bubbles caused by mixing it.

z1ppy
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Many thanks for all the replies, sound like PilotPTK has the ‘answer’ but obviously not something I can afford.
I’m edging towards Strick9’s Loctite 5699 suggestion, as though the thermal rubber cubes Chloes suggests might be cheap and do the same job, the delivery wait time will make the repair turn-around excessive,

Cheers all, you’ve been very helpful

z1ppy
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Small update on this, well I filled it full of loctite 5699 and that was several weeks ago, and he’s used it every week since, so I rate this as a success Smile
Cheers all round

Cowboysnavy
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RMM has those thermal cubes
I potted my last mod with high temp RTV sealant “auto store”
As for taking it apart I don’t think I can but it’s very rugged

I’ve mixed silicon sealant with cornstarch before in the past to give a temporary fix
I guess it could work in a situation like this

Yes I know I’m a cheapskate