Thermal paste for output transistors?
- Thread starter Oleg LED
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Blue Shadow
Waiting for Vintage Gear from this century
Dow 340 is mentioned a bit here, but I don't think the world or your unit will come to an end for not using just the best. Any decent brand will be just fine Except those that are electrically conductive, containing silver and designed to be used in computer stuff not high fidelity gear. The one you selected will be fine when used properly.
Oleg LED
New Member
Thanks Blue Shadow. I used that silicone grease twice so far to refresh the old grease but was not sure if it is a good choice. I will probably switch to Dow 340 next time.
Never use thermal compound as it tends to dry out. Always use those silicone sheets. Last brand I got was a kind of tan color and called Kerafol/Keratherm. Available for TO-3, TO-220 and TO-247 packages. No more messy fingers, love the stuff! There are other types as well, these have different color (grey).
Tjerk, 9ZZ
Tjerk, 9ZZ
There has been some debate about the thermal properties of sil-pads, ie, they don't conduct/transfer heat as well as some would
like. I haven't done any study, yet another thing on my do list...
Lots of excellent discussion about them here
https://www.diyaudio.com/forums/solid-state/258573-transistor-insulators-7.html#post5959902
I use Thermal Interface Products. Mouser part # 567-120-SA it is fine and messy but it has been the standard for years. For a new design I use sil-pads they work fine as well. Kerafol/Keratherm are premium, little harder to find and more expensive. I do not use them because of availability, if they were more available I'd spec them.
https://www.diyaudio.com/forums/solid-state/258573-transistor-insulators-7.html#post5959902
I use Thermal Interface Products. Mouser part # 567-120-SA it is fine and messy but it has been the standard for years. For a new design I use sil-pads they work fine as well. Kerafol/Keratherm are premium, little harder to find and more expensive. I do not use them because of availability, if they were more available I'd spec them.
Depends on what you are using it on, but that Wakefield product is just fine for TO-3, TO-66, and TO-220 transistors. Sanken recommends Dowsil SC 102 (and a couple others). Note that *some* silicone based compounds can bleed and actually penetrate transistors, such as the MT-200 and others. Scroll down to the end of the "mounting" section. https://www.semicon.sanken-ele.co.jp/en/support/reliability/4-7.html#sec3
Dowsil SC 102 datasheet; https://www.dupont.com/content/dam/...iterature/Downloaded-TDS/0901b803809b781b.pdf
Blue Shadow
Waiting for Vintage Gear from this century
I bought a tube of stuff from Mouser years ago and it works fine. No reason to switch until I run out. Aavid 249G. works fine.
turboyam
The Kenwood fan!
I absolutely love Keratherm but i wouldn't try to steer away from the goo either.
Kerafol is one step tho, and no mess!
OMGCat!
Super Member
This is interesting. I had no idea that thermal compound could possibly damage the devices. Great read I’m general though.
I’ve been using a non silicone thermal compound made by Techspray. It was liberated from a job years and years ago and I still have at least half the tube remaining. Good to know that the lack of silicone is a plus.
turboyam
The Kenwood fan!
This is where i got it from DIY store. You should try that stuff Craig, i think it's really nice. I had put together a Pass F-5 class A amp, and the thermal transfer was great!. It's probably re-usable for another time i'd say, no cracking of a mica insulator, no paste, no mess.
It's not really a "plus". Some silicone-based thermal compounds do no harm whatsoever, and do not dry out for a very long time. It depends on what specific formula, or mixture is used for the base grease. Just like grease used in machinery where the oil will bleed out of certain "brands", types, and temperature ratings, but they (comparative types such as lithium) use the same base.The oils used in some bleed very little over time, where others bleed all over the place in only a few weeks. The Dowsil SC 102 resists bleeding as compared to many other types and brands and the oils won't penetrate the transistor body. Metal to metal won't be affected. TO-3 is all metal, where an MT-200 has a metal plate and part of the body material is exposed where the compound goes. The joint between the 2 dissimilar materials is a problem too.
teal'c
Nuclear Cardiac Parent
This isn't a debate thread for which paste is "best". I was merely pointing out a caveat that an actual manufacturer of silicon transistors where some compounds actually attack and permeate the transistor case material.
It's not for use with silicon. In fact, it says nothing about using it for silicon, only CPU use where the heatsink is the only thing it will touch. Plus it isn't really a long lasting paste.. A quote... "In contrast to metal and silicon thermal compound, the performance of MX-4 does not compromise over time. Once applied, you do not need to apply it a second time as it will last at least for 8 years." Though in computer "life" time, where they constantly go obsolete in as little as 4 years, and even get toasted in less time by overclockers and gamers, it wouldn't matter. Arctic has absolutely no skin in the game when it comes to transistors. They sell the stuff for computer use, not audio use. And I am sure they never even researched it anyways.
They are a one-time use only. I have removed transistors with the pads and found some were dangerously close to shorting being compressed to near translucent, and one actually did short the collector. I don't trust them for repeated thermal cycling where they can actually wear through over time.
