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Thermal paste application?

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gyrene

gyrene

No Marconi:Gomer MacGyver
When installing transistors to the heat sink should I put thermal paste on both sides of the mica card?
So it would be transistor with thermal paste on the rear attached to the mica card which itself has thermal paste on its rear and then all attached to the heat sink?
Seems like a lot of paste.
 
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From what i've seen taking some units apart, the older stuff just put paste on the back of the mica card, between it and the heatsink. I would not think there is a reason to double up, as the mica material is to prevent electrical contact, and passes heat with no problems. In practical terms, for electrical contact, the mica is there, in heat terms, it's not.

Maybe someone else has more expieriance, but this is what i've run into.
 
You need to apply paste between every surface, as none of them are perfectly flat on a microscopic level. The paste will fill those spaces and conduct heat better than air.

But thermal paste is not that great of a heat conductor by itself, so this is a case of less is more, i.e. don't apply too much!

Good luck!

az
 
Both sides, afaik.

Also, it is my understanding this is one thing of which more isn't necessarily better...enough is just right, too much isn't good.
 
Both sides of the mica. The problem is the inevitable air space between the mica washer and the metal on either side. That air space is what you want to exclude with the zinc-oxide paste.

You can get thermally conductive rubber sheet now that is more efective than mica + zinc oxide
 
steerpike2 said:
Both sides of the mica. The problem is the inevitable air space between the mica washer and the metal on either side. That air space is what you want to exclude with the zinc-oxide paste.

You can get thermally conductive rubber sheet now that is more efective than mica + zinc oxide
Click to expand...

Are you refering to the grey Sil-pads? If so, those are nowhere near mica+paste, but much more convenient. Maybe you're talking about some other, newer, material of which I'm not aware, but of which I'd like to be if it's the case! :D

az
 
I have seen talk of aluminum oxide or beryllium oxide transistor insulators that I believe profess top thermal conductivity, but I don't know the details.
 
audiozaz said:
Are you refering to the grey Sil-pads? If so, those are nowhere near mica+paste, but much more convenient. Maybe you're talking about some other, newer, material of which I'm not aware, but of which I'd like to be if it's the case! :D

az
Click to expand...

Concur..Light reading on heatsinks-thermal compound and various insulators to include mica/Sil-pad & aluminum-beryllium oxide(ceramics)

http://www.sound.westhost.com/heatsinks.htm#8
 
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whoaru99 said:
Both sides, afaik.

Also, it is my understanding this is one thing of which more isn't necessarily better...enough is just right, too much isn't good.
Click to expand...

Yeah, much like a CPU, a small, well-spread amount is much better than a thick layer. From what i've read, a small dot of paste, spread with the side of a card (or other plastic straight-edge) to a very thin layer is all you need.

As for my point earlier, I guess it would be better, certainly to do both sides (you could get by on one). The one-side thing may just be older units, as i'm basing my assumptions on a pioneer sx-1000tw I took apart. As a worthwhile mention, my father works as a electrical engineer in a printer company, as such we have many spare boards and samples laying around. The boards with heatsinks do have paste between everything. Maybe just a change in times :dunno:
 
audiozaz said:
Are you refering to the grey Sil-pads?... Maybe you're talking about some other, newer, material of which I'm not aware, but of which I'd like to be if it's the case!
Click to expand...

I haven't bought any yet so I can't verify performance; the ones I've seen claiming better performance were a dark purple colour, quite soft and almost jelly-like. They feel noticably cool to the touch, evidently because they conduct the heat away from your fingers.

whoaru99 said:
I have seen talk of aluminum oxide or beryllium oxide transistor insulators
Click to expand...

Beryllium oxide is a fantastic thermal conductor, but it is exceptionally poisonous, and in certain places impossible to buy without a permit.
 
Thin layer, both sides, like gasket sealer if that analogy means anything to ya. I wipe the insulators on a towel after application to reduce the squeeze out. I like the OEM look.
 
Well it won't matter today anyway...I had two NOS transistors and they were looking real nice.Came in last night.Got it all set up and don't you know it...fragile legs!
Each Q busted a leg.
And "NO" I didn't try to muscle them into place...nice and gentle it was...well thats what happens when a Q is 30+ years old right?
Ohhhhhh...well.Good thing this is a FUN hobby,right?
 
gyrene said:
Well it won't matter today anyway...I had two NOS transistors and they were looking real nice.Came in last night.Got it all set up and don't you know it...fragile legs!
Each Q busted a leg.
And "NO" I didn't try to muscle them into place...nice and gentle it was...well thats what happens when a Q is 30+ years old right?
Ohhhhhh...well.Good thing this is a FUN hobby,right?
Click to expand...

Sorry to hear that. It should not happen, I've never had it happen even with stuff equally old. What transistors are they?
 
NEC 2sb618's
What can I say.One showed up as a two legged version with the missing limb in the plastic bag and the other one was fragile enough to fall off in my hand.
And you know how gentle "gyrene"s can be...right?
Its alright.I needed a break anyway.Put a small order in already and next week I know what I'm doing.
 
gyrene said:
NEC 2sb618's
What can I say.One showed up as a two legged version with the missing limb in the plastic bag and the other one was fragile enough to fall off in my hand.
And you know how gentle "gyrene"s can be...right?
Its alright.I needed a break anyway.Put a small order in already and next week I know what I'm doing.
Click to expand...

Can you say Go-rilla..:D
 
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