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Thermal Paste

stackowax

stackowax

pfm Member
I'm trying to find some thermal paste locally (I'm in the US) to put between the case and the heat sinks on the amp and regulator modules on my NAP250. Looks like the only thing available is stuff intended for use on CPUs, for example this. Is this okay to use or should order something different on-line?
 
That will be fine but the usual would be the normal white stuff, Dow Corning about the most common brand, which you will get from Mouser or Digikey over there.
 
Paste works well for improving already close contact. It is not a gap filler, for which you should use the silicone gap filler pads
 
davidsrsb said:
Paste works well for improving already close contact. It is not a gap filler, for which you should use the silicone gap filler pads
Click to expand...


Rather than start a new thread with the same title, I'll jump in here with my own question if thats ok.

I've got a number of Quad 405's which I'm slowly working through and servicing. Every time I unscrew the amp cards from the main body, I get thermal paste everywhere, and I can't stand the stuff! I've heard about these pads, but am not sure whether I can use them for this situation, or how to choose them from Farnell, because there are so many things that seem the same. (...I long for the days when you could walk in to a shop and talk to someone...)

Can I use a pad here?

Does it have to cover the entire surface?

How thick should it be?


The red arrows point to the bit I'm talking about... Thanks!

IMG-0072-arroes.jpg
 
You can easily get rid of this extra paste with an earpick (Q-tip) after tightening the screws.
I usually prefer to use thermal paste on amps that came with it originally as it seems to me the heat transfers with better efficiency than with a silicone pad. Especially true if the amplifier doesn’t have any thermal switch bolted to the heat sink.
 
That one looks like a job for paste as surfaces should be true and the thermal resistance is better than a pad.
Use as little as possible paste smeared over the surface. Too much and you will get trouble when the oil dries out and the powder then falls out. You may even get warping when you torque up the screws.
The clean alternative here would be the graphite sheets, but they are EXPENSIVE.
 
davidsrsb said:
That one looks like a job for paste as surfaces should be true and the thermal resistance is better than a pad.
Click to expand...
Did you mean thermal conductivity instead of resistance?

davidsrsb said:
Use as little as possible paste smeared over the surface. Too much and you will get trouble when the oil dries out and the powder then falls out.
Click to expand...
How often should thermal paste be changed, if at all, due to drying out?
 
Resistance is just the reciprocal of conductivity. Paste adds thermal resistance, but you hope that this is better than the resistance added by the voids between the plate and the heatsink.
If you use just enough paste to fill the voids, without actually pushing the two surfaces apart, the drying out process leaves the oxide particles filling the voids and gives excellent and permanent contact.
 
davidsrsb said:
Resistance is just the reciprocal of conductivity. Paste adds thermal resistance, but you hope that this is better than the resistance added by the voids between the plate and the heatsink.
Click to expand...
I know that, but you are suggesting in post #7 that paste is more thermally resistive than silicon pads. So did you mean what you said, or did you mean thermal paste has better conductivity than pads?
 
Unless you are overclocking your CPU to the nth degree or making a high power LED array ordinary thermal paste or thin silicone pads will both be fine - if your transistors are getting very hot in normal use you should maybe rethink the design.
 
James said:
I know that, but you are suggesting in post #7 that paste is more thermally resistive than silicon pads. So did you mean what you said, or did you mean thermal paste has better conductivity than pads?
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Pads are worse than well applied paste mainly because the pad (which is loaded with oxides like the paste) is MUCH thicker'
 
James said:
I know that, but you are suggesting in post #7 that paste is more thermally resistive than silicon pads. So did you mean what you said, or did you mean thermal paste has better conductivity than pads?
Click to expand...

Did you mean silicon pads?
 
James said:
I know that, but you are suggesting in post #7 that paste is more thermally resistive than silicon pads. So did you mean what you said, or did you mean thermal paste has better conductivity than pads?
Click to expand...
He said that the thermal resistance of paste is better, i.e. lower, than that of pads.
 
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