The effective thermal conductivity
I have written time and again that almost nothing can be recognized or compared on the basis of thermal conductivity. Anyone who believes that thermal conductivity is a constant value is very much mistaken. But I have already explained this at length in the basic article. If you have Rth, you don’t need λeff, i.e. the effective thermal conductivity, at all. And the pure specification for the idealized bulk value is so far removed from reality that you always have to wonder about these figures. The stated 17 W/(m-K) is guaranteed to have been produced in the PR department and not in the laboratory by a real measurement. Yes, it’s still better than what some “high-performance pastes” really offer, but it’s not enough for the top. Good midfield, but no more.
Apart from the fact that I also have the temperatures of the heater and the water, which are of no use to us because they always remain constant, I have my measurement setup with temperature sensors 1 to 6 (see diagram on page 2). With these values, you can now make some very interesting considerations. Let’s first take the values of T3 and T4, which show us the two temperatures at the respective contact surfaces between which the paste is located. These curves are no longer completely linear, because the interface resistance also changes a little. And we no longer calculate with 6 points, but only with 2 absolute values for the temperature difference instead of a gradient aswithTTim, whereby the sample temperature remains constant.
GPU emulation
And what is the point of all this? The behavior is similar to that of a graphics card, which has to manage without an IHS and where the delta is usually measured between the substrate and the water temperature. With a bit of good will, you can also project it onto the behavior on CPUs, because I’m testing the temperature difference on the two surfaces between which the paste is located. Let’s see what we have there:
CPU emulation
Now I compare T1 of the reference with T1 of the gaming paste A. While the heater remains constant, we already have sufficient thermal resistance in the copper reference block to simulate the CPU temperature and its differences with different pastes compared to the reference and depending on the layer thickness of the paste. It is precisely this variable evaluation that no test on a CPU can offer, because it is always individually different and therefore not really reproducible. But here in the TIMA5 test it is.
56 Antworten
Kommentar
Lade neue Kommentare
Urgestein
Mitglied
Neuling
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Urgestein
Veteran
1
Veteran
Urgestein
Alle Kommentare lesen unter igor´sLAB Community →