ASTM D 5470-17
The purpose is clear: to obtain comparative test data under identical conditions while eliminating all interfering factors (such as die distortion or non-coplanar contact areas). ASTM D 5470-17 and transient methods are the primary test methods for determining thermal conductivity and thermal resistance, whereby I only use ASTM D 5470-17 and not the complementary electrical methods according to JESD 51-14. The values in a TIM provider’s data sheet should be developed using ASTM D 5470-17 to produce comparable values determined under the following conditions:
– Controlled surface conditions
– Unidirectional heat flow conditions
– Parallel contact surfaces
– Precisely known clamping forces
And this is exactly where the TIMA5 comes into its own. It is a fairly compact all-in-one tabletop device that combines the measurement setup and the required PC in one device. It is therefore a self-sufficient and, above all, automated measurement setup that I can also run in parallel to other tasks in the background. All data is saved directly to the NAS via the network, so that’s safe. The device is calibrated and has already passed the first plausibility test.
As this all seems a bit complex, I have placed the individual assemblies against the functional diagram so that you can see where and how the measurements already explained take place. We can also see T3 and T4 here, which I already referred to in the diagram on the previous page:
I’ll repeat the diagram with the transitions again now anyway, because it helps us to better visualize the meaning of this value to be determined.
I have analyzed the measurement of the DOWSIL 340 at a sample temperature of 70 °C graphically myself and you can see very clearly that the Rth remains linear, while the thermal conductivity changes logically and drops non-linearly with decreasing layer thickness. This is normal, but also shows that the Rth value is much more important than a fictitious thermal conductivity
External cooling is provided by a laboratory chiller from IKA, which can maintain the water temperature almost to the nearest decimal place and which can not only cool, but also reheat if necessary, so that the required 20 °C water temperature can always be maintained. The hoses were connected using Festo couplings and special hoses.
I’ll leave the theory at that, because it’s already been four long pages of heavy fare. So it’s time to gather ourselves and turn to the first results tomorrow, and I can already spoil it: it’s going to be very interesting! There’ll be a few more nice shockers and insights in part 2 tomorrow, I promise!
TIMA_5-23_datasheet-3
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