Measurement according to ASTM D 5470-17
I determine comparative test data under identical conditions, whereby all interfering factors (such as die distortions or non-coplanar contact surfaces) can be excluded. For me, ASTM D 5470-17 is the primary test method 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 to be determined under the following conditions:
– Controlled surface conditions
– Unidirectional heat flow conditions
– Parallel contact surfaces
– Precisely known clamping forces
And this is exactly where my 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. I measure the pastes at an average paste temperature of 60 degrees.
As this all seems a bit complex to outsiders, I have placed the individual assemblies against the function diagram so that you know where and how the measurements already explained take place. I have already explained in detail what happens in the background and how the whole thing works in the linked basic article. I don’t need to repeat all that again.
I will illustrate this once again in the already familiar diagram so that you can better visualize the meaning of these values to be determined. We can see that the effective thermal resistance affects both the material and the two contact surfaces. Yes, there are very sophisticated methods, including pulsed lasers, which can also evaluate the pure bulk value very accurately, but in practice we ALWAYS have contact surfaces. I use reference bodies with a standardized (low) roughness for the measurements so that I can also draw conclusions from these in practice. I then end up with two values, the effective thermal conductivity and a value averaged over all measuring points of the different layer thicknesses BLT minus the extrapolated contact resistance.
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 will leave the theory at that, because we are waiting for the measurements.
TIMA_5-23_datasheet-3
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