ASTM D 5470 TIM material testing

The ASTM D 54701 standard is currently being revised to cover a test method for the measurement of thermal impedance and calculation of an apparent thermal conductivity for thermal interface materials (TIM) ranging from liquid compounds to hard solids. Modifications to the procedure include the use of mechanical stops to control the specimen thickness under test and an in situ thickness measurement to monitor the specimen thickness if the thickness dimension of the specimen can change during the test. Rigid materials that will not coalesce together require the preparation of specimens of different thickness to obtain the multiple thermal impedance measurements needed to calculate the thermal conductivity. The revised method does not call out a specific clamping pressure to be used for all material types but instead specifies that the clamping pressure required is either that which is sufficient to contact the mechanical stops or to coalesce multiple layers together without damaging the test specimens. Measuring the 3 primary properties - the heat flow through the test specimen, the temperature difference across it, and the thickness of the specimen under test - is still stressed