ASTM D5470-17

5.1 This standard measures the steady state thermal impedance of electrical insulating materials used to enhance heat transfer in electrical and electronic applications. This standard is especially useful for measuring thermal transmission properties of specimens that are either too thin or have insufficient mechanical stability to allow placement of temperature sensors in the specimen as in Test Method E1225.

5.2 This standard imposes an idealized heat flow pattern and specifies an average specimen test temperature. The thermal impedances thus measured cannot be directly applied to most practical applications where these required uniform, parallel heat conduction conditions do not exist.

5.3 This standard is useful for measuring the thermal impedance of the following material types.

5.4 The apparent thermal conductivity of a specimen is able to be calculated from the measured thermal impedance and measured specimen thickness if the interfacial thermal resistance is insignificantly small (nominally less than 1 %) compared to the thermal resistance of the specimen.

1.1 This standard covers a test method for measurement of thermal impedance and calculation of an apparent thermal conductivity for thermally conductive electrical insulation materials ranging from liquid compounds to hard solid materials.

1.2 The term “thermal conductivity” applies only to homogeneous materials. Thermally conductive electrical insulating materials are usually heterogeneous and to avoid confusion this test method uses “apparent thermal conductivity” for determining thermal transmission properties of both homogeneous and heterogeneous materials.

1.3 The values stated in SI units are to be regarded as standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.