ASTM D5470-17

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5470 − 12 D5470 − 17
Standard Test Method for
Thermal Transmission Properties of Thermally Conductive
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Electrical Insulation Materials
This standard is issued under the fixed designation D5470; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
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 safety, health, and healthenvironmental 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.
2. Referenced Documents
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2.1 ASTM Standards:
D374 Test Methods for Thickness of Solid Electrical Insulation (Metric) D0374_D0374M
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1225 Test Method for Thermal Conductivity of Solids Using the Guarded-Comparative-Longitudinal Heat Flow Technique
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 apparent thermal conductivity (λ), n—the time rate of heat flow, under steady conditions, through unit area of a
heterogeneous material, per unit temperature gradient in the direction perpendicular to the area.
3.1.2 average temperature (of a surface), n—the area-weighted mean temperature.
3.1.3 composite, n—a material made up of distinct parts which contribute, either proportionally or synergistically, to the
properties of the combination.
3.1.4 homogeneous material, n—a material in which relevant properties are not a function of the position within the material.
3.1.5 thermal impedance (θ), n—the total opposition that an assembly (material, material interfaces) presents to the flow of heat.
3.1.6 thermal interfacial resistance (contact resistance), n—the temperature difference required to produce a unit of heat flux
at the contact planes between the specimen surfaces and the hot and cold surfaces in contact with the specimen under test. The
symbol for contact resistance is R .
I
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This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Products.
Current edition approved Jan. 1, 2012Nov. 1, 2017. Published February 2012November 2017. Originally approved in 1993. Last previous edition approved in 20112012
as D5470 – 11.D5470 – 12. DOI: 10.1520/D5470-12.10.1520/D5470-17.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
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D5470 − 17
3.1.7 thermal resistivity, n—the reciprocal of thermal conductivity. Under steady-state conditions, the temperature gradient, in
the direction perpendicular to the isothermal surface per unit of heat flux.
3.2 Symbols Used in This Standard:
3.2.1 λ = apparent thermal conductivity, W/m·K.
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3.2.2 A = area of a specimen, m .
3.2.3 d = t
...