ASTM D5470-12

Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials

SIGNIFICANCE AND USE
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.
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.
This standard is useful for measuring the thermal impedance of the following material types.
Type I—Viscous liquids that exhibit unlimited deformation when a stress is applied. These include liquid compounds such as greases, pastes, and phase change materials. These materials exhibit no evidence of elastic behavior or the tendency to return to initial shape after deflection stresses are removed.
Type II—Viscoelastic solids where stresses of deformation are ultimately balanced by internal material stresses thus limiting further deformation. Examples include gels, soft, and hard rubbers. These materials exhibit linear elastic properties with significant deflection relative to material thickness.
Type III—Elastic solids which exhibit negligible deflection. Examples include ceramics, metals, and some types of plastics.
The apparent thermal conductivity of a specimen can 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.
The apparent thermal conductivity of a sample material can be accurately determined by excluding the interfacial thermal resistance. This is accomplished by measuring the thermal impedance of di...
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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Dec-2011
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.01 - Electrical Insulating Products

Relations

• Replaces: ASTM D5470-06(2011) - Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials
• Effective Date: 01-Jan-2012
• Replaced By: ASTM D5470-17 - Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials
• Effective Date: 01-Nov-2017
• Referred By: ASTM D6343-14(2018) - Standard Test Methods for Thin Thermally Conductive Solid Materials for Electrical Insulation and Dielectric Applications
• Effective Date: 01-Jan-2012

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D5470 − 12
Standard Test Method for
Thermal Transmission Properties of Thermally Conductive
1
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* 3. Terminology
1.1 This standard covers a test method for measurement of 3.1 Definitions of Terms Specific to This Standard:
thermal impedance and calculation of an apparent thermal 3.1.1 apparent thermal conductivity (λ), n—the time rate of
conductivity for thermally conductive electrical insulation heat flow, under steady conditions, through unit area of a
materials ranging from liquid compounds to hard solid mate- heterogeneous material, per unit temperature gradient in the
rials. direction perpendicular to the area.
3.1.2 average temperature (of a surface), n—the area-
1.2 The term “thermal conductivity” applies only to homo-
weighted mean temperature.
geneous materials. Thermally conductive electrical insulating
materialsareusuallyheterogeneousandtoavoidconfusionthis
3.1.3 composite, n—a material made up of distinct parts
testmethoduses“apparentthermalconductivity”fordetermin-
whichcontribute,eitherproportionallyorsynergistically,tothe
ing thermal transmission properties of both homogeneous and
properties of the combination.
heterogeneous materials.
3.1.4 homogeneous material, n—a material in which rel-
1.3 The values stated in SI units are to be regarded as
evant properties are not a function of the position within the
standard.
material.
1.4 This standard does not purport to address all of the
3.1.5 thermal impedance (θ), n—the total opposition that an
safety concerns, if any, associated with its use. It is the
assembly (material, material interfaces) presents to the flow of
responsibility of the user of this standard to establish appro-
heat.
priate safety and health practices and determine the applica-
3.1.6 thermal interfacial resistance (contact resistance),
bility of regulatory limitations prior to use.
n—thetemperaturedifferencerequiredtoproduceaunitofheat
flux at the contact planes between the specimen surfaces and
2. Referenced Documents
the hot and cold surfaces in contact with the specimen under
2
2.1 ASTM Standards:
test. The symbol for contact resistance is R .
I
D374 Test Methods for Thickness of Solid Electrical Insu-
3.1.7 thermal resistivity, n—the reciprocal of thermal con-
3
lation (Withdrawn 2013)
ductivity. Under steady-state conditions, the temperature
E691 Practice for Conducting an Interlaboratory Study to
gradient, in the direction perpendicular to the isothermal
Determine the Precision of a Test Method
surface per unit of heat flux.
E1225 Test Method for Thermal Conductivity of Solids
3.2 Symbols Used in This Standard:
Using the Guarded-Comparative-Longitudinal Heat Flow
3.2.1 λ = apparent thermal conductivity, W/m·K.
Technique
2
3.2.2 A = area of a specimen, m .
3.2.3 d = thickness of specimen, m.
1
This test method is under the jurisdiction of ASTM Committee D09 on
3.2.4 Q = time rate of heat flow, W or J/s.
Electrical and Electronic Insulating Materials and is the direct responsibility of
3.2.5 q = heat flux, or time rate of heat flow per unit area,
Subcommittee D09.01 on Electrical Insulating Products.
2
W/m .
Current edition approved Jan. 1, 2012. Published February 2012. Originally
approved in 1993. Last previous edition approved in 2011 as D5470 – 11. DOI:
3.2.6 θ = thermal impedance, temperature difference per
10.1520/D5470-12. 2
unit of heat flux, (K·m )/W.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on 4. Summary of Test Method
the ASTM website.
3
4.1 This standard is based on idealized heat conduction
The last approved version of this historical standard is referenced on
www.astm.org. between two parallel, isothermal surfaces separated by a test
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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D5470 − 12
specimen of uniform thickness. The thermal gradient imposed mechanical stability to allow placement of temperature sensors
on the specimen by the temperature difference between the two in the specimen as in Test Method E1225.
contacting surfaces causes the heat fl
...

This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
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.
An American National Standard
Designation:D5470–06 (Reapproved 2011) Designation:D5470–12
Standard Test Method for
Thermal Transmission Properties of Thermally Conductive
1
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 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D374 Test Methods for Thickness of Solid Electrical Insulation
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1225 Test Method for Thermal Conductivity of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow
Technique
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 apparent thermal conductivity (l), 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 (u), n—thetotaloppositionthatanassembly(material,materialinterfaces)presentstotheflowofheat.
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
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 l = apparent thermal conductivity, W/m·K.
2
3.2.2 A = area of a specimen, m .
3.2.3 d = thickness of specimen, m.
3.2.4 Q = time rate of heat flow, W or J/s.
1
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.19 on Dielectric Sheet and Roll Products.
Current edition approved AprilJan. 1, 2011.2012. Published April 2011.February 2012. Originally approved in 1993. Last previous edition approved in 20062011 as
D5470–06.D5470 – 11. DOI: 10.1520/D5470-06R11.10.1520/D5470-12.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
D5470–12
2
3.2.5 q = heat flux, or time rate of heat flow per unit area, W/m .
2
3.2.6 u = thermal impedance, temperature difference per unit of heat flux, (K·m )/W.
4. Summary of Test Method
4.1 This standard is based on idealized heat conduction between two parallel, isothermal
...