Fine ceramics (advanced ceramics, advanced technical ceramics) --Test method for thermal property measurements of metalized ceramic substrates — Part 1: Evaluation of thermal resistance for use in power modules

This document specifies a method for measuring the thermal resistance between a heater chip and a cold plate with the heater chip mounted on a metalized ceramic substrate, imitating a silicon carbide (SiC) high-output power module. This measurement represents an index of the heat dissipation characteristics of a metallized ceramic substrate used in a high-output power module.

Céramiques techniques — Méthode d'essai pour les mesures des propriétés thermiques des substrats céramiques métallisés — Partie 1: Évaluation de la résistance thermique pour utilisation dans les modules d'alimentation

General Information

Status
Published
Publication Date
11-Jan-2023
Current Stage
6060 - International Standard published
Due Date
02-Apr-2023
Completion Date
12-Jan-2023
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ISO 4825-1:2023 - Fine ceramics (advanced ceramics, advanced technical ceramics) --Test method for thermal property measurements of metalized ceramic substrates — Part 1: Evaluation of thermal resistance for use in power modules Released:12. 01. 2023
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INTERNATIONAL ISO
STANDARD 4825-1
First edition
2023-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Test method for thermal property
measurements of metalized ceramic
substrates —
Part 1:
Evaluation of thermal resistance for
use in power modules
Céramiques techniques — Méthode d'essai pour les mesures des
propriétés thermiques des substrats céramiques métallisés —
Partie 1: Évaluation de la résistance thermique pour utilisation dans
les modules d'alimentation
Reference number
ISO 4825-1:2023(E)
© ISO 2023
---------------------- Page: 1 ----------------------
ISO 4825-1:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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© ISO 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4825-1:2023(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Apparatus .................................................................................................................................................................................................................... 2

6 Procedure ....................................................................................................................................................................................................................5

6.1 Set-up............................................................................................................................................................................................................... 5

6.2 Test environments ............................................................................................................................................................................... 7

6.3 Measurement ........................................................................................................................................................................................... 7

7 Calculation .................................................................................................................................................................................................................. 8

8 Test report .................................................................................................................................................................................................................. 8

Annex A (informative) Example of set-up apparatus ......................................................................................................................... 9

Annex B (informative) Interlaboratory evaluation of thermal resistance measurements ...................10

Bibliography .............................................................................................................................................................................................................................12

iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 4825-1:2023(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
A list of all parts in the ISO 4825 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 4825-1:2023(E)
Introduction

Electrical energy is predicted to become an increasingly major modality of energy usage in the future,

and power conversion technologies play a crucial role in its generation, transmission, storage and

use. Against this backdrop, power modules that use semiconductor devices to provide high-efficiency

conversion and control of electric power are becoming an extremely important technology. While

silicon has long been used as the primary material for power semiconductor devices, wide bandgap

semiconductors using SiC, GaN and other such materials as next-generation power semiconductors

are drawing increasing expectations for their prospects of greater energy conservation, higher output

and high-speed operation. Power modules using next-generation power semiconductors of this type

are also anticipated to provide higher output and higher energy density, and likewise to capitalize

on the characteristics of these materials for high-temperature operation (in the near future, junction

temperatures are anticipated to reach 250 °C), thus heat-dissipating technologies are becoming more

important than ever before.

In high-output power modules, an insulating substrate serving as an electrical insulator is one of the

most important component materials. As power semiconductor devices increase in power output and

energy density, the amount and density of heat dissipated by these devices are also increasing, creating

a demand for higher thermal conductivity in substrate. For this reason, ceramics are generally used as

insulating substrates because of their high thermal conductivity. In addition, to minimize interfacial

thermal resistance between constituent materials, metallic conductor circuit layers are also joined

to ceramic substrates at high temperature. Heat-dissipating structures of this nature are termed

metallized ceramic substrates.

Techniques are available to measure the thermal conductivity of the individual materials comprising

metallized ceramic substrates; however, there are no established methods to evaluate the thermal

characteristics of metallized ceramic substrates per se, or the thermal characteristics of power

semiconductor devices in mounted form, which are key issues in the design of power modules with a

high heat-dissipating efficiency.

This document provides a technique for bonding a metallized ceramic substrate equipped with a heater

chip to a cold plate and for using the amount of heat dissipated by the heater chip and the temperature

differential between the heater chip and the cold plate to measure the thermal resistance of a system

including a metallized ceramic substrate. Manufacturers of ceramic elements, modules and other such

devices can use this standard to evaluate the heat-dissipating characteristics of metallized ceramic

substrates under common conditions.

The International Organization for Standardization (ISO) draws attention to the fact that it is claimed

that compliance with this document may involve the use of a patent.

ISO takes no position concerning the evidence, validity and scope of this patent right.

The holder of this patent right has assured ISO that he/she is willing to negotiate licences under

reasonable and non-discriminatory terms and conditions with applicants throughout the world. In

this respect, the statement of the holder of this patent right is registered with ISO. Information may be

obtained from the patent database available at www.iso.org/patents.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights other than those in the patent database. ISO shall not be held responsible for identifying

any or all such patent rights.
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 4825-1:2023(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for thermal property
measurements of metalized ceramic substrates —
Part 1:
Evaluation of thermal resistance for use in power modules
1 Scope

This document specifies a method for measuring the thermal resistance between a heater chip and a

cold plate with the heater chip mounted on a metalized ceramic substrate, imitating a silicon carbide

(SiC) high-output power module. This measurement represents an index of the heat dissipation

characteristics of a metallized ceramic substrate used in a high-output power module.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
IEC 60584-1, Thermocouples — Part 1: EMF specifications and tolerances
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
metalized ceramic substrate
component in which metallic circuit layers are joined to a ceramic substrate
3.2
thermal resistance

thermal property representing resistance to heat flow from a higher temperature area to a lower

temperature area in a structure

Note 1 to entry: In this document thermal resistance is expressed as the temperature difference in the structure

across a thickness when a unit of heat energy flows through it in unit time. The SI unit of thermal resistance is

K/W.

[SOURCE: IEC 60747-15:2010, 3.1, modified — Definition revised and note to entry added.]

© ISO 2023 – All rights reserved
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ISO 4825-1:2023(E)
3.3
thermal conductivity

quotient of the amount of heat flow per unit of time through a unit of surface area perpendicular to

the heat flow in a solid material, divided by the temperature difference per unit length (temperature

gradient)
Note 1 to entry: The SI unit of thermal conductivity is W/(m·K).
3.4
thermal interface material
TIM

material which fills small gaps or irregularities between components and has the function of efficiently

transferring heat produced by a device to a heat-dissipating component
EXAMPLE Thermally conductive greases, silicone sheets, graphite sheets.
4 Principle

The thermal resistance between a heater chip and a cold plate in a direction perpendicular to the

substrate is calculated by dividing the temperature difference between the heater chip and the cold

plate by the amount of heat radiated from the heater chip in a structure where a metalized ceramic

substrate bearing the heater chip is bonded to the cold plate. The cold plate is temperature-controlled

by a chiller. This calculation method minimizes the error in thermal resistance value that develops

as the aforementioned temperature difference increases. An interlaboratory comparison study

(interlaboratory test) project on this method is described in Annex B.
5 Apparatus

Figure 1 presents a schematic of the test apparatus, which is composed of the following main elements.

Note See Annex A for an example of a detailed set-up for thermal resistance measurement.

© ISO 2023 – All rights reserved
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ISO 4825-1:2023(E)
Key
1 metalized ceramic substrate 7 thermocouple
2 heater chip 8 temperature sensor
3 cold plate 9 supply of electricity
4 chiller 10 recording voltage and electric current
5 power supply 11 turning on/off power
6 controller and recorder
Figure 1 — Illustration of thermal resistance measurement apparatus

5.1 Metalized ceramic substrate. Unless otherwise specified, use a metalized ceramic substrate

with a configuration as shown in Figure 2. The metallic pattern on the front of the metallized ceramic

substrate shall include an installation area for bonding the heater chip and at least four electrode pads

electrically insulated from this area. The entire back of the metallized ceramic substrate shall comprise

a metal layer. The thickness of the metallized ceramic substrate and the metal layer are not stipulated

specifically.
© ISO 2023 – All rights reserved
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ISO 4825-1:2023(E)
Dimensions in millimetres
a) Schematic from the top b) Schematic from the back
c) Schematic from the side
Key
1 electrode pad (metal) 4 ceramic substrate
2 metal layer (front) 5 adhesion location for heater chip
3 metal layer (back)
Figure 2 — Configuration of metalized cera
...

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