IEC 61189-2-809:2024

Test methods for electrical materials, circuit boards and other interconnection structures and assemblies – Part 2-809: X/Y coefficient of thermal expansion (CTE) test for thick base materials by TMA

IEC 61189-2-809:2024 defines the method to be followed for the determination of the X/Y coefficient of thermal expansion of electrical insulating materials by the use of a thermomechanical analyser (TMA).
This method is applicable to materials that are solid of the entire range of temperature used and retain sufficient hardness and rigidity over the temperature range so that irreversible indentation of the specimen by the sensing probe does not occur.

Méthodes d'essai pour les matériaux électriques, les circuits imprimées et autres structures d'interconnexion et ensembles – Partie 2-809: Essai du coefficient de dilatation thermique (CTE) X/Y pour matériaux de base épais à l'aide d'un analyseur thermomécanique (TMA)

L’IEC 61189-2-809:2024 définit la méthode à suivre en vue de déterminer le coefficient de dilatation thermique (CTE, coefficient of thermal expansion) X/Y des matériaux isolants électriques à l'aide d'un analyseur thermomécanique (TMA, thermomechanical analyser).
La présente méthode est applicable aux matériaux qui sont solides dans toute la plage de températures utilisée, et qui conservent une dureté et une rigidité suffisantes sur la plage de températures, de telle sorte qu'une indentation irréversible de l'éprouvette par la sonde de détection ne se produise pas.

General Information

• Status: Published
• Publication Date: 08-Dec-2024
• ICS: 31.180 - Printed circuits and boards
• Technical Committee: TC 91 - Electronics assembly technology
• Drafting Committee: WG 10 - TC 91/WG 10
• Current Stage: PPUB - Publication issued
• Start Date: 09-Dec-2024
• Completion Date: 27-Dec-2024

Overview

IEC 61189-2-809:2024 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the test method for determining the X/Y coefficient of thermal expansion (CTE) of thick electrical insulating base materials using a Thermomechanical Analyzer (TMA). This method focuses on measuring dimensional changes in electrical insulating materials used in circuit boards and interconnection assemblies, ensuring these materials maintain structural integrity and performance across varying temperature ranges. The standard is applicable to materials that remain solid, hard, and rigid throughout the testing temperature range, preventing irreversible indentation by the TMA sensing probe.

Key Topics

• Scope and Applicability
  The standard applies specifically to thick base insulating materials for electronics that maintain physical solidity and rigidity over the temperature range tested, typically from 30 °C to 260 °C. It emphasizes testing both the fill (weft) and machine (warp) directions of woven fiber materials to evaluate anisotropic thermal expansion properties.

• Test Specimens
  Specimens for testing should be between 0.5 mm and 7.5 mm thick, and with length and width dimensions ranging from 5 mm to 12 mm and 5 mm to 10 mm respectively. Both "X" (weft/fill) and "Y" (warp) directions must be tested using at least three specimens each to ensure reliability and repeatability. Precise specimen preparation includes polishing and controlled drying to eliminate surface inconsistencies.

• Test Apparatus
  Required equipment includes a thermomechanical analyzer capable of measuring dimensional changes with 0.001 mm precision, a controlled circulating air oven for drying specimens at 110 °C ± 2 °C, and a desiccator or low-humidity drying cabinet maintaining less than 30% relative humidity at 23 °C ± 2 °C.

• Test Procedure
  The method outlines a detailed sequence, starting with specimen cleaning using isopropyl alcohol, drying, calibrating the TMA, and securing the specimen for testing. The specimen is heated at a controlled rate of 5 °C per minute, and dimensional changes are recorded to calculate the CTE for both X and Y directions. Proper specimen positioning and probe load (0.04 N to 0.10 N) are critical for accurate readings.

• Calculations and Reporting
  The standard provides formulas for calculating the X and Y coefficients of thermal expansion from dimensional measurements. Results must be reported systematically, including specimen preparation, testing conditions, and data obtained, facilitating transparency and reproducibility.

Applications

IEC 61189-2-809:2024 is essential for manufacturers and quality assurance teams involved with:

• Electrical Insulating Materials
  Ensuring material performance in printed circuit boards (PCBs), multilayer substrates, and other thick base electrical insulating components.

• Circuit Board Production
  Assessing thermal reliability of base materials to prevent warpage, delamination, or mechanical stress due to thermal cycling in electronic assemblies.

• Material Characterization and Selection
  Helping material scientists and engineers select insulating materials with appropriate thermal expansion coefficients to match other components and ensure dimensional stability in final products.

• Quality Control and Compliance
  Standardizing CTE testing procedures across internationally recognized frameworks to promote product reliability and interoperability.

Related Standards

• IEC 60194-1 & IEC 60194-2 – Vocabulary standards providing essential terminology concerning printed board design, manufacture, and assembly technologies that support clear understanding of definitions used in IEC 61189-2-809.

• Other Parts in IEC 61189 Series – Cover additional test methods for electrical materials, circuit boards, and interconnection assemblies, helping manufacturers ensure comprehensive evaluation and conformity of materials and processes.

• ISO/IEC Directives – Governing frameworks for developing international standards that IEC 61189-2-809 adheres to, ensuring global relevance and acceptance.

---

This standard represents a critical methodology for reliable measurement of thermal expansion, supporting the development and manufacture of high-quality electrical insulating materials and assemblies. By following IEC 61189-2-809:2024, organizations can improve product durability, reduce thermal stress failures, and maintain alignment with international best practices in electrical materials testing.

Standards Content (Sample)

IEC 61189-2-809 ®
Edition 1.0 2024-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for electrical materials, circuit boards and other interconnection
structures and assemblies –
Part 2-809: X/Y coefficient of thermal expansion (CTE) test for thick base
materials by TMA
Méthodes d'essai pour les matériaux électriques, les circuits imprimées et
autres structures d'interconnexion et ensembles –
Partie 2-809: Essai du coefficient de dilatation thermique (CTE) X/Y pour
matériaux de base épais à l'aide d'un analyseur thermomécanique (TMA)
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IEC 61189-2-809 ®
Edition 1.0 2024-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for electrical materials, circuit boards and other interconnection

structures and assemblies –
Part 2-809: X/Y coefficient of thermal expansion (CTE) test for thick base

materials by TMA
Méthodes d'essai pour les matériaux électriques, les circuits imprimées et

autres structures d'interconnexion et ensembles –

Partie 2-809: Essai du coefficient de dilatation thermique (CTE) X/Y pour

matériaux de base épais à l'aide d'un analyseur thermomécanique (TMA)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.180  ISBN 978-2-8327-0054-9

– 2 – IEC 61189-2-809:2024-© IEC 2024
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Test specimens . 5
5 Test apparatus . 6
6 Test procedure . 6
7 Calculations . 7
8 Report . 8
Bibliography . 9

Figure 1 – Diagram of sample direction . 6
Figure 2 – Specimen size versus temperature . 8

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR ELECTRICAL MATERIALS, CIRCUIT BOARDS AND
OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 2-809: X/Y coefficient of thermal expansion (CTE) test
for thick base materials by TMA

FOREWORD
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IEC 61189-2-809 has been prepared by IEC technical committee 91: Electronics assembly
technology. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
91/1983/FDIS 91/1994/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
– 4 – IEC 61189-2-809:2024-© IEC 2024
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61189 series, published under the general title Test methods for
electrical materials, circuit boards and other interconnection structures and assemblies, can be
found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
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• reconfirmed,
• withdrawn, or
• revised.
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TEST METHODS FOR ELECTRICAL MATERIALS, CIRCUIT BOARDS AND
OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 2-809: X/Y coefficient of thermal expansion (CTE) test
for thick base materials by TMA

1 Scope
This part of IEC 61189 defines the method to be followed for the determination of the X/Y
coefficient of thermal expansion of electrical insulating materials by the use of a
thermomechanical analyser (TMA).
This method is applicable to materials that are solid of the entire range of temperature used
and retain sufficient hardness and rigidity over the temperature range so that irreversible
indentation of the specimen by the sensing probe does not occur.
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.
IEC 60194-1, Printed boards design, manufacture and assembly – Vocabulary – Part 1:
Common usage in printed board and electronic assembly technologies
IEC 60194-2, Printed boards design, manufacture and assembly – Vocabulary – Part 2:
Common usage in electronic technologies as well as printed board and electronic assembly
technologies
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60194-1 and
IEC 60194-2 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Test specimens
4.1 The test specimens shall be between 0,5 mm to 7,5 mm thick. This thickness may be "as
received" or may be laminated by the user from pre-impregnated "B" stage material. If laminated
by the user, the user shall be responsible for the layup and curing parameters used for quality
acceptance by the manufacturer.
NOTE The repeatability of the test results will vary by the factors, such as layup used, the resin to glass ratio and
the ultimate cure of the laminated stack, etc.

– 6 – IEC 61189-2-809:2024-© IEC 2024
4.2 The test specimens shall be between 5 mm to 12 mm in length and between 5 mm to
10 mm in width. The width of the specimen shall be less than the length.
4.3 Unless otherwise specified, three specimens shall be prepared in both warp and weft
direction of the glass fibre from the same piece of material, and mark with "X" or "Y" directions,
as shown in Figure 1. The "X" direction is the fill (weft) of the woven fibre and the "Y" direction
is the machine direction (warp) of the woven fibre.

NOTE Sample 1 is CTE sample in "X" direction, the width direction of the sample is the "X" direction; Sample 2 is
CTE sample in "Y" direction, the width direction of the sample is the "Y" direction.
Figure 1 – Diagram of sample direction
4.4 Opposing sides of the test specimens shall be parallel, and surfaces shall be polished with
sandpaper to remove debris and protruding fibres (e.g. 600 grit sandpaper). After that then be
cleaned using isopropyl alcohol and dried for 1 hour at 110 °C ±2 °C.
NOTE The one-hour prebake can be eliminated if condition [see Clause 6 item a)] is performed immediately after
final polish.
5 Test apparatus
The test apparatus is composed of the following elements:
– thermomechanical analyzer (TMA) capable of determination of dimensional change to within
0,001 mm over the specified temperature range;
– circulating air oven capable of maintaining 110 °C ± 2 °C;
– dessicator or low humidity drying cabinet capable of maintaining an atmosphere less than
30 % relative humidity at 23 °C ± 2 °C.
6 Test procedure
The test procedure is as follows:
a) Immerse the specimen in isopropyl alcohol with agitation for 20 seconds, and then dried for
1 hour ± 10 minutes at 110 °C ± 2 °C in oven. After removal from the oven, the specimen
shall be cooled for 40 minutes in desiccator or drying cabinet before testing.
b) Calibrate the TMA instrument in accordance with the manufacturer's instructions.

c) Test the CTE of "X" direction, measure the initial width of the specimen which marked with
"X" direction, recorded as H.
d) Place the specimen on the stage of the TMA, the width direction of the test sample should
always be perpendicular to the test sample placement platform. The specimen should be
centred and rest flat on the stage. The thermocouple wire should be in contact with the
specimen or as near to the specimen as possible.
e) Place weights on the sensing probe and lower the TMA probe to ensure that the probe is in
contact with the specimen with a 0,04 N to 0,10 N load.
f) Heat the specimen at the rate of 5 ± 0,5 °C/min to a temperature which is 10 °C greater than
the required temperature range. The testing temperature range shall be specified by the
user so that the manufacturer and the user can test under the same temperature range. The
repeatability can be unacce
...