ISO/TS 25336:2025

Technical
Specification
ISO/TS 25336
First edition
Plastics — Thermosetting
2025-10
resin-based materials — Low-
temperature cracking index test by
embedded metal block method
Plastiques — Matériaux à base de résines thermodurcissables —
Essai d'indice de fissuration à basse température par la méthode
du bloc métallique
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
5 Test method . 2
5.1 mould and stress module .2
5.1.1 mould .2
5.1.2 Stress module .3
5.1.3 Assembly of mould .4
5.2 Specimen preparation .5
5.2.1 Preheat .5
5.2.2 Make thermosetting resin base compound .5
5.2.3 Casting thermosetting resin-based condensate . .6
5.2.4 Vacuum degassing .6
5.2.5 Curing .6
5.2.6 Demoulding and treatment .7
5.3 Test procedures .7
5.3.1 Preliminary test .7
5.3.2 Cracking temperature test .7
6 Low-temperature cracking index calculation . 8
7 Test report . 8
Bibliography .10

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
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iv
Introduction
With the advancement of large-scale integration of integrated circuits and miniaturization of electronic
components, thermosetting resin-based materials have been increasingly adopted in power electronics
device encapsulation. However, their low-temperature brittleness can lead to encapsulation cracking
failures.
This document introduces the embedded metal block method, and the corresponding moulds, stress module
and sample preparation are also recommended. The method simulates encapsulation structures by pre-
embedding stress modules in test specimens and determines the critical temperature for material cracking
through thermal testing. A quantitative evaluation methodology, the low-temperature cracking index (CR),
is established accordingly. This method has been applied by power electronics manufacturers for screening
and validation of encapsulation materials such as epoxy resins.
This document facilitates innovation in material research and development and enhances the reliability of
electronic devices.
v
Technical Specification ISO/TS 25336:2025(en)
Plastics — Thermosetting resin-based materials — Low-
temperature cracking index test by embedded metal
block method
1 Scope
This document defines a method for testing the low-temperature cracking index of thermosetting resin-
based materials.
The test method described in this document is suitable for quantifying and comparing the low-temperature
cracking of thermosetting resin-based materials in laboratory settings.
This document does not refer to thermosetting resin-based materials that can also crack at 0 °C and above.
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 472, Plastics — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following 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
thermosetting resin-based compound
liquid or semi-solid compound for pouring power electronic equipment comprising at least a thermosetting
resin and a curing agent, and optionally one or more of the additives such as fillers, tougheners, accelerators, etc.
3.2
thermosetting resin-based condensate
product formed by cu
...