ISO/TS 25336:2025
(Main)Plastics — Thermosetting resin-based materials — Low-temperature cracking index test by embedded metal block method
Plastics — Thermosetting resin-based materials — Low-temperature cracking index test by embedded metal block method
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.
Plastiques — Matériaux à base de résines thermodurcissables — Essai d'indice de fissuration à basse température par la méthode du bloc métallique
General Information
Standards Content (Sample)
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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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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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 curing a thermosetting resin-based compounds
3.3
casting
manufacturing process for, e.g. the production of power electronic equipment using an automatic pressure
gel (APG) process or a traditional vacuum casting process
3.4
cracking resistance index
CR
characteristic data of the crack resistance capacity of the thermosetting resin-based materials embedded
with stress modules
Note 1 to entry: This data is used to compare the differences in crack resistance performance among different
thermosetting resin-based materials.
4 Apparatus
4.1 Vacuum drying oven. Degassing equipment for thermosetting resin-based compounds. The minimum
pressure of the equipment shall be at least 100 Pa.
4.2 Vacuum batching plant. Vacuum batching apparatus or similar vacuum batching apparatus of which
the minimum pressure of the equipment shall be at least 100 Pa.
4.3 Drying oven, for curing thermosetting resin-based compounds. The temperature and time settings
range of the oven shall be able to meet the required maximum temperature and holding time for the curing
process of the test specimens.
4.4 Temperature test chambers, which shall feature a minimum temperature of -70 °C and a temperature
ramp rate within the range of 0,1 to 0,3 °C/min. If the test conditions allow, a temperature test chamber can
also be equipped with a viewing window or a camera to monitor the test process.
5 Test method
5.1 mould and stress module
5.1.1 mould
When making the low-temperature cracking index mould, it should choose metal materials such as
35CrMo7 or P20.The mould is composed of a mould cavity plate and two covering plates. All three parts are
(10,0 ± 0,1) mm thick. The surface roughness shall reach Ra1.6.
The cavity plate shall be square with a side length of (140,0 + 0,1) mm and a thickness of (10,0 ± 0,1) mm. In
the centre of the mould cavity plate, there shall be a hollow cavity in the shape of a cylinder with a diameter
of φ(100,00 ± 0,02) mm. On the upper side edge of the mould cavity plate, there shall be an opening in the
centre, with a width of (10,0 ± 0,1) mm and a thickness of (10,0 ± 0,1) mm, served as the casting gate. At each
of the four corners of the cavity plate, there shall be a through-hole with a diameter of 8 mm for installing the
mould and securing the covering plate. The positions of the four holes align with those of the covering plates.
The mould structure diagram is shown in Figure 1.
NOTE In many laboratories, to prevent resin leakage, a sealing groove is often designed between the mould cavity
plate and the two sealing plates to accommodate rubber sealing rings.
a) Structure explosion diagram b) Mould explosion diagram
Key
1 covering plate
2 cavity plate
3 stress module
4 casting gate
5 vent
6 sample
7 fastener connecting hole
δ the thickness of the plate
Figure 1 — Schematic diagram of mould structure
5.1.2 Stress module
The material of the stress module should be consistent with the mould material. The stress module is a
quadrilateral metal plate with a thickness of (10 + 0,05) mm, and a
...
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