IEC 62899-202-10:2023

IEC 62899-202-10
®

Edition 1.0 2023-08
INTERNATIONAL
STANDARD

colour
inside


Printed electronics –
Part 202-10: Materials – Resistance measurement method for thermoformable
conducting layer

IEC 62899-202-10:2023-08(en)

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IEC 62899-202-10

®


Edition 1.0 2023-08




INTERNATIONAL



STANDARD








colour

inside










Printed electronics –

Part 202-10: Materials – Resistance measurement method for thermoformable

conducting layer
























INTERNATIONAL

ELECTROTECHNICAL


COMMISSION





ICS 29.035.01; 31.180 ISBN 978-2-8322-7325-8




  Warning! Make sure that you obtained this publication from an authorized distributor.


® Registered trademark of the International Electrotechnical Commission

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CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 In-situ resistance measurement method. 9
4.1 Measured value . 9
4.2 Test specimen . 9
4.2.1 Ink stack . 9
4.2.2 Size and shape . 10
4.2.3 Conductive layer layout . 10
4.3 Measurement apparatus . 11
4.3.1 General . 11
4.3.2 Elongation equipment . 11
4.3.3 Resistance measurement equipment . 12
4.4 Measurement parameters . 13
4.4.1 Elongation . 13
4.4.2 Elongation speed . 13
4.4.3 Elongation temperature . 13
4.5 Measurement procedure . 13
4.6 Measuring conductive line elongation . 14
4.7 Data analysis . 14
4.7.1 General . 14
4.7.2 Calculating results . 14
4.7.3 Excluding outliers in data analysis . 15
4.8 Measurement report . 16
5 Pre-and post-elongation resistance measurement method . 16
5.1 Measured value . 16
5.2 Test specimen . 16
5.3 Measurement apparatus . 16
5.3.1 Elongation equipment . 16
5.3.2 Resistance measurement equipment . 17
5.4 Measurement parameters . 17
5.5 Measurement procedure . 17
5.6 Measuring conductive line elongation . 17
5.7 Data analysis . 17
5.7.1 General . 17
5.7.2 Calculating results . 17
5.7.3 Excluding outliers in data analysis . 18
5.8 Measurement report . 18
Annex A (informative) Example report for pre- and post-elongation resistance
measurement . 19
A.1 Test specimen information . 19
A.2 Elongation parameters . 19
A.3 Results . 19
A.3.1 Measured line elongation range and elongation at electric break . 19

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IEC 62899-202-10:2023 © IEC 2023 – 3 –
A.3.2 Analysis of potential outliers . 20
A.3.3 Average resistance changes . 20
A.4 Date of the measurements . 21
Annex B (informative) Guidelines for test specimen shape and conductive layer layout . 22
B.1 Test specimen shape and dimensions . 22
B.2 Conductive layer layout . 23
B.3 General guidelines for specimen shapes and conductive layer layout. 24
Bibliography . 26

Figure 1 – Substrate with ink stack in 2D (top) and 3D (bottom) shape . 6
Figure 2 – Example of test specimen shape . 10
Figure 3 – Example of conductive layer layout . 11
Figure 4 – Example of elongation equipment . 12
Figure 5 – Example of test specimen holder . 12
Figure 6 – Example of measuring conductive line elongation . 14
Figure 7 – Example of conductive line resistance increase (%) as a function of
elongation time (s) . 15
Figure A.1 – Conductive layer layout . 19
Figure A.2 – Boxplot of resistance change before outlier analysis . 20
Figure A.3 – Boxplot of conductive line resistance changes . 21
Figure B.1 – Example of the test specimen shape . 22
Figure B.2 – Example of conductive layer layout . 24

Table 1 – Test specimen ink stack . 10
Table A.1 – Conductive lines that had electric break during elongation . 20
Table A.2 – Resistance changes according to line elongation ranges . 21

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

PRINTED ELECTRONICS –

Part 202-10: Materials – Resistance measurement
method for thermoformable conducting layer

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62899-202-10 has been prepared by IEC technical committee 119: Printed Electronics. It
is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
119/436/FDIS 119/448/RVD

Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

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IEC 62899-202-10:2023 © IEC 2023 – 5 –
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 62899 series, published under the general title Printed electronics,
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
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
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contents. Users should therefore print this document using a colour printer.

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INTRODUCTION
In-mould-electronics (IME) manufacturing can include thermoforming during which two-
dimensional electric films with conducting layers are thermoformed into three-dimensional
shapes. During thermoforming, the substrate and printed layers will experience plastic strain
leading to elongation (see Figure 1). The conductive layer’s resistance increases as a function
of plastic strain. Designers of electric circuitry should know how much the resistance changes.
Using a standardized measurement method ensures comparability of the results.

NOTE 1 The top image shows a 2D substrate and ink stack after printing and cure.
NOTE 2 The bottom image shows a substrate and ink stack after thermoforming into a 3D shape. The ink layers
have been elongated.
Figure 1 – Substrate with ink stack in 2D (top) and 3D (bottom) shape

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IEC 62899-202-10:2023 © IEC 2023 – 7 –
PRINTED ELECTRONICS –

Part 202-10: Materials – Resistance measurement
method for thermoformable conducting layer



1 Scope
This part of IEC 62899 defines terminology and measurement methods for the resistance
change of conductive ink layer(s) as a function of thermoplastic elongation. The method
measures resistance changes in-situ or post-elongation.
This document is applicable to thermoformable substrates with conductive ink layers. The
thermoformable substrates can have printed graphic ink as well and cover insulation layers.
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 62899-202, Printed electronics – Part 202: Materials – Conductive ink
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:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
in-mould-electronics
IME
3D circuit manufactured by integrating and embedding printed electronics and electronic
components within shaped structures
Note 1 to entry: Manufacturing steps include, but are not limited to, printing, surface mounting, thermoforming and
injection moulding.
3.2
thermoforming
process of shaping heated thermoplastic sheets or other articles, generally on a mould, followed
by cooling
Note 1 to entry: In this document, the test structures are elongated in the measurement equipment; they are not
thermoformed on a mould.
[SOURCE: ISO 472:2013, 2.1172, modified – Note 1 has been added.]

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3.3
thermoformable substrate
substrate made of a material that deforms irreversibly when subjected to heating and force
3.4
conductive ink
fluid in which one or more conductive materials are dissolved or dispersed, and which is used
to form an electrically conductive structure
[SOURCE: IEC 62899-202-7:2021, 3.1, modified – “printable fluid intended for printing in which
one or more molecules, polymers, or particles” is changed to “fluid in which one or more
conductive materials” and “which becomes an electrically conductive layer by post treatment
such as heating” is changed to “and which is used to form an electrically conductive structure”.]
3.5
graphic ink
composite material containing colorants, functional components, vehicle and additives
Note 1 to entry: In most cases, it is applied as a fluid to a substrate by a printing process and setting or drying by
either physical (evaporation) and/or chemical (polymerizations e.g., oxidation, radiation induced, or other) processes
in order to form an image for decorative, informative or technical purposes.
Note 2 to entry: Functional components are materials in the graphic ink that add or enhance its characteristics.
Note 3 to entry: Graphic ink forms visual layers after post treatment such as heating.
[SOURCE: ISO 2834-2:2015, 3.5, modified – the term “printing ink” is changed to “graphic ink”,
Note 2 and Note 3 are added.]
3.6
insulation layer
film-like structure formed by printing or coating of insulator ink on a substrate, which can
become electrically insulating after post treatment
[SOURCE: IEC 62899-204:2019, 3.3, modified – “insulating layer” is changed to “insulation
layer” and “electrically insulating body made of insulator ink, which is printed or coated on a
substrate, followed as necessary by the application of a post treatment such as heating” is
changed to “structure formed by printing or coating of insulator ink on a substrate, which can
become electrically insulating after post treatment”]
3.7
ink stack
combination of ink layers printed on a substrate
Note 1 to entry: Ink layers can include graphic ink layers and conductive layers, or conductive layers only. A stack
can also include an insulation layer.
3.8
elongation
increase of length of a test piece
[SOURCE: ISO 1924-3:2005, 3.3]
3.9
elongation at break
percent elongation of a test piece at rupture
[SOURCE: ISO 1382:2020, 3.171, modified – in the term, “ultimate elongation” has been
removed.]

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IEC 62899-202-10:2023 © IEC 2023 – 9 –
3.10
plastic strain
plastic strain component of a controlled strain
Note 1 to entry: The strained specimen does not return to its original size and shape after the deforming force has
been removed.
[SOURCE: ISO 23718:2007:2007, 1.6.28, modified – in the term, the symbol has been removed
and Note 1 is added.]
3.11
glass transition temperature
temperature where a polymer substrate changes from a rigid glassy material to a soft (not
melted) material, and is usually measured in terms of the stiffness, or modulus
[SOURCE: ISO 11119-2:2020, 3.22, modified – in the term, the symbol has been removed.]
3.12
melting temperature
temperature at which transition between fully or partially crystalline solid becomes a liquid of
variable viscosity, which is indicated by an endothermic peak in the DSC curve
[SOURCE: ISO 15309:2013, 3.4, modified – in the term, the symbol has been removed, Note 1
and Note 2 have been omitted.]
4 In-situ resistance measurement method
4.1 Measured value
The measured value is the conducting layer resistance change (%) as a function of time (s) or
elongation (mm) at specified elongation speed (mm/s) and temperature (ºC).
Results include also conducting layer resistance change (%) between pre- and post-elongation
at specified elongation (mm) and elongation speed (mm/s). Resistance measurements are
made at room temperature (ºC).
4.2 Test specimen
4.2.1 Ink stack
Select the substrate material that can be elongated at elevated temperatures, i.e., it shall be
thermoformable. The substrate shall include conductive ink layers that have been printed and
cured in accordance with ink material specifications. The test specimen can also include graphic
and insulation layers that have been printed and cured in accordance with ink material
specifications. All of these layers shall be thermoformable as well.
The following four types of stacks are permitted:
a) substrate and conductive layer;
b) substrate, graphic layer and conductive layer;
c) substrate, conductive layer and insulation layer;
d) substrate, graphic layer, conductive layer and insulation layer.
The substrate, conductive ink layer, graphic ink layer and insulation layer form an ink stack (see
Table 1).

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Table 1 – Test specimen ink stack
Material Specifications
Substrate Thermoformable material Nominal thickness shall be 0,175 mm or more. The
tolerance of the nominal thickness shall be ±10 % for
maximum and minimum values.
Graphic layer Thermoformable graphic This layer is optional. If used, select graphic ink materials,
inks layer thicknesses and number of layers.
Conductive layer Thermoformable conductive Select conductive ink materials, layer thicknesses and
inks number of layers.
Insulation layer Thermoformable insulation This layer is optional. If used, select insulation materials,
layer layer thicknesses and number of layers.
NOTE 1 Films thinner than 0,175 mm can have internal stresses that cause flaws to the thermoformed shapes.
NOTE 2 Test specimen with thicker substrate, for example, > 0,50 mm, will have longer heating times, and
temperature distribution can be less homogeneous.

4.2.2 Size and shape
The size of the elongated area shall be smaller than the size of the heater element in the
measurement apparatus. However, the size of the test specimen can be larger so that it can be
fastened into the test specimen holder of the measurement equipment.
The test specimen shape shall be suitable for uniaxial elongation (see Figure 2). The substrate
shall be narrower in the elongation area than outside it. This is to concentrate conductive line
elongation to the intended area. The substrate also has an hour-glass shape, and its middle is
slightly curved. This is to improve uniform elongation of conductive ink lines. See more from
Annex B.

NOTE The red rectangle comprises the elongation area.
Figure 2 – Example of test specimen shape
4.2.3 Conductive layer layout
All conductive lines shall have the same width in the elongated area. This is to minimize the
elongation differences between the conductive lines. Suitable line widths are, for example,
0,3 mm, 0,45 mm, 0,6 mm, 1,0 mm, and 1,5 mm. The line width of 0,3 mm can be suitable only
for appropriately stretching conductive inks or for small elongation (e.g., < 20 %). The
conductive line width in the test specimen shall be recorded in the test report.
The conductive layer layout shall also include reference dots on both sides of conductive lines
in the elongation area. They are used to measure the actual elongation of the conductive lines.
The distance between the dots shall be below 10 mm, it can be for example 5 mm. If the test
specimen ink stack includes an insulation layer, it shall not hide the reference dots. For
example, the insulating layer is transparent or it has openings for the reference dots.

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IEC 62899-202-10:2023 © IEC 2023 – 11 –
Outside the elongation area, the conductive lines shall be at least two times wider than the
conductive lines in the elongated area. This is to concentrate conductive line elongation to the
intended area. The conductive line length is defined by sample size. Conductive lines shall
make electrical contact with the test specimen holder. In addition, there shall be a clearance
between the edge of the substrate and the conductive lines, for example 12 mm. This is to
minimize the elongation differences between the conductor lines. Figure 3 shows an example
of the layout.
Select the conducting layer thickness from a range that the conductive ink manufacturer has
specified. If the conductive ink manufacturer has not specified layer thicknesses, it can be
agreed between the user and supplier. Conducting layer thickness values shall be measured
from at least three different samples. In each sample, at least both edge lines and the middle
line shall be measured. The recommendation is not to measure samples that have been printed
sequentially.

NOTE 1 The black lines show the conductive layer.
NOTE 2 The red rectangle comprises the elongated area.
NOTE 3 The conductive layer lines will not necessarily contact the test specimen holder if they are used only for
pre- and post-resistance measurements.
Figure 3 – Example of conductive layer layout
4.3 Measurement apparatus
4.3.1 General
The measurement apparatus consists of elongation equipment and resistance measurement
equipment.
4.3.2 Elongation equipment
The elongation equipment shall include:
a) test specimen chamber with holder;
b) heater element with temperature sensors;
c) elongation element.
An example of the elongation equipment is shown Figure 4. The measurement apparatus also
includes a cover because measurements shall be made at constant temperature (the cover is
not shown in Figure 4).

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The test specimen chamber with holder shall isolate the temperature from the ambient
temperature so that requirements for the heater element are fulfilled. Figure 5 shows an
example of the test specimen holder.
The heater element shall be able to heat the test specimen to the elongation temperature in
less than 30 min and hold the temperat
...