Semiconductor devices - Micro-electromechanical devices - Part 35: Test method of electrical characteristics under bending deformation for flexible electro-mechanical devices

IEC 62047-35:2019 specifies the test method of electrical characteristics under bending deformation for flexible electromechanical devices. These devices include passive micro components and/or active micro components on the flexible film or embedded in the flexible film. The desired in-plane dimensions of the device for the test method ranges typically from 1 mm to 300 mm and the thickness ranges from 10 mm to 1 mm, but these are not limiting values. The test method is so designed as to bend devices in a quasi-static manner monotonically up to the maximum possible curvature, i.e. until the device is completely folded, so that the entire degradation behaviour of the electric property under bending deformation is obtained. This document is essential to estimate the safety margin under a certain bending deformation and indispensable for reliable design of the product employing these devices.

Dispositifs à semiconducteurs - Dispositifs microélectromécaniques - Partie 35 : Méthode d’essai des caractéristiques électriques sous déformation par courbure de dispositifs électromécaniques souples

L’IEC 62047-35:2019 spécifie la méthode d’essai des caractéristiques électriques sous déformation par courbure de dispositifs électromécaniques souples. Ces dispositifs incluent des microcomposants passifs et/ou des microcomposants actifs situés sur ou intégrés dans le film souple. Typiquement, les dimensions dans le plan souhaitées du dispositif pour la méthode d’essai sont comprises entre 1 mm et 300 mm, et l’épaisseur est comprise entre 10 mm et 1 mm. Ces valeurs ne sont pas limitatives. La méthode d’essai est conçue pour plier les dispositifs de manière quasi statique et monotone, jusqu’à la courbure maximale possible, c’est-à-dire jusqu’à ce que le dispositif soit complètement plié, afin d’obtenir le comportement des propriétés électriques sous dégradation complète, lors d’une déformation par courbure. Le présent document est essentiel pour estimer la marge de sécurité lors d’une certaine déformation par courbure et indispensable pour concevoir de manière fiable des produits qui utilisent ces dispositifs.

General Information

Status
Published
Publication Date
21-Nov-2019
Current Stage
PPUB - Publication issued
Completion Date
22-Nov-2019
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IEC 62047-35
Edition 1.0 2019-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices – Micro-electromechanical devices –
Part 35: Test method of electrical characteristics under bending deformation
for flexible electromechanical devices
Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 35: Méthode d’essai des caractéristiques électriques sous déformation
par courbure de dispositifs électromécaniques souples
IEC 62047-35:2019-11(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62047-35
Edition 1.0 2019-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices – Micro-electromechanical devices –
Part 35: Test method of electrical characteristics under bending deformation
for flexible electromechanical devices
Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 35: Méthode d’essai des caractéristiques électriques sous déformation
par courbure de dispositifs électromécaniques souples
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.99 ISBN 978-2-8322-7636-5

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

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 62047-35:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

3.1 General ................................................................................................................... 7

3.2 Loading configurations ............................................................................................ 7

3.3 Measure of loading levels ....................................................................................... 8

4 Test piece ....................................................................................................................... 8

4.1 General ................................................................................................................... 8

4.2 Shape of a test piece .............................................................................................. 8

5 Test method .................................................................................................................... 9

5.1 Principle ................................................................................................................. 9

5.2 Test apparatus ...................................................................................................... 10

5.3 Procedure ............................................................................................................. 10

5.3.1 Testing conditions ......................................................................................... 10

5.3.2 Selection of bending direction ........................................................................ 11

5.3.3 Determination of bending axes ...................................................................... 11

5.3.4 Measurement of test piece dimensions .......................................................... 11

5.3.5 Measurement of folding distance ................................................................... 12

5.3.6 Number of tests ............................................................................................. 12

5.3.7 Instrumentation .............................................................................................. 12

5.3.8 End of testing ................................................................................................ 13

6 Test report ..................................................................................................................... 13

6.1 General ................................................................................................................. 13

6.2 Bending direction(s) and in-plane locations of bending axes ................................. 13

6.3 Dimensions of the test piece ................................................................................. 14

6.4 Performance degradation characteristics with the folding distance ........................ 14

6.5 Distance at a defined operation limit ..................................................................... 15

6.6 Testing conditions ................................................................................................. 15

Annex A (normative) Example of flexible MEMS device ........................................................ 16

Annex B (informative) Controls for appropriate performance instrumentation and

setting of bending axis position ...................................................................................... 18

B.1 Loading wall design with electric accessing cavity and fine adjustment

capability for bending axis location during the test ................................................ 18

B.2 Special arrangement of the target parts of device to obtain a number of

bending axis locations in a single testing .............................................................. 19

Annex C (informative) Loading principle for extremely thin soft devices ............................... 20

Annex D (informative) Issues related to local loading severity .............................................. 21

D.1 Possible inhomogeneity in local curvature and parameter of loading ..................... 21

D.2 Possible variations of loading parameter ............................................................... 21

Figure 1 – Schematic illustration of a flexible MEMS test piece ............................................... 9

Figure 2 – Principle of folding test ......................................................................................... 10

Figure 3 – Selection of bending axis ..................................................................................... 12

Figure 4 – Illustration of performance degradation in the test report ...................................... 14

---------------------- Page: 4 ----------------------
IEC 62047-35:2019 © IEC 2019 – 3 –

Figure A.1 – Target part and loading configuration of test piece for organic thin-film

transistor device ................................................................................................................... 16

Figure A.2 – Device performance degradation behaviour and distances at defined

operation limits for an organic thin-film effect transistor ........................................................ 17

Figure B.1 – Loading point adjustment mechanism ............................................................... 18

Figure B.2 – Cascade arrangement of target parts for efficient testing .................................. 19

Figure C.1 – Bending configuration ....................................................................................... 20

Figure D.1 – Possibility of inhomogeneous local curvature distribution .................................. 21

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– 4 – IEC 62047-35:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –
Part 35: Test method of electrical characteristics under bending
deformation for flexible electromechanical devices
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62047-35 has been prepared by subcommittee 47F: Micro-

electromechanical devices, of IEC technical committee 47: Semiconductor devices.
The text of this International Standard is based on the following documents:
FDIS Report on voting
47F/344/FDIS 47F/352/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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IEC 62047-35:2019 © IEC 2019 – 5 –

A list of all parts in the IEC 62047 series, published under the general title Semiconductor

devices – Micro-electromechanical devices, 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 "http://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 publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
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– 6 – IEC 62047-35:2019 © IEC 2019
INTRODUCTION

In the recent trend toward ubiquitous sensor society and the world of internet of things,

demand and thus the market for softer electronic devices are quickly expanding. That is what

flexible micro-electromechanical devices are for, some of which are already released into the

market. Even a so-called foldable device is under development and will soon appear in the

market. However, to operate trillions of such devices for the comfort and safety of human

beings, the reliability of the individual devices is a critical concern. Especially in the case of

flexible devices, robustness against bending deformation is an important issue which is

shared among all the producers and users of such devices. In order to understand how safe a

situation is, critical conditions for possible dangers should be thoroughly determined so that

the potential risk can be for the first time managed. In this context, flexible devices should be

folded in two at least once so that every possible critical failure actually appears. This

standard procedure of testing is designed with the emphasis on such a point and with the

applicability not only to already emerging flexible devices but also to so-called foldable

devices which still function even when the device is folded.
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IEC 62047-35:2019 © IEC 2019 – 7 –
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –
Part 35: Test method of electrical characteristics under bending
deformation for flexible electromechanical devices
1 Scope

This part of IEC 62047 specifies the test method of electrical characteristics under bending

deformation for flexible electromechanical devices. These devices include passive micro

components and/or active micro components on the flexible film or embedded in the flexible

film. The desired in-plane dimensions of the device for the test method ranges typically from

1 mm to 300 mm and the thickness ranges from 10 µm to 1 mm, but these are not limiting

values. The test method is so designed as to bend devices in a quasi-static manner

monotonically up to the maximum possible curvature, i.e. until the device is completely folded,

so that the entire degradation behaviour of the electric property under bending deformation is

obtained. This document is essential to estimate the safety margin under a certain bending

deformation and indispensable for reliable design of the product employing these devices.

2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 General
3.1.1
flexible micro-electromechanical system
flexible MEMS

device with structured semiconductor and/or mechanical components electrically connected to

each other, being assembled onto or embedded into flexible substrate and operated without

unacceptable loss of its functions under bending deformation

EXAMPLE Organic transistors, thermistors, smart diapers with wet sensors and smart epidermal patches for

health care, etc.
Note 1 to entry: This note applies to the French language only.
3.2 Loading configurations
3.2.1
bending axis

line on a device around which the device is bent with the minimum radius of curvature

Note 1 to entry: Due to the characteristics of this document, the bending axis can be and should be placed at

arbitrary positions in arbitrary directions in accordance with the requirements of the evaluation. The actual

positions and directions shall be intentionally determined according to the structures on the test piece.

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– 8 – IEC 62047-35:2019 © IEC 2019
3.2.2
bending direction
direction in which the device is bent
3.3 Measure of loading levels
3.3.1
folding distance

distance between two loading walls, representing the load level applied to the device

Note 1 to entry: The degree of bending given to the device is here represented by the distance between two walls

approaching close to each other to bend the device, which is denoted as the folding distance.

Note 2 to entry: This measure may be optionally converted to the radius of curvature given around a bending axis

but it may not be uniform between the two walls especially when the rigidity distribution around the bending axis is

not homogeneous due to the heterogeneity of structures. More details are given in Annex D.

3.3.2
distance at defined operation limit

folding distance(s) corresponding to unacceptable deterioration(s) in the electrical

performance of the test piece
Note 1 to entry: More details can be found in Annex A.
4 Test piece
4.1 General

A flexible MEMS device, which is bent in use, can in principle be a test piece as it is and

subjected to the evaluation of this document. In principle, this test method is applicable

without restriction as to the size and shape of the devices. However, for ease of a load

application, it may be cut into a rectangular shape with target parts to be loaded at the center

as mentioned in 4.2. More methods for test piece preparation are suggested in Annex B.

4.2 Shape of a test piece

A rectangular shape of the test piece should be used for the ease of experiment as shown in

Figure 1. It may be necessary to cut out a part of the devices for the test, especially when the

target part to be tested, which determines its own functional feature, is not located in the

center of the device. In this case, the test piece shall be prepared in a rectangular form by

cutting a part out of the entire device with the target part located at the center of two parallel

edges which should also be parallel to the bending axis. This is because the point to be

loaded to the end is limited in this test method only along the bending axis likely coming out at

the center due to the loading scheme explained in 5.1.

In this document, the length l and the width w of test piece are the dimensions of the test

piece in the perpendicular and parallel direction to the bending axis, respectively. Because of

the structures assembled on or embedded in the flexible substrate, the thickness may not be

uniform over the entire device and hence depends on the location.

As a number of target parts can be arranged on a substrate, especially for testing purposes in

accordance with this document, some recommendations are given in Annex B.

NOTE The length and width can be interchangeable when the bending axis is rotated by 90°, which is

symbolically illustrated in Figure 3.
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IEC 62047-35:2019 © IEC 2019 – 9 –
Key
1 target part 2 interconnects
3 electrodes 4 flexible substrate
5 bending axis 6 bending direction
7 length 8 width
9 thickness
Figure 1 – Schematic illustration of a flexible MEMS test piece
5 Test method
5.1 Principle

The principles of loading to the test piece are illustrated in Figure 2. The device shall be

inserted between two walls sliding closer to each other as illustrated in Figure 2 a). Then let

the distance between two walls, i.e. folding distance d, be gradually shortened as shown in

Figure 2 b) until finally touching each other with the folded test piece in between as in Figure

2 c). While the device is folded gradually tighter and tighter, its functions should be evaluated

to find which portion of the performance could be maintained while the folding distance is

applied.
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– 10 – IEC 62047-35:2019 © IEC 2019
a) Initial stage b) Middle stage c) Final stage
Key
1 folding distance d
2 test piece
Figure 2 – Principle of folding test
5.2 Test apparatus

There is no special requirement for the configuration of the test apparatus in this document,

as long the device can be folded tighter and tighter until the end of the test. However, the

width and height of the walls shall be longer, preferably at least by 5 %, than the width and

half the length of the test piece, respectively, so that the whole test piece is firmly pressed by

the walls. The surface flatness and parallelism of the walls are carefully prepared so that they

do not to touch each other before the end of the test. The variance of the gap between the

walls shall be smaller than the thickness of the test piece. The surface roughness and

flatness of the walls are recommended to be less than 1/10 of the thickness of the test piece

so as not to distort the test piece by bumps of the wall except for the intended bending

deformation. Either wall or both walls are shifted by a motor drive system, or a manually-

actuated linear stage. A number of recommendations for the convenience of experiment can

be found in Annex B and Annex C.

The folding distance shall be measured to an accuracy of less than 5 % relative to the folding

distance itself. Therefore, it may be suggested to use a number of tools, for example a scale

for the millimeter range, a micrometer gauge for the submillimeter range, or a laser

displacement meter or microscopy for the micron and sub-micron range.

NOTE Not an absolute error for full range measurement but a relative error on the folding distance is of

importance to maintain the reproducibility in the bending deformation, especially around the end of the test,

because the nominal curvature can be approximated by 2/d under the bending deformation as shown in Figure 2b).

In addition, the value of d ranges from l, for example more than 100 mm, to 2t, for example values less than a

millimeter. The dimension with such a wide range is difficult to measure with an accuracy of less than 1 % by a

ready-made apparatus. That is why the accuracy of the folding distance is noted in terms of the relative value with

an accuracy of 5 % for the ease of experiment in this document.
5.3 Procedure
5.3.1 Testing conditions

Since the aim of this document is to see the deterioration behaviour of a device's performance

by bending to the end of possible curvature, it may not always be easy to find the testing

speed adequately corresponding to the conditions of the actual device operation. Therefore,

the evaluation of time-dependent deformation behaviour such as visco-elasticity is regarded

here as out of the scope, and thus the holding time between two loading steps before starting

the instrumentation as well as the loading speed itself are not specified here. It is here simply

suggested to keep the holding time for measurement the same for all the steps and be aware

of any drift after increasing the folding distance. The test speed and holding time determined

by the user shall be included in the test report, for example l per minute of the wall moving

speed and 1-min holding time per each measurement. Since substrates for flexible MEMS

may often be made of polymeric materials, the deformation behaviour should be in principle

more or less time-dependent. Non-elastic time-dependent behaviour should be mentioned in

the test report, if any is noticed.
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IEC 62047-35:2019 © IEC 2019 – 11 –

Other conditions for testing, such as temperature and humidity, etc., shall be so far as

possible the same as those where the devices are operated in actual use.

NOTE 1 Since the aim of this document is to see the deterioration behaviour of the device's performance against

monotonic bending to the end of possible curvature, it may not be always easy to find testing conditions (especially

speed) which adequately correspond to those of the actual device operation. In such cases, the users are

responsible for determining the conditions and report them appropriately as mentioned in 6.6.

NOTE 2 When the
...

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