IEC 62341-5-2:2013

IEC 62341-5-2 ®
Edition 1.0 2013-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –
Part 5-2: Mechanical endurance testing methods

Afficheurs à diodes électroluminescentes organiques (OLED) –
Partie 5-2: Méthodes d’essais d'endurance mécanique

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IEC 62341-5-2 ®
Edition 1.0 2013-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –

Part 5-2: Mechanical endurance testing methods

Afficheurs à diodes électroluminescentes organiques (OLED) –

Partie 5-2: Méthodes d’essais d'endurance mécanique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 31.260 ISBN 978-2-8322-0964-6

– 2 – 62341-5-2 © IEC:2013
CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references . 6

3 Terms and definitions . 7

4 Abbreviations . 7

5 Standard atmospheric conditions . 7

6 Evaluations . 7

6.1 Visual examination and verification of dimensions . 7
6.2 Reporting . 8
7 Mechanical endurance test methods . 8
7.1 General . 8
7.2 Vibration (sinusoidal) . 8
7.2.1 General . 8
7.2.2 Purpose . 8
7.2.3 Test apparatus . 8
7.2.4 Test procedure . 8
7.2.5 Evaluation . 11
7.3 Shock . 11
7.3.1 General . 11
7.3.2 Purpose . 11
7.3.3 Test apparatus . 11
7.3.4 Test procedure . 11
7.3.5 Evaluation . 12
7.4 Quasistatic strength . 12
7.4.1 General . 12
7.4.2 Purpose . 12
7.4.3 Specimen . 13
7.4.4 Test apparatus . 13
7.4.5 Test procedure . 13
7.4.6 Evaluation . 14
7.5 Four-point bending test . 14
7.5.1 General . 14

7.5.2 Purpose . 14
7.5.3 Specimen . 14
7.5.4 Test apparatus . 15
7.5.5 Test procedure . 15
7.5.6 Post-testing analysis . 16
7.5.7 Evaluation . 17
7.6 Transportation drop test . 17
7.6.1 General . 17
7.6.2 Purpose . 17
7.6.3 Test sample . 17
7.6.4 Test procedure . 17
7.6.5 Evaluation . 18
7.7 Peel strength test . 18
7.7.1 Purpose . 18

62341-5-2 © IEC:2013 – 3 –
7.7.2 Test procedure . 18

7.7.3 Evaluation . 19

Annex A (informative) Example of the raw test data reduction for four-point bending

test . 20

Bibliography . 28

Figure 1 – Configuration of OLED shock test set-up . 11

Figure 2 – Schematic of quasistatic strength measurement apparatus example . 13

Figure 3 – Schematics of test apparatus and pinned bearing edges . 15

Figure 4 – Specimen configuration under four-point bending test . 15
Figure 5 – Order of transportation package drop . 18
Figure 6 – Example of peeling strength test . 19
Figure A.1 – Specimen dimensions used for sample test . 20
Figure A.3 – Finite element model of test specimen . 22
Figure A.4 – Displacement contour map after moving down loading-bar by 2 mm . 23
Figure A.5 – Contour map of maximum principal stress distribution . 23
Figure A.6 – Maximum principal stress and maximum stress along the edge . 24
Figure A.7 – Final relationship between panel strength and failure load . 24
Figure A.8 – Extraction of conversion factor by linear fitting . 25
Figure A.9 – Example of Weibull distribution of strength data and statistical outputs . 27
Figure A.10 – Fitted failure probability distribution of strength data . 27

Table 1 – Frequency range – Lower end . 9
Table 2 – Frequency range – Upper end . 9
Table 3 – Recommended frequency ranges . 10
Table 4 – Recommended vibration amplitudes . 10
Table 5 – Conditions for shock test . 12
Table 6 – Examples of test parameter combinations . 16
Table 7 – Example of package drop sequence . 18
Table A.1 – Results of raw test data . 21
Table A.2 – Example of conversion factor (t = 0,4 mm, test span = 20 mm/40 mm) . 25

Table A.3 – Failure load and converted strength data . 26

– 4 – 62341-5-2 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 5-2: Mechanical endurance testing methods

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 in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62341-5-2 has been prepared by IEC technical committee 110:
Electronic display devices.
The text of this standard is based on the following documents:
FDIS Report on voting
110/472/FDIS 110/486/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62341 series, published under the general title Organic light
emitting diode (OLED) displays, can be found on the IEC website.

62341-5-2 © IEC:2013 – 5 –
The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication 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.
– 6 – 62341-5-2 © IEC:2013
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 5-2: Mechanical endurance testing methods

1 Scope
This part of IEC 62341 defines testing methods for evaluating mechanical endurance quality

of Organic Light Emitting Diode (OLED) display panels and modules or their packaged form
for transportation. It takes into account, wherever possible, the environmental testing methods
outlined in specific parts of IEC 60068. The object of this standard is to establish uniform
preferred test methods for judging the mechanical endurance properties of OLED display
devices.
There are generally two categories of mechanical endurance tests: those relating to the
product usage environment and those relating to the transportation environment in packaged
form. Vibration, shock, quasistatic strength, four-point bending test and peel strength test are
introduced here for usage environment, while transportation drop test is applicable to the
transportation environment. Mechanical endurance tests may also be categorized into mobile
application, notebook computer or monitor application and large size TV application. Special
considerations or limitations of test methods according to the size or application of the
specimen will be noted.
NOTE This standard is established separately from IEC 61747-5-3, because the technology of organic light
emitting diodes is considerably different from that of liquid crystal devices in such matters as:
– used materials and structure;
– operation principles;
– measuring methods.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests–Test Fc: Vibration (sinusoidal)

IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests–Test Ea and guidance: Shock
IEC 61747-5:1998, Liquid crystal and solid-state display devices – Part 5: Environmental,
endurance and mechanical test methods
IEC 61747-5-3:2009, Liquid crystal display devices – Part 5-3: Environmental, endurance and
mechanical test methods – Glass strength and reliability
IEC 62341-1-2:2007, Organic light emitting diode displays – Part 1-2: Terminology and letter
symbols
IEC 62341-5:2009, Organic light emitting diode (OLED) displays – Part 5: Environmental
testing methods
IEC 62341-6-1:2009, Organic light emitting diode (OLED) displays – Part 6-1: Measuring
methods of optical and electro-optical parameters

62341-5-2 © IEC:2013 – 7 –
IEC 62341-6-2:2012, Organic light emitting diode (OLED) displays – Part 6-2: Measuring

methods of visual quality and ambient performance

ISO 2206:1987, Packaging – Complete, filled transport packages – Identification of parts

when testing
ISO 2248:1985, Packaging – Complete, filled transport packages – Vertical impact test by

dropping
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62341-1-2 and the
following apply.
3.1
strength
stress at which a sample fails for a given loading condition
3.2
glass edge strength
measured stress at failure where the failure origin is known to have occurred at an edge
4 Abbreviations
FEA finite element analysis
FPCB flexible printed circuit board
B the value at lower 10 % position in the Weibull distribution [1]
TSP touch screen panel
5 Standard atmospheric conditions
The standard atmospheric conditions in IEC 62341-5:2009, 5.3, shall apply unless otherwise
specifically agreed between customer and supplier.
6 Evaluations
6.1 Visual examination and verification of dimensions

The specimen shall be submitted to the visual, dimensional checks in non-operation condition
and functional checks in operational condition prescribed by the following specification.
a) Visual checks of damage to exterior body of the specimen including marking,
encapsulation and terminals shall be examined as specified in IEC 61747-5:1998, 1.5.
b) Dimensions given in the customer’s specification shall be verified.
c) Visual and optical performance shall be checked as specified in IEC 62341-6-1.
Unless otherwise specified, visual inspection shall be performed under the conditions and
methods as specified in IEC 62341-6-2:2012, 6.2.
———————
Numbers in square brackets refer to the bibliography.

– 8 – 62341-5-2 © IEC:2013
6.2 Reporting
For the main results in each test, generally the minimum and averaged values or B value
instead of minimum value shall be reported over the number of specimens depending on the

test purposes. The relevant specification shall provide the criteria upon which the acceptance

or rejection of the specimen is to be based.

7 Mechanical endurance test methods

7.1 General
Choice of the appropriate tests depends on the type of devices. The relevant specification
shall state which tests are applicable.
7.2 Vibration (sinusoidal)
7.2.1 General
Test Fc, specified in IEC 60068-2-6 and IEC 61747-5:1998, 2.3, are applicable with the
following specific conditions. In case of contradiction between these standards,
IEC 61747-5:1998, 2.3, shall govern.
7.2.2 Purpose
The purpose of this test is to investigate the behaviour of the specimen in a vibration
environment such as transportation or in actual use.
7.2.3 Test apparatus
The equipment shall be capable of maintaining the test conditions specified in 7.2.4. The
vibration testing table should not resonate within the test condition vibration frequency range.
The required characteristics apply to the complete vibration system, which includes the power
amplifier, vibrator, test fixture, specimen and control system when loaded for testing. The
body of the device shall be securely clamped during the test. If the device has a specified
method of installation, it shall be used to clamp the device. The specimen shall be tested
under the non-operational condition.
7.2.4 Test procedure
7.2.4.1 Test conditions
7.2.4.1.1 Basic motion
The basic motion shall be a sinusoidal function of time and such that the fixing points of the
specimen move substantially in phase and in straight parallel lines.
7.2.4.1.2 Spurious motion
The maximum amplitude of spurious transverse motion at the check points in any
perpendicular to the specified axis shall not exceed 25 %. In the case of large size or high
mass specimens, the occurrence of spurious rotational motion of the vibration table may be
important. If so, the relevant specification shall prescribe a tolerance level.
7.2.4.1.3 Signal tolerance
Unless otherwise stated in the relevant specification, acceleration signal tolerance
measurements shall be performed and signal tolerance shall not exceed 5 %.

62341-5-2 © IEC:2013 – 9 –
7.2.4.1.4 Vibration amplitude tolerance

Reference point: ± 15 %;
Check point: ± 25 %.
7.2.4.1.5 Frequency tolerances

7.2.4.1.5.1 Endurance by sweeping

± 1 Hz from 5 Hz to 50 Hz;
± 2 % above 50 Hz.
7.2.4.1.5.2 Endurance at critical frequencies
± 2 %.
7.2.4.2 Severities
7.2.4.2.1 General
A vibration severity is defined by the combination of the three parameters: frequency range,
vibration amplitude and duration of endurance (in sweep cycles or time).
7.2.4.2.2 Frequency range
The frequency range shall be given in the relevant specification by selecting a lower
frequency from Table 1 and an upper frequency from Table 2.
Table 1 – Frequency range – Lower end
Lower frequency f
Hz
Table 2 – Frequency range – Upper end
Upper frequency f
Hz
– 10 – 62341-5-2 © IEC:2013
The recommended ranges are shown in Table 3.

Table 3 – Recommended frequency ranges

Recommended frequency ranges, from

f to f
1 2
Hz
5 to 100
5 to 200
5 to 500
10 to 55
10 to 200
10 to 300
10 to 500
7.2.4.2.3 Vibration Amplitude
The vibration amplitude shall be stated in the relevant specification. Recommended vibration
amplitudes with cross-over frequency are shown in Table 4.
Table 4 – Recommended vibration amplitudes
Displacement amplitude
Acceleration amplitude above the cross-over frequency
below the cross-over
frequency
g
m/s
n
mm
0,035 4,9 0,5
0,075 9,8 1,0
0,10 14,7 1,5
0,15 19,6 2,0
0,20 2,4 3,0
NOTE The values listed apply in Table 4 for cross-over frequencies between 57 Hz and 62 Hz.

7.2.4.2.4 Duration of endurance
7.2.4.2.4.1 Endurance by sweeping

The duration of the endurance test in each axis shall be given as a number of sweep cycles
chosen from the list given below.
1, 5, 10, 20, 30, 45, 60, 120
The sweeping shall be continuous and the frequency shall change exponentially with time.
The endurance time associated with number of sweep cycles or sweep rate in octaves/minute
shall be specified. During the vibration response investigation, the specimen and the vibration
response data shall be examined in order to determine critical frequencies.
7.2.4.2.4.2 Endurance at critical frequencies
The duration of the endurance test in each axis at the critical frequencies found during the
vibration response investigation shall be chosen from the list given below. This test shall be
repeated for the number of critical frequencies as specified by the relevant specification.
10 min, 15 min, 30 min, 90 min.

62341-5-2 © IEC:2013 – 11 –
7.2.5 Evaluation
After the test, visual, dimensional and functional checks shall be performed and compared as

described in 6.1.
7.3 Shock
7.3.1 General
IEC 60068-2-27 and 61747-5:1998, 2.4, shall be applied with the following specific conditions.

In case of contradiction between these standards, IEC 61747-5:1998, 2.4, shall govern.

7.3.2 Purpose
This test is to provide a standard procedure for determining the ability of an OLED panel or
module to withstand specified severities of shock. During transportation or in use, an OLED
panel or module may be subjected to conditions involving relatively non-repetitive shocks.
7.3.3 Test apparatus
The body of the specimen shall be securely clamped during the test in the test direction
aligning with the z-axis of the test machine; for example, Figure 1 depicts shock test along the
y’-direction of the specimen. If the device has a specified method of installation, it shall be
used to clamp the device.
Clamp
OLED
OLED
module
module
y′
OLED
module
y′
z
y
x′
x
z′
IEC  1686/13
a) Example of a shock test machine      b) Test direction of a specimen
Figure 1 – Configuration of OLED shock test set-up
7.3.4 Test procedure
Test Ea, specified in IEC 60068-2-27, is applicable, with the following specific requirements.
The conditions shall be selected from Table 5, taking into consideration the mass of the
device and its internal construction.

– 12 – 62341-5-2 © IEC:2013
Table 5 – Conditions for shock test

Peak amplitude A Corresponding velocity change
Corresponding duration D of the

ΔV
nominal pulse
Half-sine Trapezoidal
m/s (g ) ms m/s m/s
n
50 (5) 30 1,0 -
150 (15) 11 1,0 1,5
300 (30) 18 3,4 4,8
300 (30) 11 2,1 2,9
300 (30) 6 1,1 1,6
500 (50) 11 3,4 4,9
500 (50) 3 0,9 1,3
1 000 (100) 11 6,9 9,7
1 000 (100) 6 3,7 5,3
2 000 (200) 6 7,5 10,6
2 000 (200) 3 3,7 5,3
5 000 (500) 1 3,1 -
10 000 (1 000) 1 6,2 -
NOTE Preferred values are underlined.

The choice of waveform to be used depends on a number of factors, and difficulties inherent
in making such a choice preclude a preferred order being given in the standard (see
IEC 60068-2-27:2008, Clause A.3). The relevant specification shall state the waveform
utilized.
Unless otherwise prescribed by the relevant specification, three successive shocks shall be
applied in each direction of three mutually perpendicular axes of the specimen, for a total of
18 shocks. Depending on the number of identical devices available and the mounting
arrangements, particularly in the case of components, they may be oriented such that the
multiple axis/direction requirements of the relevant specification can be met by the application
of three shocks in one direction only (see IEC 60068-2-27:2008, Clause A.7).
7.3.5 Evaluation
Visual, dimensional and functional checks shall be performed and compared as described in
6.1 to the relevant specification.

7.4 Quasistatic strength
7.4.1 General
IEC 61747-5-3:2009, 5.4, is applicable with the following specific conditions.
7.4.2 Purpose
The objective of this standard is to establish uniform requirements for accurate and reliable
measurements of the quasistatic strength of OLED panels or modules. The quasistatic
strength of OLED module may be specified to ensure the mechanical endurance level from
the quasistatic external loadings in and around the display area in normal use, such as sitting
on the product or touching/pushing fingertip in the display area.

62341-5-2 © IEC:2013 – 13 –
7.4.3 Specimen
This standard applies to the OLED panels or modules for mobile and IT application. OLED

module products incorporating additional components, e.g. TSP, protective film and window

cover may be used as an acceptable form of the specimen. In all cases a minimum sample

size of at least 6 panels or modules shall be used to obtain a statistically significant strength
distribution representative of quasistatic resistance of the specimen to external loadings

induced by handling, processing and fabrication of the specimen specified as a part of the end

product.
F
Metal rod
Specimen
Frame with
cavity
Hard plate
IEC  1687/13
a) Boundary support with cavity b) Side support
Figure 2 – Schematic of quasistatic strength measurement apparatus example
7.4.4 Test apparatus
The quasistatic strength of a specimen is measured by supporting the specimen on the
mounting frame and loading it at the center as shown in Figure 2. The specimen shall be put
on the frame with the rectangular cavity as shown in Figure 2a) or on side supports as shown
in Figure 2b). The size of a rectangular cavity in the frame (Figure 2a)) shall be specified by
the relevant specification and shall be as big as the edge of the supporting area allows. It is
recommended to set the cavity to be around the active area size for mobile application. The
tip of metal loading bar shall be rounded in shape and the diameter of the metal rod varies
according to the specimen size under testing. It is recommended to use a metal rod of 10 mm

in diameter for the samples up to 101,6 mm (4 inches) display diagonal length. For larger
modules, such as for notebook computer or monitor applications, a rod of 19 mm diameter is
recommended. The same apparatus may also be used for loading the OLED module off-
center and obtaining its strength at different locations. For TV applications, this quasistatic
strength test is generally not applicable.
7.4.5 Test procedure
7.4.5.1 General
The displacement rate should be slow enough so that there is no significant dynamic
response from the loading such that the maximum strain rate upon specimen shall be of the

-4 -1
order of 1,0 × 10 s [3]. Typical loading rate or crosshead speed is 3 mm/min or 5 mm/min
for small size displays such that failure may occur within the measurement time of 30 s to
45 s. Depending on the purpose of the test, the following test procedure may be applied.

– 14 – 62341-5-2 © IEC:2013
7.4.5.2 Static loading resistance

For this test, a specified load is set to assess module resistance to external static load from

the relevant specification. A specified load is set and load is applied on the surface of the

specimen by lowering the metal rod as shown in Figure 2. After reaching the specified load,

the rod is set to return back to starting position. Multiple loads may be applied in steps. The
loading position of the specimen shall be the center of the active area of the display, but

multiple loading positions including off-center position may also be applied depending on the

area of interest.
7.4.5.3 Quasistatic failure load

In the continuation of the specified load test in 7.4.5.2, this test is intended to measure the
failure load. The metal rod is lowered to push the surface of the specimen until the specimen
breaks. The specimen is categorized as a failure when the applied load starts to drop by more
than a designated portion, e.g. 2 % of the peak load value.
7.4.6 Evaluation
For the static load test, the relevant specification shall provide the specified load level upon
which the acceptance or rejection of the resistance of specimen is to be based. For the failure
load test in 7.4.5.3, the average, maximum and minimum values along with failure load of
each test specimen are reported. It shall be noted in the test reporting about the specimen if it
incorporates any additional component.
7.5 Four-point bending test
7.5.1 General
This standard is established separately from IEC 61747-5-3, where the characterization of
glass component is particularly emphasized. Quasistatic strength of the edges of glass or
simply flexural strength of OLED panels and the integrity of the panel structure are assessed
in the four-point bending test configuration. Even though there is no limitation in use of four-
point bending test on the size of display panel, this test is generally applicable for mobile
applications, which is at most 101,6 mm in diagonal size.
7.5.2 Purpose
The four-point bending test is important since the result of this test can be used as an
indicator of the mechanical endurance level when either panel sample or module sample is
exposed to various mechanical loadings under hostile usage conditions, such as twisting a
handset, etc. For the purpose of this test, glasses in OLED display panels are considered
brittle and to have the property that fracture normally occurs at the surface of the glass from
the maximum tensile stress. The failure strength of display module is determined when a

weakest component in the specimen fails. Depending on the panel structure, the weakest link
could be inferior edge of glass or other failure origins, such as disintegration of sealing
material. The four-point bending test is recommended since it distributes the maximum tensile
stress over a larger volume or area in comparison to the three-point bending test.
7.5.3 Specimen
The specimen is a display panel consisting of rear and front glasses. The test specimen may
contain a polarizer; however, it is not necessary if the testing is done at production phase
where the polarizers have not yet been placed. The use of polarizer or other low elastic
modulus tape is permitted on the specimen surface to hold the cracked fragments and permit
observation of crack origin. At least 10 specimens shall be used for the purpose of estimating
the mean. A minimum of 20 specimens shall be necessary if estimates regarding the form of
strength distribution are to be reported. Unless otherwise taken for specific purpose, the
samples shall be taken from several sheets or regions of a single sheet from which the
display panels are made. Any specimen may be rejected prior to testing for defects

62341-5-2 © IEC:2013 – 15 –
considered likely to affect the quasistatic strength of the edges of glass. The variation in width

or thickness shall not exceed 5 % over the length of the specimen equal to the support span.

7.5.4 Test apparatus
7.5.4.1 Testing machine
The testing machine consists of a test frame and a four-point bending test fixture. Figure 3
illustrates an example of four-point bending test fixture with an OLED panel specimen. The

test frame consists of a vertical loading machine, which could be electromechanical, servo-

hydraulic or pneumatic driven, a load cell mounted and controller software. It is assumed that

the fixtures are relatively rigid and that most of the testing-machine crosshead travel is

imposed as strain on the specimen. There are also several requirements for a four-point
bending apparatus to be met in order to ensure reliable data with minimal variation [2].
7.5.4.2 Bearing cylinders
Cylindrical bearing edges shall be used for the support of the specimen and for the
application of the load. The bearing cylinder radius shall be approximately 2 mm to 5 mm
depending on the thickness of the specimen [3]. The cylinders shall be made of sufficiently
hardened steel to prevent excessive deformation under load and free to roll in order to relieve
frictional constraints. Moreover two loading bearings and one support bearing cylinder also
shall be provided to rotate laterally to compensate for any irregular surface contact with
specimen and to ensure uniform and even distribution of load between the two inner bearing
edges. Figure 3 shows a suitable arrangement using pinned bearing assemblies.

d d
Bearing
Panel
cylinders
front
Test
fixture
IEC  1688/13
b) Front view
a) Side view
Figure 3 – Schematics of test apparatus and pinned bearing edges

S
L
S
L
z
z
y y
x
S
S
S
S
x
L
L
IEC  1689/13
b) Y-direction bending
a) X-direction bending
Figure 4 – Specimen configuration under four-point bending test
7.5.5 Test procedure
The specimen length, L is determined as the length of either the long side or short side of the
front glass as described in Figure 4a) and Figure 4b), respectively. The amount of overhang
of the specimen, d in Figure 3 shall be at least 2 mm beyond the outer bearings to allow the

– 16 – 62341-5-2 © IEC:2013
specimen to slide over the support and to eliminate the effect of the specimen’s end condition.

Slowly apply the load at right angles to the fixture. The maximum permissible stress in the

specimen due to initial load shall not exceed 25 % of the mean strength. In four-point bending

test, a specimen is loaded at constant displacement rate until rupture. The displacement rate

to be used depends on the chosen spans and it is chosen such that the time to complete one

test cycle would be sufficiently long as described in 7.4.5.1 while times to failure for a typical

specimen range from 30 s to 45 s. In Table 6 some examples of the combinations of test
configurations and displacement rates are given.

Table 6 – Examples of test parameter combinations

Displacement rate
S (mm) S (mm)
L (mm)
S L
(mm/min)
25 20 10 3
45 40 20 5
85 80 40 10
Specifically the span between the test jig and loading rollers needs to be adjusted for a
) and load span (S ) to cover most
different specimen size with a specified support span (S
S L
part of panel edge under bending. On the other hand, to prevent the effect of bending area
size on glass edge strength and to test under the same strength criteria regardless of the
specimen sizes tested, a constant load span and support span may be specified. In any case,
the load span shall be the half of the support span [3]. The bearing cylinders shall be carefully
positioned such that the spans are accurate within ± 0,10 mm.
7.5.6 Post-testing analysis
7.5.6.1 Breakage origin analysis
Since OLED panels may have different structures for various emission mechanisms and
encapsulation schemes, potentially they may exhibit unique fracture mechanisms. And hence,
fracture origin of a specimen under four-point bending test may be different. Therefore, it is
required and important to ensure this four-point bending test method is valid for assessing the
mechanical endurance in the area of interest. Frequently, break origin analysis through
fractography is conducted to review the failure origin of the panel. Potential failure modes
include inferior edge quality, or weak integrity of adhesion material, and/or other structure
weaknesses.
7.5.6.2 Test result analysis
The mechanical testing unit used for four-point bending test reports failure load when a
specimen under the test procedures described in this test method fails. It is very important to

convert these failure load values into a standardized expression of failure stress,
...