IEC 62047-14:2012

IEC 62047-14 ®
Edition 1.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Micro-electromechanical devices –
Part 14: Forming limit measuring method of metallic film materials

Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 14: Méthode de mesure des limites de formage des matériaux à couche
métallique
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IEC 62047-14 ®
Edition 1.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Micro-electromechanical devices –

Part 14: Forming limit measuring method of metallic film materials

Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –

Partie 14: Méthode de mesure des limites de formage des matériaux à couche

métallique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 31.080.99 ISBN 978-2-88912-938-6

– 2 – 62047-14 © IEC:2012
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 5
3.1 Terms and definitions . 5
3.2 Symbols . 6
4 Testing method . 6
4.1 General . 6
4.2 Equipment . 6
4.3 Specimen . 7
5 Test procedure and analysis . 8
5.1 Test procedure . 8
5.2 Data analysis . 9
6 Test report. 10
Annex A (informative) Principles of the forming limit diagram . 11
Annex B (informative) Grid marking method . 13
Annex C (informative) Gripping method . 15
Annex D (informative) Strain measuring method . 17

Figure 1 – Equipment and tools for forming limit tests . 7
Figure 2 – Rectangular specimens with six kinds of aspect ratio . 8
Figure 3 – Strain for forming limit measurement . 9
Figure 4 – Construct the forming limit diagram by plotting the major and minor strains . 9
Figure A.1 – Forming limit diagram . 11
Figure A.2 – Hemispherical punch for forming limit measurement . 11
Figure A.3 – Grid for forming limit measurement . 12
Figure A.4 – Loading path of the specimen with various aspect ratios . 12
Figure B.1 – Procedure of a photographic grid marking method . 13
Figure B.2 – Procedure for an inkjet grid marking method . 14
Figure C.1 – Gripping of the specimen using a ring shaped die . 15
Figure C.2 – Gripping of the specimen using adhesive bonding . 16
Figure D.1 – Set up for strain measurement using digital camera . 17
Figure D.2 – Example of pixel converting image of deformed specimen . 17

Table 1 – List of letter symbols . 6

62047-14 © IEC:2012 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –

Part 14: Forming limit measuring method
of metallic film materials
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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 62047-14 has been prepared by subcommittee 47F: Micro-
electromechanical systems, of IEC technical committee 47: Semiconductor devices.
The text of this standard is based on the following documents:
FDIS Report on voting
47F/108/FDIS 47F/118/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.

– 4 – 62047-14 © IEC:2012
A list of all parts of 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 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.
62047-14 © IEC:2012 – 5 –
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –

Part 14: Forming limit measuring method
of metallic film materials
1 Scope
This part of IEC 62047 describes definitions and procedures for measuring the forming limit of
metallic film materials with a thickness range from 0,5 µm to 300 µm. The metallic film
materials described herein are typically used in electric components, MEMS and micro-
devices.
When metallic film materials used in MEMS (see 2.1.2 of IEC 62047-1:2005) are fabricated by
a forming process such as imprinting, it is necessary to predict the material failure in order to
increase the reliability of the components. Through this prediction, the effectiveness of
manufacturing MEMS components by a forming process can also be improved, because the
period of developing a product can be reduced and manufacturing costs can thus be
decreased. This standard presents one of the prediction methods for material failure in
imprinting process.
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 62047-1:2005, Semiconductor devices – Micro-electromechanical devices – Part 1:
Terms and definitions
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62047-1 and the
following apply.
3.1.1
circular grid
grid used for measuring the localized deformation of the specimens within the circle
3.1.2
grid patterns
pattern marked on the surface of the testing material permitting immediate and direct
measurement of the formability for the metallic film materials
Note 1 to entry The grid consists of a pattern of small circles or rectangles.
3.1.3
major axis
longest line of the deformed elliptical shape, which passes through both focuses of the ellipse

– 6 – 62047-14 © IEC:2012
3.1.4
minor axis
longest line of the deformed elliptical shape, which is perpendicular to the major axis
3.1.5
square grid
grid used for measuring the overall deformation of the testing material
3.2 Symbols
For the purpose of this document, letter symbols given in Table 1 are used.
Table 1 – List of letter symbols
Name and designation Letter symbol
Grid size
– initial diameter of the grid before deformation d
– diameter of the grid along the major axis after deformation d
d
– diameter of the grid along the minor axis after deformation 2

Strain
ε
– major strain 1
– minor strain ε
Equipment, tool and specimen size
– diameter of the hemispherical punch D
punch
– inner diameter of the die hole Ddie
– diameter of the bead ring D
bead
– fillet radius of the upper die edge r
de
– thickness of the testing specimen t
h
– height of the testing specimen
– width of the testing specimen w

4 Testing method
4.1 General
The forming limit diagram (FLD) is determined by pressing the micro film material using a
hemispherical punch. This pressing process is performed until the film material fractures. The
major and minor strains of a deformed specimen can be measured in many ways, for example,
by using a digital camera module or an optical device. However, using a digital camera
module with sufficient resolution and a high magnifying power lens is recommended.
NOTE See Annex A for principles of forming limit diagram.
4.2 Equipment
Micro press equipment is utilized as the loading equipment for FLD tests as described in
Figure 1. A hemispherical punch is attached to the micro press to stretch the film material to
measure the forming limits of the specimen. Conventional hard chrome coating to the punch
surface using hexavalent chromium is recommended to guarantee a surface roughness less
than 0,8 µm (RMS: Root Mean Square). In addition, lubricants such as graphite can be
applied for reducing the friction force between the surfaces of the punch and the specimen.
The movement of the punch is controlled by a constant crosshead speed of the measuring
devices in the micro press. The punch speed shall be lowered to the quasi-static condition. A
punch speed of less than 20 µm/s is recommended in order not to result in the dynamic inertia

62047-14 © IEC:2012 – 7 –
effect during the test. Although the dimension of the hemispherical punch and the test
samples can be varied with forming product and inspected measuring region, it is
recommended that the dimension should be determined as the following ratio.
D = D + 2,5t (1)
die punch
D = 2 × D (2)
bead punch
It is also recommended that the hemispherical punch diameter and the die edge radius should
be 5 mm and 0,5 mm respectively.

D
Dbead
bead
D
Ddie
die
1 1
1 1
r
de
r
de
3 33
2 2
2 2
DD
ppununcchh
IEC  200/12
Key
1 upper die
2 lower die
3 specimen
4 hemispherical punch
Figure 1 – Equipment and tools for forming limit tests

4.3 Specimen
Rectangular specimens with different aspect ratios shall be used in the test. At least six kinds
of specimens with the aspect ratios of 1,0, 1,5, 1,75, 2,0, 3,5 and 7,0 are recommended as
shown in Figure 2 in order to cover the various loading paths on the domain of the forming
limit diagram.
h = 2,5 × D (3)
punch
– 8 – 62047-14 © IEC:2012
Specimen height (h)
Aspect ratio =
Specimen width (w)
w
h
1 1,5 1,75 2 3,5 7
IEC  201/12
Figure 2 – Rectangular specimens with six kinds of aspect ratio
Grids shall be marked to the surface of the testing sample to measure the localized and
overall deformation of the film material. The grid consists of a pattern of small circles or
rectangles. It is recommended to arrange the grid patterns with an interval range from 50 µm
to 200 µm and that the thickness of the grid is less than 10 % of the specimen thickness.
NOTE See Figure A.3 for detailed grid pattern.
5 Test procedure and analysis
5.1 Test procedure
In a FLD test, the following items from a) to e) are steps to obtain a localized fracture of a
specimen which is firstly observed. Then the values of a major strain and a minor strain which
are used to quantify the deformation of the specimen will be measured.
a) Preparation of the specimen
Specimens with different aspect ratios are prepared to conduct the test.
NOTE 1 Both the positive and negative region of the FLD curve can be obtained by varying the aspect ratio of
the specimen and the lubricant.
b) Grid marking on the specimen
Appropriate marking conditions which have a lesser effect on the microstructure and the
properties of materials should be applied in the grid marking since the thickness of the film
is relatively smaller.
NOTE 2 See Annex B for detail expression of several grid marking methods.
c) Gripping the specimen
In order to measure the strain only in the testing region, it is important that the sample
should be clamped without any sliding. Also, pre-fracture should not occur when it is being
clamped.
NOTE 3 See Annex C for several recommended gripping methods.
d) Moving the punch until the specimen fails
The hemispherical punch moves by controlling the constant crosshead speed of
equipment until the localized fracture of the specimen is first observed.
e) Measuring the major and minor strains of deformed specimen
Major and minor strains of the deformed specimen are measured representatively using
the digital camera module with a high magnifying power lens. The recommended
magnification factor of the camera lens is less than 5 µm/pixel in order to measure the
strain precisely.
NOTE 4 See Annex D for strain measuring method.
f) Construct the FLD by plotting the measured major and minor strains (refer to Figure 4).

62047-14 © IEC:2012 – 9 –
5.2 Data analysis
In order to quantify the deformation of the specimen, two kinds of strains – major and minor
strains – are measured between the initial state of the circle and the deformed elliptical shape.
After the circular grid deforms, the longest dimensions of the ellipse is major axis and the
dimension perpendicular to the major axis is the minor axis, as explained in Figure 3.
Minor axis
Minor Axis
Major axis
Major Axis
IEC  202/12
Figure 3 – Strain for forming limit measurement
The major strain, ε , and the minor strain, ε , are calculated with following equations:
1 2
d
ε = ln (4)
d
d
ε = ln (5)
d
Here, d is the initial diameter of the circular grid while d and d represent the major and the
0 1 2
minor diameters of the grid after deformation.
MaMajjoorr s stratraiinn ε εε   [(%)% ]
11 2
-40 -30 -20 -10 0 10 20 30 40
Minor strain  εε   [%]
Minor strain ε (%22 )
IEC  203/12
Key
1 fracture
2 good
3 failure
Figure 4 – Construct the forming limit diagram
by plotting the major and minor strains

– 10 – 62047-14 © IEC:2012
The major and minor strains calculated from the grids in the neighbourhood of the failure zone
of the specimen are regarded as critical failure strains. By conducting a series of experiments
with various specimens, it is possible to find combinations of major strain and minor strain for
which neither necking nor fracture occurs by plotting on the strain domain. The diagram
plotting the combinations of major and minor strains is a forming limit diagram as shown in
Figure 4.
6 Test report
The test report should contain at least the following information:
a) reference to this international standard;
b) testing material;
c) grid marking method;
d) number of specimens used in the test;
e) dimensions of the specimen(s);
f) description of testing apparatus (punch diameter, gripping method, punch roughness,
etc.);
g) lubrication condition;
h) crosshead speed of testing apparatus;
i) strain measurement module: specification of the digital camera, scale factor of each pixel;
j) measured diameters and calculated strains of each specimen;
k) forming limit diagram.
62047-14 © IEC:2012 – 11 –
Annex A
(informative)
Principles of the forming limit diagram

The maximum major and minor strains at fracture are plotted in the strain domains. The
surface of metallic film material part deforms differently based on the type of loading. A
relationship exists between the deformation of the film material and the type of stressing. By
conducting a series of experiments, it is possible to find combinations of maximum strain
(corresponding to the major axis of the ellipse) and minimum strain (perpendicular to the
major strain and corresponding to the minor axis of the ellipse) for which neither necking nor
fracture occurs. The FLD is valid for a definite formability and defines two zones “good” and
“failure”. The strains plotted are the critical points, where cracks are likely to form. Between
the two zones of “good” and “failure”, there is a curve of critical deformation shown in
Figure A.1
εε
MajMorajor s straitrain n  ε   [ (%%) ]
-40 -30 -20 -10 0 10 20 30 40
Minor strain ε (%)
εε
Minor strain    [%]
IEC  204/12
Key
1 good zone
2 failure zone
Figure A.1 – Forming limit diagram
Forming limit diagrams can be obtained by conducting experiments for different zones. The
most widely used method of obtaining the forming limit diagram is by means of drawing tests
of the specimens with a hemispherical punch shown in Figure A.2.

IEC  205/12
Figure A.2 – Hemispherical punch for forming limit measurement

– 12 – 62047-14 © IEC:2012
In order to evaluate the deformation behaviour and forming limits of metallic thin film, grid
patterns are marked on the specimen. This permits immediate and direct measurement of the
formability of the metallic thin film at any location. The grid consists of a pattern of small
circles and rectangles as described in Figure A.3

IEC  206/12
Figure A.3 – Grid for forming limit measurement
Circular grid patterns on the surface of a film material part deform differently based on the
type of loading. The different stress conditions are simulated by changing the width of the
specimen. The specimens with various widths are drawn until cracks occur. With details from
these tests, the FLD can be obtained for strain paths ranging from biaxial tension (stretch
forming) to equal tension and compression (deep drawing) as explained in Figure A.4. The
diagram shall be determined for each particular film material.
Major strain ε (%)
Major strain εε [%]
Aspect ratio = 7
Aspect ratio = 1
aspect ratio = 7 aspect ratio = 1
εε ==−−εε εε ==εε
ε = ε
1 2
11ε = –ε 22 11 22
1 2
-40 -30 -20 -10 0 10 20 30 40
Minor strain ε (%)
Minor strain  εε   [%2 ]
IEC  207/12
Figure A.4 – Loading path of the specimen with various aspect ratios

62047-14 © IEC:2012 – 13 –
Annex B
(informative)
Grid marking method
B.1 General
Photographic and inkjet methods are typical grid marking methods. The photographic method
can achieve very small-sized grid marking through its precise processing, but there are
disadvantages such as complex, slow work. The inkjet method has merits such as simplicity
and quickness. However there are limits to precision work. The procedures and concepts for
each method are as follows.
B.2 Photographic method
a) Deposit the photographic sensitive materials on the specimen;
b) Expose the photographic sensitive materials using a photo-mask;
c) Clean the specimen (refer to Figure B.1).
IEC  208/12
Key
1 dark room
2 photographic sensitive materials
3 specimen
4 light
5 photo mask
Figure B.1 – Procedure of a photographic grid marking method

– 14 – 62047-14 © IEC:2012
B.3 Inkjet method
a) Place the specimen on the hot plate and inkjet machine;
b) Carry out the inkjet process according to the grid marking tool path data (refer to Figure
B.2).
IEC  209/12
Key
1 specimen
2 hot plate
Figure B.2 – Procedure for an inkjet grid marking method

62047-14 © IEC:2012 – 15 –
Annex C
(informative)
Gripping method
C.1 Bead method
Figure C.1 shows the gripping method using ring shaped dies composed respectively of the
female and male beads in the upper and lower dies. Also, the detailed dimensions of the bead
parts are recommended. These dimensions can be modified if they satisfy the no slip
conditions of the specimen.
2√3 × t
22 33××tt
0,5 t
0,5t
0,5 t
0,5t
t
t
0,5 t
0,5t
0,5t
0,5 t
0,0,5 5tt
IEC  210/12
Key
1 upper die
2 lower die
3 specimen
4 hemispherical punch
5 female bead
6 male bead
Figure C.1 – Gripping of the specimen using a ring shaped die

– 16 – 62047-14 © IEC:2012
C.2 Bonding method
As shown in Figure C.2, a gripping method using adhesive bonding can be adopted in the test.
Either upper or lower adhesive can be used if they satisfy the no slip condition. At this point, it
should be ensured that the adhesive does not invade the round part of the upper die edge.
Additionally, it is recommended that the upper and lower thicknesses of the adhesive layer
respectively should not exceed 10 % of the specimen thickness.
a
IEC  211/12
Key
1 upper die
2 lower die
3 specimen
4 adhesive
5 specimen with adhesive
NOTE Figure C.2 illustrates the bonding method.
a
It shall be ensured that the round part of the edge is not invaded.
Figure C.2 – Gripping of the specimen using adhesive bonding

62047-14 © IEC:2012 – 17 –
Annex D
(informative)
Strain measuring method
Major and minor strains of the deformed specimen can be measured representatively using
the digital camera module with a high magnifying power lens. As shown in Figure D.1, the
digital camera module shall be located so that the line of sight is perpendicular to the surface
of the deformed specimen. Alternatively, the digital camera is fixed and the deformed
specimen can be moved. The image captured from the digital camera shall be converted to
real scale data by the pixel calculating algorithm described in Figure D.2. Manual calculation
of the strains can be adopted, but using a software which can calculate the strains would be
convenient. The detailed step-by-step procedure for the strain measurement is as follows.
Step 1. Install the high magnified digital camera over the deformed specimen so that the
screen displayed from the camera including the grid pattern of the specimen can be
observed clearly.
Step 2. Manipulate the software so that one or more grid patterns on the region of interest
of the deformed specimen appear(s) on the monitor.
Step 3. Concerning the corresponding ellipse, calculate the major and minor deformations
by counting the pixels.
IEC  212/12
Key
1 deformed specimen
2 high magnified digital camera
Figure D.1 – Set up for strain measurement using digital camera

8 (pixel)
8 [pixel]
Initial diameter (µm) =
Initial diameter [µm] =
magnification factor [pixel/µm]
Magnification factor (pixel/µm)
8 (pixel)
Minor 8 [pixel]
Minor
axis
Major deformation (µm)
...