IEC 62137-1-4:2009

IEC 62137-1-4
Edition 1.0 2009-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Surface mounting technology – Environmental and endurance test methods for
surface mount solder joint –
Part 1-4: Cyclic bending test
Technologie de montage en surface – Méthodes d’essais d’environnement et
d’endurance des joints brasés montés en surface –
Partie 1-4: Essai de flexion cyclique

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IEC 62137-1-4
Edition 1.0 2009-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Surface mounting technology – Environmental and endurance test methods for
surface mount solder joint –
Part 1-4: Cyclic bending test
Technologie de montage en surface – Méthodes d’essais d’environnement et
d’endurance des joints brasés montés en surface –
Partie 1-4: Essai de flexion cyclique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 31.190 ISBN 978-2-88910-627-1
– 2 – 62137-1-4 © IEC:2009
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .6
3 Terms and definitions .6
4 Test equipment and material .6
4.1 Test equipment for cyclic bending .6
4.2 Test substrate .7
4.3 Solder alloy .7
4.4 Solder paste.7
4.5 Reflow soldering equipment .7
4.6 Surface mount component for testing .7
5 Mounting method.7
6 Test conditions .8
6.1 Pre-treatment .8
6.2 Test procedures .8
6.3 Judging criteria.9
7 Items to be included in the test report.9
8 Items to be prescribed in the product specifications.9
Annex A (normative) Cyclic bending test equipment.11

Figure 1 – Image drawing on evaluation area of joint strength.5
Figure 2 – Typical reflow soldering profile.8
Figure A.1 – Sample structure of substrate bending jig .12
Figure A.2 – Sample structure of cyclic bending strength test .13

62137-1-4 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
SURFACE MOUNTING TECHNOLOGY –
ENVIRONMENTAL AND ENDURANCE TEST METHODS
FOR SURFACE MOUNT SOLDER JOINT –

Part 1-4: Cyclic bending test
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
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agreement between the two organizations.
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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 62137-1-4 has been prepared by IEC technical committee 91:
Electronics assembly technology.
The text of this standard is based on the following documents:
FDIS Report on voting
91/815/FDIS 91/835/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 – 62137-1-4 © IEC:2009
A list of all parts of the IEC 62137 series, under the general title Surface mounting
technology – Environmental and endurance test methods for surface mount solder joint, can
be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
62137-1-4 © IEC:2009 – 5 –
SURFACE MOUNTING TECHNOLOGY –
ENVIRONMENTAL AND ENDURANCE TEST METHODS
FOR SURFACE MOUNT SOLDER JOINT –

Part 1-4: Cyclic bending test
1 Scope
The test method described in this part of IEC 62137 applies to surface mount components
with a thin and wide basal plane, such as QFP and BGA. This test method evaluates the
endurance of the solder joints between component leads and lands on a substrate by cyclic
bending of substrate.
This test also evaluates the effects of repeated mechanical stress, such as key pushing in cell
phones, the strength of the solder joint between component terminals and lands on a
substrate.
In this test method, the evaluation requires first to mount the surface mount component on the
substrate by reflow soldering, then cyclically bend the substrate to a certain degree of depth
until fracture of the solder joints occurs. The properties of the solder joints (e.g, solder alloy,
substrate, mounted device or design, etc.) are evaluated to assist in improving the strength of
the solder joints.
Component
lead
Component lead
Enlarge
Solder Plated layers
Evaluation area
Intermetallic compound
layers
Substrate
Substrate land
Substrate
IEC  1174/07
Figure 1 – Image drawing on evaluation area of joint strength

– 6 – 62137-1-4 © IEC:2009
2 Normative references
The following referenced documents are indispensable for the application 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 60068-1, Environmental testing – Part 1: General and guidance
IEC 60194, Printed board design, manufacture and assembly – Terms and definitions
IEC 61188-5 (all parts 5), Printed boards and printed board assemblies – Design and use –
Part 5: Attachment (land-joint) considerations
IEC 61190-1-2, Attachment materials for electronic assembly – Part 1-2: Requirements for
soldering pastes for high-quality interconnects in electronics assembly
IEC 61190-1-3, Attachment materials for electronic assembly – Part 1-3: Requirements for
electronic grade solder alloys and fluxed and non-fluxed solid solders for electronic soldering
applications
IEC 61249-2-7, Materials for printed boards and other interconnecting structures – Part 2-7:
Reinforced base materials clad and unclad – Epoxide woven E-glass laminated sheet of
defined flammability (vertical burning test), copper-clad
IEC 61760-1, Surface mounting technology – Part 1: Standard method for the specification of
surface mounting components (SMDs)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60194, IEC 60068-1
and IEC 61249-2-7 as well as the following apply.
3.1
cyclic bending strength
intensity of the strength, which is expressed in the number of cycles to attain the joint fracture
between surface mount component terminals mounted on the printed board and the copper
land of the substrate after bending the substrate cyclically to a certain degree to allow the
surface of the component side of the board to become a convex shape
3.2
displacement rate
moving velocities of the indenter when cyclically bending the substrate
3.3
displacement range
distance from the initial test position at the centre of the substrate to the maximum indentation
caused by pushing the indenter down and by pulling it back
4 Test equipment and materials
4.1 Test equipment for cyclic bending
The equipment for cyclic bending tests consists of a tension compression testing machine,
substrate bending jigs, a resistance measuring instrument and a recorder. The specifications
shall comply with those of the cyclic bending test equipment described in Annex A.

62137-1-4 © IEC:2009 – 7 –
4.2 Test substrate
Unless otherwise prescribed by the relevant product specifications, the test substrate shall
meet the following conditions:
a) Material: Epoxide woven, glass fabric, copper-clad laminated sheet, general purpose
grade (see IEC 61249–2-7), with foil bonded to one side and a nominal thickness of the
sheet, including the metal foil, of 1,6 mm with a tolerance of ±0,20 mm. The copper foil
should have a thickness of 0,035 mm ± 0,010 mm.
b) Size: The size of the substrate depends on the size and shape of a surface mount device
soldered on the substrate. The substrate shall be able to be fastened to the pull test
equipment.
c) Land geometry: The shape and size of a land shall comply with the IEC 61188-5 series or
the pad geometry recommended by the respective component supplier.
d) Surface protection: The solderable areas of the substrate (lands) shall be protected
against oxidization by suitable means, for example by an organic surface protection layer
(OSP). This protective layer shall not adversely effect the solderability of the lands under
the soldering conditions of the reflow soldering equipment.
4.3 Solder alloy
Unless otherwise specified, the solder alloy shall consist of a ternary composition of Sn, Ag
and Cu with the Ag content ranking from 3,0 % to 4,0 % by weight and the Cu content ranking
from 0,5 % to 1,0 % by weight with Sn for balance, for example SnAg3,0Cu0,5. The solder
alloy shall be in accordance with IEC 61190-1-3.
4.4 Solder paste
Unless otherwise stated in the relevant product specifications, solder paste should be chosen
from IEC 61190-1-2. However, the solder to be used shall be the one specified in 4.3 above.
4.5 Reflow soldering equipment
Unless otherwise prescribed by the relevant product specifications, reflow-soldering
equipment should be the one that can realize the temperature profile as shown in Figure 2.
4.6 Surface mount component for testing
Unless otherwise prescribed by the relevant product specifications, the surface mount
component shall have the structure that enables the measurement of electrical resistance (for
example, daisy chain).
NOTE In connecting a daisy chain, care should be given to prevent breaking the wiring pattern, such as by
drawing the wiring pattern forth from a shorter rather than a longer direction of the board.
5 Mounting method
Unless otherwise prescribed by the relevant product specifications, the surface mount
component shall be mounted on the substrate in the following sequence:
a) Apply the solder paste specified in 4.4 to the lands of a test substrate as specified in 4.2,
using a stainless steel mask that has openings of the same size, shape and configuration
as the lands as specified in 4.2 c) with a thickness of 100 μm to 150 μm.
b) Mount the test specimen on the test substrate with the printed solder paste.
c) Perform soldering using the reflow soldering equipment specified in 4.5 and the solder
paste specified in 4.4 under the following conditions: typical temperature profile of reflow
soldering is given in Figure 2 and as proposed in IEC 61760-1; the temperature shall be
measured at the land.
– 8 – 62137-1-4 © IEC:2009
SnAgCu Reflow
250 °C
245 °C
235 °C
220 °C
180 °C
Preheating
ca 45 s … 90 s > 220 °C
150 °C
Typical
Ramp down rate < 6 k/s
Ramp up rate < 3 k/s
0 30 60 90 120 150 180 210 240 270 300 330 360
Time  s
Continous line: typical process (terminal temperaure)
Dotted line: process limits. Bottom process limit (terminal temperature). Upper process limit (top surface temperature)
IEC  1176/07
Figure 2 – Typical reflow soldering profile
6 Test conditions
6.1 Pre-treatment
Unless otherwise stated in the relevant product specifications, the specimen shall be left
under standard atmospheric conditions, as specified in IEC 60068-1, for 4 h or more.
6.2 Test procedures
Unless otherwise stated in the relevant product specifications, the following procedures
should be followed:
a) Fix the test substrate to the substrate bending jig in the following order:
1) First, solder the lead-wires to the terminals (daisy chain) used for monitoring electrical
resistance on the substrate, and then connect the wires to a momentary interruption
detector.
2) Make sure that the centre of the support jigs is evenly spaced (45 mm ± 0,5 mm) apart
from the centre of the indenter.
3) Mount the substrate on the support jigs with the face down of the surface mount
component side. Adjust the position to allow the indenter to push into the central part
of the substrate.
4) Install anti-displacement jigs at both sides of the substrate, leaving no space between
in order to prevent the indenter from pushing down off the centre of the substrate.
5) Make sure that the indenter is at the centre position by having it in contact with the
substrate.
NOTE To ensure that the indenter is going down to the centre position of the substrate and that the
indenter is in contact with the substrate, keep pushing the substrate until a force of 1 N ± 0,1 N is applied.
b) Displacement rate and allowable displacement range shall be set as follows:
Temperature  °C
62137-1-4 © IEC:2009 – 9 –
1) The displacement rate shall be 0,5 mm/s (30 mm/min) which is the moving rate of the
indenter to push the central part of the substrate.
2) Allowable displacement range (maximum bending depth) shall be determined by
conducting preliminary tests for each type of surface mount component and thereby
selecting the conditions in which joint fracture can be initiated with the cyclic number of
several thousands. However, the selection should be limited within 1 mm to 4 mm.
c) Continue cyclic bending strength tests at each level mainly in the selected range until the
electrical resistance-measuring instrument can detect occurrence of electric continuity
interruption in the specimen. Make a record of the number of cycles when fracture occurs.
d) Make analytical observations of the fractured part as needed, verify the fracture mode and
record it.
6.3 Judging criteria
When a momentary interruption detector can detect that electrical continuity interruption has
occurred in the specimen, this is judged as a failure.
7 Items to be included in the test report
When a test report is required, agreement shall be made between the reporting party and the
recipient on the selection of reporting items from the following:
a) Test date
b) Location of the test organization
c) Name of the electronic component, type, size, body dimensions and lead pitch
d) Base materials of lead on electronic components; with or without plating, and materials of
plating
e) Materials of the test substrate, dimensions and layer structure
f) Measurements of the land on the substrate and materials for the surface treatment
g) Type of solder and type of solder paste
h) Temperature profile of reflow soldering and soldering ambience (for the case of a nitrogen
ambient atmosphere, oxygen concentration should apply)
i) Model of the tensile and compression machine
j) Details of the substrate bending jig (drawing is preferable.)
k) Specifications of the electrical resistance-measuring instrument
l) Specifications of the recorder
m) Displacement rate
n) Displacement range and the number of cycles to fracture initiation
o) Fracture mode (photos, etc.)
NOTE Solder joint geometry may affect the performance in this test.
8 Items to be given in the product specifications
The following items shall be included:
a) Test substrate (4.2)
b) Solder alloy (4.3)
c) Solder paste (4.4)
d) Reflow soldering equipment (4.5)
e) Specimens (4.6)
– 10 – 62137-1-4 © IEC:2009
f) Mounting method (5.1)
g) Pre-treatment (6.1)
h) Test procedures (6.2)
62137-1-4 © IEC:2009 – 11 –
Annex A
(normative)
Cyclic bending test equipment
A.1 Application
Annex A applies to the test equipment for substrate bending strength specified in 4.1 and
specifies the requirements.
A.2 Cyclic bending test equipment
Unless otherwise specified by the relevant product specifications, the cyclic bending test
machine should be able to meet the following requirements.
A.2.1 Tension compression testing machine
The machine shall have the following characteristics:
a) It shall be capable of pushing the indenter to the prescribed displacement (0,5 mm to
5 mm) with the use of triangular waves at the prescribed speed (0,5 mm/s) and after this,
pulling the indenter back to the initial position at the same speed. This test machine also
needs the capability of repeating this activity. Precision of displacement measurement
should be ±1 % of the indication on the test machine (set values) and cyclic precision
should be ±2 %.
NOTE As the test is effective with sine waves in place of triangular waves, the test machine should also be
able to function with sine waves.
b) The test machine should be able to measure elapsed time and the forces applied to the
test substrate in the course of testing.
c) The test machine should be able to shut down when receiving signals from the electrical
resistance-measuring instrument.
A.2.2 Substrate bending jig
The substrate bending jigs should be able to support the substrate with the face down of the
component side of the printed circuit board, push the centre of the substrate down with the
indenter, and then pull the indenter back. Unless otherwise specified by the relevant product
specifications, these jigs shall meet the following conditions:
The structure shall be as indicated in Figure A.1.

– 12 – 62137-1-4 © IEC:2009
Indenter
Substrate
Support
tool
Support jig (flexible clamp
for printed wiring boards)
IEC  2235/08
Figure A.1 – Sample structure of substrate bending jig
a) Material: Steel
NOTE Steel of high strength is recommended to prevent deformation due to application of cyclic bending.
b) Indenter
The indenter has a radius of 3 mm ± 0,2 mm with the structure that can clip the central part of
the substrate from front to back on both sides. This structure shall prevent the substrate from
distorting after a certain time in the direction that the indenter pushes during the cyclic
bending test; it shall also be able to pull the substrate back to the initial test position.
c) Support jig
The support jig has a radius of 3 mm ± 0,2 mm. Its structure shall be such that both ends of
the substrate can be clipped from front to back on both sides to pull the substrate back to the
initial test position. However, it should not be too tightly constrained, in that it uses head
knocking type rollers on the upper side (see Figure A.1).
d) The distance between the support jigs is 90 mm ± 1 mm.
e) The displacement range (distance between the initial position of the substrate and the
lowest position of the substrate).
Displacement range is 0,5 mm to 5 mm and the test machine needs to have the structure
to function under this condition.
A.2.3 Electrical resistance measuring instrument
The electrical resistance measuring instrument should have the mechanism to verify electrical
continuity and discontinuity on the test substrate and to be able to judge an interruption when
the resistance value exceeds 1 × 10 Ω. In
...