IEC 60068-2-21:2006

IEC 60068-2-21 ®
Edition 6.0 2006-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-21: Tests – Test U: Robustness of terminations and integral mounting
devices
Essais d’environnement –
Partie 2-21: Essais – Essai U: Robustesse des sorties et des dispositifs de
montage incorporés
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IEC 60068-2-21 ®
Edition 6.0 2006-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-21: Tests – Test U: Robustness of terminations and integral mounting
devices
Essais d’environnement –
Partie 2-21: Essais – Essai U: Robustesse des sorties et des dispositifs de
montage incorporés
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 19.040; 31.190 ISBN 978-2-88912-734-4

– 2 – 60068-2-21  IEC:2006
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Test Ua : tensile . 7
3.1 Object . 7
3.2 General description . 7
3.3 Preconditioning . 7
3.4 Initial measurements . 7
3.5 Test method . 7
3.6 Final measurements . 8
3.7 Information to be given in the relevant specification . 8
4 Test Ua : thrust . 9
4.1 Object . 9
4.2 General description . 9
4.3 Preconditioning . 9
4.4 Initial measurements . 9
4.5 Test method . 9
4.6 Final measurements . 10
4.7 Information to be given in the relevant specification . 10
5 Test Ub: bending . 10
5.1 Object . 10
5.2 General description . 11
5.3 Preconditioning . 11
5.4 Initial measurements . 11
5.5 Test method . 11
5.6 Final measurements . 13
5.7 Information to be given in the relevant specification . 14
6 Test Uc: torsion . 14
6.1 Object . 14
6.2 Preconditioning . 14
6.3 Initial measurements . 14
6.4 Test method . 14
6.5 Final measurements . 15
6.6 Information to be given in the relevant specification . 15
7 Test Ud: torque . 15
7.1 Object . 15
7.2 General description . 15
7.3 Preconditioning . 15
7.4 Initial measurements . 15
7.5 Test method . 16
7.6 Final measurements . 16
7.7 Information to be given in the relevant specification . 16

60068-2-21  IEC:2006 – 3 –
8 Test Ue: robustness of terminations for SMD in the mounted state . 17
8.1 Object . 17
8.2 General description . 17
8.3 Mounting . 18
8.4 Initial measurements . 19
8.5 Test methods . 19
8.6 Final measurements . 21
8.7 Information to be given in the relevant specification . 22

Figure 1 – Clamp for the testing of short terminations . 13
Figure 2 – Sketches showing direction by arrow heads of application of forces
Test Ua : tensile and test Ua : thrust . 23
1 2
Figure 3 – Sketches showing test procedure for test Ub: bending (see 5.5.2.1 and 5.5.2.3) . 24
Figure 4 – Diagrams showing test procedure for test Uc: torsion test for wire terminations. 25
Figure 5 – Example of substrate for test method Ue (also suitable for electrical test) . 26
Figure 6 – Example of substrate for test methods Ue and Ue
2 3
(also suitable for electrical test) . 26
Figure 7 – Bending jig for test Ue . 27
Figure 8 – Example of a push-off test substrate . 27
Figure 9 – Force test Ue – pull-off . 28
Figure 10 – Example of a force application pushing tool for test Ue – push-off . 28
Figure 11 – Example of the shear (adhesion) test – Ue . 28
Table 1 – Application . 6
Table 2 – Value of applied force for test Ua . 8
Table 3 – Value of applied force for test Ua . 10
Table 4 – Value of applied force for test Ub . 12
Table 5 – Torque severity . 16

– 4 – 60068-2-21  IEC:2006
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-21: Tests – Test U: Robustness of terminations
and integral mounting devices
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
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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
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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 60068-2-21 has been prepared by IEC technical committee 91:
Electronics assembly technology.
This sixth edition cancels and replaces the fifth edition, published in 1999, and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition
– Addition of torque severity for nominal thread diameter of 8 mm in Test Ud: torque in
accordance with IEC 60252-2 (see table 5)
– Modification of substrate specification and mounting method describing lead-free solder in
Test Ue (see Figure 5 and 8.3.3 et al.)

60068-2-21  IEC:2006 – 5 –
– Modification of test jig and test condition in Test Ue : substrate bending test (see Figure 7
et al.)
– Change of pushing force from 10 N to 5 N in Test Ue : shear test (see 8.5.3.2)
This bilingual version corresponds to the monolingual English version, published in 2006-06.
The text of this standard is based on the following documents:
FDIS Report on voting
91/582/FDIS 91/607/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.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A complete list of all parts comprising the IEC 60068 series, under the general title
Environmental testing, 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.
The contents of the corrigendum of January 2012 have been included in this copy.

– 6 – 60068-2-21  IEC:2006
ENVIRONMENTAL TESTING –
Part 2-21: Tests – Test U: Robustness of terminations
and integral mounting devices
1 Scope
This part of IEC 60068 is applicable to all electrical and electronic components whose
terminations or integral mounting devices are liable to be submitted to stresses during normal
assembly or handling operations.
Table 1 provides details of the applicable tests.
Table 1 – Application
Test Type Component Mounted/not mounted
Ua Tensile Leaded devices Not mounted
Ua Thrust Leaded devices Not mounted
Ub Bending Leaded devices Not mounted
Uc Torsion Leaded devices Not mounted
Ud Torque Threaded stud or screw termination Not mounted
Ue Bending Surface mounted devices Mounted
Ue Pull/push Surface mounted devices Mounted
Ue Shear Surface mounted devices Mounted
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 60068-1:1988, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
IEC 60068-2-20:1979, Environmental testing – Part 2: Tests – Test T: Soldering
Amendment 2 (1987)
IEC 60068-2-58:2004, Environmental testing – Part 2-58: Tests – Test Td – Test methods for
solderability, resistance to dissolution of metallization and to soldering heat of surface
mounting devices (SMD)
IEC 60068-2-61:1991, Environmental testing – Part 2: Tests – Test Z/ABDM: Climatic
sequence
IEC 61249-2-7:2002, 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 61188-5 (all parts), Printed boards and printed board assemblies – Design and use
IEC 61190-1-2:2002, Attachment materials for electronic assembly – Part 1-2: Requirements
for soldering pastes for high quality interconnections in electronics assembly

60068-2-21  IEC:2006 – 7 –
IEC 61191-2:1998, Printed board assemblies – Part 2: Sectional specification – Requirements
for surface mount soldered assemblies
ISO 272:1982, Fasteners – Hexagon products – Widths across flats
ISO 9453:1990, Soft solder alloys – Chemical compositions and forms
3 Test Ua : tensile
This test is applicable to all types of terminations.
3.1 Object
The purpose of this test is to verify that the terminations and attachment of the terminations to
the body of the component will withstand such axial stresses as are likely to be applied during
normal assembly or handling operations.
3.2 General description
With the termination in its normal position and the component held by its body, a force is
applied to the termination in the direction of its axis and acting in a direction away from the
body of the component. The force shall be applied progressively (without any shock) and then
maintained for a period of 10 s ± 1 s.
3.3 Preconditioning
The method of preconditioning shall be as prescribed in the relevant specification.
3.4 Initial measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
3.5 Test method
Unless otherwise specified in the relevant specification, the test method shall be as follows:
Refer to Figure 2a.
3.5.1 Application
This test applies to all types of terminations. It shall be carried out on all the terminations,
except where a component has more than three terminations, in which case the specification
shall state the number of terminations per component to be tested. The test shall be carried
out in such a manner that all the terminations of the component have an equal probability of
being subjected to test.
3.5.2 Procedure
With the termination in its normal position and the component held by its body, a force with a
value as stated in Table 2 shall be applied to the termination in the direction of its axis and
acting in a direction away from the body of the component. The force shall be applied
progressively (without any shock) and then maintained for a period of 10 s ± 1 s.

– 8 – 60068-2-21  IEC:2006
The value of the applied force is as follows:
a) Wire terminations (circular section or strip) or pins
The value of the force applied shall be that indicated in Table 2.
Insulated wires shall be stripped of the insulation at the point at which the load is applied.
Stranded wires shall be united mechanically at the point of application of the load (such as
by soldering or knotting), prior to the application of the load. Where the technical features
of insulated or stranded wires may give rise to difficulties during the stripping, joining or
knotting operations and be liable to cause dispute for the test results, such operations
shall be in accordance with the relevant specification or, where necessary, with the
instructions of the component manufacturer.
Table 2 – Value of applied force for test Ua
a
Nominal cross-sectional area (S) Corresponding diameter (d) for Force with tolerance of ±10 %
circular-section wires
mm mm N
s ≤ 0,05      d ≤ 0,25 1
0,05 < s ≤ 0,10 0,25 < d ≤ 0,35 2,5
0,10 < s ≤ 0,20 0,35 < d ≤ 0,50 5
0,20 < s ≤ 0,50 0,50 < d ≤ 0,80 10
0,50 < s ≤ 1,20 0,80 < d ≤ 1,25 20
s > 1,20      d > 1,25 40
a
For circular-section wires, strips or pins, the nominal cross-sectional area is equal to the value calculated
from the nominal dimension(s) given in the relevant specification. For stranded wires, the nominal cross-
sectional area is obtained by taking the sum of the cross-sectional areas of the individual strands of the
conductor specified in the relevant specification.

b) Other terminations (tag terminations, threaded studs, screws, terminals, etc.)
The value of the force to be applied shall be given in the relevant specification.
3.6 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
3.7 Information to be given in the relevant specification
Subclause
a) Method of preconditioning 3.3
b) Initial measurements 3.4
c) Number of terminations to be tested, if more than three 3.5.1
d) Force (for oversized and other terminations) 3.5.2
e) Details of stripping, joining or knotting operations, if necessary 3.5.2
f) Final measurements 3.6
60068-2-21  IEC:2006 – 9 –
4 Test Ua : thrust
4.1 Object
The purpose of this test is to verify that the terminations and attachment of the terminations to
the body of the component will withstand such thrusts as are likely to be applied during
normal assembly or handling operations. This test applies only to specimens of small
dimensions and of low mass, to the exclusion of equipment and assemblies.
NOTE This test does not apply to flexible terminations. The tests for flexible terminations are given in a) and b)
of 5.1.
4.2 General description
With the termination in its normal position and the component held by its body, thrust is
applied to the termination as close as possible to the body of the component, but leaving a
clear 2 mm of wire between the body of the component and the nearest point of the device
applying the force. The force shall be applied progressively (without any shock) and then
maintained for a period of 10 s ± 1 s.
4.3 Preconditioning
The method of preconditioning shall be as prescribed in the relevant specification.
4.4 Initial measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
4.5 Test method
Refer to Figure 2b.
4.5.1 Application
The relevant specification shall state whether this test is applicable. When applicable, it shall
be carried out on all the terminations, except where a component has more than three
terminations, in which case the specification shall state the number of terminations per
component to be tested. The test shall be carried out in such a manner that all the
terminations of the component have an equal probability of being subjected to test. The
relevant specification shall define the direction of applied force.
4.5.2 Procedure
With the termination in its normal position and the component held by its body, thrust shall be
applied to the termination as close as possible to the body of the component, but leaving a
clear 2 mm of wire between the body of the component and the nearest point of the device
applying the force. The force shall be applied progressively (without any shock) and then
maintained for a period of 10 s ± 1 s.
The value of the applied force is as follows:
a) Wire terminations (circular-section or strip) or pins
The value of the force applied shall be as given in Table 3.

– 10 – 60068-2-21  IEC:2006
Table 3 – Value of applied force for test Ua
a
Nominal cross-sectional area (S) Corresponding diameter (d) for
Force with tolerance of ±10 %
circular-section wire
mm mm N
s ≤ 0,05      d ≤ 0,25 0,25
0,05 < s ≤ 0,10 0,25 < d ≤ 0,35 0,5
0,10 < s ≤ 0,20 0,35 < d ≤ 0,50 1
0,20 < s ≤ 0,50 0,50 < d ≤ 0,80 2
0,50 < s ≤ 1,20 0,80 < d ≤ 1,25 4
s > 1,20      d > 1,25 8
a
For circular-section wires, strips or pins, the nominal cross-sectional area is equal to the value calculated from
the nominal dimension(s) given in the relevant specification.

Insulated wires shall be stripped of the insulation at the point at which the load is applied.
Where the technical features of insulated wires may give rise to difficulties during the
stripping, and be liable to cause dispute for the test results, such operations shall be in
accordance with the relevant specification or, where necessary, with the instructions of the
component manufacturer.
b) Other terminations (tag terminations, threaded studs, screws, terminals, etc.)
The value of the force to be applied shall be given in the relevant specification.
4.6 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
4.7 Information to be given in the relevant specification
Subclause
a) Method of preconditioning 4.3
b) Initial measurements 4.4
c) Indication as to whether the test is applicable 4.5.1
d) Number of terminations to be tested, if more than three 4.5.1
e) Direction of applied force 4.5.1
f) Details of stripping, if necessary 4.5.2
g) Force, for other than wire terminations or pins 4.5.2
h) Final measurements 4.6
5 Test Ub: bending
This test is applicable to pliable terminations only.
5.1 Object
The purpose of this test is to verify that pliable terminations and attachment of such
terminations to the body of the component shall withstand such bending loads as are likely to
be applied during normal assembly or handling operations. In order for the terminations to be
considered pliable, the following conditions shall apply:

60068-2-21  IEC:2006 – 11 –
a) Test prescribed in 5.5.2.1 and 5.5.2.3
The termination shall assume, during the course of the test, a displacement of at least 30°
with respect to its initial position (see Figure 3c).
b) Test prescribed in 5.5.2.2:
The termination shall be capable of being bent with the fingers.
5.2 General description
a) Bending (wire or strip terminations)
With the termination in its normal position and the component held by its body in such a
manner that the axis of the termination is vertical, a mass is suspended from the end of
termination. The body of the component is then inclined through an angle of approximately
90° in the vertical plane and then returned to its original position; this operation
constitutes one bend.
Method 1: two or more bends in opposite directions.
Method 2: two or more bends in the same direction.
b) Bending (tag terminations)
Tag terminations, capable of being bent with the fingers, shall be bent through 45° and
then returned to their initial position; this operation constitutes one bend.
Method 1: two bends in opposite directions.
Method 2: two bends in the same direction.
c) Simultaneous bending
All the terminations on one side of the component shall be held in a clamp at a point 3 mm
from the seal between the termination and the body of the component. A mass shall be
attached to the clamp with the terminations pointing downwards. The body of the
component is then inclined through an angle of 45° and returned to its original position.
This test shall be performed in two opposite directions.
5.3 Preconditioning
The method of preconditioning shall be as prescribed in the relevant specification.
5.4 Initial measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
5.5 Test method
Unless otherwise specified in the relevant specification, the test method shall be as follows:
5.5.1 Application
The relevant specification shall state whether this test is applicable. When applicable, the test
shall be carried out on all the terminations, except where a component has more than three
terminations, in which case the specification shall state the number of terminations per
component to be tested. The test shall be carried out in such a manner that all the
terminations of the component have an equal probability of being subjected to test. This
limitation in the number of terminations tested does not apply to simultaneous bending
(5.5.2.3), which is generally applicable to certain types of microelectronic packages with
several terminations in line on one or more sides.

– 12 – 60068-2-21  IEC:2006
5.5.2 Procedure
Refer to Figure 3.
5.5.2.1 Bending (wire or strip terminations)
With the termination in its normal position and the component held by its body in such a
manner that the axis of the termination is vertical, a mass applying a force of a value given in
Table 4 is then suspended from the end of the termination. The body of the component is then
inclined, over a period of 2 s to 3 s, through an angle of approximately 90° in the vertical
plane and then returned to its original position over the same period of time; this operation
constitutes one bend. The test shall be performed according to the relevant specification,
stipulating one or other of the following procedures.
a) Method 1 (see Figure 3a)
One bend immediately followed by a second bend in the opposite direction, or a larger
number of alternate bends where prescribed in the relevant specification.
b) Method 2 (see Figure 3b)
Two bends in the same direction without interruption, or a larger number of alternate
bends where prescribed in the relevant specification. No device capable of imposing a
radius of curvature shall be placed between the body of the component and the point of
application of the force. Strip terminations shall be bent perpendicularly to the widest
surface of the strip.
The value of the force to be applied is given in Table 4.
Table 4 – Value of applied force for test Ub
Section modulus (Z ) Diameter(d) of corresponding Force with tolerance
x
round leads
of 10 %
mm mm N
–3 0,5
Z  1,5  10     d  0,25
x
–3 –3 1,25
1,5  10  Z  4,2  10 0,25  d  0,35
x
–3 –2
2,5
4,2  10  Z  1,2  10 0,35  d  0,50
x
–2 –1 5
1,2  10  Z  0,5  10 0,50  d  0,80
x
–1 –1 10
0,5  10  Z 1,9  10 0,80  d  1,25
x
–1
1,9  10  Z         1,25  d
x
NOTE 1 For round terminations, the section modulus is given by the following formula:
d
Z =
x
where d is the lead diameter.
For strip terminations, the section modulus is given by the following formula:
ba
Z =
x
where
a is the thickness of the rectangular strip perpendicular to the bending axis;
b is the other dimension of the rectangular strip;
Z is the section modulus.
x
NOTE 2 The section modulus is defined in ISO 31-3, item 3-21, and the derivation of the above formula can be
found in standard textbooks on mechanical engineering.

60068-2-21  IEC:2006 – 13 –
5.5.2.2 Bending (tag terminations)
Tag terminations, capable of being bent with the fingers, shall be bent through 45° and then
returned to their initial position; this operation shall constitute one bend (see Figure 3). The
test shall be performed according to the relevant specification, stipulating one or other of the
following procedures:
a) Method 1
One bend immediately followed by a second bend in the opposite direction.
b) Method 2
Two bends in the same direction, without interruption. The relevant specification may
stipulate other details (such as use of pliers, place of bending, etc.).
5.5.2.3 Simultaneous bending
All terminations on one side of the component shall be clamped at the seating plane or, where
it is not given, at a point approximately 3 mm from the seal between the termination and the
body of the component, in a clamp with a radius of 0,1 mm at the edge where bending will
occur. A mass shall be attached to the clamp with the terminations pointing downwards. This
mass, which shall include the mass of the clamp, shall apply a force equal to that given in
Table 4, multiplied by the number of leads clamped.
The body of the component is then inclined through an angle of 45°, taking 2 s to 3 s for the
operation, and returned to its initial position over the same period of time. The test shall be
performed once in one direction, and returned to the normal position, and once in the opposite
direction, and again returned to the normal position (see Figure 3).
NOTE For the testing of short terminations, the clamp should be so designed that its upper surface will not touch
the body of the component during the bending (which would cause a tensile stress on the terminations). See
Figure 1 below:
IEC  894/01
Figure 1 – Clamp for the testing of short terminations
5.6 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.

– 14 – 60068-2-21  IEC:2006
5.7 Information to be given in the relevant specification
Subclause
a) Method of preconditioning 5.3
b) Initial measurements 5.4
c) Indication as to whether the test is applicable 5.5.1
d) Number of terminations to be tested, if more than three 5.5.1
e) Method and number of bends, if more than two 5.5.2.1
f) Method and particular details of application 5.5.2.2
g) Final measurements 5.6
6 Test Uc: torsion
6.1 Object
The purpose of this test is to verify that the terminations and attachment of the terminations to
the body of the component will withstand torsional forces such as are likely to be applied
during normal assembly or dismantling operations.
6.2 Preconditioning
The method of preconditioning shall be as prescribed in the relevant specification.
6.3 Initial measurements
The specimen shall be visually inspected and electrically and mechanically checked as
required by the relevant specification.
6.4 Test method
Unless otherwise specified in the relevant specification, the test method shall be as follows:
Refer to Figure 4.
6.4.1 Application
The relevant specification shall state whether this test is applicable. When applicable, the test
shall be carried out on all the terminations, except where a component has more than three
terminations, in which case the specification shall state the number of terminations per
component to be tested. The test shall be carried out in such a manner that all the
terminations of the component have an equal probability of being subjected to test.
6.4.2 Procedure
Each termination shall be bent through 90° at a point 6 mm to 6,5 mm from the point of
emergence of the termination. The radius of curvature of the bend shall be approximately
0,75 mm (see Figure 4a). The free end of the termination shall be clamped to a point 1,2 mm
± 0,4 mm from the bend (see Figure 4b). The body of the component shall then be rotated, as
specified below, about the original axis of the termination at a rate of one rotation per 5 s.
Successive rotations shall be in alternate directions. The test shall be performed in
accordance with one of the following procedures, and one of the following severities as
required by the detail specification.

60068-2-21  IEC:2006 – 15 –
a) Method 1
Component body clamped:
– Severity 1: three rotations of 360°;
– Severity 2: two rotations of 180°.
b) Method 2
Both wire terminations clamped (see Figure 4c):
– Severity: two rotations of 180°.
NOTE Method 2 is primarily intended for components with a body unsuitable for clamping (e.g. having a diameter
less than 4 mm) and with axial terminations of the same kind at each end.
6.5 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
6.6 Information to be given in the relevant specification
Subclause
a) Method of preconditioning 6.2
b) Initial measurements 6.3
c) Indication as to whether this test is applicable 6.4.1
d) Number of terminations to be tested, if more than three 6.4.1
e) Test procedures and severities 6.4.2
f) Final measurements 6.5
7 Test Ud: torque
7.1 Object
The purpose of this test is to verify that the terminations, the attachment of the terminations to
the body of the component and integral mounting means shall withstand torque forces such as
are likely to be applied during normal assembly or handling operations.
7.2 General description
For terminations with threaded studs or screws, the torque given in Table 5 below is applied
to the screw or to each of the nuts normally fitted to each terminal for a period of 10 s to 15 s,
according to the severity prescribed in the relevant specification. During this test, a washer or
metal plate with a normal clearance hole for the screw threads shall be placed between the
screw head and the surface on to which it is tightened. For other types of termination the
relevant specification shall give the method required.
7.3 Preconditioning
The method of preconditioning shall be as prescribed in the relevant specification.
7.4 Initial measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.

– 16 – 60068-2-21  IEC:2006
7.5 Test method
Unless otherwise specified in the relevant specification, the test method shall be as follows:
7.5.1 Application
The relevant specification shall state whether this test is applicable. When applicable, the test
shall be carried out on all the terminations, except where a component has more than three
terminations, in which case the specification shall state the number of terminations per
component to be tested. The test shall be carried out in such a manner that all the
terminations of the component have an equal probability of being subjected to test.
7.5.2 Procedure
7.5.2.1 Terminations with threaded studs or screws
With the component held by its normal fixing devices, the torque given in Table 5 shall be
applied without shock to the screw or to each of the nuts normally fitted to each termination,
for a period of 10 s to 15 s, according to the severity prescribed by the relevant specification.
During this test, a washer or metal plate with a normal clearance hole for the screw threads
shall be placed between the screw head and the surface on to which it is tightened. The
thickness of the washer or metal plate shall be approximately equal to six times the nominal
pitch of the stud. All parts shall be clean and dry. The nut width shall be equal to
approximately 0,8 times the nominal stud diameter, as stated in ISO 272.
Table 5 – Torque severity
Nominal thread diameter
2,6 3,0 3,5 4,0 5,0 6,0 8,0
mm
Torque Severity 1 0,4 0,5 0,8 1,2 2,0 2,5 5,0
Nm Severity 2 0,2 0,25 0,4 0,6 1,0 1,25 2,5

For some components, such as semiconductor devices, very different torque values may be
needed. Where necessary, these shall be prescribed in the relevant specification. For
diameters greater than 8 mm, the torque values shall be specified in the relevant specification.
The nuts or screws shall be capable of being loosened afterwards.
7.5.2.2 Other types of terminations
The relevant specification shall give the methods required.
7.6 Final measurements
The specimen shall be visually inspected and electrically and mechanically checked, as
required by the relevant specification.
7.7 Information to be given in the relevant specification
Subclause
a) Method of preconditioning 7.3
b) Initial measurements 7.4
c) Indication as to whether thi
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