IEC 61760-3:2021

IEC 61760-3 ®
Edition 2.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Surface mounting technology –
Part 3: Standard method for the specification of components for through-hole
reflow (THR) soldering
Technique du montage en surface –
Partie 3: Méthode normalisée relative à la spécification des composants pour
le brasage par refusion à trous traversants (THR, Through Hole Reflow)

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - IEC online collection - oc.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un
en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour
comité d’études, …). Elle donne aussi des informations sur adapté à vos besoins.
les projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au
Restez informé sur les nouvelles publications IEC. Just
monde, avec plus de 22 000 articles terminologiques en
Published détaille les nouvelles publications parues.
anglais et en français, ainsi que les termes équivalents dans
Disponible en ligne et une fois par mois par email.
16 langues additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC 61760-3 ®
Edition 2.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Surface mounting technology –
Part 3: Standard method for the specification of components for through-hole

reflow (THR) soldering
Technique du montage en surface –

Partie 3: Méthode normalisée relative à la spécification des composants pour

le brasage par refusion à trous traversants (THR, Through Hole Reflow)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.190 ISBN 978-2-8322-9294-5

– 2 – IEC 61760-3:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Requirements to component design and component specifications . 9
4.1 General requirement . 9
4.2 Packaging . 9
4.3 Labelling of component packaging . 10
4.4 Component marking . 10
4.5 Storage and transportation . 10
4.6 Component outline and design . 10
4.6.1 Drawing and specification . 10
4.6.2 Requirement of pick-up area . 11
4.6.3 Component tilt . 13
4.6.4 Bottom surface requirements . 13
4.6.5 Terminal requirements . 14
4.6.6 Optical recognition . 19
4.6.7 Component height . 19
4.6.8 Component mass . 20
4.7 Mechanical stress . 20
4.8 Component reliability . 20
4.9 Additional requirements for compatibility with lead-free soldering . 20
5 Typical process conditions for THR soldering process . 20
5.1 Mounting by through-hole reflow soldering . 20
5.2 Solder paste supply . 21
5.3 Component insertion . 22
5.4 Reflow soldering methods (recommended) . 22
5.5 Cleaning . 23
5.5.1 General . 23
5.5.2 Cleaning medium and cleaning method . 23
5.5.3 Cleaning process conditions . 23
5.6 Removal and/or replacement of soldered components . 24
6 Relevant tests and requirements for components and component specifications for
THR soldering process . 24
6.1 General . 24
6.2 Wettability . 25
6.3 Dewetting . 25
6.4 Resistance to soldering heat . 25
6.5 Resistance to cleaning solvent . 25
6.5.1 General . 25
6.5.2 Solvent resistance of component . 26
6.5.3 Solvent resistance of marking . 26
6.6 Soldering profile . 26
6.7 Moisture sensitivity level . 26
7 Quality criteria for THR soldering . 26
Annex A (informative) Flux creeping-up and solder wicking . 27

Bibliography . 28

Figure 1 – Example of a component with marked specific orientation put in tape
and tray . 9
Figure 2 – Example of components in a tape . 10
Figure 3 – Pick-up area . 12
Figure 4 – Chuck jaw . 12
Figure 5 – Component side flat surface . 13
Figure 6 – Component top flat surface . 13
Figure 7 – Clearance . 14
Figure 8 – Stand-off height . 14
Figure 9 – Terminal length and protrusion length . 15
Figure 10 – Terminal position tolerance 0,2 mm . 16
Figure 11 – Terminal position tolerance 0,4 mm . 17
Figure 12 – Terminal shape . 18
Figure 13 – Solder wetting . 19
Figure 14 – Typical soldering process steps. 21
Figure 15 – Solder paste supply . 22
Figure A.1 – Example of the flux creeping-up . 27
Figure A.2 – Example of the solder wicking . 27

Table 1 – Typical cleaning conditions. 24

– 4 – IEC 61760-3:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SURFACE MOUNTING TECHNOLOGY –
Part 3: Standard method for the specification of
components for through-hole reflow (THR) soldering

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
misinterpretation by any end user.
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.
IEC 61760-3 has been prepared by IEC technical committee 91: Electronics assembly
technology. It is an International Standard.
This second edition cancels and replaces the first edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) change position tolerance requirement (0,4 mm maximum to between 0,2 mm and 0,4 mm);
b) introduce through-hole vacant method as a solder paste supply method.

The text of this International Standard is based on the following documents:
Draft Report on voting
91/1684/FDIS 91/1702/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 61760 series, published under the general title Surface mounting
technology, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 61760-3:2021 © IEC 2021
SURFACE MOUNTING TECHNOLOGY –
Part 3: Standard method for the specification of
components for through-hole reflow (THR) soldering

1 Scope
This part of IEC 61760 gives a reference set of requirements, process conditions and related
test conditions to be used when compiling specifications of electronic components that are
intended for usage in through-hole reflow soldering technology.
The object of this document is to ensure that components with leads intended for through-hole
reflow and surface mounting components can be subjected to the same placement and
mounting processes. Hereto, this document defines test and requirements that need to be part
of any component generic, sectional or detail specification, when through-hole reflow soldering
is intended.
Furthermore, this document provides component users and manufacturers with a reference set
of typical process conditions used in through-hole reflow soldering technology.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 (all parts), Environmental testing
IEC 60068-2-20:2008, Environmental testing – Part 2-20: Tests – Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of terminations
and integral mounting devices
IEC 60068-2-45:1980, Basic environmental testing procedures – Part 2-45: Tests – Test XA
and guidance: Immersion in cleaning solvents
IEC 60068-2-45:1980/AMD1:1993
IEC 60068-2-58, 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)
, Environmental testing – Part 2-77: Tests – Test 77: Body strength and impact
IEC 60068-2-77
shock
IEC 60194-1, Printed boards design, manufacture and assembly – Vocabulary – Part 1:
Common usage in printed board and electronic assembly technologies
___________
To be integrated into the seventh edition of IEC 60068-2-21.
Stage at the time of publication: IEC/AFDIS 60068-2-21:2021.

IEC 60286 (all parts), Packaging of components for automatic handling
IEC 60286-3, Packaging of components for automatic handling – Part 3: Packaging of surface
mount components on continuous tapes
IEC 60286-4, Packaging of components for automatic handling – Part 4: Stick magazines for
electronic components encapsulated in packages of different forms
IEC 60286-5, Packaging of components for automatic handling – Part 5: Matrix trays
IEC 60749-20, Semiconductor devices – Mechanical and climatic test methods – Part 20:
Resistance of plastic encapsulated SMDs to the combined effect of moisture and soldering heat
IEC 61188-6-4, Printed boards and printed board assemblies – Design and use – Part 6-4: Land
pattern design – Generic requirements for dimensional drawings of surface mounted
components (SMD) from the viewpoint of land pattern design
IEC 61191-3, Printed board assemblies – Part 3: Sectional specification – Requirements for
through-hole mount soldered assemblies
IEC 61760-1:2020, Surface mounting technology – Part 1: Standard method for the
specification of surface mounting components (SMDs)
IEC 61760-2, Surface mounting technology – Part 2: Transportation and storage conditions of
surface mounting devices (SMD) – Application guide
IEC 61760-4:2015, Surface mounting technology – Part 4: Classification, packaging, labelling
and handling of moisture sensitive devices
IPC/JEDEC J-STD-020, Moisture/Reflow Sensitivity Classification for Non-hermetic Solid State
Surface Mount Devices
IPC-A-610G, Acceptability of Electronic Assemblies
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60194-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
through-hole reflow
THR
reflow soldering process for electronic component terminals inserted into the through-hole of
the circuit board
3.2
THR components
through-hole reflow components
electronic components with leads which are intended to be subject to through-hole reflow
soldering
– 8 – IEC 61760-3:2021 © IEC 2021
3.3
vacuum nozzle
pipette
type of tooling for component to pick-up and place the component with vacuum
3.4
chuck
gripper
type of tooling for component transfer
3.5
chucking
gripping
motion of the chuck (3.4) to hold the components
3.6
pick-up area
component surface area for vacuum suction or chucking to transfer within pick and place
machine
3.7
cavity of packaging
depression area to place component in taping or tray
3.8
stand-off
protrusion(s) from the component body which are used to make a space between the component
body and the seating plane
Note 1 to entry: Stand-off prevents the component touching the solder paste.
3.9
clearance
space to avoid contact between component body and solder paste and to ensure sufficient heat
transfer to soldering regions
3.10
auxiliary terminal
protrusion which has no electrical function inserted into a circuit board
3.11
stencil
stencil foil
thin sheet of material containing openings to reflect a specific pattern, designed to transfer
solder paste like material to a circuit board for the purpose of component attachment
[SOURCE: IEC 60194-1:2021, 3.19.187, modified – The words " paste-like material " have been
replaced by "solder paste like material" and “substrate” has been replaced by “circuit board”.]
3.12
A side
circuit board surface to which THR components (3.2) are to be mounted
3.13
B side
reverse surface of A side (3.12)

3.14
solder wicking
capillary movement of solder between metal surfaces, such as strands of wire
[SOURCE: IEC 60194-1:2021, 3.19.125]
4 Requirements to component design and component specifications
4.1 General requirement
The component specification for THR components (hereinafter, referred to as component
specification) shall specify the requirements specified in 4.2 through 4.9 and Clause 6.
4.2 Packaging
Packaging for THR components shall be in accordance with IEC 60286-3, IEC 60286-4 and
IEC 60286-5.
The component specification shall specify the following:
– Protection of THR components during transportation and storage;
– Moisture absorption control; if needed, follow the moisture sensitivity level (MSL) according
to IEC 61760-4, IEC 60749-20 or IPC/JEDEC J-STD-020 (see 6.7);
– Polarity or pin 1 indication (see Figure 1);
– Orientation of the component in the packaging (see Figure 2).

Figure 1 – Example of a component with marked
specific orientation put in tape and tray

– 10 – IEC 61760-3:2021 © IEC 2021

Figure 2 – Example of components in a tape
4.3 Labelling of component packaging
Labelling of the component packaging should comply with IEC 62090.
NOTE The following items are particularly important.
– item identification (e.g. customer part number or manufacturer part number or both);
– quantity;
– traceability identification (e.g. batch number or serial number).
4.4 Component marking
The marking on the component shall be specified in the component specification.
4.5 Storage and transportation
Component specification shall refer to storage and transportation conditions of IEC 61760-2.
4.6 Component outline and design
4.6.1 Drawing and specification
Drawings, including bottom-view, top-view and side-view drawings, of the component showing
all dimensions and tolerances of its body and terminals shall be part of the component
specification. The drawing shall include reference to the positioning of the component body and
terminals on the mounting land pattern. If conductive surfaces are not planar, their three-
dimensional geometry shall be clearly specified with the relevant tolerances.
In any 2D drawing or 3D data, conductive parts/surfaces and insulating parts/surfaces shall be
clearly distinguished, at least for bottom and sides of components, as well as for movable parts.
This requirement applies both to the disassembled and the assembled condition for parts
requiring a final assembly step after mounting on a substrate (e.g. if a connector contains
spring-loaded retainers, which change their position/angle upon mating). The locations and
dimensions of conductive parts/surfaces shall be specified even if they are not intended for
establishing a contact with the mounting surface, e.g. punched or sawn surfaces consisting of
unplated leadframe resulting from component singulation for molded semiconductor packages.

Component drawing and component specification shall specify in particular the following
information:
– Dimensions and tolerances according to 4.6.4, 4.6.5.1 and 4.6.5.2;
– Dimensional drawings of footprint design. The generic requirements for dimensional
drawings of SMDs from viewpoint of land-pattern design as specified in IEC 61188-6-4 shall
be adopted for surface-mount devices;
– Locations of metal parts which contact to the circuit board surface.
The manufacturer of a THR component shall consider that the design and material selection
can lead to a possible expansion or deformation of the component in the reflow process. The
manufacturer shall provide an appropriate recommendation for mounting including a footprint
recommendation.
4.6.2 Requirement of pick-up area
4.6.2.1 General requirement
Design of the component shall be in such a way, that it is possible to hold the component by
vacuum nozzle or mechanical chuck and transfer it to the exact placement position on the circuit
board. It shall be possible to create a vacuum or mechanical force strong enough to hold the
component in its position under the vacuum nozzle or chuck. During the total transfer process,
which may include optical inspection, the component shall remain exactly in its position under
the vacuum nozzle or chuck, until the component is placed.
The centre of the suction area shall match the centre of gravity (major requirement) and the
geometrical centre (minor requirement).
NOTE Assembly manufacturer considers mounting by vacuum nozzle first. If a vacuum nozzle is not available,
then chuck will be selected.
4.6.2.2 Vacuum nozzle mounting
Vacuum nozzle mounting shall be in accordance with IEC 61760-1.
In the case of mounting or inserting the component by using vacuum nozzle, the following
matters shall be considered and, when necessary, clarified between the manufacturer and the
user of the component:
– The pick-up area shall be on top of the component;
– The pick-up area shall be appropriately secured depending on the mass of the component;
NOTE See 4.6.8 for the relation between area of vacuum nozzles and mass of components.
– If a suitable pick-up area is not ensured, then sticky tape or caps (see Figure 3) shall be
used;
– Sticky tape or caps shall not fall off during and after reflow soldering;
– The centre of the pick-up area should match the component centre of gravity. Unless the
component dose not tilt, the geometrical centre may be used.

– 12 – IEC 61760-3:2021 © IEC 2021

Key
1 vacuum nozzle
2 pick-up area
3 component body
4 sticky tape
Figure 3 – Pick-up area
4.6.2.3 Chuck mounting
In the case of mounting or inserting the component using a chuck, an agreement between
manufacturer and user is necessary considering the following matters:
– There shall be enough gap between the component and the cavity of packaging (see
Figure 4);
– Components shall have flat surface on sides for chucking (see Figure 5);
– Components shall have flat surface on top which make the component fixed while chucking
(see Figure 6);
– It is desirable to reduce rattling between the component and the cavity.

Chuck jaws are shown in hatched.
Figure 4 – Chuck jaw
Component side flat surface are shown hatched.
Figure 5 – Component side flat surface

Component top flat surface is shown hatched.
Figure 6 – Component top flat surface
4.6.3 Component tilt
The components shall be self-sustaining when the component is inserted into a circuit board
and the component body comes into contact with the circuit board. The components should not
be designed to incline taking into account the centre of the gravity of the components. If a
component tilt is not avoidable due to the component structure, a retention mechanism to
prevent the tilting should be considered.
4.6.4 Bottom surface requirements
Sufficient clearances shall be considered to avoid contact between component body and solder
paste and to ensure sufficient heat transfer to soldering regions (see Figure 7).
To ensure sufficient clearances, the components shall have a stand-off height of 0,5 mm or
more and should not contact with the circuit board except for terminals and stand-off
(see Figure 8).
– 14 – IEC 61760-3:2021 © IEC 2021
In addition, the components shall be designed to avoid creeping up of flux and solder wicking
(see Annex A).
When designing the clearance of a component, the amount of solder paste to be supplied needs
to be adapted.
Key
1 clearance
Bottom side of the connector
Figure 7 – Clearance
Key
1 component body
2 solder
3 terminal
4 circuit board
5 stand-off height
6 stand-off
Figure 8 – Stand-off height
4.6.5 Terminal requirements
4.6.5.1 Terminal length
The terminal length of the component shall be the length at which the terminal protrudes from
the B side of the circuit board in order to improve the visibility in visual inspection, the ease of
judgment in the image inspection equipment after reflow soldering, and to ensure the solder
joint strength (see Figure 9). The recommended protrusion length is 0,5 mm minimum and the
terminal length should be depending upon the circuit board thickness.
Other dimensions shall be discussed between the user and the supplier of the component.

Key
1 seating plane
2 terminal length from seating plane to the tip of terminal.
3 protrusion length
Figure 9 – Terminal length and protrusion length
4.6.5.2 Terminal position tolerance
The position tolerance of each pin tip should be specified to a value between 0,2 mm and
0,4 mm in diameter (see Figure 10 and Figure 11).
For any protrusion which is to be inserted into the circuit board such as an auxiliary terminal,
the same position tolerance should apply.
If the location of the terminals does not fall within the recommended tolerance, or when a
specific requirement shall apply, the manufacturer and the user of the components should be
consulted.
NOTE A smaller position tolerance of the component terminals is expected, because of the tolerance that is
determined by the hole diameter and hole position tolerance of the circuit board, the positioning accuracy of the
placement equipment that will insert the device, the required supply amount of the solder paste and the maximum
traveling distance to the land at the time of the solder paste reflow.

– 16 – IEC 61760-3:2021 © IEC 2021
Dimensions in millimetres
Version A
Square pin
Version B
Rectangular pin
Version C
Round pin
Key
A hole in gauge
B diameter of pin
Figure 10 – Terminal position tolerance 0,2 mm

Dimensions in millimetres
Version A
Square pin
Version B
Rectangular pin
Version C
Round pin
Key
A hole in gauge
B diameter of pin
Figure 11 – Terminal position tolerance 0,4 mm

– 18 – IEC 61760-3:2021 © IEC 2021
4.6.5.3 Terminal shape
The terminal shape of the component shall be a straight shape (see Figure 12 a)). The tip of
terminals should be chamfered or rounded. Kinked terminal as shown in Figure 12 b), and snap-
in terminal as shown in Figure 12 c) are not acceptable.
For the terminals not intended to be inserted into the circuit board, terminal shape is arbitrary.
NOTE 1 The kinked terminal or the snap-in terminal can be inserted manually but the vibration of the board is
anticipated. The board vibration can cause a quality risk for the pre-mounted surface mount components, or the
additional manual rework operation at the mounting process.
NOTE 2 It can sometimes happen that the tip configuration of chamfered or rounded is not available. In such
circumstance, the special footprint design is needed.
NOTE 3 Chamfer reduces the pin tip diameter to less than half of that of the pin shaft.

a) Straight terminal b) Kinked terminal c) Snap-in terminal

Key
1 component body
2 terminal
3 chamfered tip
4 rounded tip
Figure 12 – Terminal shape
4.6.5.4 Hardness of terminal
The terminal shall not change shape during transportation, storage and placement or insertion.
4.6.5.5 Solder wettable surface
The solder wettable surface of the terminals should allow that a visible solder fillet on the
component side can be formed. Taking the stand-off of the component into consideration, at
least 0,2 mm of the terminal above the circuit board level on the component side should be
solder wettable (see Figure 13).

Key
1 component body
2 circuit board
3 solder
4 terminal
5 solder wetting height
6 solder fillet (meniscus) height
Figure 13 – Solder wetting
4.6.5.6 Material content
Details on composition, thickness, and layer-structure of the surfaces to be soldered should be
given.
This information is needed (among others) to determine the suitable whisker test methods from
IEC 60068-2-82.
4.6.6 Optical recognition
The optical contrast between the terminal bottom surface and the component bottom surface
around the terminals shall be high enough (until assembling) to enable optical recognition of
the position of the terminals, seen from the bottom side. Preferably at the bottom side the
terminal pin at the final stages shall be reflecting.
The following items are the information to be noted regarding to the optical recognition:
– the mounting equipment applies light to the component terminals to recognize the
component terminal tip position;
– if the optical recognition function of the mounting machine is not able to detect the terminal
tips, then the component outline is used;
– in the case where component recognition is used, there may be problems, such as, the
terminals may not be inserted into the circuit board or the terminal bend may not be detected.
Therefore, terminal tip recognition is preferred.
4.6.7 Component height
The component height is limited by the length of the vacuum nozzle or chuck and the space
traversed between pick-up and placement. A proper clearance is required by the length of the
vacuum nozzle or chuck and the component height for the traverse from pick-up to placement.
The component height and the cavity of component packaging shall be matched to each other
to enable the vacuum nozzle or chuck to safely pick-up the component. If standardized
packaging complying with the IEC 60286 series of standards is used, the component height
shall relate to the packing dimensions specified therein.

– 20 – IEC 61760-3:2021 © IEC 2021
The component height is also important to avoid overheating of the component top surface
during forced gas convection reflow soldering.
4.6.8 Component mass
Regarding the component mass, the following should be considered:
– For a stable pick-up and transfer of the component to the mounting location, the following
should be considered: There is a relationship between maximum payload mass and vacuum
nozzle diameter. The diameter of the pick-up area should be selected appropriately
considering the component mass and pick-up area surface properties.
– A low thermal mass is beneficial in establishing suitable reflow-soldering profiles.
4.7 Mechanical stress
Components shall withstand the stresses applied by placement equipment such as pick-
up/impact force, centering force and placement force. The component specification shall specify
the details of the test method selected from IEC 60068-2-21 and IEC 60068-2-77.
4.8 Component reliability
Requirements and related test methods that define the long-term performance of a component
shall be specified in the component specification. These tests shall be conducted on the
components which are mounted on the circuit board.
The test methods specified in the component specification shall be preferably selected from
IEC 60068 (all parts) unless otherwise specified in the test specification for the relevant
components.
The component specification shall specify the operating temperature range. Derating may be
applied. The operating temperature range shall be in accordance with the long-term
performance of the component.
The allowable number of reflow soldering processes shall be specified in the component
specification. If the component specification does not specify the allowable number of reflow
soldering processes, 2 times shall be applied.
NOTE In the worst case, the components are subjected to three consecutives reflow soldering processes.
4.9 Additional requirements for compatibility with lead-free soldering
In component specifications, the compatibility of the terminations with the solder used shall be
defined. This is as important to lead-free terminations in connection with lead-free solders as
in connection with lead containing solders.
5 Typical process conditions for THR soldering process
5.1 Mounting by through-hole reflow soldering
The soldering process steps are depending on mounting method and conditions in use.
A flow chart for a typical soldering process of a single sided circuit board is shown in Figure 14.

Figure 14 – Typical soldering process steps
5.2 Solder paste supply
The amount of the solder paste to be supplied to the circuit board shall be sufficient enough to
fill the through-hole with the solder and to form a solder fillet on the B side after the reflow
soldering process.
The solder paste thickness on the circuit board (t) should be between 100 μm and 250 μm.
Through-hole filled method: The solder paste should be supplied to the circuit board using
stencil printing or a dispenser to fill the through-hole by solder paste. Solder paste protrusion
from B side (L) should be 1 mm or less so that the solder paste does not fall down before reflow
soldering. See Figure 15 a).
NOTE 1 When the component terminals are inserted into the through-holes filled with solder paste, the solder paste
is pushed out and fall into the reflow furnace. There is a possibility of soldering defects, such as blowholes, voids
and similar state, due to the flux evaporation (sudden boiling) inside of the through-hole and/or reduced liquidity of
the molten solder during reflow soldering.
Through-hole vacant method: The solder paste should be supplied on the circuit board using
stencil printing or a dispenser such that it does not fill the through-hole with solder paste. The
supplied solder paste will melt and flow into the through-hole during reflow soldering. See
Figure 15 b).
NOTE 2 This method needs a relatively large solder paste area.

– 22 – IEC 61760-3:2021 © IEC 2021

a) Through-hole filled method b) Through-hole vacant method

Key
1 A side
2 solder paste
3 land
4 circuit board
5 through-hole
6 B side
t solder paste thickness
L solder paste protrusion height
Figure 15 – Solder paste supply
5.3 Component insertion
THR components shall be inserted using pick and place machines. The insertion conditions
shall be selected appropriately. Optical recognition of component and printed circuit board
position is necessary.
5.4 Reflow soldering methods (recommended)
The re
...