IEC 61191-2:2013

Printed board assemblies - Part 2: Sectional specification - Requirements for surface mount soldered assemblies

IEC 61191-2:2013 gives the requirements for surface mount solder connections. The requirements pertain to those assemblies that are totally surface mounted or to the surface mounted portions of those assemblies that include other related technologies (e.g. through-hole, chip mounting, terminal mounting, etc.). This edition includes the following significant technical changes with respect to the previous edition:
- IPC-A-610 on workmanship has been included as a normative reference;
- some of the terminology used in the document has been updated;
- references to IEC standards have been corrected;
- the use of lead-free solder paste and plating are addressed.

Ensembles de cartes imprimées - Partie 2: Spécification intermédiaire - Exigences relatives à l'assemblage par brasage pour montage en surface

La CEI 61191-2:2013 donne les exigences relatives aux connexions brasées pour montage en surface. Les exigences se rapportent aux ensembles intégrant uniquement le montage en surface ou aux portions d'ensembles pour montage en surface incluant d'autres technologies associées (par exemple montage par trous traversants, montage à puce, à borne, etc.). Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- inclusion du document IPC-A-610 sur la qualité d'exécution en tant que référence normative;
- mise à jour d'une partie de la terminologie utilisée dans le présent document;
- correction des références aux normes CEI;
- prise en compte de l'utilisation de crème de brasage et de métallisation sans plomb.

General Information

• Status: Published
• Publication Date: 04-Jun-2013
• ICS: 31.190 - Electronic component assemblies
• ICS: 31.240 - Mechanical structures for electronic equipment
• Technical Committee: TC 91 - Electronics assembly technology
• Drafting Committee: WG 2 - TC 91/WG 2
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 23-May-2017

Relations

• Revised: IEC 61191-2:2017 - Printed board assemblies - Part 2: Sectional specification - Requirements for surface mount soldered assemblies
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61191-2
®

Edition 2.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Printed board assemblies –
Part 2: Sectional specification – Requirements for surface mount soldered
assemblies

Ensembles de cartes imprimées –
Partie 2: Spécification intermédiaire – Exigences relatives à l’assemblage par
brasage pour montage en surface

IEC 61191-2:2013

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IEC 61191-2

®


Edition 2.0 2013-06




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE











Printed board assemblies –

Part 2: Sectional specification – Requirements for surface mount soldered

assemblies




Ensembles de cartes imprimées –

Partie 2: Spécification intermédiaire – Exigences relatives à l’assemblage par


brasage pour montage en surface













INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX U


ICS 31.190; 31.240 ISBN 978-2-83220-856-4



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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– 2 – 61191-2 © IEC:2013
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Conventions . 6
4 General requirements . 6
5 Classification . 6
6 Surface mounting of components . 7
6.1 General . 7
6.2 Alignment requirements . 7
6.3 Process control . 7
6.4 Surface mounted component requirements . 7
6.5 Flatpack lead forming . 7
6.5.1 General . 7
6.5.2 Surface mounted device lead bends . 8
6.5.3 Surface mounted device lead deformation . 8
6.5.4 Flattened leads . 8
6.5.5 Dual-in-line packages (DIPs) . 8
6.5.6 Parts not configured for surface mounting . 9
6.6 Small devices with two terminations . 9
6.6.1 General . 9
6.6.2 Stack mounting . 9
6.6.3 Devices with external deposited elements . 9
6.7 Lead component body positioning . 9
6.7.1 General . 9
6.7.2 Axial-leaded components . 9
6.7.3 Other components . 9
6.8 Parts configured for butt lead mounting . 9
6.9 Non-conductive adhesive coverage limits . 10
7 Acceptance requirements . 10
7.1 General . 10
7.2 Control and corrective actions . 10
7.3 Surface soldering of leads and terminations . 10
7.3.1 General . 10
7.3.2 Solder fillet height and heel fillets . 10
7.3.3 Flat ribbon L and gull-wing leads . 13
7.3.4 Round or flattened (coined) leads . 13
7.3.5 J leads. 15
7.3.6 Rectangular or square end components . 16
7.3.7 Cylindrical end cap terminations . 17
7.3.8 Bottom only terminations . 18
7.3.9 Leadless chip carriers with castellated terminations . 19
7.3.10 Butt joints . 20
7.3.11 Inward L-shaped ribbon leads . 21
7.3.12 Flat lug leads . 22
7.4 General post-soldering requirements applicable to all surface-mounted
assemblies . 23

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61191-2 © IEC:2013 – 3 –
7.4.1 Dewetting . 23
7.4.2 Leaching. 23
7.4.3 Pits, voids, blowholes, and cavities . 23
7.4.4 Solder wicking . 23
7.4.5 Solder webs and skins . 23
7.4.6 Bridging . 23
7.4.7 Degradation of marking . 23
7.4.8 Solder spikes . 23
7.4.9 Disturbed joint . 23
7.4.10 Component damage . 24
7.4.11 Open circuit, non-wetting . 24
7.4.12 Component tilting . 24
7.4.13 Non-conducting adhesive encroachment . 24
7.4.14 Open circuit, no solder available (skip) . 24
7.4.15 Component on edge . 24
8 Rework and repair . 24
Annex A (normative) Placement requirements for surface mounted devices . 26

Figure 1 – Lead formation for surface mounted device . 8
Figure 2 – Fillet height . 12
Figure 3 – Flat ribbon L and gull-wing leads . 13
Figure 4 – Round or flattened (coined) lead joint . 14
Figure 5 – J lead joint . 15
Figure 6 – Rectangular or square end components . 16
Figure 7 – Cylindrical end-cap terminations . 17
Figure 8 – Bottom only terminations . 18
Figure 9 – Leadless chip carriers with castellated terminations . 19
Figure 10 – Butt joints . 20
Figure 11 – Inward L-shaped ribbon leads . 21
Figure 12 – Flat lug leads . 22

Table 1 – Surface mounted solder joint defects . 25

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– 4 – 61191-2 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_____________

PRINTED BOARD ASSEMBLIES –

Part 2: Sectional specification –
Requirements for surface mount soldered assemblies

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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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
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61191-2 has been prepared by IEC technical committee 91:
Electronics assembly technology.
This second edition cancels and replaces the first edition, published in 1998, and constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– IPC-A-610 on workmanship has been included as a normative reference;
– some of the terminology used in the document has been updated;
– references to IEC standards have been corrected;
– the use of lead-free solder paste and plating are addressed.

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61191-2 © IEC:2013 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
91/1091/FDIS 91/1103/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 61191 under the general title Printed board assemblies can be found
in 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.

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– 6 – 61191-2 © IEC:2013
PRINTED BOARD ASSEMBLIES –

Part 2: Sectional specification –
Requirements for surface mount soldered assemblies



1 Scope
This part of IEC 61191 gives the requirements for surface mount solder connections. The
requirements pertain to those assemblies that are totally surface mounted or to the surface
mounted portions of those assemblies that include other related technologies (e.g. through-
hole, chip mounting, terminal mounting, etc.).
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 61191-1:2013, Printed board assemblies – Part 1: Generic specification – Requirements
for soldered electrical and electronic assemblies using surface mount and related assembly
technologies
IPC-A-610E:2010, Acceptability of Electronic Assemblies
3 Conventions
Unless otherwise specified by the user, the word "shall" signifies that the requirement is
mandatory. Deviations from any "shall" requirement requires written acceptance by the user,
e.g. via assembly drawing, specification or contract provision.
The word “should” is used to indicate a recommendation or guidance statement. The word
“may” indicates an optional situation. Both “should” and “may” express non-mandatory
situations. “Will” is used to express a declaration of purpose.
4 General requirements
Clause 4 of IEC 61191-1:2013 is a mandatory part of this standard.
Workmanship of surface mount assemblies shall meet the requirements of IPC-A-610E in
accordance with the classification requirements of this standard.
5 Classification
This standard recognizes that electrical and electronic assemblies are subject to
classifications by intended end-item use. Three general end-product classes have been
established to reflect differences in producibility, complexity, functional performance
requirements, and verification (inspection/test) frequency. These are the following:
Level A: General electronic products
Level B: Dedicated service electronic products

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61191-2 © IEC:2013 – 7 –
Level C: High performance electronic products
The user of the assemblies is responsible for determining the level to which his product
belongs. It should be recognized that there may be overlaps of equipment between levels.
The contract shall specify the level required and indicate any exceptions or additional
requirements to the parameters, where appropriate (see 4.3 of IEC 61191-1:2013).
6 Surface mounting of components
6.1 General
This clause covers assembly of components that are placed on the surface to be manually or
machine soldered and includes components designed for surface mounting as well as
through-hole components that have been adapted for surface mounting technology.
6.2 Alignment requirements
Sufficient process control at all stages of design and assembly shall be in place to enable the
post-soldering alignments and solder joint fillet controls specified in 7.3 to be achieved.
Relevant factors affecting the requirements include land and conductor design, component
proximities, component and land solderability, solder paste/adhesive quantity and alignment
and component placement accuracy.
6.3 Process control
If suitable process controls are not in place to ensure compliance with 6.2 and the intent of
Annex A, the detailed requirements of Annex A shall be mandatory.
6.4 Surface mounted component requirements
The leads of lead surface mounted components shall be formed to their final configuration
prior to mounting. Leads shall be formed in such a manner that the lead-to-body seal is not
damaged or degraded and that they may be soldered into place by subsequent processes
which do not result in residual stresses decreasing reliability. When the leads of dual-in-line
packages, flatpacks, and other multilead devices become misaligned during processing or
handling, they may be straightened to ensure parallelism and alignment prior to mounting,
while maintaining the lead-to-body seal integrity.
6.5 Flatpack lead forming
6.5.1 General
Leads on opposite sides of surface mounted flatpacks shall be formed such that the
non-parallelism between the base surface of the component and the surface of the printed
board (i.e. component cant) is minimal. Component cant is permissible provided the final
configuration does not exceed the maximum spacing limit of 2,0 mm (see Figure 1).

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– 8 – 61191-2 © IEC:2013

IEC  1364/13

Figure 1 – Lead formation for surface mounted device
6.5.2 Surface mounted device lead bends
Leads shall be supported during forming to protect the lead-to-body seal. Bends shall not
extend into the seal (see Figure 1). The lead-bend radius (R) shall be >1 T (T = nominal lead
thickness). The angle of that part of the lead between the upper and lower bends in relation to
the mounting land shall be 45° minimum and 90° maximum.
6.5.3 Surface mounted device lead deformation
Lead deformation (unintentional bending) may be allowed when
a) no evidence of a short circuit or potential short circuit exists,
b) lead-to-body seal or weld is not damaged by the deformation,
c) does not violate minimum electrical spacing requirement,
d) top of lead does not extend beyond the top of body; preformed stress loops may extend
above the top of the body; however, stand-off height limit shall not be exceeded,
e) toe curl, if present on bends, shall not exceed two times the thickness of the lead (2 T),
f) coplanarity limits are not exceeded.
6.5.4 Flattened leads
Components with axial leads of round cross-section may be flattened (coined) for positive
seating in surface mounting. If flattening is used, the flattened thickness shall be not less than
40 % of the original diameter. Flattened areas of leads shall be excluded from the 10 %
deformation requirement in 6.5.3 of IEC 61191-1:2013.
Flattened leads on opposite sides of a surface mount part shall be formed such that the non-
parallelism between the base surface of the component and the surface of the printed board
(e.g., component cant) is minimal.
6.5.5 Dual-in-line packages (DIPs)
Dual-in-line packages may be surface mounted provided the leads are configured to meet the
mounting requirements for surface mounted loaded parts. The lead preparation operation
shall be performed using die forming/cutting systems. Hand forming and trimming of leads are
prohibited.

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61191-2 © IEC:2013 – 9 –
6.5.6 Parts not configured for surface mounting
Flatpacks of the through-hole configuration, transistors, metal power packages, and other
non-axial lead components shall not be surface mounted unless the leads are formed to meet
the surface mounted device lead forming requirements. Such applications shall be agreed on
between user and manufacturer.
6.6 Small devices with two terminations
6.6.1 General
The detailed requirements for mounting of small devices with two lead terminations are
defined in the following subclauses.
6.6.2 Stack mounting
When part stacking is permitted by the assembly drawing, parts shall not bridge spacing
between other parts or components such as terminals or other chip components.
6.6.3 Devices with external deposited elements
Components with electrical elements deposited on an external surface (such as chip resistors)
shall be mounted with that surface facing away from the printed board or substrate.
6.7 Lead component body positioning
6.7.1 General
Parts mounted over protected surfaces and insulated parts that are positioned over circuitry
or parts mounted over surfaces without exposed circuitry may be flush mounted (i.e. no stand-
off height). Parts mounted over exposed circuitry shall have their leads formed to provide a
minimum of 0,25 mm between the bottom of the component body and the exposed circuitry.
The maximum clearance between the bottom of the leaded component body and the printed
wiring surface shall not exceed 2,0 mm.
6.7.2 Axial-leaded components
The body of a surface mounted axial-leaded component should be spaced from the surface of
the printed board at a maximum of 2,0 mm unless the component is mechanically attached to
the substrate by adhesive or other means. Leads on opposite sides of surface mounted
axial-leaded components shall be formed such that component cant (non-parallelism between
the base surface of the mounted component and the surface of the printed board) is minimal
and in no instance shall body cant result in non-conformance with maximum spacing limits.
6.7.3 Other components
TO-can devices, tall profile components (i.e. over 15 mm), transformers, and metal power
packages may be surface mounted provided the parts are bonded or otherwise secured to the
board in a manner which enables the part to withstand the end-item shock, vibration and
environmental stresses.
6.8 Parts configured for butt lead mounting
Components designed for through hole (pin-in-hole) applications and modified for butt joint
attachment, or stiff leaded dual-in-line packages may be butt mounted on level A and B
products. Butt mounting is not permitted on level C products unless the component is
designed for surface mounting.

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– 10 – 61191-2 © IEC:2013
6.9 Non-conductive adhesive coverage limits
Non-conductive adhesive materials, when used for component mounting, shall not flow onto,
or obscure, areas to be soldered or into vias or plated-through holes.
7 Acceptance requirements
7.1 General
Materials, processes, and procedures described and specified in IEC 61191-1 provide for
soldered interconnections that are better than the minimum surface mount acceptance
requirements in this clause. Processes and their c
...