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

IEC 61191-2:2017 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:
a) the requirements have been updated to be compliant with the acceptance criteria in IPC‑A-610F;
b) some of the terminology used in the document has been updated;
c) references to IEC standards have been corrected;
d) five termination styles have been added.
The contents of the corrigendum of September 2019 have been included in this copy.

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

L’IEC 61191-2:2017 spécifie 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:
a) mise à jour des exigences pour qu’elles soient conformes aux critères d’acceptation de l’IPC‑A-610F;
b) mise à jour d’une partie de la terminologie utilisée dans le présent document;
c) correction des références aux normes IEC;
d) ajout de cinq styles de terminaisons.

General Information

Status
Published
Publication Date
22-May-2017
Current Stage
PPUB - Publication issued
Start Date
23-May-2017
Completion Date
23-May-2017
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IEC 61191-2
Edition 3.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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 61191-2:2017-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61191-2
Edition 3.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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
INTERNATIONALE
ICS 31.190; 31.240 ISBN 978-2-8322-7400-2

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
---------------------- Page: 3 ----------------------
– 2 – IEC 61191-2:2017 © IEC 2017
CONTENTS

CONTENTS ............................................................................................................................ 2

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 General requirements ...................................................................................................... 7

5 Surface mounting of components ..................................................................................... 7

5.1 General ................................................................................................................... 7

5.2 Alignment requirements .......................................................................................... 8

5.3 Process control ....................................................................................................... 8

5.4 Surface mounted component requirements ............................................................. 8

5.5 Flatpack lead forming .............................................................................................. 8

5.5.1 General ........................................................................................................... 8

5.5.2 Surface mounted device lead bends ................................................................ 8

5.5.3 Surface mounted device lead deformation ....................................................... 9

5.5.4 Flattened leads ................................................................................................ 9

5.5.5 Dual-in-line packages (DIPs) ........................................................................... 9

5.5.6 Parts not configured for surface mounting ........................................................ 9

5.6 Small devices with two terminations ........................................................................ 9

5.6.1 General ........................................................................................................... 9

5.6.2 Stack mounting ................................................................................................ 9

5.6.3 Devices with external deposited elements ........................................................ 9

5.7 Lead component body positioning ......................................................................... 10

5.7.1 General ......................................................................................................... 10

5.7.2 Axial-leaded components ............................................................................... 10

5.7.3 Other components ......................................................................................... 10

5.8 Parts configured for butt lead mounting ................................................................. 10

5.9 Non-conductive adhesive coverage limits .............................................................. 10

6 Acceptance requirements .............................................................................................. 10

6.1 General ................................................................................................................. 10

6.2 Control and corrective actions ............................................................................... 10

6.3 Surface soldering of leads and terminations .......................................................... 11

6.3.1 General ......................................................................................................... 11

6.3.2 Solder fillet height and heel fillets .................................................................. 11

6.3.3 Flat ribbon L and gull-wing leads ................................................................... 12

6.3.4 Round or flattened (coined) leads .................................................................. 13

6.3.5 J leads ........................................................................................................... 14

6.3.6 Rectangular or square end component .......................................................... 15

6.3.7 Cylindrical end-cap terminations .................................................................... 16

6.3.8 Bottom only terminations ............................................................................... 17

6.3.9 Castellated terminations ................................................................................ 18

6.3.10 Butt joints ...................................................................................................... 19

6.3.11 Inward L-shaped ribbon leads ........................................................................ 20

6.3.12 Flat lug leads ................................................................................................. 21

6.3.13 Ball grid array ................................................................................................ 22

6.3.14 Column grid array .......................................................................................... 23

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IEC 61191-2:2017 © IEC 2017 – 3 –

6.3.15 Bottom termination components ..................................................................... 24

6.3.16 Components with bottom thermal plane terminations (D-Pak) ........................ 24

6.3.17 P-style terminations ....................................................................................... 26

6.4 General post-soldering requirements applicable to all surface-mounted

assemblies ............................................................................................................ 26

6.4.1 Dewetting ...................................................................................................... 26

6.4.2 Leaching ........................................................................................................ 26

6.4.3 Pits, voids, blowholes, and cavities ................................................................ 26

6.4.4 Solder wicking ............................................................................................... 27

6.4.5 Solder webs and skins ................................................................................... 27

6.4.6 Bridging ......................................................................................................... 27

6.4.7 Degradation of marking ................................................................................. 27

6.4.8 Solder spikes ................................................................................................. 27

6.4.9 Disturbed joint ............................................................................................... 27

6.4.10 Component damage....................................................................................... 27

6.4.11 Open circuit, non-wetting ............................................................................... 27

6.4.12 Component tilting........................................................................................... 27

6.4.13 Non-conducting adhesive encroachment ........................................................ 28

6.4.14 Open circuit, no solder available .................................................................... 28

6.4.15 Component on edge ...................................................................................... 28

7 Rework and repair ......................................................................................................... 28

Annex A (normative) Placement requirements for surface mounted devices ......................... 30

A.1 General ................................................................................................................. 30

A.2 Component positioning ......................................................................................... 30

A.3 Small devices incorporating two terminations ........................................................ 30

A.3.1 Metallization coverage over the land (side-to-side) ........................................ 30

A.3.2 Metallization coverage over the land (end) ..................................................... 30

A.4 Mounting of cylindrical end-cap devices (MELFs) .................................................. 30

A.5 Registration of castellated chip carriers ................................................................ 30

A.6 Surface mounted device lead and land contact ..................................................... 30

A.7 Surface mounted device lead side overhang ......................................................... 30

A.8 Surface mounted device lead toe overhang ........................................................... 31

A.9 Surface mounted device lead height off land (prior to soldering) ........................... 31

A.10 Positioning of J lead devices ................................................................................. 31

A.11 Positioning gull-wing lead devices ......................................................................... 31

A.12 External connections to packaging and interconnect structures ............................. 31

Bibliography .......................................................................................................................... 32

Figure 1 – Lead formation for surface mounted device ............................................................ 8

Figure 2 – Fillet height .......................................................................................................... 12

Figure 3 – Flat ribbon 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

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– 4 – IEC 61191-2:2017 © IEC 2017

Figure 10 – Butt joints ........................................................................................................... 20

Figure 11 – Inward L-shaped ribbon leads ............................................................................ 21

Figure 12 – Flat lug leads ..................................................................................................... 22

Figure 13 – BGA with collapsing balls ................................................................................... 23

Figure 14 – Bottom termination components ......................................................................... 24

Figure 15 – Bottom thermal plane terminations ..................................................................... 25

Figure 16 – P-style terminations ........................................................................................... 26

Table 1 – BGA with non-collapsing balls ............................................................................... 23

Table 2 – Column grid array .................................................................................................. 23

Table 3 – Reworkable defects ............................................................................................... 29

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IEC 61191-2:2017 © IEC 2017 – 5 –
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

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

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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

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

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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

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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 61191-2 has been prepared by IEC technical committee 91:

Electronics assembly technology.

This bilingual version (2019-09) corresponds to the monolingual English version, published in

2017-05.

This third edition cancels and replaces the second edition published in 2013. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) the requirements have been updated to be compliant with the acceptance criteria in

IPC-A-610F;
b) some of the terminology used in the document has been updated;
---------------------- Page: 7 ----------------------
– 6 – IEC 61191-2:2017 © IEC 2017
c) references to IEC standards have been corrected;
d) five termination styles have been added.
The text of this International Standard is based on the following documents:
CDV Report on voting
91/1386/CDV 91/1429/RVC

Full information on the voting for the approval of this International 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 document 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 document will remain unchanged until the

stability date indicated on the IEC website under "http://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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 8 ----------------------
IEC 61191-2:2017 © IEC 2017 – 7 –
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 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 60194, Printed board design, manufacture and assembly – Terms and definitions

IEC 61191-1, Printed board assemblies – Part 1: Generic specification – Requirements for

soldered electrical and electronic assemblies using surface mount and related assembly

technologies
IPC-A-610, Acceptability of Electronic Assemblies
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60194 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 http://www.iso.org/obp
4 General requirements
The requirements of IEC 61191-1 are a mandatory part of this specification.

Workmanship shall meet the requirements of IPC-A-610 in accordance with the classification

requirements of this document.
5 Surface mounting of components
5.1 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.
---------------------- Page: 9 ----------------------
– 8 – IEC 61191-2:2017 © IEC 2017
5.2 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 6.3 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.
5.3 Process control

If suitable process controls are not in place to ensure compliance with 5.2 and the intent of

Annex A, the detailed requirements of Annex A shall be mandatory.
5.4 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.
5.5 Flatpack lead forming
5.5.1 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).

No bend
into the seal
45° – 90° R
≤ 2,0 mm
IEC
Key
R lead-bend radius
T nominal lead thickness
Figure 1 – Lead formation for surface mounted device
5.5.2 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

---------------------- Page: 10 ----------------------
IEC 61191-2:2017 © IEC 2017 – 9 –

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.
5.5.3 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.
5.5.4 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.
5.5.5 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
...

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