IEC TS 62647-23:2013

IEC/TS 62647-23 ®
Edition 1.0 2013-10
TECHNICAL
SPECIFICATION
colour
inside
Process management for avionics – Aerospace and defence electronic systems
containing lead-free solder –
Part 23: Rework and repair guidance to address the implications of lead-free
electronics and mixed assemblies

IEC/TS 62647-23:2013(E)
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.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
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 corrigenda or an amendment might have been published.

Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: csc@iec.ch.

IEC/TS 62647-23 ®
Edition 1.0 2013-10
TECHNICAL
SPECIFICATION
colour
inside
Process management for avionics – Aerospace and defence electronic systems

containing lead-free solder –
Part 23: Rework and repair guidance to address the implications of lead-free

electronics and mixed assemblies

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-8322-1162-5

– 2 – TS 62647-23  IEC:2013(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviations . 9
3.1 Terms and definitions . 9
3.2 Abbreviations . 14
4 Pb-free concerns . 16
4.1 General . 16
4.2 Reliability . 16
4.2.1 General . 16
4.2.2 Mixed metallurgy reliability. 16
4.3 Configuration management . 17
4.4 Risk management . 18
4.5 Tin whiskers . 18
4.6 Copper dissolution (erosion) . 18
5 Materials . 18
5.1 Solder . 18
5.1.1 General . 18
5.1.2 Solder alloys . 18
5.1.3 Solder forms . 19
5.2 Fluxes . 20
5.3 Piece parts . 20
5.3.1 General . 20
5.3.2 Termination finishes . 20
5.3.3 Area arrays (BGA, CSP, etc.) . 20
5.4 Printed circuit boards/printed wiring boards . 21
5.4.1 Laminate material . 21
5.4.2 Surface finish . 21
5.5 Conformal coatings . 21
6 Soldering equipment . 22
6.1 General . 22
6.2 Hand soldering equipment . 22
6.2.1 General hand soldering equipment considerations . 22
6.2.2 Tip selection . 22
6.2.3 Soldering iron tip life . 23
6.3 Fountain soldering . 24
6.4 Convective soldering equipment . 25
6.4.1 General . 25
6.4.2 Thermal profile issues. 25
7 General rework/repair considerations . 26
7.1 General . 26
7.2 Rework/repair procedure order of precedence . 26
7.3 Technician training . 27
7.4 Pb-free rework/repair considerations . 27
7.4.1 General . 27

TS 62647-23  IEC:2013(E) – 3 –
7.4.2 General process considerations . 27
7.4.3 Solder processing considerations . 28
7.4.4 Flux considerations . 28
8 Pre-rework/repair processes . 29
8.1 Alloy identification . 29
8.1.1 IPC/JEDEC J-STD-609A . 29
8.1.2 X-ray fluorescence (XRF) . 31
8.1.3 Pb swabs . 31
8.2 Piece part and CCA preparation . 31
8.2.1 General . 31
8.2.2 Piece part preparation . 31
8.2.3 CCA preparation . 32
9 Rework/repair processes . 32
9.1 General . 32
9.2 Conductive hand soldering . 32
9.3 Convective soldering process . 34
9.3.1 General . 34
9.3.2 Solder paste handling . 34
9.3.3 Paste printing . 34
9.3.4 Reflow process . 34
10 Post-rework/repair processes . 36
10.1 Cleaning . 36
10.2 Inspection . 36
10.3 Reapplication of conformal coating . 36
Annex A (informative) Termination finishes . 37
Annex B (informative) Tin whiskers . 39
B.1 Tin whisker growth mechanisms . 39
B.2 Tin whisker mitigation techniques. 39
B.3 Hot solder dip . 39
B.4 Conformal coatings . 39
B.5 Specification of piece part termination finish . 40
B.6 Under-platings/annealing . 40
B.7 Piece part lead pitch . 40
Bibliography . 44

Figure 1 – Soldering iron tip construction . 23
Figure 2 – Worn soldering iron tip . 23
Figure 3 – Copper dissolution . 24

Table 1 – Assembly and piece part marking methods . 30
Table A.1 – Piece-part terminal and BGA ball metallization solder process
compatibility risk (see IEC/TS 62647-22:2013) . 37
Table A.2 – BGA piece parts risk . 38
Table B.1 – Tin whisker information (see IEC/TS 62647-22:2013) . 41
Table B.2 – Piece part termination tin whisker risks (see IEC/TS 62647-22:2013) . 42

– 4 – TS 62647-23  IEC:2013(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC
SYSTEMS CONTAINING LEAD-FREE SOLDER –

Part 23: Rework and repair guidance to address the implications
of lead-free electronics and mixed 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,
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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62647-23, which is a technical specification, has been prepared by IEC technical
committee 107: Process management for avionics.

TS 62647-23  IEC:2013(E) – 5 –
The text of this technical specification is based on the following document:
IEC/PAS 62647-23 .
This technical specification cancels and replaces IEC/PAS 62647-23, published in 2011. This
edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Coherence with IEC/TS 62647-1, IEC/TS 62647-2 and IEC/TS 62647-21 definitions.
b) Reference to IEC 62647 documents when already published.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
107/206/DTS 107/219/RVC
Full information on the voting for the approval of this technical specification 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 in the IEC 62647 series, published under the general title Process
management for avionics – Aerospace and defence electronic systems containing lead-free
solder, can be found on 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
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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.
___________
IEC/PAS 62647-23, which served as a basis for the present document, is also known as GEIA-HB-0005-3.

– 6 – TS 62647-23  IEC:2013(E)
INTRODUCTION
0.1 General
The global transition to lead-free (Pb-free) electronics impacts the aerospace, defence and
high performance (ADHP) industry and other industries having high reliability applications in
various ways.
This document is intended to facilitate the development of procedures and processes for use
when undertaking the rework/repair of aerospace, defence, and high performance (ADHP)
electronics systems. It is intended to contain sufficient information to support the processing
of equipment that incorporates either tin-lead (Sn-Pb) or lead-free (Pb-free) solder alloy, Sn-
Pb or lead-free (Pb-free) piece parts and printed circuit board (PCB)/printed wiring board
(PWB) finishes, or a combination thereof.
This document may be used by original equipment manufacturers (OEMs), contract
manufacturers (CMs) and commercial depots. This document may also be used by personnel
performing rework/repair at the organizational (O) level, intermediate (I) back shop level, and
depot (D) overhaul level.
0.2 Pb-free and legislation
Recent directives and legislation by nations around the world mandated elimination of lead
and other hazardous material usage in sectors of the electronics industry by 2006. In
electronics, lead (Pb) has been a primary component of tin-lead (Sn-Pb) solder used in piece
part attachment and PCB/PWB finishes for over 50 years, and more recently in the solder
spheres for attachment of ball grid array (BGA) packages. Since there is no “drop-in”
replacement for Sn-Pb solder alloys, multiple Pb-free alloys have emerged in the
manufacturing industry as replacements. These multiple replacement alloys are being used in
printed circuit boards (PCBs)/printed wiring boards (PWBs) finish, piece part termination finish
and as solder alloys, leaving the rework/repair technician with literally hundreds of possible
combinations of metallurgy in the finished repair.
The majority of the Pb-free alloys being considered have melting temperatures 34 °C to 44 °C
(61 °F to 79 °F) higher than that of tin-lead (Sn-Pb) eutectic solder. These higher Pb-free
processing temperatures require significant changes to convective rework/repair procedures
and minor adjustments in conductive hand soldering procedures to ensure that quality
products will be produced.
Another major concern is the potential re-emergence of tin whiskers as an additional
equipment failure mechanism. Tin whiskers are electrically conductive, crystalline structures
of tin (Sn) that grow under compressive force from surfaces where tin (Sn) (especially
electroplated tin (Sn)) is used as a final finish. Tin whiskers have been observed to grow to
lengths of several millimeters (mm). Numerous electronic system failures have been attributed
to short circuits caused by tin whiskers that bridge closely-spaced circuit elements. Tin
whiskers have been successfully suppressed for decades by the addition of lead (Pb) to tin
(Sn) plating used in high reliability applications. With the global shift to Pb-free solders, tin
whiskers have re-emerged as a major concern to reliability. IEC/TS 62647-2:2012 further
discusses tin whisker issues and mitigation techniques.
Procedurally, conductive Pb-free rework/repair is similar to that of Sn-Pb. However,
adjustments should be made to accommodate the generally poorer wetting ability of Pb-free
solders as well as differences in appearance and inspection criteria. Convective rework/repair
will require redevelopment of profiles to accommodate the higher melting temperature of Pb-
free alloys. Also, Pb-free rework/repair has a tighter process window leaving a smaller margin

TS 62647-23  IEC:2013(E) – 7 –
for error in comparison to Sn-Pb. With the proper materials, preparation, skill, and the use of
fundamentally sound procedures, Pb-free rework/repair can be successfully and reliably
accomplished [28] .
___________
Numbers in square brackets refer to the Bibliography.

– 8 – TS 62647-23  IEC:2013(E)
PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC
SYSTEMS CONTAINING LEAD-FREE SOLDER –

Part 23: Rework and repair guidance to address the implications
of lead-free electronics and mixed assemblies

1 Scope
This part of IEC 62647 provides technical background, procurement guidance, engineering
procedures, and guidelines to assist organizations reworking/repairing aerospace and high
performance electronic systems, whether they were assembled or previously
reworked/repaired using traditional alloys such as Sn-Pb or Pb-free alloys, or a combination
of both solders and surface finishes. This document contains a review of known impacts and
issues, processes for rework/repair, focused to provide the technical structure to allow the
repair technician to execute the task.
This document focuses on the removal and replacement of piece parts. For the purposes of
this document, the term “rework/repair” is used as defined in 3.1.29 and 3.1.30.
The information contained within this document is based on the current knowledge of the
industry at the time of publication. Due to the rapid changing knowledge base, this document
should be used for guidance only.
NOTE 1 For the purposes of this document, if the element “lead” is implied, it will be stated either as Pb, as lead
(Pb), or as tin-lead. If a piece part terminal or termination “lead” is referred to, such as in a flat pack or a dual-
inline package, the nomenclature lead/terminal or lead-terminal will be used.
NOTE 2 Processes identified in the document apply to either rework or repair.
This document may be used by other high-performance and high-reliability industries, at their
discretion.
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/TS 62647-1:2012, Process management for avionics – Aerospace and defence
electronics systems containing lead free solder – Part 1: Preparation for a lead-free control
plan
IEC/TS 62647-2:2012, Process management for avionics – Aerospace and defence electronic
systems containing lead-free solder – Part 2: Mitigation of deleterious effects of tin
IEC/TS 62647-22:2013, Process management for avionics – Aerospace and defence
electronic systems containing lead-free solder – Part 22: Technical guidelines

TS 62647-23  IEC:2013(E) – 9 –
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
alloy composition
whole ingredients of an alloy whose weight is defined in percent
Note 1 to entry: For instance 63Sn-37Pb corresponds to a mixture of 63 % by weight of tin (Sn) and 37 % by
weight of lead (Pb).
[SOURCE: IEC/TS 62647-22:2013, 3.1.1]
3.1.2
assemblies
electronic items that require electrical attachments, including soldering of wires or component
terminations
EXAMPLE: Circuit cards and wire harnesses.
[SOURCE: IEC/TS 62647-1:2012, 3.1]
3.1.3
backwards compatibility
Pb-free materials compatible with an Sn-Pb process
3.1.4
CTE
coefficient of thermal expansion
degree of expansion of a material divided by the change in temperature
Note 1 to entry: PCB/PWB CTE (x-y axis) is measured in the direction in the plane of the piece part mounting
surface and is used to quantify the stresses in the solder joint arising from the differences in CTE between the
piece parts and the PCB/PWB during thermal cycling. CTE (z axis) is measured in the “thickness” direction and is
typically used to quantify plated through hole stress.
[SOURCE: IEC/TS 62647-22:2013, 3.1.8]
3.1.5
conductive
use of a contact heat source such as a soldering iron, hot bar, or resistance to transfer heat to
the assembly
3.1.6
convective
use of a non-contact heat source, usually heated air, nitrogen or infrared light to transfer heat
to the assembly
3.1.7
copper dissolution
excessive loss of copper from plated through hole barrels and pads caused by wave or solder
fountain processing primarily with high tin (Sn) content solders
3.1.8
critical
state of an item or function, which if defective, will result in the system’s inability to retain
operational capability, meet primary objective, or affect safety

– 10 – TS 62647-23  IEC:2013(E)
[SOURCE: IEC/TS 62647-1:2012, 3.2]
3.1.9
customer
entity or organization that (a) integrates a piece part, soldered assembly, unit, or system into
a higher control level system, (b) operates the higher control level system, or (c) certifies the
system for use
EXAMPLE: This may include end item users, integrators, regulatory agencies, operators, original equipment
manufacturers (OEMs), and subcontractors.
[SOURCE: IEC/TS 62647-1:2012, 3.5]
3.1.10
delamination
separation between plies within a base material, between a base material and a conductive
foil, or any other planar separation with a printed board that may propagate under thermal
stress
3.1.11
D
depot level maintenance
maintenance requiring major overhaul or a complete rebuilding of parts, assemblies,
subassemblies, and end items, including the manufacture of parts, modifications, testing, and
reclamation as required.
Note 1 to entry: Depot maintenance serves to support lower categories of maintenance by providing technical
assistance and performing that maintenance beyond their responsibility.
3.1.12
dissolution
process in which one substance is dissolved in another by chemical action
3.1.13
eutectic
mixture of two or more metals at a composition that has the lowest melting point, and where
the phases simultaneously crystallize from molten solution at this temperature
Note 1 to entry: A non-eutectic mixture will exhibit a pasty range during cooling where both liquid and solid
phases are present prior to reaching the mixture’s solidus temperature.
[SOURCE: IEC/TS 62647-22:2013, 3.1.12]
3.1.14
high performance
continued performance or performance on demand where an application (product, equipment,
electronics, system, program) down time cannot be tolerated in an end-use environment
which can be uncommonly harsh, and the application must function when required
EXAMPLE: Examples of high performance applications are life support or other critical systems.
[SOURCE: IEC/TS 62647-1:2012, 3.7]
3.1.15
I
intermediate level maintenance
repair operation of aircraft and engine components, WRAs, and LRUs forwarded to the
intermediate level by the organizational level flight-line activities

TS 62647-23  IEC:2013(E) – 11 –
Note 1 to entry: This consists either in limited repair operation of commodity-orientated piece parts and end items,
job shop, bay, and production line operations for special mission requirements or in repair of printed circuit boards
(PCBs)/printed wiring boards (PWBs), software maintenance, and fabrication or manufacture of repair parts,
assemblies, piece parts. WRA and LRU repair is accomplished by the removal, troubleshooting, and replacement of
faulty SRA and SRU, pieces, and parts within the WRA/LRU.
3.1.16
lead-free
Pb-free
less than 0,1 % by weight of lead (Pb) in accordance with reduction of hazardous substances
(RoHS) guidelines
[SOURCE: IEC/TS 62647-1:2012, 3.8]
3.1.17
lead-free control plan
LFCP
aerospace or military system supplier’s document that defines the processes that assure the
Plan owners, their customers and all other stakeholders that aerospace, defence and high
performance high-reliability electronics systems containing Pb-free solder and Pb-free piece
part and PWB finishes will continue to be reliable, safe, producible, affordable, and
supportable
[SOURCE: IEC/TS 62647-1:2012, 3.9]
3.1.18
liquidus
minimum temperature at which all components of a mixture (such as an alloy) can be in a
liquid state
Note 1 to entry: Below liquidus, the mixture will be partly or entirely solid.
3.1.19
measling
condition that occurs in laminated base material in which internal glass fibers are separated
from the resin at the weave intersection
Note 1 to entry: This condition manifests itself in the form of discrete white spots or “crosses” that are below the
surface of the base material.
3.1.20
organization
organizational structure typically consisting of program management, procurement, process
engineering, bench technicians, and quality assurance personnel
3.1.21
O
organizational level maintenance
maintenance normally performed by an operating unit on a day-to-day basis in support of its
own operations
Note 1 to entry: Organizational level maintenance typically includes "inspections”, "servicing”, "handling" and
"preventive maintenance” and is limited to the replacement of electronic assemblies at the WRA and LRU (black
box) level of major aircraft and engine components. There can be an exception when troubleshooting and piece
parts level repair are accomplished at the organizational level.
3.1.22
Pb-free tin
pure tin or any tin alloy with < 3 % lead (Pb) content by weight

– 12 – TS 62647-23  IEC:2013(E)
Note 1 to entry: Some Pb-free finishes other than pure tin, such as tin-bismuth and tin-copper are considered to
be “tin” for the purposes of this specification. Many of these alloys have not been assessed for whiskering
behaviour.
[SOURCE: IEC/TS 62647-1:2012, 3.11]
3.1.23
Pb-free tin finish
final finishes or under-plates either external or internal to a device, board or other hardware,
including all leads and surfaces, even those coated, encapsulated, or otherwise not exposed
Note 1 to entry: It may include finishes on electrical piece parts, mechanical piece parts, and boards. It does not
include Pb-free bulk solders, assembly materials, solder balls, or those devices where the Pb-free tin finish has
been completely replaced.
[SOURCE: IEC/TS 62647-1:2012, 3.12]
3.1.24
PCB
printed circuit board
PWB
printed wiring board
substrate using conductive pathways, tracks or signal traces etched from copper sheets
laminated, and allowing to connect electrically a set of electronic components to realize a
circuit card.
[SOURCE: IEC/TS 62647-21:2013, 3.1.10]
3.1.25
piece part
electronic component that is not normally disassembled without destruction and is normally
attached to a printed wiring board to perform an electrical function
[SOURCE: IEC/TS 62647-1:2012, 3.14]
3.1.26
procurement
process of obtaining services, supplies, and equipment
3.1.27
PTH
plated through hole
plated through holes used on printed circuit boards (PCBs)/printed wiring boards (PWBs) for
interconnecting between layers and for component attachment
[SOURCE: IEC/TS 62647-22:2013, 3.1.26]
3.1.28
quality assurance
planned and systematic set of activities to ensure that requirements are clearly established
and that the defined process or product complies with these requirements
3.1.29
repair
act of restoring the functional capability of a defective article in a manner that precludes
compliance of the article with applicable drawings or specifications
[SOURCE: IEC/TS 62647-1:2012, 3.17]

TS 62647-23  IEC:2013(E) – 13 –
3.1.30
rework
action taken to return a unit (SRU/LRU/system) to a state meeting all requirements of the
engineering drawing, including both functionality and physical configuration by making repairs
Note 1 to entry: Also used to define the act of reprocessing non-complying articles, through the use of original or
equivalent processing in a manner that assures full compliance of the article with applicable drawings or
specifications.
[SOURCE: IEC/TS 62647-1:2012, 3.16]
3.1.31
SAC
family of Pb-free alloys containing tin, silver and copper used in surface mount technology or
sometimes in wave solder processes
Note 1 to entry: The alloys typically have a composition near the eutectic (95,6Sn-3,5Ag-0,9Cu)
[SOURCE: IEC/TS 62647-22:2013, 3.1.29]
3.1.32
SRA
shop replaceable assembly
SRU
shop replaceable unit
component assembly inside a black box (LRU or WRA) typically consisting of individually
replaceable circuit card assemblies
3.1.33
Sn-Cu
solder or alloy referring to Pb-free alloys that are comprised of tin-copper (Sn-0,7Cu)
[SOURCE: IEC/TS 62647-22:2013, 3.1.32]
3.1.34
Sn-Cu-Ni
solder or alloy referring to tin-copper with nickel trace (Sn-0,7Cu-0,05Ni)
Note 1 to entry: Some formulations also include other minor additions such as germanium (Ge).
[SOURCE: IEC/TS 62647-22:2013, 3.1.33]
3.1.35
Sn-Pb
solder generally referring to the family of tin-lead alloys at or near the eutectic composition
with or without silver added (Sn-37Pb, Sn-40Pb, or Sn-36Pb-2Ag)
[SOURCE: IEC/TS 62647-22:2013, 3.1.34]
3.1.36
soldered assembly
assembly of two or more basic parts interconnected by a solder alloy
Note 1 to entry: A lead (Pb)-based soldered assembly is one in which the solder alloys are solely lead (Pb)-
based. A lead-free soldered assembly is one in which the solder alloys are solely lead-free.
[SOURCE: IEC/TS 62647-22:2013, 3.1.36]

– 14 – TS 62647-23  IEC:2013(E)
3.1.37
system
one or more units that perform electrical function(s)
[SOURCE: IEC/TS 62647-1:2012, 3.24]
3.1.38
termination
area to be soldered of the piece part termination, castellations, or metallized surface(s) of an
electronic device
3.1.39
ternary alloy
solder alloy containing three component metals
3.1.40
T
g
glass transition temperature of laminate material
3.1.41
high T
g
glass transition temperature of laminate material ≥ 170 °C (338 °F)
3.1.42
tin whisker
spontaneous crystal growth that emanates from a tin (Sn) surface and which may be
cylindrical, kinked, or twisted
Note 1 to entry: Typically tin whiskers have an aspect ratio (length/width) greater than two, with shorter growths
referred to as nodules or odd-shaped eruptions (OSEs).
[SOURCE: IEC/TS 62647-1:2012, 3.26]
3.1.43
under-plating
plating made as a base of a surface over-plating usually required as a barrier to prevent
leeching of two dissimilar metals into one another
3.1.44
WRA
weapons replaceable assembly
black box of electronics, replaced at the flight-line level
3.1.45
XRF
X-ray fluorescence
form of metallurgical analysis that uses X-rays to identify composition of solder alloys and
termination finishes
3.2 Abbreviations
ADHP Aerospace, defence, and high performance
Ag Silver
AHP Aerospace and high performance
Au Gold
Bi Bismuth
TS 62647-23  IEC:2013(E) – 15 –
BGA Ball grid array (related to electronic component package)
C4 Ball Controlled collapse component connection ball
CALCE Center for Advanced Life Cycle Engineering
CBGA Ceramic ball grid array
CCA Circuit card assembly
CM Contract manufacturer
CTE Coefficient of thermal expansion
Cu Copper
D Depot maintenance level
ENIG Electroless nickel immersion gold (related to PCB/PWB surface finish)
EU European Union
Fe Iron
I Intermediate maintenance level
Imm Ag Immersion silver
In Indium
iNEMI International Electronics Manufacturing Initiative
JG-PP Joint Group on Pollution Prevention
GEIA Government Electronics and Information Technology Association
HASL Hot air solder leveling (related to PCB/PWB surface finish)
LFCP Lead-free control plan
LRU Line replaceable unit
MSD Moisture sensitive devices
Ni Nickel
O Organizational maintenance level
OEM Original equipment manufacturer
OSP Organic solderability preservative (related to PCB/PWB surface finish)
Pb Lead
Pb-free Lead-free
PCB Printed circuit board
Pd Palladium
PTH Plated through hole
PWB Printed wiring board
QFN Quad flat no leads (related to electronic component package)
Sn-Ag- Pb-free solder alloy of tin (Sn), silver (Ag), and copper (Cu)
Cu
SAC Pb-free solder alloy of tin (Sn), silver (Ag), and copper (Cu)
SACB Pb-free solder alloy of tin (Sn), silver (Ag), copper (Cu) and bismuth (Bi)
SMT Surface mount technology (related to circuit card assembly technology)
SMTA Surface Mount Technology Association
Sn Tin
Sn-Bi Pb-free solder alloy of tin (Sn) and bismuth (Bi)
Sn-Cu Pb-free solder alloy of tin (Sn) and copper (Cu)
Sn-Cu-Ni Pb-free solder alloy of tin (Sn), copper (Cu), and nickel (Ni)

– 16 – TS 62647-23  IEC:2013(E)
Sn-Pb Tin/lead (normally 63 % tin/37 % lead)
SRA Shop replaceable assembly
SRU Shop replaceable unit
WRA Weapons replaceable assembly
XRF X-ray fluorescence
4 Pb-free concerns
4.1 General
The transition from Sn-Pb to Pb-free rework/repair raises a variety of concerns. IEC/TS
62647-1:2012 identifies five major areas that should be considered. Those areas include
reliability, configuration control, risk management, effects of Sn in the system, and
rework/repair. If the concerns in the first four areas are not properly identified, planned for,
assessed, managed, and documented, rework/repair of those assemblies becomes extremely
difficult. A quality lead-free control plan (LFCP) will identify and mitigate potential concern
areas and provide the technician with clear requirements for rework/repair.
4.2 Reliability
4.2.1 General
The program manager should understand how the transition to Pb-free solder and piece part
termination finishes or mixing Sn-Pb and Pb-free solders may affect the reliability of the
assembly. Additionally, the effects on package types/geometry, piece part termination finish,
and laminate materials and finishes, should be clearly understood when authorizing and
introducing the use of alternate materials.
The reliability of the original solder joint is dependent upon the integrity of the solder in the
joint and the metallurgical interfaces to the terminations and PCB/PWB lands. The solder joint
reliability is influenced by the final solder alloy composition and microstructure, the shape of
the solder surface and the termination-to-solder interfacial strength. The initial composition of
the solder used to form the joint is typically modified to some extent during the soldering
process as the pad metallization and finish are dissolved into the solder joint. The amount of
dissolved piece part and pad metal typically does not significantly alter the initial alloy
composition. The exceptions to this rule are ball grid array (BGA) type devices where the ball
solder volume represents a significant amount of the total solder volume, and pad interface
finish elements that have a tendency to segregate to either the piece part or the PCB/PWB
pad interfaces or grain boundaries such as gold (Au) and bismuth (Bi) alloys contaminated
with trace amounts of lead (Pb).
4.2.2 Mixed metallurgy reliability
4.2.2.1 General
In a reworked/repaired solder joint, metallurgy mixing is a major reliability concern to
electronics equipment suppliers and users. As Sn-Pb BGA ball metallurgy and Sn-Pb finished
piece parts are being quickly replaced by Pb-free alternatives, Pb-free solders may be either
intentionally or unintentionally mixed with Sn-Pb solder and/or Pb-bearing finishes throughout
their service life and during repair activity. Annex A lists a number of the termination finishes
that potentially could be encountered. Annex B provides a summary of the tin whisker
propensity for the various elemental additions to Sn.
4.2.2.2 Pb-free terminations in Sn-Pb joints
One result of the WEEE/RoHS directives and the responding piece part fabricator initiative is
the introduction of piece parts with Pb-free surface finish terminations into existing traditional
Sn-Pb soldering processes. The variety and compositions of the Pb-free surface finishes
being delivered into the electronics industry is extensive. Many of these piece parts materials

TS 62647-23  IEC:2013(E) – 17 –
will find their way into the inventory of aerospace and defence assembly processes under
government acquisition reform initiatives. Electronics assembly design teams should be
knowledgeable on the potential imp
...