IEC PAS 62647-22:2011
(Main)Process management for avionics - Aerospace and defence electronic systems containing lead-free solder - Part 22: Technical guidelines
Process management for avionics - Aerospace and defence electronic systems containing lead-free solder - Part 22: Technical guidelines
IEC/PAS 62647-22:2011(E) is intended for use as technical guidance by Aerospace system Suppliers, e.g., Aerospace system Original Equipment Manufacturers and Aerospace system maintenance facilities, in developing and implementing designs and processes to ensure the continued performance, quality, reliability, safety, airworthiness, configuration control, affordability, maintainability, and supportability of high performance aerospace systems (subsequently referred to as AHP) both during and after the transition to Pb-Free electronics.
General Information
Relations
Standards Content (Sample)
IEC/PAS 62647-22
®
Edition 1.0 2011-07
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Process management for avionics – Aerospace and defence electronic systems
containing lead-free solder –
Part 22: Technical guidelines
IEC/PAS 62647-22:2011(E)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2011 IEC, Geneva, Switzerland
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
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: 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.
Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
---------------------- Page: 2 ----------------------
IEC/PAS 62647-22
®
Edition 1.0 2011-07
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Process management for avionics – Aerospace and defence electronic systems
containing lead-free solder –
Part 22: Technical guidelines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-88912-601-9
® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – PAS 62647-22 IEC:2011(E)
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 11
4 Approach . 17
5 General Pb-Free Solder Alloy Behavior . 18
5.1 Elevated Temperature . 19
5.2 Low Temperatures . 19
5.3 Temperature Cycling . 21
5.3.1 Solder Thermal Cycling Failure Mode: . 22
5.3.2 Stress Relaxation Considerations: . 22
5.3.3 Ramp Rate: . 22
5.3.4 Dwell Time at Elevated Temperature: . 23
5.3.5 Dwell Time at Low Temperature: . 23
5.4 Rapid Mechanical Loading (Vibration/Shock) . 23
6 System Level Service Environment . 23
6.1 Service Environment . 24
6.2 Electronics/Electrical Equipment Thermal Environments . 24
6.2.1 Electronics/Electrical Equipment Steady Temperatures . 24
6.2.2 Electronics/Electrical Equipment Temperature Cycling . 24
6.3 Vibration and Shock . 24
6.4 Humidity . 25
6.5 Other environments: Salt Spray, Fungus, Cooling Air Quality, and Fluid
Compatibility . 25
6.6 Other Special Requirements . 25
7 High Performance Electronics Testing . 25
8 Solder Joint Reliability Considerations . 26
8.1 Mixing of Solder Alloys and Finishes . 27
8.2 Pb-free Terminations in Tin-Lead Joints . 27
8.2.1 Ball Grid Array Pb-free Terminations in Tin-Lead Joints . 28
8.2.2 Flat pack and chip device Pb-free Terminations in Tin-Lead Joints . 30
8.3 Tin-Lead Terminations in Pb-free joints . 30
8.3.1 Ball Grid Array Tin-Lead Terminations in Lead-free Joints . 31
8.3.2 Flat pack and chip device Tin-Lead Terminations in Lead-free Joints . 31
8.4 Bismuth Effects . 31
8.5 JCAA/JGPP Testing of Mixed Alloy Combinations . 32
8.5.1 Vibration . 32
8.5.2 Thermal Shock Testing . 32
8.5.3 Combined Environments . 33
8.6 Pb-Free Solder and Mixed Metallurgy Modeling . 33
9 Piece-parts . 38
9.1 Materials . 38
9.2 Temperature Rating. 38
9.3 Special considerations . 38
9.4 Plastic Encapsulated Microcircuit (PEM) Moisture Sensitivity Level (MSL) . 38
---------------------- Page: 4 ----------------------
PAS 62647-22 IEC:2011(E) – 3 –
9.5 Terminal Finish . 38
9.6 Assembly stresses . 40
9.7 Hot Solder Dipping . 40
10 Printed Circuit Boards . 40
10.1 Plated Through Holes . 41
10.2 Copper Dissolution . 41
10.3 PCB Laminate Materials . 42
10.3.1 Coefficient of Thermal Expansion . 43
10.4 Surface Finish . 43
10.5 Pb-Free PCB Qualification. 45
10.6 PCB artwork and Design Considerations for Pb-Free solder applications . 45
11 Printed Circuit Board Assembly . 45
11.1 PCB Process Indicator Coupons . 45
11.2 Solder Inspection Criterion . 45
11.3 Fluxes, Residues, Cleaning and SIR issues . 46
12 Module Assembly Considerations . 54
12.1 Connectors and Sockets . 54
12.2 Heatsinks/Modules . 54
12.3 Conformal Coating . 54
13 Manufacturing Resources . 55
14 Aerospace Wiring/Cabling Considerations . 55
14.1 Insulation Temperature Rating. 55
14.2 Cable Connectors . 55
14.3 Wire Terminals . 56
14.4 Splices . 56
14.5 Sleeving . 56
15 Rework/Repair . 56
15.1 Piece Part Rework . 58
15.1.1 Area Array Rework . 58
15.1.2 Surface Mount Capacitor/Resistor Rework . 58
15.1.3 Through-Hole Piece Part Rework . 58
15.2 Depot Level Repair . 59
15.3 Mixed Solder Rework Temperature Profiles . 59
15.4 Solder Fluxes . 59
15.5 Rework / Repair Cleaning Process . 60
15.6 Inspection requirements . 60
16 Generic Life Testing . 60
16.1 Thermal Cycling, Vibration, and Shock Testing . 60
16.2 Other Environments. 61
16.2.1 Salt Fog . 61
16.2.2 Cooling Air Quality . 61
16.2.3 Fluid Compatibility . 61
16.2.4 Generic Humidity . 61
17 Similarity Analysis . 61
Annex A Equipment Service Environmental Definition . 63
Bibliography . 64
---------------------- Page: 5 ----------------------
– 4 – PAS 62647-22 IEC:2011(E)
Table 1 – Review Of Piece-Part Surface Finish And Potential Concerns . 34
Table 2 – Elements Promoting and Supressing Tin Whiskers . 35
Table 3 – Elements Promoting and Supressing Tin pest . 36
Table 4 – Piece-part Lead/Terminal and BGA Ball Metallization Tin Whisker and Tin
Pest Propensity . 39
Table 5 – PCB Metallization Tin Whisker and Tin Pest Propensity . 44
Table 6 – Piece-part Terminal and BGA Ball Metallization Solder Process Compatibility
Risk (See Note 1) . 47
Table 7 – PCB Finish Solder Process Compatibility Risk (1) . 50
Table 8 – Piece-part Terminal and BGA Ball Metallization Reliability Risk (See Note 1) . 51
Table 9 – PCB Metallization Reliability Risk (See Note 1) . 53
Table 10 – Relative Rigidity of IPC-CC-830 Conformal Coating Categories . 55
Table 11 – Process temperatures of mixed alloys . 60
---------------------- Page: 6 ----------------------
PAS 62647-22 IEC:2011(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC SYSTEMS
CONTAINING LEAD-FREE SOLDER –
Part 22: Technical guidelines
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.
A PAS is a technical specification not fulfilling the requirements for a standard, but made
available to the public.
IEC PAS 62647-22 has been processed by IEC technical committee 107: Process
management for avionics.
The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft PAS Report on voting
107/131/PAS 107/139A/RVD
Following publication of this PAS, which is a pre-standard publication, the technical committee
or subcommittee concerned may transform it into an International Standard.
---------------------- Page: 7 ----------------------
– 6 – PAS 62647-22 IEC:2011(E)
This PAS shall remain valid for an initial maximum period of 3 years starting from the
publication date. The validity may be extended for a single 3-year period, following which it
shall be revised to become another type of normative document, or shall be withdrawn.
This PAS is based on GEIA-HB-0005-2 and is published as a double logo PAS. GEIA,
Government Electronics and Information Technology Association, has been transformed into
TechAmerica Association.
---------------------- Page: 8 ----------------------
PAS 62647-22 IEC:2011(E) – 7 –
INTRODUCTION
0.1 General
This PAS is intended for use by Aerospace and High Performance (AHP) electronics system
Customer, i.e., aerospace and defence vehicle integrators, operators, and regulatory
organizations, and their Suppliers, i.e., system Original Equipment Manufacturers (OEMs) and
system maintenance facilities as they incorporate Lead-free (Pb-free) solder or Pb-free piece-
parts and board finishes.
This PAS is intended to work in concert with IEC/PAS 62647-1 (GEIA-STD-0005-1), IEC/PAS
62647-21 (GEIA-HB-0005-1), and IEC/PAS 62647-2 (GEIA-STD-0005-2). Part way through
this documents creation, it was evident that three additional documents were needed. As a
result, IEC/PAS 62647-3 (GEIA-STD-0005-3), IEC/PAS 62647-23 (GEIA-HB-0005-3) and the
reliability assessment document GEIA-HB-0005-4 have been added to address testing,
rework, and reliability prediction respectively.
This PAS may be referenced in proposals, requests for proposals, work statements, contracts,
and other aerospace and high performance industry documents.
0.2 Transition to Pb-free
The global transition to Pb-Free electronics impacts the aerospace and other industries
having high reliability applications in various ways. In addition to the perceived need to
replace the Tin-Lead solders used as an interconnect medium in electronic and electrical
systems, the following variations to established practice will need to be considered:
• components and printed circuit boards will need to be able to withstand higher
manufacturing process temperatures;
• printed circuit boards will need to have robust solderable Pb-Free surface finishes;
• manufacturing and inspection techniques are needed that yield repeatable reliability
characteristics;
• at least initially, Pb-free alloys used within the equipment should be restricted to those
that are compatible with Tin-Lead soldering systems;
• a maintenance strategy should be developed that will facilitate the support repair of new
and existing equipment throughout a 20+ year life.
This PAS will establish guidelines for the use of Pb-Free solder and mixed Tin-Lead/Lead-free
alloy systems while maintaining the high reliability standards required for aerospace
electronic and electrical systems. Currently the largest volume of Lead (Pb) in many of these
electronic systems is in the Tin-Lead eutectic (Sn-37Pb) and near eutectic alloys (Sn-36Pb-
2Ag, Sn-40Pb) used in printed circuit board assemblies, wiring harnesses and electrical
systems. High-Lead solder alloys are not specifically addressed in this PAS; however, many
of the methodologies outlined herein are applicable for their evaluation.
A good deal of the information desired for inclusion in this technical guidelines document does
not exist. A large number of Pb-Free investigative studies for aerospace and high reliability
electronic and electrical systems are either in progress or in the initiation stage. The long
durations associated with reliability testing necessitates a phased release of information. The
information contained herein reflects the best information available at the time of document
issuance. It is not the goal of this PAS to provide technical guidance without an understanding
of why that guidance has technical validity or without concurrence of the technical community
in cases where sufficient data is lacking or conflicting. The PAS will be updated as new data
becomes available.
Further complicating matters is the fact that no single alloy across the supply base will be
replacing the heritage Tin-Lead eutectic alloy and that it is not likely that qualification of one
alloy covers qualification for all other alloys. Given the usual requirement for long, high
---------------------- Page: 9 ----------------------
– 8 – PAS 62647-22 IEC:2011(E)
performance electronic service lives, any Pb-Free alloy must have predictable performance
when mixed with heritage Tin-Lead alloys. Pb-Free alloys containing elements such as
Bismuth (Bi) or Indium (In) that can form alloys having melting points within the equipments
operating temperature range must be considered very carefully before use. Although Pb-Free
solder alloys are still undergoing some adjustments, it appears that the Sn-Ag-Cu family of
alloys will be used for surface mount assembly and either Sn-Ag-Cu, Sn-Cu or Sn-Cu-Ni (Sn-
Cu stabilized with Nickel) alloys will be dominant in wave solder applications. In addition,
some applications are using the Sn-Ag alloy family [1] [2] [3].
The majority of the Pb-Free solder alloys being considered have higher melting temperatures
than Tin-Lead eutectic solder. In order to make use of the Pb-Free solders, changes to the
molding compound, die attach and printed circuit board insulation systems are being
introduced to accommodate the 30 °C to 40 °C higher (54 °F to 72 °F higher) processing
temperature. Thus, not only is the Pb-Free transition changing the solder alloy, but a
significant portion of the electronic packaging materials are changing as well. The higher
melting point, greater creep resistance and higher strength of the Pb-Free alloys have driven
a significant amount of study into the thermal cycling and mechanical vibration/shock
assessments of these new alloys.
The consumer electronics industry has invested considerable resources to ensure that Pb-
Free solder will perform adequately for their products. Creep resistance of Pb-free alloys can
vary considerably from heritage Tin-Lead solders. The creep/stress relaxation performance of
the solder depends on the stress level, temperature and time for a specific solder material
and joint composition. Therefore, one needs to establish what the acceleration factor is
between a particular test condition and application. The interpretation of the results of a head-
to-head testing needs to be assessed in terms of the anticipated service conditions with
respect to these acceleration factors. Thermal preconditioning prior to thermal cycling should
be considered in the Pb-free solder assessment plan particularly as it relates to changes in
solder microstructure. Modeling/Analysis is needed to properly compare the Tin-Lead and Pb-
Free alloy performance and correct for the stress relaxation differences obtained for the
various piece-parts and thermal cycling conditions.
While there is much data on near eutectic SAC (e.g., 305 and 405) Pb-Free thermal cycling,
there is less information regarding Pb-Free vibration and shock performance. Fortunately, the
vibration and shock performance data can be obtained relatively quickly. During
vibration/shock testing, the near eutectic SAC Pb-Free solder behaves more rigidly than the
Sn-Pb solder transferring greater loads to the interfaces between the solder alloy and the
substrate interfaces. The increased amount of Tin in Pb-Free alloys increases the
intermetallic thickness when Copper substrates are used. In addition, when Nickel or
electroless Nickel (Nickel – Phosphorous) substrates are used, the increased Copper in the
SAC alloy can result in the formation of intermetallics on the nickel interface, which are less
robust than Sn-Cu or Sn-Ni intermetallics that are typical of Tin-Lead solder joints.
Mechanical test results to-date suggest that a robust assessment of Pb-Free alloy assembly
in vibration and shock environments will need to include thermal aging for interface and
microstructural stabilization prior to any dynamic mechanical testing. Alloys other than SAC
should be assessed to determine their vibration and shock performance characteristics.
---------------------- Page: 10 ----------------------
PAS 62647-22 IEC:2011(E) – 9 –
PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC SYSTEMS
CONTAINING LEAD-FREE SOLDER –
Part 22: Technical guidelines
1 Scope
This PAS is intended for use as technical guidance by Aerospace system Suppliers, e.g.,
Aerospace system Original Equipment Manufacturers (OEMs) and Aerospace system
maintenance facilities, in developing and implementing designs and processes to ensure the
continued performance, quality, reliability, safety, airworthiness, configuration control,
affordability, maintainability, and supportability of high performance aerospace systems
(subsequently referred to as AHP) both during and after the transition to Pb-Free electronics.
This PAS is intended for application to aerospace products; however, it may also be applied,
at the discretion of the user, to other products with similar characteristics, e.g., low-volume,
rugged use environments, high reliability, long lifetime, and reparability. If other industries
wish to use this PAS, they may substitute the name of their industry for the word “Aerospace”
in this PAS.
The guidelines may be used by the OEMs and maintenance facilities to implement the
methodologies they use to ensure the performance, reliability, airworthiness, safety, and
certifiability of their products, in accordance with IEC/PAS 62646-1 (GEIA-STD-0005-1),
“Performance Standard for High Performance Electronic Systems Containing Pb-Free Solder.”
This PAS also contains lessons learned from previous experience with Pb-Free aerospace
electronic systems. The lessons learned give specific references to solder alloys and other
materials, and their expected applicability to various operating environmental conditions. The
lessons learned are intended for guidance only; they are not guarantees of success in any
given application.
2 Normative references
The following referenced docu
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.