IEC PAS 62647-3:2011

IEC/PAS 62647-3
®

Edition 1.0 2011-07
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
colour
inside

Process management for avionics – Aerospace and defence electronic systems
containing lead-free solder –
Part 3: Performance testing for systems containing lead-free solder and finishes



IEC/PAS 62647-3:2011(E)

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IEC/PAS 62647-3
®

Edition 1.0 2011-07
PUBLICLY AVAILABLE
SPECIFICATION

PRE-STANDARD
colour
inside

Process management for avionics – Aerospace and defence electronic systems
containing lead-free solder –
Part 3: Performance testing for systems containing lead-free solder and finishes


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
W
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-88912-599-9
® Registered trademark of the International Electrotechnical Commission

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– 2 – PAS 62647-3 © IEC:2011(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 9
3 Terms and Definitions . 10
4 Default Test Methods . 11
4.1 Test Vehicles . 11
4.1.1 Test Vehicle type . 11
4.1.2 Sample size . 12
4.2 Pre-Conditioning by Thermal Aging Method . 12
4.2.1 Thermal Aging Acceleration Model . 12
4.2.2 Default Test Parameters . 13
4.3 Default Temperature Cycle Test Method . 13
4.3.1 Test Parameters . 13
4.3.2 Test Duration . 13
4.3.3 Failure Determination and Analysis . 13
4.3.4 Acceleration Model . 14
4.4 Vibration Test . 15
4.5 Mechanical Shock . 15
4.6 Combined Environments. 16
5 Protocol to Design and Conduct Performance Tests . 16
5.1 Test Vehicles . 16
5.2 Temperature Cycle Test Protocol . 16
5.2.1 Measure the recovery time . 17
5.2.2 Determine the high-temperature dwell times and temperatures . 18
5.2.3 Select other test parameters as appropriate for the application . 19
5.2.4 Conduct tests . 19
5.2.5 Determine the temperature versus cycles-to-failure relationship . 19
5.2.6 Estimate the cycles to failure . 20
5.3 Vibration Test . 20
5.4 Mechanical Shock . 21
5.5 Combined Environments Test Protocol . 21
5.5.1 Combined Environment Relation . 22
5.5.2 Additional Insight: NASA-DoD Lead-free (Pb-free) Project . 23
5.5.3 Additional Insight: Concept of Life Cycle per MIL-STD-810 . 23
5.6 Failure Determination and Analysis . 24
6 Final Remarks . 24
Annex A (informative) Test Sample Size . 25
Annex B (informative) Material Properties of Lead-free (Pb-free) Solder Materials . 27
Annex C (informative) NASA-DoD Lead-free (Pb-free) Electronics Project Test
Information (from the NASA-DoD Lead-free (Pb-free) Project Joint Test Protocol, 19
September 2007) . 30

Figure 1 – Notional method for determining the recovery time for a given solder alloy,

or combination of alloys. . 18

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PAS 62647-3 © IEC:2011(E) – 3 –
Figure 2 – Notional method for determining the relationship between high temperature
dwell time, t , and recovery time, t . (This example assumes an idealized system but
hd r
the slope may differ depending on material, temperature range, and dwell.) . 19
Figure 3 – Notional method for determining the relationship between cycles to failure . 20
Figure C.1 – Vibration Spectrum . 31
Figure C.2 – Vibration Test Fixture (from JCAA/JGPP Lead-free (Pb-free) Solder
Project Team*) . 33
Figure C.3 – Vibration Table showing Y-axis (from JCAA/JGPP Lead-free (Pb-free)
Solder Project Team) . 34
Figure C.4 – Mechanical Shock Response Spectrum . 35
Figure C.5 – Mechanical Shock Test Set-Up (from JCAA/JGPP Lead-free (Pb-free)
Solder Project Team) . 37

Table B.1 – Test and Acceleration Model Parameters . 27
Table C.1 – Vibration Profile . 32
Table C.2 – Vibration Test Methodology . 33
Table C.3 – Mechanical Shock Test Methodology – Test Procedure. 37
Table C.4 – Combined Environments Test Methodology . 39

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– 4 – PAS 62647-3 © IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC
SYSTEMS CONTAINING LEAD-FREE SOLDER –

Part 3: Performance testing for systems containing
lead-free solder and finishes


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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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 62647-3 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
107/124/PAS 107/135A/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.

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PAS 62647-3 © IEC:2011(E) – 5 –
This PAS is based on GEIA-STD-0005-3 and is published as a double logo PAS. GEIA,
Government Electronics and Information Technology Association, has been transformed into
TechAmerica Association.
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.

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.

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– 6 – PAS 62647-3 © IEC:2011(E)
INTRODUCTION
The implementation of Lead-free (Pb-free) interconnection technology into electronics has
resulted in a variety of reactions by designers, manufacturers, and users. While the prime
motivation for Lead-free (Pb-free) technology was to address the social concern of improving
the environment by limiting the amount of toxic and dangerous substances used in products,
the ramifications of this initiative have provided a state of uncertainty regarding the
performance – in this context, defined as operation and reliability, i.e. the expected life cycle
of a product – of aerospace and defence systems. For over fifty years, Tin-Lead solder was
the benchmark for electronics assembly and generations of research baselined its
performance under a variety of operating conditions including the harsh settings of aerospace
and defence equipment. However, with the integration of Lead-free (Pb-free) technology,
aerospace and defence companies are faced with questions as to whether these new
materials will provide, as a minimum, the same degree of confidence during the life cycle of
critical systems and products.
In evaluating performance, two approaches are used: analysis/modeling and test. This
document addresses the latter, providing guidance and direction in the development and
execution of performance tests for Lead-free (Pb-free) electronic interconnections. The user
of this document needs to be aware of the following: This document does not give answers as
to how to perform a specific test. Products and systems applications vary immensely, so
designers need to understand use conditions and the entire life cycle. Once this is
understood, then this document can be used to give designers an understanding of how to
develop a suitable test, e.g., ascertain the type of platform in which a product will be used,
comprehending all the environmental effects on the platform, and learning why material
characterization is key to deciding upon test parameters, etc.
Sound engineering knowledge and judgment will be required for the successful use of this
document.
The global transition to Lead-free (Pb-free) electronics has a significant impact on the
electronics industry; it is especially disruptive to aerospace and other industries that produce
electronic equipment for high performance applications. These applications, hereinafter
described as AHP (Aerospace and High Performance), are characterized by severe or harsh
operating environments, long service lifetimes, and high consequences of failure. In many
cases, AHP electronics must be repairable at the soldered assembly level. Typically, AHP
industry production volumes may be low and, due to low market share, may not be able to
resist the change to Lead-free (Pb-free). Furthermore, the reliability tests conducted by
suppliers of solder materials, components, and sub-assemblies cannot be assumed to assure
reliability in AHP applications. This document provides guidance (and in some cases
direction) to designers, manufacturers, and maintainers of AHP electronics in assessing
performance of Lead-free (Pb-free) interconnections.
Over the past several decades, electronics manufacturers have developed methods to
conduct and interpret results from reliability tests for lead-bearing solder alloys. Since these
alloys have been used almost universally in all segments of the electronics industry, and
since a large body of data, knowledge, and experience has been assembled, the reliability
tests for Pb-bearing solder alloys are well-understood and widely accepted.
When it became apparent that the use of Pb-bearing alloys would decline rapidly, programs
were implemented to evaluate the reliability of the Lead-free (Pb-free) replacement alloys.
Those programs have generated a considerable database. To date, however, there is no
reliability test method that is widely accepted in the AHP industries. Reasons for this include:
a) No single Lead-free (Pb-free) solder alloy has emerged as a replacement for lead-bearing
alloys; instead, a number of alloys are being used in various segments of the electronics
industry.
b) The physical, chemical, and metallurgical properties of the various Lead-free (Pb-free)
replacement alloys vary significantly.

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PAS 62647-3 © IEC:2011(E) – 7 –
c) Due to the many sources of solder alloys used in electronic component termination
materials or finishes, assembly processes, and repair processes, the potential number of
combinations of alloy compositions is nearly unlimited. It is an enormous task to collect
data for all these combinations.
d) The test methods developed by other segments (References [1] and [2]) are directed
toward shorter service lives and more benign environments. Also, there is still a question
of suitable dwell times and acceleration factors. (However, the intent of this document is to
provide a mean of coordinating the information from References [1] and [2] into a basic
approach for AHP suppliers.)
e) The data from reliability tests that have been conducted are subject to a variety of
interpretations.
In view of the above facts, it would be desirable for high-reliability users of Lead-free (Pb-
free) solder alloys to wait until a larger body of data has been collected, and methods for
conducting reliability tests and interpreting the results have gained wide acceptance for high-
reliability products. In the long run, this will indeed occur. However, the transition to Lead-free
(Pb-free) solder is well under way and there is an urgent need for a reliability test method, or
set of methods, based on industry consensus. While acknowledging the uncertainties
mentioned above, this document provides necessary information for designing and conducting
performance tests for aerospace products. In addition, when developing test approaches, the
material in question needs to be suitably characterized. Such material properties as ultimate
tensile strength, yield strength, Poisson’s ratio, creep rate, and stress relaxation have been
shown to be key attributes in evaluating fatigue characteristics of Lead-free (Pb-free) solders.
Because of the dynamic nature of the transition to Lead-free (Pb-free) electronics, this and
other similar documents must be considered provisional. While this document is based on the
best information and expertise available, it must be updated as future knowledge and data are
obtained.
The intent of the document is not to prescribe a certain method, but to aid avionics/ defence
suppliers in satisfying the reliability and/or performance requirements of IEC/PAS 62647-1
(GEIA-STD-0005-1) [5] as well as support the expectations in GEIA-HB-0005-1 [6].
Accordingly, it includes
– a default method for those companies that require a pre-defined approach and
– a protocol for those companies that wish to develop their own test methods.
Also, this PAS will focus on testing the Lead-free (Pb-free) interconnections, i.e., the “system”
comprised of the solder alloy as well as the component and board finishes. While the bulk of
this introduction has discussed reliability testing of Lead-free (Pb-free) assemblies, this
document will direct attention to test guidelines to evaluate the performance of the Lead-free
(Pb-free) interconnection. The guidelines presented in this document do not suggest methods
for reliability testing of product. That is left to each individual user. The document provides
insight as to what approaches should be used as part of a performance test when Lead-free
(Pb-free) interconnection is of prime interest.
In summary, the purpose of this PAS is threefold:
1. It is meant to provide a means to acquire sound, accurate data regarding the performance
of a Lead-free (Pb-free) interconnection under harsh conditions (aerospace, military,
medical, etc.,)
2. It is usable for further design assessment and operation of a product, and
3. It is usable as part of a process development study.
Finally, any portion of this document may be used to develop a Lead-free (Pb-free) assembly
test program, i.e., this PAS is tailorable and provides room for flexibility. For those situations
in which results are used for reliability, verification, or qualification, it is strongly
recommended that stakeholder concurrence be sought and documented so that expectations
are understood and addressed.

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– 8 – PAS 62647-3 © IEC:2011(E)
PROCESS MANAGEMENT FOR AVIONICS –
AEROSPACE AND DEFENCE ELECTRONIC
SYSTEMS CONTAINING LEAD-FREE SOLDER –

Part 3: Performance testing for systems containing
lead-free solder and finishes



1 Scope
This PAS defines for circuit card assemblies (CCA)
– a default method for those companies that require a pre-defined approach and
– a protocol for those companies that wish to develop their own test methods.
The default method (Section 4 of the PAS) is intended for use by electronic equipment
manufacturers, repair facilities, or programs that, for a variety of reasons, may be unable to
develop methods specific to their own products and applications. It is to be used when little or
no other information is available to define, conduct, and interpret results from reliability,
qualification, or other tests for electronic equipment containing Lead-free (Pb-free) solder.
The default method is intended to be conservative, i.e., it is biased toward minimizing the risk
to users of AHP electronic equipment.
The protocol (Section 5 of the PAS) is intended for use by manufacturers or repair facilities
that have the necessary resources to design and conduct reliability, qualification, or process
development tests that are specific to their products, their operating conditions, and their
applications. Users of the protocol will have the necessary knowledge, experience, and data
to customize their own methods for designing, conducting, and interpreting results from the
data. Key to developing a protocol is a firm understanding of all material properties for the
Lead-free (Pb-free) material in question as well as knowledge of package- and board-level
attributes as described in Section 4.1.1. As an example, research has shown that the
mechanisms for creep can be different between Tin-Lead and Tin-Silver-Copper (SAC)
solders. Understanding these mechanisms is key to determining critical test parameters such
as dwell time for thermal cycling. The protocol portion of this document provides guidance on
performing sufficient characterization of new materials in order to accurately define test
parameters.
Use of the protocol is encouraged, since it is likely to yield more accurate results, and to be
less expensive than the default method. Reference [7] provides a comprehensive overview of
those technical considerations necessary in implementing a test protocol.
This PAS addresses the evaluation of failure mechanisms, thru performance testing, expected
in electronic products containing Lead-free (Pb-free) solder. One failure mode, fatigue-failure
thru the solder-joint, is considered a primary failure mode in AHP electronics and can be
understood in terms of physics of failure and life-projections. Understanding all of the
potential failure modes caused by Lead-free (Pb-free) solder of AHP electronics is a critical
element in defining early field-failures/reliability issues. Grouping of different failure modes
may result in incorrect and/or misleading test conclusions. Failure analysis efforts should be
conducted to insure that individual failure modes are identified, thus enabling the correct
application of reliability assessments and life-projection efforts.
When properly used, the methods or protocol defined in this PAS may be used along with the
processes documented in compliance to Reference [3], to satisfy, at least in part, the
reliability requirements of References [3] and [4].

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PAS 62647-3 © IEC:2011(E) – 9 –
This PAS may be used for products in all stages of the transition to Lead-free (Pb-free)
solder, including:
• Products that have been designed and qualified with traditional Tin-Lead electronic
components, materials, and assembly processes, and are being re-qualified with use of
Lead-free (Pb-free) components
• Products with Tin-Lead designs transitioning to Lead-free (Pb-free) solder; and
• Products newly-designed with Lead-free (Pb-free) solder.
For programs that were designed with Tin-Lead solder, and are currently not using any Lead-
free (Pb-free) solder, the traditional methods may be used. It is important, however, for those
programs to have processes in place to maintain the Tin-Lead configuration including those
outsourced or manufactured by subcontractors.
With respect to products as mentioned above, the methods presented in this document are
intended to be applied at the level of assembly at which soldering occurs, i.e., circuit-card
assembly level.
2 Normative references
The following referenced documents are indispensable for the application 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.
1) IPC-9701A, “Performance Test Methods and Qualification Requirements for Surface
Mount Solder Attachments”, IPC, February 2006
2) IPC/JEDEC-9703, “Testing Methodologies for Solder Joint Reliability in Shock
Conditions”, DATE TBD
3) IPC-SM-785, “Guidelines for Accelerated Reliability Testing of Surface Mount Solder
Attachments”, IPC, November 1992
4) JESD22-B110A, “JEDEC Standard Subassembly Mechanical Shock”, November 2004
5) IEC/PAS 62647-1, Program management for Avionics – Aerospace and defence electronic
systems containing lead-free solder – Part 1: Lead-free management
6) GEIA-STD-0005-1, Performance Standard for Aerospace and High Performance
Electronic Systems Containing Lead-free (Pb-free) Solder. Government Engineering and
Information Technology Association, 2006
7) IEC/PAS 62647-2, Process management for Avionics – Aerospace and defence electronic
systems containing lead-free solder – Part 2: Mitigation of the deleterious effects of tin
8) GEIA-STD-0005-2, Standard for Mitigating the Effects of Tin whiskers in Aerospace and
High Performance Electronic Systems. Government Engineering and Information
Technology Association, 2006
9) IEC/PAS 62647-21, Aerospace and defence electronic systems containing lead-free solder
– Part 2
...