IEC PAS 62647-22:2011

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)
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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
– 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

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

– 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

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
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6) All users should ensure that they have the latest edition of this publication.
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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 62647-22 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.

– 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.
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

– 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.

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 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.
IEC/PAS 62647-1, Aerospace and defence electronics systems containing lead free solder –
Part 1: Lead free management
IEC/PAS 62647-2, Aerospace and defence electronics systems containing lead free solder –
Part 2: Mitigation of the deleterious effects of tin
IEC/PAS 62647-3, Aerospace and defence electronics systems containing lead free solder –
Part 3: Performance testing for systems containing lead-free solder
IEC/PAS 62647-21, Aerospace and defence electronic systems containing lead free-solder –
Part 21: Program management – Systems engineering guidelines for managing the transition
to lead-free electronics
– 10 – PAS 62647-22  IEC:2011(E)
IEC/PAS 62647-23, 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
GEIA-STD-0005-1, Performance standard for aerospace and high performance electronic
systems containing lead-free solder
GEIA-STD-0005-2, Standard for mitigating the effects of tin in aerospace and high
performance electronic systems
GEIA-HB-0005-1, Program management / Systems engineering guidelines for managing the
transition to lead-free electronics
GEIA-HB-0005-3, Rework and repair handbook to address the implications of lead-free
electronics and mixed assemblies in aerospace and high performance electronic systems
GEIA-HB-0005-3, “Aerospace and defence electronics systems containing lead free solder –
Part 23: Rework and repair handbook to address the implications of lead-free electronics and
mixed assemblies
GEIA-HB-0005-4, Guidelines for Performing Reliability Assessment for Lead Free Assemblies
used in Aerospace and High-Performance Electronic Applications
GEIA-STD-0006, Requirements for Using Solder Dip to Replace the Finish on Electronic
Components
ARINC Project Paper 671: Guidelines for Lead-free Soldering, Repair, and Rework, March 16,
2006.
ASTM B117-3 Standard Practice for Operating Salt Spray (Fog) Apparatus, October 2003
ASTM G85 Standard Practice for Modified Salt Spray (Fog) Testing, Annex A4 Salt/SO2
Spray (Fog) Testing 2002.
MIL-I-46058C Insulating Compound, Electrical (for coating printed circuit assemblies),
Inactive for new design. July (1982)
IPC/JEDEC JP002, Current Tin Whiskers Theory and Mitigation Practices Guideline, March
2006.
IPC/JEDEC J-STD-001D, Requirements for Soldered Electrical and Electronic Assemblies,
Feb. 2005.
IPC/JEDEC J-STD-002B, Solderability Tests for Component Leads, Terminations, Lugs,
Terminals and Wires, February 2003
IPC/JEDEC J-STD-006B, Requirements for Electronic Grade Solder Alloys and Fluxed and
Not Fluxed Solders for Electronic Soldering Applications, January 2006.
IPC/JEDEC J-STD-020C, Moisture/Reflow Sensitivity Classification for Non-hermetic Solid
State Surface Mount Devices, July 2004.
IPC/JEDEC J-STD-033B, Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive
Surface Mount Devices, October 2005

PAS 62647-22  IEC:2011(E) – 11 –
IPC/JEDEC J-STD-609, Marking of Symbols and Labels of PCB Assemblies and Piece Parts
to Identify Lead (Pb) and other Materials
IPC-A-610, Acceptability of Electronic Assemblies, Revision D, February (2005)
IPC-CC-830, Qualification and Performance of Electrical Insulating Compound for Printed
Wiring Assemblies, Revision B, August (2002)
IPC-TM-650, Test Methods Manual Method 2.6.25 Conductive Anodic Filament (CAF)
Resistance Test: X-Y Axis November 2003
IPC-1066 Marking, Symbols and Labels for Identification of Lead-Free and Other Reportable
Materials in Lead-Free Assemblies, Components and Devices, January 2005
IPC-1752 Materials Declaration Management, February 2006
IPC-2221A, Generic Standard on Printed Board Design, May 2003.
IPC-4552, Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed
Circuit Boards, October 2002.
IPC-4553, Specification for Immersion Silver Plating for Printed Circuit Boards, June 2005.
IPC-4554, Specification for Immersion Tin Plating for Printed Circuit Boards
IPC-7095A, Design and Assembly Process Implementation for BGAs, October, 2004.
IPC-9701 Performance Test Methods and Qualification Requirements for Surface Mount
Solder Attachments, January 2002, and Lead-Free Appendix B
JESD97 Marking, Symbols, and Labels for Identification of Lead (Pb) Free Assemblies,
Components, and Devices, May 2004
3 Terms and definitions
For purposes of this document, the following terms and definitions apply:
3.1
alloy composition
all alloy compositions are stated as weight percent. For instance 63Sn-37Pb corresponds to a
mixture of 63 % by weight of Tin(Sn) and 37 % by weight of Lead(Pb)
3.2
alloy 42
refers to a nickel-iron controlled-expansion alloy containing 42 % nickel that is often used as a
lead-frame material in electronic packages
3.3
Ag, Au, Bi, Cu, Ge, In, Ni, Pb, Sb, and Sn
refer to the elements Silver, Gold, Bismuth, Copper, Germanium, Indium, Nickel, Lead,
Antimony, and Tin, respectively
3.4
AHP
Aerospace, High Performance Systems

– 12 – PAS 62647-22  IEC:2011(E)
3.5
assemblies
are electronic items that require electrical attachments, including soldering of wires or
component terminations; examples include circuit cards and wire harnesses
3.6
AR
acrylic resin conformal coating
3.7
CAF
refers to Conductive Anodic Filaments that form in printed wiring boards. See IPC-TM-650
Method 2.6.25
3.8
CALCE
the University of Maryland Center for Advanced Life Cycle Engineering (CALCE) consortium
3.9
CLCC
refers to a Ceramic Leadless Chip Carrier electronic package
3.10
critical
item or function, if defective, will result in the system’s inability to retain operational capability,
meet primary objective, or affect safety
3.11
creep
refers to time dependent strain occurring under stress
3.12
CSAM
refers to C-Mode scanning acoustic microscopy, which is a method for evaluating electronic
packages for internal delamination using high frequency sound waves
3.13
CTE
refers to the coefficient of thermal expansion of a material. PCB CTE (x-y) 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
during thermal cycling. CTE(z) is measured in the “thickness” direction and is typically used to
quantify plated through hole stress
3.14
customer
refers to an entity or organization that (a) integrates a piece part, soldered assembly, unit, or
system into a higher level system, (b) operates the higher level system, or (c) certifies the
system for use. For example, this may include end item users, integrators, regulatory
agencies, operators, original equipment manufacturers (OEMs), and Subcontractors
3.15
dicy cure
refers to the use of dicyandiamide (dicy), as a curing agent for epoxy resins

PAS 62647-22  IEC:2011(E) – 13 –
3.16
EM
refers to electromigration of the PCB metallization. Resistance to electromigration testing is
typically performed between electrically biased conductors at elevated humidity and
temperature
3.17
ENIG
refers to Electroless Nickel Immersion Gold Printed Wiring Board Finish
3.18
ER
epoxy resin conformal coating
3.19
eutectic
a eutectic or eutectic mixture is a 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. 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
3.20
FR4
refers to Flame Retardant laminate made from woven glass fiber material impregnated with
epoxy resin
3.21
Fick’s law
refers to the classic diffusive mass transport model where the mass diffusion is proportional to
the concentration gradient in the material
3.22
fillet lifting
refers to a separation that occurs between a solder fillet and a PCB pad where the solder fillet
has the appearance that it has lifted off the PCB pad. The fillet lifting is caused by the
formation of a low melting point phase (often a ternary alloy) or liquid phase in an alloy having
a large pasty range. The thin layer of liquid present adjacent to the PCB pad results in a layer
that allows the solidified solder above it to pull off the PCB pad [38] [73]
3.23
high performance system or product
requires continued performance or performance on demand, or equipment down time cannot
be tolerated, or end-use environment may be uncommonly harsh, and the equipment must
function when required, such as life support or other critical systems
3.24
HALT and HAST
refers to highly accelerated life test and highly accelerated stress test, respectively
3.25
HASL
refers to the Hot Air Solder Level PCB surface finish
3.26
incubation period
in the context of Tin Pest formation refers to the time required at cold temperature to initially
form the brittle gray (α) Tin phase from the ductile white (β) Tin phase

– 14 – PAS 62647-22  IEC:2011(E)
3.27
inoculation
in the context of Tin Pest formation refers to practice of facilitating the white (β) Tin to
gray (α) Tin phase transformation by using seed particles of the gray Tin phase on the white
Tin to reduce the nucleation barrier energy associated with the transformation
3.28
ICP
refers to Inductively Coupled Plasma/Mass Spectrometry based chemical analysis
3.29
Imm Ag or Im Ag
refers to an immersion silver printed circuit board finish
3.30
JCAA
refers to the Joint Council of Aging Aircraft Organization within the US Department of
Defense. JCAA and JGPP have performed extensive Pb-free solder reliability testing
3.31
JGPP
refers to the NASA lead Joint Group on Pollution Prevention. The NASA JGPP group began
the Pb-free solder testing that was completed with the support of JCAA
3.32
Kirkendall void formation
refers to voids induced in a diffusion couple between two metals that have different
interdiffusion coefficients
3.33
lead
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
3.34
Lead-Free or Pb-Free
is defined as less than 0,1 % by weight of Lead (Pb) in accordance with Waste Electrical and
Electronic Equipment (WEEE) guidelines
3.35
LRU
is a line replaceable electronic unit
3.36
May
indicates a course of action that is permissible within the limits of this document
3.37
MSL
is the moisture sensitivity level rating of a plastic encapsulated electronic device as it relates
to soldering
3.38
Non-Eutectic
See Eutectic mixture definition

PAS 62647-22  IEC:2011(E) – 15 –
3.39
OSP
refers to Organic Solderability Preservative finishes used on PCBs
3.40
PCB
stands for Printed circuit board, which is also commonly referred to as a Printed Wiring Board
(PWB)
3.41
PEM
refers to a plastic encapsulated microcircuit
3.42
peritectic
in a peritectic reaction, a solid phase and a liquid phase react on cooling to produce a new
solid phase
3.43
piece-part
is defined as an electronic piece part that is not normally disassembled without destruction
and is normally attached to a printed wiring board to perform an electrical function
3.44
PWB
stands for Printed Wiring Board, which is also commonly referred to as a Printed Circuit Board
(PCB)
3.45
PTH
stands for the plated through holes used on printed circuit boards for interconnecting between
layers and for component attachment
3.46
repair
is the act of restoring the functional capability of a defective article in a manner that precludes
compliance of the article with applicable drawings or specifications
3.47
rework
is 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
3.48
RMA
refers to solder flux type: Rosin, Mildly Activated
3.49
RoHS
refers to the legislation enacted by the European Union on the Restriction of Hazardous
Substances, EU Directive 2002/95/EC, which places a restriction on the use of certain
hazardous substances in electrical or electronic equipment sold or used in the European
Union after July 1, 2006. These substances are lead, mercury, cadmium, hexavalent
chromium, polybrominated biphenyls, and polybrominated diphenyl ethers

– 16 – PAS 62647-22  IEC:2011(E)
3.50
SAC
refers to the family of Pb-Free alloys containing Tin, Silver and Copper used in surface mount
technology or sometimes in wave solder processes. The alloys typically have a composition
near the eutectic (Sn95,6Ag3,5Cu,9)
3.51
SAC-L
refers to low Silver content SAC alloys that are not eutectic compositions. These alloys have
increasingly been used for BGA interconnects
3.52
should
indicates that, among several possibilities, one is recommended as particularly suitable,
without mentioning or excluding others; or that a certain course of action is preferred but not
necessarily required; or that (in the negative form) a certain course of action is deprecated but
not prohibited
3.53
SIR
refers the Surface Insulation Resistance measurements performed on PCBs. These electrical
resistance measurements are often performed after periods of humidity exposure
3.54
SMT
refers to surface mount technology circuit card assembly technology
3.55
SMTA
refers to the Surface Mount Technology Association, with headquarters in Edina, MN
3.56
Sn-Cu
solder or alloy refers to Pb-Free alloys that are comprised of Tin-Copper (Sn-0.7Cu)
3.57
Sn-Cu-(Ni)
solder or alloy refers to Pb-Free Tin-Copper with trace Nickel concentration alloy (Sn-0.7Cu-
0.05Ni). Some formulations also include other minor additions such as Ge
3.58
Sn-Pb
solder generally refers to the family of Tin-Lead alloys at or near the eutectic composition with
or without Silver added (Sn-37Pb, Sn-40Pb, or Sn-3
...