IEC PAS 62483:2006

Test method for measuring whisker growth on tin and tin alloy surface finishes

Provides the methodology applicable for studying tin whisker growth from finishes containing a predominance of tin (Sn). This test method may not be sufficient for applications with special requirements, e.g., military or aerospace. Additional requirements may be specified in the appropriate requirements document

General Information

• Status: Replaced
• Publication Date: 11-Sep-2006
• ICS: 31.080.01 - Semiconductor devices in general
• Technical Committee: TC 47 - Semiconductor devices
• Drafting Committee: WG 2 - TC 47/WG 2
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 25-Sep-2013

Relations

• Replaced By: IEC 62483:2013 - Environmental acceptance requirements for tin whisker susceptibility of tin and tin alloy surface finishes on semiconductor devices
• Effective Date: 05-Sep-2023

Standards Content (Sample)

PUBLICLY
IEC
AVAILABLE
PAS 62483
SPECIFICATION
First edition
2006-09
Test method for measuring whisker growth
on tin and tin alloy surface finishes

Reference number
IEC/PAS 62483:2006(E)
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PUBLICLY
IEC
AVAILABLE
PAS 62483
SPECIFICATION
First edition
2006-09
Test method for measuring whisker growth
on tin and tin alloy surface finishes
 IEC 2006  Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch

PRICE CODE
U
For price, see current catalogue

PAS 62483 © IEC:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHOD FOR MEASURING WHISKER GROWTH
ON TIN AND TIN ALLOY SURFACE FINISHES

FOREWORD
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all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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A PAS is a technical specification not fulfilling the requirements for a standard but made
available to the public.
IEC-PAS 62483 was submitted by JEDEC and has been processed by IEC technical
committee 47: Semiconductor devices.
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
47/1842/NP 47/1876/RVN
Following publication of this PAS, the technical committee or subcommittee concerned will
investigate the possibility of transforming the PAS into an International Standard
An IEC-PAS licence of copyright and assignment of copyright has been signed by the IEC
and JEDEC and is recorded at the Central Office.
This PAS shall remain valid for an initial maximum period of three years starting from
2006-08. The validity may be extended for a single three-year period, following which it shall
be revised to become another type of normative document or shall be withdrawn.
Page i
Test Method for Measuring Whisker Growth on Tin
and Tin Alloy Surface Finishes

Introduction
This document contains a suite of recommended tin whisker growth tests. If these common
tests are adopted, then the industry can collect common and comparable data that may
improve the understanding of the fundamentals of whisker growth and allows comparisons
between technologies. Tests in this document may be changed in the future as a better
understanding of the mechanisms causing tin whisker growth is developed.

Based on a variety of testing and data review from around the globe, three test conditions
have been identified that appear to be suitable for monitoring tin whisker growth. The three
test conditions include two isothermal conditions with controlled humidity and a thermal
cycling condition. However, these test conditions have not been correlated with longer
environmental exposures of components in service. Thus, there is at present no way to
quantitatively predict whisker lengths over long time periods based on the lengths measured
in the short-term tests described in this document. At the time of writing, the fundamental
mechanisms of tin whisker growth are not fully understood and acceleration factors have not
been established. Certain applications, e.g., military or aerospace, may require additional
and/or different tin whisker tests or evaluations.

The predominant terminal finishes on electronic components have been Sn-Pb alloys. As
the industry moves toward Pb-free components and assembly processes, the predominant
terminal finish materials will be pure Sn and alloys of Sn, including Sn-Bi and Sn-Ag.

Pure Sn and Sn-based alloy electrodeposits and solder-dipped finishes may grow tin
whiskers, which could electrically short across component terminals or break off the
component and degrade the performance of electrical or mechanical parts.

Page 2 Copyright © 2005, JEDEC; 2006, IEC

Test Method for Measuring Whisker Growth on Tin
and Tin Alloy Surface Finishes
(TEST METHOD A121)
1 Scope
The methodology presented in this document, see Annex A for process flow, is applicable for
studying tin whisker growth from finishes containing a predominance of tin (Sn). This test
method may not be sufficient for applications with special requirements, e.g., military or
aerospace. Additional requirements may be specified in the appropriate requirements
document.
The purpose of this PAS is to:

• Provide an industry-standardized suite of tests for measurement and comparison of
whisker propensity for different plating or finish chemistries and processes.
• Provide a consistent inspection protocol for tin whisker examination.
• Provide a standard reporting format.

2 Normative references
JESD22-A104, Standard for Temperature Cycling

IPC 7530, Guidelines for Temperature Profiling for Mass Soldering (Reflow & Wave)
Processes
3 Terms and definitions
3.1 total axial whisker length: The distance between the finish surface and the tip of
the whisker that would exist if the whisker were straight and perpendicular to the surface.

NOTE For tin whiskers that bend and change directions, the total axial length can be estimated by
adding all of the straight subdivisions of the whisker. (See Figure 5.)

3 Terms and definitions (cont’d)

3.2 whisker: A spontaneous columnar or cylindrical filament, usually of monocrystalline
metal, emanating from the surface of a finish. (See Annex C for example pictures of tin
whiskers.)
NOTE 1 For the purpose of this document, whiskers have the following characteristics:
• An aspect ratio (length/width) greater than 2
• Can be kinked, bent, or twisted
• Usually have a uniform cross-sectional shape
• Typically consist of a single columnar filament that rarely branches
• May have striations along the length of the column and/or rings around the circumference
of the column
• Length of 10 microns or more. Features less than 10 microns may be deemed important
for research but are not considered significant for this test method.

NOTE 2 Whiskers are not to be confused with dendrites: fern-like growths on the surface of a
material which can be formed as a result of electromigration of an ionic species or produced during
solidification. (See Annex D for a picture of a typical solidification dendrite.)

3.3 whisker density: The number of whiskers per unit area on a single lead or coupon
area.
3.4 whisker growth: Measurable changes in whisker length and/or whisker density after
exposure to a whisker test condition for a certain duration or number of cycles.

3.5 whisker test coupon: A piece of metal of specified size and shape that is plated or
dipped with a tin finish for the purpose of measuring the propensity for whisker formation and
growth.
4 Apparatus
4.1 Temperature cycling chambers

Air to air temperature cycling chamber(s), capable of cycling from -55 (+0/-10) °C to
+85(+10/-0) °C or from -40(+0/-10) °C to +85(+10/-0) °C. The temperature cycling
chamber(s) must be able to satisfy the cycle conditions defined in Table 4.

Page 4 Copyright © 2005, JEDEC; 2006, IEC

4 Apparatus (cont’d)
4.2 Temperature humidity chambers

Temperature–humidity (T&H) chambers capable of non-condensing 60 ±5 °C, 87 +3/-2% RH
and 30 ±2 °C, 60 ±3% RH environment.

NOTE 1 The elevated temperature–humidity condition of 60 ±5 °C, 87 +3/-2% RH is close to the
condensation point. If water condenses on the tin finish during environmental exposure, the
condensed moisture and resulting corrosion may affect the final test results. To prevent condensation
in the T & H chamber, the chamber dry-bulb temperature must exceed the wet-bulb temperature at all
times by not less than 2.4 °C (or equivalent for electronic sensors). Before opening of the chamber
door for loading and unloading, the chamber temperature and humidity should be ramped down
sufficiently close to room ambient (recommended within 10 °C and 10% RH) to prevent condensation
on the test samples and chamber walls.

NOTE 2 During operation, condensation is most likely to occur on the T & H test chamber walls and
ceiling; therefore, it is recommended that the test samples be sufficiently shielded from any condensed
water that may drip from the chamber ceiling and/or walls onto the samples.

NOTE 3 When loading the test samples into the T & H test chamber, the sample temperature must
be sufficiently higher than the chamber ambient temperature to avoid condensation on the test
samples. It is recommended that the test samples and all sample trays or holders be preheated (to a
temperature equal to the test temperature of the T & H test chamber) in a dry-bake oven prior to
loading them into the T & H test chamber.

NOTE 4 Frequent wet-bulb maintenance is required for proper control of this test condition.

4.3 Optical stereomicroscope (Optional)

Optical stereomicroscope with adequate lighting capable of 50X to 150X magnification and
capable of detecting whiskers with a minimum axial length of 10 microns, per Annex B. If tin
whiskers are measured with an optical system, then the system must have a stage that is
able to move in three dimensions and rotate, such that whiskers can be positioned
perpendicular to the viewing direction for m
...