IEC 61189-5-501:2021

IEC 61189-5-501 ®
Edition 1.0 2021-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for electrical materials, printed boards and other interconnection
structures and assemblies –
Part 5-501: General test methods for materials and assemblies – Surface
insulation resistance (SIR) testing of solder fluxes

Méthodes d’essai pour les matériaux électriques, les cartes imprimées et autres
structures d’interconnexion et ensembles –
Partie 5-501: Méthodes d’essai générales pour les matériaux et les ensembles –
Essais de résistance d’isolement en surface (RIS) des flux de brasage

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IEC 61189-5-501 ®
Edition 1.0 2021-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test methods for electrical materials, printed boards and other interconnection

structures and assemblies –
Part 5-501: General test methods for materials and assemblies – Surface

insulation resistance (SIR) testing of solder fluxes

Méthodes d’essai pour les matériaux électriques, les cartes imprimées et autres

structures d’interconnexion et ensembles –

Partie 5-501: Méthodes d’essai générales pour les matériaux et les ensembles –

Essais de résistance d’isolement en surface (RIS) des flux de brasage

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.180 ISBN 978-2-8322-9289-1

– 2 – IEC 61189-5-501:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Equipment/Apparatus . 7
4.1 Measurement instrument . 7
4.2 Resistor verification coupon . 8
4.3 Damp heat chamber . 8
4.4 Additional apparatus . 9
4.4.1 Ionic contamination test system . 9
4.4.2 Drying oven . 9
4.4.3 Camera . 9
4.4.4 Backlight panel . 9
5 Test coupons . 9
5.1 General . 9
5.2 IEC TB144 (IPC B53) test coupon . 9
5.3 Laminate . 10
5.4 Coupons for testing . 10
5.5 Chamber controls . 10
5.6 Blank process controls . 11
5.7 Test conditions . 11
5.7.1 Fluxes not intended for cleaning . 11
5.7.2 Fluxes intended for cleaning . 11
5.8 Test duration. 11
5.9 Test voltage . 11
5.10 Connecting the test coupons . 11
5.10.1 General . 11
5.10.2 Connector/test rack . 11
5.10.3 Direct wiring . 12
5.11 Cable connection . 12
5.12 Coupon orientation in the chamber . 12
6 Coupon preparation . 13
6.1 General . 13
6.2 Coupon cleaning . 13
6.3 Identification . 13
6.4 Inspection . 13
6.5 Storage . 13
6.6 No clean fluxes . 14
6.7 Cleanable type fluxes . 14
6.8 Solder paste coupons . 14
6.8.1 Coupon preparation . 14
6.8.2 Cleaning of coupons . 15
6.9 Preparation of coupons for chamber . 15
7 Test procedure . 15
8 Measurements . 15
9 Evaluation . 15

10 Reporting. 16
Annex A (informative) General advice for testing . 17
A.1 Test coupons . 17
A.2 Test coupon development . 17
A.3 Sampling. 17
A.3.1 General . 17
A.3.2 Coupon count . 17
A.3.3 Sample sizes . 17
A.3.4 Characterising materials . 17
A.3.5 Characterising process(es) . 17
A.3.6 Derived unit of SIR . 17
A.3.7 Set-up parameters . 18
A.4 Humidity . 18
A.5 Voltage . 18
Bibliography . 19

Figure 1 – SIR pattern . 6
Figure 2 – Example of a resistor verification coupon . 8
Figure 3 – IPC B53 Surface insulation resistance pattern . 10
Figure 4 – Connector arrangement . 12
Figure 5 – Specimen orientation in test chamber . 12
Figure 6 – Coupon orientation in test chamber . 13

Table 1 – Coupons for surface insulation resistance (SIR) testing . 14

– 4 – IEC 61189-5-501:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR ELECTRICAL MATERIALS, PRINTED BOARDS
AND OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 5-501: General test methods for materials and assemblies –
Surface insulation resistance (SIR) testing of solder fluxes

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.
IEC 61189-5-501 has been prepared by IEC technical committee 91: Electronics assembly
technology. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
91/1645/CDV 91/1672/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.

A list of all parts in the IEC 61189 series, published under the general title Test methods for
electrical materials, printed boards and other interconnection structures and assemblies, can
be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

– 6 – IEC 61189-5-501:2021 © IEC 2021
TEST METHODS FOR ELECTRICAL MATERIALS, PRINTED BOARDS
AND OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 5-501: General test methods for materials and assemblies –
Surface insulation resistance (SIR) testing of solder fluxes

1 Scope
This part of IEC 61189 is used to quantify the deleterious effects of flux residues on surface
insulation resistance (SIR) in the presence of moisture.
Interdigitated comb patterns comprising long parallel electrodes on an IPC B53 standardized
test coupon are used for the evaluation. Coupons are conditioned and measurements taken at
a high temperature and humidity. The electrodes are electrically biased during conditioning to
facilitate electrochemical reactions, as shown in Figure 1 and Figure 3.
Reference can be made to IEC TR 61189-5-506, which examines different geometry comb
patterns: 400 µm x 500 µm; 400 µm x 200 µm; and 318 µm x 318 µm.

Figure 1 – SIR pattern
Specifically, this method is designed to simultaneously assess:
• leakage current caused by ionized water films and electrochemical degradation of test
vehicle, (corrosion, dendritic growth);
• provide metrics that can appropriately be used for binary classification (e.g. go/no go;
pass/fail);
• compare, rank or characterize materials and processes.
This test is carried out at high humidity and heat conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-58, Environmental testing – Part 2-58: Tests – Test Td: Test methods for
solderability, resistance to dissolution of metallization and to soldering heat of surface mounting
devices (SMD)
IEC 60068-2-67, Environmental testing – Part 2-67: Tests – Test Cy: Damp heat, steady state,
accelerated test primarily intended for components

IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady state
IEC 60194-2, Printed boards design, manufacture and assembly – Vocabulary – Part 2:
Common usage in electronic technologies as well as printed board and electronic assembly
technologies
IEC 61189-5-504, Test methods for electrical materials, printed board and other interconnection
structures and assemblies – Part 5-504: General test methods for materials and assemblies –
Process ionic contamination testing (PICT)
IEC TR 61189-5-506, Test methods for electrical materials, printed boards and other
interconnection structures and assemblies – Part 5-506: General test methods for materials and
assemblies – An intercomparison evaluation to implement the use of fine pitch test structures
for surface insulation resistance (SIR) testing of solder fluxes in accordance with IEC 61189-5-
IEC 61190-1-3, Attachment materials for electronic assembly – Part 1-3: Requirements for
electronic grade solder alloys and fluxed and non-fluxed solid solder for electronic soldering
applications
IEC 61249-2-7, Materials for printed boards and other interconnecting structures – Part 2-7:
Reinforced base materials clad and unclad – Epoxide woven E-glass laminated sheet of defined
flammability (vertical burning test), copper-clad
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60068-1, IEC 60068-
2-58, IEC 60194-2, and IEC 61190-1-3 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Equipment/Apparatus
4.1 Measurement instrument
This shall consist of a measuring device capable of measuring insulation resistance in the range
6 12
of at least 10 Ω to 10 Ω.
It shall be capable of measuring and recording each individual test channel/pattern. The
measurement circuit shall incorporate a 1 MΩ current limiting resistor in each current pathway.
The tolerance of the total measurement system shall be
• ±5 % up to 10 Ω at 5 V;
10 11
• ±10 % between 10 Ω to 10 Ω at 5 V;
• ±20 % above 10 Ω at 5 V.
If a different test voltage is to be used, the measurement circuit shall be assessed at that voltage
rather than the 5 V stipulated. See Clause A.5 for additional information on test voltages.
The resistors used to confirm the ‘total measurement system tolerance’ defined above, shall
have a purchased tolerance of
• ±0,1 % up to and including 10 Ω;
6 8
• ±1 % above 10 Ω and up to and including 10 Ω;
8 10
• ±5 % above 10 Ω and up to and including 10 Ω;
• ±10 % above 10 Ω.
– 8 – IEC 61189-5-501:2021 © IEC 2021
The instrument can be used with either an external or internal power supply but shall be capable
of delivering a variable voltage from (5 to 100) V DC ±1 % with a 1 MΩ load and a channel to
channel isolation resistance of 10 Ω.
The system shall be capable of taking measurements in the time interval required.
Equipment shall have the measurement capability to repeat the resistance measurement on all
channels at least every 20 minutes.
4.2 Resistor verification coupon
The measurement system measurement performance shall be verified by substituting a resistor
verification coupon (see Figure 2) in place of the test coupons while in the chamber at both
ambient and elevated conditions. This coupon should be fitted with at least 4 “known value”
resistors. The tolerances for the “known value” resistors shall be as per the purchased
tolerances defined in 4.1.
Figure 2 – Example of a resistor verification coupon
4.3 Damp heat chamber
A damp heat chamber capable of being adjusted to a temperature of 20 °C ± 2 °C to
°
C and of relative humidity between 80 % RH ± 3 % RH and 90 % RH ± 3% RH
100 °C ± 2
according to IEC 60068-2-67 and IEC 60068-2-78 shall be used.
If the alternative conditions of 40 °C / 93 % RH are to be used, the damp heat chamber shall
be capable of the upper humidity level of 93 % RH ± 3 % RH rather than the 90 % RH ± 3% RH
specified above. See 5.7.1 and Clause A.4 for additional information.
The chamber should be constructed with stainless steel inner surfaces and be well insulated.
The temperature and humidity measurement should be taken using sensors such as dry and
wet bulb thermometers or solid-state sensors. The temperature and humidity levels of the test
chamber shall be recorded at a minimum of 5 minute intervals throughout the test, preferably
with independent control sensors.
The location of the samples within the chamber should ensure that the airflow within is not
impeded.
Adequate mixing of water vapour and air is imperative to ensure condensation does not occur
anywhere in the chamber except on/around cooling or dehumidification coils. If any part of
interior of the chamber is below the dew point, possibly due to insulation or control issues,
condensation will occur. The samples shall be kept above the dew point and be shielded from
dripping or flying condensate.

The chamber interior shall be free from any unwanted residues from previous tests. The
chamber should have been dedicated to heat and humidity testing only and not used for tests
such as salt fog, salt mist or salt spray.
4.4 Additional apparatus
4.4.1 Ionic contamination test system
If the user does not have an ionic contamination test system, as described in IEC 61189-5-504,
then the following additional items shall be needed:
• lint-free handling gloves;
• three 2 l beakers;
• exhaust ventilation hood;
• metal tongs;
• soft bristle brush;
• deionised or distilled water maximum 15 µS/cm of sufficient volume to carry out cleaning as
per 6.2;
• propan-2-ol (IPA) of sufficient volume to carry out cleaning as per 6.2.
4.4.2 Drying oven
Capable of maintaining at least 50 °C.
4.4.3 Camera
A camera for recording full colour photographs of test coupons.
4.4.4 Backlight panel
Suitable for inspecting test coupons after testing for evidence of dendritic growth or other
anomalies.
5 Test coupons
5.1 General
It has been the practice for different test coupons to be used that has led to confusion in respect
to comparing test results. In addition, previous revisions of this and other test methods, have
conflicting requirements in respect to the voltage gradient and test voltages to be used. To
resolve this confusion, a comprehensive “round-robin” research study was conducted that
employed a new test coupon that includes test pattern characteristics of the following test
coupons: IPC B24; “Bellcore”; IEC 61189-5 Method 5E01.
The full technical report IEC TR 61189-5-506 of this separate research study should be
reviewed.
5.2 IEC TB144 (IPC B53) test coupon
The test pattern IEC TB144 from IEC TR 61189-5-506, now known as IPC B53 and shown in
Figure 3, shall be used for the test coupon. The 6 comb patterns comprise A and F patterns of
0,4 mm line width and 0,2 mm spacing, comprising 5 125 squares (IEC 61189-5 Method 5E01);
B and E patterns have 0,4 mm line width and 0,5 mm spacing, comprising 1 020 squares (IPC
B24); C and D patterns have 0,318 mm line width and 0,318 mm spacing, comprising 1 950
squares (Bellcore).
Pattern G (the central Y pattern), and the squares and dots (adhesion test pattern) identified as
A and B, are not a requirement for SIR testing; all other test patterns shall be evaluated as part
of this test.
The coupon is approximately 150 mm × 95 mm in size. The conductive patterns shall be either
unpreserved bare copper or finished with electroless nickel gold (ENIG).

– 10 – IEC 61189-5-501:2021 © IEC 2021

Figure 3 – IPC B53 Surface insulation resistance pattern
5.3 Laminate
The laminate material for this test coupon shall be an epoxide woven E-glass laminated sheet
in accordance with IEC 61249-2-7.
5.4 Coupons for testing
The type and number of test coupons as well as method of preparation and test requirements
should be described in the governing specification or procurement documentation; see Annex A
for recommendations.
The coupons shall be handled in a way that minimizes the possibility of contamination such as
from finger salts. Refer to 6.2.
5.5 Chamber controls
Two cleaned bare IPC B53 test coupons shall be used as chamber controls.
Visually inspect the coupons for any obvious defects. If there is any doubt about the overall
quality of any test coupon, it shall be discarded.
Prior to running a test, the chamber should be run at the intended test conditions for not less
than 8 h. This should be carried out after 60 days of test operations to minimise the risk of any
residues influencing subsequent tests.

Before commencing each test, the interior surfaces of the chamber shall be wiped using propan-
2-ol (IPA) and a suitable lint-free cloth.
5.6 Blank process controls
It is recommended that a single bare control coupon be included in each test.
5.7 Test conditions
5.7.1 Fluxes not intended for cleaning
If the flux contains more than 1 % by weight organic acid activators, such as adipic acid that
volatilise significantly at 85 °C, and contain less than 5 % by weight rosin or modified-rosin
resin, the test shall be conducted at 40 °C ± 2 °C and 90 % RH ± 3 % RH.
As an alternative to 40 °C ± 2 °C and 90 % RH ± 3 % RH, it is acceptable to use 40 °C ± 2°C
and 93 % RH ± 3%. If 93 % RH is desired to be used instead of 90 % RH (at 40 °C), this shall
be agreed between user and supplier prior to use. Using 93 % RH could lead to different results
when compared to using 90 % RH. See Clause A.4 for additional details.
5.7.2 Fluxes intended for cleaning
If the flux contains more than 0,1 % by weight ionic halide and the intended end-product is to
be cleaned, the test shall be conducted at 85 °C ± 2 °C and 85 % RH ± 3 % RH.
5.8 Test duration
The test duration shall be not less than 72 h.
5.9 Test voltage
Testing shall be conducted using a test and measurement voltage of 5 V DC. Alternative
voltages are acceptable, if agreed between user and supplier. See Clause A.5 for additional
information on test voltages.
5.10 Connecting the test coupons
5.10.1 General
The interconnecting cabling between the measurement instrument and the test coupon shall
ensure accurate and reliable measurements to be recorded, as the measurements are being
made at pico-Amp levels >10 Ω.
Halogen-Free, shielded, cable should be used so as to minimise any electrical noise or tribo-
electrical interference.
The connection of the test coupons to the measurement system may be done in 1 of 2 ways as
described in 5.10.2 and 5.10.3.
5.10.2 Connector/test rack
This comprises a set of connectors that shall be suitable for the test coupons and able to tolerate
the test environment over repeated test cycles, see Figure 4 and Figure 5 for examples.
These connectors shall be mounted onto a suitable support frame. An electro-polished stainless
steel frame is the most durable type but others may be employed provided that they will not
adversely influence the test measurements.
There shall be a measurement cable soldered in the appropriate pattern that is secured to the
frame for connection to the measurement system.
Prior to connecting test coupons to the measurement system, each cable assembly shall be
connected to a resistor verification coupon (see 4.2) inside the humidity chamber at ambient
conditions and a measurement taken. Any cable that does not read within the tolerance value
of the total measurement system, as defined in 4.1, shall be reworked or replaced.

– 12 – IEC 61189-5-501:2021 © IEC 2021
5.10.3 Direct wiring
Direct wired coupons need to be soldered without adverse effect to the test coupons. The
coupon should be covered during this process to protect the patterns from cross-contamination
of this soldering process. Additional information can be found in IPC 9201 which can assist the
user.
Take care to avoid coupon damage by overheating the coupons during this soldering process.
Solid wire solder should be used. If flux is deemed necessary by qualitative observation, use
rosin non-activated flux.
5.11 Cable connection
The cables from the test rack or the direct wired coupons shall retain relationship of
interconnection between test coupon and testing system (nets, channels, etc.).

Figure 4 – Connector arrangement

Figure 5 – Specimen orientation in test chamber
5.12 Coupon orientation in the chamber
Mount the coupons in the chamber uniformly, vertically, and parallel to airflow as shown in
Figure 6. The minimum spacing between coupons shall be 12,5 mm to facilitate good air flow
between each test coupon.
Provision should be made to avoid any water droplets falling or blowing onto the coupons, for
example a drip guard may be necessary.
If a test rack is being used, a rain shield should be used to avoid the possibility of condensation
raining onto the test coupons.

Figure 6 – Coupon orientation in test chamber
Connect the voltage source to the coupon test points to apply the bias voltage to all coupons.
6 Coupon preparation
6.1 General
There shall be not less than three test coupons for each liquid flux or solder paste to be tested.
Patterns A through F shall be prepared and tested on each coupon.
6.2 Coupon cleaning
Place the test coupons in an ionic contamination tester containing 50 % propan-2-ol, 50 %
deionized water and process the solution until a resistivity measure of >20 MΩ has been
achieved. A mixture of 25 % propan-2-ol, 75 % deionised water may alternatively be used. See
IEC 61189-5-504 for additional information on ionic contamination testing.
Alternatively, clean each of the test coupons with deionized or distilled water and scrub with a
soft bristle brush for a minimum of 30 seconds. Spray-rinse thoroughly with deionized or distilled
water. Rinse cleaned area thoroughly with fresh propan-2-ol.
During the remainder of the coupon preparation, handle test coupons by the edges only, or use
lint-free, non-contaminating gloves.
Dry the cleaned coupons for 2 h at 50 °C.
If the coupons are to be stored before treatment, place them into contamination-free containers
or a desiccator.
When measured as described in Clauses 4 and 5, if the control coupon readings are less than
1 000 MΩ at any point after the initial 24 h of SIR exposure, a new set of test coupons shall be
obtained and the entire test repeated.
6.3 Identification
Positive, permanent and non-contaminating identification of test coupons is of paramount
importance for example, a vibrating scribe.
6.4 Inspection
Visually inspect the test coupons for any obvious defects. If there is any doubt about the overall
quality of any test coupon, the test coupon shall be discarded.
6.5 Storage
If boards are to be stored before treatment, place the boards in contamination-free bags or
containers with a desiccant.
– 14 – IEC 61189-5-501:2021 © IEC 2021
6.6 No clean fluxes
When testing liquid fluxes that are intended to remain in the un-cleaned state, a minimum of six
test coupons are required. Three uncleaned test coupons shall be wave soldered pattern side
down (see Table 1, Sample group B) and three shall be wave soldered pattern side up (see
Table 1, Sample group C).
Table 1 – Coupons for surface insulation resistance (SIR) testing
Sample group Flux/Solder Clean Number of coupons
A Yes Yes 3
B Yes No 3
C Yes No 3
D Yes Yes 3
E Yes No 3
F No No 2
After exposure to flux and solder, coupons to be tested in an un-cleaned state shall be evaluated
as described in Clauses 8 and 9.
6.7 Cleanable type fluxes
After exposure to flux and solder, coupons to be tested in the cleaned state shall be cleaned
using one of the procedures listed below. The cleaning parameters shall be reported in the
qualification test report.
The coupons to be cleaned shall be cleaned with an appropriate environmentally safe solvent
or aqueous cleaning medium. The use of a commercial batch or in-line cleaner is preferred.
If this is not available, the following laboratory cleaning process shall be followed: Three
coupons shall be cleaned within a maximum of 30 minutes after soldering.
For solvent or aqueous detergent cleaning, three 2 000 ml beakers each containing 1 000 ml of
solvent shall be used so that one beaker serves as the primary cleaning stage and the other
two are used for rinsing purposes. Each test coupon shall be agitated in each beaker for 1 min.
In the case of aqueous detergent, one beaker shall contain the cleaning agent and the remaining
beakers shall contain deionised water for rinsing purposes.
After the cleaning procedure is complete, coupons are dried for 2 h at 50 °C. Following cleaning,
the coupons shall be tested as outlined in Clauses 8 and 9.
6.8 Solder paste coupons
6.8.1 Coupon preparation
Stencil print the solder paste on to the preferred comb patterns using a 0,150 mm thick stencil.
The stencil shall consist of a series of circular holes of a diameter of 0,4 mm for patterns A, B,
E and F, and 0,3 mm for patterns C and D, or square openings that match the conductors of
the comb pattern. The registration of the stencil shall be such that the solder paste is deposited
directly on the conductors and does not cause bridging between conductive patterns. There
shall be a minimum of six openings for each conductor in the comb pattern.
The coupons shall be run through a reflow soldering process using the temperature profile
recommended by the solder paste supplier.
These shall be reflowed pattern side up and either cleaned (Table 1, Sample group D) or not
cleaned (Table 1, Sample group E). In addition, there shall be at least two unprocessed control
coupons for comparison purposes (Table 1, Sample group F).

6.8.2 Cleaning of coupons
a) No-clean paste: After exposure to flux and solder, coupons to be tested in an un-cleaned
state shall be evaluated as described in Clauses 8 and 9.
b) Cleanable paste: prepare as per 6.6.
6.9 Preparation of coupons for chamber
Visually inspect all test coupon combs and disregard any coupons that exhibit conductor
bridging.
7 Test procedure
Seal the chamber and ramp from laboratory ambient conditions to 25 ºC ± 2 °C and 50 % RH
± 3% RH. Dwell for 1 h.
Verify the electrical system setup by taking a series of all measurements at these specified
ambient conditions. Because classification or ranking of sample performance by SIR at ambient
is not appropriate for these test vehicles, clarity suggests that measurements need not be
reported unless “shorts” are observed and therefore the corresponding samples are deemed
inappropriate for test.
Increase the temperature to 40 ºC ± 2 °C or 85 °C ± 2 °C, depending on the flux chemistry
being evaluated (see 5.7) while maintaining the humidity at 50 % RH ± 3 % RH and dwell at
this temperature for 15 min. After this period, gradually increase, within 30 min, the relative
humidity to 85 % RH ± 3 % RH or 90 % RH ± 3 % R.H depending on the flux chemistry being
evaluated (see 5.7). Do not allow the temperature of the samples to drop below the dew point.
Allow the chamber to stabilise at the set point for 1 h.
If the alternative conditions of 40 °C ± 2°C and 93 % RH ± 3 % are being employed, the chamber
shall be increased to 93 % RH ± 3 % RH rather than the 90 % RH ± 3 % RH referenced above.
See Clause A.4 for additional details.
The duration of the test shall not be less than 72 h.
8 Measurements
Measurement and stress bias voltage shall be the same.
Measurements shall be made with test coupons in the chamber under the test conditions of
temperature and humidity at not less than 20 minute intervals. To take these measurements,
the stress bias voltage source shall be removed from the test coupon and the measurement
voltage shall be applied. Unless a different voltage is agreed between user and supplier, the
voltage for both stress and measurement shall be 5 V DC.
The stress bias voltage shall be applied during an aggregate 90 % (minimum) of the
temperature and humidity conditioning (remaining percentage is related to measurement) in
order to facilitate electrochemical reactions.
9 Evaluation
After conditioning, remove the coupons from the chamber and examine at 30x to 40x in light
field and dark field (back light). Record the following:
a) presence of dendrites: Yes/No
b) maximum percent reduction of spacing: 0 % for no dendrites 1 % to 100 % for worst-case
dendrite; capture and record image of worst case dendrite;
c) presence of discoloration between conductors: Yes/No; if yes, capture and record image.
d) presence of water spots: Yes/No; if Yes, capture and record the image.
e) presence of subsurface metal migration: Yes/No; if Yes, capture and record the image.

– 16 – IEC 61189-5-501:2021 © IEC 2021
The insulation resistance values of each comb pattern shall be greater than 1 × 10 Ω. If the
control coupon readings are less than 1 × 10 Ω, a new set of test specimens shall be obtained
and the entire test repeated. Any reason for deleting values (scratches, condensation, bridged
conductors, outlying points, etc.) shall be noted.
10 Reporting
Deviations from the te
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