IEC 60068-2-20:2008

IEC 60068-2-20 ®
Edition 5.0 2008-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-20: Tests – Test T: Test methods for solderability and resistance to
soldering heat of devices with leads

Essais d’environnement –
Partie 2-20: Essais – Essai T: Méthodes d'essai de la brasabilité et de la
résistance à la chaleur de brasage des dispositifs à broches

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IEC 60068-2-20 ®
Edition 5.0 2008-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-20: Tests – Test T: Test methods for solderability and resistance to
soldering heat of devices with leads

Essais d’environnement –
Partie 2-20: Essais – Essai T: Méthodes d'essai de la brasabilité et de la
résistance à la chaleur de brasage des dispositifs à broches

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
R
CODE PRIX
ICS 19.040 ISBN 978-2-88910-037-8
– 2 – 60068-2-20 © IEC:2008
CONTENTS
FOREWORD.4
1 Scope and object.6
2 Normative references .6
3 Terms and definitions .7
4 Test Ta: Solderability of wire and tag terminations.8
4.1 Object and general description of the test.8
4.1.1 Test methods.8
4.1.2 Specimen preparation.8
4.1.3 Initial measurements .9
4.1.4 Accelerated ageing.9
4.2 Method 1: Solder bath .9
4.2.1 Description of the solder bath .9
4.2.2 Flux .10
4.2.3 Procedure.10
4.2.4 Test conditions .10
4.2.5 Final measurements and requirements .11
4.3 Method 2: Soldering iron at 350 °C.11
4.3.1 Description of soldering irons .11
4.3.2 Solder and flux .12
4.3.3 Procedure.12
4.3.4 Final measurements and requirements .13
4.4 Information to be given in the relevant specification .13
5 Test Tb: Resistance to soldering heat.13
5.1 Object and general description of the test.13
5.1.1 Test methods.13
5.1.2 Initial measurements .14
5.2 Method 1: Solder bath .14
5.2.1 Description of the solder bath .14
5.2.2 Flux .14
5.2.3 Procedure.14
5.2.4 Test conditions .14
5.2.5 De-wetting .15
5.3 Method 2: Soldering iron .15
5.3.1 Description of soldering iron .15
5.3.2 Solder and flux .15
5.3.3 Procedure.15
5.4 Recovery.16
5.5 Final measurements and requirements .16
5.6 De-wetting (if applicable).16
5.7 Information to be given in the relevant specification .17
Annex A (informative) Example of apparatus for accelerated steam ageing process .18
Annex B (normative) Specification for flux constituents .19
Bibliography.20

Figure 1 – Diagram of contact angle .7

60068-2-20 © IEC:2008 – 3 –
Figure 2 – Position of soldering iron.12
Figure A.1 – Example of apparatus .18

Table 1 – Solderability, Solder bath method: Test severities (duration and temperature).11
Table 2 – Resistance to soldering heat, Solder bath method: Test severities (duration
and temperature) .15

– 4 – 60068-2-20 © IEC:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-20: Tests –
Test T: Test methods for solderability
and resistance to soldering heat of devices with leads

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
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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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
International Standard IEC 60068-2-20 has been prepared by IEC technical committee 91:
Electronics assembly technology.
This fifth edition cancels and replaces the fourth edition, published in 1979 and its
Amendment 2 (1987). Amendment 2 includes Amendment 1. This fifth edition constitutes a
technical revision and includes test conditions and requirements for use of lead-free solder.
The major technical changes with regard to the fourth edition are the following:
– the solder globule test is deleted;
– test conditions and requirements for lead-free solders are added.

60068-2-20 © IEC:2008 – 5 –
This bilingual version, published in 2009-08, corresponds to the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
91/764/FDIS 91/774/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60068 series, under the general title Environmental testing,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60068-2-20 © IEC:2008
ENVIRONMENTAL TESTING –
Part 2-20: Tests –
Test T: Test methods for solderability
and resistance to soldering heat of devices with leads

1 Scope and object
This part of IEC 60068 outlines Test T, applicable to devices with leads. Soldering tests for
surface mounting devices (SMD) are described in IEC 60068-2-58.
This standard provides procedures for determining the solderability and resistance to
soldering heat of devices in applications using solder alloys, which are eutectic or near
eutectic tin lead (Pb), or lead-free alloys.
The procedures in this standard include the solder bath method and soldering iron method.
The objective of this standard is to ensure that component lead or termination solderability
meets the applicable solder joint requirements of IEC 61191-3 and IEC 61191-4. In addition,
test methods are provided to ensure that the component body can resist against the heat load
to which it is exposed during soldering.
NOTE Information about wetting time and wetting force can be obtained by test methods using a wetting balance.
See IEC 60068-2-54 (solder bath method) and IEC 60068-2-69 (solder bath and solder globule method for SMDs).
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 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-66, Environmental testing – Part 2: Test methods – Test Cx: Damp heat, steady
state (unsaturated pressurized vapour)
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60194, Printed board design, manufacture and assembly – Terms and definitions
IEC 61191-3, Printed board assemblies – Part 3: Sectional specification – Requirements for
through-hole mount soldered assemblies
IEC 61191-4, Printed board assemblies – Part 4: Sectional specification – Requirements for
terminal soldered assemblies
60068-2-20 © IEC:2008 – 7 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
colophony
natural resin obtained as the residue after removal of turpentine from the oleo-resin of the
pine tree, consisting mainly of abietic acid and related resin acids, the remainder being resin
acid esters
NOTE "Rosin" is a synonym for colophony, and is deprecated because of the common confusion with the generic
term "resin".
3.2
contact angle
in general the angle enclosed between two planes, tangent to a liquid surface and a
solid/liquid interface at their intersection (see Figure 1). In particular the contact angle of
liquid solder in contact with a solid metal surface

Contact angle
Liquid
Solid
IEC  1234/08
Figure 1 – Diagram of contact angle
3.3
wetting
formation of an adherent coating of solder on a surface. A small contact angle is indicative of
wetting
3.4
non-wetting
inability to form an adherent coating of solder on a surface. In this case the contact angle is
greater than 90°
3.5
de-wetting
retraction of molten solder on a solid area that it has initially wetted
NOTE In some cases an extremely thin film of solder may remain. As the solder retracts the contact angle
increases.
3.6
solderability
ability of the termination or lead of device to be wetted by solder at the temperature of the
termination or lead which is assumed to be the lowest temperature in the soldering process
within solderable temperature of solder alloy

– 8 – 60068-2-20 © IEC:2008
3.7
soldering time
time required for a defined surface area to be wetted under specific conditions
3.8
resistance to soldering heat
ability of device to withstand the highest temperature of the termination or lead in soldering
process, within applicable temperature range of solder alloy
3.9
lead-free solder
alloy that does not contain more than 0,1 % lead (Pb) by weight as its constituent and is used
for joining components to substrates or for coating surfaces
[75.1904 of IEC 60194]
4 Test Ta: Solderability of wire and tag terminations
4.1 Object and general description of the test
4.1.1 Test methods
Test Ta provides two different test methods to determine the solderability of the areas on wire
and tag terminations that are required to be wetted by solder.
– Method 1: Solder bath
– Method 2: Soldering iron
The test method to be used shall be indicated in the relevant specification. The solder bath
method is the one which simulates most closely the soldering procedures of flow soldering
and similar soldering processes.
The soldering iron method may be used in cases where Method 1 is impracticable.
If required by the relevant specification, the test conditioning may be preceded by accelerated
ageing. The following are recommended conditions:
Ageing 1a: 1 h steam ageing
Ageing 1b: 4 h steam ageing
Ageing 2: 10 days damp heat, steady state condition (40 ± 2) °C; (93 ± 3) % RH
(Test Cab)
Ageing 3a: 4 h at 155 °C dry heat (Test Bb)
Ageing 3b: 16 h at 155 °C dry heat (Test Bb).
Ageing 4: 4 h unsaturated pressurized vapour (Test Cx)
NOTE The test specimens may be introduced into the chamber at any temperature from laboratory temperature to
the specified temperature.
4.1.2 Specimen preparation
The surface to be tested shall be in the "as received" condition and shall not be subsequently
touched by the fingers or otherwise contaminated.
The specimen shall not be cleaned prior to the application of a solderability test. If required by
the relevant specification, the specimen may be degreased by immersion in a neutral organic
solvent at room temperature.
60068-2-20 © IEC:2008 – 9 –
4.1.3 Initial measurements
The specimens shall be visually examined and, if required by the relevant specification,
electrically and mechanically checked.
4.1.4 Accelerated ageing
If accelerated ageing is required by the relevant specification, one of the following procedures
shall be adopted. At the end of the conditioning, the specimen shall be subjected to standard
atmospheric conditions for testing for not less than 2 h and not more than 24 h.
NOTE Terminations may be detached if the ageing temperature is higher than the component's maximum
operating or storage temperature, or if the component is likely to degrade considerably at 100 °C in steam and thus
affect the solderability in a manner which would not normally occur in natural ageing.
4.1.4.1 Ageing 1
The relevant specification shall indicate whether ageing 1a (1 h in steam) or ageing 1b (4 h in
steam) is to be used. For these procedures the specimen is suspended, preferably with the
termination vertical, with the area to be tested positioned 25 mm to 30 mm above the surface
of boiling distilled water which is contained in a borosilicate glass or stainless steel vessel of
suitable size (e.g., a 2 litre beaker). The termination shall be not less than 10 mm from the
walls of the vessel.
The vessel shall be provided with a cover of like material consisting of one or more plates
which are capable of covering approximately seven-eighths of the opening. A suitable method
of suspending the specimens shall be devised; perforations or slots in the cover are permitted
for this purpose. The specimen holder shall be non-metallic.
The level of water shall be maintained by the addition of hot distilled water, added gradually in
small quantities, so that the water will continue to boil vigorously; alternatively a reflux con-
denser may be provided if desired. (See Figure A.1).
4.1.4.2 Ageing 2
Specimens are subjected to 10 days damp heat, steady state, according to IEC 60068-2-78,
Test Ca: Damp heat, steady state.
4.1.4.3 Ageing 3
Specimens are subjected to 4 h (Ageing 3a) or 16 h (Ageing 3b) dry heat at 155 °C according
to IEC 60068-2-2, Test B: Dry heat.
4.1.4.4 Ageing 4
Specimens are subjected to 4 h at 120 °C and 85 % RH according to IEC 60068-2-66, Test
Cx: Damp heat, steady state (unsaturated pressurized vapour).
4.2 Method 1: Solder bath
This method provides a procedure for assessing the solderability of wires, tags, and termina-
tions of irregular form.
4.2.1 Description of the solder bath
The solder bath shall be not less than 40 mm in depth and not less than 300 ml in volume.
The bath shall contain solder as specified in Table 1.

– 10 – 60068-2-20 © IEC:2008
4.2.2 Flux
The flux to be used shall consist of 25 % by weight of colophony in 75 % by weight of 2-
propanol (isopropanol) or of ethyl alcohol, as specified in Annex B.
When non-activated flux is inappropriate, the above flux with the addition of diethylammonium
chloride (analytical reagent grade), up to an amount of 0,2 % chloride (expressed as free
chlorine based on the colophony content), may be used as required by the relevant
specification.
4.2.3 Procedure
The surface of the molten solder shall be wiped clean and bright with a piece of suitable
material immediately before each test.
The termination to be tested shall be immersed first in the flux described in 4.2.2 at laboratory
temperature, and excess flux shall be eliminated either by draining off for a suitable time, or
by using any other procedure likely to produce a similar result. In case of dispute, drainage
shall be carried out for (60 ± 5) s.
NOTE Excessive remaining flux may boil when coming into contact with the liquid solder. Gas bubbles may stick
to the surface of terminations and prevent wetting of the termination in the respective area.
The termination is then immersed immediately in the solder bath in the direction of its
longitudinal axis. The point of immersion of the termination shall be at a distance not less than
10 mm from the walls of the bath.
The speed of immersion shall be (25 ± 2,5) mm/s and the termination shall remain immersed
for the time selected from Table 1 with the body of the component at the distance above the
solder prescribed in the relevant specification. The specimen shall then be withdrawn at
(25 ± 2,5) mm/s.
For components having a high thermal capacity an immersion time of (5,0 ± 0,5) s or
(10 ± 1) s may be selected from Table 1.
If required by the relevant specification, a screen of thermally insulating material of
(1,5 ± 0,5) mm thickness with clearance, holes appropriate to the size of the termination may
be placed between the body of the component and solder.
Any flux residue shall be removed with 2-propanol (isopropanol) or ethyl alcohol.
4.2.4 Test conditions
The duration and temperature of immersion shall be selected from Table 1, unless otherwise
prescribed by the relevant specification.

60068-2-20 © IEC:2008 – 11 –
Table 1 – Solderability, solder bath method: Test severities
(duration and temperature)
Severity
Alloy
(215 ± 3) °C (235 ± 3) °C (245 ± 3) °C (250± 3) °C
composition
(3 ± 0,3) s (10 ± 1) s (2 ± 0,2) s (5 ± 0,5) s (3 ± 0,3) s (3 ± 0,3) s
SnPb X X X X
Sn96,5Ag3Cu,5  X
Sn99,3Cu,7
X
Alloy composition for test purposes only. The solder alloys consist of 3,0 wt % to 4,0 wt % Ag, 0,5 wt % to 1,0 wt %
Cu, and the remainder of Sn may be used instead of Sn96,5Ag3Cu,5. The solder alloys consist of 0,45 wt % to
0,9 wt % Cu and the remainder of Sn may be used instead of Sn99,3Cu,7.
NOTE 1 “X” denotes ‘applicable’.
NOTE 2 Refer to 4.1 of IEC 61190-1-3 to identify alloy composition.
NOTE 3 The basic lead-free solder alloys listed in this table represent compositions that are currently preferred
for lead-free soldering processes. If solder alloys other than those listed here are used, it has to be verified that
the given severities are applicable.

4.2.5 Final measurements and requirements
Inspection shall be carried out under adequate light with normal eyesight or with the assis-
tance of a magnifier capable of giving a magnification of 4 x to 25 x, depending on the size of
objects.
The specimens shall be visually examined and, if required by the relevant specification,
electrically and mechanically checked.
The dipped surface relevant for soldering shall be covered with solder coating with no more
than small amounts of scattered imperfections such as pin-holes or un-wetted or de-wetted
areas. All leads shall exhibit a continuous solder coating free from defects for a minimum of
95 % of the critical area of any individual lead. For solder alloys containing lead, solder shall
be smooth and bright.
4.3 Method 2: Soldering iron at 350 °C
This method provides a procedure for assessing the solderability of terminations in cases
where the solder bath method is impracticable. It applies to lead containing and lead-free
solder alloys.
4.3.1 Description of soldering irons
To keep the bit temperature during test within the specified limits, usage of a temperature
controlled soldering iron is recommended.
Size A
Bit temperature: (350 ± 10) °C
Bit diameter: 8 mm
Exposed length: 32 mm reduced to a wedge shape over a length of approximately
10 mm.
Size B
Bit temperature: (350 ± 10) °C

– 12 – 60068-2-20 © IEC:2008
Bit diameter: 3 mm
Exposed length: 12 mm reduced to a wedge shape over a length of approximately 5 mm.
The bit shall be made of copper, preferably plated with iron, or of erosion-resistant copper
alloy, in accordance with usual practice, and tinned at the test surface.
4.3.2 Solder and flux
A cored solder wire shall be used comprising solder as specified in Table 1 with a core or
cores containing 2,5 % to 3,5 % colophony as specified in Annex B. A visual check shall be
made during the test for the presence of flux.
4.3.3 Procedure
According to the type of component, an iron of either Size A or Size B shall be used as pres-
cribed in the relevant specification.
The nominal diameter of the solder wire to be used with Size A iron is 1,2 mm and 0,8 mm
with Size B iron.
The termination shall be positioned so that the iron can be applied to the test surface in a
horizontal position as in Figure 2.
If mechanical support for the terminations be required while performing this test, such support
shall be of thermally insulating material.

Solder wire: sufficient
to cover test area
Soldering iron bit
Component
Termination
body
IEC  1235/08
Figure 2 – Position of soldering iron
When testing heat-sensitive components, the relevant specification shall specify the distance
of the test area from the component body, or it shall specify the use of a specific heat sink.
The relevant specification may specify different conditions where the geometry of the termina-
tions renders the above procedure impracticable.
Surplus solder which has remained on the test surface of the iron from a previous test shall
be wiped off.
The iron and the solder shall, unless otherwise specified, be applied to the termination for 2 s
to 3 s at the position stated in the relevant specification. During this period of time the iron
shall be kept stationary.
If the relevant specification requires that several terminations of the component shall be
tested, an interval in the order of 5 s to 10 s shall be observed between the applications to the
different terminations of the component to avoid it being overheated.

60068-2-20 © IEC:2008 – 13 –
Any flux residue shall be removed from the terminations with 2-propanol (isopropanol) or with
ethyl alcohol.
4.3.4 Final measurements and requirements
Inspection shall be carried out under adequate light with normal eyesight or with the
assistance of a magnifier capable of giving a magnification of 4 x to 25 x, depending on the
size of objects.
The specimens shall be visually examined and, if required by the relevant specification, elec-
trically and mechanically checked.
The solder shall have wetted the test area and there shall be no droplets.
4.4 Information to be given in the relevant specification
When this test is included in the relevant specification, the following details shall be given as
far as they are applicable.
Subclause
a) Whether degreasing is required 4.1.2
b) Initial measurements 4.1.3
c) Ageing method (if required) 4.1.4
d) Test method 4.2 or 4.3
e) Whether activated flux shall be used 4.2.2
f) Immersion depth, temperature and duration 4.2.3, 4.2.4
g) Whether a thermal screen is to be used 4.2.3
h) Size of soldering iron (A or B) 4.3.1
i) Distance of test area from component body or use of a heat sink 4.3.3
j) Different test conditions, if required by geometry of termination 4.3.3
k) Position of the soldering iron 4.3.3
l) Application time of soldering iron, if not 2 s to 3 s 4.3.3
m) Number of terminations to be tested 4.3.3
n) Final measurements and requirements 4.3.4
o) Type of solder alloy Table 1, 4.3.2

5 Test Tb: Resistance to soldering heat
5.1 Object and general description of the test
5.1.1 Test methods
Test Tb provides two different methods to determine the ability of a specimen to withstand the
heating stresses produced by soldering.
– Method 1: Solder bath
– 14 – 60068-2-20 © IEC:2008
– Method 2: Soldering iron
Method 1 is identical to Test Ta, Method 1, but with different immersion times and
temperatures.
Method 2 is identical to Test Ta, Method 2, but with the iron applied to the test surface for
10 s.
5.1.2 Initial measurements
The specimens shall be visually examined and electrically and mechanically checked as
required by the relevant specification.
5.2 Method 1: Solder bath
5.2.1 Description of the solder bath
The solder bath shall be not less than 40 mm in depth and not less than 300 ml in volume.
The bath shall contain solder as specified in Table 2.
5.2.2 Flux
The flux to be used shall consist of 25 % by weight of colophony in 75 % by weight of
2-propanol (isopropanol) or of ethyl alcohol, as specified in Annex B.
When non-activated flux is inappropriate, the above flux with the addition of diethylammonium
chloride (analytical reagent grade), up to an amount of 0,5 % chloride (expressed as free
chlorine based on the colophony content), may be used as required by the relevant
specification.
When the test forms part of a test sequence and is applied prior to a humidity test, a non-
activated flux comprising 25 % by weight of colophony in 75 % by weight 2-propanol
(isopropanol) or ethyl alcohol shall be used. In this case, the test shall be made on specimens
which have a surface which has satisfactorily passed the solderability Test Ta, Method 1,
within the previous 72 h period.
5.2.3 Procedure
The surface of the molten solder shall be wiped clean and bright by wiping with a piece of
suitable material immediately before each test.
The termination to be tested shall be immersed first in the flux described in 5.2.2 at laboratory
temperature, and then in the solder bath, in the direction of its longitudinal axis. The point of
immersion of the termination shall be at a distance not less than 10 mm from the walls of the
bath.
Immersion of the termination to within 2,0 mm to 2,5 mm from the component or seating
plane, unless otherwise specified in the relevant specification, shall be completed in a time
not exceeding 1 s.
The termination shall remain immersed to the specified depth for one of the durations given in
Table 2, or as prescribed in the relevant specification.
5.2.4 Test conditions
The duration and temperature of immersion shall be selected from Table 2, unless otherwise
prescribed by the relevant specification.

60068-2-20 © IEC:2008 – 15 –
Table 2 – Resistance to soldering heat, solder bath method: Test severities
(duration and temperature)
Severity
Alloy
(235 ± 3) °C (260± 3) °C
composition
(10 ± 1) s (5 ± 0,5) s (10 ± 1) s
X b c
SnPb
X X
a b c
Lead-free alloy X X
NOTE 1 “X” denotes ‘applicable.
NOTE 2 Certain soldering methods may require higher severity of (270± 3) °C for (5 ± 0,5) s or the more
severe condition of (10 ± 1) s. Such conditions should be provided by the detail specification as agreed between
the trading partners.
NOTE 3 Care should be taken, that heat / moisture sensitive devices are handled according to the instructions
of the supplier.
a
Any alloys may be used, provided they are completely liquid at the required temperature.
b
The shorter immersion time of 5 s is mainly intended for heat-sensitive components to be mounted on printed
circuits. A warning should be given to the user that such components should be soldered to the printed
circuit board in less than 4 s.
c
This test severity is also used for the de-wetting test. As an optional test condition (260 ± 5) °C for (30 ± 3) s
is also used.
Unless otherwise prescribed in the relevant specification, a screen of thermally insulating
material of (1,5 ± 0,5) mm thickness, with clearance holes appropriate to the size of the termi-
nation, shall be placed between the body of the component and the molten solder.
When the relevant specification prescribes the use of a heat sink during this test, it shall give
full details of the size and type of heat sink to be used, which should be related to the method
used for production soldering.
5.2.5 De-wetting
The relevant specification shall prescribe whether this test is required.
A total immersion of 10 s is required because de-wetting can occur slowly; this immersion
shall be divided into two periods of 5 s each in order that any rapid de-wetting is not masked
by any subsequent re-wetting.
5.3 Method 2: Soldering iron
5.3.1 Description of soldering iron
As prescribed in 4.3.1.
The relevant specification shall state whether iron A or iron B is to be used.
5.3.2 Solder and flux
As prescribed in 4.3.2.
5.3.3 Procedure
As prescribed in 4.3.3 (Method 2, with the soldering iron of Test Ta), but with the iron applied
to the test surface of the termination for one of the following temperatures and durations, as
prescribed in the relevant specification.

– 16 – 60068-2-20 © IEC:2008
Temperature: 350 °C or 370 °C
Duration: (5 ± 1) s or
(10 ± 1) s
If the relevant specification does not indicate the duration, 10 s shall apply.
NOTE In testing certain types of electromechanical and other heat-sensitive components, prolonged heat stress
may provoke non-repairable defects. The usual soldering times used in practice are in the range of 1 s to 2 s; this
and the heat sensitivity of the component should be considered when selecting the test duration. Additional
precautions (e.g. automatic switching off of the heat source) may be necessary.
For heat-sensitive components, the relevant specification shall specify the distance of the test
area from the component body, or shall specify the use of a specific heat sink.
If the relevant specification requires that several terminations of the component shall be
tested, an interval in the order of 5 s to 10 s shall be observed between the applications to the
different terminations of the component to avoid it being overheated.
5.4 Recovery
The specimen shall remain under standard atmospheric conditions for testing as prescribed in
IEC 60068-1 for a period of 30 min, or until thermally stabilized.
NOTE It may occur with certain components, such as some semiconductors and capacitors, that the electrical
properties are stabilized only some hours after heat stability is reached.
5.5 Final measurements and requirements
Inspection shall be carried out under adequate light with normal eyesight or with the assis-
tance of a magnifier capable of giving a magnification of 4 x to 25 x, depending on the size of
objects.
The specimens shall be visually examined and electrically and mechanically checked,
including dimensional tolerances, as required by the relevant specification.
5.6 De-wetting (if required)
The criteria for wetting described in 4.2.5 shall also apply.
If de-wetting or unwetted areas occur this should be noted.

60068-2-20 © IEC:2008 – 17 –
5.7 Information to be given in the relevant specification
When this test is included in the relevant specification, the following details shall be given as
far as they are applicable:
Subclause
a) Initial measurements 5.1.2
b) Test method to be applied 5.2; 5.3
c) Immersion depth, if different from 2,0 mm to 2,5 mm from the
5.2.3
component
d) Test severity 5.2.4
e) Whether a thermal screen is to be used or not, and details of a
5.2.4
heat sink, if required
f) Whether test de-wetting applies 5.2.5
g) Size (A or B) of soldering iron 5.3.1
h) Distance of the test area from the component body or use of a
5.3.3
specific heat sink
i) Number of terminations to be tested 5.3.3
j) Temperature and duration of the soldering iron test 5.3.3
k) Type of solder alloy in case de-wetting is tested Table 2, 5.3.2
l) Final measurements and requirements 5.5, 5.6

– 18 – 60068-2-20 © IEC:2008
Annex A
(informative)
Example of apparatus for accelerated steam ageing process

Cooling water in
Cooling water out
Clamp to support flask
2 l capacity flask of
borosilicate glass
Beaker spout closes with
loose fitting roll of glass
fibre filter paper
Space for specimens:
height approx. 75 mm
diameter approx. 125 mm
2 l capacity beaker of
borosilicate glass
Specimen support
(porcelain filter disk
raised on glass rods)*
800 cm deionised water
Anti-bumping stones
750 W hotplate with
temperature controller
IEC  1236/08
NOTE Specimens should not be placed under the lowest portion of the cooling flask because of dripping water.
Figure A.1 – Example of apparatus

60068-2-20 © IEC:2008 – 19 –
Annex B
(normative)
Specification for flux constituents

B.1 Colophony
Colour To WW grade or paler
Acid value (mg KOH/g colophony) 155 (minimum)
Softening point (ball and ring) 70 °C (minimum)
Flow point (Ubbelohde) 76 °C (minimum)
Ash 0,05 % (maximum)
Solubility A solution of the colophony in an equal part by
weight of 2-propanol (isopropanol) shall be clear,
and after a week at room temperature there shall
be no sign of a deposit
B.2 2-propanol (isopropanol)
Purity Minimum 99,5 % 2-propanol (isopropanol) by
weight
Acidity as acetic acid Maximum 0,002 % by weight
(other than carbon dioxide)
Non-volatile matter Maximum 2 mg per 100 ml
B.3 Ethyl alcohol
Purity Minimum 96,2 % ethyl alcohol by weight
Free acids Maximum 4 mg/l
(other than carbon dioxide)
NOTE When an activated flux is called for this may be conveniently made up as follows:
Colophony 25 g
2-propanol (isopropanol) or Ethyl
75 g for 0,5 % chloride activation

alcohol
Diethylammonium chloride 0,39 g

– 20 – 60068-2-20 © IEC:2008
Bibliography
IEC 60068-2-54, Environmental testing – Part 2-54: Tests – Test Ta: Solderability testing of
electronic components by the wetting balance method
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 60068-2-69, Environmental testing – Part 2-69: Tests – Test Te: Solderability testing of
electronic components for surface mounting devices (SMD) by the wetting balance method
IEC 61190-1-3:2007, Attachment materials for electronic assembly – Part 1-3: Requirements
for electronic grade solder alloys and fluxed and non-fluxed solid solders for electronic
soldering applications
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