IEC 60068-2-88:2025

IEC 60068-2-88 ®
Edition 1.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-88: Tests – Test XD: Resistance of components and assemblies to liquid
cleaning media
Essais d’environnement –
Partie 2-88: Essais – Essai XD: Résistance des composants et des assemblages
aux produits de nettoyage liquides
ICS 19.040, 31.190 ISBN 978-2-8327-0441-7

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– 2 – IEC 60068-2-88:2025 © IEC 2025
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Objective and general aspects . 9
4.1 Objective . 9
4.2 General . 9
4.3 Qualification and validation process . 10
5 Test liquids . 10
5.1 Test liquid W – Water based neutral, single phase . 10
5.1.1 Preparation . 10
5.1.2 Formulation . 10
5.1.3 Specification . 11
5.2 Test liquid W – Water based alkaline . 11
5.2.1 Preparation . 11
5.2.2 Formulation . 11
5.2.3 Specification . 11
5.3 Test liquid OR – Petroleum based organic solvent, single phase . 11
5.3.1 Preparation . 11
5.3.2 Formulation . 11
5.3.3 Specification . 12
5.4 Test liquid OR – Glycol based organic solvent . 12
5.4.1 Preparation . 12
5.4.2 Formulation . 12
5.4.3 Specification . 12
5.5 Test liquid D – Deionized water . 12
5.5.1 Preparation . 12
5.5.2 Specification . 12
6 Test apparatus . 13
6.1 Containers . 13
6.2 Miscellaneous laboratory equipment . 13
6.3 Temperature controlled equipment . 13
6.4 Balance . 13
6.5 Thermometer . 13
6.6 pH meter . 13
7 Test XD – Test procedure for components . 13
7.1 Object . 13
7.2 Preconditioning . 13
7.3 Initial measurements . 14
7.3.1 Visual inspection . 14
7.3.2 Electrical and mechanical measurement . 14
7.4 Conditioning . 14
7.4.1 Test conditions and severities . 14
7.4.2 Method 1 – Manual stirring . 15

7.4.3 Method 2 – Automatic stirring . 15
7.5 Recovery . 15
7.6 Final measurements . 16
7.7 Information to be given in the relevant specification . 16
8 Test XD – Test procedure for circuit boards . 16
8.1 Object . 16
8.2 Preconditioning . 16
8.3 Initial measurements . 17
8.3.1 Initial weight . 17
8.3.2 Visual inspection . 17
8.4 Conditioning . 17
8.4.1 Test conditions and severities . 17
8.4.2 Method – Automatic stirring . 18
8.5 Recovery . 18
8.6 Final measurements . 19
8.6.1 Final weight . 19
8.6.2 Final visual inspection . 19
8.6.3 Inspection of the white paper . 19
8.7 Information to be given in the relevant specification . 19
9 Test XD – Test procedure for assemblies . 20
9.1 Object . 20
9.2 Preconditioning . 20
9.2.1 General . 20
9.2.2 Soldering . 20
9.2.3 Preparing of a reference . 20
9.3 Initial measurements . 20
9.3.1 Visual inspection – Microscope . 20
9.3.2 Impedance spectroscopy (optional). 21
9.3.3 Electrical function tests . 21
9.4 Conditioning . 21
9.4.1 Test parameters . 21
9.4.2 Test apparatus . 22
9.4.3 Test procedure . 22
9.5 Recovery . 22
9.6 Final measurements . 22
9.6.1 Final visual inspection . 22
9.6.2 Final impedance spectroscopy (optional) . 23
9.6.3 Final electrical function tests . 23
9.7 Information to be given in the relevant specification . 23
Annex A (normative) Qualification and process validation . 24
A.1 General . 24
A.2 Component and circuit board qualification process. 24
A.3 Cleaning process validation . 24
Annex B (informative) Typical cleaning procedures . 26
B.1 Spray-in-air process (SIA) . 26
B.2 Dip tank process . 27
Annex C (informative) Impedance spectroscopy . 28
C.1 General description . 28

– 4 – IEC 60068-2-88:2025 © IEC 2025
C.2 Measuring system set up . 28
C.3 Selection of measuring parameters . 28
C.4 Interpretation of impedance curves . 28
Bibliography . 31

Figure C.1 – Test board . 29
Figure C.2 – Impedance curves elKo 2 before (a) and after conditioning (b) . 29
Figure C.3 – Impedance curves L1 before (a) and after conditioning (b) . 30

Table 1 – Test liquid W water based neutral . 10
Table 2 – Test liquid W alkaline, single phase . 11
Table 3 – Test liquid OR – Petroleum based organic solvent . 12
Table 4 – Test liquid OR – Glycol based organic solvent . 12
Table 5 – Recommended magnification values. 14
Table 6 – Test XD – Test conditions . 15
Table 7 – Test XD – Recommended magnification values . 17
Table 8 – Test XD – Test conditions . 18
Table 9 – Test XD – Recommended magnification values . 21
Table B.1 – Direct spraying batch process . 26
Table B.2 – Indirect spraying batch process with rotating arms . 26
Table B.3 – Spraying inline process . 27
Table B.4 – Dip tank process parameters . 27

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-88: Tests – Test XD: Resistance of components
and assemblies to liquid cleaning media

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,
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60068-2-88 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
91/2027/FDIS 91/2038/RVD
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.

– 6 – IEC 60068-2-88:2025 © IEC 2025
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/publications.
A list of all parts in the IEC 60068 series, published under the general title Environmental testing,
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 webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
a) Background
Current manufacturing processes preferably do not use cleaning steps for the sake of cost
saving, environmental impacts, and potentially detrimental effects to quality and reliability of
the equipment. But there are situations, where cleaning of components or assemblies becomes
unavoidable, for example when it is necessary to apply protective coatings, or cleaning is
required by specific regulations concerning the end use of the equipment. It is the challenge for
process engineers to select effective cleaning media and processes at one side, and on the
other side to evaluate whether the components and circuit boards exposed to those processes
can withstand it without being damaged or their performance being deteriorated.
b) Current industry standard test methods
Current standards, like IEC 60068-2-45 [1] and some other component standards describe
resistance to solvents tests, but the test liquids used for testing (e.g. alcohols) are not commonly
used in real industrial cleaning processes. In addition, the current resistance to solvent test
methods are immersion tests without any mechanical load to the components or ultrasonic
agitation. The current focus of these tests is mainly on the legibility of marking, etc.
Other standards, like MIL-STD-202 [12], Method 215K, describe very specific qualification
processes and solvents, which again are not common in today’s manufacturing processes of
electronic equipment.
c) To close the gap
It is the intention of this document to close the above-described gap between industrial practice
and existing test methods. The approach used is a combination of basic qualification tests to
perform on component and unpopulated circuit board level, and a validation test to perform on
assembly level, using the real manufacturing processes conditions and media. By this two-step
approach, a pre-selection of components suitable for the intended assembly and cleaning
processes, the evaluation of its resistance against the selected processes, and detection of
material incompatibilities are enabled.
The test liquids specified in this document are representative for solvent families used in
cleaning processes of electronics industry.

___________
Numbers in square brackets refer to the Bibliography.

– 8 – IEC 60068-2-88:2025 © IEC 2025
ENVIRONMENTAL TESTING –
Part 2-88: Tests – Test XD: Resistance of components
and assemblies to liquid cleaning media

1 Scope
This part of IEC 60068-2 establishes test methods for the resistance of electronic and
electromechanical components, unpopulated circuit boards and assemblies to liquid cleaning
media and cleaning processes, which are agreed between user and supplier for applications,
where cleaning is required. These tests are not applicable to components, unpopulated circuit
boards and assemblies, which are not intended to be subjected to cleaning processes.
Tests XD and XD primarily are intended for qualification testing of components and
1 2
unpopulated circuit boards suitable for cleaning processes but can be adopted as well to testing
of material compatibility and specific cleaning media used in manufacturing processes of
components and unpopulated circuit boards.
Test XD is intended to determine the resistance of electronic assemblies suitable for cleaning
processes to the various cleaning processes to which they are exposed during manufacturing,
including the effects of assembly and soldering processes.
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 60068-2-20, Environmental testing – Part 2-20: Tests – Tests Ta and Tb: Test methods for
solderability and resistance to soldering heat of devices with leads
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)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp

3.1
compatibility
interaction between material sets which do not negatively impact the end use product
EXAMPLE Removal of flux while not interacting with the markings required for product use.
[SOURCE: IPC 9505:2017, 1.1]
3.2
incompatibility
interaction between material sets which do negatively impact the end use product
EXAMPLE Removal of protective coatings and critical type markings.
[SOURCE: IPC 9505:2017, 1.1]
3.3
validation
confirmation, through the provision of objective evidence, that the requirements for a specific
intended use or application have been fulfilled
[SOURCE: ISO 9000:2015, 3.8.13, modified – The notes have been removed.]
4 Objective and general aspects
4.1 Objective
The objective of the test methods is to assess the effects of short-term exposure of components
and unpopulated circuit boards to specified liquid cleaning media as they are used typically in
cleaning processes of electronic assemblies. In addition, Annex A describes a qualification
process and the validation of cleaning processes as they are used during manufacturing of
electronic assemblies.
Plastic materials show a different behaviour against liquid cleaning media, even when the liquid
cleaning media are from the same family with similar contents. A component or circuit board
can therefore not generally be regarded as resistant against liquid cleaning media. It can only
be stated as resistant to such liquid cleaning media that it has been tested against.
4.2 General
Testing is performed to ensure resistance of a test specimen to liquids to which it could be
exposed during manufacturing or assembly and is carried out by immersing the test specimen
in a specified test liquid, or group of liquids, for a specified period at a specified temperature.
A separate test specimen shall be used for each test liquid and test condition. Properties are
measured prior to and after exposure to the liquid.
Components and unpopulated circuit boards should be tested under the same conditions and
severities as described in test XD and XD , assuming that at a later stage both will be stressed
1 2
in the same way during the assembly processes.
Components and unpopulated circuit boards shall be tested in as-received condition without
cleaning. The tests described do not differ between components or unpopulated circuit boards,
which can contain flux residues coming from their manufacturing process (e.g. certain inductors
or boards using hot air leveling finishes) and those without flux residues.

– 10 – IEC 60068-2-88:2025 © IEC 2025
WARNING – Intended users of this procedure are cautioned that tests of this nature can involve
the use of certain hazardous material, operations and equipment. In particular, some of the
fluids that can be used are flammable or can constitute health hazards, or both. Test
temperatures should be at least 10 °C below the flashpoint of any fluid being used. Open flame
heat sources should not be used with any organic solvents. Test personnel should consult the
relevant material’s safety data sheets when necessary.
4.3 Qualification and validation process
The qualification of components and unpopulated circuit boards and the validation of resistance
against real cleaning processes shall be performed as specified in Annex A.
For qualification of components and unpopulated circuit boards (tests XD and XD ) it is
1 2
important:
– to test components and unpopulated circuit boards individually to enable inspection from all
sides for any detrimental effects. In assembled stage this would not be possible anymore,
for example underneath components;
– to select appropriate test liquids and conditions under consideration of worst-case
conditions, to which the components and circuit boards later can be exposed in
manufacturing processes of electronic assemblies.
For validation (test XD ) it is important:
– to use the cleaning media and cleaning equipment as used in the manufacturing process;
– to set cleaning process parameters under worst-case conditions;
– to include all cleaning steps into the test sequence.
5 Test liquids
5.1 Test liquid W – Water based neutral, single phase
5.1.1 Preparation
Mix deionized water, organic solvent and surfactant and mix for 5 min. Wait 30 min to allow the
test liquid to stabilize before checking pH value and visual appearance.
5.1.2 Formulation
The composition of the test liquid is described in Table 1.
Table 1 – Test liquid W water based neutral
Composition Material Mass fraction
[%]
Organic solvent Dipropylene glycol monomethyl ether (CAS 34590-94-8) 24
C10 – C18 fatty alcohol with (8 – 15) EO 1
Non-ionic surfactant
Water Deionized, conductivity ≤ 20 μS/cm 75

___________
The following trade names are examples of suitable products available commercially. This information is given
for the convenience of users of this document and does not constitute an endorsement by IEC of these products:
Greenbentin DE 080, BIO-SOFT N91-8, Lutensol ON 80, Tergitol 15-S-12.

5.1.3 Specification
The pH value of the mixture should be checked by use of a simple method (e.g. indicator paper);
typical values are in the range between 5 to 8.
Visual appearance target: Clear and transparent, colourless to yellow.
5.2 Test liquid W – Water based alkaline
5.2.1 Preparation
Mix deionized water and organic solvent and surfactant and mix for 5 min. Add alkanolamine
and corrosion inhibitor and stir till both compounds are solubilized. Wait 30 min to allow the test
liquid to stabilize before checking pH value and visual appearance.
5.2.2 Formulation
The composition of the test liquid is described in Table 2.
Table 2 – Test liquid W alkaline, single phase
Composition Material Mass fraction
[%]
Organic solvent Dipropylene glycol monomethyl ether (CAS 34590-94-8) 23,4
C10 – C18 fatty alcohol with (8 – 15) EO 1
Non-ionic surfactant
Corrosion inhibitor Sodium metasilicate pentahydrate 0,1
Alkanolamine 2-Aminoethan-1-ol 0,5
Water Deionized, conductivity ≤ 20 µS/cm 75

5.2.3 Specification
The pH value of the mixture should be checked by use of a simple method (e.g., indicator paper);
typical values are in the range between 10 to 13.
Visual appearance target: Clear and transparent, colourless to yellow.
5.3 Test liquid OR – Petroleum based organic solvent, single phase
5.3.1 Preparation
Use solvent as received.
5.3.2 Formulation
The composition of the test liquid is described in Table 3.
___________
The following trade names are examples of suitable products available commercially. This information is given
for the convenience of users of this document and does not constitute an endorsement by IEC of these products:
Greenbentin DE 080, BIO-SOFT N91-8, Lutensol ON 80, Tergitol 15-S-12.

– 12 – IEC 60068-2-88:2025 © IEC 2025
Table 3 – Test liquid OR – Petroleum based organic solvent
Composition Material Mass fraction
[%]
4 a
Organic solvent 100
Distillates petroleum, hydrotreated light (CAS 64742-47-8)
a
Alternative products with comparable composition (mixture of hydrocarbons in the range of C9 through C16)
and a flash point ≥ 93 °C may be used. In this case the test liquid shall be informed in the test report.

5.3.3 Specification
Visual appearance target: Clear and transparent, colourless to yellow.
5.4 Test liquid OR – Glycol based organic solvent
5.4.1 Preparation
Mix organic solvents for 5 min.
5.4.2 Formulation
The composition of the test liquid is described in Table 4.
Table 4 – Test liquid OR – Glycol based organic solvent
Composition Material Mass fraction
[%]
Organic solvent 1 Diethylene glycol monohexyl ether (CAS 112-59-4) 70
Organic solvent 2 Dipropylene glycol monomethyl ether (CAS 34590-94-8) 30

5.4.3 Specification
Visual appearance target: Clear and transparent, colourless to yellow.
5.5 Test liquid D – Deionized water
5.5.1 Preparation
Use solvent as received.
5.5.2 Specification
Conductivity ≤ 20 µS/cm
Visual appearance clear colourless
___________
The following trade names are examples of suitable products available commercially. This information is given
for the convenience of users of this document and does not constitute an endorsement by IEC of these products:
Shellsol D 100/D 110 or Cobersol H 105.

6 Test apparatus
6.1 Containers
A boro-silicate glass or stainless steel vessel of suitable volume for each test liquid shall be
used. Vessels shall be of sufficient size and capacity to permit the test specimens to be
immersed until they are fully covered in the selected liquid without violating other physical
constraints (e.g. touching one another).
6.2 Miscellaneous laboratory equipment
Beaker, spatula, pipette, magnetic stirrer, basket and holder for boards and components, white
absorptive paper.
6.3 Temperature controlled equipment
Hot plate capable for heating up to 100 °C.
Circulating air oven.
6.4 Balance
Analytical balance with a resolution of 0,001 g suitable for masses up to 200 g (for test XD ).
Balance with a resolution of 0,1 g to 1 g (for test XD ).
6.5 Thermometer
Capable of measuring temperatures up to 100 °C with a resolution of 0,1 °C.
6.6 pH meter
Suitable pH meter or pH strips (indicator).
7 Test XD – Test procedure for components
7.1 Object
This test is used to determine the resistance of components suitable for cleaning processes to
liquid cleaning media. The test specimen can be assembled onto a test board or other suitable
fixture, especially in case electrical measurement is necessary.
In case specific cleaning media are required the test should be separately agreed upon between
the user and supplier or alternatively test XD shall be applied by the user.
7.2 Preconditioning
The components shall be kept at room temperature for a time sufficient to adopt to the room
temperature.
Coatings and varnishes shall be completely cured.
In case it is necessary for the test specimen to be soldered to test coupons, the soldering
conditions and solders to be used shall be specified in the component specification, preferably
in accordance with the requirements set forth for the resistance to soldering heat tests in
IEC 60068-2-20 and IEC 60068-2-58 as the preconditioning under worst-case conditions.

– 14 – IEC 60068-2-88:2025 © IEC 2025
If it is necessary to identify single components, for example for comparison between initial and
tested stage, the test specimen shall be marked by use of suitable means, which can withstand
the test procedure without impacting the result.
7.3 Initial measurements
7.3.1 Visual inspection
Visual inspection shall be carried out under adequate light with a binocular microscope of
magnification in a range of 4x to 100x. The test specimen shall comply to the criteria given in
the component specification.
Table 5 contains recommended magnification values related to the size of components.
The test specimen shall comply with the criteria given in the component specification.
Table 5 – Recommended magnification values
Component length Magnification
mm
> 5 4x to 10x
0,25 to ≤ 5 10x to 40x
< 0.25 40x to 100x
7.3.2 Electrical and mechanical measurement
Electrical and mechanical measurement shall be performed as given in the component
specification.
Usually, a measurement result shall be assignable to the test specimen. In case many
specimens are tested simultaneously, an appropriate statistical method may be applied instead.
7.4 Conditioning
7.4.1 Test conditions and severities
Unless otherwise stated in the relevant specification for Method 1 (see 7.4.2) or Method 2
(see 7.4.3) at least five components shall be tested. If the specimens are assembled to test
coupons, testing of at least one coupon is sufficient.
For every test fresh test liquids shall be used.
For qualification purpose the tests shall be performed with test liquid W , W , OR , OR and D.
1 2 1 2
For each test liquid separate samples shall be used.
The test conditions are given in Table 6.
A test duration of 120 min is the recommended condition. Components passing that condition
are robust against the most common cleaning conditions, even under consideration of repeated
cleaning processes.
Components not passing that condition shall then be tested with a duration of 20 min or another
duration as agreed between user and supplier. In this case test XD should be added to assess
the suitability for cleaning under real manufacturing conditions.

A test duration of 20 min is the minimum condition to be used for sensitive components. This
condition can be applied for example to components consisting of materials, which are
susceptible against the cleaning media, or for labels or markings, where the high robustness
against cleaning is not required. These limitations shall be noted in the component specification.
Components not passing the 20 min test condition are not suitable for cleaning.
– Test conditions
Table 6 – Test XD
Test liquid Temperature Duration
°C min
W , W , D 55 ± 5 20 ± 2
1 2
55 ± 5 120 ± 5
OR , OR 23 ± 5 20 ± 2
1 2
120 ± 5
55 ± 5 20 ± 2
120 ± 5
After conditioning residues of the test liquids can be removed by rinsing with distilled water (test
liquids W and W ) or ethanol (test liquids OR and OR ).
1 2 1 2
7.4.2 Method 1 – Manual stirring
Choose a container of appropriated size. Fill test liquid in the container, so that the components
are covered with at least 10 mm of the liquid. Place the test specimen in it, if necessary, by use
of a suitable holder or basket to ensure that the components do not touch each other.
Heat up the liquid until the test temperature is achieved and stable. Gently stir it with a spatula.
The specimens shall be conditioned in accordance with the conditions in Table 6.
7.4.3 Method 2 – Automatic stirring
Choose a container of appropriated size. Fill test liquid in the container, so that the component
is covered with at least 10 mm of the liquid. Place the test specimen in it, if necessary by use
of a suitable holder or basket. Place the beaker on a magnetic stirrer.
Heat up the liquid until the test temperature is achieved and stable.
The specimens shall be conditioned in accordance with the conditions in Table 6.
7.5 Recovery
Rinsing may be added as an optional method to remove residues of the test liquids before final
measurements, or in case the test is part of a test sequence.
The samples shall be dried at room temperature, for example by blowing with air.

– 16 – IEC 60068-2-88:2025 © IEC 2025
7.6 Final measurements
After subjection to the test, the specimen shall be visually inspected for cracks, separations,
crazing, and degradation of body. Material, labels and markings shall be readable, and end
caps and seals if present, or any other damage or degradation that has occurred due to solvent
exposure and which affects the mechanical integrity or reliability shall constitute a failure. If it
is required that th
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