IEC 60749-24:2025

IEC 60749-24 ®
Edition 2.0 2025-11
INTERNATIONAL
STANDARD
REDLINE VERSION
Semiconductor devices - Mechanical and climatic test methods -
Part 24: Accelerated moisture resistance - Unbiased HAST
ICS 31.080.01 ISBN 978-2-8327-0915-3
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright
or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
IEC member National Committee for further information.

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3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

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CONTENTS
FOREWORD . 2
1 Scope and object . 4
2 Normative references . 4
3 Terms and definitions . 4
4 GeneralTest requirements . 4
5 Test apparatus . 5
5.1 Test chamber . 5
5.2 Records . 5
5.3 Devices under stress . 5
5.4 Ionic contamination . 5
5.5 Distilled or deionized water . 5
6 Test conditions . 5
7 Procedure . 6
7.1 Mounting . 6
7.2 Ramp-up . 6
7.3 Ramp-down . 7
7.4 Test clock . 7
7.5 Electrical tests . 7
7.6 Handling . 7
8 Failure criteria . 7
9 Safety . 7
10 Summary . 8
Bibliography . 9

Table 1 – Temperature, relative humidity, and pressure Test conditions for accelerated
moisture resistance testing . 6

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Semiconductor devices - Mechanical and climatic test methods -
Part 24: Accelerated moisture resistance - Unbiased HAST

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) 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 patens, 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.
This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 60749-24:2004. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 60749-24 has been prepared by IEC technical committee 47: Semiconductor devices. It is
an International Standard.
This second edition, cancels and replaces the first edition published in 2004. lt is based on
JEDEC document JESD22-A118B.01. It is used with permission of the copyright holder, JEDEC
Solid State Technology Association. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) rearrangement of clauses to reposition requirements;
b) addition of two notes to the post-test electrical procedures.
The text of this International Standard is based on the following documents:
Draft Report on voting
47/2957/FDIS 47/2974/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.
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 of the IEC 60749 series, under the general title Semiconductor devices –
Mechanical and climatic test methods, can be found in 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.
1 Scope and object
This part of IEC 60749 specifies unbiased highly accelerated stress testing (HAST). HAST is
performed for the purpose of evaluating the reliability of non-hermetically packaged solid-state
devices in humid environments.
It is a highly accelerated test which employs temperature and humidity under non-condensing
conditions to accelerate the penetration of moisture through the external protective material
(encapsulant or seal) or along the interface between the external protective material and the
metallic conductors which pass through it. Bias is not applied in this test to ensure that the
failure mechanisms potentially overshadowed by bias can be uncovered (e.g. galvanic
corrosion).
This test is used to identify failure mechanisms internal to the package and is destructive.
NOTE This test is a complete rewrite of the test contained in Clause 4C of Chapter 3 of IEC 60749 (1996) (without
bias voltage).
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 60749-5, Semiconductor devices - Mechanical and climatic test methods - Part 5: Steady-
state temperature humidity bias life test
IEC 60749-33, Semiconductor devices - Mechanical and climatic test methods - Part 33:
Accelerated moisture resistance - Unbiased autoclave
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– ISO Online browsing platform: available at https://www.iso.org/obp
– IEC Electropedia: available at https://www.electropedia.org
4 GeneralTest requirements
This test method applies primarily to moisture resistance evaluations and robustness testing
and may be used as an alternative to unbiased autoclave.
Samples are subjected to a non-condensing, humid atmosphere, as described in IEC 60749-33,
but with a higher temperature and without bias. For the temperature limits defined by this
procedure, the test will typically generate the same failure mechanisms as those in an unbiased
autoclave "85 °C/85 % RH" steady-state humidity life test, but caution should be exercised if
higher temperatures are considered, since non-realistic failure modes can be generated. In the
case where both this test and that of IEC 60749-33 are performed, the results of this unbiased
HAST test takes precedence over the results of the unbiased autoclave test.
The use of a non-condensing environment avoids many irrelevant external failures, e.g. pin-to-
pin leakage or lead corrosion. However, because absorbed moisture typically decreases glass
transition temperature for most polymeric materials, the combination of high humidity and high
temperature (> T ) may can produce unrealistic material failures. Thus, caution is needed if
g
unbiased HAST is required used for reliability or qualification purposes. The condition of
85 °C/85 % RH is considered equivalent but with less of an acceleration factor. Unbiased HAST
may can show failures that are due to the HAST accelerated conditions. In this case, unbiased
85 °C/85 % RH is considered the reference condition as it correlates better with use conditions.
Test method IEC 60749-5, used without bias, is the reference test method.
5 Test apparatus
5.1 Test chamber
The test requires a chamber capable of maintaining a specified temperature and relative
humidity under pressure during ramp-up to, and ramp-down from, the specified test conditions.
5.2 Records
A permanent record of the temperature profile for each test cycle is recommended. Calibration
records shall verify that the equipment avoids condensation on devices under test (DUTs) hotter
than 50 °C during ramp-up and ramp-down for conditions of maximum thermal mass loading.
Calibration records shall verify that, for steady-state conditions and maximum thermal mass
loading, test conditions are maintained within the tolerances specified in Clause 6.
5.3 Devices under stress
Devices under stress shall be placed in the chamber to minimize temperature gradients.
Devices under stress shall be no closer than 30 mm from internal chamber surfaces and shall
not be subjected to direct radiant heat from heaters. If devices are mounted on boards, the
boards should be oriented to minimize interference with vapor circulation.
5.4 Ionic contamination
Care shall be exercised is needed in the choice of any materials introduced into the chamber
in order to minimize release of contamination and minimize degradation due to corrosion and
other mechanisms. Ionic contamination of the test apparatus shall needs to be controlled to
avoid inducing erroneous failure mechanisms.
5.5 Distilled or deionized water
The supply water shall be distilled or deionized water with a minimum resistivity of 1 × 10 Ωm
(1 MΩ-cm) at room temperature shall be used.
6 Test conditions
Test conditions consist of a given temperature, relative humidity, and duration (see Table 1).
Table 1 – Temperature, relative humidity, and pressure Test conditions for accelerated
moisture resistance testing
c,d a a b b
Test condition Temperature Relative humidity Temperature Vapor pressure
(dry bulb) (wet bulb)
°C % °C kPa
A 130 ± 2 85 ± 5 125 230
B 110 ± 2 85 ± 5 105 122
NOTE Caution is needed if unbiased HAST is required used for reliability or qualification purposes. The condition
of 85 °C/85 % RH is considered equivalent but with less of an acceleration factor. Unbiased HAST may can show
failures that are due to the HAST accelerated conditions. In this case, unbiased 85 °C/85 % RH is considered the
reference condition as it correlates better with use conditions. Test method IEC 60749-5, used without bias, is the

reference test method.
a
Tolerances apply to the entire usable test area.
b
For information only.
c
The test conditions are to shall be applied continuously except during any interim readouts. For interim
readouts, devices should be returned to stress within the time specified in 7.4.
d
The unbiased HAST duration is intended to meet or exceed an equivalent field lifetime under use conditions.
The duration is established based on the acceleration of the stress (see, for example, JEDEC document
JEP122H). The stress duration is specified by appropriate qualification requirements or the relevant
specification. Typical test durations are:
Condition Duration
+2
A 96 h
+2
B 264 h
CAUTIONWARNING: For plastic-encapsulated microcircuits, it is known that moisture
reduces the effective glass transition temperature of the molding moulding compound.
Stress temperatures above the effective glass transition temperature may can lead to
failure mechanisms unrelated to operational use

7 Procedure
7.1 Mounting
The test devices shall be mounted in a manner that exposes them to a specified condition of
temperature and humidity. Exposure of devices to conditions that result in them being exposed
to condensation, particularly during ramp-up and ramp-down, shall be avoided. While devices
are above 30 °C, the relative humidity shall be ≥ 40 % to ensure their moisture content is not
reduced, i.e. inadvertent moisture bake out.
7.2 Ramp-up
The time to reach stable temperature and relative humidity conditions shall be less than 3 h.
Condensation shall be avoided by ensuring that the test chamber (dry bulb) temperature
exceeds the wet-bulb temperature at all times, and that the rate of ramp-up shall not be faster
than a rate which ensures that the temperature of any DUT does not lag below the wet bulb
temperature.
The dry- and wet-bulb temperature set points shall be maintained so that the relative humidity
is not less than 50 % after significant heating begins. In a dry laboratory, the chamber ambient
may can initially be drier than this.
7.3 Ramp-down
The first part of ramp-down to a slightly positive gauge pressure (a wet bulb temperature of
about 104 °C) shall be long enough to avoid test artefacts due to rapid depressurization, but
shall not exceed 3 h.
The second part of ramp-down from a wet bulb temperature of 104 °C to room temperature shall
occur with the chamber vented. There is no time restriction, and forced cooling of the vessel is
permitted.
Condensation on devices shall be avoided in both parts of the ramp-down by ensuring that the
test chamber (dry bulb) temperature exceeds the wet-bulb temperature at all times.
Ramp-down should maintain the moisture content of the molding moulding compound
encapsulating the die. Therefore, the relative humidity shall not be less than 50 % during the
first part of the ramp-down, see above.
7.4 Test clock
The test clock starts when the temperature and relative humidity reach the set points, and stops
at the beginning of ramp-down.
7.5 Electrical tests
Electrical test shall be performed not later than 48 h after the end of ramp-down. For
intermediate read-outs, devices shall be returned to stress within 96 h of the end of ramp-down.
The rate of moisture loss from devices after removal from the chamber can be reduced by
placing the devices in sealed moisture barrier bags, the bags should be non-vacuum sealed
without a nitrogen purge and without desiccant. When devices are placed in sealed bags, the
"test window clock" runs at one-third of the rate of devices exposed to the laboratory ambient.
Thus the 130 °C/85 % RH test window can be extended to as much as 144 h, and the time to
return to stress to as much as 288 h by enclosing the devices in sealed moisture barrier bags.
The electrical test parameters should be chosen to preserve any defect (i.e., by limiting the
applied test current).
Additional time-to-test delay or return-to-stress delay time is allowed if justified by technical
data.
7.6 Handling
Suitable hand-covering shall be used to handle devices, boards and fixtures. Contamination
control is important in any highly accelerated moisture stress test.
8 Failure criteria
A device will be considered to have failed if parametric limits are exceeded, or if functionality
cannot be demonstrated under nominal and worst-case conditions, as specified in the relevant
specification or data sheet. Electrical failures due to external package damage, which are an
artefact of the test method, shall be excluded from the failure classification.
9 Safety
The equipment shall be used in accordance with manufacturer's recommendations safety-
related requirements and relevant local safety laws/regulations shall apply.
10 Summary
The following details shall be specified in the relevant specification:
a) test duration (see Clause 6);
b) test conditions (see Clause 6);
c) measurements after test (see 7.5).

Bibliography
JEDEC document JEP122H, Failure mechanisms and models for semiconductor devices
JEDEC document JESD22-A118B.01, Accelerated Moisture Resistance - Unbiased HAST

___________
IEC 60749-24 ®
Edition 2.0 2025-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices - Mechanical and climatic test methods -
Part 24: Accelerated moisture resistance - Unbiased HAST

Dispositifs à semiconducteurs - Méthodes d'essais mécaniques et climatiques -
Partie 24: Résistance à l'humidité accélérée - HAST sans polarisation
ICS 31.080.01  ISBN 978-2-8327-0862-0

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
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or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
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CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - IEC Products & Services Portal - products.iec.ch
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committee, …). It also gives information on projects, content tailored to your needs.

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once a month by email. Also known as the International Electrotechnical Vocabulary
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CONTENTS
FOREWORD . 2
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Test requirements. 4
5 Test apparatus . 5
5.1 Test chamber . 5
5.2 Records . 5
5.3 Devices under stress . 5
5.4 Ionic contamination . 5
5.5 Distilled or deionized water . 5
6 Test conditions . 5
7 Procedure . 6
7.1 Mounting . 6
7.2 Ramp-up . 6
7.3 Ramp-down . 7
7.4 Test clock . 7
7.5 Electrical tests . 7
7.6 Handling . 7
8 Failure criteria . 7
9 Safety . 7
10 Summary . 8
Bibliography . 9

Table 1 – Test conditions for accelerated moisture resistance testing . 6

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Semiconductor devices - Mechanical and climatic test methods -
Part 24: Accelerated moisture resistance - Unbiased HAST

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) 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 patens, 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 60749-24 has been prepared by IEC technical committee 47: Semiconductor devices. It is
an International Standard.
This second edition, cancels and replaces the first edition published in 2004. lt is based on
JEDEC document JESD22-A118B.01. It is used with permission of the copyright holder, JEDEC
Solid State Technology Association. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) rearrangement of clauses to reposition requirements;
b) addition of two notes to the post-test electrical procedures.
The text of this International Standard is based on the following documents:
Draft Report on voting
47/2957/FDIS 47/2974/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.
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 of the IEC 60749 series, under the general title Semiconductor devices –
Mechanical and climatic test methods, can be found in 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.
1 Scope
This part of IEC 60749 specifies unbiased highly accelerated stress testing (HAST). HAST is
performed for the purpose of evaluating the reliability of non-hermetically packaged solid-state
devices in humid environments.
It is a highly accelerated test which employs temperature and humidity under non-condensing
conditions to accelerate the penetration of moisture through the external protective material
(encapsulant or seal) or along the interface between the external protective material and the
metallic conductors which pass through it. Bias is not applied in this test to ensure that the
failure mechanisms potentially overshadowed by bias can be uncovered (e.g. galvanic
corrosion).
This test is used to identify failure mechanisms internal to the package and is destructive.
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 60749-5, Semiconductor devices - Mechanical and climatic test methods - Part 5: Steady-
state temperature humidity bias life test
IEC 60749-33, Semiconductor devices - Mechanical and climatic test methods - Part 33:
Accelerated moisture resistance - Unbiased autoclave
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– ISO Online browsing platform: available at https://www.iso.org/obp
– IEC Electropedia: available at https://www.electropedia.org
4 Test requirements
This test method applies primarily to moisture resistance evaluations and robustness testing
and may be used as an alternative to unbiased autoclave.
Samples are subjected to a non-condensing, humid atmosphere, as described in IEC 60749-33,
but with a higher temperature and without bias. For the temperature limits defined by this
procedure, the test will typically generate the same failure mechanisms as those in an unbiased
"85 °C/85 % RH" steady-state humidity life test, but caution should be exercised if higher
temperatures are considered, since non-realistic failure modes can be generated. In the case
where both this test and that of IEC 60749-33 are performed, the results of this unbiased HAST
test takes precedence over the results of the unbiased autoclave test.
The use of a non-condensing environment avoids many irrelevant external failures, e.g. pin-to-
pin leakage or lead corrosion. However, because absorbed moisture typically decreases glass
transition temperature for most polymeric materials, the combination of high humidity and high
temperature (> T ) can produce unrealistic material failures. Thus, caution is needed if unbiased
g
HAST is used for reliability or qualification purposes. The condition of 85 °C/85 % RH is
considered equivalent but with less of an acceleration factor. Unbiased HAST can show failures
that are due to the HAST accelerated conditions. In this case, unbiased 85 °C/85 % RH is
considered the reference condition as it correlates better with use conditions. Test method
IEC 60749-5, used without bias, is the reference test method.
5 Test apparatus
5.1 Test chamber
The test requires a chamber capable of maintaining a specified temperature and relative
humidity under pressure during ramp-up to, and ramp-down from, the specified test conditions.
5.2 Records
A permanent record of the temperature profile for each test cycle is recommended. Calibration
records shall verify that the equipment avoids condensation on devices under test (DUTs) hotter
than 50 °C during ramp-up and ramp-down for conditions of maximum thermal mass loading.
Calibration records shall verify that, for steady-state conditions and maximum thermal mass
loading, test conditions are maintained within the tolerances specified in Clause 6.
5.3 Devices under stress
Devices under stress shall be placed in the chamber to minimize temperature gradients.
Devices under stress shall be no closer than 30 mm from internal chamber surfaces and shall
not be subjected to direct radiant heat from heaters. If devices are mounted on boards, the
boards should be oriented to minimize interference with vapor circulation.
5.4 Ionic contamination
Care is needed in the choice of any materials introduced into the chamber in order to minimize
release of contamination and minimize degradation due to corrosion and other mechanisms.
Ionic contamination of the test apparatus needs to be controlled to avoid inducing erroneous
failure mechanisms.
5.5 Distilled or deionized water
The supply water shall be distilled or deionized water with a minimum resistivity of 1 × 10 Ωm
(1 MΩ-cm) at room temperature shall be used.
6 Test conditions
Test conditions consist of a given temperature, relative humidity, and duration (see Table 1).
Table 1 – Test conditions for accelerated moisture resistance testing
c,d a a b b
Test condition Temperature Relative humidity Temperature Vapor pressure
(dry bulb) (wet bulb)
°C % °C kPa
A 130 ± 2 85 ± 5 125 230
B 110 ± 2 85 ± 5 105 122
Caution is needed if unbiased HAST is used for reliability or qualification purposes. The condition of 85 °C/85 % RH
is considered equivalent but with less of an acceleration factor. Unbiased HAST can show failures that are due to
the HAST accelerated conditions. In this case, unbiased 85 °C/85 % RH is considered the reference condition as

it correlates better with use conditions. Test method IEC 60749-5, used without bias, is the reference test method.
a
Tolerances apply to the entire usable test area.
b
For information only.
c
The test conditions shall be applied continuously except during any interim readouts. For interim readouts,
devices should be returned to stress within the time specified in 7.4.
d
The unbiased HAST duration is intended to meet or exceed an equivalent field lifetime under use conditions.
The duration is established based on the acceleration of the stress (see, for example, JEDEC document
JEP122H). The stress duration is specified by appropriate qualification requirements or the rele
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