EN IEC 60749-20-1:2026

SLOVENSKI STANDARD
01-maj-2026
Nadomešča:
SIST EN 60749-20-1:2009
Polprevodniški elementi - Mehanske in klimatske preskusne metode - 20-1. del:
Obdelava, pakiranje, označevanje in pošiljanje elementov za površinsko montažo
(SMD), občutljivih na učinkovanje vlage in spajkalne vročine (IEC 60749-20-1:2019)
Semiconductor devices - Mechanical and climatic test methods - Part 20-1: Handling,
packing, labelling and shipping of surface-mount devices sensitive to the combined effect
of moisture and soldering heat (IEC 60749-20-1:2019)
Halbleiterbauelemente - Mechanische und klimatische Prüfverfahren - Teil 20-1:
Handhabung, Verpackung, Kennzeichnung und Transport oberflächenmontierbarer
Bauelemente, die empfindlich gegen die Kombination von Feuchte und Lötwärme sind
(IEC 60749-20-1:2019)
Dispositifs à semi-conducteurs - Méthodes d'essais mécaniques et climatiques - Partie
20-1: Manipulation, emballage, étiquetage et transport des composants pour montage en
surface sensibles à l'effet combiné de l'humidité et de la chaleur de brasage (IEC 60749-
20-1:2019)
Ta slovenski standard je istoveten z: EN IEC 60749-20-1:2026
ICS:
19.020 Preskuševalni pogoji in Test conditions and
postopki na splošno procedures in general
31.080.01 Polprevodniški elementi Semiconductor devices in
(naprave) na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60749-20-1

NORME EUROPÉENNE
EUROPÄISCHE NORM February 2026
ICS 31.080.01 Supersedes EN 60749-20-1:2009
English Version
Semiconductor devices - Mechanical and climatic test methods -
Part 20-1: Handling, packing, labelling and shipping of surface-
mount devices sensitive to the combined effect of moisture and
soldering heat
(IEC 60749-20-1:2019)
Dispositifs à semiconducteurs - Méthodes d'essais Halbleiterbauelemente - Mechanische und klimatische
mécaniques et climatiques - Partie 20-1: Manipulation, Prüfverfahren - Teil 20-1: Handhabung, Verpackung,
emballage, étiquetage et transport des composants pour Kennzeichnung und Transport oberflächenmontierbarer
montage en surface sensibles à l'effet combiné de Bauelemente, die empfindlich gegen die Kombination von
l'humidité et de la chaleur de brasage Feuchte und Lötwärme sind
(IEC 60749-20-1:2019) (IEC 60749-20-1:2019)
This European Standard was approved by CENELEC on 2026-02-09. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60749-20-1:2026 E

European foreword
This document (EN IEC 60749-20-1:2026) consists of the text of IEC 60749-20-1:2019 prepared by
IEC/TC 47 "Semiconductor devices".
The following dates are fixed:
• latest date by which this document has to be (dop) 2027-02-28
implemented at national level by publication of an
identical national standard or by endorsement
• latest date by which the national standards conflicting (dow) 2029-02-28
with this document have to be withdrawn
This document supersedes EN 60749-20-1:2009 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN-CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN and CENELEC
websites.
Endorsement notice
The text of the International Standard IEC 60749-20-1:2019 was approved by CEN-CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60749-37 NOTE Approved as EN IEC 60749-37
IEC 60749-39 NOTE Approved as EN IEC 60749-39
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60749-20 - Semiconductor devices - Mechanical and EN IEC 60749-20 -
climatic test methods - Part 20: Resistance of
plastic encapsulated SMDs to the combined
effect of moisture and soldering heat
IEC 60749-30 - Semiconductor devices - Mechanical and EN IEC 60749-30 -
climatic test methods - Part 30: Preconditioning
of non-hermetic surface mount devices prior to
reliability testing
IEC 60749-20-1 ®
Edition 2.0 2019-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Mechanical and climatic test methods –

Part 20-1: Handling, packing, labelling and shipping of surface-mount devices

sensitive to the combined effect of moisture and soldering heat

Dispositifs à semiconducteurs – Méthodes d'essais mécaniques et climatiques –

Partie 20-1: Manipulation, emballage, étiquetage et transport des composants

pour montage en surface sensibles à l'effet combiné de l'humidité et de la

chaleur de brasage
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.01 ISBN 978-2-8322-7043-1

– 2 – IEC 60749-20-1:2019 © IEC:2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 General applicability and reliability considerations . 10
4.1 Assembly processes . 10
4.1.1 Mass reflow . 10
4.1.2 Localized heating. 10
4.1.3 Socketed components . 10
4.1.4 Point-to-point soldering . 10
4.1.5 Aqueous cleaning . 11
4.2 Reliability . 11
5 Dry packing . 11
5.1 Requirements . 11
5.2 Drying of SMDs and carrier materials before being sealed in MBBs . 11
5.2.1 Drying requirements – level A2 . 11
5.2.2 Drying requirements – levels B2a to B5a . 12
5.2.3 Drying requirements – carrier materials . 12
5.2.4 Drying requirements – other . 12
5.2.5 Excess time between bake and bag . 12
5.3 Dry pack . 12
5.3.1 Description . 12
5.3.2 Materials . 13
5.3.3 Labels . 16
5.3.4 Moisture barrier bag sealing . 16
5.3.5 Dry pack precautions . 16
5.3.6 Shelf life . 16
6 Drying. 17
6.1 Drying options . 17
6.2 Post exposure to factory ambient . 20
6.2.1 Floor life clock . 20
6.2.2 Any duration exposure . 20
6.2.3 Short duration exposure . 20
6.3 General considerations for baking . 20
6.3.1 High-temperature carriers . 20
6.3.2 Low-temperature carriers . 20
6.3.3 Paper and plastic container items . 21
6.3.4 Bakeout times . 21
6.3.5 ESD protection . 21
6.3.6 Reuse of carriers . 21
6.3.7 Solderability limitations . 21
7 Use . 21
7.1 Floor life clock start . 21
7.2 Incoming bag inspection . 21

IEC 60749-20-1:2019 © IEC:2019 – 3 –
7.2.1 Upon receipt . 21
7.2.2 Component inspection . 22
7.3 Floor life . 22
7.4 Safe storage . 22
7.4.1 Safe storage categories . 22
7.4.2 Dry pack . 22
7.4.3 Shelf life . 22
7.4.4 Dry atmosphere cabinet . 22
7.5 Reflow . 23
7.5.1 Reflow categories . 23
7.5.2 Opened MBB . 23
7.5.3 Reflow temperature extremes . 23
7.5.4 Additional thermal profile parameters. 23
7.5.5 Multiple reflow passes . 23
7.5.6 Maximum reflow passes . 24
7.6 Drying indicators . 24
7.6.1 Drying requirements . 24
7.6.2 Excess humidity in the dry pack . 24
7.6.3 Floor life or ambient temperature/humidity exceeded . 25
7.6.4 Level B6 SMDs . 25
Annex A (normative) Symbol and labels for moisture-sensitive devices . 26
A.1 Object . 26
A.2 Symbol and labels. 26
A.2.1 Moisture-sensitive symbol . 26
A.2.2 Moisture-sensitive identification (MSID) label . 26
A.2.3 Moisture-sensitive caution labels . 26
Annex B (informative) Board rework . 30
B.1 Component removal, rework and remount . 30
B.1.1 Removal precautions . 30
B.1.2 Removal for failure analysis . 30
B.1.3 Removal and remount . 30
B.2 Baking of populated boards. 30
Annex C (normative) Test method for Humidity Indicator Card used with electronic
component packaging . 31
C.1 HIC testing method . 31
C.2 Testing apparatus . 31
C.3 Testing procedure . 31
C.4 Data analysis . 32
Annex D (informative) Derivation of bake tables . 33
Annex E (informative) Derating due to factory environmental conditions . 35
Bibliography . 39

Figure 1 – Typical dry pack configuration for moisture-sensitive SMDs in shipping
tubes . 12
Figure 2 – Example humidity indicator cards . 15
Figure A.1 – Moisture-sensitive symbol (example) . 26
Figure A.2 – MSID label (example) . 26
Figure A.3 – Information label for level A1 or B1 (example) . 27

– 4 – IEC 60749-20-1:2019 © IEC:2019
Figure A.4 – Moisture-sensitive caution label for level A2 (example) . 27
Figure A.5 – Moisture-sensitive caution label for levels B2-B5a (example) . 28
Figure A.6 – Moisture-sensitive caution label for level B6 (example) . 29
Figure D.1 –Typical moisture concentration over time . 33

Table 1 – Dry packing requirements . 11
Table 2 –Typical HIC spot compliance . 15
Table 3 – Reference conditions for drying mounted or unmounted SMDs (user bake:
floor life begins counting at time = 0 after bake) – Level 2. 17
Table 4 – Reference conditions for drying mounted or unmounted SMDs (user bake:
floor life begins counting at time = 0 after bake) – Levels B2, B2a to B5a . 18
Table 5 – Default baking times used prior to dry-pack that were exposed to conditions
≤60 % RH (supplier bake: MET = 24 h) . 19
Table 6 – Resetting or pausing the ‘floor life’ clock at user site . 19
Table 7 – Moisture classification level and floor life . 22
Table C.1 – HIC spot compliance: . 31
Table E.1 – Recommended equivalent total floor life (days) for level A2 at 20 °C, 25 °C,
30 °C and 35 °C for ICs with novolac, biphenyl and multifunctional epoxies (reflow at
same temperature at which component was classified) . 36
Table E.2 – Recommended equivalent total floor life (days) for levels B2a to B5a at
20 °C, 25 °C, 30 °C and 35 °C for ICs with novolac, biphenyl and multifunctional
epoxies (reflow at same temperature at which component was classified) . 37

IEC 60749-20-1:2019 © IEC:2019 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
MECHANICAL AND CLIMATIC TEST METHODS –

Part 20-1: Handling, packing, labelling and shipping of surface-mount
devices sensitive to the combined effect of moisture and soldering heat

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,
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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 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.
This second edition cancels and replaces the first edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updates to subclauses to better align the test method with IPC/JEDEC J-STD-033C,
including new sections on aqueous cleaning and dry pack precautions;
b) addition of two annexes on colorimetric testing of HIC (humidity indicator card) and
derivation of bake tables.
– 6 – IEC 60749-20-1:2019 © IEC:2019
The text of this standard is based on the following documents:
FDIS Report on voting
47/2565/FDIS 47/2579/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60749 series, published under the general title Semiconductor
devices – Mechanical and climatic test methods, 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.
IEC 60749-20-1:2019 © IEC:2019 – 7 –
INTRODUCTION
The advent of surface-mount devices (SMDs) introduced a new class of quality and reliability
concerns regarding package damage "cracks and delamination" from the solder reflow
process. This document describes the standardized levels of floor life exposure for
moisture/reflow-sensitive SMDs along with the handling, packing and shipping requirements
necessary to avoid moisture/reflow-related failures. IEC 60749-20 defines the classification
procedure and Annex A of this document defines the labelling requirements.
Moisture from atmospheric humidity enters permeable packaging materials by diffusion.
Assembly processes used to solder SMDs to printed circuit boards (PCBs) expose the entire
package body to temperatures higher than 200 °C. During solder reflow, the combination of
rapid moisture expansion, materials mismatch, and material interface degradation can result
in package cracking and/or delamination of critical interfaces within the package.
Typical solder reflow processes of concern for all devices are infrared (IR), convection/IR,
convection, vapour phase reflow (VPR), hot air rework tools, and wave solder, including full
immersion.
Non-semiconductor devices can exhibit additional process sensitivities beyond moisture
sensitivity such as thermal sensitivity, flux sensitivity, or cleaning process sensitivity.

– 8 – IEC 60749-20-1:2019 © IEC:2019
SEMICONDUCTOR DEVICES –
MECHANICAL AND CLIMATIC TEST METHODS –

Part 20-1: Handling, packing, labelling and shipping of surface-mount
devices sensitive to the combined effect of moisture and soldering heat

1 Scope
This part of IEC 60749 applies to all devices subjected to bulk solder reflow processes during
PCB assembly, including plastic encapsulated packages, process sensitive devices, and other
moisture-sensitive devices made with moisture-permeable materials (epoxies, silicones, etc.)
that are exposed to the ambient air.
The purpose of this document is to provide SMD manufacturers and users with standardized
methods for handling, packing, shipping, and use of moisture/reflow sensitive SMDs that have
been classified to the levels defined in IEC 60749-20. These methods are provided to avoid
damage from moisture absorption and exposure to solder reflow temperatures that can result
in yield and reliability degradation. By using these procedures, safe and damage-free reflow
can be achieved, with the dry packing process, providing a minimum shelf life capability in
sealed dry-bags from the seal date.
Two test conditions, method A and method B, are specified in the soldering heat test of
IEC 60749-20. For method A, moisture soak conditions are specified on the assumption that
moisture content inside the moisture barrier bag is less than 30 % RH. For method B,
moisture soaking conditions are specified on the assumption that manufacturer’s exposure
time (MET) does not exceed 24 h and the moisture content inside the moisture barrier bag is
less than 10 % RH. In an actual handling environment, SMDs tested by method A are
permitted to absorb moisture up to 30 % RH, and SMDs tested by method B are permitted to
absorb moisture up to 10 % RH. This document specifies the handling conditions for SMDs
subjected to the above test conditions.
NOTE Hermetic SMD packages are not moisture sensitive and do not require moisture precautionary handling.
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 60749-20, Semiconductor devices – Mechanical and climatic test methods – Part 20:
Resistance of plastic-encapsulated SMDs to the combined effect of moisture and soldering
heat
IEC 60749-30, Semiconductor devices – Mechanical and climatic test methods – Part 30:
Preconditioning of non-hermetic surface mount devices prior to reliability testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
IEC 60749-20-1:2019 © IEC:2019 – 9 –
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
active desiccant
desiccant that is either fresh (new) or has been baked according to the manufacturer’s
recommendations to renew it to original specifications
3.2
bar code label
label that gives information in a code consisting of parallel bars and spaces, each of various
specific widths
Note 1 to entry: For the purposes of this document, the bar code label is on the lowest level shipping container
and includes information that describes the product, e.g. part number, quantity, lot information, supplier
identification, moisture-sensitivity level.
3.3
mass reflow
reflow of a number of components with simultaneous attachment by an infrared (IR),
convection/IR, convection, or vapour phase reflow (VPR) process
3.4
carrier
container that directly holds components such as a tray, tube, or tape and reel
3.5
desiccant
absorbent material used to maintain a low relative humidity
3.6
floor life
allowable time period for a moisture-sensitive device, after removal from a moisture barrier
bag, dry storage or dry bake and before the solder reflow process
3.7
humidity indicator card
HIC
card printed with a moisture-sensitive chemical (cobalt bromide) that changes from blue to
pink in the presence of water vapour
Note 1 to entry: The HIC is packed inside the moisture-barrier bag, along with a desiccant, to aid in determining
the level of moisture to which the moisture-sensitive devices have been subjected.
Note 2 to entry: This note applies to the French language only.
3.8
manufacturer’s exposure time
MET
maximum time after bake that the component manufacturer requires to process components
prior to bag seal, and that also includes the maximum time allowed at the distributor for
having the bag open to split out smaller shipments
Note 1 to entry: This note applies to the French language only.
3.9
moisture barrier bag
MBB
storage bag manufactured with a flexible laminated vapour barrier film that restricts the
transmission of water vapour
– 10 – IEC 60749-20-1:2019 © IEC:2019
Note 1 to entry: This note applies to the French language only.
3.10
rework
removal of a component for scrap, reuse, or failure analysis; replacement of an attached
component; or heating and repositioning of a previously attached component
3.11
shelf-life
maximum storage period for a dry-packed moisture-sensitive device in an unopened moisture
barrier bag (MBB) to avoid exceeding the specified interior bag ambient humidity
3.12
surface-mount device
SMD
plastic-encapsulated surface-mount devices made with moisture-permeable materials
Note 1 to entry: For the purposes of this document, the term "SMD" is limited as indicated in the above definition.
3.13
solder reflow
solder attachment process in which previously applied solder or solder paste is melted to
attach a component to the printed circuit board
3.14
water vapour transmission rate
WVTR
measure of the permeability of plastic film or metallized plastic film material to moisture
4 General applicability and reliability considerations
4.1 Assembly processes
4.1.1 Mass reflow
This document applies to mass solder reflow assembly by convection, convection/IR, infrared
(IR), and vapour phase (VPR), processes. It does not apply to mass solder reflow processes
that immerse the component bodies in molten solder (e.g. wave soldering bottom mounted
components). Such processes are not allowed for many SMDs and are not covered by the
component qualifications standards used as a basis for this document.
4.1.2 Localized heating
This document also applies to moisture-sensitive SMDs that are removed or attached singly
by local ambient heating, i.e. "hot air rework". See Annex B.
4.1.3 Socketed components
This document does not apply to SMDs that are socketed and not exposed to solder reflow
temperatures. Such SMDs are not at risk and do not require moisture precautionary handling.
4.1.4 Point-to-point soldering
This document does not apply to SMDs in which only the leads are heated to reflow the solder,
e.g. hand-soldering, hot bar attach of gull-wing leads, and through hole by wave soldering.
The heat absorbed by the SMD body from such operations is typically much lower than that
for mass surface mount reflow or hot air rework, and moisture precautionary measures are
typically not needed.
IEC 60749-20-1:2019 © IEC:2019 – 11 –
4.1.5 Aqueous cleaning
For non-cavity SMDs, typical short-term aqueous cleaning processes will not impact the floor
life (internal moisture content). Special consideration should be given to non-hermetic cavity
packages.
4.2 Reliability
The methods set forth in this specification ensure that an adequate SMD reliability can be
achieved during and after the PCB assembly operation, when the SMDs are evaluated and
verified by IEC 60749-20 and/or by IEC 60749-30, together with environmental reliability
testing.
This specification does not address or ensure solder joint reliability of attached components.
5 Dry packing
5.1 Requirements
Dry packing requirements for the various moisture sensitivity levels are shown in Table 1. The
levels are determined in accordance with IEC 60749-20 and/or IEC 60749-30, together with
reliability testing. As a minimum, all materials used in dry packing should conform to relevant
national packaging material standards for ESD-sensitive items.
Table 1 – Dry packing requirements
a
Level Dry before MBB Desiccant MSID label Caution label
bag
A1 or B1 Optional Optional Optional Not required Not required if classified at
220 °C to 225 °C
b
Required if classified at other
than 220 °C to 225 °C
A2 or B2 Optional Required Required Required Required
B2a-B5a Required Required Required Required Required
B6 Optional Optional Optional Required Required
a
MSID = moisture-sensitive identification label.
b
A "Caution" label is not required if level and reflow temperature are given, in human readable form, on the
barcode label attached to the lowest level shipping container.

5.2 Drying of SMDs and carrier materials before being sealed in MBBs
5.2.1 Drying requirements – level A2
Packing of the SMDs classified as Level A2 into MBBs shall be carried out within one week
under the environmental condition below 30 °C/60 % RH after moulding, burn-in, or bake.
MET is not specified for Level A2 SMDs.
MBBs may be opened for a short period of time (less than 1 h) and re-closed provided that
the HIC indicates a humidity of less than 30 % RH and provided that the desiccant is replaced
with fresh desiccant. When the MBB is next opened, as long as the HIC indicates below
30 % RH, the duration time of the previous MBB’s opening may be disregarded. Thus, if the
HIC indicates below 30 % RH when MBB is opened, the floor life is not dependent on the
duration time of the MBB's opening, and is 168 h at 30 °C/70 % RH.

– 12 – IEC 60749-20-1:2019 © IEC:2019
5.2.2 Drying requirements – levels B2a to B5a
SMDs classified from Levels B2a through to B5a shall be dried (see Clause 6) prior to being
sealed in MBBs. The period between drying and sealing shall not exceed the MET less the
time allowed for distributors to open the bags and repack parts. If the supplier’s actual MET is
more than the default 24 h, then the actual time shall be used. If the distributor practice is to
repack the MBBs with active desiccant, then this time does not need to be subtracted from the
MET.
5.2.3 Drying requirements – carrier materials
The materials from which carriers (such as trays, tubes, reels) are made can affect the
moisture level when placed in the MBB. Therefore, the effect of these materials shall be
compensated for by baking or, if required, adding additional desiccant in the MBB to ensure
the shelf life of the SMDs (see 6.3).
5.2.4 Drying requirements – other
Suppliers may use the drying effect of normal in-line processes such as post-mould cure,
marking cure, and burn-in to reduce the bake time. An equivalency evaluation is
recommended to ensure that high-temperature processing maintains moisture weight gain to
an acceptable level. The total weight gain for the SMD at the time it is sealed in the MBB shall
not exceed the moisture gain of that SMD starting dry and then being exposed to
30 °C/60 % RH for MET h (less the time for distributors).
5.2.5 Excess time between bake and bag
If the allowable time between bake and bag is exceeded, the SMDs shall be redried in
accordance with Clause 6.
5.3 Dry pack
5.3.1 Description
A dry pack consists of desiccant material and a humidity indicator card (HIC) sealed with the
SMDs and their carriers inside a moisture barrier bag (MBB). A representative dry pack
configuration is shown in Figure 1.

Figure 1 – Typical dry pack configuration for moisture-sensitive
SMDs in shipping tubes
IEC 60749-20-1:2019 © IEC:2019 – 13 –
5.3.2 Materials
5.3.2.1 Moisture barrier bag (MBB)
The moisture barrier bag shall meet relevant national standard requirements for flexibility,
ESD protection, mechanical strength, and puncture resistance. The bags shall be heat-
sealable. The water vapour transmission rate (WVTR) shall be ≤ 0,03 g/m in 24 h at 40 °C
after flex testing in accordance with relevant national standards governing flex durability of
flexible barrier materials. The WVTR is measured using relevant national standards governing
water vapour transmission rate through plastic film and sheeting using a modulated infrared
sensor.
5.3.2.2 Desiccant
The desiccant material shall comply with relevant national standards governing activated
desiccants used for the static dehumidification of packaging bags. Desiccant shall be dustless,
non-corrosive, and absorbent to amounts specified in the standard. The desiccant shall be
packaged in moisture-permeable bags. The amount of desiccant used, per moisture barrier
bag, shall be based on the bag surface area and WVTR in order to maintain an interior
relative humidity in the MBB of less than 30 % at 25 °C for SMD classification A2 and less
than 10 % at 25 °C for SMDs classified from Levels B2a to B5a.
For comparison between various desiccant types, certain specifications adopted the "UNIT"
as the basic unit of measure of quantity for desiccant material. A UNIT of desiccant is defined
as the amount that will absorb a minimum of 2,85 g of water vapour at 20 % RH and 25 °C. To
meet the dry pack requirements of this document, the amount of water vapour that a UNIT of
desiccant can absorb at 10 % RH and 25 °C shall be known.
When the desiccant capacity at 10 % RH and 25 °C is known, the following equation should
be used.
U = (0,003 × M × WVTR × A)/D (1)
where
U = amount of desiccant in UNITS;
M = shelf life desired in months;
WVTR = water vapour transmission rate in g/m in 24 h;
A = total surface area of the MBB in m ;
D = amount of water in grams, that a UNIT of desiccant will absorb at 10 % RH and 25 °C.
When the desiccant capacity at 10 % RH and 25 °C is not known, the quantity needed can be
estimated using the following simplified equation.
U = 8 × A (2)
where
U = amount of desiccant in UNITS;
A = total surface area of the MBB in m .
If it is desired to minimize the amount of desiccant used for dry-packing level 2 components, a
value of D based on the amount of water in grams that a UNIT of desiccant will absorb at
60 % RH and 25 °C should be used in the formula. This value can be obtained from the
desiccant manufacturer. When this option is used, it can be verified that, when the component
was classified in accordance with IEC 60749-20, it has achieved full saturation during
moisture soak.
– 14 – IEC 60749-20-1:2019 © IEC:2019
No moisture-absorbing material (e.g. trays, tubes, reels, foam end caps) should be placed in
the dry bag without baking. Any such material that is included increases the amount of
desiccant needed to meet the calculated shelf life (see 7.4.2) by an amount based on the
moisture content of the material. This can be determined by weighing a representative
quantity of material known to be at equilibrium with the manufacturing environment, baking to
a new constant weight, and subtracting the final from the initial weight. Additional UNIT(s) of
desiccant, based on 10 % RH at 25 °C, should be added to absorb the amount of water, in
grams, egressed from the packing materials (dunnage) after baking.
5.3.2.3 Desiccant handling and storage
Desiccant capacity decreases rapidly when exposed to 30 °C/60 % RH. Therefore, the
desiccant should remain in the manufacturer’s container or stored in a dry cabinet at < 5 %
RH until use. When dry packing, the desiccant shall be removed from the storage container
just prior to placing it into the MBB and sealing the MBB.
5.3.2.4 Humidity indicator card (HIC)
The HIC shall comply with relevant national standards governing chemically impregnated
humidity indicator cards. For level A2, the HIC shall have a sensitivity valu
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