IEC 63378-2-1:2024

IEC 63378-2-1 ®
Edition 1.0 2024-10
INTERNATIONAL
STANDARD
Thermal standardization on semiconductor packages –
Part 2-1: 3D thermal simulation models of semiconductor packages for steady-
state analysis – Discrete packages

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.

IEC Secretariat Tel.: +41 22 919 02 11
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.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews, graphical symbols and the glossary.
committee, …). It also gives information on projects, replaced With a subscription you will always have access to up to date
and withdrawn publications. content tailored to your needs.

IEC Just Published - webstore.iec.ch/justpublished
Electropedia - www.electropedia.org
Stay up to date on all new IEC publications. Just Published
The world's leading online dictionary on electrotechnology,
details all new publications released. Available online and once
containing more than 22 500 terminological entries in English
a month by email.
and French, with equivalent terms in 25 additional languages.

Also known as the International Electrotechnical Vocabulary
IEC Customer Service Centre - webstore.iec.ch/csc
(IEV) online.
If you wish to give us your feedback on this publication or need

further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC 63378-2-1 ®
Edition 1.0 2024-10
INTERNATIONAL
STANDARD
Thermal standardization on semiconductor packages –

Part 2-1: 3D thermal simulation models of semiconductor packages for steady-

state analysis – Discrete packages

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.080.01  ISBN 978-2-8322-9816-9

– 2 – IEC 63378-2-1:2024 © IEC 2024
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Attributes of 3D thermal models . 5
4.1 General . 5
4.2 TO-243 . 6
4.3 TO-252 . 8
4.4 TO-263 . 10
Annex A (normative) Contribution analysis in the case of TO-252 . 12
A.1 Attributes of a sample package . 12
A.2 Simulation validation . 14
Bibliography . 15

Figure 1 – Dimensions of TO-243 . 6
Figure 2 – Dimensions of TO-252 . 8
Figure 3 – Dimensions of TO-263 . 10
Figure A.1 – Sample package of TO-252. 12
Figure A.2 – Results of contribution analysis. 13
Figure A.3 – Accuracy comparison . 14

Table 1 – Attributes for TO-243 . 7
Table 2 – Attributes for TO-252 . 9
Table 3 – Attributes for TO-263 . 11
Table A.1 – Attributes and their range of a sample package . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
THERMAL STANDARDIZATION ON SEMICONDUCTOR PACKAGES –

Part 2-1: 3D thermal simulation models of semiconductor
packages for steady-state analysis – Discrete packages

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 (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 63378-2-1 has been prepared by subcommittee 47D: Semiconductor devices packaging, of
IEC technical committee 47: Semiconductor devices. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
47D/976/FDIS 47D/982/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.

– 4 – IEC 63378-2-1:2024 © IEC 2024
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 63378 series, published under the general title Thermal
standardization on semiconductor packages, 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.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

THERMAL STANDARDIZATION ON SEMICONDUCTOR PACKAGES –

Part 2-1: 3D thermal simulation models of semiconductor
packages for steady-state analysis – Discrete packages

1 Scope
This part of IEC 63378 specifies three-dimensional (3D) thermal models of discrete
semiconductor packages (TO-243, TO-252 and TO-263), utilized in the steady-state thermal
analysis of electronic devices to estimate junction temperatures accurately.
This model is assumed to be made by semiconductor suppliers and to be used by assembly
makers of electronic devices.
2 Normative references
There are no normative references in this document.
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
detailed model
semiconductor package model which has both the structures of each portion, such as die or
moulding or terminal, and the material properties for thermal analysis
Note 1 to entry: This model is often simplified to some extent.
4 Attributes of 3D thermal models
4.1 General
Clause 4 shows the attributes such as dimensions and thermal properties of three different type
of TO-packages. These attributes are used to estimate junction temperatures.

– 6 – IEC 63378-2-1:2024 © IEC 2024
4.2 TO-243
Figure 1 and Table 1 show the attributes which TO-243 thermal simulation models shall have.

Figure 1 – Dimensions of TO-243

Table 1 – Attributes for TO-243

Attribute Symbol Value Unit
Package thickness A m
Terminal width b m
b
Heat spreader width m
b
Centre terminal width m
Terminal thickness C m
Package width D m
Package body length E m
Terminal pitch e m
H
Span m
E
Dimension
Terminal length L m
L
Exposed terminal length m
L
Heat spreader length m
S
Die width X m
Die length Y m
Y
Die length offset m
Die thickness Z m
Z
Die attach thickness m
d
k
Thermal conductivity of die W/(m × K)
d
k
Thermal conductivity of die attach W/(m × K)
da
Thermal
conductivity
k
Thermal conductivity of molding W/(m × K)
m
k
Thermal conductivity of heat spreader W/(m × K)
s
NOTE 1 The default thermal conductivity of molding is 0,6 W/(m∙K) and that of heat spreader is 300 W/(m × K).
The thermal conductivity of die and die attach varies a lot according to the material adopted.
NOTE 2 The thickness of molding is the same as package thickness "A".
NOTE 3 The length and width of the die attach are the same as those of die X and Y.
NOTE 4
...