IEC TR 60297-3-1:2023
(Main)Mechanical structures for electrical and electronic equipment - Dimensions of mechanical structures of the 482,6 mm (19 in) series - Part 3-1: Technological schemes and applications
Mechanical structures for electrical and electronic equipment - Dimensions of mechanical structures of the 482,6 mm (19 in) series - Part 3-1: Technological schemes and applications
IEC 60297-3-1:2023 provides information on the technological schemes of the IEC 60297 series and shows how to apply the 19-inch series standards for the mechanical structure practices for electrical and electronic equipment.
The content of the corrigendum 1 (2025-11) has been included in this copy.
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IEC TR 60297-3-1 ®
Edition 1.0 2023-02
TECHNICAL
REPORT
colour
inside
Mechanical structures for electrical and electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series
Part 3-1: Technological schemes and applications
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IEC TR 60297-3-1 ®
Edition 1.0 2023-02
TECHNICAL
REPORT
colour
inside
Mechanical structures for electrical and electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series
Part 3-1: Technological schemes and applications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.240 ISBN 978-2-8322-6398-3
– 2 – IEC TR 60297-3-1:2023 © IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Technological scheme of the IEC 60297 series . 10
4.1 Development history and technological background . 10
4.1.1 General . 10
4.1.2 Development of the 482,6 mm (19 in) subracks and associated plug-in
units (19-inch subrack system) . 10
4.1.3 Adoption of IEC 60603-2 connector in the 482,6 mm (19 in) subracks
and associated plug-in units ("19-inch subrack system") . 13
4.1.4 Modular structure of the 482,6 mm (19 in) series . 14
4.2 Extended specifications of the 486,2 mm (19 in) series . 16
4.2.1 General . 16
4.2.2 Extended specifications of 19-inch subrack system by the IEC 60917
series . 16
4.2.3 Enhanced 19-inch subrack system from the market applications . 18
5 Definition domains of the 482,6 mm (19 in) series standards . 18
6 Prospect for further applications and standards development of the 19-inch
subrack system . 20
Annex A (informative) Applicable connectors to the 482,6 mm (19 in) subracks and
associated plug-in units . 21
A.1 General conditions of the applicable connectors . 21
A.2 List of applicable connectors . 22
Annex B (informative) IEEE and VITA standards related with the 482,6 mm (19 in)
series . 25
B.1 Subracks and associated plug-in units . 25
B.2 Mezzanine card standards . 25
B.3 Conduction cooling . 28
B.4 Environmental specifications . 31
Bibliography . 33
Figure 1 – Unified printed board size accommodated with height and depth of the
subracks (recommended dimension matrix) . 12
Figure 2 – Typical image of 19-inch subrack system (6U subrack with plug-in units,
where the plug-in units are interconnected by a backplane fixed on the subrack frame) . 13
Figure 3 – Modular structure of the 482,6 mm (19 in) series. 15
Figure 4 – Basic dimensions of the modular structure of the 482,6 mm (19 in) series . 16
Figure 5 – Definition domains of the 482,6 mm (19 in) series standards . 20
Figure A.1 – Dimensional relations of the connectors within mating condition, in the
482,6 mm (19 in) subracks and associated plug-in units . 22
Figure B.1 – Examples of mezzanine card size (coordination dimensions as 25 mm
grid) and mezzanine card boundary envelope in IEEE 1301.4 . 26
Figure B.2 – Example of adoption of CMC single size on 6U depth 160 mm plug-in unit,
and outline of single size CMC (common mezzanine card) in IEEE 1386. 26
Figure B.3 – Outline of the CCA of 6U VME module in IEEE 1101.2 . 29
IEC TR 60297-3-1 © IEC 2023 – 3 –
Figure B.4 – Assembly of VPX-REDI 3U conduction cooled plug-in unit . 30
Figure B.5 – Assembly of VPX-REDI 3U conduction cooled chassis . 30
Table A.1 – Applicable connectors to the 482,6 mm (19 in) subracks and associated
plug-in units . 23
Table B.1 – IEEE and VITA standards for mezzanine cards applied on 19-inch subrack
system . 27
Table B.2 – Environmental class for the plug-in units in ANSI/VITA 47 . 31
– 4 – IEC TR 60297-3-1:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MECHANICAL STRUCTURES FOR ELECTRICAL AND
ELECTRONIC EQUIPMENT – DIMENSIONS OF MECHANICAL
STRUCTURES OF THE 482,6 mm (19 in) SERIES
Part 3-1: Technological schemes and applications
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
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TR 60297-3-1 has been prepared by subcommittee 48D: Mechanical structures for
electrical and electronic equipment, of IEC technical committee 48: Electrical connectors and
mechanical structures for electrical and electronic equipment. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
48D/756/DTR 48D/757/RVDTR
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 Technical Report is English.
IEC TR 60297-3-1 © IEC 2023 – 5 –
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 60297 series, published under the general title Mechanical structures
for electrical and electronic equipment – Dimensions of mechanical structures of the 482,6 mm
(19 in) series, can be found on the IEC website.
Future documents in this series will carry the new general title as cited above. Titles of existing
documents in this series will be updated at the time of the next edition.
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,
• replaced by a revised edition, or
• amended.
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.
– 6 – IEC TR 60297-3-1:2023 © IEC 2023
INTRODUCTION
The IEC 60297 series contains dimensional definitions of the entire mechanical structure layers
from level 1 to level 4 for electrical and electronic equipment practices. Nowadays, the
IEC 60917-1 generic standard defines all the elements and components in the mechanical
structure layers from level 1 to level 4, and they are adopted for the IEC 60917-2 (metric) series.
The original concept of the mechanical structure layers was established in DIN 41494 and
introduced into the former IEC 297 series, later republished as the IEC 60297 series. Therefore,
the second edition of IEC 60917-1:2019 (generic) categorizes the existing IEC 60297 series as
a "conventional standard (legacy system)", which contains the detail dimensions of the structure
levels from level 1 to level 4 as well as the structure levels of the IEC 60917-2 series (metric).
Applications of the IEC 60297 series are divided into two different perceptions by the users:
a) the traditional 19-inch racks and chassis configurations, and
b) the 19-inch subrack system.
The latter has been providing effective and rational solutions for the critical issues on
interconnection and packaging for electronic equipment, which have been in a close relationship
with the IEC connector standards of IEC SC 48B, in the microelectronics era since the 1960s.
In the 1980s, the 19-inch subrack system was adopted as the mechanical specifications for
open computer bus standards in the IEEE and other manufacturers' associations or industrial
consortia. In such fields, not only newly developed high-performance connectors have been
applied, but also advanced mechanical features have been developed, based on the 19-inch
subrack system. These new technologies have been standardized, and their efforts considered
as development for extended specifications for the 19-inch subrack system in IEC SC 48D.
From these points of view, this Technical Report has been prepared to provide the following
information, not only for users of the IEC 60297 series standards, but also for the engineers
who will develop new architectures or hardware for advanced ICT equipment or systems for the
current IoT or Industry 4.0 era:
– information on technological schemes of the IEC 60297 series standards, which have been
in development for over 40 years in IEC TC 48/SC 48D. (In the market for industrial
electronics and information and communication technology (ICT), there are active users who
take the two different approaches regarding the application or adoption of the technologies
from the IEC 60297 series standards);
– the technological background of the standards, and the principles or concepts, which had
been adopted to cope with the technological evolutions through the development process of
the IEC 60297 series standards in IEC SC 48D;
– in standardization for mechanical structures for electrical and electronic equipment in
IEC SC 48D, IEC 60917-1 has been published as the generic standard for modular order for
the development of mechanical structures for electrical and electronic equipment practices.
The IEC 60297 series also considered that the dimensions of the mechanical structure are
partly in accordance with IEC 60917-1. This document clarifies the relationship between the
IEC 60917 series and the IEC 60297 series;
– to introduce the domain of each part of the IEC 60297 series for structures for electrical and
electronic equipment.
Annex A introduces applicable connectors for the 19-inch subrack system, including newly
developed high-performance connectors which are not (yet) published as IEC SC 48B
standards.
IEC TR 60297-3-1 © IEC 2023 – 7 –
Annex B introduces relationships and compatibilities between the 19-inch subrack system
standards in IEC SC 48D, the IEEE standards for the 19-inch subrack and plug-in units, and
other industrial standards for the mechanical specifications. It also shows outlines of the
extended mechanical features adopted for the 19-inch subrack system. These features include
the implementations of the mezzanine cards and the conduction cooled system, and they are
not yet defined in IEC SC 48D standards.
Through the study of the additional information given in Annex A and Annex B, further prospects
on applications of the 19-inch subrack system will be seen, and the directions of the next
standards development in IEC TC 48/SC 48D will be provided.
– 8 – IEC TR 60297-3-1:2023 © IEC 2023
MECHANICAL STRUCTURES FOR ELECTRICAL AND
ELECTRONIC EQUIPMENT – DIMENSIONS OF MECHANICAL
STRUCTURES OF THE 482,6 mm (19 in) SERIES
Part 3-1: Technological schemes and applications
1 Scope
This part of IEC 60297 provides information on the technological schemes of the IEC 60297
series, and shows how to apply the 19-inch series standards for the mechanical structure
practices for electrical and electronic equipment.
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 60297-3-100:2008, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-100: Basic dimensions of front
panels, subracks, chassis, racks and cabinets
IEC 60297-3-101:2004, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-101: Subracks and associated
plug-in units
IEC 60297-3-102:2004, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-102: Injector/extractor handle
IEC 60297-3-103:2004, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-103: Keying and alignment pin
IEC 60297-3-104:2006, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-104: Connector dependent
interface dimensions of subracks and plug-in units
IEC 60297-3-105:2008, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-105: Dimensions and design
aspects for 1U high chassis
IEC 60297-3-106:2010, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-106: Adaptation dimensions for
subracks and chassis applicable with metric cabinets or racks in accordance with
IEC 60917-2-1
IEC 60297-3-107:2012, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-107: Dimensions of subracks and
plug-in units, small form factor
IEC 60297-3-108:2014, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-108: Dimensions of R-type
subracks and plug-in units
IEC TR 60297-3-1 © IEC 2023 – 9 –
IEC 60297-3-109:2015, Mechanical structures for electrical and electronic equipment –
Dimensions of mechanical structures of the 482,6 mm (19 in) series – Part 3-109: Dimensions
of chassis for embedded computing devices
IEC 60297-3-110:2018, Mechanical structures for electrical and electronic equipment –
Dimensions of mechanical structures of the 482,6 mm (19 in) series – Part 3-110: Residential
racks and cabinets for smart houses
IEC 60603-2, Connectors for frequencies below 3 MHz for use with printed boards – Part 2:
Detail specification for two-part connectors with assessed quality, for printed boards, for basic
grid of 2,54 mm (0,1 in) with common mounting features
IEC 60917-1, Modular order for the development of mechanical structures for electrical and
electronic equipment practices – Part 1: Generic standard
IEC 60917-2:1992, Modular order for the development of mechanical structures for electronic
equipment practices – Part 2: Sectional specification – Interface co-ordination dimensions for
the 25 mm equipment practice
IEC 60917-2-1:1993, Modular order for the development of mechanical structures for electronic
equipment practices – Part 2: Sectional specification – Interface co-ordination dimensions for
the 25 mm equipment practice – Section 1: Detail specification – Dimensions for cabinets and
racks
IEC 60917-2-2:1994, Modular order for the development of mechanical structures for electronic
equipment practices – Part 2: Sectional specification – Interface co-ordination dimensions for
the 25 mm equipment practice – Section 2: Detail specification – Dimensions for subracks,
chassis, backplanes, front panels and plug-in units
IEC 61076-4-100, Connectors for electronic equipment – Part 4-100: Printed board connectors
with assessed quality – Detail specification for two-part connector modules having a grid of
2,5 mm for printed boards and backplanes
IEC 61076-4-101, Connectors for electronic equipment – Part 4-101: Printed board connectors
with assessed quality – Detail specification for two-part connector modules, having a basic grid
of 2,0 mm for printed boards and backplanes in accordance with IEC 60917
IEC 61076-4-113, Connectors for electronic equipment – Printed board connectors – Part 4-113:
Detail specification for two-part connectors having 5 rows with a grid of 2,54 mm for printed
boards and backplanes in bus applications
IEC 61076-4-116, Connectors for electronic equipment – Product requirements – Part 4-116:
Printed board connectors – Detail specification for a high-speed two-part connector with
integrated shielding function
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:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
– 10 – IEC TR 60297-3-1:2023 © IEC 2023
4 Technological scheme of the IEC 60297 series
4.1 Development history and technological background
4.1.1 General
This Subclause 4.1 introduces the history of the development and the applications of the
IEC 60297-X series in IEC SC 48D.
The initial standards of the IEC 60297-X series were published at the beginning of the 1980s.
Before the publication of IEC standards, there was the EIA 19-inch rack standard (ANSI/EIA
RS310-C 1971 Rack, Panels and Associated Equipment ), and the combination of 19-inch racks
or cabinets and 19-inch chassis (modular chassis) in accordance with the EIA standard had
been used broadly for telecommunication, instrumentation, and other electronic equipment in
many countries. This model is still being applied to current IT equipment, servers, etc., which
are mounted within the 19-inch racks/cabinets in datacentres. It is the traditional 19-inch rack
and chassis configuration of the 482,6 mm (19 in) standard series.
IEC 60297-3 was published in 1984. This standard was developed by DIN and IEC SC 48D
under the following circumstances.
4.1.2 Development of the 482,6 mm (19 in) subracks and associated plug-in units
(19-inch subrack system)
In the middle of the 1960s, to cope with the expanding adoption of printed boards (PBs) in the
fields of industrial electronics and telecommunication equipment, the development of a
mechanical structure for housing PBs in a rack started in Germany. The dimensions of the rack
and chassis were adopted from the 19-inch EIA standard, and the following development
concept was established to mount the PBs into the 19-inch modular chassis as the structure of
482,6 mm (19 in) subracks and associated plug-in units.
Electronic equipment for telecommunication or industrial uses is required to obtain reliability,
compatibility and interchangeability for easy maintenance. In such electronic equipment, in the
case where one electronic system consists of multiple PCBs (functional units/sub-systems, they
are interconnected in one chassis), its hardware should adopt the mechanical structure
described above. And, the mechanical structure, 482,6 mm (19 in) subracks and associated
plug-in units, shall be designed based on the following principles.
• The sizes of PBs of plug-in units are unified and based on the height and depth of the
accommodated subracks.
• The adopted connectors on the PBs of plug-in units are unified and standardized to establish
the interconnection between plug-in units (via a backplane or wire-wrap , which is a cable-
connecting technology between tail pins of fixed connectors on the backside of a subrack).
• The plug-in units are placed vertically in the subracks to promote convective air flow for heat
dissipation.
___________
The main parts of the IEC 60297-X series were published in the 1980s. IEC 60297-1:1986 and IEC 60297-2:1982
were merged into IEC 60297-3-100:2008.
The standard defines a flange width of 19 in (482,6 mm) and a height pitch of 1U = 1,75 in (44,45 mm) for
mounting the chassis to the rack.
IEC 60297-3:1984 was replaced by IEC 60297-3-101:2004.
Wrapped connections are described in IEC 60352-1.
IEC TR 60297-3-1 © IEC 2023 – 11 –
In accordance with these principles, the basic size of the PB for the 482,6 mm (19 in) subracks
was defined as 100 mm × 100 mm and adopted for the 3U high subrack . One connector in
accordance with IEC 60603-2/DIN 41612 is placed on the 100 mm high PB. The extended sizes
were also defined with regard to height as the double-size with two connectors for a 6U subrack
and triple-size with three connectors placed on a 9U subrack, and with regard to depth in
increments of 60 mm (see Figure 1 and Figure 2).
These modular structures and dimensions were adopted by DIN standards and proposed in
IEC SC 48D. Consequently IEC 60297-3 was published in 1984.
The mechanical architecture of the 19-inch subrack system consists of plug-in units (connectors
and PBs assembled with other mechanical parts) and subracks, in which the plug-in units are
interconnected via the adoption of standard connectors on a backplane in a subrack. The
configuration of the 19-inch subrack system has provided a rational hardware solution to
microcomputing systems and microelectronics equipment for industrial and commercial uses.
In the industrial electronics and ICT market, the 19-inch subrack system in the 482,6 mm (19 in)
standard series was accepted as an effective solution to the issue of packaging and
interconnection for electronic equipment.
The 19-inch subrack system had been adding advanced extended features through the 1990s
to the 2010s (see 4.2), and their applications had been expanding in the same market.
___________
3U (133,35 mm) high subrack is defined to have the 100 mm high PBs vertically installed in accordance with the
principles described, and such subracks are mounted into the 482,6 mm (19 in) cabinets or racks. See IEC 60297-
3-101.
– 12 – IEC TR 60297-3-1:2023 © IEC 2023
Dimensions in millimetres
Figure 1 – Unified printed board size accommodated with height and depth
of the subracks (recommended dimension matrix)
IEC TR 60297-3-1 © IEC 2023 – 13 –
Dimensions in millimetres
Figure 2 – Typical image of 19-inch subrack system (6U subrack with plug-in units,
where the plug-in units are interconnected by a backplane fixed on the subrack frame)
4.1.3 Adoption of IEC 60603-2 connector in the 482,6 mm (19 in) subracks and
associated plug-in units ("19-inch subrack system")
In the development of the 19-inch subrack system at DIN and IEC SC 48D, it was assumed that
the DIN 41612 connectors would be adopted for interconnecting the plug-in units via backplanes
in the subracks.
– 14 – IEC TR 60297-3-1:2023 © IEC 2023
The DIN 41612 connector is a board-to-board connector and consists of a free board connector
and a fixed board connector, which has a three-rows of a maximum of 32 contact pins on the
2,54 mm (0,1 in) grid (total 96 pin-count). The length of the connector is suited to the 100 mm
high PB.
The major parts of the DIN 41612 series were released in the late 1970s. In the early 1980s,
IEC 60603-2 was published by IEC SC 48B. (The 2,54 mm grid arrangement of the IEC 60603-
2/DIN 41612 connector had been used as the grid for PBs in the electronics industry , and it
also affected the dimensions of the subracks and associated plug-in units ).
In the early 1980s, the most important technological issue in the relationship between the
IEC 60603-2 connector and the 19-inch subrack system was how to provide a solution to the
problems of the physical interconnection between functional PB modules. The functional PB
modules were data processing units, I/O units, memory storage, a system management module,
etc., for digital telecommunication equipment and industrial computing systems in the coming
evolutions in the microelectronics era. The IEC 60603-2 standard has been defined to ensure
not only reliability of the interconnection and durability of the mechanical structure, but also
compatibility for general industrial use , and actual products that had been widely accepted in
the fields of industrial electronics and ICT equipment. The IEC 60297-X series 482,6 mm (19 in)
standards for the subracks and associated plug-in units provided the physical environment to
realize the performance and capability of the IEC 60603-2 connector fully by the modular
structure based on design principles.
4.1.4 Modular structure of the 482,6 mm (19 in) series
The concept of modular structure for the mechanical structure for electronic equipment was
established through the development of the 482,6 mm (19 in) series in DIN and IEC SC 48D.
The basic dimensions of the modular system consist of the inch modular pitch (1U = 1,75 in,
1 HP = 0,2 in and 0,1 grid on the print boards) and the metric pitch (the base dimension of the
printed board which is 100 mm × 100 mm and the overall dimensions of the 19-inch cabinets).
The metric dimensions are dealt with in accordance with the modular grid of IEC 60917-1.
Figure 3 shows the modular structure of the 482,6 mm (19 in) series. Figure 4 introduces the
basic dimensions of the modular structure of the 482,6 mm (19 in) series.
___________
The 0,1 in pitch of dual in-line packages (DIP) was developed as one of basic designs in microelectronics
components in the middle of the 1960s. Through the 1970s, wiring and components layout on printed boards
were designed based on the 2,54 mm (0,1 in) grid. IEC TC 52 published a standard on the 2,54 mm grid. In the
1980s, due to the evolution of printed board assembly technology by spread of the surface mounting technology,
etc., the 2,54 mm grid on printed boards became no longer a major design method and the standard was
withdrawn. IEC TC 52 was merged into IEC TC 91.
The increment of the horizontal pitch is defined as 1 HP = 5,08 mm (0,2 in) for the 482,6 mm (19 in) subracks
and associated plug-in units. See IEC 60297-3-101.
Compatibility between products from different manufacturers has been established by the detailed definitions of
performance requirements and test specifications.
The concept of the modular structure or modular system of the 482,6 mm (19 in) system for electronic equipment
is defined in the DIN 41494 standard. But there are no descriptions of the modular structure consisting of the four
modular levels (from Level 1 to Level 4) in the current IEC 60297-3-XXX series. Instead of the modular structure
of the 482,6 mm (19 in) system, the IEC 60917-1:1989 generic standard defines "Structures for electronic
equipment practices" and "Co-ordination dimensions" based on the metric modular grid. The concept of the
structures of electronic equipment practices in IEC 60917-1 is accommodated with the idea of the mechanical
structure layers from Level 1 to Level 4. It is the same as the modular system defined in DIN 41494. Therefore,
the IEC 60297-3-XXX series is considered as one of several subsidized standard series complying with the
concept of the IEC 60917 generic standard.
IEC TR 60297-3-1 © IEC 2023 – 15 –
Figure 3 – Modular structure of the 482,6 mm (19 in) series
– 16 – IEC TR 60297-3-1:2023 © IEC 2023
Dimensions in millimetres
Key
Inch-based dimensions are highlighted in orange. Blue highlighted columns indicate metric dimensions (mm).
Figure 4 – Basic dimensions of the modular structure of the 482,6 mm (19 in) series
4.2 Extended specifications of the 486,2 mm (19 in) series
4.2.1 General
The current 482,6 mm (19 in) series, the IEC 60297-3-XXX series, were accomplished through
two-step extensions in the 1990s and 2010s.
4.2.2 Extended specifications of 19-inch subrack system by the IEC 60917 series
Initially, the DIN/IEC standards, the 482,6 mm (19 in) subracks and associated plug-in units
(19-inch subrack system) with IEC 60603-2 connectors, were intended for telecommunication
equipment in Europe. In the early 1980s, the application had expanded into the field of the IEEE
standardized open computer-bus system using 16/32 bit MPU (microprocessor unit). Those
open-bus architectures specified the 3U/6U 19-inch subrack system and IEC 60603-2
connectors as the packaging and interconnection for computer hardware. The IEEE Computer
Society also released their own standards for the 19-inch subrack system . The combination
___________
IEEE 1014-1987 (VME bus), IEEE 1296-1987 (MULTIBUS II), etc.
IEEE 1101.1-1991, IEEE Standard for Mechanical Core Specifications for Microcomputers Using IEC 603-2
Connectors. Current edition: IEEE 1101.1-1998, IEEE Standard for Mechanical Core Specifications for
Microcomputers Using IEC 60603-2 Connectors.
IEC TR 60297-3-1 © IEC 2023 – 17 –
of the IEC 60297 mechanical structure system and IEC 60603-2 connectors became one of the
major standard mechanical systems for the industrial computing systems and other electronic
equipment except for military uses or space and aviation applications.
On the other hand, in the middle of the 1980s, DIN and IEC SC 48D started the new
development of the mechanical structures for electronic equipment practices based on the
metric modular order (adoption of metric modular grid for the entire mechanical structures). It
was considered that such development would be an urgent and necessary project to cope with
the next coming evolution of the microelectronics and computer technology. And, according to
the following development concept, IEC 60917-1 "Generic standard" consisting of the modular
order of 0,5 mm, 2,5 mm and 25 mm grids and the coordination dimensions, was published in
1988.
Design concepts for the new development of the mechanical structures for electronic equipment
practices are:
a) Adopting a dimensional system premised on the use of CAD/CAE.
b) Support for interconnection and packaging of high-density printed board with SMD/SMT.
c) Support adoptions of high pin-count and high-speed connectors for the high-density
interconnections that accompany the uses of high-density printed boards.
d) Support appropriate measures against EMC and heat problems that are caused by the
higher density of printed boards and electronics components and higher signal speed
devices.
Under the IEC 60917-1 generic standard, practical standards on the metric mechanical
structure (metric cabinet/rack and subrack system based on the 25 mm equipment practice)
were developed and published by DIN, IEC SC 48D and IEEE in the early 1990s. In the
connector industry, the high pin-count and high-speed metric connectors based on the 0,5 mm,
2,5 mm, and 25 mm grid, were developed and published as IEC standards by IEC SC 48B in
parallel with the standards on metric mechanical structures. At that time, it was considered that
the packaging and interconnection solution by the combination of the IEC 60297 mechanical
structures and the IEC 60603-2 connectors would be replaced by the metric system.
In the industry for the mechanical structures related with IEC SC 48D, after development of
actual products in accordance with the practical standards on the metric subrack system, the
new technologies for the metric subrack system were applied to the 482,6 mm (19 in) series.
The 19-inch subrack system adopted the extended features which had been implemented in the
metric subrack system in accordance with the development concept of the IEC 60917 series
standards. Through the reconstruction of the IEC 60297 series in the 2000s, respective
elements of such new technologies were published as follows:
– IEC 60297-3-101:2004 (where EMC provisions were added);
– IEC 60297-3-102:2004 (where new functions for plug-in unit handles were added);
– IEC 60297-3-103:2004 (function to distinguish the positions of the plug-in units in a
subrack);
– IEC 60297-3-104:2006 (where the definition of how to adopt newly developed connectors
was added).
Items b), c) and d) of the development concept of IEC 60917-1 have been covered by these
standards, and the issue of item a) has been solved by rapid evolution of processing
performance of CAD/CAE systems.
___________
Metric structure standards: DIN 43356 series (Withdrawn), IEC 60917-2:1992, IEC 60917-2-1:1994, IEC 60917-
2-2:1994 , and IEEE 1301-1991 (Withdrawn).
The metric modular connectors based on the 2 mm or 2,5 mm grid are IEC 61076-4-100, IEC 61076-4-101,
IEC 61076-4-104, etc.
– 18 – IEC TR 60297-3-1:2023 © IEC 2023
4.2.3 Enhanced 19-inch subrack system from the market applications
The next functional extension was brought by the explosive expansion of the internet technology
and personal computer which started in the second half of the 1990s. The booming of the ICT
(Information & Communication Technology) market affected the application of the 482,6 mm
(19 in) series. To cope with requirements for more high-speed data transmission and data
processing in systems or networks and computing or communication devices, high speed
parallel or serial interface were developed and such functional elements became modules.
Conventional telecommunication equipment had been using proprietary architectures in their
hardware, but it became real that the newly developed ICT market, in which the conventional
telecommunication technology converged with the computer network/internet technology, made
such hardware shift to the open architecture. AdvancedTCA (Advanced Telecommunications
Computing Architecture) and MicroTCA (Micro Telecommunications Computing Architecture) ,
developed in PICMG and in which many international companies were involved, are typical
examples of such open architectures.
Based on the chassis for AdvancedTCA and MicroTCA, which adopted the 19-inch subrack
system in their basic dimensions, enhanced mechanical structure standards over the 482,6 mm
subracks and associated plug-in units were published as follows:
– IEC 60297-3-107:2012 (based on MicroTCA mechanical form factor);
– IEC 60297-3-108:2014 (which reflects AdvancedTCA mechanical features).
The differences of the applications between the IEC 60297-3-101 conventional 482,6 mm
subracks and associated plug-in units, IEC 60297-3-107 and IEC 60297-3-108 are shown in
Figure 5, Definition domain b).
5 Definition domains of the 482,6 mm (19 in) series standards
The current IEC 60297 series (IEC 60297-3-XXX series) consists of ten standards, which are
not categorized for the users.
Figure 5 shows that these IEC 60297 series standards are divided into three categories, and,
within each category, the definition domains of the ten standards referring to the layer levels of
the mechanical structure are introduced.
___________
Specifications of the chassis (subrack with cooling units) for AdvancedTCA (PICMG 3.0) and MicroTCA (PICMG
MTCA.0) were developed based on the 19-inch subrack system by PICMG (PCI Industrial Computer
Manufacturers Group, an international industrial consortium developing open standards for high performance
telecommunications and industrial computing applications).
IEC TR 60297-3-1 © IEC 2023 – 19 –
a) Conventional 19-inch system, including the extended
specifications from the IEC 60917 series (See 4.2.2)
b) Extended 19-inch system, including the enhanced subrack
system from the market applications (See 4.2.3)
– 20 – IEC TR 60297-3-1:2023 © IEC 2023
c) 19-inch application related standards
Figure 5 – Definition domains of the 482,6 mm (19 in) series standards
6 Prospect for further applications and standards development of the 19-inch
subrack system
Through this review of the technological scheme of the IEC 60297 series, it becomes clear that
users in the industrial electronics and ICT market have recognized that the 19-inch series
standards, especially the subrack system, have been providing us
...
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