IEC 62396-4:2013

Process management for avionics - Atmospheric radiation effects - Part 4: Design of high voltage aircraft electronics managing potential single event effects

IEC 62396-4:2013(E) provides guidance on atmospheric radiation effects and their management on high voltage (nominally above 200 V) avionics electronics used in aircraft operating at altitudes up to 60 000 ft (18,3 km). This part of IEC 62396 defines the effects of that environment on high voltage electronics and provides design considerations for the accommodation of those effects within avionics systems. This part of IEC 62396 provides technical data and methodology for aerospace equipment manufacturers and designers to standardise their approach to single event effects on high voltage avionics by providing guidance, leading to a standard methodology.
This publication is to be read in conjunction with IEC 62396-1:2012.

General Information

• Status: Published
• Publication Date: 24-Sep-2013
• ICS: 03.100.50 - Production. Production management
• ICS: 31.020 - Electronic components in general
• ICS: 49.060 - Aerospace electric equipment and systems
• Technical Committee: TC 107 - Process management for avionics
• Current Stage: PPUB - Publication issued
• Start Date: 25-Sep-2013
• Completion Date: 30-Sep-2013

Relations

• Replaces: IEC TS 62396-4:2008 - Process management for avionics - Atmospheric radiation effects - Part 4: Guidelines for designing with high voltage aircraft electronics and potential single event effects
• Effective Date: 05-Sep-2023

Overview

IEC 62396-4:2013 - Process management for avionics - Atmospheric radiation effects - Part 4 provides guidance for the design of high voltage aircraft electronics (nominally >200 V) to manage atmospheric radiation-induced failures at altitudes up to 60 000 ft (18.3 km). Intended as a complement to IEC 62396-1:2012, this part focuses on the physics, quantification and mitigation of radiation-driven destructive events in high-voltage power semiconductors used in avionics.

Key topics and technical requirements

• Primary failure mechanisms: Describes and distinguishes single event burnout (SEB) and single event gate rupture (SEGR) as the main radiation-induced threats to high voltage MOSFETs, IGBTs, diodes and bipolar power devices.
• Radiation sources and sensitivity: Explains that SEB/SEGR can be triggered by heavy ions, high-energy protons and high-energy/thermal neutrons, and highlights the greater atmospheric neutron flux at flight altitudes vs. sea level.
• Quantification and testing guidance:
  • Methodology for measuring SEB cross-sections and calculating SEB rates for aircraft altitudes.
  • Use of accelerated test data (e.g., spallation neutron facilities such as the WNR beam) and interpretation guidance for avionics.
  • Measurement techniques for event charge/current (EPICS plots and event statistics) and discussion of how stress (applied voltage) affects event rates.
• Design considerations: Guidance for accommodating radiation effects at system and component levels, including conservative operating voltages and device selection strategies.
• Additional topics: Treatment of thermal neutron-induced SEB, potential SEGR from recoil ions, and consideration of alternative semiconductor materials (e.g., non-silicon technologies).

Practical applications and users

Who should use IEC 62396-4:

• Avionics system designers and aircraft electrical architects specifying high-voltage power electronics.
• Electronic equipment and component manufacturers (power MOSFET, IGBT, diode vendors) validating device robustness to atmospheric radiation.
• Aerospace qualification and test engineers conducting radiation testing, failure analysis and mitigation design. Practical uses:
• Standardizing radiation testing approaches and reporting for high-voltage avionics components.
• Informing design margins (operating voltages, protective circuitry) to reduce SEB/SEGR risk.
• Integrating radiation risk assessments into avionics procurement and safety cases.

Related standards

• IEC 62396-1:2012 - Accommodation of atmospheric radiation effects via single event effects within avionics electronic equipment (required companion document).

Keywords: IEC 62396-4, atmospheric radiation effects, high voltage avionics, single event burnout (SEB), single event gate rupture (SEGR), neutron-induced effects, radiation testing, aircraft electronics, avionics standards.

Standards Content (Sample)

IEC 62396-4 ®
Edition 1.0 2013-09
INTERNATIONAL
STANDARD
Process management for avionics – Atmospheric radiation effects –
Part 4: Design of high voltage aircraft electronics managing potential single
event effects
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 Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
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 corrigenda or an amendment might have been published.

Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: [e-mail].

IEC 62396-4 ®
Edition 1.0 2013-09
INTERNATIONAL
STANDARD
Process management for avionics – Atmospheric radiation effects –

Part 4: Design of high voltage aircraft electronics managing potential single

event effects
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
R
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-8322-1094-9

– 2 – 62396-4 © IEC:2013(E)
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Potential high voltage single event effects . 6
5 Quantifying single event burnout in avionics for high voltage devices . 8
6 Relevant SEB data and applying it to avionics . 9
6.1 SEB data from heavy ion testing is not relevant . 9
6.2 SEB data from high energy neutron and proton testing . 9
6.3 Calculating the SEB rate at aircraft altitudes . 12
6.4 Measurement of high voltage component radiation characteristics, EPICS . 12
6.5 Single event burnout due to thermal neutrons . 14
6.6 Alternative semiconductor materials to silicon . 15
7 Conclusion . 15
Bibliography . 17

Figure 1 – SEB cross sections measured in 400 V and 500 V MOSFETs for WNR

neutron and proton beams . 10
Figure 2 – SEB cross sections measured in 1 000 V MOSFETs and 1 200 V IGBTs
with WNR neutron and 200 MeV proton beams . 11
Figure 3 – Measurement of radiation event charge and current . 13
Figure 4 – EPICS plot of 1 200 V diode numbers of events at currents taken at different
9 2
applied voltages for a neutron fluence of approximately 3,5 × 10 neutrons per cm
measured at energies greater than 10 MeV . 14
Figure 5 – EPICS plot of 1 200 V diode numbers of events at currents taken at 675 V
(56 %) and 900 V (75 %) applied voltage (stress) demonstrating the difference
between low and high voltage stress – Fluence as per Figure 4 . 14

62396-4 © IEC:2013(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 4: Design of high voltage aircraft
electronics managing potential single event effects

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) 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.
International Standard IEC 62396-4 has been prepared by IEC technical committee 107:
Process management for avionics.
This International Standard is to be used in conjunction with IEC 62396-1:2012.
This first edition cancels and replaces IEC/TS 62396-4 published in 2008. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Change to title.
b) Clause 4 inclusion of SEGR.
c) Inclusion of 6.5 concerning SEB due to thermal neutrons.

– 4 – 62396-4 © IEC:2013(E)
d) Consideration of alternative materials to silicon in 6.6.
The text of this international standard is based on the following documents:
FDIS Report on voting
107/211/FDIS 107/221/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 the parts in the IEC 62396 series, published under the general title Process
management for avionics – Atmospheric radiation effects, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
A bilingual edition of this document may be issued at a later date.

62396-4 © IEC:2013(E) – 5 –
INTRODUCTION
This industry-wide international standard provides guidance and requirements to design high
voltage aircraft electronics for electronic equipment and avionics systems. It is intended for
avionics system designers, electronic equipment manufacturers, component manufacturers
and their customers to manage the single event effects produced in semiconductor devices
operating at high voltage (nominally above 200 V) by atmospheric radiation. It expands on the
information and guidance provided in IEC 62396-1:2012.
The internal elements of semiconductor devices operating at high applied voltage will be
subject to high voltage stress. The incident radiation causes ionisation charge within the
device, and the high voltage stress may cause a large increase (avalanche) in this charge,
which may be destructive. Within this part of IEC 62396 two effects are considered: single
event burnout (SEB), and single event gate rupture (SEGR).

– 6 – 62396-4 © IEC:2013(E)
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 4: Design of high voltage aircraft
electronics managing potential single event effects

1 Scope
This part of IEC 62396 provides guidance on atmospheric radiation effects and their
management on high voltage (nominally above 200 V) avionics electronics used in aircraft
operating at altitudes up to 60 000 ft (18,3 km). This part of IEC 62396 defines the effects of
that environment on high voltage electronics and provides design considerations for the
accommodation of those effects within avionics systems.
This part of IEC 62396 provides technical data and methodology for aerospace equipment
manufacturers and designers to standardise their approach to single event effects on high
voltage avionics by providing guidance, leading to a standard methodology.
Details are given of the types of single event effects relevant to the operation of high voltage
avionics electronics, methods of quantifying those effects, appropriate methods to provide
design and methodology to demonstrate the suitability of the electronics for the application.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62396-1:2012, Process management for avionics – Atmospheric radiation effects – Part 1:
Accommodation of atmospheric radiation effects via single event effects within avionics
electronic equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62396-1:2012 apply.
4 Potential high voltage single event effects
An N-channel power MOSFET can have two different types of destructive effects induced by
the deposition of charge from a single energetic particle, single event burnout (SEB) and
single event gate rupture (SEGR). Different tests performed on several devices show that is
difficult to induce SEB in P-channel MOSFET [1], [2] . In addition to this kind of power
MOSFET, other power devices, such as insulated gate bipolar transistors (IGBTs), bipolar
power transistors and diodes, which have large applied voltage biases and high internal
electric fields, are susceptible to SEB.
In SEB, the penetration of the source-body-drain region by the deposited charge can forward
bias the thin body region under the source. If the bias applied to the drain exceeds the local
___________
Numbers in square brackets refer to the Bibliography.

62396-4 © IEC:2013(E) – 7 –
breakdown voltage of the parasitic bipolar elements, the single event induced pulse initiates
avalanching in the drain depletion region that eventually leads to destructive burnout SEB.
SEB can be induced by heavy ions, high energy protons [3] and high energy neutrons [4].
SEGR applies to N- and P-channel MOSFETs. It is explained via the transient plasma filament
created by the energy deposition track when the MOSFET is struck through the thin gate
oxide region. As a result of this transient track filament, there is a localized increase in the
oxide field which can cause the oxide to break down, leading first to gate leakage and finally
to gate rupture. The SEGR failure mechanism has been widely studied by heavy ion testing
and effects have been identified on different devices with various levels of sensitivity [2]. For
the time being, experiments show also that SEGR induced by heavy ions is more an issue for
space systems, and guidance for heavy ion SEGR testing is available [5]. As a consequence
of the atmospheric neutrons, SEB is the major threat to high voltage electronics.
There remains a paucity of data on the question of neutron-induced single event gate rupture
(SEGR) in power devices. In the late 1990s one study looked for, but did not find, SEGR in
500 V power MOSFETs during accelerated spallation neutron testing [1]. Shortly afterwards,
however, dielectric breakdown was observed in 60 V power MOSFETs during 44 MeV and
200 MeV proton irradiation [6]. As the gate ruptures in these devices were almost certainly
caused by charge deposition from recoil ions, rather than by direct ionisation from the very
low LET protons, sensitivity to neutrons was implied.
Data published more recently show more direct evidence of neutron-induced SEGR in devices
rated at ~1 kV. Hands et al. observed significant gate damage to a 1 kV power MOSFET at a
spallation neutron facility, with a dependence on gate bias consistent with SEGR [7]. Griffoni
et al. tested a variety of devices, including IGBTs, SiC MOSFETs and superjunction (SJ)
MOSFETs in quasi-monoenergetic neutron environments, and observed SEGR only in the SJ
MOSFETs [8]. Interestingly, in this latter case the SEGR failure rate was sometimes higher
than the SEB failure rate, though no dependency on gate bias condition was investigated to
characterise the relative susceptibilities. These results demonstrate that fast neutrons (and
protons) are very capable of causing damage to the gate regions of power devices and, where
conditions are right, this damage can lead to dielectric breakdown and catastrophic failure.
Therefore this failure mode should be considered and, where appropriate, quantified during
accelerated testing of HV devices.
Although at the outset this threat to the power system in an aircraft from SEB from the
atmospheric neutrons may appear to be remote or even far-fetched, the experience of
breakdowns in the high voltage electronics on electric trains in Europe before 1995 shows
that SEB can be real and has happened in the field. In that case, European and Japanese
manufacturers of high voltage semiconductors noticed that some of their devices were
undergoing burnout failures in the field during normal operation of newly developed train
engines [9, 10]. The diodes and GTO thyristors (gate turn-off thyristors) used on the trains
were rated at 4 500 V, and were normally operated at 50 % to 60 % of rated voltage. They
were designed for terrestrial use for > 35 years, so when the failures first appeared in the field
after only a few months, this was puzzling. The failure mode was investigated in great detail
and eventually a set of experiments was carried out at three different locations (salt mine, top-
floor laboratory and basement); the results convinced the investigators that the cause of the
failures was the cosmic ray neutrons. Since that time, the manufacturers of these very high
voltage devices have been careful in recommending the voltage at which the devices can be
operated safely without SEB.
In addition, these manufacturers have followed the methodology established by an
experienced radiation effects group [1] by carrying out tests in the WNR beam at Los Alamos
National Laboratory to characterize the response of their devices to a simulated high-energy
neutron environment. Because the atmospheric neutron flux is higher by about a factor of 300
at aircraft altitudes compared to sea level, it is clear that the same effect can occur in high
voltage electronics in aircraft. The reason that, as far as is known, such failures have not
been experienced previously in the field in aircraft power electronics is that the bus voltage
used in aircraft systems has always been low enough to preclude SEB or SEGR.

– 8 – 62396-4 © IEC:2013(E)
Generally, the highest voltage used in aircraft power systems has been 270 V, and a practical
lower onset limit for most high voltage devices is 300 V. This practical lower limit stems from
the fact that with SEB there is a threshold voltage for the effect to occur; if V is kept below
ds
the threshold voltage, there will be no SEB. Thus for 270 V operation, devices rated at 400 V
or 500 V would be used, resulting in a situation in which the devices are being operated at a
derating factor of 67,5 % and 54 % respectively. Since the devices are being used at < 300 V
and with a derating factor of < 70 %, these conditions are sufficient to preclude any single
event burnout in the high voltage electronics.
However, in advanced designs for avionics systems significantly higher voltages are being
considered for the bus voltage in order to reduce the overall weight of the system. The
voltage will thus be > 300 V and in fact 600 V has often been mentioned as a practical bus
voltage. Thus, in order to preclude SEB from occurring in the high voltage electronics of such
advanced avionics systems, a sufficiently low derating factor will have to be used, and the
adequacy of the derating factor will have to be demonstrated through testing.
5 Quantifying single event burnout in avionics for high voltage devices
Thus, the problem becomes that avionics vendors are asked to provide systems that will
operate at higher voltages, e.g., 600 V, and there has been virtually no guidance for them to
use in developing the designs that will avoid the potential of SEB in the high voltage devices
such as power MOSFETs and IGBTs.
In reality, the situation with SEB in high voltage electronics is relatively similar to that of
single event upset (SEU), in low voltage devices (< 5 V) such as random access memories
(RAMs), microprocessors and FPGAs. The threat of SEU from the atmospheric neutrons in
the low voltage devices has been dealt with very extensively in the technical literature and in
IEC 62396-1:2012. The approach in IEC 62396-1:2012 is that the rate of the single event
effect, in this case SEU, in the devices, can be estimated by the following equation:
2 2
SEE rate per device (per hour) = 6 000 (n/cm h) × SEE cross section (cm per device) (1)
The 6 000 n/cm per hour flux is a nominal value for the cosmic ray neutrons with energy
> 10 MeV, at 40 000 ft (12,2 km) altitude and 45° latitude. It shall be adjusted for different
altitudes and latitudes using the data tables in Annex D of IEC 62396-1:2012. For RAMs
especially, a great deal of SEU cross section data has been published, allowing users of the
standard to estimate the SEU rate, and some SEU cross section data is also available for
microprocessors and FPGAs.
The same Equation (1) shall be used for SEB rates in high voltage devices provided that SEB
cross sections are known for specific devices operated at a specified voltage. This part of
IEC 62396 recommends the use of Equation (1) for calculating SEB rates even though it is
recognized that this is conservative. There is very little published data on the SEB cross
sections, but the data that does exist [1], [4] suggests that the SEB cross section is
significantly reduced at lower neutron energies compared to e.g. 200 MeV. The most suitable
facilities for measuring SEB cross sections are spallation sources with maximum energy
above 200 MeV. Thus the minimum neutron energy threshold for calculating the SEB rate
(energy at which the SEB cross section is similar to that at high energy, e.g., 200 MeV) is
100 MeV. The available SEB cross section data is documented in Clause 6.
For avionics applications it should be recognized that assuming the high voltage electronics
will be operating at a single voltage is unrealistic. First, the airplane power system is expected
to experience power transients and spikes during flight. The transients typically last for less
than 1 s, during which time V could increase from 270 V to 350 V. The cascading power
ds
spikes can increase the voltage to even higher levels above nominal, although the duration is
much shorter, usually < 100 µs.

62396-4 © IEC:2013(E) – 9 –
Secondly, the operating details of the high voltage equipment are important in evaluating its
susceptibility to SEB. For example, in the case of certain types of DC-DC converters, the
voltage across the MOSFET is not continuous. The MOSFET cycles between off and on
states, and the voltage across the MOSFET during the off state is higher than during the on
state due to an inductive voltage associated with the mechanism that allows the magnetic
energy to be discharged [11]. The highest voltage across the MOSFET is during the off state,
but its magnitude depends on several operational parameters of the converter (e.g., V , V
in out
and output current). Thus, a true evaluation of the SEB susceptibility should take into
consideration the voltage across the MOSFET throughout the complete duty cycle and set of
operating conditions of the converter. Other high voltage components may have similar
variations in their operating conditions.
The use of the WNR beam to perform accelerated SEB testing of very high voltage devices [1]
has spurred considerable additional testing of the very high voltage devices (> 2 kV) by the
microelectronics companies that manufacture these devices. This testing has used the WNR
facility as well as other sources of neutrons. The other neutron sources include the quasi
mono-energetic neutron beam created by a proton beam on a lithium target (e.g., at the
Svedberg Laboratory in Sweden) or high elevation research stations (Sphinx Laboratory at
Jungfraujoch, Switzerland, 11 300 ft (3,4 km) high). However, the results of such testing are
usually considered proprietary and not published, or if a few are published, it is in a little
known publications [12], [13]. In addition, for these vendors having ground level applications,
their results are often put into the format of a FIT (failure in time) rate, 1 FIT being equal to
one failure in 10 device hours of operation [1].
The key points are that none of these very high voltage devices are relevant to avionics
applications currently and that some vendors treat their SEB data as proprietary. However,
the familiarity of these HV electronics vendors with the overall SEB issue from neutrons
means that if they also manufacture lower voltage devices, devices that are relevant to
avionics applications, they may have SEB data, but this data will often be considered
proprietary.
6 Relevant SEB data and applying it to avionics
6.1 SEB data from heavy ion testing is not relevant
It is surprising that when it comes to SEB induced by high-energy protons and neutrons, there
are only a limited number of IEEE papers [1], [2], [4] that discuss this subject and present
useful data, despite the fact that the first evidence of proton-induced SEB in MOSFETs was
documented in a 1988 report [3]. Since the 1988 report, almost all data published concerning
SEB
...