IEC PAS 61340-5-6:2022

IEC PAS 61340-5-6 ®
Edition 1.0 2022-06
PUBLICLY AVAILABLE
SPECIFICATION
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Electrostatics –
Part 5-6: Protection of electronic devices from electrostatic phenomena –
Process assessment techniques
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IEC PAS 61340-5-6 ®
Edition 1.0 2022-06
PUBLICLY AVAILABLE
SPECIFICATION
colour
inside
Electrostatics –
Part 5-6: Protection of electronic devices from electrostatic phenomena –

Process assessment techniques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.99; 29.020 ISBN 978-2-8322-3943-8

– 2 – IEC PAS 61340-5-6:2022 © IEC 2022

CONTENTS
FOREWORD . 4
1.0 PURPOSE, SCOPE, LIMITATION, and EXPERIENCE LEVEL REQUIRED . 9
1.1 Purpose . 9
1.2 Scope . 9
1.3 Limitation . 9
1.4 Experience Level Required . 9
2.0 ReferenceD PUBLICATIONS . 9
3.0 DEFINITIONS . 10
4.0 Personnel Safety . 10
5.0 Measurement Techniques FOR ESd Risk Assessment . 10
6.0 ESD Robustness of ESDS ITEMS used in Processes . 12
6.1 ESD Withstand Currents of Single Devices (Components) . 13
6.1.1 Human Body Model . 13
6.1.2 Discharge of Charged Conductors . 13
6.1.3 Charged Device Model . 14
6.2 ESD Withstand Currents of Electronic Assemblies . 14
6.2.1 Discharge of Charged Personnel . 14
6.2.2 Discharge of Charged Conductors . 14
6.2.3 Discharge of Boards/Systems . 15
7.0 Process Assessment Flow . 15
7.1 General Considerations . 15
7.2 Manual Handling Steps . 16
7.2.1 Introduction . 16
7.2.2 Parameter Limits for ESD Process Assessment in Manual Handling Steps . 16
7.2.3 Detailed ESD Risk Assessment Flow . 17
7.3 Conductors . 18
7.3.1 Introduction . 18
7.3.2 Parameter Limits for Process Assessment of Conductors . 19
7.3.3 Detailed ESD Risk Assessment Flow . 19
7.4 Charged ESDS Items . 20
7.4.1 Introduction . 20
7.4.2 Parameter Limits for Process Assessment of Charged ESDS Items . 20
7.4.3 Detailed ESD Risk Assessment Flow . 21
7.5 Risks Due to Process-Required Insulators . 23
7.5.1 Introduction . 23
7.5.2 Parameter Limits for Process Assessment of Process-Required Insulators . 23
7.5.3 Detailed ESD Risk Assessment Flow . 24
7.6 Process Assessment by ESD Event Detection . 25
7.6.1 Introduction . 25

7.6.2 General Procedure . 26
7.6.3 Detailed ESD Risk Assessment Flow . 26

ANNEX A (INFORMATIVE): Measurement TECHNIQUES And EQuipment . 28
A.1 General Considerations . 28
A.2 Measurements of Grounding . 28
A.3 Measurements of Electrostatic Fields . 31
A.4 Measurements of Charges . 32
A.5 Measurements of Electrostatic Voltages . 33
A.6 Measurements of Discharge Events . 37
A.7 Measurements of Discharge Currents . 39
ANNEX B (INFORMATIVE) – PREPARATION: WHAT IS NECESSARY TO .
PREPARE AN EFFECTIVE PROCESS EVALUATION? . 45
B.1 Measurement of Temperature, Humidity, and Basic Electrostatic Conditions . 45
B.2 Further Hints for Preparation . 45
ANNEX C (INFORMATIVE) – Risk Assessment and Mitigation . 46
ANNEX D (INFORMATIVE) – ExampleS for defining limits in process assessment for .
Risks Due to Charged Personnel . 47
ANNEX E (INFORMATIVE) – Example for CDM risk assessment in a .

semiconductor manufacturing line . 49
ANNEX F (INFORMATIVE) – Bibliography . 53
ANNEX g (INFORMATIVE) – revision History for ANSI/ESD Sp17.1 . 54

Table 1 – Overview of Possible Measurement Equipment Used for Different Scenarios .
to Assess ESD Risk . 11
Table 2 – Peak Current Ranges of CDM Discharges of Small and Large Verification Modules for
Oscilloscopes with a Bandwidth of 1 GHz and 6 GHz According to ANSI/ESDA/JEDEC JS-002 . 44
Table 3 – Recommended Measurement Locations During Process Assessment in Assembly .
(Pre-Assembly) of Devices . 49
Table 4 – Recommended Measurement Locations During Process Assessment in Device Testing . 50

Figure 1 – Direct (Best Correlation) and Indirect (Least Correlation) Measurements .
to Assess an ESD Risk . 12
Figure 2 – Flow to Assess ESD Risk Induced by Personnel . 18
Figure 3 – Flow to Assess the ESD Risk Induced by Conductors . 20
Figure 4 – Flow to Assess the ESD Risk Induced by Charged ESDS Items . 22
Figure 5 – Flow to Assess the ESD Risk Induced by Process-Required Insulators . 25
Figure 6 – Flow to Assess the ESD Risk by Detecting the Electromagnetic Radiation .
Using ESD Event Detectors or Antennas and Oscilloscopes . 27
Figure 7 – Examples of Current Probes . 40
Figure 8 – Example of a 4-GHz Pellegrini Target . 42
Figure 9 – Commercially Available CDM Test Head Used for Discharge Current Measurements . 43
Figure 10 – Discharge Current Measured in the Field and During Device Qualification [8] . 47
Figure 11 – Examples of Measurements During Semiconductor Assembly and Testing . 50
Figure 12 – Schematic of Possible CDM-Like Scenarios During Device Testing . 52

– 4 – IEC PAS 61340-5-6:2022 © IEC 2022

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROSTATICS –
Part 5-6: Protection of electronic devices from electrostatic phenomena –
Process assessment techniques
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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A PAS is an intermediate specification made available to the public and needing a lower level
of consensus than an International Standard to be approved by vote (simple majority).
IEC PAS 61340-5-6 has been processed by IEC technical committee 101: Electrostatics.
It is based on ANSI/ESD SP17.1-2020. The structure and editorial rules used in this publication
reflect the practice of the organization which submitted it.
The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft PAS Report on voting
101/654/DPAS 101/663/RVDPAS
Following publication of this PAS, the technical committee or subcommittee concerned may
transform it into an International Standard.
A list of all parts in the IEC 61340 series, published under the general title Electrostatics, can
be found on the IEC website.
This PAS shall remain valid for an initial maximum period of 2 years starting from the publication
date. The validity may be extended for a single period up to a maximum of 2 years, at the end
of which it shall be published as another type of normative document, or shall be withdrawn.

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 PAS 61340-5-6:2022 © IEC 2022

ESD Association Standard Practice for
the Protection of Electrostatic Discharge
Susceptible Items –
Process Assessment Techniques
Approved November 17, 2020
EOS/ESD Association, Inc.
(This foreword is not part of EOS/ESD Association, Inc. Standard Practice ANSI/ESD SP17.1-2020)

FOREWORD
This standard practice describes a set of methodologies, techniques, and tools that can be used to
characterize a process where ESD sensitive (ESDS) items are handled. This document's procedures
are meant to be used by those possessing knowledge and experience with electrostatic measurements.
This document provides methods to determine the level of ESD risk that remains in the process after
ESD protective equipment and materials are implemented.
These test methods' objective is to identify if potentially damaging ESD events are occurring or if
significant electrostatic charges are generated on people, equipment, materials, components, or printed
circuit board assemblies (PCBA) even though there are static control measures in place.
Sensitivities of items are characterized by industry-standard ESD testing and rated by their withstand
voltages. This document is intended to provide methods to determine whether items of a given withstand
voltage are at risk in the process.
The wide variety of ESD protective equipment and materials and the environment in which these items
are used may require test setups different from those described in this document. Users of this standard
practice may need to adapt the test procedure and setups described in Annex A to produce meaningful
data for the user’s application.
Organizations performing these tests will need to determine if on-going process characterization is
necessary, and if so, the time interval between observations. It may also be important to make these
observations when new products are introduced or when process changes occur. Examples of process
changes may include tools, fixtures, equipment, new items/products, and additional manufacturing steps.
The topics below are not addressed in this document:
• Program Management: see ANSI/ESD S20.20 Protection of Electrical and Electronic Parts,
Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)
• Compliance Verification: see ESD TR53-01 Compliance Verification of ESD Protective Equipment
and Materials
• Troubleshooting: ESD TR53-01
• ESD Program Certification: see ANSI/ESD S20.20 Certification Program at www.esda.org
This document was designated ANSI/ESD SP17.1-2020 and approved on November 17, 2020.

ESD Association Standard Practice: A procedure for performing one or more operations or functions that may
or may not yield a test result. Note, if a test result is obtained it may not be reproducible.

– 8 – IEC PAS 61340-5-6:2022 © IEC 2022

At the time ANSI/ESD SP17.1-2020 was prepared, the 17.0 Subcommittee had the following members:
Reinhold Gaertner, Co-Chair Wolfgang Stadler, Co-Chair
Infineon Technologies AG Intel Deutschland GmbH
Christopher Almeras Donn Bellmore Stephen Blackard
Raytheon Advanced ESD Services + Finisar Corporation
Rodney Doss David N. Girard Toni Gurga
Samtec, Inc. Staticon Support Services, Inc. Reliant ESD
Ginger Hansel John Kinnear Vladimir Kraz
Dangelmayer Associates IBM OnFILTER, Inc
Chuck McClain Ronnie Millsaps Andrew Nold
Micron Technology, Inc. Teradyne
Dale Parkin Keith Peterson Alan Righter
Seagate Technology Missile Defense Agency Analog Devices
James Roberts Jeff Salisbury Arnold Steinman
ZF Friedrichshafen AG Finisar Corporation Electronics Workshop
David Swenson Chin Sing Tay
Matt Strickland
Affinity Static Control Suzhou TA&A Ultra Clean
The Boeing Company
Consulting, LLC Technology Co., Ltd.
Arman Vassighi Toni Viheriaekoski Nobuyuki Wakai
Intel Corp. Cascade Metrology Toshiba
Scott Ward Terry Welsher Joshua Yoo
Texas Instruments, Inc. Dangelmayer Associates Core Insight, Inc.
Craig Zander
Transforming Technologies LLC
ESD Association Standard Practice for the Protection of Electrostatic Discharge Susceptible
Items – Process Assessment Techniques

1.0 PURPOSE, SCOPE, LIMITATION, AND EXPERIENCE LEVEL REQUIRED
1.1 Purpose
The purpose of this document is to describe a set of methodologies, techniques, and tools that can be
used to characterize a process where ESD sensitive (ESDS) items are handled. The process
assessment covers risks by charged personnel, ungrounded conductors, charged ESDS items, and
ESDS items in an electrostatic field.

1.2 Scope
This document applies to activities that manufacture, process, assemble, install, package, label, service,
test, inspect, transport, or otherwise handle electrical or electronic parts, assemblies, and equipment
susceptible to damage by electrostatic discharges. This document does not apply to electrically initiated
explosive items, flammable liquids, or powders. The document does not address program management,
compliance verification, troubleshooting, or program manager/coordinator certification. In this version of
the document, risks due to electromagnetic sources that produce AC fields are not considered.

1.3 Limitation
No detailed description of the processes and measurement techniques is given. An example of a simple
risk assessment of a discharge from a charged human body is described in Annex D.
Due to the sampling nature in this document's procedures, deficiencies may exist that are not detected
at the time the measurements are made. The measurements described are valid only at the time the
measurements are made and may or may not change with time.
NOTE: Environmental parameters such as temperature and relative humidity (RH) may significantly impact the
measurement results.
1.4 Experience Level Required
The procedures in this document are for use by personnel possessing advanced knowledge and
experience with electrostatic measurements. The interpretation of the results from the measurements
described in this document requires significant experience and knowledge of the physics of ESD and
the process.
2.0 REFERENCED PUBLICATIONS
Unless otherwise specified, the following documents of the latest issue, revision, or amendment form a
part of this standard to the extent specified herein:
ESD ADV1.0, ESD Association Glossary of Terms
ANSI/ESD S20.20, For the Development of an Electrostatic Discharge Control Program for –Protection
of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive
Devices)
IEC61340-5-1, Electrostatics–Part 5-1: Protection of Electronic Devices from Electrostatic Phenomena
– General Requirements
EOS/ESD Association, Inc. 7900 Turin Road, Bldg. 3, Rome, NY 13440, Ph: 315-339-6937; www.esda.org
IEC – International Electrotechnical Commission, www.iec.ch

– 10 – IEC PAS 61340-5-6:2022 © IEC 2022

3.0 DEFINITIONS
The terms used in the body of this document are in accordance with the definitions found in ESD ADV1.0,
ESD Association’s Glossary of Terms available for complimentary download at www.esda.org.
process. A unique combination of tools, materials, methods, and people engaged in producing a
measurable output.
NOTE: The term “process” can refer to a complete assembly process or a minor step, such as a pick-and-place
process.
process assessment. A methodological framework to evaluate the process capabilities regarding
defined parameters.
process capability. Parameters for different ESD risks that allow safe handling of items with a given
ESD withstand voltage.
4.0 PERSONNEL SAFETY
THE PROCEDURES AND EQUIPMENT DESCRIBED IN THIS DOCUMENT MAY EXPOSE
PERSONNEL TO HAZARDOUS ELECTRICAL CONDITIONS. USERS OF THIS DOCUMENT ARE
RESPONSIBLE FOR SELECTING EQUIPMENT THAT COMPLIES WITH APPLICABLE LAWS,
REGULATORY CODES, AND BOTH EXTERNAL AND INTERNAL POLICY. USERS ARE
CAUTIONED THAT THIS DOCUMENT CANNOT REPLACE OR SUPERSEDE ANY
REQUIREMENTS FOR PERSONNEL SAFETY.
GROUND FAULT CIRCUIT INTERRUPTERS (GFCI) AND OTHER SAFETY PROTECTION SHOULD
BE CONSIDERED WHEREVER PERSONNEL MIGHT COME INTO CONTACT WITH ELECTRICAL
SOURCES.
ELECTRICAL HAZARD REDUCTION PRACTICES SHOULD BE EXERCISED, AND PROPER
GROUNDING INSTRUCTIONS FOR EQUIPMENT MUST BE FOLLOWED.
THE RESISTANCE MEASUREMENTS OBTAINED THROUGH THE USE OF THIS TEST METHOD
SHALL NOT BE USED TO DETERMINE THE RELATIVE SAFETY OF PERSONNEL EXPOSED TO
HIGH AC OR DC VOLTAGES.
5.0 MEASUREMENT TECHNIQUES FOR ESD RISK ASSESSMENT
Specific test equipment is needed for specific measurement techniques to perform a proper risk
assessment. The appropriate instruments are required to measure if a material fulfills given
requirements. Additionally, the charging status of an object or even the discharge current waveform of
this object must be measured. Each process step might need a different technique and tool to measure
whether there is a risk to the ESDS items being processed. This chapter describes the basic
measurement techniques that can be used to assess various risks in different scenarios.
Table 1 lists tools that can measure parameters to assess whether there is a risk for the items handled
in a process. Measurement of the object's actual discharge under consideration is desirable but difficult
to accomplish in a production environment. The discharge waveform then could be compared with the
qualification waveform, and the risk could easily be assessed. However, this is often difficult to achieve,
especially in a production environment. Therefore, indirect parameters must be assessed, such as
charging of the object, although this parameter does not tell the user whether a catastrophic discharge
is happening. If it is not possible to measure charging, measurements such as resistance to ground may
need to be used (see Figure 1). A detailed description of all the test methods is given in Annex A.
NOTE: All measurements should be performed with verified test equipment to ensure that the measurements are
not influenced by defective equipment.

Table 1 – Overview of Possible Measurement Equipment Used
for Different Scenarios to Assess ESD Risk
Parameter
Personnel Conductors Insulators Devices/PCBs
(Document)
Resistance
Grounding
measurement Multimeter – –
(Annex A.2)
apparatus
Electrostatic
fields Field meter Field meter Field meter Field meter
(Annex A.3)
Faraday cup Faraday cup
Electrometer
Charge
Electrometer Faraday cup Electrometer
(Annex A.4)
Current probe
Current probe Current probe
Charged Plate
Monitor
a a
ESVM ESVM
Electrostatic
a
Walking Test Kit
ESVM
b b
voltage HIDVM HIDVM
a
c
ESVM
Field meter
c c
(Annex A.5)
Field meter Field meter
b
HIDVM
c
Field meter
Resistance
Resistance of
Resistance Resistance
measurement
material
measurement – measurement
apparatus,
contacting ESDS
apparatus apparatus
item (Annex A.6)
Multimeter
Antenna with Antenna with Antenna with
oscilloscope oscilloscope oscilloscope
Discharge events
–
(Annex A.7)
ESD event ESD event ESD event
detector detector detector
Current probe
Discharge
Current probe Current probe
currents Pellegrini target –
Pellegrini target CDM test head
(Annex A.8)
CDM test head
a
ESVM = non-contact electrostatic voltmeter
b
HIDVM = contact-based high-impedance digital voltmeter
c
used as non-contact electrostatic voltmeter

– 12 – IEC PAS 61340-5-6:2022 © IEC 2022

Figure 1 – Direct (Best Correlation) and Indirect (Least Correlation) Measurements to Assess an ESD Risk

6.0 ESD ROBUSTNESS OF ESDS ITEMS USED IN PROCESSES
For a successful process assessment, one or more of the electrical/physical parameters listed in Table 1
and the process assessment flows in Section 7.0 must be measured and compared against set limits.
However, the parameters' limits depend on the process, measurement methodologies and techniques,
and ESD robustness of the ESDS items. Therefore, it is not possible to define one limit for the
parameters of all ESDS items and processes. It is particularly important to distinguish between handling
a single integrated circuit (IC) and electronic assemblies. For example, a single device with relatively
high robustness against a charged device model (CDM) discharge may be more susceptible to damage
once installed on a PCBA. The PCBA has a larger capacitance than the single device, which may result
in more severe stress (higher peak current, higher charge).
Defining limits requires some knowledge about the ESD robustness of the ESDS item that is being
handled in the process and knowledge about the process itself. As the ESD robustness of the ESDS
item in this process is better known, and the process is analyzed in greater detail, more accurate limits
can be determined. Otherwise, reasonable assumptions must be made.
The discharge event is the most critical point of a process or application, and determining the discharge
current is the most direct parameter for the risk assessment. Comparing the discharge current as
measured in the process with the withstand current obtained during ESD qualification tests is
theoretically the best approach. However, discharge currents from qualification data are often unknown
and not easily obtainable directly in process measurements. Hence, more indirect parameters must be
used for ESD risk assessment. In most cases, the charging and the ESD robustness voltage of the
ESDS item are used for the assessment. Each uncertainty in the ESD robustness of the ESDS item or
the knowledge about the process reduces the accuracy and, consequently, results in a higher effort
combined with a possible larger margin that has to be taken to exclude any risk.
Section 6.1 discusses how the withstand current of the different discharge scenarios can be either
derived from qualification data or from limits defined in ANSI/ESD S20.20 or IEC 61340-5-1. A similar
discussion of withstand currents of electronic assemblies is outlined in Section 6.2. These withstand
currents are the basis for assessing the limits of the measurement parameters listed in Table 1 and the
process assessment flows in Section 7.0.

6.1 ESD Withstand Currents of Single Devices (Components)
6.1.1 Human Body Model
Component manufacturers use the human body model (HBM) test to determine ESDS items' sensitivity
to discharge from a simulated charged person. Current HBM qualification procedure is described in the
standard ANSI/ESDA/JEDEC JS-001 [1]. Typically, in HBM qualification, the HBM discharge voltage
VHBM is reported, not the HBM discharge current IHBM, which is the real damaging parameter. However,
can be derived from the HBM withstand voltage rather accurately by
the HBM withstand current IHBM
IHBM = VHBM/RHBM with RHBM = 1500 ohms being the serial resistance in the HBM discharge network.
• If the HBM robustness in terms of withstand voltage VHBM of the component is known, the withstand
current can be calculated by I = VHBM/RHBM. For example, a component with an HBM robustness
HBM
of 1000 volts has an HBM withstand current of I = 1000 volts/1500 ohms ≈ 670 milliamperes.
HBM
NOTE: If the HBM robustness of the component is unknown, but similar products with the same power supply
concept and set of I/O cells have been qualified according to HBM, this qualification value can be used as HBM
robustness.
• If the HBM robustness of the component is not known, 100 volts HBM robustness can be used as
a reasonable lower limit of ESDS items that can be handled in an EPA according to ANSI/ESD
S20.20. For most of the components, this value might be quite conservative, but still can be achieved
rather easily in a process. The maximum HBM withstand current IHBM is then 67 milliamperes.
• If the component's HBM robustness is unknown, and the application does not tolerate any ESD-
related failures, the assumed HBM robustness could be lowered; however, a lower HBM robustness
might require additional ESD control measures.

6.1.2 Discharge of Charged Conductors
The risk of a component being damaged by the contact to a charged conductor while at least one pin of
the component is on a different potential (typically grounded) was previously thought to correlate to the
“machine model” (MM) test. However, MM is no longer used for component ESD qualification due to
severe deficiencies in repeatability and reproducibility. Therefore, MM qualification results are typically
not available.
NOTE: A discharge of a charged conductor to a floating device is modeled by CDM because it is the closest
approximation.
• If HBM qualification is available, HBM thresholds divided by ten could act as a reasonable approach
to correlate with a charged conductor's discharge into a component on a different potential.
According to [2], the correlation between V and V is in the range of 3:1 to 30:1. According to
HBM MM
[3], the MM withstand current is 1.75 amperes per 100 volts. As an example, if the HBM robustness
of a component is 500 volts, the corresponding MM withstand voltage can be estimated to be V
MM
= VHBM/10 = 50 volts, and the MM withstand current to be IMM = 1.75 amperes x (VMM/100 volts) =
880 milliamperes.
• If the HBM robustness of the component is not known, 35 volts MM robustness against a discharge
of a charged conductor can be used as a reasonable lower limit of ESDS items that can be handled
in an EPA according to ANSI/ESD S20.20. For most of the components, this value might be quite
conservative, but still can be achieved rather easily in a process. A withstand voltage of 35 volts
corresponds to approximately 600 milliamperes MM withstand current.
• If the component's HBM robustness is unknown, and the application does not tolerate any ESD-
related failures, the assumed MM robustness could be lowered; however, a lower MM robustness
might require additional ESD control measures.

– 14 – IEC PAS 61340-5-6:2022 © IEC 2022

6.1.3 Charged Device Model
The phenomenon of a charged component or a component in the presence of an electric field being
discharged when contacted by a conductive item is referred to as a charged device model event. The
current version of this model is described in the standard ANSI/ESDA/JEDEC JS-002 [4]. For assessing
the risk of damage in this CDM scenario, the CDM robustness of the component must be known.
• If the CDM robustness in terms of withstand current ICDM of the component is known, the withstand
current can be used and correlated directly to the discharge current in the process. For example, if
the qualification withstand current ICDM of the IC is 3.0 amperes, discharge currents of 3.0 amperes
in the process should not damage the component.
• If only the CDM withstand voltage VCDM is known, the CDM withstand current ICDM must be
estimated. For components with small capacitance (< 10 pF), the CDM current correlates to the
CDM voltage with ~1.0 ampere/100 volts, which means I = 1.0 ampere x (V /100 volts),
CDM CDM
knowing that this is extremely conservative for very small components. For example, for
components with larger capacitance (~50 pF), the correlation is I /V = 2.0 amperes/100 volts,
CDM CDM
that means ICDM = 2.0 ampere x (VCDM/100 volts). The capacitance of the component in the CDM
tester can be approximated from a comparison with the size of the modules used for the verification
of CDM qualification testers.
NOTE: If the component’s CDM robustness is unknown, but similar components with the same power supply
concept, set of I/O cells, and the same die size and package have been qualified according to CDM, this
qualification value can be used as a realistic approximation of the CDM robustness.
• If the CDM robustness of the component is not known, 200 volts CDM robustness (corresponds to
2.0–4.0 amperes CDM current) can be used as a reasonable lower limit of ESDS items that can be
handled in an EPA according to ANSI/ESD S20.20. Experience has shown that a 100-volt CDM
robustness (corresponding to 1.0–2.0 amperes CDM current) is sufficient to handle components in
most of the processes without ESD damage; however, it requires advanced charge and discharge
control techniques in the process.

6.2 ESD Withstand Currents of Electronic Assemblies
6.2.1 Discharge of Charged Personnel
For electronic assemblies/systems, in most cases, no HBM qualification is performed. However, as the
current and energy of an HBM event do not change whether discharged to a single device (component)
or an electronic assembly, the worst-case approximation is that all the discharge current is dissipated
through one component. The robustness of the entire system is then determined by the component with
the lowest HBM robustness.
For the HBM robustness of the single component, the same considerations as in Section 6.1.1 apply.

6.2.2 Discharge of Charged Conductors
For risks of electronic assemblies by charged conductors, the same considerations are valid as for HBM
risk of electronic assemblies (Section 6.2.1). As the discharge current and energy of a charged
conductor does not change whether discharged to a component or an electronic assembly, the worst-
case approximation is that all the discharge current is dissipated through one component. The
robustness of the entire system is then determined by the component with the lowest HBM robustness.
For the robustness of the single component, the same considerations as in Section 6.1.2 apply.
NOTE: Charged cables and the risk of a cable discharge event (CDE) can also be assessed as charged isolated
conductors.
6.2.3 Discharge of Boards/Systems
The worst-case HBM risk for electronic systems could be correlated to the component’s HBM robustness.
In contrast, for the discharge of a charged board (charged board event, CBE) or system or a
board/system in an electric field, no easy correlation to any component robustness qualification exists.
The reason for this is that even if on a board, a component pin is contacted directly, the charge stored
at the board is typically significantly higher compared to the charge stored on a single component.
Knowing the discharge peak current is required to establish any worst-case approximation. No
qualification method exists yet for boards and electronic assemblies.
As a very simple worst-case approximation, the maximum allowed peak discharge current of a board
(that is, the current flowing through the conductive item that contacts the board) can be estimated from
the component’s CDM threshold currents, see Section 6.1.3. As the charge stored at the board is larger
than the charge stored on a single component, resulting in a wider full-width half maximum of the
discharge current waveform and consequently more severe stress, a safety factor should be included.
From experimental data, a safety factor of two seems to be a reasonable estimate [5]. For example, if
all components on the board or in the system do not fail 3 amperes CDM current, very likely, a board
discharge current of 1.5 amperes will not cause damage to the components on the board. This worst-
case approximation requires that the discharge current in the process can be measured, which is rarely
the case.
If the discharge current of the board cannot be measured, the only reasonable approach is to avoid “all”
possible discharges or limit the charging of the board/system to an exceptionally low and safe value.
From data in the literature (for example, see [13] and references therein), a worst-case approximation
could be to limit the charging of the board/system to one-tenth of the minimum CDM robustness of all
devices. For example, if the minimum CDM robustness of all components is known or assumed to be
200 volts, then the charging of the board should not exceed 20 volts.
NOTE: Another option is to limit the discharge current by contacting the ESDS item with a dissipative or insulative
material. See the assessment flows in Sections 7.4 and 7.5.

7.0 PROCESS ASSESSMENT FLOW
7.1 General Considerations
Standards such as ANSI/ESD S20.20 and IEC 61340-5-1 give guidance on implementing an ESD
control program for handling ESDS items in EPAs. ESD failures can still happen even in well-equipped
EPAs, as reported in many publications (see references in [6]). A detailed risk assessment is needed
for the various process steps to avoid failures coming from the production process. A process
assessment needs to cover risks induced by charged personnel, ungrounded conductors, charged
insulators, and charged ESDS items.
Although automated processes dominate many production areas, manual process steps still exist,
especially at process transition points and manual PCBA handling processes. Therefore, assessing
operator grounding and charging of personnel is necessary. Standards such as ANSI/ESD STM97.2 [7]
provide good guidance on measuring an operator's body voltage using footwear/flooring grounding.
Without such an assessment, ESD protective elements might not fit together and are not as effective.
Isolated conductors can charge and discharge into ESDS items. Hence, it is also important to care for
isolated conductors when handling ESDS items. These failures can be avoided by removing charges
from all conductors, especially those in direct or close contact with the ESDS item. Following ANSI/ESD
S20.20, the maximum voltage difference between an ESDS item and a conductor shall not exceed
35 volts to limit possible discharge currents between the conductor and the ESDS item to an acceptable
level.
Issues with CDM-type discharges are becomin
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