ESD Control Standards:
Setting up an ESD control program
This paper will help an ESD Coordinator,
Manager or Engineer apply the proper ESD standards when developing
an ESD Control Program. For an ESD Control program to be effective
it should be designed around the ElectroStatic Discharge Sensitive
(ESDS) devices it is protecting; and most importantly, it should
be supported at all levels within the company, from the company
officers through all managers to the operators and technicians.
This top-down approach, when fully adapted, ensures that all the
elementary elements of the program are properly deployed.
One of the main reasons companies deploy
an ESD Control program is to save money. Increased throughput and
decreased scrap can yield a ROI (Return On Investment) of up to
3000% per year for successfully deploying an ESD Control program
. A secondary reason is to comply with their customers’ demands
and ISO 9000 programs. Whatever reason, setting up and implementing
an ESD Control program will almost always pay for itself within
the first year.
There is an array of ESD Control products
on the market. Which products should you choose when developing
your ESD Control program? The products that you select are determined
by how you have defined your ESD control program.
I STANDARDS from the Ground
There are about 60 of the more commonly used standards
for ESD control listed in Tables I and II. These standards and
specifications originate from many different organizations and
serve different purposes, as are outlined below.
Military & Government (FTM, MIL, OSHA)
Commercial Organizations (AATCC, ANSI, ASTM,
AT&T, CECC, IEC, IPO, ISO)
Associations (EIA, ESDA)
PURPOSE or FUNCTION
Standard testing and classification of semiconductor
Standard test methods
Standards for qualifying ESD Control programs
Standards for monitoring ESD Control programs
Technical reports or advisories for understanding
the standards or technology
If your company supplies various electronic
components or is a board house, your customers may require you to
follow certain prescribed standards to which they adhere. If you
are establishing a new ESD control program then the Electrostatic
Discharge Association’s Standards listed in Tables I through IV
will aid you to establishing the proper criteria.
The Electrostatic Discharge Association
(ESDA) standards are the most comprehensive and up-to-date industry
accepted standards for the control of ESD. Their current standards
are listed in Table I by application.
Six years ago, the ESD Association
became an American National Standards Institute (ANSI) accredited
standards development organization, and this attainment is reflected
in some of the ESDA standards carrying the ANSI accreditation.
The first place to look for guidance
in developing your ESD Control program would be from within the
ESDA standards. As of February 1998, the ESDA has refined their
definitions of standards by specifying the following categories.
Standard (S) is a precise statement
of a set of requirements to be satisfied by a material, product,
system or process that also specifies the procedures for determining
whether each of the requirements is satisfied.
Standard Test Method (STM) is a definitive
procedure for the identification, measurement and evaluation
of one or more qualities, characteristics or properties of
a material, product, system or process that yield a reproducible
Standard Practice (SP) is a procedure
for performing one or more operations or functions that may
or may not yield a test result.
Technical Report (TR) is a collection
of technical data or test results published as an informational
reference on a specific material, product, system or process.
Furthermore, as a new standard evolves,
it becomes ready for industry review and is classified as a Draft
Standard and can be represented by the designation Draft Standard
(DS), Draft Standard Practice (DSP), Draft Standard Test Method
(DSTM), and Draft Technical Report (DTR). And lastly, an Advisory
(ADV), which may be replaced by the Technical Report (TR), can be
educational in nature and consists of general information and guidelines
deemed helpful to the industry in understanding the use of standards
and related technology.
The ESD Association has recently accepted
the task of refining MIL-STD-1686 Electrostatic Discharge Control
Program for Protection of Electrical and Electronic Parts, Assemblies
and Equipment as a commercial document and currently has a draft
standard ESD DS20.20-1998. The ESDA is also assisting the update
of EIA-625, Requirements for Handling Electrostatic-Discharge-Sensitive
The starting point of a sound program is to classify
the sensitivity to ESD damage of the devices you need to protect.
Classification of these devices should include all simulation
models (HBM, MM, and CDM, refer to the ESD STM5 series in Table
I) that will properly characterize the devices' sensitivity when
handled at various locations within the facility.
Realize that there may be different sensitivities
at different locations within the facility.
The ESDA standards that aid the sensitivity
testing process are ESD STM5.1-1998, ANSI/ESD S5.2-1994, ESD
DS5.2-1996, and ESD DS5.3.1-1996. These documents are the
most recent in the industry.
The Military standards that can be used to
determine device ESD sensitivity MIL-HDBK-263B, MIL-STD-883D
Method 3015.7, MIL-STD-750C/4 Method 1020, MIL-STD-785
The IEC standards to help classify device
sensitivity are CISPR 24 (1997-09) and IEC-61000-4-2 (1995).
ANSI has a document, ANSI C63.16, that can
aid in device sensitivity classification.
If you do not classify the devices
then you can assume the worst case for all 3 models, (Classes 0,
M0, C0 - refer to the ESD STM5 series standards in Table I), making
the program design critical and expensive.
Once the ESD device sensitivities for the various
areas in the facility have been determined then this information
can be mapped over the complete facility and will act as a guide
to designing the ESD control program.
Now, the location/sensitivity map of
the facility needs to be expanded upon by determining what standards
you will use to evaluate the success and monitor the program’s progress.
This map should also consider the transportation systems and traffic
flow of the sensitive devices between various working areas. Additional
design criteria to ensure device protection that needs to be broadened
are listed as follows.
Minimize voltage or field exposure (remove
non-essential charge generators)
Minimize voltage or field exposure (use of
protective packaging during transportation or storage)
Minimize voltage or field exposure (from machine
to device contact, e.g., automated equipment)
Exposed surfaces and their resistance (controlled
discharge times and use of dissipative work surface materials)
Grounding (power ground distribution) for
common point grounds/work surfaces
Grounding (floors – traffic areas)
Grounding (personnel – wrist straps/foot grounders/smocks/gloves)
Use of air ionization for essential non-grounded
or insulative materials/equipment/tools
Environmental controls (temperature and humidity)
Training of employees within various affected
areas (by far one of the most important factors)
IV Selecting General Product
Criteria for each Area
Which standard(s) should you reference when building
your ESD Control program from scratch, updating or evaluating
your current program? When you look to build an ESD-safe workstation,
you need to know what industry-wide acceptability criteria to
Table IV will help aid the design and
development of an ESD control program for each area using either
the ESD ADV-2.0-1994 or the MIL-STD-1686. The former is more recent
at this time. Table III lists various ESD Control products and the
associated ESDA Standards that can be used to qualify them.
As an example, an ESD Sensitive (ESDS)
workstation that is designed for worst case criteria may have the
following ESD Control products: an ESD floor; grounded floor mats
with use of ESD footwear (such as foot grounders); grounded and
monitored table mats covering all exposed surfaces; a common point
ground with monitored wrist strap connections; and air ionizers
covering all areas on the work surface to which the devices would
be exposed. In addition, all exposed insulators and metal surfaces
would be replaced with grounded dissipative materials; all non-essential
items, especially insulators, would be removed the ESDS area; and
most importantly, the ESDS workstation would have ESD Control Trained
operator(s) at the helm.
Starting from the ground up, your
floor would be the first place to start. One of the most important
characteristics of an ESD floor is its ability to conduct charges
to ground. The second most important aspect is its anti-static
property. One of the main mechanisms of charge generation is triboelectric
generation or tribocharging. Some examples of tribocharging are
people walking along a floor and carts carrying sensitive devices
rolling across a floor. Depending on where the materials in contact
with the floor are in the triboseries, voltages of over 30,000
Volts can be attained. If a floor has the property of being anti-static,
tribocharging becomes a much smaller concern. The standards documents
to help choose a floor are ANSI/ESD S7.1-1994, AATCC Step Test
- Method 134-1979, ANSI/EIA-625-1994, MIL-STD-1686, MIL-HDBK-263B,
and the AT&T Electrostatic discharge Control Handbook.
Typically protection on an ESDS device
should start at receiving, continue to inventory storage, and
then travel through its production flow usually from one workstation
to the next before ending up in shipping. All throughout its handling,
the device should be handled by grounded personnel. The easiest
way to ground people who travel from one station to the next,
delivering or picking up sensitive materials, is through mobile
grounding. Wearing foot grounders (one on each foot) in conjunction
with a conductive floor is one way to ensure that the operator
is grounded and protected from delivering or receiving an ESD
event. There are several ESDA standards to help in the testing
and verification of foot grounders and shoes: ESD DSTM54.1-1997,
ESD DSTM54.2-1997, and ESD S9.1-1995.
The surfaces where ESDS devices are
handled should be both conductive (in the dissipative range) and
properly grounded to the equipment grounding conductor to be an
effective ESD control element. There are several materials to
choose from such as rubber mats, vinyl mats, both single and multi-layered
and FRP and Micastat® for rigid or permanent bench surfaces.
Conductive metal work surfaces should be discontinued or covered
with a dissipative material because it is highly susceptible to
causing an ESD event from a metal-metal contact. It is very important
to control your discharge time by minimizing the energy transfer
by employing resistive materials to ground . The ESDA standards
to help characterize a work surface are ESD STM4.2-1998 and ESD
The human being can be the most dynamic
part of a working environment and consequently should be considered
one of the most important objects to ground. Wrist straps, a conductive
wristband with a connecting ground cord, is the most popular and
effective way to ground a person. Wrist straps should always be
properly employed when working with ESDS devices. The ESDS standard
EOS/ESD S1-1987 can aid in qualifying your wrist straps before
Materials that must stay with the
ESDS work area but are neither conductive nor groundable should
be treated with air ionization. Ionizers come in several types,
the most popular is the corona discharge air ionizer. Corona discharge
air ionizers can have emitters that are powered by AC, DC or pulsing
DC high voltage. Air ionizers can be qualified by applying the
ESDA standards ANSI-EOS/ESD, S3.1-1991ADV3.2-1995, and ESD SP3.3-1998.
Transportation & Packaging
ESDS devices should always be stored
in an enclosed antistatic shielding bag or conductive closed tote
or bin when not being handled. This includes inventory storage,
transportation, and WIP. Further precautions during transportation
include using dissipative carts with conductive wheels or drag chains
in conjunction with a conductive floor when transporting ESDS devices
in their shielded containers. The standards to help characterize
and qualify packaging materials are ANSI/ESD S11.31-1994 for shielding
bags, ANSI/EOS/ESD S8.1-1993 for proper use of package markings,
ANSI/EIA-541-88 and ANSI/EIA-583-91 for packaging materials.
III-ESD PROTECTIVE PRODUCTS & RELATED ESDA STANDARDS
Determining the product sensitivities within the
facility and then mapping this information helps in choosing the
right materials to keep each work area under control. Using the
ESDA or other related Standards will help your ESD Control program
comply with industry-accepted requirements and procedures that
govern the materials, products, systems or processes. Acceptability,
repeatability, and dependability can be expected from an ESD Control
program that employs a good design using the appropriate standards
along with proper training and monitoring.
ESD Program Management, G. Theodore
Dangelmayer, Van Nostrand Reinhold, NY, NY, Chpt. 14, 1990
The ESD Association, 7900 Turin Road, Bldg.
3, Suite 2, Rome, NY 13440-2069, http://www.eosesd.org
MIL-STD-1686B, Department of the Navy, Defense
Printing Service Detachment Office, Philadelphia, PA, 31 December
FOR EXTERNAL COLORED TEXT BOX
There is always some confusion between
the terms conductive and dissipative. Conductive can imply at least
two different things: (1) the basic property of being able to move
charges along a surface and (2) the range in ESD Control that differentiates
very conductive materials (classified as "conductive") from lesser
conductive materials (classified as "dissipative"). A "dissipative"
material is conductive in that it will move charges along its surface.
A "dissipative" material also has more resistance to the charge
flow and will move these charges slower than a "conductive" material
will, but much faster than an "insulative" material. Figure 1 graphically
displays the ESD Control resistive ranges of "conductive", "dissipative"
and "insulative". In ESD Control, one of the main keys of this control
is to control the charge flow (current) during a discharge.
Increasing the time for an ESD discharge will result in a reduction
of the peak energy transferred over any given point in time, which
minimizes the chance for an ESD event to occur and cause damage
to a sensitive device. This is best accomplished with a conductive
material that has sufficient resistance. The resistance range considered
for this type of control starts at the high end of the "conductive"
range through a good part of the "dissipative" range, refer to Figure
About the Author
Ryne C. Allen is the technical manager
at ESD Systems, a division of Desco Industries, Inc. (DII). Previously,
he was chief engineer and lab manager at the Plasma Science and
Microelectronics Research Laboratory at Northeastern University.
Mr. Allen is an NARTE-certified ESD control engineer and the author
of 27 published papers and articles. He is a member of the ESD Association
and an active ADCOM associate member of the Northeast Local Chapter.
He graduated from Northeastern University with B.S.E.E, M.S.E.E.,
and MBA degrees. ESD Systems, 19 Brigham St., Unit 9, Marlboro,
MA 01752-3170, (508) 485-7390, resume: http://ryne.hotresume.net/,