E. Newberg, President, MicroStat Laboratories
A significant investment can be made when
purchasing products for an ESD safe work area.
In many cases, thousands of dollars can be wasted purchasing
items that won’t work as described.
After spending many years purchasing products for
semiconductor and disk drive manufacturing operations, the author has
learned that it is critical to purchase items that have been tested by
an in-house laboratory or an independent laboratory to verify that
they meet the established requirements.
The requirements for equipment and materials used
in ESD-Safe work areas can be found in documents and specifications
published by the ESD Association.
This article will outline some of those documents and standards
published by the ESD Association.
The ESD Association has a very aggressive and
active standards writing group which publishes documents related to
ESD testing of devices, testing of workstations and materials, and
several detailed overview documents on work area and ESD program
development. After an
extensive writing and review process which includes submission to
industry for comments, the documents are submitted for ANSI approval.
The ESD Association has four levels of documents
that it publishes. ESD
Standards are given the ESD S XX.XX - YR designation.
Standards define 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. In many cases, these standards refer to the
other types of documents.
Standard Test Methods are given the ESD STM XX.XX
- YR designation. These
documents are aggressively reviewed and include round-robin test
matrices along with extensive data analysis to ensure repeatability
and reproducibility of data. STM’s give 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 test result.
Standard Practices are given an ESD SP XX.XX - YR
designation and are documents written in the same vein as STM’s
however are not as repeatable or reproducible for a variety of
reasons. An SP gives a
procedure for performing one or more operations or functions that may
or may not yield a test result. However
it should be noted that if a test result is obtained it is not
Advisories and Technical Reports are also
published by the ESDA. These
documents are a collection of technical data or test results published
as an informational reference on a specific material, product, system
or process. The advisories
are being phased out, and in most cases, are being replaced by
technical reports. Technical
reports are given an ESD TR XX – YR designation.
ANSI/ESD S20.20 is an overall document which
details how to develop and run a company-wide ESD control program.
S20.20 has been used in the industry now for over five years
and is well accepted. The
document has been adopted by the Department of Defense to replace the
now obsolete MIL-STD-1686. ANSI/ESD
S20.20 is available for free download from the ESD
Association’s web site. This
document should be downloaded and available for anybody who has or is
developing an ESD control program of any size.
For larger organizations, many ISO registrars also offer a
formal certification to ANSI/ESD S20.20.
A list of registrars available to perform these audits is
available at http://www.esda.org/s2020.html.
In addition to ESD S20.20, the ESD Association
also publishes a plethora of test methods, standards, advisory and
technical reports related to all areas of ESD control.
The standards writing organization, along with the documents
written by them are organized by working group.
The largest single working group which supplies
test methods to the semiconductor testing industry is WG-5.
WG-5 has published documents for testing semiconductor devices
for human-body model (STM5.1-2001), machine-model (STM5.2-1999),
Charged Device Model – Component Level (STM5.3.1-1999), Sensitivity
Testing Socketed Device (SDM) Component Level (SP5.3.2-2004),
Transient Latch-up Testing – Component Level (SP5.4-2004), and ESDS
Testing Transmission Line Pulse (SP5.5.1-2004).
There are also several draft standards out for review from this
committee (DSP 5.1.1-2005 & DSP 5.1.2-2005).
The balance of the working groups provide
documents that are more material or work-area related.
WG-1 had written S1.1-1998 “Wrist Straps,” and WG-2 has
published STM 2.1-1997, “Garments.”
WG-3 has published several documents on ionization, with
STM3.1-2000. being the
most established and only document on ionization in the industry.
SP3.3-2000 defines periodic verification of ionizers.
WG-4 has published S4.1-1997 and STM4.2-1998 on worksurfaces.
WG-6 is a dormant group, however the document
that they published, S6.1-2005 “Grounding,” is another
well-accepted document in the industry.
WG-7 has published S7.1-2005 “Resistive Characterization of
Materials - Floor Materials.” WG-8
is another dormant group but has another well-established document
S8.1-2001 “Symbols – ESD Awareness.”
In addition to this document, the symbols can be downloaded
(page down a bit to find the symbols).
WG-9 has published STM9.1-2001 “Footwear –
Resistive Characterization,” and SP9.2-2003 “Foot Grounders
Resistive Characterization.” They
also published STM97.1-1999 “Floor Materials and
Footwear–Resistance Measurement in Combination with a Person” and
STM97.2-1999 “Floor Materials and Footwear – Voltage Measurement
in Combination with a Person.” WG-10
has published SP10.1-2000 “Automated Handling Equipment.”
WG-11 (Packaging Materials) has published a
number of documents including the industry recognized STM11.11-2001
“Surface Resistance,” and STM11.12-2000 “Volume Resistance.”
They have also published STM 11.13-2004 “Two Point Resistance
Measurement,” and STM 11.31-2001 “Shielding for Bags.”
They also published an advisory (ADV11.2-1995) on Triboelectric
Charge Accumulation Testing. Perhaps
the most critical specification to come out of this group in recent
years is the newly released S541-2003 which replaces the EIA-541
Standard which was rendered obsolete by EIA several years ago.
WG-12 published STM12.1-1997 “Seating –
Resistive Measurement,” and WG-13 issued STM13.1-2000 “Electric
Soldering/Desoldering Hand Tools.”
Finally, WG-14 has recently published SP14.1-2004
“System Level Electrostatic Discharge (ESD) Simulator
Verification,” and WG-15 very recently issued SP15.1-2005 “In-Use
Resistance Testing of Gloves and Finger Cots.”
Clearly the best
supplier to the electrostatics industry for standards and
documentation for ESD control is the ESD
complete list of standards can be found in their Press
Catalog. Using these
standards and test methods is the single best investment that a user
of ESD supplies can make.