Solutions Strategies and Innovations
Static Solutions Inc. - Ohm - Stat RT - 1000 Information
Foreword
(This
foreword
is
not
part
of
ANSI/ESD
Association
Standard
S20-1.29099)
This standard covers the requirements necessary to design, establish, implement, and maintain an
Electrostatic Discharge (ESD) Control Program for activities that: manufacture, process, assemble, install,
package, label, service, test, inspect or otherwise handle electrical or electronic parts, assemblies and
equipment susceptible to damage by electrostatic discharges greater than or equal to 100 volts Human
Body Model (HBM). When handling devices susceptible to less than 100 volts HBM, more stringent ESD
Control Program Technical Requirements may be required, including adjustment of program Technical
Element Recommended Ranges. This document covers the control program requirements and offers
guidance to protect and handle ESD sensitive (ESDS) items, based on the historical experience of both
military and commercial organizations. References include, ESD Association, US Military and ANSI
approved standards for material properties and test methods. The fundamental ESD control principles
that form the basis of this document follow:
A. All conductors in the environment, including personnel, must be bonded or electrically
connected and attached to a known ground or contrived ground (as on shipboard or on
aircraft). This attachment creates an equipotential balance between all items and personnel.
Electrostatic protection can be maintained at a potential above a “zero” voltage ground
potential as long as all items in the system are at the same potential.
B. Necessary non-conductors in the environment cannot lose their electrostatic charge by
attachment to ground. Ionization systems provide neutralization of charges on these
necessary non-conductive items (circuit board materials and some device packages are
examples of necessary non-conductors). Assessment of the ESD hazard created by
electrostatic charges on the necessary non-conductors in the work place is required to ensure
that appropriate actions are implemented, commensurate with risk.
C. Transportation of ESDS items outside an Electrostatic Protected Area (hereafter referred
to as “Protected Area”) requires enclosure in static protective materials, although the type of
material depends on the situation and destination. Inside a Protected Area, low charging and
static dissipative materials may provide adequate protection. Outside a Protected Area, low
charging and static discharge shielding materials are recommended. While these materials
are not discussed in the document, it is important to recognize the differences in their
application.
Any relative motion and physical separation of materials or flow of solids, liquids, or particle-laden gases
can generate electrostatic charges. Common sources of ESD include personnel, items made from
common polymeric materials, and processing equipment. ESD can damage parts by direct contact with a
charged source or by electric fields emanating from charged objects that induce a charge on grounded or
capacitively coupled to ground sensitive items. It is possible to determine device and item susceptibility
by exposure to simulated electronic equivalent discharge circuits. The level of sensitivity determined by
test using these models may not necessarily relate to the level of sensitivity in a real life situation.
However, they are used to establish a baseline of susceptibility data for comparison of devices with
equivalent part numbers from different manufacturers. Three different models are used for
characterization of electronic components - Human Body Model (HBM), Machine Model (MM), and
Charged Device Model (CDM). It is important to recognize that these models, if used alone, are difficult to
apply in terms of specification setting activities. Examples of ESDS parts are microcircuits, discrete
semiconductors, thick and thin film resistors, hybrid devices and piezoelectric crystals.
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