semi合集-English.pdf - 第7123页
SEMI S22-1103a © SEMI 2003, 2005 8 5.1.68 types of electrical work — define d by the electrical energy levels a pe rson is exposed to when perfo rming a task. All tasks that should be performed on a system fall into one …
SEMI S22-1103a © SEMI 2003, 2005 7
5.1.50 permanently connected equipment — equipment that is electrically connected to a supply by means of a
connection that may be detached only by the use of a tool.
5.1.51 pollution — any addition of foreign matter, solid, liquid or gas, that may produce a reduction of dielectric
strength or increase of surface resistivity.
5.1.52 pollution degree — for the purpose of evaluating clearances the following two degrees of pollution in the
micro-environment are recognized for use with this document:
5.1.52.1 pollution degree 1 — no pollution or only dry, non-conductive pollution occurs. The pollution has no
influence. Cleanroom Class 1000 or less.
NOTE 10: Cleanroom Class 1000 or less is pollution degree 1, however the pollution degree in a particular area in a given piece
of equipment may exceed pollution degree 1, even if the equipment is installed in a cleanroom class 1000 or less.
5.1.52.2 pollution degree 2 — normally only non-conductive pollution occurs. Occasionally, however, a temporary
conductivity caused by condensation is expected. Cleanroom Class greater than 1000.
NOTE 11: Cleanroom Class greater than 1000 is pollution degree 2, however the pollution degree in a particular area in a given
piece of equipment may exceed pollution degree 2, even if the equipment is installed in a cleanroom greater than 1000.
5.1.53 protective conductor — a conductor that provides electrical continuity between conductive components that
are not intended to be energized during normal operations and the equipment’s protective earthing conductor
terminal.
5.1.54 protective earthing conductor — a normally non-current carrying conductor connected between earth
(ground) at the source of supply and the protective earthing (grounding) terminal on the equipment enclosure.
5.1.55 protective earthing conductor terminal — a terminal bonded to conductive parts of an equipment enclosure
for safety purposes and intended to be connected to an external protective earthing (grounding) conductor (the
protective earthing conductor).
5.1.56 protective earthing system — the earthing (grounding & bonding) system connecting accessible conductive
parts of the equipment to an external earth (ground) at the source of supply. The protective earthing system may
include bonded structural members, bonding jumpers, the protective earthing conductor terminal on the equipment
and the protective earthing conductor in the incoming supply wiring to the equipment.
5.1.57 raceway — an enclosed channel of metal, or nonmetallic materials, designed expressly for holding wires,
cables, or busbars.
5.1.58 readily accessible — capable of being reached quickly for operation or inspection, without requiring
climbing over or removing obstacles or using portable ladders, chairs, etc.
5.1.59 reinforced insulation — a single layer of insulation that provides a degree of protection against electric shock
equivalent to double insulation.
5.1.60 risk — the expected losses from a mishap, expressed in terms of severity and likelihood.
5.1.61 safe shutdown condition — a condition in which all hazardous energy sources and hazardous production
materials are removed or suitably contained, unless this results in additional hazardous conditions.
5.1.62 safety circuit — a circuit whose intended function is to make the equipment safer. Interlocks, EMO circuits,
and other protective circuits are safety circuits.
5.1.63 service — unplanned activities intended to return equipment that has failed to proper working order (see also
maintenance).
5.1.64 severity — the extent of the worst credible loss (damage, injury, or release) from a mishap caused by a
specific hazard.
5.1.65 supplementary insulation — applied to basic insulation in order to ensure protection against electric shock in
the event of the failure of basic insulation.
5.1.66 testing — measurements or observations used to validate and document conformance to designated
criteria.
5.1.67 tool — an external device used to aid a person to perform a mechanical function.
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5.1.68 types of electrical work — defined by the electrical energy levels a person is exposed to when performing a
task. All tasks that should be performed on a system fall into one of the four following type categories of electrical
work:
5.1.68.1 type 1 — equipment is fully de-energized.
5.1.68.2 type 2 — equipment is energized. Energized circuits are covered or insulated with no exposed parts.
NOTE 12: Type 2 work includes those tasks where the energized circuits are, or may be, measured by placing probes through
suitable openings in the covers or insulators.
5.1.68.3 type 3 — equipment is energized. Energized circuits are exposed and inadvertent contact with un-insulated
energized parts is possible. Potential exposures are not greater than 30 Volts rms, 42.4 Volts peak, 60 Volts DC, and
240 volt-amps in dry locations.
5.1.68.4 type 4 — equipment is energized. Energized circuits are exposed and inadvertent contact with un-insulated
energized parts is possible. Potential exposures are greater than 30 Volts rms, 42.4 Volts peak, 60 Volts DC, 240
volt-amps in dry locations, or where induced or contact radio-frequency currents exceed the limits in SEMI S2.
5.1.69 wire guide — any method of mechanically securing wire or cable into a restrictive routing.
6 Alternate Methods of Conformity
6.1 The criteria in this document are based on harmonized basic electrical safety considerations. It is not the intent
of this document to be the only means of demonstrating the electrical safety conformance of semiconductor
manufacturing equipment.
6.2 Equipment that satisfies other national or international electrical product safety standards meets the intent of this
document.
7 Design Philosophy
NOTE 13: This section is intended to provide general design guidance to engineers; for specific design considerations see §8
through §22.
7.1 This document should be used during the electrical design, construction, and evaluation phases of
semiconductor manufacturing equipment. The intent of this safety guideline is to provide a design based electrical
document that will be useful to both design engineers and evaluators, in order to facilitate electrical safety in the
equipment.
7.2 Designers that understand these general principles of safety are more likely to design safe equipment. This
section is not an alternative to the more specific engineering considerations of this safety guideline, but is intended
to provide designers with an appreciation of the basic safety principles.
7.3 Electric shock is due to current passing through the human body. Currents on the order of a milliampere may
cause a reaction in people in good health, and may cause indirect mishap due to involuntary reactions. Higher
currents may have higher severity risks.
7.4 Design of equipment should provided protection of personnel from electric shock or arc flash/blast that may
result from reasonably forseeable single faults.
7.5 Service and maintenance personnel should be protected against inadvertent contact with electrical hazards.
7.6 Movable cord-connected equipment is considered to present a slightly increased risk of shock as well as
overheating, due to strain on the supply cord leading to damage to the connections, insulation, and the protective
earthing conductor. With portable cord-connected equipment, wear on the cord is more likely, and further hazards
could arise if the equipment were dropped.
7.7 Short-circuiting between phases and phase to ground of high current supplies or high capacitance circuits may
cause arcing or ejection of molten metal which may cause burns. Even low voltage circuits may be dangerous in this
respect. Protection should be provided by adequate separation, by shielding, or by using safety interlocks.
7.8 When temperatures that could cause a hazard result from overloads, component failure, insulation breakdown,
high resistance or loose connections, the risk of fire may be reduced by one or more of the following means:
SEMI S22-1103a © SEMI 2003, 2005 9
a) taking all reasonable steps to avoid high temperatures which might cause ignition;
b) controlling the position of combustible materials in relation to possible ignition sources;
c) limiting the quantity of combustible materials used;
d) using barriers, if necessary, to limit the spread of fire within the equipment beyond the immediate vicinity of the
ignition source; and/or
e) using suitable materials for the outer fire enclosures of the equipment.
NOTE 14: SEMI S14 may also be used for guidance on fire risk mitigation.
NOTE 15: Some fire retardant components or materials may be restricted or banned in certain jurisdictions.
7.9 Equipment should be designed to prevent injury due to excessive (high or low) temperatures of parts; to ensure
that the equipment is mechanically stable and structurally sound; to avoid the presence of operator accessible sharp
edges and points; and to provide adequate guarding or safety interlocking of hazardous moving parts.
7.10 Materials used in the construction of equipment should be selected and arranged so that they may be expected
to perform in a reliable manner, without a risk of energy hazard or electric shock developing, and such that they
would not contribute significantly to the development of a significant fire hazard.
NOTE 16: Some electrical components such as relays, electrolytic capacitors, batteries, solder, cathode ray tubes, finished
chassis, fluorescent lights and connectors may contain materials that are restricted or banned in certain jurisdictions.
8 General Considerations
8.1 The risks associated with the electrical design, construction, and operation of the equipment should be
considered as part of the overall safety assessment of the equipment. This assessment should include a fault analysis
with consideration given to, but not limited to, electric shock or fire and failures of components, subsystems, and
systems.
8.2 The following are some of the types of faults that should be considered:
a) faults and failures in the equipment’s circuits, and
b) possible human error associated with operator, maintenance, and service activities.
NOTE 17: This is not intended to be a comprehensive list of all possible types of faults.
8.3 The order of precedence for resolving identified hazards and satisfying equipment safety considerations should
be as follows:
a) design to eliminate hazards,
b) incorporate safety devices,
c) provide hazard alerts or warning signals, and finally
d) develop administrative procedures and training (administrative procedures may include the use of personal
protective equipment).
A combination of these approaches can also be used.
NOTE 18: See SEMI S2 for additional information.
8.4 Electrical Components
8.4.1 Where failure of components and assemblies could result in an unacceptable increase in risk of electric shock,
fire, or personnel injury, those components and assemblies should be certified by an accredited testing laboratory
and used in accordance with the manufacturer’s specifications and conditions of the certification, or otherwise
evaluated to the relevant component standard(s). This applies to components that handle hazardous voltage or
hazardous electrical power or are used in a safety circuit.
NOTE 19: Reference SEMI S2 for discussions of acceptable risk.
8.4.2 Components should be provided with overcurrent protection in accordance with §11.