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SEMI S22-1103a © SEMI 2003, 2005 9 a) taking all reasonable steps to avoi d high temperatures which might cause i gnition; b) controlling the position of combustible materials in relation to possible ignition sources; c)…
SEMI S22-1103a © SEMI 2003, 2005 8
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.
SEMI S22-1103a © SEMI 2003, 2005 10
8.4.3 Components should be securely mounted according to the conditions of their certification, if applicable, and
their manufacturer’s instructions.
8.5 Electrical Supply
8.5.1 The equipment should be designed to operate safely when connected to its specified electrical supply.
8.5.2 Interruptions in the facilities electrical supply should not lead to an increased risk of fire, electric shock, or
other hazardous conditions.
8.6 Un-interruptible Power Supplies (UPS) This subsection applies to UPSs with outputs greater than 30 Volts
rms, 42.4 Volts peak, 60 Volts DC or 240 Volt-Amperes (VA). Whenever a UPS is provided with the equipment, its
location and wiring should be clearly described within the relevant manufacturer supplied documentation that covers
installation and maintenance.
8.6.1 Power from the UPS should be interrupted when any of the following events occur:
a) the emergency off actuator (EMO button) is pushed; or
b) the equipment main disconnecting means is opened.
EXCEPTION: Upon emergency off (EMO) activation, the UPS may continue to supply power to the EMO circuit,
safety related devices, and data/alarm logging computer systems as described in the exception clauses of ¶13.3.3.
8.6.2 The UPS may be physically located within the footprint of the equipment provided that the UPS is within its
own electrical enclosure, which may be the enclosure provided with the UPS and considered in the certification of
the UPS. The UPS circuits may also be supplied from a facility source outside of the equipment served. If this is
the case, then all the considerations discussed for facilities main disconnecting means in §9 should be taken into
account for power supplied to the UPS circuits.
8.6.3 The UPS should be certified by an accredited testing laboratory.
8.6.4 The UPS wiring and terminals should be identified as “UPS Supply Output”, or equivalent, at each connection
point where the UPS wiring may be disconnected.
8.7 Operating Environment — The electrical equipment should be suitable for the environment in which it is
intended to be used.
8.8 Electromagnetic Compatibility (EMC) A system malfunction, as a result of the presence of anticipated
electromagnetic disturbances that will be present in the end use environment, should not result in an unacceptable
risk. Products that are compliant with either SEMI E33 or the EMC Directive (89/336/EEC) are considered to be
compliant with this criterion.
8.9 Contaminants
8.9.1 Electrical equipment should be adequately protected against the entrance of solid bodies and liquids likely to
be present that may increase the risk of electric shock or fire as a result of a single-point failure or reasonably
foreseeable operational error.
8.9.2 Electrical insulation should be protected against chemical environments that may lead to deterioration, or be
capable of withstanding the environments to which it will be exposed.
8.10 Ionizing and Non-ionizing Radiation Personnel should be adequately protected against the hazards
associated with ionizing and non-ionizing radiation. Compliance to the ionizing and non-ionizing radiation sections
of SEMI S2 serves as verification of compliance.
8.11 Vibration, Shock, and Bump Protection should be provided against likely unsafe consequences from the
effects of vibrations, shocks and bumps caused by operation of the equipment, or disturbances of this type that will
be present in the semiconductor manufacturing, testing, and assembly environment.
NOTE 20: See the SEMI S2 seismic section for considerations.
8.12 Transportation and Storage Packing for shipment should prevent damage from humidity, vibration, and
shock that may affect the safety of the equipment.