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SEMI S22-1103a © SEMI 2003, 2005 25 16.2.2 Printed Circuit Boards Printed wire assemblies of flame-retardan t material should be allowed in place of conductor assem blies provided that they are withi n electrical enclo…
SEMI S22-1103a © SEMI 2003, 2005 24
15.3 Location and Mounting
15.3.1 All components within electrical enclosures should be placed and oriented so that they can be identified
without moving components or the wiring. Components should not be mounted on panels that are intended to be
removed for routine maintenance.
EXCEPTION 1: Moveable panels are acceptable if they are well bonded, secured to the equipment, and the supply
wires are routed such that moving the slide panel will not deteriorate their insulation.
EXCEPTION 2: Devices supplied with non-hazardous voltages and power levels may be mounted on normally
removable panels.
15.3.2 Components should be located to permit inspection for correct operation and routine maintenance without
dismantling equipment or parts of the machine.
15.3.3 Where a special tool is necessary to remove an electrical component, the tool should be supplied.
15.3.4 Where electrical components are connected through plug-in arrangements, their association should be made
clear by type (shape), marking, or reference designation, whether singly or in combination.
15.3.5 Plug-in devices that are handled during normal operation should be provided with non-interchangeable
features where the lack of such a feature can result in an unacceptable risk.
15.3.6 Creepage and clearances should meet the criteria of basic insulation between primary parts and the earthed
electrical enclosure for the working voltages involved (See Appendix 1 Tables A1-12 and A1-13).
15.3.7 When components that handle hazardous voltage and hazardous power are mounted on swing panels, the
swing panels that have those components mounted on them should swing open adequately to provide access. The
wiring that flexes during servicing should be provided with additional mechanical protection at all points where it is
flexed.
EXCEPTION: Wiring that passes the flexing test described in ¶22.16 does not need to have additional mechanical
protection.
15.4 Component Identification — Components should be labeled on the surface of the panel where the component
is mounted so the component may be identified from the documentation as discussed in §21.
EXCEPTION: Engineering documentation that provides a layout of the electrical enclosure with component
identification may serve this function.
16 Conductors and Cables
16.1 General Conductors and cables should be rated for the voltage and load current at which they are used.
Proper overcurrent protection in accordance with Sections 10 and 11 should be provided. Conductor insulation or
covering should also be rated to withstand any external influences that they may be subjected to under normal
operating conditions, as well as under single fault conditions (e.g., the presence of water, corrosive substances,
mechanical stress, and thermal stress).
16.2 Conductor Construction Wire conductors should be constructed of copper. Conductors should be
constructed of materials compatible with the materials and ratings of the devices they will be connected to and the
environment in which they will be used.
NOTE 45: Most of the components used in the semiconductor industry are not compatible with aluminum wiring.
16.2.1 Conductor Ampacity Conductors should meet one of the following considerations:
c) be certified by an accredited testing laboratory to be used in a manner other than that described in Tables A1-1
through A1-6 in Appendix 1 and used in accordance with their certification; or
d) be sized in accordance with Tables A1-1 through A1-6 in Appendix 1.
EXCEPTION: Conductors that have been demonstrated to be adequate for their application by testing in accordance
with IEC 61010.
SEMI S22-1103a © SEMI 2003, 2005 25
16.2.2 Printed Circuit Boards Printed wire assemblies of flame-retardant material should be allowed in place of
conductor assemblies provided that they are within electrical enclosures and are mounted in such a way as to
minimize flexing or stress. All printed circuit boards should have a flammability rating of V-1 or better (See IEC
60707 or UL 94); or a rating of FR-4 or FR-5 (ANSI/IPC 2221).
16.2.3 Bus Bars Non-insulated bus bars should be sized according to Appendix 1, Table A1-7.
16.2.4 Insulation The insulation on each conductor should be rated to take into account:
a) the electrical, thermal and mechanical strength for the maximum voltages and currents that can be applied to
the conductor,
b) the worst environment (e.g., temperature, pressure, humidity, vibration and pollution) where the conductor
may be routed, and
c) resistance to flame spread.
16.2.5 Natural rubber and materials containing asbestos should not be used as insulation.
16.2.6 Hazards Associated with Insulation
Where the insulation of conductors and cables can constitute hazards
due to the propagation of fire or the emission of toxic or corrosive fumes under single fault conditions, additional
protections should be provided or alternative conductor or cable assemblies should be considered.
16.2.7 Dielectric Strength of Wire and Cable Insulation A test mark from an accredited testing laboratory on the
wire or cable may be used to demonstrate suitability of the wire when it is used in accordance with its voltage rating.
An alternate means of compliance can be obtained by the test described below. Cables and wires operating at a
nominal voltage of higher than 50 V AC or 120 V DC should withstand a dielectric test voltage of 1000 V plus two
times their working rated voltage or 2000 V AC for 5 minutes, whichever is higher. This test for dielectric
breakdown should be applied between the wire or cable conductor and foil wrapped around the conductor insulation.
16.2.8 Insulation Strength The mechanical strength and thickness of the insulation should be such that the
insulation cannot be damaged in normal operation or as a result of reasonably foreseeable abuse, so as to fail to
provide adequate protection.
16.3 Flexible Cables
16.3.1 Flexible cords, cables and power cord sets are permitted inside electrical enclosures for internal wiring:
a) when equipped with an attachment plug and powered from a receptacle outlet inside the electrical enclosure to
connect one or more assemblies to primary power inside the enclosure; and
b) when the insulation on the individual conductors of the flexible cord or cable are suitable for the application
without consideration of the outer jacket insulation; and
c) when the AC flexible cord, AC power cord set, AC receptacles, and AC appliance coupler are all used in
accordance with their ratings.
NOTE 46: Power cord sets are preferred over non-detachable cords to facilitate replacement of assemblies without modifying or
removing the flexible cord.
16.3.2 Exposed flexible cords and cables installed along the structure of the equipment or system or in the chassis
of the machinery is allowable when they are not subject to physical damage from normal operations. Exposed
cables should be installed to closely follow the surface and structural members of the machinery.
17 Wiring Practices
17.1 Connections and Routing
17.1.1 All connections should be secured against accidental loosening. Terminals should be sized appropriately for
the conductors that are being terminated. The connection of two or more conductors to one terminal is allowable
only where the terminal is designed and identified for that purpose. All soldered connections should be
mechanically secured before soldering. Terminals on terminal blocks should be clearly identified to correspond with
markings on the diagrams, or terminal identification should be provided in system manuals or another equivalent
means of identification should be provided.
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17.1.2 The installation of flexible conduits and cables should be such that liquids drain away from the fittings.
17.1.3 Terminal blocks should be mounted and wired so that the internal and external wiring does not cross over the
terminals.
17.1.4 Conductors and cables should be connected from terminal to terminal without splices.
17.1.5 Where circuits operate at different voltages, the conductors of each voltage level should be separated by
suitable barriers, or routed separately and secured, or all conductors grouped or bundled together should be insulated
for the highest voltage present in the group or bundle.
17.1.6 Conductors smaller than 1/0 AWG should not be connected in parallel to the same terminations to attain the
necessary ampacity.
17.1.7 Conductors should not be exposed to temperatures greater than their temperature rating. If the wire
termination has a lower temperature rating than the conductor, the lower temperature rating should be used to
evaluate the suitability of the conductor.
17.2 Terminal Lugs Terminal lugs should be utilized according to the following:
a) Ring Tongue Desired for all terminations not routinely disconnected for access and service;
b) Flat Spade not desired for terminating hazardous potentials or hazardous energy levels and not suitable for
bonding or earthing (grounding).
c) Flanged Spade not desired for earthing except on a captive screw;
d) Female Tab
Desired only for terminations to fixed male tabs on components or panels.
17.3 Attachment Plugs, Cord Connectors, and
Receptacles If an unacceptable risk can result from
misconnection, then receptacles and cord connectors
should not accept an attachment plug with a different
voltage or current rating.
17.3.1 Only female cord connectors should be used to
supply power.
17.3.2 Receptacles should be rated for at least 125
percent of the maximum rated design load (current)
intended for the circuit.
17.3.3 Each receptacle should be individually bonded
to the protective earthing system.
17.3.4 Series connection of the protective conductor
from receptacle to receptacle should not be used.
17.3.5 Convenience receptacles accessible from the
exterior of the equipment should be protected by a
ground-fault circuit-interrupter (GFCI).
NOTE 47: A receptacle that is used to supply power to a
subsystem is not a convenience receptacle.
17.4 Temporary Power Taps Temporary power taps
(commercial power strips) should not be used for
installation in or on equipment.
EXCEPTION: Permanently installed fixed power strips
that are suitable for industrial equipment are acceptable
if they have been evaluated by an accredited testing
laboratory for this application.
Figure 1
Terminal Lugs