Table of Contents
Advertisement
SAFETY CONSIDERATIONS
I
GENERAL - This product and relation documentation must
be
reviewed for familiarization with safety markings and instruc-
tions before operation,
CAUTION
SAfETY SYMBOLS
Instruction manual symbol: the product
will be marked with this symbol when it is
necessary for the user to refer to' the i n-
struction manual in order to protect the
product against damage,
Indlcatt.·s hazardous \'oltages,
Indicatt.·s t'arth 'groundl terminal Isome-
tmlt.'s lIsed in manual to indicate circuit
('OmnlOn connt.·cted to grounded chassisl,
The WARNING sign denotes a hazard.
It
calls attention to a procedure. prac-
tice. or the like. which. if not correctly
performed or adhered to. could result
in injury. Do not proceed beyond a
WA RNING sign until the indicated
conditions are fully understood and
met.
The
('A
l"rI()!\; sign d('not('s a hazard
It
calls attt.·ntion to an opt'r"t ing pron·dure.
practin·. or tht.·like. which. ifnot cOITectl.\'
pl'ri'ol'llwd or adht'red to. could result in
damagt.· to or dt.·structlon of part or all of
tht.· pl'Oduct. Do not proceed heyond a
CA
l'TION sign until the Indicated ·condi-
tions are
full~'
undt.·rstood and met.
CAUTION
STATIC SENSITIVE DEVICES
When any two materials make contact, their surfaces
are crushed on the atomic level and electrons pass
back and forth between the objects, On separation,
one surface comElS away with excess electrons (nega-
tively charged) while the other is electron deficient
(positively
chargt~d).
The level of charge that is devel-
oped depends upon the type of material. Insulators
can easily build up static charges in excess of 20,000
volts. A person working at a bench or walking across a
vii
floor can build up a charge of many thousands of
volts. The amount of static voltage developed de-
pends on the rate of generation of the charge and the
capacitance of the body holding the charge. If the
discharge happens to go through a semiconductor
device and the transient current pulse is not effective-
ly diverted by protection circuitry, the resulting cur-
rent flow through the device can raise the tempera-
ture of internal junctions to their melting points.
MOS structures are also susceptible to dielectric
damage due to high fields. The resulting damage can
range from complete destruction to latent degrada-
tion. Small geometry semiconductor devices are espe-
cially susceptible to damage by static discharge.
The basic concept of static protection for electronic
components is the prevention of static build-up where
possible and the quick removal of already existing
charges. The means by which these charges are re-
moved depend on whether the charged object is a
conductor or an insulator. If the charged object is a
conductor such as a metal tray or a person's body,
grounding it will dissipate the charge. However, if the
item to be discharged is an insulator such as a plastic
box/tray or a person's clothing, ionized air must be
used.
Effective anti-static systems must offer start-to-
finish protection for the products that are intended
to be protected. This means protection during initial
production, in-plant transfer, packaging, shipment,
unpacking and ultimate use. Methods and materials
are in use today that provide this type of protection.
The following procedures are recommended:
1.
All semiconductor devices should be kept in "antis-
tatic" plastic carriers. Made of transparent plastics
coated with a special "antistatic" material which
might wear off with excessive use, these inexpen-
sive carriers are designed for short term service
and should be discarded after a period of usage.
They should be checked periodically to see if they
hold a static charge greater than 500 volts in
which case they are rejected or recoated, A 3M
Model 703 static meter or equivalent can be used
to measure static voltage, and if needed, carriers
(and other non-conductive surfaces) can be recoat-
ed with "Staticide" (from Analytical Chemical
Laboratory of Elk Grove Village, Ill.) to make them
"antistatic. "
2. Antistatic carriers holding finished devices are
stored in transparent static shielding bags made by
3M Company. Made of a special three-layer mate-
rial (nickle/polyester/polyethylene) that is "antis-
tatic" inside and highly conductive outside, they
provide a Faraday cage-like shielding which pro-
tects devices inside. "Antistatic" carriers which
contain semiconductor devices should be kept in
these shielding bags during storage or in transit.
Advertisement
Table of Contents
