--------------------------
RELIAB I
LlTY
TEST
DATA
4. PRECAUTIONS
4.1 Storage
To prevent deterioration
of
electrical characteristics, solder-
ability, appearance
or
structure, Hitachi recommends semicon-
ductor devices be stored as follows:
(I)
Store in ambient temperatures
of
5 to 30°C, with a relative
humidity
of
40 to 60%.
(2)
Store in a clean, dust- and active gas-free environment.
(3)
Store in conductive containers to prevent static electricity.
(4)
Store without any physical load.
(5)
When storing devices for an extended period, store in
an
unfabricated form,
to
minimize corrosion
of
pre-formed
lead wires.
(6)
Unsealed chips should be stored in a cool, dry,
dark
and
dust-free environment. Assembly should be performed
within 5 days
of
unpacking. Devices can be stored for up to
20
days in dry nitrogen gas with a dew point
at
-30° C
or
less.
(7)
Prevent condensation during storage due to rapid tempera-
ture changes.
4.2
Transportation
General precautions for electronic components are appli-
cable in transporting semiconduCtors, units incorporating semi-
conductors, and other similar systems. In addition, Hitachi
recommends the following:
(I) When transporting semiconductor devices
or
printed circuit
boards, minimize mechanical vibration and shock.
Use
con-
tainers
or
jigs which will not induce static electricity as a
result
of
vibration. Use
of
an electrically conductive con-
tainer
or
aluminum foil
is
recommended.
(2)
To prevent device deterioration from clothing-induced static
electricity, workers should be properly grounded while hand-
ling devices.
Use
of
a I M ohm resistor
is
recommended to
prevent electric shock.
(3)
When transporting printed curcuit boards containing semi-
conductor devices, suitable preventive measures against
static electricity must be taken. Voltage build-up can be
avoided
by
shorting the card-edge terminals. When a belt
conveyor
is
used, apply some surface treatment to prevent
build-up
of
electrical charge.
(4)
Minimize mechanical vibration and shock when trans-
porting semiconductor devices
or
printed circuit boards.
30
4.3
Handling
for
Measurement
Avoid static electricity, noise and voltage surge when meas-
uring
or
mounting devices. Precaution should be taken against
current leakage through terminals and housings
of
curve tracers,
synchroscopes, pulse generators, and DC power sources.
When testing devices, prevent voltage surges from the tester,
attached clamping circuit, and any excessive voltage possible
through accidental contact.
In inspecting a printed circuit board, power should not be
applied if any solder bridges
or
foreign matter
is
present.
4.4
Soldering
Semiconductor devices should not be exposed to high
temperatures for excessive periods. Soldering must be performed
consistent with temperature conditions
of
260°
C for
10
seconds,
350° C for 3 seconds, and
at
a distance
of
I to 1.5mm from the end
of
the device package.
A soldering iron with secondary voltage supplied through a
grounded transformer
is
recommended to protect against
leakage current.
Use
of
alkali
or
acid flux, which may corrode the
leads,
is
not recommended.
4.5
Removing Residual Flux
Detergent
or
ultrasonic removal
of
residual flux from circuit
boards
is
necessary to ensure system reliability. Selection
of
detergent type and cleaning conditions are important factors.
When chloric detergent
is
used for plastic packaged devices,
care must be taken against package corrosion. Extended
cleaning periods and excessive temperature conditions can cause
the chip coating to swell due to solvent permeation. Hitachi
recommends use
of
Lotus and Dyfron solvents. Trichloroeth-
ylene solvent
is
not suitable.
The following conditions are advisable for ultrasonic
cleaning:
Frequency:
28
to
29
k Hz (to avoid device resonation)
• Ultrasonic output:
15W/f
• Keep devices from making direct contact with power
generator
• Cleaning time: Less than
30
seconds.
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