Soldering Techniques; General Soldering Techniques; Soldering Micro-Miniature Semiconductors - Fluke 93 Service Manual

CORRECTIVE
MAOTENANCE
7 -SI
7.3
SOLDERING TECHNIQUES
7.3.1
General soldering techniques
Method:
•
Carefully
unsolder
the soldering leads of the semiconductor one
after
the
other.
•
Remove
all
superfluous soldering
material.
Use
de&oldering wick, ordering code;
4822
321 40042.
'
Verify that
the leads
of
the
replacement
part
are clean
and have
pre-tinned leads.
'
Place
the
replacement semiconductor
exactly
in
the
same
position,
and
solder
each
lead
to
the
relevant printed
circuit
padon
the
PC
B.
NOTE:
The
maximum
permissible soldering time
is
10
seconds
during
which the temperature
of the
leads
must
not
exceed 2SDC. The use
of solder with
a low
melting point
is
recommended
Take
care not
to
damage
the
plastic
encapsufation of the
semiconductor
(softening point
of
the pfastfc
is
1S0C).
CAUTION; When
you
are soldering inside the
Instrument
It
Is
essential to
use a low
voltage
soldering
Iron,
the
tip of
which
must be connected
to the
ground
of
the
Scope
Meter.
A
suitable soldering iron
is:
• Mini
solderirtg iron station,
WECP-COD3
(regulated transformer)
and
Weller LR-20
(soldering
Iron).
Ordinary 60/40
Cin/lead
solder with
flux
core
and
a35W
to
40W
pencil'
type soldering
Iron
can Pe used
to
do most
of the soldering.
If
a
higher wattage
soldering
Iron
Is
used
on
the
circuit
PCB,
excessive
heat
may
cause
the
circuit
wiring
to
separate from
the
PCB
Pass
material.
7.3.2
Soldering micro-miniature semiconductors
Because
of
the small
dimensions
of
these
SOT
semiconductors and
the lack of space between
the
components on the
PCB,
It
is
necessary
to
use
a miniature soldering
iron with
a
pinpoint
tip
(max.
diameter
1
mm.)
to solder a
SOT
onto a
PCB.
Suitable soldering tools are:
"
Mini soldering
Iron station.
WECP-COD3
(regulated transformer)
and
Welle
r
MLR
-20
(rm'nl
soldering
Iron).
-
A
hot-air solder
tool:
Leister Hot-Jet
Next, the
foliowing materials are
recommended:
•
Soldering
tin,
diameter
0.8
mm.,
SnPb
60/40
with
a Resin
Mildly
Activated
(RWA)
flux.
Ordering
code;
4S22 390
80133.
•
Desolder braided
wire.
Ordering
code 4822
321 40042.
-
Solder paste
26.
-
Non-corrosive and
Resin
Mildly Activated
(RMA)
flux-Colophony.
Ordering
code:
4822 390
50025.
Refer to the
Support
Bulletin
OSC
296
(ordering
code
4822 872
06407)
for
a complete
discussion
of
the soldering techniques
for
SMD's.