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
PCB.
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
ScopeMeter.
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.
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