Soldering Techniques - Fluke Autoranging CombiScope PM3370B Service Manual

CORRECTIVE MAINTENANCE PROCEDURES
8.4

SOLDERING TECHNIQUES

8.4.1 General soldering techniques
Working method:
- Carefully unsolder the soldering tags of a semi-conductor one after the other.
- Remove all superfluous soldering material. Use desolder braided wire; ordering code:
4822 321 40042.
- Check that the leads of the replacement part are clean and pre-tinned on the soldering places.
- Place the replacement semiconductor exactly in the same position, and solder each lead to the
relevant printed conductor on the printed circuit board.
NOTE: The maximum permissible soldering time is 10 seconds during which the temperature of the
leads must not exceed 250 °C. The use of solder with a low melting point is recommended.
Take care not to damage the plastic encapsulation of the semiconductor (softening point of
the plastic is 150 °C).
ATTENTION: When you are soldering inside the instrument it is essential to use a low voltage
A suitable soldering iron is:
Mini soldering iron station, WECP-COD3 (regulated transformer) and Weller LR-20 (soldering iron).
Ordinary 60/40 solder with core and 35 ... 40 W pencil-type soldering iron can be used to do the
majority of the soldering. If a higher wattage-rating soldering iron is used on the printed circuit board,
excessive heat can cause the circuit wiring to separate from the base material.
8.4.2 Soldering micro-miniature semi-conductors
Because of the small dimensions of these SOT semi-conductors and the lack of space between the
components on the printed circuit board, it is necessary to use a miniature soldering iron with a pin-
point tip (max. diameter 1mm) to solder a SOT on to a printed circuit board.
Suitable soldering tools are:
- Mini soldering iron station, WECP-COD3 (regulated transformer) and Weller MLR-20 (mini
soldering iron).
- A hot-air solder tool: Leister Hot-Jet.
Next, the following materials are recommended:
- Soldering tin, diameter 0.8 mm, SnPb 60/40 with a Resin Mildly Activated (RMA) flux. Ordering
code: 4822 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 OSC296 (ordering code 4822 872 08407) for a complete discussion of
the soldering techniques for SMD's.
soldering iron, the tip of which must be grounded to the chassis of the oscilloscope.
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