Wolf MWD24 Technical Service And Parts Manual page 29

1. Employing lead-free solder
The "Main PWB" of this model employs lead-free solder. This is indicated by the "LF" symbol printed on the PWB
and in the service manual. The suffi x letter indicates the alloy type of the solder.
Example:
2. Using lead-free wire solder
When repairing a PWB with the "LF" symbol, only lead-free solder should be used. (Using normal tin/lead alloy
solder may result in cold soldered joints and damage to printed patterns.) As the melting point of lead-free solder
is approximately 40oC higher than tin/lead alloy solder, it is recommend that a dedicated bit is used, and that the
iron temperature is adjusted accordingly.
3. Soldering
As the melting point of lead-free solder (Sn-Ag-Cu) is higher and has poorer wettability, (fl ow), to prevent damage
to the land of the PWB, extreme care should be taken not to leave the bit in contact with the PWB for an extended
period of time. Remove the bit as soon as a good fl ow is achieved. The high content of tin in lead free solder will
cause premature corrosion of the bit. To reduce wear on the bit, reduce the temperature or turn off the iron when it
is not required.
Leaving different types of solder on the bit will cause contamination of the different alloys, which will alter their
characteristics, making good soldering more diffi cult. It will be necessary to clean and replace bits more often
when using lead-free solder. To reduce bit wear, care should be taken to clean the bit thoroughly after each use.
Drawer Microwave
Figure 4-1 Discharging High Voltage Capacitor
PRECAUTIONS FOR USING LEAD-FREE SOLDER
Indicates lead-free solder of tin, silver and copper.
4-3
Access & Removal