Precautions For Using Lead-Free Solder - Wolf MWD24-2 Service Manual

Drawer Microwave
Capacitor

PRECAUTIONS FOR USING LEAD-FREE SOLDER

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 suffix 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 40°C 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, (flow), 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 flow 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 tempera-
ture or turn off the iron when it is not required. Leaving different types of solder on the bit will cause contamina-
tion of the different alloys, which will alter their characteristics, making good soldering more difficult. 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.
(Models MWD24-2 / MWD30-2)
Red
Rectifier
White
Red
Chassis
Figure 4-1. Discharge Capacitor
Indicates lead-free solder of tin, silver and copper.
Before servic-
ing, capacitor
must be dis-
charged by
shorting con-
necting lead
of rectifier
against chas-
sis with an
insulated
screwdriver.
4-3
#813632 - Revision B - December, 2009
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