R-238ASL (serv.man9). Touch Control Panel Assembly - Sharp Home Appliance Service Manual (repair manual). Page 4

R238A(SL)

9 – 4

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.

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.

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 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 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.

Indicates lead-free solder of tin, silver and copper