A lecture on Soldering
Ⅱ. Pb-free Soldering
2. Materials of Pb-free tin solder composition
People have been researching many kinds of pb-free tin solder up to date. Now two kinds are commonly used in Japan.
One of them is a compound of stannum (Sn), silver (Ag) and copper (Cu). It is most commonly used Pb-free tin solder in Japan, featuring its good wettability. However, since it contains rare metals, such pb-free tin solder is very expensive.
Sn: about 96.5%; Ag: about 3% and Cu: about 0.5%
It also contains other trace elements
Most commonly used in Japan
Good wettability but expensive due to its containing silver
The other kind is a compound of stannum (Sn) and copper (Cu). It is less expensive compared with Sn-Ag-Cu, but stickier.
Recently, another kind of tin solder has been developed, i.e. “Sn-Cu+α”. Its wettability, fluidity and gloss have been improved due to some additional trace elements. Sometimes the tin-copper solder containing α-trace-elements is only called “tin-copper solder” which, however, may be confused with the solder without α-trace-elements. So “Sn-Cu+α” is used for the description to tell the distinction.
Sn: about 99%, Cu: about 0.7% and other trace elements
Compare with Sn-Ag-Cu, it is less expensive, but stickier.
Its wettability and gloss have been improved due to the addition of some trace elements.
Solder of Sn-Cu-α
For example: Stannum-copper-nickel-cadmium (Sn-0.7Cu-0.05Ni+Ge)
Any one of the above mentioned tin solders is pretty good in terms of wettability and reliability because of the improvements in soldering flux. Recently, as the price of silver has gone up, more and more users employ Sn-Cu solder.