When the tin-lead alloy is mutually melted at a ratio of 63:37, the temperature rises to 183 °C, and the junction of solid and liquid will appear. The temperature at this point is called the eutectic temperature, which is the lowest temperature among the different tin and lead ratio solder melting points. of. The corresponding alloy composition is Sn (62.7%) and Pb (37.3%) (the ratio in actual production is 63: 37). This tin-lead alloy is called eutectic solder and is the best performance of tin-lead solder. Kind. It has the following advantages.

 

 

1) Low melting point, which reduces the heating temperature during soldering of the board and prevents component damage.

 

(2) The melting point and the freezing point are the same, so that the solder joints of the circuit board can be quickly solidified, and the semi-solidified state is hardly passed, and the solder joints are not loosely crystallized due to the long time interval of the semi-molten state, and the strength is lowered. This is of particular importance for automatic welding because vibrations are inevitably present in the transmission system of automatic welding equipment.

 

(3) Good fluidity, small surface tension and good wettability, which is beneficial to improve the quality of solder joints.

 

(4) High mechanical strength and good electrical conductivity. Because of the above advantages, eutectic solder has been widely used in the production of electronic products.