The lead alloy: Most of the soldering in the electronic industry is carried out using tin lead alloy. Pure lead metals at 3270C, whereas tin melts at 2320C and the mixture of tin and lead will melt at 1880C when ratio of tin to lead is approximately 60/40. As the ratio moves from 60/40 area, the solder goes through a plastic or pasty stage instead of changing from solid to liquid. The tin lead ratio at which the solder goes directly to liquid stage is called eutectic composition and the resulted alloy is known as eutectic alloy.
Manganin: Manganin is an alloy of copper (86%), Manganese (12%), and nickel (2%).
1. Its electrical resistivity is 48*10-8 ohm-m.
2. Its resistance is stable over a wide range of temperature for a long time.
3. It melts at 1020 degree centigrade.
4. Its specific gravity is 8.2.
5. It can be drawn into wires.
6. Since its resistance temperature coefficient is larger at higher temperature the permissible working temperature of Manganin is low (600C to 700C).
Uses: It is commercially used as a standard resistor and for the instrument shunts.