Hand soldering
Soldering with melted solder
a.Dip in soldering
b.Wave soldering
c.Drag soldering
Soldering with solder paste
a.Reflow soldering
b.Laser soldering[...]

First of all, soldered to be area is heated with the soldering iron.
As solder wire contacts with the area, the solid flux in the wire melts around at 100°C and spreads on the area which makes it clean.
As solder reaches the melting temperature it melts and spreads on fully.
During the spread, an intermetallic layer is formed and soldering is finalizes.[...]

To choose the correct soldering iron, tip and temperature,
To choose the right solder wire diameter,
To choose the appropriate solder alloy and flux,
Soldering process should be applied correctly.[...]

Hand-soldering is a soldering method where soldering iron is used as the heater as well as flux containing solder wire.[...]