Soldering is the process of joining two or more similar or dissimilar metals by melting another metal having low melting point. The materials and tools that are required in the process of soldering are solder, flux, knife, blade, and soldering iron and nose plier.

              Soldering fluxes

In order to make the surfaces accept the solder readily, the component terminals should be free from oxides and other obstructing films. Soldering fluxes are used to clean the oxide from the surface of the metal .The leads should be cleaned chemically or by scrapping using a blade or a knife .Small amount of lead should be coated on the cleaned portion of the leads and the bit of the soldering iron. This process is called tinning. Zinc chloride; ammonium chloride and rosin are the most commonly used fluxes.

              Solder

                 Solder is used for joining tow or more metals below their melting point. The popularly used solder are the alloys of tin (60%) and lead (40%) that melts at 370 degrees Fahrenheit and solidifies when it cools .Most of the solder wires are flux cored type. When such solder wires are used, extra soldering flux is not required.

Soldering tools

Soldering iron is the most important tool used for soldering. It is used to melt the solder and apply at the joints in the circuit. It operates in 230V mains supply. The power ratings of the soldering iron are 10W, 25W, 35W, 65W and 125W etc.The iron bar at the tip of it gets heated up within a few minutes .Soldering gun is a gun shaped soldering tool used especially when more heat is required .Its trigger is a switch that controls the ac voltage to the circuit.

Desoldering

It is the removal of solder from the previously soldered joints. Desolder pump is a commonly used device for this purpose. When the solder melts by the action of the soldering iron, a trigger on the desolder pump should be activated to create a vacuum. This vacuum pulls the solder into the tube.

Soldering rules

There are various rules for the soldering process. They include the following-

• Select the proper soldering iron for the work.
• Tin the bit before soldering.
• Keep the tinned bits always clean from oxide formed while soldering.
• Do not over heat the PCB and devices.
• Do not use excess solder or flux.
• Clean the surfaces of the leads to be joined using a blade.

 Procedure for soldering

The procedure that is involved in soldering process is as follows-

• Make a lay-out of the components in the circuit. Plug in the chord of soldering iron into the mains supply to get it heated up.
• Clean the component leads, using a blade or a knife and bend them according to the needs. Apply a little flux on the leads. Take a little solder on soldering iron and apply the molten solder on the leads. Care must be taken to avoid the components heated up.
• Mount the components on the PCB, apply flux on the joints and solder the joints. Soldering must be done in minimum time to avoid dry-soldering and heating up of the components.
• Wash the residues using water and brush.
• Desolder the soldered circuit, if necessary, using soldering iron and the desolder pump.