Soldering is an integral and important of any electronics PCB manufacturing, assembly and rework / repair./ Soldering is defined as "the joining of metals by a fusion of alloys which have relatively low melting points e.g. alloy of tin and lead (sn/pb)". This allows is called solder, which could be solder wire, solder bar, solder paste, solder balls or solder preforms. Kester is the leading manufacturers and suppliers of solder and solder materials. In electronics industry, soldering is done to mainly to solder electronic components on to the circuit board to get a circuit board assembly.

1. Wave Soldering: Wave soldering is done for mass production using wave soldering machine, solder bar, flux, reflow checkers, dip tester, spray fluxers, flux controller.

2. Reflow Soldering: Reflow Soldering is done for mass produuction and is used for soldering of SMD components. Equipments and soldering material needed for reflow soldering are - Reflow Oven, Reflow checker, stencil printer, solder paste, flux.

4. Hand Soldering: Hand soldering is done in small scale production and repair and rework of PCB. Equipments and raw materials needed in hand soldering are - Soldering iron, soldering station, solder wire, solder paste, flux, desoldering iron or desoldering station, tweezers, solder pot, hot air system, wrist straps, smoke absorbers, static eliminators, heating gun, pick-up tools, lead formers, cutting tools, microscopes and magnifying lamps, solder balls, flux pen, desoldering braid or wick, desoldering pump or sppon, overcoat pen, esd material.

Equipment and material needed to solder:

Hand Soldering requires two main things: a soldering iron / soldering station and solder (wire / paste / solder balls). Nor normal hobby and repair soldering works, a normal 15W or 30W soldering iron is good. Foir mass rework / repairing jobs, temperature controlled soldering station is good because it offer faster thermal recovery.

If you are doing lead-free soldering, you may need a soldering iron or soldering station of higher wattage of about 50W to 60W or higher because melting point of lead-free solder is more than normal Sn/Pb solder. Weller and Hakko are leading suppliers of soldering iron, soldering station and other soldering equipment.

Next you need solder wire. If you are soldering a surface mount component (Chip), you will need solder paste, although many SMD electronic components can also be soldered using fine solder wire. For BGA soldering you will need BGA solder balls. You also need solder flux.

Remember that when soldering, the rosin in the solder releases fumes. These fumes are harmful to your eyes and lungs. Therefore, always work in a well ventilated area. Use smoke absorbers.

A clean PCB surface is very important if you want a strong, low resistance solder joint. All surfaces to be soldered should be cleaned with steel wool or any other PCB cleaning solvent. Laquer thinner works well. Some people also use sand paper, but I don’t recommend that and it can damage the traces on the circuit board. I recommend using steel wool. Clean both board surface and component leads.

Once you circuit board and electronic components are clean, you are ready to solder. Bend the component leads as required and insert through the proper holes on the board. To hold the part in place while you are soldering, you may want to bend the leads on the bottom of the board at a 45 degree angle. Once you are sure that the component is properly placed, you can move on to the next step.

Now apply flux on the pads and components leads. Flux will help to remove any oxide that may have accumulated on to the pads and components leads. Take small quantity of solder to the tip of the soldering iron and lay the iron tip so that it rests against both the component lead and the board. Normally, it takes one to two seconds to heat the component up enough to solder, but larger components and larger soldering pads on the board may need more time.

Once the component lead and solder pad has heated up, you are ready to apply solder. Hold and touch the tip of the strand of solder to the component lead and solder pad. Note that tip of soldering iron will be away at this point of time. Now tough the tips of the soldering iron to the solder wire and the pad. Molten solder should flow freely around the lead and pad to form a perfect solder joint. Allow the solder to cool. This should take 4-5 seconds. If you do move the joint, within this time, you will get a "cold joint".

After you have soldered all the solder joints, you may clean the circuit board assembly with steel wool or circuit board cleaning solvent to remove all the left over rosin from flux or cored solder wire. You may also apply conformal coating which acts like a laminate for the circuit board and prevents oxidation.