information:filtering, structural:scholar_edition
Hand soldering

For attachment of electronic components to a PCB, proper selection and use of flux helps prevent oxidation during soldering; it is essential for good wetting and heat transfer. The soldering iron tip must be clean and pre-tinned with solder to ensure rapid heat transfer.

Electronic joints are usually made between surfaces that have been tinned and rarely require mechanical cleaning, though tarnished component leads and copper traces with a dark layer of oxide passivation (due to aging), as on a new prototyping board that has been on the shelf for about a year or more, may need to be mechanically cleaned.

To simplify soldering, beginners are usually advised to apply the soldering iron and the solder separately to the joint, rather than the solder being applied directly to the iron. When sufficient solder is applied, the solder wire is removed. When the surfaces are adequately heated, the solder will flow around the workpieces. The iron is then removed from the joint.

If all metal surfaces have not been properly cleaned ("fluxed") or brought entirely above the melting temperature of the solder used, the result will be an unreliable ("cold solder") joint, even though its appearance may suggest otherwise.

Excess solder, unconsumed flux and residue is sometimes wiped from the soldering iron tip between joints. The tip of the bit (commonly iron plated to reduce erosion) is kept wetted with solder ("tinned") when hot to assist soldering, and to minimize oxidation and corrosion of the tip itself.

After inserting a through-hole mounted component, the excess lead is cut off, leaving a length of about the radius of the pad.

Hand-soldering techniques require a great deal of skill for the fine-pitch soldering of surface-mount chip packages. In particular ball grid array (BGA) devices are notoriously difficult, if not impossible, to rework by hand.