Design Circuit Board Pcb
Electronic components (PCBs)
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 direct 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 joint. The iron is then removed from the joint.
Since non-eutectic solder alloys have a small plastic range, the joint must not be moved until the solder has cooled down through both the liquidus and solidus temperatures. When visually inspected, a good solder joint will appear smooth and shiny, with the outline of the soldered wire clearly visible. A matte gray surface is a good indicator of a joint that was moved during soldering.
Other solder defects can be detected visually as well. Too little solder will result in a dry and unreliable joint; too much solder (the familiar 'solder blob' to beginners) is not necessarily unsound, but tends to mean poor wetting. With some fluxes, flux residue remaining on the joint may need to be removed, using water, alcohol or other solvents compatible with the parts in question.
Excess solder and unconsumed flux and residue is sometimes wiped from the soldering iron tip between joints. The tip of the iron is kept wetted with solder ("tinned") when hot to assist soldering, and when hot and cold to minimize oxidation and corrosion of the tip itself.
Environmental legislation in many countries, and the whole of the European Community area (see RoHS), has led to a change in formulation of both solders and fluxes. Water-soluble non-rosin-based fluxes have been increasingly used since the 1980s so that soldered boards can be cleaned with water or water-based cleaners. This eliminates hazardous solvents from the production environment, and from factory effluents.