<P> 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 involved . </P> <P> Excess solder and 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 . </P> <P> 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 . Those regulations have also reduced the use of lead based solders, and caused the melting temperatures of solders in use to increase by up to a hundred degrees F . </P> <P> Hot - bar reflow is a selective soldering process where two pre-fluxed, solder coated parts are heated with heating element (called a thermode) to a sufficient temperature to melt the solder . </P>

Which are the materials generally employed as solders in soldering operations in electronics