Presently, tin and solder coatings are the main metal finishes employed in the manufacturing of circuit boards and electronic components. In order to protect the substrate from oxidation during the storage and manufacturing process, the solder or tin layer has to have a certain thickness and quality. There are two common ways to apply solder to the surface of the board or component—electroplating and hot solder leveling/dipping. The plated coatings are usually more porous and have a higher level of surface oxides than do the coatings applied in contact with molten solder. Electroplating is also apt to have other surface contaminants, for example, codeposited organics. The presence of surface contaminants, excessive oxides, and porosity may adversely affect the solderability. There are some disadvantages in hot solder application as well, particularly the varying of the solder layer thickness, which can affect the surface planarity.
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