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A step in the manufacturing process of plated-through printed circuit boards. After the generation of the conductive pattern with a solder layer (metallization) used as etching mask, the solder layer is melted by heating and joined to a continuous alloy. The solder layer is melted either by using infrared beams or by immersing the plated-through PCB into a 200-220°C hot oil or glycerin bath. The former method is called infrared fusing while the latter is known as oil fusing. This treatment is used to prevent short circuits between conductor tracks through overhanging solder fillets, to make the solder layer homogeneous and to improve hole filling in contact holes.