It is necessary to make balls before bga welding. It refers to a welding method in which the solder and the solder are heated to the melting temperature of the solder at the same time, and the gap of the solid workpiece is filled with the liquid solder to make the metal join.
During brazing, the oxide film and oil on the contact surface of the base metal must be removed first, so that the capillary can play a role in the melting of the filler metal and increase the wettability and capillary fluidity of the filler metal.