In mounting of a semiconductor device, it is frequently used to connecting a discrete semiconductor device to a circuit substrate using a solder bump. As the solder bump, in recent years, along with propulsion of Pb-free, solder such as Sn—Ag based-alloy and the like are used instead of Sn—Pb based-alloy solder.
When electroplating with Sn—Ag based-alloy, if Sn is used for an anode, Ag is substitution-deposited on an anode surface since Ag is nobler than Sn. In order to prevent this, it is frequent to use an insoluble anode such as Pt and the like for electroplating. However, electrolysis may be deteriorated since hydrogen is generated on the anode surface. Accordingly, it is contrived not to substitution-deposit Ag in the soluble anode.
Patent Document 1 discloses that when an object to be plated is soaked in a lead-free tin-alloy electroplating bath in an electroplating tank so that electroplating is performed in a state in which the object to be plated is a cathode, electroplating is performed in the plating tank in a state in which the anode is isolated by an anode bag or a box formed by a cation-exchange membrane. According to this method, Sn ions in plating solution in the anode box are moved to the plating tank through the exchange membrane, so that the Sn ions are stably supplied. Therefore, even if a soluble anode such as Sn and the like is used as an anode, by movement of cations, deposition of metals with respect to an anode can be prevented.
USPTO Backgrounds
USPTO Backgrounds