Patent ID: 7718523

Claim:
A solder ball forming method comprising: preparing a semiconductor die comprising a plurality of electrically conductive pads formed on a surface thereof; preparing a solder attach film comprising a first cover film, a flux layer formed on the first cover film, a solder layer formed on the flux layer, and a second cover film formed on the solder layer, and barrier ribs formed between the first cover film and the second cover film so as to penetrate the flux layer and the solder layer; removing the first cover film from the solder attach film; adhering the solder attach film such that the flux layer is adhered to the surface of the semiconductor die and the barrier ribs are aligned to areas not corresponding to the electrically conductive pads; removing the second cover film so the flux layer and the solder layer remain in the areas corresponding to the electrically conductive pads; and putting the semiconductor die, the flux layer, and the solder layer into a furnace to volatilize and remove the flux layer and to fuse and fix the solder layer to the electrically conductive pads, thereby forming solder balls.