Patent ID: 6939790

Claim:
A method of forming a plurality of bumps on a wafer having an active surface, wherein the wafer further includes a plurality of bonding pads formed on the active surface and a passivation layer formed on the active surface that exposes the bonding pads, the method comprising the steps of: forming an under bump metallurgy layer over the active surface of the wafer, wherein the under bump metallurgy layer covers both the bonding pads and the passivation layer; patterning the under bump metallurgy layer so that a residual portion of the under bump metallurgy layer remains over each of the bonding pads; forming a polymer layer over the active surface of the wafer, wherein the polymer layer has a plurality of openings that expose the residual portion of the under bump metallurgy layer; disposing a plurality of solder balls into each of the openings, wherein each of the solder balls has a flux material formed on a surface of each of the solder balls; performing a reflow process so that the solder balls are bonded to the residual portion of the under bump metallurgy layer; and removing the polymer layer.