Abstract: A lead-free solder bump fabrication process for producing a plurality of lead-free solder bumps over a wafer is provided. The lead-free solder bump fabrication process includes forming a lead-free pre-formed solder bump over each bonding pad on the wafer and then forming a patterned solder mask layer over the active surface of the wafer. The openings in the solder mask layer expose the respective lead-free pre-formed solder bumps on the wafer. Thereafter, lead-free solder material is deposited into the opening. The material composition of the lead-free solder material differs from the material composition of the lead-free pre-formed solder bump. A reflow process is conducted so that the lead-free pre-formed solder bump fuses with the lead-free solder material to form a lead-free solder bump. Finally, the solder mask layer is removed.

Abstract: A method of modifying the tin to lead ratio of a tin-lead bump forms a patterned solder mask over a substrate that comprises a first tin-lead bump formed thereon, the patterned solder mask having an opening that exposes the tin-lead bump. A solder material including tin and lead is filled in the opening of the solder mask over the first tin-lead bump. The solder material has a tin to lead ratio that differs from that of the first tin-lead bump. The solder material is reflowed to fuse with the first tin-lead bump, which forms a second tin-lead bump. The tin to lead ratio of the second tin-lead bump is thereby different from that of the first tin-lead bump.

Abstract: A solder ball fabrication process for forming solder balls over a wafer having an active layer is provided. A plurality of patterned solder mask layers is sequentially formed over the active surface of the wafer. Each patterned solder mask layer has at least an opening that exposes a solder ball pad on the wafer. The opening of the patterned solder mask layers further away from the solder ball pad is larger in diameter than the opening of the patterned solder mask close to the solder ball pad. Solder material is deposited into the openings and a reflow process is conducted to melt the solder material together so that a solder ball is formed over the solder ball pad.

Abstract: A method for etching a nickel-vanadium alloy is described. The etching of the nickel-vanadium alloy is conducted using an etchant that comprises sulfuric acid. Further, the etching rate of the nickel-vanadium alloy is controlled based on the electrolytic reaction between the etchant and the nickel-vanadium alloy thin film.

Abstract: The present invention provides a bump fabrication process. A wafer is provided with a patterned photoresist layer formed on the wafer. The patterned photoresist layer has a plurality of openings, corresponding to bonding pads. A conductive layer is formed on the photoresist layer and the exposed bonding pads. Afterwards, a sticker film is provided to lift off the conductive layer on the photoresist layer, while the conductive layer within the openings is not removed. A solder paste is filled into the openings. A reflow step is performed to turn the filled solder paste into globular bumps. At last, the photoresist layer is removed.