Reflow of Electrochemically Fabricated Eutectic C4 using a Glycrol-based Water Soluble Flux
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Electrochemical fabrication of eutectic C4s involves through-mask plating, photoresist stripping, and selective etching of seed layers between C4s. During the etching step, C4s are protected by passive layers and hence are covered with reaction products. These reaction products were found to interfere with the eutectic C4 solder reflow process and to constantly leave debris on the reflowed C4 solder surface. These debris were found difficult to remove by both acid etching and intensive water rinse. Since these debris may either hinder the latter joining process or leave voids in solder joints, it is essential to remove these debris and to achieve reflowed C4s with clean, smooth, and round surface.