Applications of Ag-alloy stud bump for IC and LED packages

Recently, 3-D IC and 2.5-D IC packages become more popular and Cu pillars are often employed as their conductive bumps. However, since the Cu pillars are hard and rigid, it is difficult to plastically deform for the solid contact between the Cu pillars and bonding pads during the assembly process utilizing hot pressing. In this case, a coplanar problem may occur, which leads to voids or even failure at the bonding interfaces. The Ag-alloy wires previously developed by Wire Technology Co., LTD., have been further manufactured as stud bumps for flip-chip interconnections. This innovative Ag alloy stud bump is softer, so it is able to plastically deform during hot pressing to be in solid contact with the on-substrate bonding pad, preventing the coplanar problem of Cu pillars in 3D- or 2.5D-IC packages. The Ag-alloy stud bumps also exhibit many other advantages for applications in advanced IC and high power flip chip packages as comparing with the conventional Au- or Cu- stud bumps.