| abstract |
Solder bumps are included on the UBM structure and a solder bump structure is provided for operation at temperatures above 2500 ° C. According to the first embodiment, the UBM structure comprises layers of Ni-P, Pd-P, and gold, wherein the Ni-P and Pd-P layers act as barrier layers and / or solderable / bondable layers. The gold layer acts as a protective layer. According to the second embodiment, the UBM structure comprises layers of Ni-P and gold, the Ni-P layer serving as a solderable / bondable layer as well as a diffusion barrier layer, and the gold layer serving as a protective layer. According to a third embodiment, the UBM structure comprises (i) a thin layer of metal, such as titanium or aluminum or a Ti / W alloy, and (ii) a NiV, W, Ti, Pt, TiW alloy or Ti / W / N alloy. The same metal, and (iii) a metal alloy such as Pd-P, Ni-P, NiV, or TiW, followed by a layer of gold. Alternatively, gold, silver, or palladium bumps can be used in place of solder bumps in the UBM structure. |