under-bump metallization (UBM)

A patterned, thin-film stack of material that provides 1) an electrical connection from the silicon die to a solder bump; 2) a barrier function to limit unwanted diffusion from the bump to the silicon die; and 3) a mechanical interconnection of the solder bump to the die through adhesion to the die passivation and attachment to a solder bump pad.

JEP154, 1/08