In one embodiment, a sub-pad assembly of metal structures is located directly underneath a metal pad. The sub-pad assembly includes an upper level metal line structure abutting the metal pad, a lower level metal line structure located underneath the upper level metal line structure, and a set of metal vias that provide electrical connection between the lower level metal line structure located underneath the upper level metal line structure. In another embodiment, the reliability of a C4 ball is enhanced by employing a metal pad structure having a set of integrated metal vias that are segmented and distributed to facilitate uniform current density distribution within the C4 ball. The areal density of the cross-sectional area in the plurality of metal vias is higher at the center portion of the metal pad than at the peripheral portion of the planar portion of the metal pad.