Interconnect structures having lead-free solder bumps

摘要

An integrated circuit structure includes a semiconductor substrate, and a polyimide layer over the semiconductor substrate. An under-bump-metallurgy (UBM) has a first portion over the polyimide layer, and a second portion level with the polyimide layer. A first solder bump and a second solder bump are formed over the polyimide layer, with a pitch between the first solder bump and the second solder bump being no more than 150μm. A width of the UBM equals one-half of the pitch plus a value greater than 5μm.