A wafer level package that incorporates dual compliant layers and a metal cap
layer
on top of I/O pads and a method for forming the package. The wafer level package
includes a plurality of metal cap layers formed on top of a plurality of I/O pads
to function as stress buffering and avoiding sharp corners in metal traces formed
on top of the metal cap layers. A first compliant layer and a second compliant
layer are formed under the metal trace to provide the necessary standoff and to
accommodate differences in coefficients of thermal expansion of the various materials
on an IC die. The wafer level package is particularly suitable for copper devices
or in devices wherein copper lines are used.
