A ball grid array for a flip-chip assembly is disclosed. The ball grid array
includes
a plurality of bumps bonded between an active surface of a semiconductor die and
a top surface of a printed circuit board or any type of substrate carrier. The
plurality of balls include at least one bump having a core material and an outer
layer. The rigidity of the core material is greater than that of the material of
the outer layer. Additionally, the melting temperature of the core material is
higher than the material of the outer layer. By this arrangement, the core material
with an outer layer provides bumps that are substantially uniform in height. In
addition, the balls only procure marks or deformation to the core material during
burn-in testing and reflow. Therefore, when bonding the semiconductor device to
the substrate, the ball grid array provides sufficient electrical and mechanical
connection despite any non-planarity in the active surface of the semiconductor
device and the top surface of the substrate, and any differing height in the plurality
of balls due to testing the semiconductor device.
