A cylindrical bonding structure and its method of manufacture. The
cylindrical bonding structure is formed over the bonding pad of a silicon
chip and the chip is flipped over to connect with a substrate board in
the process of forming a flip-chip package. The cylindrical bonding
structure mainly includes a conductive pillar and a solder cap. The
conductive pillar is formed over the bonding pad of the silicon chip and
the solder cap is attached to the upper end of the conductive pillar. The
solder cap has a melting point lower than the conductive pillar. The
solder cap can be configured into a cylindrical, spherical or
hemispherical shape. To fabricate the cylindrical bonding structure, a
patterned mask layer having a plurality of openings that correspond in
position to the bonding pads on the wafer is formed over a silicon wafer.
Conductive material is deposited into the openings to form conductive
pillars and finally a solder cap is attached to the end of each
conductive pillar.