Solder bumps have been used to interconnect the chip and substrate, and the size of the solder bump decreases below $100{\mu}m$ to accommodate higher packaging density. In order to fabricate solder bumps, a mold to chip transfer process is suggested i...
Solder bumps have been used to interconnect the chip and substrate, and the size of the solder bump decreases below $100{\mu}m$ to accommodate higher packaging density. In order to fabricate solder bumps, a mold to chip transfer process is suggested in this work. Since the thin stainless steel mold is not wet by the solder, the molten solder is forced to fill the mold cavities with ultrasonic vibration. The solders within the mold cavities are transferred to the Cu pads on the polyimide film through reflow soldering.