Laser Deposition of Gold Bumps for TAB Packaging of Chips
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
The low-end packaging of chips can be accomplished by Tape Automated Bonding (TAB), in which chip-to-package interconnections are formed simultaneously and reliably. This technique currently involves the placement of gold bumps (1 mil in thickness) on the I/O pads of the chip before bonding. The gold bumps are formed by electroplating which requires: a) electrically connecting all the I/O pads on the chip by deposition of a conductive gold layer; b) photoresist application and processing; c) a wet process for the plating of the gold bump. Alternatively, the bumps can be produced on the copper fingers (or beams) on the TAB tape by subtractive etching of a thick copper finger to form the bump. In this case, copper is the bump.