Improved Via Design for Bumped Chips
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
The TAB (tape automated bonding) process calls for the fabrication of metal bonding platforms or bumps on the I/O contact pads of the chip to be TAB bonded. It is desirable that the chip top surface metal, usually aluminum with a small percentage of another metal, be completely sealed by the bump. This will protect the aluminum from exposure to corrosion. The conventional technique that does this calls for overlapping the edges of the bump on the edges of the chip top passivation layer. As a result of the thickness of the passivation, a dimple remains in the top of the bump. This is undesirable, as the dimple may lead to incomplete contact and poor bonding of the TAB lead to the bump.