Apparatus for aligning die to interconnect metal on flex substrate

Abstract

A method and process sequence for accurately aligning (die to interconnect metal on flex substrate such as polyimide flex is described. A mask for via formation is first patterned in a metal layer on the bottom surface of the flex substrate. Die attach means such as die attach adhesive is then applied to the top side of flex substrate. The bond pads on die are locally, adaptively aligned to the patterned metal via mask on the flex with high accuracy. Vias down to the die bond pads are then created by either plasma etching or excimer laser ablation through the existing aligned metal mask on the flex substrate, and interconnect metal is then deposited, patterned and etched. As a result of this process, the flex metal interconnect artwork does not have to be customized for each die misplacement using “adaptive lithography”. Lower cost commercially available lithography equipment can be used for processing, reducing capital equipment and processing cost. The method is compatible with the projected designs of the next generation die which will have bond pads on the order of 40um in size.