Removing Residual Polyamic Acid Salt Films From Chip Joining Solder Balls
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Polyamic acid used in the final step of an integrated circuit (IC) fabrication process forms an undesirable lead polyamate salt (a barrier film) on the solder ball chip interconnect. A technique for the removal of this film from the surface of the solder ball is described. Polyamic acid is applied over an entire chip as the last step of an IC fabrication process. Lead polyamate salts are formed on the solder balls during this process step. When cured, these salts form stable encapsulating imide films which prevent wetting by the solder and inhibit chip joining to the substrate. The problem films form during the initial contact between the polyamic acid and the lead in the solder ball.