Impact of wafer probe damage on flip chip yields and reliability

(Author's note: A large number of the samples built for this experiment were destroyed in an equipment malfunction. The samples were re-manufactured for the entire experiment. This resulted in long term test results not being available at press time. Additional results will be presented at the IEMT Symposium.) Reliability concerns have historically precluded electrical probing of wafers before the flip chip bumping process. The described experiments show that the bumping process as practiced by Delco Electronics and its commercial bumping venture Flip Chip Technologies has an Under-Bump-Metallurgy (UBM) that is able to tolerate wafer probing before bumping. The quality and bump reliability of a probed wafer is no different than a bump that did not see wafer probe before the bumping process.