Nondestructive methodology for standoff height measurement of flip chip onflex (FCOF) by SAM

Flip chip technology is the emerging interconnect technology for the next g eneration of high performance electronics. One of the important criteria fo r reliability is the width of the gap between the die and the substrate, i. e., the standoff height, A nondestructive technique using scanning acoustic microscopy (SAM) for the standoff height measurement of flip chip assembli es is demonstrated. The method, by means of the implementation of a pulse s eparation technique, time difference of the representative signals of the d ie bottom and water interface and water and substrate surface interface fro m the A-scan image can be found. Then, the corresponding standoff height ca n be calculated. When compared to the traditional destructive measurement m ethod (SEM analysis on sectioned sample), this nondestructive technique yie lds reliable results.