The Application of THz-TDR in Failure Analysis of ICs in FCBGA Packages

IC failure analysis includes not only wafer failure, but also package failure. Especially for complex packaging devices, conventional non-destructive methods such as FCBGA, X-RAY or CT can not accurately locate the packaging defects in integrated circuits. In this paper, the principle of non-destructive terahertz time-domain reflectometry (THz-TDR) is introduced, and its application in IC failure analysis is illustrated. The TDR uses a laser signal generated by a signal generator to send a high-frequency pulse with a fast rise time to the IC. When an impedance discontinuity is encountered, part of the pulse energy is reflected back, and by monitoring the time at which these reflected signals arrive at the oscilloscope and comparing them to the size of the original pulse, it is possible to determine if there is an impedance change in the line. The open circuit and short circuit faults in the integrated circuit can be quickly located using the TDR machine.