Scanning acoustic microscopy (SAM) is a non-destructive tool for analysis of packaged devices. New materials, package configurations, and technologies have required adaptation of standard practices in SAM. The detection of cracked die, voids, or delamination in the underfill or package are standard issues for SAM. SAM can routinely detect large cracks through the central 80% of the die; however, the occurrence of smaller cracks at the edge of the flip chip die is problematic. This article proposes a model in which alteration in the standard SAM parameters, the gain and Time-of-Flight, enable detection of die edge cracks in assembled Flip Chip devices. IR imaging after thinning and polishing of the die confirms the die edge cracks. The SAM analysis can replace the IR imaging for detection of small die edge cracks taking minutes to complete instead of the hours involved in the sample preparation for IR imaging.

The acquisition of reliable Acoustic Micro Images (AMI) are an essential non-destructive step in the Failure Analysis (FA) of electronic packages. Advanced packaging and new IC materials present challenges to the collection of reliable AMI signals. The AMI is complicated due to new technologies that utilize an increasing number of interfaces in ICs and packages. We present two case studies in which it is necessary to decipher the acoustic echoes from the signals generated by the interface of interest in order to acquire trustworthy information about the IC package.

Acoustic Micro Imaging (AMI) is an established nondestructive technique for evaluation of electronic packages. Non-destructive evaluation of electronic packages is often a critical first step in the Failure Analysis (FA) process of semiconductor devices [1]. The molding compound to die surface interface of the Plastic Ball Grid Array (PBGA) and Plastic Quad Flat Pack (PQFP) packages is an important interface to acquire for the FA process. Occasionally, with these packages, the standard acoustic microscopy technique fails to identify defects at the molding compound to die surface interface. The hard to identify defects are found at the edge of the die next to the bond pads or under the bonds wires. This paper will present a technique, Backside Acoustic Micro Imaging (BAMI) analysis, which can better resolve the molding compound to die surface interface at the die edge by sending the acoustic signal through the backside of the PBGA and PQFP packages.