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106 SMT Magazine • September 2016 no heat sink on the flip-chip die. This allowed C-SAM characterization of the flip-chip bumps and underfill materials. • Microscopic cross-sectional evaluation of FC-CGA 1517 did not support the edge-delami- nation revealed by the C-SAM images. • C-SAM of a hermetically sealed LGA 1272 package revealed only the lid bonding defects. Internal features could not be detected. For plas- tic LGA1156, the C-SAM revealed only the die, but not the solder joint condition. • C-SAM of a large number of other fine pitch ball grid array assemblies revealed inter- nal die integrity and configuration, but it did not show solder ball or joint attachment integ- rity. • No defect was detected by C-SAM when CGA 1752 I/O and fine pitch BGA packages with 20 repeated solder iron touches, each for about 5 seconds using a tip temperature of 700°F. Non-destructive evaluation of microelec- tronic packaging and assemblies is of critical importance in assuring reliability. Understand- ing key features of various NDE inspection sys- tems in detecting defects in the early stages of assembly are critical to developing approach- es that will minimize future failures. Addition- al specific, tailored, NDE inspection approach- es could enable low-risk insertion of these ad- vanced electronic packages. Even though C-SAM showed significantly lower versatility in defect detection compared to X-ray for packages and assemblies of FC-CGA and FCBGA, the C-SAM techniques are widely used for detection of flip-chip die attachment by package manufacturers during the early stag- es of the flip-chip die assembly. However, add- ed additional interfaces (e.g., heat sink on die) limits the use of acoustic emission approach at package and assembly levels. The recently de- veloped GHZ SAM version is shown to have po- tential for TSV defect detection even for com- plete wafer inspection. C-SAM inspection is a non-destructive tech- nique with a wider use for revealing hidden gap defects, including delamination and voids. It is recommended that the C-SAM characterization be used as a complement to other inspection techniques, including X-ray and traditional vi- sual inspection by optical microscopy. It is ap- parent that a combination of various inspection techniques may be required in order to assure quality at part, package, and system levels. This is especially true for newly introduced minia- turized advanced electronic packages with hid- den flip-chip solder bumps at the die level and solder balls at the package level with associated underfill and solder joints. Acknowledgments This research was carried out at the Jet Pro- pulsion Laboratory, California Institute of Tech- nology, and was sponsored by the Nation- al Aeronautics and Space Administration Elec- tronic Parts and Packaging (NEPP) Program. Reference herein to any specific commer- cial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement by the United States Government or the Jet Propulsion Laboratory, California Institute of Technology. Copyright 2015. California Institute of Technol- ogy. Government sponsorship acknowledged. The author would like to acknowledge many people from industry, especially Ken Tylor, and the Jet Propulsion Laboratory (JPL), especially Steve Bolin, who were critical to the progress of this activity. The author extends his apprecia- tion to program managers of the National Aero- nautics and Space Administration Electronics Parts and Packaging (NEPP) Program, including Michael Sampson and Ken LaBel for their con- tinuous support and encouragement. SMT References 1. Ghaffarian, R., "Damage and Failures of CGA/BGA Assemblies under TC and Dynam- ic Loading," ASME, IMEC, San Diego, CA, Nov. 2013. 2. Ghaffarian, R. "Thermal Cycle and Vibra- tion/Drop Reliability of Area Array Package As- semblies," Structural Dynamics of Electronics and Photonic Systems, eds. E. Suhir, E. Connal- ly, and D. Steinberg, Chapter 22, John Wiley, New York, NY, 2011. 3. Ghaffarian, R., "Thermal Cycle Reliabili- ty and Failure Mechanisms of CCGA and PBGA Assemblies with and without Corner Staking," IEEE Transactions on Components and Packag- DEFECT FEATURES DETECTED BY ACOUSTIC EMISSION

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