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110 SMT Magazine • August 2016 Conclusions We have demonstrated that SAT images from a multilayer stack of ceramics-organics-ceramics structure with embedded devices can be sepa- rated to individual layers to characterize if flaws are included in the acoustically deep layers. The SAT findings are confirmed by cross sectioning a selected sample. To successfully image such samples, the transducer frequencies should be able to vary at will in certain range and the acoustic beam spot small while focal length of the probe long enough for a given sample. Acknowledgements The authors would like to thank the mem- bers of Flex China and Failure Analysis Lab in the USA, as well as the experts of SAT demo lab at Hitachi Power Solutions, Japan, who all re- lentlessly supported this project to conclude a success. SMT References 1. K. Kitami, M. Takada, O. Kikuchi, and S. Ono, "Development of High Resolution Scanning Acoustic Tomograph for Advanced LSI Packages," Proceedings of 20th IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits, 2013, pp 530-533. 2. K. Kitami, M. Murai, N. Sugaya, O. Kikuchi, and S. Ono, "New Technique for Acquiring Dead Pixel Free and Fine Inspection Image of Advanced LSI Package with Rough Surface using Scanning Acoustic Tomograph," Proceedings of 21st IEEE In - ternational Symposium on the Physical and Failure Analysis of Integrated Circuits, 2014, pp 530-533. 3. Z. Feng, D. Geiger, W. Liu, A. Mohammed, M. Kurwa, and G. Tint, "Characterization of Solder Defects in Package-on-Packages with AXI Systems for Inspection Quality Improvements," Proceed- ings of IPC APEX, San Diego, CA, 2015. 4. D. Geiger, Z. Feng, J. Nguyen, W. Liu, A. Mo- hammed, M. Kurwa, G. Xu, L. Su, and G. Tint, "Op- timization of X-ray Inspection for Solder Charged Connectors," Proceedings of SMTAI, Chicago, IL, 2015. 5. G. Tint, "Transducer Properties for High Def- inition SAT Imaging of Semiconductor Packages," Chip Scale Review Magazine, June 2007. Note: This article was presented at the technical proceedings of the IPC APEX EXPO 2016. *Co-Authors: J. Zheng, J. Lian, Ph.D., Z. Feng, Ph.D., L. Su, D. Willie, and D. Geiger, Flextronics International Ltd; M. Takada and N. Sugaya, Hitachi Power Solutions Co. Ltd; and G. Tint, Ph.D., HDI Solutions Inc. NONDESTRUCTIVE INSPECTION OF UNDERFILL LAYERS Figure 8: Cross section image of center region with 150x optical microscope. Figure 9: Cross section image of center region with 500x optical microscope, the lower level de- laminations are somewhat difficult to distinguish by optical cross sections.