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88 SMT Magazine • September 2016 by Reza Ghaffarian, Ph.D. JET PROPULSION LABORATORY, CALIFORNIA INSTITUTE OF TECHNOLOGY Abstract C-mode scanning acoustic microscopy (C- SAM) is a non-destructive inspection tech- nique showing the internal features of a speci- men by ultrasound. The C-SAM is the preferred method for finding "air gaps" such as delami- nation, cracks, voids, and porosity. This paper presents evaluations performed on various ad- vanced packages/assemblies especially flip-chip die version of ball grid array/column grid array (BGA/CGA) using C-SAM equipment. For com- parison, representative X-ray images of the as- semblies were also gathered to show key defect detection features of the two non-destructive techniques. Below are some of the highlights of the study: • Compare the images of 2D X-ray and C- SAM for a plastic LGA assembly showing fea- tures that could be detected by either NDE tech- nique. For this specific case, X-ray was a clear winner. • Evaluate flip-chip CGA and FCBGA assem- blies with and without heat sink by C-SAM. Evaluation was to evaluation defect condition of underfill and bump quality. Cross-sectional microscopy performed to compare defect fea- tures detected by C-SAM. • Analyze a number of fine pitch PBGA as- semblies by C-SAM to detect the internal fea- tures of the package assemblies and solder joint failure at either package or board levels. Twenty times touch up by solder iron hav- ing 700°F, each with 5–7seconds and induced defects were analyzed by C-SAM images. Acoustic Emission Technology Electronic Packaging Trend Previous generations of microelectronic packaging technology aimed mostly at meeting the needs of high-reliability applications, such as the ceramic leaded quad flat package (CQFP). Nondestructive wire bond pull at the package level and subsequent visual inspection for sol- der joint integrity at the board level were ade- quate for ensuring the quality of CQFPs. Con- sumer electronics are now driving miniaturiza- Defect Features Detected by Acoustic Emission for Flip-Chip CGA/FCBGA/PBGA/FPBGA Packages and Assemblies FEATURE

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