Issue link: https://iconnect007.uberflip.com/i/721932
100 SMT Magazine • September 2016 central white region. The dark area is postulated to be a total separation of underfill, but needs to be verified. A similar separation condition was also observed for the other LGA 1517 I/O pack- age assembly (SN041), as shown Figure 13. Fine Pitch PBGAs 432 and 676 I/O Two plastic ball grid array package assem- blies, one with 432 balls and 0.4-mm pitch and the other with 676 balls and 1-mm pitch, were subjected to C-SAM evaluation. Figure 14 shows the C-SAM images for these packages as well an optical picture of the test vehicle and the pack- age assemblies. Generally, the C-SAM method is recommended for inspection of individual packages before assembly. Prevalent delamina- tion and "popcorn" cracking in PBGA can be detected. Nevertheless, a few features of packag- DEFECT FEATURES DETECTED BY ACOUSTIC EMISSION Figure 10: Optical and C-SAM (at 25 MHz) layering images for FC-CGA 1517 assembly (SN016) showing flip-chip top and flip chip bump interface. This package had no heat sink. Figure 11: Optical and C-SAM (at 100 MHz) images for FC-CGA 1517 assembly (SN016) showing images for die and substrate interfaces. Figure 12: Optical and C-SAM (at 230 MHz) images for FC-CGA 1517 assembly (SN016) showing images for die and substrate interfaces. Figure 13: Optical and C-SAM (at 230 MHz) images for FC-CGA 1517 assembly (SN041) showing images for die and substrate interfaces.