Issue link: https://iconnect007.uberflip.com/i/721932
102 SMT Magazine • September 2016 es such as die configuration and outline, as well as attachment condition with no signs of pop- corn delamination, could be identified. Howev- er, the integrity of solder ball attachment and solder joints on the board are unidentifiable. Multiple interfaces hinder accurate C-SAM eval- uation of hidden solders under the package. C-SAM Repeat of CGA1752 after Heat Sink Removal The initial C-SAM evaluation of FC-CGA 1752 I/O did not reveal the condition of the flip- chip die and underfill due to the package having a heat-sink interface. We successfully disbonded the heat from the die using a lap shear testing approach. The section of the flip-chip die with no heat sink was subjected to C-SAM evaluation to determine the condition of the flip-chip die and underfill. Figure 15 shows one optical and two C-SAM images of the CGA package. The con - dition of the flip-chip solder balls and joints ap- pears to be acceptable. Only a small anomaly was detected in the underfill at the center of flip- chip die, as indicated by the arrow. To induce ad- ditional defects, this flip-chip CGA with no heat sink was subjected to 20 solder iron touches with a tip temperature of 700°F, each for about 5 sec- onds. No additional defects were detected. Oth- er means need to be developed to induce con- trolled defects and evaluation by C-SAM. Hermetically Sealed CGA1272 with Internal Wire Bonds Figure 16 shows a C-SAM image of a CGA1272 I/O package assembly. Only outer surfaces including the lid brazing section could be detected by C-SAM. DEFECT FEATURES DETECTED BY ACOUSTIC EMISSION Figure 14: Optical and C-SAM images for fine pitch PBGA 432 I/O and PBGA 676 I/O. Figure 15: Optical (top left) and C-SAM images for FC-CGA 1752 I/O assembly after removal of the heat sink, showing the integrity of the flip-chip assembly and minor defect anomaly. Figure 16: C-SAM images for a hermetically sealed CGA 1272 I/O assembly showing heat sink seal integrity. Blue arrows show the lid seal region and red arrows show areas with voids.