A reliable technique for characterizing the hygroscopic swelling of materials has been developed and used to characterize a number of packaging materials. Using these data, hygroscopic stress modeling were performed. The hygroscopic stress induced through moisture conditioning was found to be significant compared to the thermal stress during solder reflow. Hygroscopic stress in over-molded wire bond PBGA and molded Flip Chip PBGA was found to be 1.3 times to 1.5 times that of thermal stress. Hygroscopic swelling of the underfill in FCPBGA was found to be the main failure driver during autoclave test. Autoclave performance of FCPBGA package assembled with different underfills and chips were analyzed. Excellent correlation was found between autoclave performance and the hygroscopic swelling characteristics of the underfills.
The Mechanics and Impact of Hygroscopic Swelling of Polymeric Materials in Electronic Packaging
Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received by the EPPD October 5, 2000. Associate Editor: S. M. Heinrich.
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Wong, E. H., Rajoo , R., Koh , S. W., and Lim, T. B. (May 2, 2002). "The Mechanics and Impact of Hygroscopic Swelling of Polymeric Materials in Electronic Packaging ." ASME. J. Electron. Packag. June 2002; 124(2): 122–126. https://doi.org/10.1115/1.1461367
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