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Experimental and numerical reliability investigations of FCOB assemblies with process-induced defects

: Schubert, A.; Dudek, R.; Kloeser, J.; Michel, B.; Reichl, H.; Hauck, T.; Kaskoun, K.

Electronic Components, Assemblies, and Materials Association; IEEE Components, Packaging, and Manufacturing Technology Society:
ECTC 2000. Proceedings of the 50th Electronic Components & Technology Conference : May 21 - 24, 2000, Las Vegas, Nevada, USA
Piscataway, NJ, USA: IEEE Press, 2000
ISBN: 0-7803-5908-9
ISBN: 0-7803-5909-7
ISBN: 0-7803-5910-0
ISBN: 0-7803-5911-9
Electronic Components and Technology Conference (ECTC) <50, 2000, Las Vegas/Nev.>
Fraunhofer IZM ()

To develop comprehensive design guidelines, models and experiments cannot overlook process-induced imperfections in the flip chip on board (FCOB) assemblies. The following items were noted as being significant factors which were used for modeling and by thermal cycling tests: (a) varying stand-off-heights and alternative bump sizes, (b) underfill-particle settling, (c) underfill-void effects, (d) underfill-to-bump coverage, (e) asymmetrical fillets vs. symmetrical fillets. A detailed numerical and experimental reliability study of perfect and imperfect flip chip assemblies has been completed. Experimental studies of the failure modes and of the mean cycles to failure are in good agreement with the failure modes and life time, as predicted by FEM for the different technological variants. A hierarchy of influences was worked out in three levels (important, medium, negligible). Most important imperfections resulting in a strong reliability decrease are particle settling, a symmetrical fillets and small and big voids.