The effects of underfill selection on flip chip reliability were always a complex issue. Mechanical optimization of the underfill performance, achieved by the addition of appropriate fillers, is invariably a tradeoff between the adhesion and the coefficient of thermal expansion (CTE) and, thus, also between in-plane and out-of-plane stresses. Another critical concern is the degradation of the underfill in processing and/or long term exposure to operating temperatures and ambient humidity. This is strongly affected by the chemical compatibility with combinations of solder mask, chip passivation, and flux residues. The latter is believed to be responsible for our observation of interactions with the solder alloy, too. As for the effects of glass transition temperatures and CTE, we find materials that were close to optimum for eutectic SnPb to be very far from the best options for lead free joints. We report on two sets of systematic experiments. The first addressed the performance of combinations of underfills, no-clean fluxes, and solder alloys in a JEDEC level 3 moisture sensitivity test. The second one involved thermal shock testing of flip chip assemblies underfilled with one of five different materials after soldering with SnCu, SAC305, and SnPb.
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e-mail: pborgese@binghamgton.edu
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September 2010
Research Papers
Interactions Between Flip Chip Underfill and Solder Alloy
P. Borgesen
P. Borgesen
Department of Systems Science and Industrial Engineering,
e-mail: pborgese@binghamgton.edu
Binghamton University
, P.O. Box 6000 Binghamton, NY 13902-6000
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D. Blass
P. Borgesen
Department of Systems Science and Industrial Engineering,
Binghamton University
, P.O. Box 6000 Binghamton, NY 13902-6000e-mail: pborgese@binghamgton.edu
J. Electron. Packag. Sep 2010, 132(3): 031008 (5 pages)
Published Online: September 9, 2010
Article history
Received:
October 17, 2009
Revised:
June 6, 2010
Online:
September 9, 2010
Published:
September 9, 2010
Citation
Blass, D., and Borgesen, P. (September 9, 2010). "Interactions Between Flip Chip Underfill and Solder Alloy." ASME. J. Electron. Packag. September 2010; 132(3): 031008. https://doi.org/10.1115/1.4002010
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