Transactions of the ASME, Vol. 124, pp. 184-187, September 2002

Hygro-Mechanical Durability of Underfilled Flip-Chip-on-Board (FCOB) Interconnects

J. H. Okura
Nokia Mobile Phones,
Connection Drive 6000, Irving, TX 75039

A. Dasgupta
CALCE Electronic Products and Systems Consortium
University of Maryland
College Park, MD 20742

J. F. J. M. Caers
Philips Centre for Manufacturing Technology,
P. O. Box 218, 5600 MD Eindhoven, The Netherlands


The effect of constant temperature and humidity environments on the durability of interconnects in underfilled Flip-Chip-on-Board (FCOB) assemblies is investigated in this study. Polymeric underfills, used to enhance thermomechanical durability of the interconnects, are found to create new failure modes due to hygromechanical swelling. Based on experimental observations, the failure mechanism is hypothesized to be cracking of intermetallics, which have weakened due to thermal aging. Pseudo 3-D finite element analyses are conducted to quantify the moisture absorption and diffusion through the polymeric underfill, and the resulting hygromechanical viscoplastic stress history. The simulations are combined with accelerated aging tests to assess in-service durability in hot, humid environments. Model predictions are compared with results of accelerated life tests available in the literature.

Complete article is available to CALCE Consortium Members


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