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Thermo-Mechanical Reliability of Flip-Chip Devices on Metal Backed Flex Circuits
January 9, 2007 |Estimated reading time: 1 minute
Flip-chip packaging technology has become one of the mainstream choices for future chip level package solutions to meet the ever increasing demand of miniaturization and high I/O requirements. Significant difference in the thermal expansion coefficients of silicon chip and organic-laminate substrate may subject the devices to thermo-mechanical failure mechanisms including interfacial-delamination, dielectric fracture, and solder-interconnect failure. Solder joint thermal-fatigue is a dominant failure mechanism in flip-chip device interconnects.
There is a need for predictive tools and techniques in product design for optimization and trade-off studies. Accelerated testing is a time consuming and resource intensive process. Modeling and simulation techniques are an attractive alternative for calculation of stresses, strains and life prediction. Previous studies have shown the effect of material and geometric parameters on the reliability of rigid organic laminate printed circuit boards. Both 2-D (two-dimensional) and 3-D (three-dimensional) models have been used for the analysis [Pang 1997, Syed 2001]. Usually 3-D models have been shown to give better accuracy and more realistic results as compared to the 2-D models [Vandevelde 2003, Zahn 2003]. Comprehensive models for lead-free flip-chip bump metallurgies addressing main-factor and interactions effects between underfill properties, substrateproperties with interfacial-delamination and solderinterconnect fatigue are scarce and the effects of flip-chip on metal-backed flex not well understood. In this paper the scope of geometry and material parameters and their effect on reliability has been broadened, and the effects of metal backed flex-substrate-on-interconnect reliability studied. Nonlinear implicit finite element models have been developed for thermo-mechanical reliability of leaded and lead-free flip-chip devices on metal backed flex and the variation geometry and material parameters on reliability studied.Click here to download the articleThis article was originally presented at SMTA International 2006 in Rosemont, Chicago.