Early fatigue failure of solder interconnects in electronics packaging is known to be due in part to differences between the coefficients of thermal expansion (CTE) of circuit boards and the attached electronic dies . In flip-chip packaging, the CTE mismatch is mitigated by the use of underfill adhesive, which is typically a highly filled epoxy resin system. Micro-scale filler particles used traditionally in the adhesive compositions have been effective in providing the desirable low CTE underfills for electronic packaging. However, high concentration of large filler particles in these underfills is problematic. Nano-scale inorganic filler particles can produce a similar large improvement in properties at lower concentrations, primarily because of their large surface to volume ratio. However, nano-scale dispersion of filler particles in liquid resins at the volume fractions required to substantially reduce the CTE value also dramatically increases the viscosity of the compositions leading to unfavorable processing characteristics. We report here on epoxy resin nanocompositions that have exceptional thermal and mechanical properties as well as excellent processing characteristics. These compositions are based on low viscosity multifunctional epoxy resins containing pristine or functionalized Boehmite (Alumoxanes). They were prepared at ambient temperature by ultrasonic dispersion process. The particle size of the inorganic filler in the uncured liquid dispersions was not in the nano length scale. However, we have observed that curing of such compositions at the processing temperature of 150�C induces a dispersion of the Boehmite particles (both functionalized and pristine) on the nano-scale. Because of the larger than nano scale dispersion in the uncured state, these compositions showed excellent processing characteristics. The CTE of the resulting nanocompositions at 35 weight percent of Boehmite nano particles was about 25 PPM /�C. We will show that nano-scale particles dispersion is key to the development of the thermomechanical properties of the compositions.

Organic/inorganic hybrid nanocompositions of pristine and functionalized boehmite with amine-cured tetraglycidyl meta-xylenediamine resin

243rd National Meeting (2012)

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