Title:
A Novel Aluminum-Filled Composite Dielectric for Embedded Passive Applications
A Novel Aluminum-Filled Composite Dielectric for Embedded Passive Applications
Author(s)
Wong, C. P.
Xu, Jianwen
Moon, Kyoung-Sik
Tison, Christopher K.
Xu, Jianwen
Moon, Kyoung-Sik
Tison, Christopher K.
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Abstract
This paper presents the development of a novel aluminum-
filled high dielectric constant composite for embedded passive
applications. Aluminum is well known as a low-cost and fast
self-passivation metal. The self-passivation forms a nanoscale insulating
boundary outside of the metallic spheres, which has dramatic
effects on the electrical, mechanical, and chemical behaviors
of the resulting composites. Influences of aluminum particle size
and filler loading on the dielectric properties of composites were
studied. Because of the self-passivated insulating oxide layer of fine
aluminum spheres, a high loading level of aluminum can be used
while the composite materials continues to be insulating. Dielectric
property measurement demonstrated that, for composites containing
80wt%3.0 maluminum, a dielectric constant of 109 and a
low dissipation factor of about 0.02 can be achieved. The dielectric
constant of epoxy-aluminum composites increased almost 30 times
as compared with that of the pure epoxy matrix, which is about
3.5. Die shear tests showed that at such loading level, materials still
had good processability and good adhesion toward the substrate.
Bulk resistivity measurement, high-resolution transmission electron
microscope (HRTEM) observation, and thermogravimetric
analysis (TGA) were conducted to characterize the aluminum powders
in order to understand the dielectric behavior of aluminumfilled
composites. Bimodal aluminum-filled composites were also
systematically studied in order to further increase the dielectric
constant. Ouchiyama–Tanaka’s model was used to calculate the
theoretical maximum packing fraction (MPF) of bimodal systems.
Based on the calculation, rheology studies were performed to find
the optimum bimodal filler volume fraction ratio that led to the
best packing efficiency of bimodal fillers. It was found that the
viscosity of polymer composites showed a minimum at optimum
bimodal filler volume fraction ratio. A high dielectric constant of
160 (@10 kHz) with a low dissipation factor of less than 0.025 was
achieved with the optimized bimodal aluminum composites. The
developed aluminum composite is a promising candidate material
for embedded capacitor applications.
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Date Issued
2006-05
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