NEPCON West - Fiberoptic Expo Conference Proceedings


Authors: Michael Todd and Frank Shi
Company: University of California
Date Published: 12/3/2002   Conference: NEPCON West - Fiberoptic Expo

Abstract: High frequency microelectronic device packaging requires the use of substrate and encapsulation materials having a low dielectric constant, low dielectric loss and high volume resistivity. Most packaging materials are polymer-ceramic composites. A clear understanding of the broadband dielectric properties of composite materials is thus of great current importance for the effective development of high frequency packaging materials and optimized package design.

Towards this goal, a general framework for understanding the dielectric properties of packaging materials was recently developed in which the dielectric constant of polymer-ceramic composite materials is characterized by the electrical properties of the polymer phase, the filler phase and an interphase region within the composite system. We have investigated the dielectric properties of the polymer-filler interphase region, which represents a region of polymer surrounding and bonded to the surface of each filler particle having unique dielectric and physical characteristics.

Bringing together the atomistic characteristics of molecular dipole polarization and interfacial chemical bonding with macroscopic dielectric qualities has allowed us to begin to define a comprehensive model to understand the properties of polymer materials at bonding interfaces. Our results show that the interphase region surrounding the filler particles of polymer-ceramic composites possess a dielectric constant less than that of the bulk polymer matrix.

Furthermore, the value of the dielectric constant of the interphase region can be explained by the change in chemical polarizability of the polymer caused by the chemical bonding of the polymer to the filler particle surface. These results are supported by experimental evidence and lay the groundwork for a comprehensive explanation and determination of the overall effective dielectric properties of packaging materials for a wide range of electrical, electronic and RF applications.

Key words: dielectric constant, interphase, composite.

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