Towards model-based engineering of optoelectronic packaging materials: dielectric constant modeling

Increases in data transmission speeds of optoelectronic devices have consequently increased high-frequency requirements for optoelectronic packaging materials including substrate. EMC/EMI shielding, adhesive and encapsulant (molding and underfill) materials. Most of those materials are polymer/filler composites, and critical materials properties for the device design and packaging include the effective dielectric constant, dielectric loss and their frequency and filler concentration dependence. This work presents a systematic theoretical investigation of the effective dielectric constant of polymer/filler composite materials, and its dependence on the filler concentration, the filler/polymer interaction, and the size of fillers. Our results demonstrate that, in contrary to the prevailing views, the filler concentration dependence of the effective dielectric constant is non-monotonic. Depending on the dielectric constant ratio between filler and polymer matrix, and the degree of interaction between filler and matrix, the effective dielectric constant exhibits an extreme as a function of filler concentration. In addition, our model is demonstrated to contain the Maxwell-Wagner formulation as an asymptotic limit, The present results have significant implications to the targeted formulation of optoelectronic packaging materials. (C) 2002 Elsevier Science Ltd. All rights reserved.