No abstract

No abstract

Commercial electronic devices require shielding solutions that ensure electromagnetic compatibility (EMC) while accounting for effects of specific enclosure structural features such as seams, vents, and port dimensions. In practice, suitable EMC materials combine with the device operating characteristics to determine an overall shielding response. To optimally couple plastic design practices with EMC requirements, both polymer materials science and electrical engineering concepts, must be considered. Use of extrinsically conductive polymer (ECP) formulations for electronic applications has advantages in that they can be directly molded to a desired shape and serve to provide the necessary shielding while also meeting mechanical integrity requirements. Shielding and mechanical performance can be varied via filler loading or altered through wall thickness changes to satisfy demands associated with a particular device. Injection-moldable ECP polycarbonate-based formulations can attain average shielding effectiveness (SE) levels of 50-60 dB through 2 GHz at 2-mm thickness as measured using ASTM D 4935 procedures. These values vary with thickness, and SE improvements of 10-20 dB are observed when increasing from 1 to 2 mm. Additionally, resultant mechanical properties of shielding composites are strong functions of overall fiber content. These interrelated material and shielding characteristics, which form the basis for filled conductive polymer use within practical enclosure shielding designs, are described.

Organic polymeric materials, often used as ceramic processing aids to assist in the fabrication of green bodies, are thought to be of a temporary nature, being easily removed by thermolysis at temperatures between 250" and 600°C. The interaction of various poly(viny1 butyral) binders with fine, high-purity alumina powder was investigated using variabletemperature Fourier-transform infrared spectroscopy and thermal gravimetric analysis. It was found that there was interaction between the functionality of the polymers and the surface of the alumina powders. If these interactions are strong enough to persist to initial sintering temperatures, the polymers would not then be merely innocuous temporary processing aids, but could have an effect on the development of ceramic microstructures. [