Dielectric Constant Polyimide Research Articles

Fibers from a low dielectric constant fluorinated polyimide: Solution spinning and morphology control

Control of the internal morphology of wet-spun fibers from a fluorinated polyimide has been achieved by varying the rate of polymer coagulation through adjustments in nonsolvent/solvent miscibility and precipitation strength of the coagulation bath. Filament internal morphologies ranged from very porous or sponge-like to fully solid. Intermediate structures included fibers containing a spongy core with a nonporous skin, sponge-like fibers containing large voids, and a relatively solid material containing randomly spaced small voids. The cross-sectional shape of the fiber is dependent upon the coagulation process as well as the volume contraction of the initial extrudate. Drawn fibers (3×) retained the original asspun cross-sectional shape and also lost porosity. Mechanical properties of poly(6FDA-4BDAF) fibers have an inverse relationship to filament porosity. Maximum modulus and break strength for drawn fibers is approximately 6 CPa and 200 MPa, respectively. Asspun mechanical properties were dependent upon the processing conditions and have moduli between 0.4–3.0 Gpa and break strengths of 10–160 MPa. A dielectric constant of 2.50 for nonporous films was measured over a frequency range between 1.0 MHz to 1.8 GHz, showing little dispersion. © 1997 John Wiley & Sons, Inc.

Photo-induced deposition of low dielectric constant polyimide film for interlayer dielectric applications

The photo-assisted conversion of polyamic acid spun onto Si substrates into thin polyimide films at low temperature using a 172 nm excimer lamp is reported. Current-voltage measurements showed that the leakage current densities in the polymer were over an order of magnitude less than those obtained in films prepared by conventional thermal processing.

Optical Properties of Low Dielectric Constant Polyimides and Effects of Orientation

AbstractControl of the refractive index in low dielectric constant polyimides through modification of chemistry and structure was investigated. The optical refractive indices of several low dielectric constant polyimides were measured, and the effects of orientation on optical anisotropy were determined. Refractive index in these polyimides was found to decrease with increasing fluorine content due primarily to the low electronic polarizability of the fluorine-carbon bonds. In zone drawn polyimides, refractive index was found to increase substantially in the direction of the draw, but decrease substantially normal to the draw direction. This was explained in terms of the preferential alignment of the polymer chains.

Effect of Structural Features and Humidity on the Dielectric Constant of Polyimides

A series of aromatic polyimides and partially fluorinated aromatic polyimides were prepared and investigated to determine the structural features affecting their moisture absorption, dielectric constant, and dielectric constant as a function of relative humidity. The moisture absorption of polyimides is related to the total imide content of the polymer. Polyimides with a lower weight per cent of imide have a lower moisture absorption. Both dielectric constant and moisture absorption of polyimides can be reduced by incorporation of fluorine into the polymer. However, a minimum in moisture absorption (about 0.7 wt.%) and dielectric constant (about 2.7) is approached at about 20% fluorine by weight of the polymer.