Synthesis and characterization of fluorinated benzoxazole polymers with highTg and low dielectric constant

Abstract

Next generation microelectronic packaging requirements are driving the need to produce increasingly lower dielectric constant materials while maintaining high thermal stability and ease of processing. Efforts have focused on the synthesis and analysis of new polymers with the goals of high thermal stability [degradation temperature (Td) > 400 °C, low glass‐transition temperature (Tg) > 350 °C], low water uptake (<1%), solubility in selected organic solvents, dielectric constant less than 2.5, and low thermal expansion coefficient. These stringent combined goals have been largely achieved with flexible aromatic benzoxazole polymers. Intramolecular hydrogen bonding between pendant hydroxyl groups and the double‐bond nitrogen of the benzoxazole has been exploited to increase the polymer Tg, whereas the incorporation of perfluoroisopropyl units effectively decreases the dielectric constant. Out‐of‐plane impedance measurements on films of materials in this family (38–134 μm thick) have resulted in typical dielectric values of 2.1–2.5 at 1 MHz, depending on copolymer ratios and functionalizations. Results have been correlated with optical waveguide measurements of films 4‐μm thick to determine film anisotropy and the high‐frequency dielectric constant, and have been corroborated by in‐plane interdigitated electrode dielectric measurements on samples 0.75 μm thick. Candidate materials exhibited extremely low water uptake (0.2%) even after submersion in boiling water for several days. Dynamic mechanical analysis of the polymers enabled the determination of the influence of intermolecular hydrogen bonding on the Tg and loss tangent magnitude. Finally, the coefficient of thermal expansion has been examined and correlated with copolymer constitution. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1991–2003, 2000

High temperature polymer film dielectrics for aerospace power conditioning capacitor applications

“…Besides the potential for electro-mechanical stability at high temperatures due to their high glass transition temperatures and thermal stability, some established criteria for micro-electronic packaging applications of fluorinated polybenzoxazoles [6,10] and fluorinated polyimides [10,11] are equally important for their dielectric applications in wide-temperature power electronics. The versatility of the hydroxyl pendant in fluorinated polyimides can be utilized to develop novel, tailorable dielectrics such as PI-ADE by post-functionalization reactions.…”

“…The detailed synthesis of the fluorinated polybenzoxazoles has been described elsewhere [6]. PI-ADE was synthesized from the post-polymer reaction of a hydroxy polyimide with adamantane-1-carboxylic acid chloride [7].…”

Synthesis and characterization of fluorinated polyimides derived from novel unsymmetrical diamines

“…As well known, introduction of geometrically or molecularly unsymmetrical diamine components into the polyimide main chain has led to new polyimides with improved solubility, melt processability and other desirable properties [14][15][16][17][18][19]; additionally, fluorination is also known for increasing intermolecule space while enhancing the solubility, optical transparency and lower moisture absorption of polyimides [6,20,21].…”

Synthesis, Characterization and Properties of New Fluorinated Poly(imide siloxane) Co-polymers from 4,4′-(Hexafluoro-isopropylidene)diphthalic Anhydride

“…Polyimides containing hexafluoro-isopropylidene (6F), pendent trifluoromethyl groups [5][6][7][8][9] serve to increase the free volume of the polyimides, thereby improving various properties like solubility, electrical insulating properties and gas permeability without forfeiture of thermal stability. These groups tend to decrease water absorption, crystallinity and colour while increasing flame resistance, environmental stability and optical transparency.…”