Synthesis and Properties of Soluble Copolyimides Containing Phthalazinone Moieties for Flexible Copper-clad Laminates

Abstract

Soluble aromatic polyimides with good comprehensive properties are potential materials for microelectronics. A series of soluble copolyimides containing phthalazinone moieties were prepared from 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)] (2H) phthalazin-1-one, 4,4'-diaminodiphenyl ether, as comonomers, and appropriate aromatic dianhydrides by one-pot solution polymerization in sulfolane. The corresponding copolyimide films had a good balance in thermal, adhesive and dielectric properties. The resulting copolyimides showed good solubility in polar aprotic solvents such as N-methyl-2-pyrrolidinone (NMP) and N, N-dimethyl acetamide and high thermal stability with glass transition temperatures in the range of 252—266 ° C and decomposition temperature at 5% weight loss being above 505 °C in nitrogen. The copolyimide solutions in NMP were processed into flexible films which exhibited good adhesive property (1.66—2.28 N mm-1) and showed a predominantly amorphous nature measured by wide-angle X-ray diffraction. These free-standing films had dielectric constants of 2.3—3.1 (100 kHz) and low water absorption in the range of 0.76—0.93%. These outstanding properties make the obtained copolyimides good candidates for polyimide-based flexible copper-clad laminates.