The essential properties of polyimide films of importance in microelectronic applications are thermal and thermo-oxidative stability, dimensional stability, glass transition behaviour and the relative permittivity (dielectric constant e'). A segmented rigid-rod polyimide was synthesized from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (PFMB) in order to develop new materials for microelectronic applications. The thermal and thermo-oxidative stability were investigated by determining the thermal degradation activation energy in air (210 kJ mol- 1 ) and in nitrogen (303 kJ mol 1 ). The thermal stability was further studied through thermogravimetry-mass spectroscopy. The coefficient of thermal expansion, which indicates the dimensional stability, was measured via a tension mode of a thermomechanical analyser and doubly extrapolated to zero stresses, and was 6.98 x 10 6 c C- 1 for the BPDA- PFMB films. The glass transition temperature, measured thermomechanically, was found to be 287°C. The dielectric constant for the films, measured after ageing at 50% relative humidity for 48 h at 23C, was between 2.8 and 2.9 in a frequency range from 0.1 kHz to I MHz. The temperature and frequency dependence of the dielectric behaviour is also discussed.
Посилання на статтю:
Organo-soluble, segmented rigid-rod polyimide films: 2. Properties for microelectronic applications / Fred E. Arnold Jr, Stephen Z. D. Cheng*, Steven L.-C. Hsu,Chul Joo Lee and Frank W. Harris // Polymer. – 1992. – Vol 33. – P. 5179-5185.