Dielectric breakdown and molecular orientation of poly(4,4′-oxydiphenylene pyromellitimide)

The electrical breakdown of polyimide (PI) thin films was investigated in the thickness range 0.8-2 μm and in the temperature range -100-200°C, by taking advantage of self-healing. Two kinds of PI films were formed by vapor deposition polymerization (VDP) and coating of polyamic acid precursor in solution, VDP and S films, respectively. Breakdown characteristics of the films in the micron thickness range can be divided into two temperature regions. In the high-temperature region, the thermal process is operative and in the low-temperature region, the avalanche process seems to be predominant probable as compared with the thermal process. The breakdown characteristics were compared between VDP and S films. The results were explained with reference to the infrared reflection absorption spectroscopy of PI which indicates the crystallization and the molecular orientation of VDP film.