The influence of the imidization temperature on the molecular structure and on the thermal and electrical properties of polyimide thin films is investigated. The effects of the imidization temperature on the formation of the imide rings are studied by Fourier transform infrared (FTIR) spectroscopy through the changes of the extent of imidization. However, the determination of the optimal imidization temperature shows a poor accuracy through this technique. Therefore, the quantification of several electrical properties used as probes of the imidization reaction advancement (particularly high field electrical measurements) allows obtaining a highest accuracy of the optimal imidization temperature. An optimum temperature is found at 400 degrees C while desimidization is observed at 450 degrees C. This is in good agreement with FTIR results. (C) 2010 Elsevier B.V. All rights reserved.