A miniaturization of wiring on the printed circuit board is important role for the development of microelectronic devices. However, it may easily lead to the electrical short circuit of the wiring on the printed circuit board in wet and dry conditions. Thus, development of corrosion monitoring sensor is necessary. Motoda et al. ¹⁾ developed an atmospheric corrosion monitor (ACM) censer. It was composed of two different metal electrodes (Fe and Ag), and the both electrodes were insulated each other. In this case, the electrochemical signals were measured due to the generation of the thin water film on the ACM censer. Shitanda et al. ²⁾ reported an electrochemical sensor fabricated by screen-printing technique. They ²⁾ applied an electrochemical impedance spectroscopy for monitoring the impedance of electrochemical sensor during wet and dry conditions. They ²⁾ mentioned the application of electrochemical sensor fabricated by screen-printing technique for corrosion monitoring of printed circuit boards.

In this study, a corrosion monitoring sensor (CMS) was fabricated by the screen-printing technique. The impedance of the CMS was measured by a two electrode system. A 15 mg cm^-2 NaCl was dispersal on the CMS before the measurement. The temperature and relative humidity were kept at 25 ℃ and 90 % in a thermostatic chamber during the measurement. The impedance of CMS was measured during wet and dry conditions due to the deliquescence of NaCl. The impedance measurement was carried out for 17.5 hours. The DC voltage was open circuit voltage. The voltage amplitude was 10 mV. The frequency range of the impedance was from 10 mHz to 10 kHz. After the impedance measurement, the CMS was dried at 60 ℃ . In addition, the impedance of CMS was also measured at room temperature after drying.

The impedance of CMS was measured every 2.5 h, indicating that a loop related to the electrode/solution interface was observed on the Nyquist plane. The magnitude of impedance at each time was discussed with the generation of the water film on the CMS during measurements.

Reference

[1] S. Motoda, Y. Suzuki, T. Shinohara, Y. Kojima, S. Tujikawa, W. Oshilawa, S. Itomura, T. Fukushima, S. Izumo, Zairyo-to-Kankyo, 43,550 (1994).

[2] I. Shitanda, A. Okumra, M. Itagaki, K. Watanabe, Y. Asano, Sensors and Actuators B: Chemical ,139, 292 (2009).