Resistors testing by noise, non-linearity and Electro-Ultrasonic Spectroscopy

The quality and reliability of polymer based and cermet thick film layers were tested both by standard testing methods based on the measurements of the low frequency noise spectra and AV characteristic nonlinearity and new proposed method Electro-Ultrasonic Spectroscopy. The samples were made using different resistive and conducting pastes, both laboratory and commercially produced. The results of standard measuring methods are compared with those of the electro-ultrasonic spectroscopy. This method is based on the phonon interaction with conducting electrons and on the change of the contact area among the conducting particles. The ultrasonic signal changes the contact area between the conducting grains in the resistor structure and then the resistance is modulated by the frequency of ultrasonic excitation. Resultant intermodulation voltage appearing on the sample depends on the value of ac current varying with frequency f_E and on the ultrasonic excited resistance change DeltaR varying with frequency f_U. Ultrasound-excited resistance change in polymer based thick film structures is about 0.4 mOmega to 13 mOmega, which corresponds to the relative resistance change of the order from 10^-6. For the cermet structures the resistance change is about 0.2 mOmega to 0.4 mOmega, which corresponds to the relative resistance change of the order from 10^-8. The intermodulation signal can be used as the quality and reliability indicator.