Piezoelectric Response of Ferroelectric Ceramics Under Mechanical Stress.

摘要

Manufacturers are constantly developing increasingly miniature, ferroelectric multi-layer ceramic capacitors, survivable under progressively harsher mechanical stresses. However, the piezoelectric response of the bulk Barium Titanate- based dielectric in such capacitors has not yet been addressed for shocks above 3,000 g. Thus, the current research developed a finite element capacitor model and modified an established constitutive relationship to calculate the capacitive response under high-g drop impact. Scanning electron microscope and impedance analyzer data confirmed the flexural mode of mechanical failure, while the newly applied RC capacitance measurement technique detected discreet partial and complete electrode separation from the terminal, corresponding to the board oscillation frequency. The experiments detected an up to 10% increase in capacitance during 24,000 g shocks, while the numerical model predicted the electromechanical response to within 2% of the nominal capacitance value, closely matching in waveform to the experimental data. When the flexural failures were completely prevented and the capacitance response was reduced by 81% with completely restricted board flexure, the electromechanical response was still detectable during drop impacts generating 3,000 g peak accelerations. While preventing board oscillations may reduce mechanical failure probability, unaddressed piezoelectric response of ferroelectric capacitors may still cause significant intermittent reliability issues above commercially relevant conditions.