Electromechanical Resonances in Ceramic Capacitors and Their Use for Rapid Nondestructive Testing

A rapid nondestructive test method for ceramic multilayer capacitors made from piezoelectric materials such as barium titanate or lead‐containing materials is described and evaluated. The test method is based on the internal excitation of standing acoustic waves in the capacitors. The standing waves are severely dampened by defects such as indentations and delaminations or warped electrodes. An undampened resonance is a good indication of a defect‐free ceramic multilayer capacitor. This finding was used in a nondestructive test setup to evaluate about 1000 capacitors. Through metallographic (cross‐section) examination, a sorting accuracy of 2% false accepts and 8% false rejects was determined for the highspeed test setup. The test setup has the potential to test over 100 000 capacitors an hour. [Key words: capacitors, nondestructive testing, multilayers, mechanical properties, electrical properties.]