Otmar Boser

High Frequency Behavior of Ceramic Multilayer Capacitors

The impedance of ceramic capacitors, made from different dielectric materials, was measured as a function of frequency from 1 MHz to 1 GHz. Most of the capacitors were of 0805 size and either end terminated or side terminated. The capacitance values ranged from a minimum of 50 pF to 100 nF. The high-frequency impedance measurements demonstrate that the inductance is a factor of two larger in end-terminated than in side-terminated ceramic muitilayer capacitors of size 0805. The inductance measured by two independent methods is 0.7 nH for the side-terminated 0805 capacitors. The inductance is only dependent on the geometry of the capacitor and independent of the dielectric material used. The capacitance and, in turn, the dielectric constant, remains constant for Z5U and X7R materials up to 100 MHz. For NPO materials the dielectric constant remains constant up to 1 GHz.

Rapid nondestructive testing of ceramic multilayer capacitors

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 capacitor. The standing waves are severely dampened by defects such as delaminations and pores. An undampened resonance is a good indication of a defect-free ceramic multilayer capacitor. In addition, a high-speed automated test setup was evaluated that has the potential of the testing of 180000 capacitors per hour with a sorting accuracy of about 92%. In addition, the nondestructive test setup can be integrated with the standard voltage breakdown test, reducing capital investments to a minimum. >