Capacitance adjustment process in multilayer capacitor mfr. - uses capacitance meter and reference standard to generate electrical signal controlling laser based trimming tool

摘要

The capacitance of a capacitor (1), held in a jig able to rotate (14) and move laterally (13), is measured in a capacitance bridge (6). Using an a.c. to d.c. converter, a feedback signal to drive the de-metallising tool is generated from a capacitance reference and an associated control circuit (7). The signal produced by the member circuit is sampled and its value is stored in a memory. The value is compared with that previously stored from a reference capacitor. A difference signal is produced which drives the cutting tool via a pre-calibrated counter. After the predetermined time has elapsed, the new capacitance is compared again with the reference. The laser cutting tool drive is calibrated to ensure a constant correspondence of capacitance change and activation time.