Distributed Circuit Modeling of Multilayer Capacitor Parameters Related to the Metal Film Layer

Linkage between the distributed-circuit capacitor model and multi-layer capacitor structures is demonstrated. Capacitor inductance leading to self-resonance in standard metallized polymer capacitors arises from lead and package inductance and can be represented by lumped inductance external to the capacitor modeling in this paper. Distributed internal capacitor inductance is negligible in metallized polymer capacitors for most applications and therefore is not considered in the analysis. Two different distributed-circuit topologies, both of which arise in practice-one by design and the other by degradation-are considered. One has the two connecting electrodes on opposite ends of the capacitor and the other has both input electrodes on the same end. The electrical performance of the two connection topologies is compared using numerical 10-stage lumped element modeling. Cross comparisons are made using diffusion equation modeling for the single-end connection topology. Strong correspondence between results from numerical lumped element distributed approximations and from diffusion equation analysis for the single-end connection is demonstrated up to 100MHz, this inferring similar accuracy for lumped element modeling of the double-end connected capacitor topology. The results show that the two connection topologies exhibit similar behavior up to at least the typical self resonance frequency of the capacitor, except for the cross-dielectric voltage and cross-width power dissipation profiles which are fundamentally different. Voltage drop across the metallic films is shown to be small in normal steady state operation. The contribution of the metallic film to the equivalent series resistance is shown to be constant with frequency up to a frequency where distributed - filtering becomes significant. Beyond this, both equivalent series resistance and capacitance fall with the square root of frequency for the single-end connected capacitor. Similarly, the dissipation factor initially rises in direct proportion to frequency and power dissipated in the metal film increases with the square of frequency. Progressive disconnection of distant metal film with frequency, due to filtering, is shown to be responsible for the changes in these relationships and the parameters of the capacitor.