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36 The PCB Design Magazine • November 2014 VERTICAL RESONANCES IN CERAMIC CAPACITORS continues Ceramic capacitors we use for power distri- bution bypassing have multiple metal plates in- terdigitated and embedded in a high dielectric constant ceramic material. As shown in Figure 3, the capacitor plates connect alternating to ver- tical metalized terminals at the two ends of the capacitor body. High-density ceramic capacitors can have hundreds of these capacitors plates. Between adjacent capacitor plates, which are connected to the opposite terminals, there are thin ceramic layers. Many of these sections are connected in parallel by the vertical terminals, conveniently increasing the total capacitance and reducing the inductance as well as the se- ries resistance of the part. Without cross sec- tioning we don't know how many conductive plates a particular capacitor actually has, but to model the resonances we see in the measured data, it is really irrelevant. The model in Figure 2 uses a 10x10 matrix: 10 capacitor plates on each terminal and 10 dielectric segments along the plates. L c and R c represent connection in- ductance and resistance between the capacitor's terminals and the observation point: these are quiet power Figure 2: Bedspring model from [1] .

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