Issue link: https://iconnect007.uberflip.com/i/1053050
64 DESIGN007 MAGAZINE I NOVEMBER 2018 modal resonance peaks and valleys, and the frequencies of the minima, which shift with losses. Figure 8 shows the same effect with the extracted capacitance at the corner (the plots look the same at the center as well, and there- fore, are not shown). Note the slight tilt of capacitance versus frequency curves, which is due to the dielectric loss. You can see this tilt in the measured data and simulated data alike, except the loss-less simulation (black trace), which ignores losses. Figures 9 and 10 show the impedance magni- tude and capacitance correlation for the 1-mil laminate. The expected trend was observed: the reduced dielectric thickness comes with an overall lower impedance and higher capaci- tance. The conductive losses start to attenuate the modal resonance peaks. Also, the extracted capacitance curve is flat, indicating very low dielectric losses, and therefore even the loss- less analytical Excel model correlates well. This trend continues as I switch to the 0.5- and 0.35-mil laminates: overall imped- ance decreases, resonance peaks and valleys become less pronounced, and capacitance increases. The data for the 0.35-mil laminates are shown for the RA copper, though there was no measurable difference between the board Figure 8: Capacitance extracted from the imaginary part of the impedance of the 4-mil open-edge board data. Figure 10: Capacitance extracted from the imaginary part of the impedance of the 1-mil open-edge board data. Figure 9: Impedance magnitude correlation of the 1-mil laminate data at the corner (L) and center (R).