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NOVEMBER 2018 I DESIGN007 MAGAZINE 73 thinner laminates produce lower impedance. The inductance comparison in Figure 27 dem- onstrates how the different laminates com- pare in their frequency ranges. In the entire frequency range, the 4-mil laminate produces the highest inductance. With thinner lami- nates—and also because the copper thickness now becomes comparable to the dielectric thickness—the order of inductance depends not only on the laminate thickness, but also on the copper weight and frequency. Below 1 MHz, the highest inductance comes from the thinnest dielectric, but just because this lami- nate had 2-ounce copper. Above 10 MHz, the order of curves follows the laminate thickness. Conclusion I showed the correlation of impedance and extracted capacitance and inductance values of 6x6" laminate test boards with open and shorted edges. The correlation was shown with three different simulation tools for the open- edge boards, including loss-less analytical for - mulas to capture the capacitive downslope of impedance magnitude curve, but without the small tilt due to dielectric losses. They also cap- ture the peak frequencies of resonances prop- erly, but due to ignoring losses, the peak/val- ley values and valley frequencies are off. The causal SPICE models and professional hybrid solvers capture all of those effects correctly. Figure 26: Comparison of PowerSI simulated impedance magnitude with different laminate thicknesses at the center (L) and corner (R) of boards. Figure 27: Comparison of PowerSI simulated inductance with different laminate thicknesses at the center (L) and corner (R) of boards.