Posted Aug 3, 2011, by Patrick Carrier
Yes, you should care about the fact that PCB traces, when actually manufactured, end up having more of a trapezoidal shape. This is especially true when modeling those traces to determine the correct impedance. More important than the trapezoid shape itself is the resulting change in trace width. Typically, on 1/2-oz. copper, the etching process leaves the top of a trace about 0.5 mils narrower than … Read More
Tags:
HyperLynx,
impedance,
correlation,
trapezoidal traces,
measurement,
stackup
Posted Aug 2, 2011, by Patrick Carrier
Simulations should match measurements. Otherwise, what good are they? When doing signal integrity simulations, that starts with comprehensive stackup modeling. I quite often hear that stackup editor calculations don’t match measurements, but when I probe deeper, I usually find that the stackup has not been modeled properly. More often than not, the calculated impedance ends up being much lower … Read More
Tags:
stackup,
dielectric,
dielectric constant,
correlation,
measurement,
HyperLynx,
impedance
Posted May 24, 2011, by Patrick Carrier
Anyone that’s ever tried to put 75-ohm video onto a PCB stackup knows how high impedance will drive layer thicknesses. Most busses operate using 50-60 ohm impedance, which means you would typically use dielectric thicknesses of around 5 mils to achieve those impedances. But 75-ohm video on a PCB requires dielectric heights more in the 8-10 mil range. Not a big deal, but those greater heights will … Read More
Tags:
HyperLynx,
impedance,
differential,
single-ended,
stackup,
route density,
routing density
Posted Jun 29, 2010, by Steve McKinney
We’re finally on to the next logical step in our study of signal integrity - impedance. So what is impedance and why does it matter?
Impedance is a result of the physical properties that make up your PCB and the reason you care about this is because the impedance of your traces will have an impact on the signal quality. If you remember from Part 2 of this series on transmission lines, I talked about … Read More
Tags:
impedance,
Signal Integrity,
HyperLynx,
stackup
