Doug Brooks will be presenting at PCB West. If you want to learn a little more about PCB trace currents, his three sessions are exactly what you’ve been looking for. Doug is the President of UltraCAD and has his own PCBDesign007 column, Brooks’ Bits.

**How Current Flows in PCB Traces
Tuesday, September 15 9:00am — 12:30pm**

Tuesday’s seminar focuses on how return currents can cause signal integrity problems. This seminar will cover additional topics and concepts related to current. We have heard the definition “current is the flow of electrons.” But there is considerable confusion over “flow” as a drift velocity of electrons and flow at the speed of light. Also, people wonder how electrons can “flow” across a capacitor or out through space (EMI and crosstalk). Come listen to Brooks as he explains what is meant by the “flow of electrons” and why that definition (which has been around for 150 years) is still valid. Then learn as Brooks discusses other current topics: How can there be a propagation delay as current flows, and yet current also be constant everywhere along the loop where it flows, both at the same time? What is the “skin effect” and why do we care? What are differential currents, and do they represent special problems? What does it have to do with signal integrity? If these questions have bothered you, come hear Brooks explain how currents flow down transmission lines, terminated and unterminated, down differential traces and through wires under high-frequency conditions.

**Trace Currents and Temperatures Revisited
Wednesday, September 16 9:00am — 12:00pm**

This seminar takes a brand new look at the topic of Trace Currents and Temperatures. First, we look at the IPC 2152 curves and evaluate some equations that fit the data, comparing those equations to the underlying theory. Then we look at the same traces using an advanced thermal model (similar to the field effect models we use for impedance calculations). This gives us a baseline for evaluating the data we have so far. Then we use the thermal model to look at the sensitivities of the trace temperature to a variety of factors; adjacent traces, planes, changes in material, and time. Are the IPC curves realistic, conservative, or aggressive, and how do we know? Finally, the thermal models give us new insight into the fusing question; how much current can a trace carry before it melts? Prepare for insights and results you have not seen before. Doug is coming out of retirement specifically to share these insights with the class.

**Electromagnetic Fields and Signal Integrity
Wednesday, September 16 3:00pm — 4:00pm**

Signal integrity issues and electromagnetic fields are tightly intertwined. Much can be inferred about SI issues by visualizing the electromagnetic field around a trace or a pair of traces. In fact, are you aware that the characteristic impedance of a trace is determined more by the electromagnetic field than by the trace dimensions? Or that the propagation speed of a signal is determined by how fast the electromagnetic field can travel? Come hear how, if you learn to visualize what the electromagnetic field looks like, you can make significant judgments about related signal integrity effects.