How to neck down trace width?

[ckaven]

I am rather new to PCB layout (meaning most of my designs so far have been fairly simple). I am working on my first USB layout and the manufacturer examples all show a small trace width leaving the IC pad and then increasing to ~27mils then decreasing at the USB connector. I have also seen these types of traces in power applications. How do you achieve this layout technique in Ultiboard without the use of copper pours? Or if anyone has any other ideas on proper USB layout, maybe a tool or feature of Ultiboard I am not familiar with that makes differential traces easier to route. Attached is an illustration of the technique I am trying to achieve.

Thank you for your time

[JasonF · Accepted solution]

This can be done in several different ways.

One is the built in auto trace narrowing feature in Ultiboard. Within the Global Preferences under the PCB Design tab there is an Auto trace narrowing checkbox. Enabling it should produce your desired result as it is designed to decrease the traces width automatically to prevent any DRC errors. Because this relies on DRC and the minimum trace width settings you need to ensure you have properly set them in the netlist editor for all nets.

Another method is to change it while routing. If you switch the width using the combobox on the draw settings toolbar, the trace width will immediately change as you continue routing. I find this method is easiest with the Follow-me router as you can set exactly where the trace width changes.

The final option is to change it once the routing is nearly complete. You can go back and double click on any section of a trace and change the trace width in the General tab.