Does trace width affect much in high-speed design (>100Mz

[doubledribble]

Does anybody know: is that necessary to calculate the trace width in order to get disired impedence? Or just determined by the space in pcb board?
In a word, how to deside the trace width in a pcb layout?


Thanx

 

[hcet]

Re: Does trace width affect much in high-speed design (>1

width and kind of trace matter, also the material of your pcb. look here (w**.polarinstruments.com) to get some info.
regards.

 

[djalli]

>100MHz yes of course if you want precision. Definitely!

How much over 100MHz we are talking here?

 

[btbass]

The impedance of the trace is set by its width and thickness and distance from the return path, normally the power plane. I suggest you get Hyperlinx to help you design high speed boards.

 

[House_Cat]

Re: Does trace width affect much in high-speed design (>1

The trace width on a PCB is a tradeoff between available space and the the desired electrical properties.

The impedance of the trace is a function of the trace width, the trace thickness, the distance to the return path, and the dielectric loss of the material above and below the trace. The material above the trace would be solder mask or air for a surface trace, and the dielectric of the prepreg or core material of the board for an inner trace.

Another factor in deciding upon a trace width is skin effect. As the frequency rises, the losses in a trace rise not only because of dielectric loss, but also because of the increasing resistive loss due to skin effect. Wider traces are used to overcome some of the skin effect loss. The distance to the return path for the dielectric in use is then changed to keep the impedance at the desired value.

There is some excellent reading material in books by Howard Johnson. He also has material available free on his web site. Read some of the articles at:

**broken link removed**

There are also some formulae that you can plug into M@thcad or M@thematica to calculate impedance and other trace characteristics at:

**broken link removed**

 

[lyric]

Yes.You should consider trace width,distance between trace and reference plane, dielectric constant, etc.

 

[chinara]

Re: Does trace width affect much in high-speed design (>1

What my supplement is that the skin effect only has significant effect while the freqence is over 1G. At same time, when the freqence is over 1G, the width of trace is never less than 8 mil, or the signal amplitude will decay significantly.