I'm designing a PCB for USB 3.0, the specifications for Differantial impedance comes at 90 ohms with a tolleance of +- 5 ohms.

I've used different calculation tools but when I have to hold these specs my traces ar really wide in comparison to the usb3.0 printed circuits that I have as example, even with the same PCB material.

I searched the internet and found some specs for the wideness and spacing but if I put them in the calculation tool I'm at 170 ohms..

Anyone have an idea how manufacturers solve this?

I also had a question to manufacturer putting multiple Vias from top layer to bottom layer. In the past I read some articles about this but can't seem to remember what it's for, anyone have an idea about that?

Here is an example : http://www.aspisys.com/netqe128.jpg

Thanks

Kind Regards

Joris Aerts

I'm designing a PCB for USB 3.0, the specifications for Differential impedance comes at 90 ohms with a tolerance of +- 5 ohms.

I've used different calculation tools but when I have to hold these specs my traces are really wide in comparison to the usb3.0 printed circuits that I have as example, even with the same PCB material.

I searched the Internet and found some specs for the width and spacing but if I put those into the calculation tool it shows 170 ohms..

Anyone have an idea how manufacturers solve this?

I also had a question about manufacturers putting multiple Vias from top layer to bottom layer. In the past I read some articles about this but can't seem to remember what it's for, anyone have an idea about that?

Here is an example :