Why are 90° angled traces bad?

[colhany]

Is there a scientific or practical reason why we avoid 90° traces? I have heard Robert and a lot of other experienced PCB designers say that they should be avoided. But according to Lee Ritchey, the fact that they cause reflections is a myth. So what is the real reason?

Thank you

[qdrives]

According to Rick Hartley it starts to be a (little) problem at multiple GHz frequency. So that is the scientific part.
Practically you might consider acid trap, but that too should be at angle > 90
"But we learned it that way"

[suleymancskn]

Hi colhany, you can check the link below.

https://resources.altium.com/p/pcb-r...0-degree-angle

[robertferanec]

My opinion - Electrically it may not be a problem for standard boards, However:
- it may not be practical to use 90Deg, it may need more space for layout (a diagonal is shorter than a horizontal + vertical line)
- if you use 90deg, other engineers may comment on it (many comments may be negative and say it is a bad layout)
- when you have a look around, designs normally do not use 90deg corners

so I simply don't use them

[colhany]

Thank you everyone