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PCB design questions


ganchan
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I'm analyzing some professional boards of analog / digital drum machines and some of that have always 90° curves with two 45° angles instad diagonal traces.

This make the traces longer so they do not chose the short line possible.

I know that on thin traces to avoid problem during pcb realization a double 45° angle is a best practice instead a 90° angle, but i'm wondering why i should design all my traces like the first image A instead the second B.

In small space and short traces this can be a well organized north south, east west design, but on long traces this can make them a lot longher.

A

56b7a04b61fbf_TracetypeA.png.c171ce223ad

B

56b7a04fa2898_TracetypeB.png.b4b1cbab308

Edited by ganchan
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Still just a semi-amateur PCB designer here. 45 degree bends aren't actually needed, this is a bit of a myth. Maybe when your signal starts to get into the microwave GHz frequency it helps, but probably not relevant for our sort of application. Maybe with press'n'peel layouts or CNC routed PCBs there's an added advantage? But I do it anyway as it helps me to keep track of where things are and will take up less board due to "cutting corners."

What is important though is the type of signals overlapping. If you had a high impedance audio line running under a clock for example, that would be bad and you would likely get crosstalk. Ideally you should strive for as little overlap as possible between layers, with solid ground planes poured underneath. This is especially important when the signal is fast, long or needs good transmission, such as a clock or digital data line.

In your example above I'd definitely go for B.

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On 7.2.2016 at 9:35 PM, ganchan said:

I know that on thin traces to avoid problem during pcb realization a double 45° angle is a best practice instead a 90° angle, but i'm wondering why i should design all my traces like the first image A instead the second B.

It is actually the other way round. Noise issues apart, there is another reason to go for variant B instead of variant A: assuming that you want to achieve a "tight" layout that requires as little board real estate as possible, it is never a good idea to have parallel traces on the front and the back side, because you have nowhere to cross these traces. Usually, it's a smart move to dedicate the front side of the PCB to say horizontal traces, whereas the back side will then mainly hold the vertical traces. This approach helps to avoid vias and reduces the amount of headache you will have once the layout gets a little more complicated (i.e. you are using more than a few components).

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