Layout curved tracks/traces


#21

I just quit… did you read my previous post?..
bust just from what I see the paper if is talking of measurements up to 1GHz … are we talking of RF or not…
re-quitting this time not coming back :smiley:


#22

It is difficult, if not impossible to measure radiated emissions from any trace corner.

Pretty clear, no?

If you have other test data, it would be good to see. I haven’t seen any other testing with a similar level of detail.


#23

Come on … you don’t read my posts!
my last sentence in this conversation:
you can check your signal integrity from the out without the need to have the ability to measure any radiation…
that is much clear!


#24

Sorry, I didn’t understand that - what is clear?

From the paper, it said that the measured radiation didn’t match the computer modeling, if that is what you mean. I would always trust measured data over computer models, the models are a useful guide but not definitive.


#25

Oh my, what did I do! X"D

Sorry about the arguing I rekindled, but happy to learn about those opposing camps, I had no idea that it was just an EE rule of thumb/myth :slight_smile:


#26

No worries, I find it interesting to take a deep dive into some of these things and really find out what is what.


#27

Well, as a technician, I can tell you that I have worked repair on both of these design concepts.

We were talking about it one day, and I reached into our repair backlog and said, “Looky! How about this one!”. There were 90 degree corners all over it; been working just fine for decades.

My own opinion, I don’t think it matters so long as the magnetic interaction between nearby traces/devices is given attention. And, this does mean 90 degrees rotation for some parts.


#28

RF is not a really good word here. Accourding to wikipedia RF starts at a few kHz. (Yes it also states it can be as high as a few hundred GHz)

As far as i know even universities currently struggle to qualify EMC for >10 GHz. (At least if i can trust my professors.) A paper about emissions in the 1 GHz range from a few years ago is really not bad.

I have to agree with @bobc. Science without data is not science.
(But yes @maui has a point. Engineers sometimes use best design guidelines even if they do not know if it is necessary. If it is more expensive to question such guidelines than to follow them they are followed without questioning. This is the difference between science and engineering! Engineers are happy if it works a scientist always wants to know why/why not.)


#29

Please keep this thread polite…:cop:

Thinking about the problem, the extra copper at the right angle is going to become significant when the track width gets to about 1/10 of wavelength, which means well above 10GHz for most cases
A pair of 45 degree bends has much less stray copper, so going even further to curved track achieves little and makes it hard to maintain track to track or track to adjacent groundplane distance accurately.

For me, curved tracks would mainly be for replicating old hand drawn PCBs. Electrons are not like cars on a racetrack braking for bends.


#30

but if someone says that the referred paper is reliable to describe RF signals and to give pcb guidelines, then he is wrong because the paper is covering signals up to 1GHz, which are a low side of the RF spectrum and the easy part… in my experience signals up to 1GHz are just referred as high speed signals…

I’m not saying that Ti engineers are writing their guidelines without scientific data as someone else in the thread… the opposite!
I just said:

you can easily test your signal loss from the in/out path without the need to measure any EMC radiation at all…
so your model could even not exists, but your data can be scientific anyway…

If you can reach your professor, I would be glad to have an academic point of view in this post referred to signal from 1GHz up to hundreds…
but stop pulling me in this thread… as I already stated out I don’t like to be in anymore …


#31

Like I said in the thread at . . . . [Solved] Multi-purpose pins on microcontrollers

Dale


#32

The line in that paper that basically says “vias are much worse than any right-angle bend in the trace” should settle the discussion, right?


#33

More reasons for having arcs.

  • arcs are almost a must for flat-flex boards. Because sharp concave corners create stress concentrations, making a perfect starting point for fatigue cracks. Sure, 45 degree turn is much better than 90 degree turn, but it does not eliminate the problem.

  • arcs are very desirable in high voltage boards. There, sharp convex corners are places where corona discharge is likely. Not only does it reduce the breakdown voltage, it can be a long-term reliability problem. If there is a subtle corona discharge, it causes insulator degradation nearby, which can lead to carbonized short after a long period of time. Similar to what happens in this video: https://youtu.be/QRHNZaVLSh4


#34

No? It’s already well established that vias create signal integrity problems for signals in the GHz range. Vias being worse than right angle bends doesn’t mean right angle bends aren’t a problem also.

The thing that gets me is that a HUGE number of high speed dev boards out there, from ADCs to DACs to comparators to flip flops, from every manufacturer, use rounded traces. So either rounded traces are a myth and the hardware designers from every major IC manufacturer in the industry have bought into the lie, or there’s something to it. Either way, I don’t understand why there’s this resistance to add that functionality to KiCad. It can’t hurt.


#35

Well, it is on the wishlist, there is not much more we can do here. https://bugs.launchpad.net/kicad/+bug/1577958

Hmm, adding code always creates new bugs, more complexity for users and developers. It’s always a question of cost/benefits, economics applies to free software as well. If you look at the other 350 or so feature requests, which features are more or less important? Everyone will have their own view.

There is a sort of voting system, if you click “also affects me” it adds to the bug “heat” index. If we sort by that we get most popular wishlist requests

The top one is teardrops. Curved tracks is not very high, but in the top 75. However, there is not much relation to the popularity and what gets implemented, that depends on whether it’s an itch developers also wish to scratch.


#36

have a look at

The code has been already developed, but not merged…


#37

[quote=“suicidaleggroll, post:34, topic:658”]
The thing that gets me is that a HUGE number of high speed dev boards out there, from ADCs to DACs to comparators to flip flops, from every manufacturer, use rounded traces. So either rounded traces are a myth and the hardware designers from every major IC manufacturer in the industry have bought into the lie, or there’s something to it. Either way, I don’t understand why there’s this resistance to add that functionality to KiCad. It can’t hurt.
[/quote]I remember reading, pre-internet, about some researchers coaxing single electrons down traces. That had to be curved ‘like sine waves’. I’ve searched and can find no reference to this research now. It may have been debunked or it could be I’m old enough to remember anything I want, factual or not. :wink:

It does make me wonder if pushing certain speed and boundary sizes will make this kind of thing necessary.


#38

In school we learned electric fields are stronger at sharp turns. The way to look at it is the perpendicular lines of force get closer together. There is a reason spark generators have pointed ends. Also lightning rods a are pointed for similar reason.


#39

When I teach kicad I tell my colleagues that electrons skid at right angles.


#40

Strength of electric field alone doesn’t predict radiation.

I hope you’re joking :smiley: