[sdiy] 45 vs. 90 degree pcb traces

David G Dixon dixon at mail.ubc.ca
Sun Feb 16 22:32:19 CET 2020

One thing I know about sharp corners:  On an electrode, a sharp corner will
be a preferred place for electron flow.  This is why dendrites on cathodes
are to be avoided, and is why they add "leveling agents" to electro-winning
and electro-refining cells.  This is one of the laws of current
distribution.  Also, if you make a cathode blank and paint it with
dielectric paint, but leave circular spots of the metal cathode exposed,
then when you electro-win metal onto that blank, you don't form flat little
circular wafers.  Instead, you form what look like metal half-donuts with a
flat deposit in the donut hole.  This is one of the preferred ways of
electro-winning nickel, and the so-called "nickel crowns" are used as
alloying additions to steel and other metals.  I did a research project on
this way back in the day, when they were making crowns with very sharp edges
at the INCO refinery in Manitoba.  We discovered that the sharp edges were
caused by one of the organic additives they were adding to the electrolyte.
Current distribution can be a bit mysterious.  This is also why they put
rubber coverings on the edges of cathode blanks in copper electro-winning -
otherwise, a fat cylinder of copper will form all around the perimeter of
the cathode.


In any case, I would say that if on-board capacitance or current leakage is
a concern, then sharp corners -- both innies and outies -- are probably best
avoided.  However, this has nothing to do with 90-degree angles, just the
sharpness of the corners themselves.  That's why, on my crazy Excel-2003
layouts, I round all of the corners on my traces.



From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Kylee
Sent: Sunday, February 16, 2020 10:16 AM
To: Didrik Madheden
Cc: SDIY List
Subject: Re: [sdiy] 45 vs. 90 degree pcb traces


I know the comment about electrons not liking corners was in jest but you
don't want 90 degree angles on your PCB designs due to the chance they could
become acid traps when the boards are made.

> stackexchange.com/questions/445614/what-is-an-acid-trap


Now back to my TB-303,


On Friday, February 14, 2020, Didrik Madheden <nitro2k01 at gmail.com> wrote:

Jimmy Moore <jamoore84 at gmail.com> wrote:


>(Notable exceptions being RF, high speed, or high voltage layouts)


>This and another

> stackexchange.com/questions/226582/pcb-90-degree-angles>


>debunk the pcb corner myth on EMI effects.


>Is there any other tangible (audible) impact this decision could have for

>music electronics?  I think not, but I'd love to hear from other more

>experienced engineers on this (hopefully not tiresome) topic.



There's a simple and tangible, although not much audible, reason to prefer
45 degree angles. They can be routed more tightly on the board. Of course,
90 degree angles will still be perfectly fine in every non-critical



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