Re: Why Are There No Right Angle Traces?

Expire through coprolitic mastication.

Best regards, Spehro Pefhany

John Larkin:

There's also the fact that a diagonal line is shorter than two orthogonal ones, and a "diagonal bent" bus will occupy less PCB space.

The classical layout method was streets and avenues (chips are still done this way) on separate planes. For dense wiring, I don't think you can do better.

Nah, it's because when the electrons encounter the square corner, they can't make the sharp turn, so they spill off the end, much like the bend in the Minnesota River causes flooding every year at the bend near Mankato.

Hope This Helps! Rich

This is not true. The photo-resist process has a minimum "spot" size and that spot is the smallest radii one will ever find on the inside edge of any trace, even at obtuse angles. It varies with the equipment used from one PCB maker to another, but it is all pretty much laser etched now, so all similarly a small spot size. It is STILL there though.

There are also electrical reasons.

We never taped up at 4X with such traces either.

It isn't mere "style". There is a reason that ANY viable EDA layout software "makes sorta soft corners anyway".

Of course it can be done using fills, pours, etc. Note how a regular trace resists your stupidity, however.

Taking a close look at a modern motherboard, where one assumes those engineers are versed with things like timings and reflections, etc., one notes where they have a couple inches of trace laid down in scrunched-up fashion, in a a way of taking up "electron travel time", one will see that they NEVER use zig-zag traces, which would allow a tighter packing-in of a longer length of trace into a smaller area, using up less PCB area, which is prime real estate in this realm. NOTE that they NEVER do that. THEY ALWAYS use smooth, rounded switchbacks to take up the trace length desired.

There is a reason for that.

goddamned cross posting idiots!

Where higher currents are involved (power supplies), such factors do cause problems.

They generate things like "hot spots".

"We" (the electronics industry community) even make "fuse" elements using that very principle.

I know that it is hard passing even such simple ideas through a mere two neurons, but you do seem to do better than some here, despite only having that "resonating window" to work with. You should probably have stayed off the psycho-actives all those years ago. You should probably stop looking for them still as well. You could blow that two neuron fuse you left yourself with.

Nah, it's because when the electrons encounter the square corner, they can't make the sharp turn, so they spill off the end, much like the bend in the Minnesota River causes flooding every year at the bend near Mankato.

Hope This Helps! Rich

There are electrons in the Minnesota River?

Cut back on the Holiday cheer Rich :-) Tom

"Memory routing" does pack better with 45 degree traces. It should be obvious when right angle traces, or any angle traces, don't pack well. But there is rarely an electrical reason to avoid right angles. The PC board houses will etch anything you want.

John

If you are one of a few drawing frequent complaints here, I do advise sticking to how you did above, especially above your last line that I quoted.

I would advise against backtracking to expose who you were, and in favor of keeping up the good work!

A sharp corner can burn up your printed circuit board!

Many of the electrons will miss the turn.

See <

That's an interesting use of postscript!

Cydrome Leader:

Right. It' some 15 years that I find Don's stuff interesting.

Really? The corner has less net resistance than the straight parts.

ftp://jjlarkin.lmi.net/Strip%20Resistivity.gif

So, does a right angle get hotter than the rest of the trace? I'm not sure. It will also depend on the width/thickness ratio of the copper, which determines heat spreading, and the TC of the copper itself, a positive feedback factor. Messy.

I'll try to do a thermal image next week.

John

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

RMS counts for current waveforms /and/ current densities. If the current density is unevenly distributed, the power dissipation will be higher than the total current flow would suggest. This is the spacial version of RMS-over-time, where the power dissipation of a pulsed waveform will be higher than the average would suggest.

Of course, this will be reflected in the resistance. The average path through your right-angle strip might be naively estimated as 18.500, but the formula shows 18.559, which is slightly higher, suggesting the current is indeed uneven as Don's simulation shows.

This is quite important in my job. Say you want to induction heat a copper billet for forging. When it's cold, you get the same skin depth, current density and power density in the work coil as in the billet, so you get no better than 50% efficiency. But we know how to get >90%.

Tim

The power dissipation is I^2*R for any chunk of copper you care to select. So the square corner zone dissipates less power than an equivalent square of the main trace. Within that corner, there is nonuniform heating, but whether that is a problem or not is a more complex issue.

Of course the current density is uneven. But does that make trace heating a hazard? Peak copper temperature is the real issue.

John

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

No, the inside corner has higher current density, so it dissipates a higher power density than any other point along the trace shown. Averaged over the area of the corner (w * y), the power dissipation (W / m^2) is slightly higher than that of the rest of the trace.

Most likely not a problem since copper is a wonderful conductor and dissipates heat quickly. If you used thin copper, it wouldn't spread out so well. With too much current through a wide, light weight trace, you will definitely see the inside corner burn first. As usual, it all comes down to proper engineering.

Tim

It only affects intoxicated electrons, flowing under the influence :-)

Sometimes a picture is worth more than two pages of math.

Pretty amusing really, since this thread got going by my replying by mistake to a post from 2003!

Cheers

Phil Hobbs