pcb layout

It is common practice not to turn a trace less than 90 degrees. Tight turns make pockets in the wave soldering process. Sharp edges may be a concern in super high frequency application also. Tom

Neither matters.

John

Surely you mean more than 90 degrees ? Unlesss I completely misunderstood the question.

Graham

I believe he was referring to acute angles. When I designed boards it was common practice not to turn at acute angles for the reasons I mentioned. But as John says, It really is not all that important.

Tom

The prohibition on 90 degree corners is mostly esthetic/historical. It does tend to produce inefficient packing in tight layouts. Electrically, below 5 GHz or so, a 90 degree bend is pretty much invisible.

The high voltage boys don't like sharp features.

John

PCB uses round-end traces all the time, so even on 90 degree corners the outside edge has a (width/2) radius bend in it. What do other EDA packages do? Do any of them use sharp outside corners?

The radius is not necessary. It was used back in the tape and light table days but for CAD progs its just style.

Tom

Actually, in PCB we use round ends because otherwise we have to compute gerber apertures separately for each trace angle and end junction.

Maybe you're confusing "round end caps" with "the trace bends" ? I mean the former when I say "round ended traces".

Sounds like a good enough reason for me.

Tom

Probably an artifact/bonus of using round Gerber aperatures to draw the traces.

John

Well, yes, I know that. I wrote its gerber exporter. I was curious if this was standard practice, or if squared-off corners were common also.

I liked tape ups with curves. I still have a box of Brady and other brand stuff. The Brady pads were the best IMHO but I used a UK brand tape whose name eludes me at this second.

They have their reasons !

Graham

Reminds me. Which packages can do teardrops ? AFAICS only PADS could, at least of the packages I reviewed.

Graham

PCB does teardrops, at least, it does the kind I like (another of my plugins). I put a page here:

I suppose there are other types of teardrops, but these solved the particular problem I had (copper cracking on inside corners during rework).

You'll like PCB's global puller, at least, when it doesn't scribble all over your board ;-)

Here's a sample board that uses both teardrops and the puller:

Yes, they look nice.

Not using Linux yet here at the moment. I did sample Ubuntu for a bit but I then had another use for the machine.

How 'intuitive' do you find PCB ? I recenly did some boards using ExpressPCB and I quite like it's 'almost manual' approach. It was almost a bit like tape-up with aids which suited my needs for a simple job very well.

Graham