pcb layout

[sp]

Hai

I have a small doubt about PCB Layout

At turning point could we do route at 45 degree's , some one told in
PCB manufaturing the edge will cutout,we cannot see by eye's,we can
see that by microscope only.

suppose we do route at 90degree 's ,may be that path current will be
short

plse anybody tell

what is the correct one and reasons



Thank u

 

[John Larkin]

On Fri, 18 Jul 2008 12:45:45 -0400, "Tom Biasi"
<tombiasi***@optonline.net> wrote:

"sp" <swapnapriya2020@gmail.com> wrote in message
news:bfff5b62-83cf-40d7-8b8b-89dfb9a9fbb4@p31g2000prf.googlegroups.com...
Hai

I have a small doubt about PCB Layout

At turning point could we do route at 45 degree's , some one told in
PCB manufaturing the edge will cutout,we cannot see by eye's,we can
see that by microscope only.

suppose we do route at 90degree 's ,may be that path current will be
short

plse anybody tell

what is the correct one and reasons



Thank u



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

 

[Eeyore]

Tom Biasi wrote:

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.

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

Graham

 

[John Larkin]

On Fri, 18 Jul 2008 13:56:36 -0400, "Tom Biasi"
<tombiasi***@optonline.net> wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4880D007.CB6C78EA@hotmail.com...


Tom Biasi wrote:

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.

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

 

[DJ Delorie]

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> writes:

The high voltage boys don't like sharp features.

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?

 

[DJ Delorie]

"Tom Biasi" <tombiasi***@optonline.net> writes:

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

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".

 

[John Larkin]

On 18 Jul 2008 16:36:24 -0400, DJ Delorie <dj@delorie.com> wrote:

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> writes:
The high voltage boys don't like sharp features.

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?

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

John

 

[DJ Delorie]

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> writes:

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

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.

 

[Eeyore]

John Larkin wrote:

"Tom Biasi" wrote:
"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
Tom Biasi wrote:

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.

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

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.

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.

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.

The high voltage boys don't like sharp features.

They have their reasons !

Graham

 

[Eeyore]

DJ Delorie wrote:

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> writes:
The high voltage boys don't like sharp features.

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?

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

Graham

 

[DJ Delorie]

Eeyore <rabbitsfriendsandrelations@hotmail.com> writes:

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

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

http://www.delorie.com/pcb/teardrops/

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

I liked tape ups with curves.

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:

http://www.delorie.com/electronics/usb-gpio/

 

[Eeyore]

DJ Delorie wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> writes:
Reminds me. Which packages can do teardrops ? AFAICS only PADS
could, at least of the packages I reviewed.

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

http://www.delorie.com/pcb/teardrops/

Yes, they look nice.

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

I liked tape ups with curves.

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:

http://www.delorie.com/electronics/usb-gpio/

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