[Pcb-bugs] [Bug 699559] Re: Wish list

[Peter C. <pc...@ca...>]

Bert, for this one, "Invalid" might be a useful status when you're done.

-- 
You received this bug notification because you are a member of PCB Bug
Team, which is subscribed to pcb.
https://bugs.launchpad.net/bugs/699559

Title:
  Wish list

Status in PCB: Printed Circuit Board:
  In Progress

Bug description:
  I don't want to sound like I am complaining, but I think 
PCB could do with a lot of enhancements. 

As a pcb design proffessional, I would be very happy to 
see a highly featured, and easy to use circuit layout 
tool, comparable to the best 'proffesional' offerings, 
which are very expensive. (And some of them are very 
poor!) 

If such a tool were available it would (I think) go a long 
way towards stimulating commercial vendors to improve 
inter-operability between the different packages. 

At this moment in time, each vendor uses their own 
proprietary file formats. This means that once you select 
a design package, you are more-or-less stuck with that 
supplier. It also means that designers cannot take 
on 'remedial' work produced using other software, which 
is not good for the customers either! 

Add to that the way they continually 'upgrade' their 
products, so that older versions cannot read files 
produced by the latest versions, and you can see the 
problem. But you probably know all this.

Unfortunately in it's current state PCB dosen't really 
compete. While it is useful for the 'odd' board for hobby 
and 'student' use, this is mainly (I think) cos it is free.

I would like to make a few suggestions under the 
following headings.

1. 'netlists' 

1.1 Component package data.

'Proffessional' netlist files usually contain details of the 
packages used in the design so that the layout tool can 
automatiacally load the corresponding component. This 
need not be particularily sophisticate, simply 
associating a 'footprint' name with a part reference would 
be sufficient. (At least initially)

It is often convenient to place more component detail in 
the netlist such as part names and values, so it would 
be nice to include this option in a specifiction for the 
netlist, even if it is not  supported at first.

This allows the circuit designer to specify packages at 
the schematic 'capture' stage of design.

I realise that this also requires the capture/schematic 
tool to produce such a file, but I think that this would 
happen if the option was there. 
I also realise that simulation tools such a spice tend to 
place device and connectivity data in separate files, and 
that may be a good approach for functional analysis 
allowing for libraries of sub-circuits to be constructed. 
But that is not an advantage to the circuit designer 
where the unit of re-use is the component package.

1.2 Net data.

It is not uncommon for such data as trace width, 
clerances and impedance also to be specified for 
individual at the schematic stage.  The same should 
apply here.


2. Design checking.

It should be possible to define design rules for each of 
the element types and layers. For example it should 
possible to turn off design checking for silk-screen 
layers. 

2.1 Global Clearances.

Global clearances should be specified seperately for the 
following type of feature.

Signal traces, Power traces, Surface mount pads, thru-
hole pads, Vias, Silk-screen to pad, board-edges,drills, 
copper pours.

These should be specified as clearances between type-
pairs. 

2.2 Individual net clearances

This is a more advanced feature. Clearances should be 
specifiable on a net-by-net basis, overriding global 
settings. This is useful for mixed technology and voltage 
designs. 

A lot of 'proffessional' software overlooks this. On more 
than one occasion I have been faced with a design with 
high voltage nets requiring clearances (and creepages!) 
of sevaral millimetres, on the same board as surface 
mount devices with pin pitches of 0.5mm. The package 
used did not support this feature, and it took several full 
working days to check the board clerances!

3. Board outlines.

Although many pcb's have a rectilinear outline, this is 
not always the case. Even when the are many are not in 
the form of a single rectangle. Cut-out areas are also 
often required.


In summary.....

The above represents a wish-list of the things I would 
like to see in a PCB layout program. The list is by no 
means exhaustive, there are 'look and feel' issues which 
probably need to be addressed, and such like, but I 
think that the above is enough to be going on with. 

Gordon Stalker