Re: gEDA-user: PCB package creation guidelines

[Daniel Nilsson <daniel@oden.homeip.net>]

On Tue, Nov 16, 2004 at 05:14:01PM +0000, Karel Kulhavy wrote:
> Hello
> 
> I suggest that some PCB package creation guidelines were created:

Karel,

I'm not sure I completely understand the rules you have outlined
below, maybe you could elaborate a little ? Anyway, here are my comments:

> 1) The centroid of the package must be really the centroid

Why do you feel this is important ? This could be quite difficult to
ensure in some cases I think.

> 2) The middle of the silkscreen outline outlines the biggest outline that
>    can occur.

Sorry, don't understand what you are getting at.

> 3) The outline can go over pins and pads; it will be automatically masked
>    out

If you are taking about the outline as in the lines on the silk layer,
I agree.

> 4) Each pin or pad should have a name so that 'd' and pinout window display
>    something meaningful

Yes, as long as multiple pins can have the same name.

> 5) It's permitted to have a protrusion in the outline at pin 1, this protrusion
>    doesn't count for an outline.

Can you provide an example ?

> Could you comment on this? Would your guidelines be different?

In general, I think adding whatever rules of this kind should be done
as library checks in PCB and not only as documentation. Documentation
is obviously needed, but unless there is code that warns about any
violations the end-user can't be sure that guidelines were met.

> Would it be possible to add some description or something like that inside
> the packages which would describe for example what the package denotes?

That would be helpful, although there is quite a large description
field available today. I think the main problem is that this is not
integrated well with gschem for example, so finding what footprint
attribute to put into your schematics is for me the biggest problem.

Regarding the state of the PCB library, it seems to me that it is in
the need of a cleanup both for the structure and also to make sure
that the components that are in there actually have good footprints. I
did see the caution to use some of the old symbols in the
documentation, and it seems like I'm not the only one that are
modifying footprints because the ones in the library are not
correct. Would it be possible to try to organize some effort to clean
up the library to make sure that what's in there is good and easy to
find ?

-- 
Daniel Nilsson