I too, use a separate layer (I.E. not the Silkscreen layer) for the
Assembly Drawing information, as does William.
What I do is to also use that layer - the Assembly Layer - to depict
the actual outline of the part, and make it the exact size as called out
in the datasheet.
This way, I have a way to see how much real estate the actual part is
going to consume on the board, which will be different from the
silkscreen representation.
Just my .02 worth.
Regards,
James Jackson
Oztronics
On 2014-04-01 12:52, Brooks, William wrote:
> A point of detail... as Juan's comment prompted me to want to
> clarify...
>
> Most of us who have been designing for some years have used the
> silkscreen legend layer as the assembly drawing for expediency sake
> and have been successful doing that... however a true assembly drawing
> should do more than just tell you where the parts go on your board.
> The very normal silkscreen layer requirement for reference
> designators to be visible when the part is installed would make the
> assembly drawing have all the reference designators outside the part
> if that is what you used to make it... This is not always ideal.
>
> Some of us make a separate layer in our library parts for the
> assembly layer... this layer can have an accurate depiction of the
> part in the correct orientation and any polarizing features clearly
> identified... since the assembly layer does not get printed as the
> 'silkscreen legend', it can cover pads or whatever else is there in
> the CAD design since it is specifically for the assembly drawing only
> and not printed on the board surface. When plotting the assembly
> drawing we turn off the silkscreen layer and turn on the assembly
> layer so we get a true depiction of the part shown and can have the
> reference designators inside the part. :)
>
>
> William Brooks, CID+
> Senior MTS (Contract)
> 2747 Loker Ave West
> Carlsbad, CA 92010-6603
> 760-930-7212
> Fax: 760.918.8332
> Mobile: 760.216.0170
> E-mail: [log in to unmask]
>
>
>
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
> Robert Wolfe
> Sent: Tuesday, April 01, 2014 10:23 AM
> To: [log in to unmask]
> Subject: Re: [DC] Assembly standard + best practices
>
> Juan,
> Well you could look at IPC 2221 which has some info about that, or
> actually IPC spec IPC-D-325 will have more However if part body is big
> enough to fit large enough text for readability in the size document
> you are printing, Ref Des should be inside body of part for assembly
> dwg.
> Where parts are too small I usually put them as close as possible to
> where they are placed in silkscreen. Example SOT-23 This helps in
> inspection etc.
> Any silkscreen must be visible when part is installed though.
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
> Juan Vega
> Sent: Tuesday, April 01, 2014 12:38 PM
> To: [log in to unmask]
> Subject: [DC] Assembly standard + best practices
>
> Hello,
> Can someone help me pointing out which standard should I consult in
> order to do a Printed circuit board assembly drawing?
> I am trying to find, which is the best practice for location of
> reference designators (inside the part drawing, outside).
>
> Best regards!!
>
> Juan Vega | Product Enngineer | Branson Ultrasonics Emerson
> Industrial Automation | Lote #4 Carretera Nacional KM 8.5 Modulo
> Industrial America | Nuevo Laredo| Tamaulipas | 88277 | Mexico T + 011
> 52 867 711 0821 | F + 011 52 867 711 0811
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