Re: gEDA-user: naming and creation of 54-pin TSOP II (400 mil) footprint, request for help

[Jelle de Jong <jelledejong@xxxxxxxxxxxxx>]

Bert Timmerman wrote:
> Hi Jelle,
> 
> On Wed, 2009-05-13 at 14:45 +0200, Jelle de Jong wrote:
>> Hello everybody,
>>
>> I am trying to create a footprint with a correct name using the IPC-7351
>> Naming Convention for Standard SMT Land Patterns.
>>
>> But I am having some issues, i am using the below document to learn about
>> the naming convention:
>> https://secure.powercraft.nl/svn/openarm/trunk/working/pcb/documents/footprint-name-spec.pdf
>>
>> The footprint I want to make is a 54-pin TSOP II (400 mil), see:
>> https://secure.powercraft.nl/svn/openarm/trunk/doc/SDRAM/MT48LC16M16A2P-7E/256MSDRAM.pdf
>> # page 75, 54-Pin Plastic TSOP
>>
>> I tried to figure it out but I don't know what the lead span 1(L1) is?
>>
>> footprint:
>> TSSOP-65P-640L1-54N
>> 54-pin TSOP II (400 mil)
>> TSSOP   pin spacing, lead span 1, pin count
>> P  pin spacing        dimension
>> L1 lead span 1        dimension
>> N  pin count          count
>>
>> I also learned to create footprints with the following document:
>> https://secure.powercraft.nl/svn/openarm/trunk/working/pcb/documents/land_patterns_20070818.pdf
>> I had my ups and downs learning this and had some help trough IRC.
>>
>> However the creation of a 54-pin TSOP II seems to be able to automate
>> using a script.
>>
>> I looked at the following, but it uses a license I disagree with and I
>> can't figure out how it works, I prefer OSI and GPL compatible licenses.
>> http://www.luciani.org/geda/pcb/pcb-perl-library.html
>>
>> Would somebody be able to help me out, what should the name of the
>> footprint become and what scripts can I use to make the footprint and how
>> can I do this?
>>
> 
> I would go for a name like: "TSSOP80P1176X120-54N.fp" as in the IPC
> standard IPC-7351
> 
> 0.80 mm pitch,
> 11.76 mm lead span,
> X
> 1.20 mm height
> - 54 leads with Nominal pad conditions (as one of the following: Least,
> Nominal, Most).
> 
> Maybe it is a wise thing to avoid "-" characters in footprint file names
> or to have a "use-files" line in your gsch2pcb config file and pass a
> --skip-m4 flag to disable m4 macro generated footprints to goof up your
> pcb stuff.
> 
> Maybe include a vendor and part name too, while footprint artwork
> recommendations may vary across vendors and specific parts.
> 
Thanks Bert for the feedback, I am confused, I calculated the pitch on
0.65 mm how did you came to 0.80mm, and could you explain what exactly
the lead span is. If I look at page 75 of the datasheet how can I exactly
calculate this lead span?

Why did you include the height where did you find this requirement in the
IPC-7351 for TSSOP footprints?

And why should one avoid the "-" character in footprint names? I see a
lot of footprints with this character, would you be willing to discuss
the arguments?

I call the gsch2pcb with the following arguments:
gsch2pcb --use-files --skip-m4 ~/openarm/working/gschem/openarm-sbc.prj
--elements-dir ~/openarm/working/pcb/footprints/

I hope that is ok...

Sorry for al the questions, I am kind of confused, and searching for
answers and help.

Best regards,

Jelle de Jong


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