Amen to that. Xlinx is a good example of that.
There are recommended patterns for qfps that are smaller than the physical
part in some of their data books.

Neil D..


At 08:45 AM 7/30/98 -0700, Matthew Park wrote:
>Mark/Lisa,
>
>I think not, component manufacturers are good at making
>components and not so for recommending land patterns for their
>components.  They don't count in everything that goes on to
>solder a simple SMT comp from the begining to the end.
>
>When designing land patterns, Some of things you should
>consider:
>- component tolerance
>- board fabrication tolerance
>- pick/place accuracy
>- which end of component pin/lead the formation of solder fillet
>  ocurrs
>- amount of extra land area to set aside for robust solder fillet
>  formation and good wetting.
>
>By the time, all tolerances are added in, accuracy could be off as
>much as 0.2mm.  My recommendation is talk to your mfg
>engineer.  Professional SMT Component and Land Pattern Book
>by SMT Plus is a good place to start, however my preference is
>IPC-SM-782.  Look into the last page of each IPC land pattern
>section and the figure will explain tolerance and solder fillet req's
>
>regards
>Matthew Park
>SMT Manufacturing Engineer
>NII - Norsat International Inc.
>
>
>
>>>> Lisa Anderson <[log in to unmask]> July 30,
>1998  5:32 am >>>
>Mark,
>
>Try an inquiry to the manufacturer.  In most cases they have a
>suggested land pattern to use for the
>product on the specification sheet.
>
>Lisa Anderson
>Paradyne Corp
>Largo FL
>
>Mark Ross wrote:
>
>> We just bought the land pattern standard, IPC-SM-782 and
>found that many
>> of the components we are planning to design are not in here
>and appear
>> (?) to be unregistered.
>>
>> For instance SOT23-5 is not in the book.  Can anyone
>recommend a good
>> source for ALL or most land patterns.  A source that has a
>proven land
>> pattern track record?
>>
>> I do not want to use the IPC calculator and waste my time on
>many
>> patterns.  I would like a good resource for this information.  Or
>does
>> one not exist yet?
>>
>> Do I understand the process correctly that first a component
>must be
>> registered with JEDEC and then at some point somehow an
>IPC land pattern
>> for the component is established?
>>
>> We do not want to design surface mount products that fail
>because of
>> poor land pattern definition.  Thanks in advance.
>>
>> Mark Ross
>> Senior Design Engineer
>> Whistler Auto-Mation Products.
>>
>>
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