Rich,

        It's my understanding from reading 782 (or reading how 782 was
created,
        I can't remember) that the formulas given were derived empirically
from
        the analysis of lots of different pad/lead ratios and the quality of
the solder
        joints that were created. In other words, the formulas are real-life
based, so
        there's no rule-of-thumb factors that need to be applied.
        On the other hand, if you have a SQFP (or any other part for that
matter)
         for which no recommded layout is given, then apply the formulas
given
        both at the beginning of 782 (for general information) and at the
back of
        each part-style section (for more specific information).
        As an alternate method, you can interpolate for values based on the
how
        close it may be to other styles. The best advice I can give you is
to read
        782 (and re-read it, if necessary) until you understand the formula
method.


>      Michael Hiteshew
>      Lockheed Martin Launching Systems
>      [log in to unmask]
     (410) 682-1259


> From:         Hamilton, Richard -4454[SMTP:[log in to unmask]]
>
> Hello Fellow TechNetters,
>
> I am curious about what anyone else uses for pad design, specifically on a
> square QFP. Is 782 sufficient?
> Is there a general rule of thumb factor to be used against 782?
> Or, is there another pad design formula to use?
>
> Thanks in advance for any input.
>
> Richard Hamilton
> Clemar Mfg. / Rain Bird
> [log in to unmask]
>

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