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December 1999

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Date:
Tue, 14 Dec 1999 18:48:57 -0500
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Hi, designers,
I am not a PWB layout guy...I did quick check for the foot print using IPC
on-line 782 calculator this afternoon, and got defeated in the attemp to do
a fast calculation...(stupid me!)
The part is Altera RQFP (square as SQFP but larger) with Jedec MO-143 style
of package and 240 gull wing leads.  The device outline is 36 mm-37 mm and
lead width is 11 mil, 20 mil pitch (sorry mixed SI with British units).  The
input for the on-line 782 calculator were:
(1) SQFP style
(2) Altera, RQFP
(3) 240 pin
the output of two table (with Altera, and RQFP)looks OK at first glance, but
the width of the pad is "X = 1.32", side filler "0.587" with outline of
package "35".... HAAAA! The outline did look close assume the unit is mm,
but how could I have a pad width of 1.32 mm in 20 mil pitch?  What I am
doing wrong?  I went to the Jedec site but no luck...
Help!  (I really think the on-line calculator is a wonderful idea, it must
be me with lack of "touch").
Many thanks in advance...
                                          jk

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