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December 1999

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Subject:
From:
Thomas Martin <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 15 Dec 1999 16:02:06 -0500
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Hi Davis,
       It is possible to do what you want but not easy. The pads
are used to build the parts and the parts are placed in the board
database. Unlike some CAD systems, Cadence is not, to my
knowledge, set up to allow different pads to occur automatically
in the part depending on which side of the board the part is placed
on; so you have 3 choices:

1&2) Define seperate library symbols for the same part to be used
on the top or bottom of the board.
      1)Depending on the schematic capture package and the
         version and level of Allegro you are using, I believe it is
         possible to include a  ALTERNATE PACKAGE in the
        schematic symbol and to choose between the two
        packages when placing the parts in Allegro ( I say,
       "I believe," because I've never  used this method,
        only read about it in the documentation.)
     2)Otherwise, after the initial parts placement,
       the schematic will have to be revised to use the bottom
        side PACKAGE for bottom (wave) side components and
        the top (reflow) side PACKAGE for the top side placed
       components and the new netlist read into the board before
       the parts appear. If the place side of a component
       is changed during the layout, this must be changed in the
       schematic and a new netlist read into the board.

3) IF the pad pitch (pad center to center spacing between pads)
      is the same on both  versions of the part, it  would also be
      possible to replace the  pads by the Reference Designator
     of the part, one part at a time,  a time consuming process and
      one with lots of opportunity for error.

 I suggest you have your PCB Designers, and/or that you yourself,
sign on to the Cadence pcb users group e-mail forum and ask this
question there. Some of the people on the forum may have a better
answer. It would be helpful if you could include the name and version
of  your schematic capture and Allegro packages in the question.
Details on the Cadence User Forums are available @:

http://www.dacafe.com/USERSGROUPS/Cadence/fact.html

Regards,

Tom

Thomas G. Martin
Sr. PCB Designer, ASE Technologies USA



Date:    Wed, 15 Dec 1999 17:12:20 +0800
From:    Davis Yang <[log in to unmask]>
Subject: Is it possible for Cadence to build 2 sets of pads library:one for
 reflow & another for wave soldering ?
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit



Hi, Technetter!
    Now our CAD engineers only build one set of pads library for reflow.
But the PCBA  often need to go thru reflow & wave soldering due to mix
technology. There are some soldering issues for reflow pads at wave
soldering. Then we require CAD engineers to build 2 sets of pads library
in Cadence: one for reflow and another for wave soldering. But the CAD
engineers said it is no use for they don't know whether the component is
at reflow side or wave soldering side when they select pads from pad
library.
How to solve the problem? Is any good solution or advice?
Thanks in advance!
Davis

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