[PCB_FORUM] Re: Design For Assembly (DFA) Audits

Just got back from vacation, so couldn't answer earlier... I've set up the DFA 
program for use here -but still rely on Valor for an interim and final check... 
We are running DFA with the way the Librarian set up the parts -I believe that 
the bounds encompass the area that the part could take up on the board -it 
allows for the part to be off center...He's not here, so can't ask him... I'm 
in the process of revamping the files to reflect our CM's valor names and 
spacings... Right now I have one .par that is minimum spacings only -I plan on 
having a couple of different version -min, okay, preferred (will always work)...
I'm only using the component to component check... I think I've used the 
testpoint check also with luck...

  There should be a new DFA release in 15.5 -so expect changes. It will have a 
spreadsheet and the format is changing -Here is some email I got about it:

"To best prepare for the DFA checker in 15.5, I would first set up DFA
rules in a spreadsheet similar to the attached screenshot that takes
into account spacing for S-S, E-E, and S-E. A new DFA placebound
subclass will be the reference point for the DFA check otherwise if not
found we will use the existing placebound geometry. The entry table will
support class to class checks so if you have several versions of an 0805
for example, you could assign the property dfa_dev_class to these
symbols. Hopefully we can provide the data entry utility in advance of
the release."
....

I've attached the screenshot of what it might look like... 
Lynn Isaacson, C.I.D.+
IPC Certified Advanced Interconnect Designer
Principal PCB Layout Technician
Medtronic Emergency Response Systems
Direct: 425-867-4443   Fax: 425-867-4462 
E-mail: lynn.isaacson@xxxxxxxxxxxxx



-----Original Message-----
From: Kevin McCowan [mailto:kmccowan@xxxxxxxxxxxxxx]
Sent: Thursday, August 26, 2004 1:13 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Design For Assembly (DFA) Audits


Steve,
I never saw an answer in all the mess that came through recently
so here goes.
In talking to our assembler he likes at least 20 mils between
parts so I make the place outline 10 mils outside the largest
piece on the component. For bgas I put a 100 mil no place around
it to allow for rework. This allows me to set my comp to comp
drc to 0.
I suggest you just look through the DFM guide that the assembler
seems to have sent and try to derive rules that you can live with.
It is always a good idea to please the assembler. They can give you
back a better product if you do!

Good luck to you,
Kevin McCowan
Sr. PCB Designer
TSI Telsys


Mariani, Stephen wrote:

> Is there anyone currently using the DFA tool? I would like to know if 
> you would share some information with me on how you define your library 
> components (placement boundary) and just how you exercise the tool 
> itself. I have a document Performing DFA Audits but it isn't the easiest 
> document to understand.
> 
> Thanks
> Steve
> 
> 
> Stephen Mariani
> Mercury Computer Systems, Inc.
> 199 Riverneck Road
> Chelmsford, MA 02194
> Phone: (978) 967-1855
> Fax: (978) 244-0520
> _mailto:smariani@xxxxxxx
> 
> 
> 

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