Hi Donald,

I saw the other responses and love the idea of not needing locals at all but I can't say how many assemblers are using this equipment. Assuming you have the room for local fid's - I recall doing a thing called a fiducial "patch" which simply meant using two diagonally opposed local fiducials to accommodate all of the fine pitch (at the time this meant .020" and under) within a 3 square inch area. Doing this will allow you to build the board anywhere. At any rate, the answer to your first question is yes. 

Rick

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Donald Kyle
Sent: Wednesday, September 13, 2006 9:05 AM
To: [log in to unmask]
Subject: [TN] Fiducials


Good morning

I have one of those It Depends questions regarding fiducials and
pick-n-place machines.

Per IPC-7351 and I'm sure other standards, a board at minimum should
have two fiducials on each end and each side.  Furthermore, if there
are fine pitch components there should be two fiducials for each fine
pitch component, sharing of fiducials is ok.

For assembly houses that place components at a billion a second I can
see the justification for the above requirements.

But lets say that your customer requires typically 5 to 10 boards per
run and those boards have fine pitch components.

It's not likely that they would be asking you to build them but maybe
you like to do prototypes and these quantities will fit somewhere in
your production area.

So my question to assembly houses is:

Can you live with fiducials placed every two inches across a board
such that any fine pitch component has two fiducials within two inches?

Is it possible to adjust the speed of pick-n-place machines to
accommodate for these parameters?

Thanks in advance


Donald Kyle C.I.D.+

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