Hi Kyle
I agree with Jerry's reply.  For the most part we do not use local
fiducials - so leaving them off isn't usually an impact to us.  But talk
to whomever is going to be building these, they may have some reason to
have them.
And consider future requirements - Might the assembly move / increase
in quantity?  I'm building a board currently that was designed around
the requirements of a prototype shop.  They had a manual screen printer,
and a P&P that used tooling holes and had no fiducial recognition - so
they didn't ask for any fiducials at all.  Does this cause me
problems???  OH YAH.  I have to use &@#&*!'n through-holes as
fiducials.

regards,

Graham Collins
Process Engineer,
L-3 Communications Electronic Systems Inc.
Halifax
(902) 873-2000 ext 6215

>>> [log in to unmask] 09/13/06 10:04AM >>>
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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