I forgot to answer another of your questions.
The standard you are looking for is SMEMA 3.1
and can be found here:

http://www.smema.org/smemastandards.htm

Also, I wasn't addressing the possibility that
SN100 is contributing to your problem. That
could be true and I wouldn't know how to deal
with it.
I was only discussing the proposed "doughnut"
solution, which sounds unwise to me.

good luck! Share your solution if you get one!


On 10/6/06, Jack Olson <[log in to unmask]> wrote:
>
> You are already using the best fiducial dimensions.
> Every SMT machine should be able to recognize it.
>
> but,
> A doughnut pattern will look no different than a plated
> through-hole,
> So...
> As an experiment, find the coordinates of a random
> through-hole and tell your operator (modify the data
> file if you need to) that coordinate is the new fiducial.
>
> I would bet a lunch that he can't "see" it any better.
>
> I'm always hesitant to change designs to non-standard
> just to solve a temporary problem (unless the product
> will be obsolete within the year?)
>
> best wishes,
> Jack
>
>
> On 10/6/06, Heather Gregg <[log in to unmask]> wrote:
> >
> > I'm being told that our Fuji CP-7 is having trouble reading the board
> > fiducials. The cause is said to be a build-up of too much SN100 plating
> > on the fid. We currently use a simple dot fid. The dot is 1mm in
> > diameter and it is made so that there is a 0.25mm ring of bare board
> > around it before you get to the solder mask. Our PCB supplier has
> > recommended going to a doughnut design, but our SMT department is
> > skeptical that this will solve the build-up of SN100 issue. Personally,
> > I'm not convinced that it is not a problem with the machine vision
> > system.
> >
> > That being said, I'm wondering what the "best" fid design would be. What
> >
> > are/ where can I find recommendations for fids? Does anyone else have
> > experience with this sort of problem? Should the fid be covered with
> > solder mask? What design is the most robust in regards to minimizing the
> >
> > effects that processing variables cause (such as plating build-up,
> > uneven plating, camera lighting bumped out of alignment, etc.)?
> >
> > Inquiring mind,
> > Hg
> >
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