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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