Heather,
What is happening is that the fiducial is isolated and is attracting
excessive plating. What the supplier is asking for is to add some
non-functional copper around the fiducial in order to balance the
plating. He requests a ring of copper, and we imagine it as a donut. In
essence, he probably means a large ring of copper for thieving, which
will probably work.
Gary Ferrari
FTG Circuits
Director, Technical Support
860-350-9300
Heather Gregg wrote:
> Some more information has come my way... (these things happen since I'm
> in the Netherlands and my employer is in Ohio)
> Apparently there is a dome of SN100 building up on the fid. Machine
> recognition is failing due to shadows and/or the fid appearing too
> small. If they crank the lighting level way down it will see most of the
> fids, but it's not consistent. The supplier has suggested a bull's eye
> pattern, not a doughnut (my bad, sorry). The supplier says the addition
> of a copper ring around the fid will solve the plating/leveling
> problems. To me it sounds like the supplier has processing problems so
> I'm reluctant to change our fid just for that. What's your opinion now?
>
> Thanks for all the responses so far. It's a great help.
> Hg
>
>
> Jack Olson wrote:
>
>> I don't think adjusting the clearance is going to solve her problem,
>> and that would be an expensive experiment (in time if nothing else)
>> for no gain. We use silver finish here, so I can't comment on that
>> except to say there has to be a bazillion boards with her finish
>> being built successfully, so I suspect the machine itself.
>>
>> just a guess, though
>> Jack
>>
>>
>> On 10/6/06, [log in to unmask] <[log in to unmask]> wrote:
>>
>>>
>>> Jack and Hg,
>>> I almost hate to disagree, but the equipment will likely work better if
>>> you
>>> use SMEMA standard fiducials.
>>> 1mm diameter copper with a minimum of 1mm clearance to anything
>>> all around.
>>> No copper, no mask, no nothing within 1mm of the fiducial dot.
>>> Unfortunately using Sn100 finish does not allow a shiny dot for the
>>> equipment to find, so you need the minimum clearance to help.
>>> If you can try a coupon with multiple variations of clearance .5mm, 1mm,
>>> 1.5mm, round, square, etc.
>>> I am relatively sure you will find the SMEMA standard of 1mm round with
>>> 1mm
>>> round clearance the best, but the finish may have more effect and there
>>> fore
>>> need something to help compensate.
>>> Good luck,
>>> FNK
>>>
>>>
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