We've used this fid for many years without trouble, until we switched to
SN100 finish for ROHS. Does the SN100 behave so differently from the old
tin-lead that it would necessitate the extra thieving?
Hg
Gary Ferrari wrote:
> 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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