The fact that this anomaly is on every piece in the same location would lead
you to believe it is something from the photo imaging process. Having said
this the other fact that it's getting progressively smaller says that its
not photo related. Ah, you have a cunundrum.

Is there any height or depth to this thing? Could it be some tin that was
not tin stripped after etching? This anomaly is on a solid piece of copper
so I would imagine its something to do with etch, resist strip, tin strip
process. I would also suggest that it is not a functional defect.

If you really have a need to see what it is I'd scrape of some mask and see
whats under it.

Good Luck,
Pete


>From: Wee Mei <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>,              Wee Mei
><[log in to unmask]>
>To: [log in to unmask]
>Subject: [TN] What is this solder mask defect?
>Date: Mon, 5 Dec 2005 08:58:23 +0800
>
>Steve,
>
>Hello,
>
>The suspect is completely flat and smooth to touch. An interesting
>observation is that though it appear at the same location for all the 10pcs
>of board, the size of the image tend to get smaller and smaller if the
>boards are arranged starting with the largest image. It can't be soda
>strawing as it is not on trace. It can't be pink ring as it is not around
>hole. What can it be? What is the likely cause?
>
>Will ask Steve to put it up. Kindly take a look. Your opinion is greatly
>appreciated.
>
>Regards,
>Wee Mei
>
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