Dale,
I have seen metal embedded in solder mask and on facility tour we found a
copper scrubbing process was the source and upon investigation there were
many cases where copper reduced spacing below minimums. I mounted samples
flat, potted and sectioned from the bottom up parallel to the board
surface. The result was very clear and no questions were raised by the
vendor. Boards were quickly replaced without question after the process was
changed to eliminate copper shavings embedded in the mask.

John

At 01:52 PM 12/10/2002 -0600, you wrote:
>Since IPC-A-600 doesn't have much to say about this...
>
>We recently started seeing quite a lot of metallic debris encapsulated in
>solder resist from several of our board suppliers. These bare boards are to
>be used as a class 3 SMT/PTH platform. There are few references to this in
>any standard I have read (including IPC-A-610, sect. 7.2), so I'd like some
>feedback on what everyone else is seeing these days and on what they
>believe the problem to be (or if they don't believe it to BE a problem).
>
>My take on it is that some board houses may be taking short cuts or saving
>money by not using fresh solder resist as often as needed, thus building up
>the amount of debris left over from each previous board that has been
>coated and leaving it on the following boards. Filtering the resist to
>remove this debris before using it again would be helpful, if workable. As
>the end user of this I find it bothersome (even though it IS encapsulated
>by the resist) as it indicates to me that the supplier may be trying to cut
>corners in the current economic climate.
>
>Okay, so is this a real problem or is it a "who cares" issue? On a board
>that is to be used as a class 3 platform, it seems to me that this IS an
>issue, especially in the rising incidents of debris seen in the resist.
>
>I have pictures of what I'm talking about. If you'd like to see them send
>email and will forward them to you for review. Thanks!
>
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