Loan,
The first photos look like de-wetting. Usually caused by surface contamination and in this cause might be caused by incomplete solder stripping by the supplier. AS long as they accept paste and reflow they should be OK. The mask issue is caused by the via hole plugging process. What you see is heavier solder mask over the via's and less on the surface. Should not be a problem as long as the pluging material is fully cured and all solvents have been driven out of the via holes.
Regards
Scott B. Westheimer
5709 Clarks Fork Drive
Raleigh, NC 27616
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Home: (919)713-0748
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> Date: Fri, 19 Jun 2009 15:48:59 -0400
> From: [log in to unmask]
> Subject: [TN] PCB problems
> To: [log in to unmask]
>
> Dear Technos,
>
>
>
> I have a few questions regarding a funny lot of PCBs we've received. Steve was kind enough to post the pictures, see
>
>
>
> http://stevezeva.homestead.com/files/non_uniform_hasl.jpg <http://stevezeva.homestead.com/files/non_uniform_hasl.jpg>
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> http://stevezeva.homestead.com/files/non_uniform_hasl_1.jpg <http://stevezeva.homestead.com/files/non_uniform_hasl_1.jpg>
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> http://stevezeva.homestead.com/files/via_halo.jpg <http://stevezeva.homestead.com/files/via_halo.jpg>
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> http://stevezeva.homestead.com/files/via_halo_detail.jpg <http://stevezeva.homestead.com/files/via_halo_detail.jpg>
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>
>
> Out of the pack of 15 that I have inspected, most of them have some weird halos around all the vias, but no such issue around the component mounting holes. The pictures show the worst board, the rest have it to a lesser extent. What is it? Should this be a reject? Is this anything we should admonish our fab about?
>
>
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> Secondly, the SnPb HASL, is irregular on the pads, which is not out of the ordinary, but on some boards looks like in the pictures. I hesitate calling this de-wetting, since the wetting angles are good. Is it de-wetting? Should we reject the boards? I will paste the worst board I find and reflow it, to get an idea what happens during soldering, but I should also be able to help the incoming inspectors draw a line between good and bad in visual inspection of future lots...
>
>
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> Thank you,
>
>
>
> Ioan Tempea, ing.
>
> Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
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>
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>
> 30 ans déjà! - Already 30 years!
>
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