Steve: It appears more like a case where the soldermask "broke", or split, allowing flux to get under the mask, and tarnish the Copper.
Rudy Sedlak
--- On Tue, 11/16/10, Steve Gregory <[log in to unmask]> wrote:
From: Steve Gregory <[log in to unmask]>
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, why?
To: [log in to unmask]
Date: Tuesday, November 16, 2010, 8:43 AM
Hi Charming,
I have your picture posted, it's here:
http://stevezeva.homestead.com/Pic1.JPG
Maybe they weren't cleaned well before solder masking?
Steve
From: Charming Chan [mailto:[log in to unmask]]
Sent: Tuesday, November 16, 2010 10:51 AM
To: [log in to unmask]
Subject: Radially discoloration on solder-resist covered via holes, why?
Hi Steve,
Would you help post the attached picture for me and forward this message to
TechNet? Thanks a lot.
The picture shows radially discoloration on solder-resist covered via holes,
while, the immersion silver pads without solder-paste reflowing have shiny
appearance with no discoloration. With naked eye checking, the discoloration
on solder-resist covered via holes is not corrosion product.
BTW, the pcb board surface finish is immersion silver, via holes are fully
pluged with solder resist, and no discoloration is observed after pcb
assembly finished. The discoloration possibly gets start in PCBA storaging.
Best Regarads
Charming Chan
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