the discoloration is visible on top of the surface copper just right of R52 -- this suggests it is a surface condition of the mask or between the mask and the surface copper and not an internal condition Chuck Brummer <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 11/16/2010 01:14 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: [TN] Radially discoloration on solder-resist covered via holes, why? Charming, I think you need a micro section and it will reveal bad news. Rudy may be right or there may be an internal separation. Is this a multi layer? I once saw a set of boards on which they spend to much time in the glass etch and when copper plating the holes the copper wicked up the glass fibers. Chuck Brummer l 3M Manufacturing Engineer 3m Electronic Solutions Division--Flexible Circuits 8357 Canoga Ave. l Canoga Park, CA 91304-2605 (818) 734-4930 [log in to unmask] l www.3m.com l www.3mFlex.com From: Steve Gregory <[log in to unmask]> To: <[log in to unmask]> Date: 11/16/2010 08:48 AM Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, why? Sent by: TechNet <[log in to unmask]> 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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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