Vias open on both sides for ICT testing. Non-ICT vias get masked on both sides and plugged. -----Original Message----- From: Guy Ramsey <[log in to unmask]> To: [log in to unmask] Sent: Wed, Nov 17, 2010 10:15 pm Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, why? Are the vias open on the other side of the board? I see some masked and some pen vias . . . for test? s this done on the other side too? Masking one side of a via produces a eniscus of mask in the via that is nearly impossible to clean. ----Original Message----- rom: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory ent: Wednesday, November 17, 2010 8:26 AM o: [log in to unmask] ubject: Re: [TN] Radially discoloration on solder-resist covered via holes, hy? Hi Colin, The thing that confuses me, is that Charming said that the boards looked ine after assembly, and it was only after the boards had been stored a hile did they notice the dark areas around the vias. If it was thicker mask ver the vias you should have seen that from the beginning, right? Steve -----Original Message----- rom: TechNet [mailto:[log in to unmask]] On Behalf Of colin mcvean ent: Tuesday, November 16, 2010 7:15 PM o: [log in to unmask] ubject: Re: [TN] Radially discoloration on solder-resist covered via holes, hy? I agree with the plugged via scenario.... he possible reason for "discolouration" could be the fact that the plugging rocess is a seperate screening process, using a stencil screen with only ias open. Normal PSR is then applied over the top of semi-cured plugged ias, and process photomechanically. This would account for a thicker eposition at the via hol area, and also the darker contrast of colour. icrosection of the via hole would verify the situation.... y 2p worth --- On Tue, 16/11/10, Bob Landman <[log in to unmask]> wrote: rom: Bob Landman <[log in to unmask]> ubject: Re: [TN] Radially discoloration on solder-resist covered via holes, hy? o: [log in to unmask] ate: Tuesday, 16 November, 2010, 22:48 think you nailed it Inge. All the bad holes are plugged vias. The open ias are very tightly registered. Bob -----Original Message----- rom: TechNet [mailto:[log in to unmask]] On Behalf Of Inge ent: Tuesday, November 16, 2010 2:11 PM o: [log in to unmask] ubject: Re: [TN] Radially discoloration on solder-resist covered via holes, hy? Had a brief look in some of our company papers about the second guess. We bserved a difference between plugged and unplugged vias. The former were iscolored like yours and it was caused by overtemperature (Leadfree!) hich degraded the epoxy which bleeded out some stuff that discolerd the oldermask. What chemistry process, I don't remember. Inge ---- Original Message ----- rom: "Inge" <[log in to unmask]> o: <[log in to unmask]> ent: Tuesday, November 16, 2010 7:44 PM ubject: Re: [TN] Radially discoloration on solder-resist covered via holes, hy? It may be what we name 'via halo' effects,which is caused by stress. We do not accept. It may also be caused by contaminations and/or improper drying. / Inge ----- Original Message ----- From: "Victor Hernandez" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, November 16, 2010 7:22 PM Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, why? Is there a higher mag photo of this anomaly. I need to see it, to call it. "X" -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna Sent: Tuesday, November 16, 2010 12:20 PM To: [log in to unmask] Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, why? 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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