Had a brief look in some of our company papers about the second guess. We 
observed a difference between plugged and unplugged vias. The former were 
discolored  like yours and it was caused by overtemperature (Leadfree!) 
which degraded the epoxy which bleeded out some stuff that discolerd the 
soldermask. What chemistry process, I don't remember.

Inge


----- Original Message ----- 
From: "Inge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 16, 2010 7:44 PM
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes, 
why?


> 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
>
>
>
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