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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Guy Ramsey <[log in to unmask]>
Date:
Wed, 17 Nov 2010 09:15:04 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (434 lines)
Are the vias open on the other side of the board? I see some masked and some
open vias . . . for test?
Is this done on the other side too? Masking one side of a via produces a
meniscus of mask in the via that is nearly impossible to clean. 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Wednesday, November 17, 2010 8:26 AM
To: [log in to unmask]
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes,
why?

Hi Colin,

The thing that confuses me, is that Charming said that the boards looked
fine after assembly, and it was only after the boards had been stored a
while did they notice the dark areas around the vias. If it was thicker mask
over the vias you should have seen that from the beginning, right?

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of colin mcvean
Sent: Tuesday, November 16, 2010 7:15 PM
To: [log in to unmask]
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes,
why?

I agree with the plugged via scenario....
 
The possible reason for "discolouration" could be the fact that the plugging
process is a seperate screening process, using a stencil screen with only
vias open. Normal PSR is then applied over the top of semi-cured plugged
vias, and process photomechanically. This would account for a thicker
deposition at the via hol area, and also the darker contrast of colour.
Microsection of the via hole would verify the situation....
 
My 2p worth

--- On Tue, 16/11/10, Bob Landman <[log in to unmask]> wrote:


From: Bob Landman <[log in to unmask]>
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes,
why?
To: [log in to unmask]
Date: Tuesday, 16 November, 2010, 22:48


I think you nailed it Inge.  All the bad holes are plugged vias.  The open
vias are very tightly registered.

Bob 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Tuesday, November 16, 2010 2:11 PM
To: [log in to unmask]
Subject: Re: [TN] Radially discoloration on solder-resist covered via holes,
why?

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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