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Subject:
From:
Charming Chan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Charming Chan <[log in to unmask]>
Date:
Wed, 17 Nov 2010 09:33:47 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (436 lines)
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



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