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Subject:
From:
Ian Hanna <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 16 Nov 2010 13:20:12 -0500
Content-Type:
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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
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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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