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December 2006

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Subject:
From:
Denis Morrissey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Denis Morrissey <[log in to unmask]>
Date:
Fri, 15 Dec 2006 08:46:57 -0500
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Another possibility is that the single panel was reworked through
immersion silver.  Immersion silver is notorious for etching copper as
it plates.  I've seen it lift narrow traces right off the substrate.
The voids probably just correspond to naturally low areas of copper
plating, whether from PTH or electrolytic copper.

Regards,
 
Denis Morrissey
Technical Applications Manager
Advanced Technology Division
Technic Inc.
Office:  516.349.0700 Ext 20
Cell:    401.595.7242
-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]] 
Sent: Thursday, December 14, 2006 4:21 PM
Subject: How does this happen?

Hi all!
 
Well, the day is just about done here and boy am I glad... 
 
We build a little board here (lots of them actually) that we call a
"leaf board" because of it's shape and small size. It has double-sided
SMT on a thin (.031"), immersion silver finished PCB. There are two PTH
hall-effect switches that we hand solder onto the board. We're using
standard 63/37 solder BTW...
 
One of my operators stopped me to tell me that she was having a hard
getting good fillets on some of the switches on one of the panels she
was working on (they come in a 18-up panel). So I look at it and then
tell her I see why she's having trouble. Take a look at this picture and
you'll see why she was having trouble too:
http://stevezeva.homestead.com/files/Lovely_Barrels.jpg
 
So I tell her to give me the panel so that I can scrap the whole thing.
We aren't about to ship our customers something like that. I
immeadiately start looking at other WIP on the floor to see if I can
find others that have the same problem. I haven't found any as yet. 
 
We emailed the photo to our fab vendor who immeadiately told us to ship
back all the bare boards that we have in our stockroom and they will
screen them for the problem. We've got a bunch in WIP right now that we
have to look closely at.
 
What actually causes something like that? The panel that we're working
with is only about 6" X 6", so I should expect that there's at least
another half dozen or so panels out there that might have this problem
depending on how big a panel the board house was building, right?
Further still, how does one panel get screwed-up like this and not the
others?
 
I'm ready to go home now...
 
-Steve Gregory- 

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