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August 2008

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Subject:
From:
Kevin Glidden <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Kevin Glidden <[log in to unmask]>
Date:
Mon, 18 Aug 2008 08:36:15 -0400
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Couple of things I would check......

Are you certain the PCB finish is tin lead?  Make sure what you received is
what you specified.

Could be dissimilar metals issue.  What is the module material and finish?

What materials are being used to clean before assembly?  Are they adequately
rinsed and dried prior to ESS?

What are the ESS parameters and is condensation occurring?



Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.

-----Original Message-----
From: Lum Wee Mei [mailto:[log in to unmask]] 
Sent: Saturday, August 16, 2008 1:23 AM
To: [log in to unmask]
Subject: [TN] Stain Mark after ESS

Hello,
 
Prior to assembly the PCBAs onto the modules, inspection has been done to
confirm there is no presence of stain around mounting holes for either
modules or PCBAs. However, after ESS when the PCBAs are removed from the
module to be conformal coated, black stain marks are noticed around the
mounting holes for modules and PCBAs. All PCBAs have a perimeter of tin-lead
plating to provide effective grounding between PCBA and module.
 
The mechanical group has ensure all modules are thoroughly cleaned before
the assembly. What would be the cause of the black stain and is there any
long-term reliability issue? The mech group has tried using Acetone to
removed the stain but without any success.
 
Looking forward to your reply and thanks in advance.  
 
Thanks and Regards,
~ Wee Mei ~

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