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May 2011

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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Sun, 1 May 2011 06:54:41 -0400
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As repair for your board, stay with specified alloy, if it is 63-37, so be it.  You should also have spare in the same vintage for the program for the design life stored somewhere if the RFQ of the program were done properly.  Someone may lost track of it.  I wouldn't use LEADfree if I were you.  There are more lead in the reactor some places than just few droplets of solder.  My question is: WHY change?  As for the components supply, either some are stored in places you do not know, or the program need a re-design (re-spin) at sub system level.  As a repair, don't do it at this level!  
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----- Original Message -----
From: Goodyear, Patrick [mailto:[log in to unmask]]
Sent: Sunday, May 01, 2011 02:11 AM
To: [log in to unmask] <[log in to unmask]>
Subject: [TN] Repair / Rework on non-in-house RoHS compliant boards

As a technician that does frequent board level repair rework some
questions have come to mind.   While the majority of my work is legacy
i.e. vintage (1968) we will face these concerns in the near future.  The
boards I primarly work on are Nuclear graded Class IE, (high
reliability, seismically qualified, etc.) high dollar boards, typically
in the 3-10g range and are not throw-aways, most have components that
are no longer manufactured. 
I am looking to the industry to find best practices, this is one of the
places that was suggested for posting.   Any help you can give me would
be appreciated. 

With pre RoHS solders most if not all of major manufacturers used 63/37
solders and repair rework was easy, one just used 63/37. 

With the adoption of RoHS controls and the subsequent use of many
different alloys of lead free solders, (at least 6 I know of), the
following comes to mind:
1. Are there compatibility issues mixing between the various alloys of
lead-free employed currently in electronics manufactures?   In strength
and reliability primarly. 
2. How does the technician determine the correct alloy of lead-free
solder to use? 

3. How does the technician determine what alloy was originally used by
the manufacturer? 

4. Will IPC 7711A / 7721A standards be updated to delineate alloy
determination and / or an alternate methods for the complete removal of
lead-free solders and subsequent repair using 63/37 or lead-free alloys?
Pat Goodyear 
Control Technician 
Pacific Gas and Electric Company 
Diablo Canyon Nuclear Power Plant 
PO Box 56 
Avila Beach, CA. 93424 
805-545-4312 


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