Patrick, 

Your problem is very similar to the DoD depots where legacy electronics comes for repair.  Our group subcontracts to the Navy 2M (Miniature and Mircrominiature) repair operations.  2M has sponsored 30 additional test boards to the very large (200 board) NASA/DoD test program for all sorts of combinations of components, solders, board finishes and rework.  Our tests of repairing both SAC and eutectic solders with good old eutectic solder is that this is the "least bad" alternative, where exact solder joint composition cannot be determined. That is, just keep eutectic solder on the repair bench if you are exempt from RoHS.  This testing goes through harsh environment - -55 to +125 thermal cycle, vibration, drop shock, and combined vibe+thermal.   Final results of this "repair only with eutectic" will be presented at SMTAI this coming October. 

Denny Fritz






-----Original Message-----
From: Goodyear, Patrick <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Sun, May 1, 2011 2:11 am
Subject: [TN] Repair / Rework on non-in-house RoHS compliant boards


As a technician that does frequent board level repair rework some
uestions have come to mind.   While the majority of my work is legacy
.e. vintage (1968) we will face these concerns in the near future.  The
oards I primarly work on are Nuclear graded Class IE, (high
eliability, seismically qualified, etc.) high dollar boards, typically
n the 3-10g range and are not throw-aways, most have components that
re no longer manufactured. 
 am looking to the industry to find best practices, this is one of the
laces that was suggested for posting.   Any help you can give me would
e appreciated. 
With pre RoHS solders most if not all of major manufacturers used 63/37
olders and repair rework was easy, one just used 63/37. 
With the adoption of RoHS controls and the subsequent use of many
ifferent alloys of lead free solders, (at least 6 I know of), the
ollowing comes to mind:
. Are there compatibility issues mixing between the various alloys of
ead-free employed currently in electronics manufactures?   In strength
nd reliability primarly. 
. How does the technician determine the correct alloy of lead-free
older to use? 
3. How does the technician determine what alloy was originally used by
he manufacturer? 
4. Will IPC 7711A / 7721A standards be updated to delineate alloy
etermination and / or an alternate methods for the complete removal of
ead-free solders and subsequent repair using 63/37 or lead-free alloys?
at Goodyear 
ontrol Technician 
acific Gas and Electric Company 
iablo Canyon Nuclear Power Plant 
O Box 56 
vila Beach, CA. 93424 
05-545-4312 

_____________________________________________________________________
his email has been scanned by the MessageLabs Email Security System.
or more information please contact helpdesk at x2960 or [log in to unmask] 
_____________________________________________________________________
---------------------------------------------------
echnet Mail List provided as a service by IPC using LISTSERV 16.0
o unsubscribe, send a message to [log in to unmask] with following text in
he BODY (NOT the subject field): SIGNOFF Technet
o temporarily halt or (re-start) delivery of Technet send e-mail to 
[log in to unmask]: SET Technet NOMAIL or (MAIL)
o receive ONE mailing per day of all the posts: send e-mail to 
[log in to unmask]: SET Technet Digest
earch the archives of previous posts at: http://listserv.ipc.org/archives
or additional information, or contact Keach Sasamori at [log in to unmask] or 
47-615-7100 ext.2815
----------------------------------------------------


______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------