It is really bad to say that: I am glad you are not close by.
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----- Original Message -----
From: Goodyear, Patrick [mailto:[log in to unmask]]
Sent: Sunday, May 01, 2011 10:35 PM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Repair / Rework on non-in-house RoHS compliant boards
Thanks Steve, Yep got the test packs already. More what I am wondering
is compatibility of the different alloys of lead free, and how mixing
alloys can affect reliability of the joint both to heat and shock
(vibration).
I have repaired boards made with eutectic solders that have failed due
not to the solder bond but the physical failure of the solder over time
(30 years)due to vibration and thermal cycling. Had a group of cards
that were edge mounted in a large cabinet that the large encapsulated
capacitors literally fell off of, they were laying in the bottom of the
panel, and the equipment was still in service. Found during an
in-service inspection. Connections for mag-amps that the 8 through
board leads cracked and failed and the mag-amp body was physically
bolted to the board, failure of SCR's due to lead joints cracking with
the SCR bolted with heat-sinks to their boards, Elco bifucated pin edge
connectors that have their board connections crack from inserting and
removing the boards.
Pat Goodyear
-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Sunday, May 01, 2011 12:38 PM
To: Goodyear, Patrick; [log in to unmask]
Subject: Re: [TN] Repair / Rework on non-in-house RoHS compliant boards
Hi Patrick,
If you can't tell visually by the solder joint appearance, one way to
check if a solder joint contains lead is with swabs from Hybrivet
Systems:
http://leadcheck.com/sites/default/files/products/additional-info/leadch
eck-testing-photos.pdf
Steve
-----Original Message-----
From: Goodyear, Patrick
Sent: Sunday, May 01, 2011 2:11 AM
To: [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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