Dave,
my judgement is based on two facts Steve had told me on his e-mail: dull
solder joints and the cause of OA flux left on the joints for too long... In
this case, the joint dullness is caused by Pb rish oxide on the surface..
You may want to verify your self using XPS.. You can put the dull joints
caused by longer exposure of OA flux into a THB (Bias is important) along
with some Sn-rich oxide passivated joint and observe the difference
yourself... Sorry, no published data .. I am agree with you that visual
appearance have not much to do with the reliability... You can make a joint
look beautiful by hand solder of poor solderability parts, but the excess
heat may generate brittle intermetallic layer and cause reliability
issues...Look can be deceiving (like we usually make mistake daily in our
live by "look" ;-)...but not in this case in my opinion,...based on my
limited experience...

By the way, I am glad Steve is working there... I think the place need him
badly to "straight out" few things... eventually, would lead to cost
cutting...Good luck Steve...may the God be with you...

best regards,
                                jk

At 06:15 AM 8/4/99 -0500, you wrote:
>
>
>Hi Joyce - You are going to have to give a better explanation of why you
>believe that a bright and shiny joint is a reflection (pun intended!) of
>good solder joint functionality before I become a believer! There is a very
>large body of data (Klein Wassink, Steen, Lea, Tench) that demonstrates the
>appearance of a solder joint is an extremely poor indicator of solder joint
>quality and reliability. Solder alloy, solder joint cooling rate, type of
>flux,  and the type of cleaning chemistry used in your assembly processes
>are just a few of the possible sources for making a solder joint dull in
>appearance. Pb oxide is less stable than Sn oxide - but the conversion of
>Pb oxide to Sn oxide is measured in minutes and not hours. You can use
>either SERA technology or Auger technology to watch the conversion in real
>time. The oxide states of solder joints play a minimal role in any
>electromigration issues on assemblies - the potential to form a battery and
>transport ions are the driving forces by several orders of magnitude in
>relation to solder joint oxide. I do agree with you on the process
>indicator aspects - if you were getting a shiny appearance and suddenly the
>solder joints become dull in appearance then something changed in the
>process which should be investigated.
>
>Dave Hillman
>Rockwell Collins
>[log in to unmask]
>
>
>
>
>joyce <[log in to unmask]> on 08/03/99 03:44:51 PM
>
>Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
>      to joyce <[log in to unmask]>
>
>To:   [log in to unmask]
>cc:
>Subject:  Re: [TN] Culture Changing...any ideas?
>
>
>
>
>Steve,
>Sorry, I have to agree with your QA for the dull solder joints... If you
>analyse the joint surface (XPS), it would be Pb rich oxide, which is
>unstable compare to the Sn rich oxide surface under RH condition.... The
>best cost saving you can do is to eliminate the idle time and get the
>assembly running as smooth as possible...(you are going to tell me to "go
>to
>hell", I know).  Based on my experience, the best products are produced
>with
>full running of assembly line with minimum idle time (nobody take extra
>long
>lunch or coffee break, therefore, not "happlily" forgot some steps...).  I
>AGREE with you that process indicator is not necessary required rework, but
>required investigation!(and documentation of why such an incidence
>occur...warning: not going to make you very popular).  If you find out that
>process is not optimized (can not minimize the idle time...for example),
>such an inherited process is not easy to fix...Usually, it is caused by
>rush
>(cost/time saving) of initial design of process (extreme case, no
>consideration of process flow at all)...In that case, you have a "career
>opportunity" on your hand...No easy fix in near future but work one station
>at the time and use your "Roberts University" output and ask for the God
>(who ever you think will listen) to help you too...by the way, if you have
>trouble for class 2, boy oh boy...(I think I should stoppppp....)
>                                  jk
>
>>One of the things that I've noticed since I've been here, is that there is
>>that everything is looked at through MIL-SPEC shaded glasses...and I've
>found
>>that boards we were building under IPC 610 class-II standards were being
>>touched-up un-neccessarily. Things that are maybe only a process
>indicator,
>>but acceptable, are being reworked. For one example, dull solder joints
>that
>>were caused because an active OA flux was left on longer than it should
>have
>>been before cleaning has made the joints look dull. QA won't accept the
>board
>>until all the solder joints are sparkling. I'll fix the problem about the
>>operators leaving the flux on too long before washing the board, but you
>>still don't need to touch every joint up! But I sure couldn't convince QA
>of
>>that...and so on it goes.
>>
>
>
>
>
>
>

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