Steve, as always can't thank you enough. I have all that stuff and more and
confusion is now decreasing.
No one should assume anything about anything. I learned this long ago. I did
listen to our people talking about the "ceramic" packages in question and
their soldering problems. I just knew, as they are not component, design,
and manufacturing types so I had to investigate the issue more. Turns out,
like you say and does TI, these are plastic parts with aluminum slugs on
top. Still creates a problem for UNQUALIFIED assemblers that we used for so
long. Also, the problem may still be with the part supplier in question for
whatever reason yet to be discovered.
Withing the last few days, I have been investigating reality and discovered
what you did in minutes. Problem is, still not satisfied with the issues
concerning these parts. That will come.
Currently, I am having "good" boards, redesigned from last revision but
still not optimized (that will come in next/last revision. This means
solderability, laminate integrity, and hole wall cracking problems will end.
Therefore, no board continuity issues will be apparent, nor will our
problems with components "leaping" off boards, so we can concentrate
on soldering and solder joint issues.
Kerry supplied a "successful" profile for his 100 plus BGA board including
the ones we use. It works for him on a board more dense, in all ways, than
ours. As previously discussed, we will attempt duplicating something similar
for our comparitavely "little" boards, starting with supplier
recommendations (much like Kerry's) with the same devices. Should work fine
when real profiles determined.
One of the things that initially threw me off was TI's report on their
MicroStar BGA's. These little guys must be associated with the TMS3206000
with such critical design requirements concerning CTE mismatch. Also, if big
Joe is out there, these parts must be the Tessera variety he did so much to
make a reality. Joe, is this right?
These device types are the ones TI talks so much about reliability and the
CTE differential between Silicon's CTE (3.0) and FR4's 16-18. I don't think,
again, this concerns the TMS320C6203BGLS we are using. I will know more
Monday and invite TI DSP users to provide some more information as well.
Still, soldering and solder joint issues only will be resolved in a
qualified assembly capability.
Thanks for letting me think out loud and Werner, I never considered
seriously the Kevlar, CIC, or sockets for our little old commercial "hi-rel"
stuff, but thanks for setting me, and the rest of us, straight again and again.
Earl
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