Hi Ingemar! Good input! The LCC photo illustrates a worst case scenario and
there are many applications where LCCs are being successfully used. The
main issue is that many designers unknowingly or ignorantly just use an LCC
for a design without understanding the implications of having a ceramic
component on a laminate pwb in terms of CTE mismatch. The physics are
pretty straightforward - a large CTE mismatch results in solder joint
damage. Using a plastic component (instead of ceramic), utilizing a
controlled laminate material (as other TechNetee's have suggested), or
evaluating the use environment impact (-55C to +125C vs -20C to 80C) are
other mitigating factors in successfully implementing LCCs. Rockwell
Collins has a number of successful applications of LCCs but with the
multitude of plastic component availability have chosen to eliminate having
to deal with the CTE mismatch issues associated with the LCC component
style. I'll bet the number of times that Werner or Guenter have had to
explain the implications of large CTE mismatch and LCC components to
designers is larger than would be expected.

Dave



                      "Ingemar Hernefjord
                      (KC/EMW)"                     To:       [log in to unmask]
                      <ingemar.hernefjord@ER        cc:
                      ICSSON.COM>                   Subject:  [TN] LCC curiosa
                      Sent by: TechNet
                      <[log in to unmask]>


                      10/21/2004 04:59 AM
                      Please respond to
                      TechNet E-Mail Forum;
                      Please respond to
                      "Ingemar Hernefjord
                      (KC/EMW)"






Hi Steve! Wow, ya never would have thought a simple picture of a very beat
up LCC would be so interesting!

Dave


Hi Dave,
happened to get old article from APL on desk 'Reflow attachment and
reliability testing of ceramic chip carriers'.  And another from Bell Labs.
According to these, the packages were not so bad (at that time). Quoted:

'The general implications are that minor cracking occurs in the solder
joints during tempcycling, but to date no adverse effects have been
seen.....
...........from the study it appears that chip carriers provide a highly
reliable, easily testable, and easy to assemble packaging technique....'

'...the solder joints withstood 1,000 cycles -40/+130 Centigrades and aging
at as high as +175 Centigrades.........the failure rate at +80 C is
projected to be negligible for fifty years....'


Myself, was involved in development of a computer, whereas each board had
some 100 LLCCs, built on multiceramic and copper technology. Think I have
some pics still from that interesting time about 20 years ago...

Ingemar Hernefjord
Ericsson Microwave Systems

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