I am working on the design of a PCB with rather large ceramic BGAs (47mm
  sq., 1284 pins) and one of my main concerns is stress in the balls as a
  result of the TCE mismatch between package and board. We plan on using
  FR4 but would consider other materials if the improved reliability is
  worth the cost. If anyone has experience with this and can give me any
  advice, or at least recommend some literature, I would greatly appreciate
  it. We have never done a design like this and are mostly worried about
  reliability. Thanks,
  Andy Buonviri ([log in to unmask])


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