Jorge,

Seems like we're on the same page having never met. I have, since the
beginning, been involved with near CTE matching requirements for components
and boards.

In the late 70's through today, I have worked with 7-9 ppm boards using
constraining or tailoring core materials as well as Kevlar while meeting
initial quality and long term reliablity needs of ceramic at 5-7 ppm/C
requirements. That's all well and good.

Now, as exemplified by my recent posts, I'm again embroiled with the issue
concerning ceramic BGA's and "normal" boards with modified epoxy resin
systems. I go back and reference all the stuff from the past as well as try
to keep up with IBM's and TI's publications as well as kind individuals like
Per-Erik Tegehall who has done extensive reliability studies for the
European Space Agency.

I'm continuing with some options as:

1) socket or not here I come
2) constraining/tailoring core materials in MLB structures
3) go to "very precise" and recommended design rules for blind micro vias
and buried dog bones with blind interstitial vias using sequential lamination
4) punt.

This ain't easy stuff in a commercial/cheap environment. However, I try to
teach this ain't normal cheap. It's hi-rel cheap and it ain't cheap.

Mail me if you wish,

MoonMan

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