What a way to start a new year! Les said it right as it should be interesting how everyone responds
to this loaded question.

I love CIC, but it's a bitch and or bastard (depending on political correctness) to work with. I
still love it, especially as a tailoring core as Les indicated, but the 10 mil stuff is my
favorite.

No one really suggested matching your stiffner on both sides. I mean, everyone agrees a balanced
construction is required. Of course, you probably don't have room on the top/bottom side for
another stiffner.

About Tg: Most all relatively conventional materials (again as everyone knows) has about the same Z
axis expansion rate at between 50-60 ppm/degree C. no matter Tg. You're currently using polyimide
so you can expect the same expansion - but it will go to a much higher temperature (250-270 Tg)
depending on the press cycle and cure, before it splodes - determined using DSC or TMA.

You could place the stiffner in the middle of the MLB no matter the material selected. Aluminum and
copper expand at relatively the same rate in the X-Y so make your choice as copper because you can
plate to it (easily) or through it and it can serve as a thermal transfer mechanism.

As always, and as everyone else, I have some pretty/ugly pictures you are welcome to view without
fear of disrupting family and friendly relationships. Also, constraint often is easier accomplished
than compliance during the fabrication process.

Earl Moon

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