I am a circuit board designer, and would like to ask a few questions
to any board fabricators out there...

Question 1 (difficulty:easy)
Can someone briefly summarize the difference between B-Stage,
Laminate, Pre-preg, Core and Bonding Sheets (and any other commonly
used words related to board material)?  I keep getting confused

Question 2 (difficulty:challenging?)
As a circuit board designer using only FR4 and no impedance control,
how accurately should I specify material thicknesses?
I have seen fab dwgs that have the exact material type (some kind of
code) and thickness for every layer, and other dwgs specify only the
finished board thickness. Our drawings say "minimum dielectric
thickness .0035" but I'm not sure why. Do we have to declare a
minimum for some reason? Should I pay more attention to stackups than
I have in the past? Its seems to me that the vendors know what types
of material are available and can judge how to build a board based on
their experience, I haven't had any problems just noting the finished
thickness (that I know of, anyway), and I usually trust that they
know what they are doing (don't laugh).
OK, maybe I am leaving too much to chance, but can someone enlighten
me as to why a designer would call out EXACTLY what to use? Seems
pretty limiting and possibly needlessly expensive, and a rather
time-consuming study that I would rather not undertake unless there
is a reason for it.

Question 3 (difficulty:not sure)
I have read several messages discussing board warpage, and that a
primary reason for it is unbalanced construction. OK, I understand
that, but what if I have a design with three routing layers and one
ground plane? Should I try to offset warpage by calling out a thicker
material on one side or the other? Just curious if there are things I
can do to "counter-balance"...

Thanks in advance, 			                       Jack

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