Mark,

Good study and good questions though I wrote a much better reply before but
it didn't take because of my ignorance in taking too much time the first
time. So, here goes again.


Mark: I'm learning about laminate materials and read with interest several
recent tecnet emails on the subject. I'd like to submit a question about a
particular construction that is a challenge with respect to registration.

Earl: Wish I simply copy what I wrote earlier. Registration, as all
specified requirements, suffers when bad design choices are made concerning
material selections and MLB constructions. You already know that.


Mark: The construction is all 2 core and 3 core. The prepregs are 1-106 and
1-1080, which I have learned are described as resin rich. The construction
is balanced with respect to copper weights, glass styles, core thicknesses,
and prepreg openings.

Earl: Unless selecting and using relatively exotic materials, you must stay
away from very thin core/preg materials for several reasons. If you're
serious about making your own capacitance cores you must consider foil
choices as not ED copper unless tooth faicing out. Of course, there is a
patent issues as well though I still don't know why. You will need to use
rolled copper unless as stated above with ED. Again, because the thin
core/pregs are so resin rich, you face dimensional issues both in the press
and in product significantly reducing yelds mostly because of
misregistration issues.


Mark: What I am observing with this part is variation in how much certain
cores shrink, lot to lot, and variation that I would describe as a shift or
possibly a rotation in some of the internal layers.

Earl: Don't know all what you mean by shrinkage but core variability should
not be an as received issue. It is when married with very thin, resin rich
stuff as you describe (106 and 1080). These glass styles are so juicy they
slip and slide in the press and books therein. I have images depicting
relamination dynamics and, if you wish, I'll ask Steve Gregory to post them.


There is so much more to this, but the general idea, unless pushing the
envelope like Steve, you should carefully consider your options as design
compromises faced every day by GOOD designers and fabricators.

I wanted to write more, and did before this, but time prohibits.

Best wishes,

Earl

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