With response to your first question, we should dialogue what is meant by
"fully cured". We monitor all of the Tg and Delta Tg for core laminates as
received from all of our suppliers ( including Polyclad). It is generally
accepted that a Delta Tg of < 5 degrees indicates "sufficient cure".
Typically we obtain values from Polyclad significantly lower than this.
Don't forget that we talking about chemical reactions based upon a myriad of
chemical, physical and thermal variations PLUS their interactions. It was
for the reason of the base varnish (aka A-stage) chemical composition
variation during blending of the various chemical components, that I asked
Robert Holmes whether the desired level of material stability could be
attained with today's supply base. Fact is NO ONE in the laminate industry
measures the base resin movement properties AS COATED on the glass during
impregnation.

The response to your second question is YES. Intuitively if we used exact
duplicate etch patterns on a core material of only 0.005 inch thick, versus
a core thickness of 0.050 inch thick, the distortion of each of the core
substrates would differ. The same could be argued for different base resin
systems. 

With regards to your last point, the theoretical model is simply a
mathematical model that estimates the base material movement based upon
empirical data. What other questions do you have?

D. Rooke
Circo Craft - Pointe Claire
([log in to unmask])

>Here are two questions that the Compunetics SPC group brought up today:
>
>(1)  Is inner layer core material completely cured when it comes from the 
>supplier?  One of our guys suggested Polyclad told him that it was not - 
>that was a surprise to us, if true.
>
>(2)  If materials differ in their effect on inner layer shifts, does that 
>mean you each material type should have its own film set to make the same 
>part?  
>
>Bob Holmes and Dave Rooke mentioned a few days ago a "theoretical model" 
>for film compensation.  How do I find out more about it?
>
>Thanks again for all help.   Lou Hart
>
>
>.
>
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