I sent this to the wrong address - apologies.

What laminate are you using? I have some data on the Z-axis 
expansion of several common laminate material.  My company was 
recommended to go with the following speicfication for FR-4 on a Flight 
compatible piece of hardware:  Use HTE (ehich is class 3) copper foil 
for conductive layers, 1.5 micron PTH wall thickness of copper with 
12-30% elongation, 45k-55k PSI tensile strength.  Some also specify a 
Nickel coating on the PTH barrels after copper plating for strength 
although we were assured that this was not necessary.  This is a common 
specification in the aerospace industry where the product experiences 
large and frequent temperature cycles.  The above spec was developed 
for a new laminate material called Non-Woven Aramid.

Martin Kennett - Design Engineer, SED Systems Inc, Saskatoon, Canada.
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