On Thu, 01 Feb 2007 23:13:51 +0100, Lez <
lez.briddon@...> wrote:
>
>> no, remember that's stuck to glass fibers.
> And that does not expand?
Sure does, but paper seems to expand or contract much more. Try it.
The expansion coefficient of copper is mostly irrelevant because the PCB
is much thicker and would just stretch it (i have not noticed any bending
of the boards, although single-sided PCB stock sometimes comes bent
regardless of temperature.
I do not know the expansion coefficient of paper, i think it depends very
much on the paper and also moisture. Wood ranges from somewhere in the
ballpark of FR4 to maybe 10 times as much, but i suspect it is even more
with paper. But the thing is, paper shrinks when you dry it, FR4 does not
;-)
Put a drop of water on paper and see the ripples from expansion (i should
know - stripped lots of wallpaper today).
ST