Bill,

I said in my intro that I made up the numbers just to show the point: that
the material CTE is
a lot higher above Tg compared to below Tg. My "numbers" are NTBTS (not to
be taken
seriously)... I didn't take the time to pull any specs ...

Sorry if I confuse that issue.

Rgds,
Valerie


Bill wrote:

I'm curious where you are getting your numbers from... as I have been
quoting IPC specs... I guess they may be slightly out of sync with your
information... the CTE or coefficient of Thermal Expansion numbers I used
came from page 127 of the CID+ study guide...

There is a chart there that I was getting the data from... but I did just
notice a note there, it's a reference that says "Z-axis expansion above Tg
can be as much as 4 times greater. For FR-4 it is 240-390 ppm. Contact
supplier for specific values of the other materials"



Bill Brooks - KG6VVP
PCB Design Engineer, C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
_______________________________________
Member of the San Diego Chapter of the IPC Designers Council
Communications Officer, Web Manager
http://dcchapters.ipc.org/SanDiego/
http://pcbwizards.com




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