In a message dated 97-08-01 00:10:33 EDT, Mark Ploughman asked for
coefficients of thermal expansion (CTEs):

ANSWERS: below are orders of magnitude:

Polyimide materials: ~  60 ppm/C.
Polyimide based boards: x-y CTE ~ 15 to 18 ppm/C, z-CTE ~ 65 ppm/C
FR-4: x-y CTEs ~ 16 to 18 ppm/C. This is typical of in-plane CTEs for
double-sided boards, but measurements have given numbers in the range 12 to
21 ppm/C, depending on construction and board features (vias, solder filled
holes, amount of copper etc...). z-CTE: 60 to 85 ppm/C.
Copper: ~ 17. ppm/C

Jean-Paul
_______________________________________________________________
 Jean-Paul Clech
 EPSI Inc., P. O. Box 1522, Montclair, NJ 07042 - USA
 tel: +1 (973)746-3796  fax: + 1 (973)655-0815
 Home page:
<A HREF="http://members.aol.com/Epsiinc1/index.html">http://members.aol.com/Ep
siinc1/index.html</A>
(last updated on June 28, 1997).
SMT / BGA /CSP assembly reliability specialists.
 - click on the above or copy: http://members.aol.com/Epsiinc1/index.html
 __________________________________________________________________