Robert,

Copper Invar Copper (CIC) is a Texas Industries "foil" product for
multi layer boards that was designed to give the resulting board a low
CTE (coefficient of thermal expansion).  The copper is metallurgically
roll bonded to both sides of a foil layer of Invar (a nickel iron
alloy that has very low CTE).  Invar also has low thermal conductivity
(much lower than copper).  Arlon (among others (not necessarily an
endorsement :)) makes a laminate core material using CIC.  Resulting
board CTE using CIC and polyimide are 9-12 ppm-C (compared to 16-18
ppm-C for standard polyimide GI(J,L,N) boards).  Talk to your board
vendors about processing concerns and cost.
--
Karl Sweitzer                     voice: 716.47.77546
Eastman Kodak Company             pager: 716.25.33681
800 Lee Road                        fax: 716.47.77293
Rochester, NY 14650-3118         mailto:[log in to unmask]

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