Ultralow-Dielectric-Constant foams by crystallisation from supercritical solution: Application to advanced electronic packaging


  • P. Ehrlich,

    1. State University of New York at Buffalo, Buffalo, NY 14260, U.S.A.
    Current affiliation:
    1. Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, U.S.A.
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  • D. J. Ehrlich

    1. Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA 02173, U.S.A.
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Accurate moulding of polymer foams of density 0.02–0.3 g cm−3 has been achieved by crystallising polyethylene and ethylene/methlacrylate copolymers from dry supercritical solutions. Adherent thick films can be sealed to electronic substrates and are proposed as insulating layers for interconnections on multichip modules and other high-speed electronic devices. The dielectric constant achieved for films of several-mil thickness is between 1.05 and 1.3 and can be tailored along with the physical properties of the film by adjusting the density and composition of the copolymer. Planarisation or complex patterning is possible by detailing the mould.