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Fabrication of high density multilayer interconnect printed circuit boards

  • US 6,255,039 B1
  • Filed: 04/03/1998
  • Issued: 07/03/2001
  • Est. Priority Date: 04/16/1997
  • Status: Expired due to Term
First Claim
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1. A process for producing a printed circuit board which comprises;

  • (a) attaching a photosensitive element onto a pattern of conductive lines on the surface of a substrate wherein there are spaces between the conductive lines;

    which photosensitive element comprises a negative working photosensitive dielectric composition on a surface of a conductive foil, such that the photosensitive dielectric composition is positioned on the conductive lines and in the spaces between the conductive lines;

    (b) applying a layer of a photoresist onto an opposite surface of said foil;

    (c) imagewise exposing the photoresist to actinic radiation and developing the photoresist to thereby form imagewise removed and imagewise nonremoved portions of the photoresist such that the imagewise removed portions are above at least one conductive line;

    (d) removing the portion of the conductive foil underlying the imagewise removed portions of the photoresist without removing the underlying photosensitive dielectric composition;

    (e) imagewise exposing a portion of the photosensitive dielectric composition to actinic radiation through the removed portions of the conductive foil;

    developing the photosensitive dielectric composition to thereby form imagewise removed and imagewise nonremoved portions of the photosensitive dielectric composition such that the imagewise removed portion form vias to the conductive lines;

    (f) curing the nonremoved portions of the photosensitive dielectric composition;

    (g) electrically connecting the conductive lines though the vias to a part of the conductive foil; and

    (h) patterning the conductive foil to thereby produce a pattern of conductive foil lines.

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