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Electromagnetic Shielding Plastic Enclosures for Logic Card Assemblies

IP.com Disclosure Number: IPCOM000104114D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Highum, EA: AUTHOR [+4]

Abstract

A need for electromagnetic shielding of logic cards has in the past required that a conductive metal be used for an enclosure. Plastics are an insulator and can not be considered because they would offer no shielding. A conductive loaded plastic alone could not be considered because many mechanical properties are sacrificed. By use of the coinjection plastic molding press, which utilizes Nickel Coated Graphite conductive fibers and an engineering plastic core material, plastic parts can now be used for electromagnetic shielding of logic cards and maintain the mechanical properties needed in the applications. This has now been applied to the book package used on the AS/400*.

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This is the abbreviated version, containing approximately 52% of the total text.

Electromagnetic Shielding Plastic Enclosures for Logic Card Assemblies

      A need for electromagnetic shielding of logic cards has in the
past required that a conductive metal be used for an enclosure.
Plastics are an insulator and can not be considered because they
would offer no shielding.  A conductive loaded plastic alone could
not be considered because many mechanical properties are sacrificed.
By use of the coinjection plastic molding press, which utilizes
Nickel Coated Graphite conductive fibers and an engineering plastic
core material, plastic parts can now be used for electromagnetic
shielding of logic cards and maintain the mechanical properties
needed in the applications.  This has now been applied to the book
package used on the AS/400*.

      The coinjection process for molding plastic parts allows a
plastic part to be injection molded with two materials.  The
materials are divided into the outer skin and the inner core.  This
combination allows the part to be molded with a conductive outer skin
loaded with Nickel Coated Graphite along with a core that provides
mechanical stability to the part.

      The Nickel Coated Graphite in the outer layer provides the
conductive ingredient to make the plastic enclosure act as a shield
around the logic card.  This is accomplished by making the outer skin
very conductive which provides an impedance mismatch with its
surroundings which reflects and absorbs electromagnetic waves as they
pass though this boundary.  By usi...