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OXYGENATED Ml3ALLIZATION SYSTEM FOR SUPERIOR ADHESION TO POLYETHERIMIDE (PEI)/GLASS COMPOSITES

IP.com Disclosure Number: IPCOM000007850D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-Apr-29
Document File: 3 page(s) / 133K

Publishing Venue

Motorola

Related People

Reggie Barnes: AUTHOR [+4]

Abstract

Metallization of three-dimensional (3D) molded polymer substrates by DC sputtering is an exciting alterna'tive to traditional electroless plating processes. This technology offers the ability to rapidly coat a three dimensional circuit base without the use of precious metal catalysts or plating baths that may be environmentally harmful. Thus, sputter coating offers high through-put and flexibility while mini- mizing disposable wastes.

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MOFOROLA Technical Developments

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OXYGENATED Ml3ALLIZATION SYSTEM FOR SUPERIOR ADHESION TO POLYETHERIMIDE (PEI)/GLASS COMPOSITES

by Reggie Barnes, John Halley, Kevin Arledge and Tom Swirbel

  Metallization of three-dimensional (3D) molded polymer substrates by DC sputtering is an exciting alterna'tive to traditional electroless plating processes. This technology offers the ability to rapidly coat a three dimensional circuit base without the use of precious metal catalysts or plating baths that may be environmentally harmful. Thus, sputter coating offers high through-put and flexibility while mini- mizing disposable wastes.

  Ultem is the trade name of a Polyetherimide (PEI)/glass composite material, produced by Gen- eral Electric, that is ideally suited to form discreet RF components and substrates due to its dielectric and loss tangent properties. Ultem is currently being used to mold helical coil resonators for various Radio products. These products typically require the Ultem material to be metallized to form a circuit pattern or RF shield for the intended application. At tem- peratures approaching the Tg of the Ultem material (around 185" C), poor metal adhesion is frequently evident with delamination, blistering, or peeling of the metal system from the Ultem substrate. These helicoils have been used extensively in Motorola's portable and mobile two-way radio products, but their use is accompanied by restrictions in the processing temperatures and methods that may be used in the solder assembly of the radio boards. This limitation reduces Ultem's potential use as a substrate media in traditional surface mount applications where the metal system may be exposed to temperatures greater than 220" C. Increased use of Ultem in surface mount applications will be dependent on the type metal system used, and its compatibility with the Ultem material. A reliable Ultem/metal system capable of multiple reflow and higher temperature processing is needed for the success of Ultem discreet compo- nents and substrates.

  In the standard metallization process the Ultem substrate material is wet-cleaned, baked, plasma cleaned, sputtered, and electroplated. During the sputtering process, the sputtering plant first performs

an RF sputter etch using argon. The parts are then automatically transferred, still under vacuum, to the sputter chamber where 6OOA of chrome and 2500.% of copper are deposited. The adhesive failure fre- quently seen in later processes is due to a separation between the chrome and the Ultem surface. This is tho...