Component for use in forming printed circuit boards

Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement

Reexamination Certificate

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Details

C174S256000, C174S259000

Reexamination Certificate

active

06316733

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to printed circuits, and more particularly, to components used in the manufacturing of printed circuit boards and other articles.
BACKGROUND OF THE INVENTION
A basic component of a printed circuit board is a dielectric layer having a sheet of copper foil bonded thereto. Through a subtractive process, that includes one or more etching steps, portions of the copper foil are etched away to leave a distinct pattern of conductive lines and formed elements on the surface of the dielectric layer. Multi-layer printed circuit boards are formed by stacking and joining two or more of the aforementioned dielectric layers having printed circuits thereon.
The trend, in recent years, has been to reduce the size of electronic components and provide printed circuit boards having multi-chip modules, etc. This results in a need to increase the number of components, i.e., surface mount components, provided on a printed circuit board. A key to providing a densely populated circuit board is to produce close and fine circuit patterns from the copper. The width and spacing of conductive paths on the printed circuit board are generally dictated by the thickness of the copper on the dielectric layer.
It has been proposed to use copper-coated polyimide components in forming printed circuits. The thickness of the copper on polyimide is generally significantly less than the thickness of traditional copper foil sheet. The thinner copper on the polyimide allows for finer and more closely spaced circuit lines in that the thinness of the copper layer reduces the etching time required to remove unwanted copper. In this respect, it is possible to use copper clad polyimide wherein the copper has a thickness as low as 0.1 &mgr;m (1,000 Å). The thinner copper on the polyimide also finds advantageous application in a semi-additive process. In a semi-additive process, the copper is masked to define a circuit pattern, and copper is plated onto the exposed pattern to build up a circuit. The mask material is removed and a “flash etch” removes the base copper on the polyimide leaving the built-up circuit on the polyimide. Thus, copper on polyimide finds advantageous application in both subtractive and semi-additive processes for forming printed circuits.
The use of copper-coated polyimide components in forming printed circuit boards or multi-layer laminates requires good adhesion between the polyimide side of the component and the inner core laminate to which it is attached. However, it is generally known that polyimide itself has relatively poor adhesion properties.
The present invention overcomes this and other problems, and provides a copper-coated polyimide component having improved adhesion with the inner core laminate.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, there is provided a component for use in manufacturing printed circuits that in a finished printed circuit constitutes a functional element. The component is comprised of a film substrate formed of a first polymeric material having a first side and a second side. At least one layer of a tiecoat metal is applied to the first side of the film substrate. At least one layer of copper is deposited on the at least one layer of a tiecoat metal, the layer of copper having an essentially uncontaminated exposed surface facing away from the at least one layer of tiecoat metal. A plurality of spaced apart, discrete, adhesion promoting areas of a tiecoat metal are formed on the second side of the film substrate to define region(s) of exposed polymeric material on the second side of the film substrate.
It is an object of the present invention to provide a copper-coated polyimide component for use in forming printed circuit boards, multi-layer laminates and the like.
It is another object of the present invention to provide a copper-coated polyimide component as described above having improved adhesion to an inner core laminate.
It is another object of the present invention to provide a copper-coated polyimide component as described above having an adhesion promoting layer on the polyimide side of the component.
It is another object of the present invention to provide a copper-coated polyimide component as described above wherein the adhesion promoting layer is comprised of a plurality of spaced apart, discrete areas defining region(s) of exposed polyimide.
It is a still further object of the present invention to provide a copper-coated polyimide component as described above that would accommodate through holes.


REFERENCES:
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patent: 5541524 (1996-07-01), Tuckerman
patent: 6059952 (2000-05-01), Kang et al.
patent: 6118183 (2000-09-01), Umehara et al.
patent: 6157085 (2000-12-01), Terashima
patent: 6199273 (2000-03-01), Kubo et al.
patent: 6201305 (2001-03-01), Darveaux et al.
Metech, Inc. specification sheet entitled: METECH, Silver Conductor 2700, Revised Oct. 1999, 1 page.
Metech, Inc. specification sheet entitled: METECH, 8000 Series Resistor Compositions, Revised Nov. 1999, 1 page.
Information obtained from the web site: http://www.metechinc.com/solutions/clarostat.html,SOLUTIONSentitled: “Polymer Resistor Project Proves a ‘win-win-win’,” 4 pages, dated Jul. 20, 2000.
Information obtained from the web side: http://www.metechinc.com/solutions/manyapps.html,SOLUTIONSentitled: “Metech Resistor Pastes Serve Many Applications,” 2 pages, dated Jul. 20, 2000.

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