Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-12-29
2001-08-07
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C439S065000
Reexamination Certificate
active
06271482
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to electrically conductive devices and, more particularly, to electrically conductive elastomers and methods for fabricating the same.
BACKGROUND OF THE INVENTION
The evolution of integrated circuits has been to decrease the package size of an integrated circuit while increasing the number of electrical leads for electrical interconnection between the integrated circuit and a circuit board on which it resides. As the number of electrical leads per integrated circuit has increased, the electrical leads have become smaller in size and more closely spaced, thereby increasing the difficulty in mounting an integrated circuit to a circuit board.
One method of overcoming this difficulty has been to replace the electrical leads, which are located around the perimeter of an integrated circuit package, with electrical contacts, which are located on the bottom surface of an integrated circuit package, thereby forming a leadless integrated circuit package. These electrical contacts typically have the shape of small protuberances or “balls” which are spaced in a grid array pattern. An integrated circuit package having these bottom surface electrical contacts is placed within a leadless integrated circuit socket or mounting device which retains the integrated circuit package. The mounting device has mating electrical contacts spaced in a grid array pattern which align with the electrical contacts on the integrated circuit package so as to provide electrical continuity between the integrated circuit package and a circuit board upon which the mounting device resides.
One problem that arises with leadless integrated circuit packages is that the electrical contacts of a leadless integrated circuit package and the mating electrical contacts of a mounting device become oxidized, which results in increased contact resistance and therefore decreased conduction between the electrical contacts of the integrated circuit package and the mating electrical contacts of the mounting device. The insertion force used to place a leadless integrated circuit package into a mounting device typically removes some of this oxide, thereby providing improved electrical contact. However, leadless integrated circuit packages are typically not inserted into a mounting device in a manner that is conducive to the removal of oxide on the electrical contacts, and since leadless integrated circuit packages are not directly soldered to the mounting device, the accumulation of oxide on the electrical contacts can result in poor electrical contact.
Another problem that arises with the use of leadless integrated circuit packages is that the electrical contacts of a mounting device are typically electrically connected to electrical leads which are soldered directly to a circuit board. The mounting device must therefore be desoldered if replacement or removal is required. As is commonly known in the industry, repeated soldering and desoldering typically degrades the quality of a circuit board, usually to the point where replacement is required. Thus, a solderless electrical connection scheme would be desirable.
In the fabrication of electronic or electrical devices and circuits, conductive paths and contact areas are usually provided by chemical etching and photolithographic techniques such as in the fabrication of printed circuit boards, and by plating techniques whereby one or more metal layers are provided on, for example, electrical contacts or contact areas of circuit boards, electrical devices, and the like. Such fabrication techniques are well known and are widely employed. They do, however, require a number of process steps and specialized fabrication equipment which adds to the cost and complexity of the manufacturing process and of the resultant products. Thus, the discovery of simpler fabrication techniques would be desirable.
SUMMARY OF THE INVENTION
The present invention contemplates several types of electrically conductive elastomers and methods for producing the same. In one embodiment, the present invention is realized as a layered composition comprising: a substrate having an outer surface, wherein the substrate is formed of a non-conductive elastic material; a first layer that is grafted to the outer surface of the substrate, wherein the first layer is formed with a non-conductive elastic material; and a second layer that is grafted to the outer surface of the first layer, wherein the second layer is formed with a non-conductive elastic material having a quantity of conductive flakes interspersed therein. The second layer can further be formed with a quantity of rounded or jagged conductive particles interspersed in the non-conductive elastic material such that some of the conductive particles are present along an outer surface of the second layer. Alternatively, a quantity of rounded or jagged conductive particles may be imbedded in an outer surface of the second layer.
In another embodiment, the present invention is realized as an elastic conductive interconnect element which has an elongated shape and is formed with a non-conductive elastic material having a quantity of conductive flakes and a quantity of conductive powder granules interspersed therein. The elastic conductive interconnect element can further be formed with a quantity of rounded or jagged conductive particles interspersed in the non-conductive elastic material such that some of the conductive particles are present along an outer surface of said elastic conductive interconnect element.
In still another embodiment, the present invention is realized as an electrical interconnect comprising a non-conductive substrate having respective opposite surfaces and a plurality of apertures formed therein extending between the respective opposite surfaces; and a corresponding plurality of elastic conductive interconnect elements located within the plurality of apertures, wherein each elastic conductive interconnect element extends between the respective opposite surfaces of the substrate, and wherein each elastic conductive interconnect element is formed with a non-conductive elastic material having a quantity of conductive flakes and a quantity of conductive powder granules interspersed therein.
The present invention includes the methods for fabricating the above-mentioned embodiments, which are themselves unique due to some novel manufacturing processes.
In view of the foregoing, it is quite apparent how the present invention overcomes the shortcomings of the above-mentioned prior art devices.
Accordingly, the primary object of the present invention is to provide electrically conductive elastomers and methods for fabricating the same.
The above primary object, as well as other objects, features, and advantages, of the present invention will become readily apparent from the following detailed description which is to be read in conjunction with the appended drawings.
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Crotzer David R.
DeDonato David A.
Goodwin Jonathan W.
Michaud Arthur G.
Norris Jeremy
Paladini Albert W.
Thomas & Betts International Inc.
Weingarten, Schurgin Gagnebin & Hayes LLP
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