Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
2000-06-22
2001-05-01
Patel, Tulsidas (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
Reexamination Certificate
active
06224394
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a tubular circuit connector or, more particularly, to a rubber-based tubular circuit connector used for electric connection of circuits, for example, between a liquid crystal display unit and a circuit board for driving the same, between two display units or between two circuit boards as well as to a unique method for the preparation thereof.
As is well known, a variety of modern electric and electronic instruments are manufactured by assembling a plurality of working units, e.g., liquid crystal display modules, and circuit boards to provide an electric circuit for driving the working unit. The electric connection between the electrode terminals of the working units and the circuit boards is established by using an electric circuit connector, referred to simply as a connector hereinafter. While various types of connectors are known and employed in the prior art, the most widely employed connector is a rubber-based connector of which the reliability of electric contacting between electrode terminals is ensured by utilizing the elastic resilience of a rubber-made member. For example, the so-called “zebra”-type rubber-based connector is an integral elongated body having a stratified structure consisting of a lengthwise alternate stratification of a multiplicity of layers of an electrically insulating rubber and a multiplicity of layers of an electroconductive rubber, which is a composite rubber compounded with an electroconductive powder such as a conductive carbon black and silver powder, to exhibit a black-and-white striped appearance.
It is usual in the above described “zebra” connectors that the composite rubber forming the conductive layers has a relatively high volume resistivity so that the connectors of this type are not quite satisfactory for electric connection between electrode terminals where a low electric resistance is essential as in the connection of color liquid crystal display modules and monochrome liquid crystal display modules of 18 or more gradations because of the possible variation in the performance of the liquid crystal display as being affected by the contact resistance unless the contact resistant is controlled to be negligibly small. The “zebra” connectors are also not suitable for electric connection when the electric current passing each of the conductive layers is large to exceed, for example, 10 mA as in the connection of plasma display modules because of the temperature elevation due to the heat generated therein as a consequence of the high resistance.
Furthermore, the rubber layers constituting the “zebra” connectors have a relatively high rubber hardness so that reliable electric connection can hardly be obtained between the electrode terminal and the conductive layer of the connector unless the contacting pressure therebetween is unduly increased to such an extent that the circuit board for connection is under a risk of warping or distortion by the large contacting pressure which may lead to a decrease in the stability of electric connection with the connector. This problem of course can be solved by increasing the thickness of the substrate board of the circuit board to withstand the large contacting pressure. This means, howqever, can not always be employed because an increased thickness of the circuit board requires on the other hand a decrease in the thickness of the working unit such as the liquid crystal display modules, for example, in mobile telephones which must be very compact in volume and light in weight. When the electroconductive rubber forming the conductive layers of the “zebra” connector is a composite rubber compounded with silver particles, in addition, the phenomenon of electromigration of silver atoms sometimes takes place between the electrodes to cause deposition of silver metal on the electrode surface resulting in a decrease in the reliability of electric connection through the connector.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide an improved rubber-based circuit connector free from the above described problems and disadvantages in the prior art rubber-based circuit connectors or, in particular, the “zebra” connectors and capable of electrically connecting oppositely positioned arrays of electrode terminals with relatively low resistance and with high reliability and stability.
Thus, the rubber-based circuit connector provided by the present invention is basically an integral tubular body consisting of an elongated tubular body of an electrically insulating rubber as a core tube and a multiplicity of electrically conductive ring-formed areas formed at a regular pitch on and around the core tube as arranged in the axial direction, the adjacent conductive ring-formed areas being insulated eacg from the other by intervention of a ring-formed insulating area.
In a first aspect of the invention, the inventive tubular circuit connector comprises:
(A) an elongated tubular body of an electrically insulating rubbery material as a core tube; and
(B) a multiplicity of ring-formed bilayered cladding layers arranged on and around the core tube at a regular pitch along the axial direction of the core tube, the adjacent ring-formed cladding layers being separated each from the other by a ring groove therebetween having a depth to reach the surface of the core tube to ensure a non-contacting condition between the ring-formed cladding layers,
in which each of the ring-formed bilayered cladding layers consists of:
a topmost layer as a contacting layer made from a highly electroconductive and oxidation-resistant metallic material such as gold; and
a base layer intervening between the surface of the core tube and the contacting layer to secure the contacting layer on the core tube, which is formed from a material having compatibility with the core tube and the contacting layer such as a synthetic resin or a metal other than gold.
In a second aspect of the invention, the insulation between adjacent two of the ring-formed contacting layers of an electroconductive material, e.g., gold, is ensured by, instead of a ring groove, a ringformed coating layer of a polysilane compound.
Though optional, it is advantageous that a pair of elongated reinforcement rubber strips are adhesively bonded to the cladding layers along the radially opposite axial lines so as to improve reliability in handling.
The above described rubber-based connector according to the first aspect of the invention can be prepared, for example, by a method which comprises the steps of:
(a) forming a coating layer, on and around the whole surface of an elongated core tube (A) of an electrically insulating rubbery material, from a material for the base layers of the bilayered cladding layer, such as a synthetic resin;
(b) forming a multiplicity of ring grooves of a constant width by partially removing away the coating layer at a regular pitch in such a depth that the surface of the core tube is exposed bare leaving ring-formed base layers; and
(c) forming a ring-formed plating layer of a highly electroconductive metallic material such as gold to serve as the contacting layer on the surface of the ring-formed base layer.
When the tubular body of a rubber subjected to the above described step (a) is a continuous-length rubber tube, the tubular body after step (c) is a head-to-tail continuum of a plurality of unit-length connectors so that the continuum after step (c) is divided by cutting apart into individual unit-length connectors.
REFERENCES:
patent: 5540594 (1996-07-01), Collins et al.
Dougherty & Troxell
Nasri Javaid
Patel Tulsidas
Shin-Etsu Polymer Co. Ltd.
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