Patent Application
20140060882
The subject matter herein relates generally to a communication cable having at least one insulated conductor that is configured to electrically interconnect different electrical components.
For at least some types of communication cables, the communication cable includes at least one insulated conductor and a drain wire (also referred to as a grounding wire) that extend alongside each other for the length of the communication cable. The insulated conductor(s) and the drain wire may be surrounded by a shielding layer that, in turn, is surrounded by a cable jacket. The shielding layer includes a conductive foil that, along with the drain wire, functions to shield the insulated conductor(s) from electromagnetic interference (EMI) and generally improve performance. The communication cables may have a foil-in configuration, wherein the conductive foil faces radially inward, or a foil-out configuration, wherein the conductive foil faces radially outward. At the terminating ends of the communication cable, the cable jacket, the shielding layer, and the insulation that covers the conductor(s) may be removed (e.g., stripped) to expose the conductor(s). The drain wire and the exposed conductor(s) may then be mechanically and electrically coupled (e.g., soldered, crimped, welded, and the like, or coupled using an insulation displacement connector (IDC)) to corresponding elements of an electrical component, such as an electrical connector.
However, the above communication cable may have some undesirable qualities, particularly when the communication cable is used for high speed applications (e.g., greater than 10 Gbps). For example, when attempting to terminate the drain wire to the electrical connector assembly shell in a foil-in configuration, the conductive foil at the terminating end of the communication cable may be cut or torn in order to expose the drain wire to connect to it. The resulting seam in the foil may increase electromagnetic radiation emission/susceptibility at the terminating end. The resulting interruption in the conductive foil may also cause an unwanted change in impedance at the terminating end. In some cases, a foil-out configuration may avoid disturbing the foil shielding; however, this configuration may still have other drawbacks.
Each of the foil-in and foil-out cables may cause a “choke point” in which the ground path reduces from a 360 degree path surrounding the cable length to a small contact area at the drain wire connection, and then expands to the 360 degree path surrounding the connector assembly shielding shell. Each of the foil-in and foil-out cables may alter the impedance of the cable at tight bend areas where the drain wire may resist stretching and encroach on the signal conductors. Lastly, a drain wire may increase the cost of the cable and may also add complexity to the manufacturing process.
Accordingly, there is a need for a communication cable that provides effective EMI shielding at relatively low cost.
In one embodiment, a communication cable is provided that includes a cable jacket having a jacket end and a shielding layer having an electrically conductive exterior surface. The exterior surface extends along a length of the communication cable and interfaces with the cable jacket. The exterior surface has an exposed section that extends beyond the jacket end to a shielding end of the shielding layer. The communication cable also includes at least one insulated conductor that extends along the length of the communication cable and that is surrounded by the shielding layer and the cable jacket. The communication cable also includes an adhesive layer that surrounds the exposed section of the exterior surface. The adhesive layer is electrically conductive and is in intimate contact with the exterior surface.
In another embodiment, a communication cable is provided that includes a cable jacket having a jacket end and a shielding layer having an electrically conductive exterior surface. The exterior surface extends along a length of the communication cable and interfaces with the cable jacket. The exterior surface has an exposed section that extends beyond the jacket end to a shielding end of the shielding layer. The communication cable also includes at least one insulated conductor that extends along the length of the communication cable and that is surrounded by the shielding layer and the cable jacket. The communication cable does not include a drain wire that extends along the at least one insulated conductor. The shielding layer is configured to be electrically grounded at the exposed section.
In some embodiments, the communication cable may include a plurality of insulated conductors (e.g., one or more pairs). In particular embodiments, a pair of insulated conductors constitute a parallel pair of insulated conductors.
In yet another embodiment, an electrical connector assembly is provided that includes an electrical connector having signal conductors and a communication cable coupled to the electrical connector. The communication cable includes insulated conductors extending along a length of the communication cable. The insulated conductors are electrically coupled to corresponding signal conductors (e.g., contacts, terminals, and the like). The communication cable also includes a shielding layer that surrounds the insulated conductors and has an electrically conductive exterior surface that extends along the length of the cable. The communication cable also includes an adhesive layer that surrounds and is in intimate contact with the exterior surface of the shielding layer. The adhesive layer is electrically conductive. The connector assembly also includes a ground shield that is shaped to surround the adhesive layer. The ground shield electrically couples the exterior surface of the shielding layer to the electrical connector such that a grounding pathway exists through the ground shield.
In the illustrated embodiment, the communication cable 100 includes a pair of insulated conductors 112A, 112B. The insulated conductors 112A, 112B may extend parallel to each other along a length of the communication cable 100. As such, the cable configuration shown in
As shown, the communication cable 100 extends along a central or longitudinal axis 190, It is understood that the communication cable 100 is a flexible cable and, as such, the central axis 190 is not required to be linear for an entire length of the communication cable 100. The central axis 190 may extend through a geometric center of a cross-section of the communication cable 100. In the illustrated embodiment, the central axis 190 extends along a tangent line where the insulated conductors 112A, 112B interface or contact each other.
The communication cable 100 may include multiple layers that surround the central axis 190 and the insulated conductors 112A, 112B. For example, the communication cable 100 may include a shielding layer 105 that surrounds the insulated conductors 112A, 112B and a cable jacket 104 that surrounds the shielding layer 105 along an interface 106. In the illustrated embodiment, the shielding layer 105 immediately surrounds the insulated conductors 112A, 112B such that no other layers of material are located between the shielding layer 105 and the insulated conductors 112A, 112B. The shielding layer 105 may be tightly wrapped about the insulated conductors 112A, 112B such that the insulated conductors are unable to move relative to one another. For instance, the insulated conductors 112A, 112B are arranged side-by-side and each is configured to move or flex with the other. However, in alternative embodiments, the shielding layer 105 may be configured to permit some movement of the insulated conductors 112A, 112B relative to each other.
The cable jacket 104 interfaces with the shielding layer 105. In the illustrated embodiment, the cable jacket 104 immediately surrounds the shielding layer 105 such that no other layers of material are located between the cable jacket 104 and the shielding layer 105. The cable jacket 104 may be applied to the shielding layer 105 through a plastic extrusion process. The cable jacket 104 may also be applied to the shielding layer 105 through a spiral wrapping process. In alternative embodiments, additional layers of material may be located between the shielding layer 105 and the insulated conductors 112A, 112B or between the shielding layer 105 and the cable jacket 104.
The shielding layer 105 defines a core cavity 110 that includes the insulated conductors 112A, 112B. In some embodiments, the communication cable 100 does not include a drain wire (also referred to as a grounding or ground wire). In some known cables, a drain wire may extend parallel to the insulated conductors within a core cavity. However, the communication cable 100 shown in
Each of the insulated conductors 112A, 112B includes a wire conductor 130 and an insulation (dielectric) layer 132. The insulation layer 132 surrounds the corresponding wire conductor 130 and electrically separates the wire conductor from the wire conductor of the other insulated conductor. As shown in
As shown in the enlarged portion of
As the cable jacket 104 is removed, a jacket end 120 may be formed that is located a longitudinal distance or depth 115 from the shielding end 122 of the shielding layer 105. The jacket end 120 may include a jacket edge 124 indicating where a portion of the cable jacket 104 was removed. The jacket edge 124 may have different characteristics based on the removal process. For example, when the laser-ablation process described above is used to remove a portion of the cable jacket 104, the jacket edge 124 may have characteristics that are different than characteristics formed by mechanically stripping or chemical etching the portion of the cable jacket 104. As such, the jacket edge 124 may be characterized as a “laser-ablated jacket edge,” a “chemically-etched jacket edge,” or “mechanically-removed jacket edge” based on the removal process.
As shown in
During application of the adhesive layer 140, the first side 151 of the adhesive layer 140 may be applied to the exterior surface 118. For example, the first side 151 may be wrapped about the exterior surface 118 such that the first side 151 is also wrapped about the central axis 190. The first side 151 may be applied uniformly across the exterior surface 118 such that bubbles or pockets of air are reduced and the first side 151 is in intimate contact with exterior surface 118. In some embodiments, a tool or machine may be used to apply the adhesive layer 140. After application of the adhesive layer 140, the first and second seam edges 153, 154 may be located adjacent to each other and define a longitudinal seam 160 therebetween. However, in alternative embodiments, the seam edges 153, 154 of the adhesive layer 140 may overlap each other or, alternatively, may be separated from each other by a large gap.
In the illustrated embodiment, only a single adhesive layer 140 is applied to and wrapped continuously about the exterior surface 118. In alternative embodiments, the adhesive layer may include a plurality of sub-sections that are collectively wrapped about the exterior surface. For example, a total of four sub-sections may be applied to the exterior surface 118 in which each sub-section may cover about 25% of the exterior surface 118. In such embodiments, a plurality of longitudinal seams may exist. Furthermore, multiple adhesive layers may be stacked with respect to each other. For example, after the adhesive layer 140 is applied to the exterior surface 118, a second adhesive layer may be applied to the adhesive layer 140. In such an embodiment, each of the stacked adhesive layers may be considered a sub-layer of a composite adhesive layer.
The adhesive material of the adhesive layer 140 may include, by way of example only, an acrylic material, an epoxy material, a thermoset material, a thermoplastic material, or a combination thereof. The conductive particles may be dispersed evenly throughout the adhesive material or may have a designated pattern or pitch in the adhesive material such that the conductive particles are concentrated in separate regions. The conductive particles may include, by way of example only, nickel, gold, silver, copper, aluminum, or a combination thereof.
In some embodiments, the adhesive layer 140 is part of a transfer tape in which the second side 152 of the adhesive layer 140 has a release liner (not shown) that is removed after application of the transfer tape. For instance, the first side 151 of the adhesive layer 140 may be exposed to the ambient environment before the adhesive layer 140 is applied to the exterior surface 118 of the exposed section 126. The second side 152 may include a release liner. After the first side 151 is applied to the exterior surface 118, the release liner may then be removed to expose the second side 152 of the adhesive layer 140. Examples of such transfer tapes include the Electrically Conductive Adhesive Transfer Tape (ECATT) product line developed by 3M™. In other embodiments, the adhesive layer 140 is applied to the exterior surface 118 as a liquid or in an aerosol form. For example, the adhesive layer 140 may be painted, printed, dipped, or sprayed onto the exterior surface 118.
In some embodiments, the adhesive layer 140 circumferentially surrounds the exposed section 126 about the central axis 190. As used herein, the adhesive layer 140 circumferentially surrounds the exposed section 126 of the shielding layer 105 if more than half of the exterior surface 118 in a cross-section taken orthogonal to the central axis 190 is covered by the adhesive layer 140 (or multiple adhesive layers applied to the exterior surface 118). In particular embodiments, the adhesive layer 140 surrounds more than 75% of the exterior surface 118 in the cross-section or, more particularly, more than 90% in the cross-section. In some embodiments, the seam edges 153, 154 may contact each other or may be proximate to each other to form the longitudinal seam 160 between the seam edges 153, 154 as shown in
As shown, the ground shield 144 includes first and second sides 161, 162 having seam edges 163, 164 and ground edges 165, 166 (
A tool or machine may be used to apply the ground shield 144. For example, a crimping tool may be configured to shape and press the ground shield 144 against the adhesive layer 140. In particular embodiments, the adhesive layer 140 is a pressure-sensitive adhesive layer in which a curing process is activated by applying a designated amount of pressure or a radially-inward force against the adhesive layer 140. The pressure may be applied through the ground shield 144. By way of example only, the activating pressure of the adhesive layer 140 may be at least 15 psi or 1.0 kg/cm2.
However, in other embodiments, the curing process may include thermal activation of the adhesive layer 140. For example, the adhesive layer 140 may be heated to a designated temperature. The designated temperature may be less than a melting point of the other materials of the communication cable 100 (e.g., the insulation layers 132 or the cable jacket 104 (
Accordingly, the adhesive layer 140 may be in intimate contact with the exterior surface 118 (
During the lifetime operation of some conventional communication cables, the insulation of the communication cables may deform or change shape. In such embodiments where the conductive foil is supported or held between the dielectric insulation layer 132 and the ground shield 144, dielectric relaxation may negatively affect the electrical connection between the conductive foil and the ground shield 144. However, during the lifetime operation of the communication cable 100, the adhesive layer 140 may operate to maintain the mechanical and electrical connection between the ground shield 144 and the shielding layer 105. If insulating materials (or other materials) of the communication cable 104 change shape, the adhesive layer 140 may maintain the bond between the ground shield 144 and the shielding layer 105. In addition, the adhesive layer 140 may inhibit or impede oxidation along the interface between the ground shield 144 and the exterior surface 118.
As shown in
In some embodiments, the ground shield 144 operates as an intermediate shield. Another ground shield (not shown), such as a portion of an electrical connector (not shown), may be shaped to grip the ground shield 144. However, in alternative embodiments, the ground shield 144 may be part of the electrical connector. Such an embodiment is described below with respect to
The electrical connector 204 includes first and second housing shells 220, 221 that are configured to be coupled to each other and signal conductors 224, 226. The first and second housing shells 220, 221 may be mated together to define a contact-space therebetween where the signal conductors 224, 226 and the wire conductors 208, 210 are located. In the illustrated embodiment, the ground shield 212 and at least one of the first or second housing shells 220, 221 are configured to mechanically and electrically couple to one another. For example, either or both of the first and second housing shells 220, 221 may be shaped to surround and be deformed (e.g., crimped) to grip the ground shield 212. In such embodiments, the first and/or second housing shells 220, 221 may be referred to as a connector shield(s), and the ground shield 212 may be referred to as a ferrule or intermediate shield. Before, after, or during the coupling process, the wire conductors 208, 210 may be mechanically and electrically connected to the signal conductors 224, 226, respectively. In other embodiments, at least one of the first or second housing shells 220, 221 is welded to the ground shield 212.
The electrical connector 304 may be similar to the electrical connector 204 (
In the illustrated embodiment, the ground shield 322 may be similar to the ground shield 144 (
In alternative embodiments, the adhesive layer may be applied directly to an interior side of the ground shield 322. In such embodiments, the adhesive layer may engage the exposed section (not shown) of the shielding layer (not shown) as the ground shield 322 is coupled to the communication cable.
In embodiments such as those shown in
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” or “an embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional elements not having that property.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
