Patent Application
20160336692
The subject matter herein relates generally to electrical connectors that have signal conductors configured to convey data signals and ground conductors that control impedance and reduce crosstalk between the signal conductors.
Communication systems exist today that utilize electrical connectors to transmit data. For example, network systems, servers, data centers, and the like may use numerous electrical connectors to interconnect the various devices of the communication system. Many electrical connectors include signal conductors and ground conductors in which the signal conductors convey data signals and the ground conductors control impedance and reduce crosstalk between the signal conductors. In differential signaling applications, the signal conductors are arranged in signal pairs for carrying the data signals. Each signal pair may be separated from an adjacent signal pair by one or more ground conductors.
There has been a general demand to increase the density of signal conductors within the electrical connectors and/or increase the speeds at which data is transmitted through the electrical connectors. As data rates increase and/or distances between the signal conductors decrease, however, it becomes more challenging to maintain a baseline level of signal integrity. For example, in some cases, electrical energy that propagates on the surface of each ground conductor of the electrical connector may be reflected and resonate within cavities formed between ground conductors. Depending on the frequency of the data transmission, electrical noise may develop that increases return loss and/or crosstalk and reduces throughput of the electrical connector.
Accordingly, there is a need for electrical connectors that reduce the electrical noise caused by resonating conditions between ground conductors.
In an embodiment, an electrical connector is provided that includes a housing and a plurality of ground wafers and signal wafers. The housing has a mounting side and a front side. The front side is configured to mate with a mating connector. The ground wafers and signal wafers are stacked next to one another along a stack axis. The signal wafers are stacked in pairs and the ground wafers are interleaved between adjacent pairs of the signal wafers. Each signal wafer includes at least one signal conductor held by a signal holder that is composed of a first material. Each ground wafer includes at least one ground conductor held by a ground holder that is composed of second material. The second material is a lossy material and the first material is a low loss dielectric material that has a loss tangent that is lower than a loss tangent of the lossy material. The signal conductors and the ground conductors are configured to engage and electrically connect to the mating connector.
In an aspect, the low loss dielectric material of the signal holders has a loss tangent that is at least ten times lower than a loss tangent of the lossy material of the ground holders.
In another embodiment, an electrical connector is provided that includes a housing and a plurality of ground wafers and signal wafers. The housing has a mounting side and a front side. The front side is configured to mate with at least one mating connector. The ground wafers and signal wafers are stacked next to one another along a stack axis. The signal wafers are stacked in pairs and the ground wafers are interleaved between adjacent pairs of the signal wafers. Each signal wafer includes at least two signal conductors held by a signal holder that is composed of a low loss dielectric material. Each ground wafer includes at least two ground conductors held by a ground holder. A first portion of the ground holder of each ground wafer is composed of a lossy material and a second portion of the ground holder is composed of a low loss dielectric material. The low loss dielectric material of the signal holder and the low loss dielectric material of the second portion of the ground holder both have a respective loss tangent that is lower than a loss tangent of the lossy material of the first portion of the ground holder. The signal conductors and the ground conductors are each configured to engage and electrically connect to one mating connector.
In particular embodiments, the connector system 100 may be a backplane or midplane interconnection system such that the electrical connector 102 and the host circuit board 104 form a backplane or midplane assembly, and the mating connector 106 forms a daughter card assembly. The daughter card assembly may be referred to as a line card or a switch card. In the illustrated embodiment, only a single electrical connector 102 is shown mounted to the host circuit board 104, but in other embodiments the host circuit board 104 may include multiple electrical connectors mounted thereto. Although only one mating connector 106 is shown in
The connector system 100 may be used in various applications that utilize ground conductors for controlling impedance and reducing crosstalk between signal conductors. By way of example only, the connector system 100 may be used in telecom and computer applications, routers, servers, and supercomputers. One or more of the electrical connectors described herein may be similar to electrical connectors of the STRADA Whisper, Z-PACK TinMan, or the pluggable input/output (I/O) product lines developed by TE Connectivity. The electrical connectors may be capable of transmitting data signals at high speeds, such as 5 gigabits per second (Gb/s), 10 Gb/s, 20 Gb/s, 30 Gb/s, or more. In more particular embodiments, the electrical connectors may be capable of transmitting data signals at 40 Gb/s, 50 Gb/s, or more. The electrical connectors may include high-density arrays of signal conductors that engage corresponding contacts of a mating connector. A high-density array may have, for example, signal conductors on a 0.8 mm or less contact pitch along a front side of the electrical connector.
The electrical connector 102 includes a housing 108 that holds a plurality of signal wafers 148 (shown in
The mating interface 116 of the electrical connector 102 defines a port 118 or opening. The port 118 is open to a mating cavity 120 within the mating interface 116. A plurality of signal conductors 122 and ground conductors 124 of the signal wafers 148 (shown in
The front wall 114 of the housing 108 is joined to other walls to define a module cavity (not shown) that receives the signal wafers 148 (shown in
In an embodiment, the signal wafers 148 are stacked in pairs 154. Each pair 154 includes two signal wafers 148 that are adjacent to one another. As used herein, “adjacent signal wafers” means first and second signal wafers 148 that do not have any other signal wafers 148 or ground wafers 146 positioned between the first and second signal wafers 148. The ground wafers 146 in an embodiment are interleaved between adjacent pairs 154 of signal wafers 148. As used herein, “adjacent pairs of signal wafers” means first and second pairs 154 of signal wafers 148 that do not have any other signal wafers 148 positioned between the first and second pairs 154, although at least one ground wafer 146 may be disposed between the first and second pairs 154. In the illustrated embodiment, the ground wafers 146 and the signal wafers 148 are stacked in a repeating ground-signal-signal-ground-signal-signal sequence, such that each pair 154 of signal wafers 148 is bordered on both sides by a ground wafer 146. A single ground wafer 146 is disposed between adjacent pairs 154 of signal wafers 148 in the illustrated embodiment, but in other embodiments two or more ground wafers 146 may be disposed between two adjacent pairs 154 of signal wafers 148.
Each signal wafer 148 includes at least one signal conductor 156 held by a signal holder 158. The signal holder 158 is composed of a first material. The first material is a low loss dielectric material. The term “low loss dielectric material” as used herein is a relative term that means that the first material of the signal holder 158 has a loss tangent that is lower or less than a loss tangent of an electrically and/or magnetically lossy material, as described in more detail herein. Each signal holder 158 includes a left side 162 and an opposite right side 164. The left and right sides 162, 164 face the adjacent wafers 146 and/or 148 on either side of the respective signal wafer 148. At least one signal conductor 156 is held between the left side 162 and the right side 164 of the signal holder 158. Each signal wafer 148 in the illustrated embodiment includes two signal conductors 156 within the respective signal holder 158. But, in other embodiments, at least some signal holders 158 may hold only one or more than two signal conductors 156 (such as four as shown in
Each ground wafer 146 includes at least one ground conductor 166 held by a ground holder 168. The ground holder 168 is composed of a second material (as compared to the first material of the signal holders 158). The second material is an electrically and/or magnetically lossy material, referred to herein as “lossy material”. The lossy material has a loss tangent that is greater or higher than a loss tangent of the low loss dielectric material of the signal holders 158. Each ground holder 168 includes a left side 172 and an opposite right side 174. The left and right sides 172, 174 face the adjacent wafers 146 and/or 148 on either side of the respective ground wafer 146. In the illustrated embodiment, the left and right sides 172, 174 of each ground holder 168 of ground wafers 146 at intermediate locations within the wafer stack 144 each face signal wafers 148. Optionally, the ground holder 168 of each ground wafer 146 abuts the signal holder 158 of an adjacent signal wafer 148 along a seam 202. For example, the ground wafers 146 and signal wafers 148 of the wafer stack 144 may abut one another, defining seams 202 at the interfaces between the engaging holders 158, 168. The seams 202 may extend parallel to the longitudinal axis 191. At least one ground conductor 166 is held between the left side 172 and the right side 174 of the ground holder 168. Each ground wafer 146 in the illustrated embodiment includes two ground conductors 166, but at least some ground wafers 146 may include one or more than two conductors 166 in other embodiments. The ground conductors 166 in each ground wafer 146 align in a column that extends parallel to the wafer plane 152 of the ground wafer 146. In an embodiment, the ground holders 168 are overmolded onto the ground conductors 166 to form the ground wafers 146.
The signal conductors 156 and the ground conductors 166 are each configured to engage and electrically connect to the mating connector 106 (shown in
The signal conductors 156 and the ground conductors 166 each include a mating contact 182 that is configured to engage the mating connector 106 (shown in
In the illustrated embodiment, each wafer 146, 148 includes two mating contacts 182, and the two mating contacts 182 of each wafer 146, 148 align in a column along the elevation axis 192. Across the wafer stack 144, the mating contacts 182 of the plurality of wafers 146, 148 align in lateral rows 188 that extend parallel to the stack axis 150. In the illustrated embodiment, the wafer stack 144 includes two rows 188 of mating contacts 182. Both rows 188 of mating contacts 182 are configured to be received in the mating interface 116 (shown in
In an embodiment, the signal conductors 156 of each pair 154 of signal wafers 148 are arranged as differential signal pairs 194 that transmit differential signals. Each differential signal pair 194 is defined by one signal conductor 156 of a first signal wafer 148A of the pair 154 and one signal conductor 156 of a second signal wafer 148B of the pair 154. The signal conductors 156 of each differential signal pair 194 have adjacent mating contacts 182 that align in the same row 188 of mating contacts 182. For example, in the illustrated embodiment, each pair 154 of signal wafers 148 defines two differential signal pairs 194. Each of the two signal conductors 156 of each signal wafer 148 forms half of a different one of the two differential signal pairs 194.
The signal conductors 156 and the ground conductors 166 extend through the respective signal holders 158 and ground holders 168 between the mating contacts 182 and the mounting contacts 176. For example, the ground conductors 166 each include a mating segment 196, a terminating segment 198, and an intermediate segment 200 therebetween. The mating segment 196 includes the mating contact 182 and may extend into the ground holder 168 through the front edge surface 186. The terminating segment 198 includes the mounting contact 176 and may extend into the ground holder 168 through the mounting edge surface 180. The intermediate segment 200 links the mating segment 196 and the terminating segment 198. The intermediate segment 200 may be held completely within ground holder 168 (except possibly for protrusions or extensions that extend from the intermediate segment 200 for use in holding the ground conductors 166 within the ground holder 168, as shown in
During operation of the electrical connector 102, electrical energy (for example, current and voltage) may exist between the ground conductors 166. For example, as the electrical energy propagates through the signal conductors 156 between the corresponding mating contacts 182 and mounting contacts 176 of the signal conductors 156, the ground conductors 166 may support electrical energy that radiates from the signal conductors 156. The ground conductors 166 and the space between grounding elements of the host circuit board 104 (shown in
In an embodiment, the lossy material of the ground holders 168 of the ground wafers 146 is configured to impede the development of these standing waves (or resonating conditions) at certain frequencies and, consequently, reduce the unwanted effects of the electrical noise. For example, the lossy material of the ground holders 168 may absorb some of the electrical energy that propagates through the corresponding ground cavity along the at least one ground conductor 166 held by each ground holder 168. The lossy material may dissipate the absorbed electrical energy as heat. The lossy material in some embodiments may effectively change or dampen the reflections such that the standing wave (or the resonating condition) is not formed during operation of the electrical connector 102.
The lossy material of the ground holders 168 is able to conduct electrical energy, but with at least some loss. The “loss” as used herein refers to dielectric loss, which is a dielectric material's inherent dissipation of electromagnetic energy into, for example, heat. The lossy material is less conductive than the ground conductor(s) 166 held by the ground holder 168. For example, the signal and ground conductors 156, 166 may be stamped and formed from a copper alloy or other suitable metal that is capable of transmitting data signals at a commercially desirable data rate. The lossy material of the ground holders 168 is less conductive than the material that forms the signal and ground conductors 156, 166. The lossy material of the ground holders 168, on the other hand, is more conductive, and has greater dielectric loss, than the low loss dielectric material of the signal holders 158.
In an embodiment, the lossy material of the ground holders 168 includes conductive particles dispersed within a dielectric material. The conductive particles may be filler elements (or fillers) and the dielectric material may be a binder that is used to hold the conductive particles in place. As used herein, the term “binder” encompasses a material that encapsulates a filler or is impregnated with a filler. The conductive particles impart increased loss to the overall lossy material. For example, the lossy material of the ground holders 168 is more conductive, and has greater dielectric loss, than the low loss dielectric material of the signal holders 158.
The frequency range of interest may depend on the operating parameters of the connector system in which the electrical connector 102 is used. For example, the frequency range of interest, for some embodiments, may be between direct current (DC) and 50 GHz, but it should be understood that higher frequencies may be of interest in other embodiments. Some electrical connectors or connector systems may have frequency ranges that span only a limited portion of the above range, such as between DC and 20 GHz. In some embodiments, the electrical connector 102 may be configured for broadband data transmission. As used herein, the “electric loss tangent” is a ratio of an imaginary part to a real part of a complex electrical permittivity of the material of interest. Examples of electrically lossy materials that may be used are those that have an electric loss tangent between approximately 0.5 and 10.0 over the frequency range of interest. As used herein, the “magnetic loss tangent” is a ratio of an imaginary part to a real part of a complex magnetic permeability of the material of interest. Examples of magnetically lossy materials that may be used are those that have a magnetic loss tangent above 0.5 over the frequency range of interest.
The lossy material of the ground holders 168 may include material that is generally thought of as conductive, but is either a relatively poor conductor over the frequency range of interest, contains particles that are sufficiently dispersed in a dielectric such that the particles do not provide a high conductivity, or is otherwise prepared with properties that lead to a relatively weak bulk conductivity over the frequency range of interest. The lossy material may be partially conductive, such as having a bulk conductivity of between 5 Siemens per meter and 50 Siemens per meter.
As described above, the lossy material of the ground holders 168 may be formed by mixing a binder with a filler that includes conductive particles. The conductive particles used as fillers may include carbon and/or graphite formed as fibers, flakes, or other particles. Metal in the form of powder, flakes, fibers, or other conductive particles may be used as the filler in addition to, or as an alternative to, the carbon and/or graphite to provide suitable electrically lossy properties. Combinations of fillers may be used in some embodiments, such as metal plated (or coated) particles. Silver and nickel may be used to plate particles. Plated (or coated) particles may be used alone or in combination with other fillers, such as carbon flakes. The filler particles may be present in a sufficient volume percentage to allow conducting paths to be created from particle to particle. For example, when metal fibers are used, the fibers may be present in up to 40% by volume or more.
The binder material may be any material that will set, cure, or can otherwise be used to position the filler material. The binder may be a thermoplastic material, such as a liquid crystal polymer. The thermoplastic material may facilitate the molding of the lossy material into the desired shapes of the ground holders 168 as part of the manufacture of the electrical connector 102. However, many alternative forms of binder materials may be used. For example, epoxies, thermosetting resins, and/or adhesives may be used as binder materials.
The lossy material may be magnetically lossy and/or electrically lossy. For example, the lossy material may be formed of a binder material with magnetic particles dispersed therein to provide magnetic properties. The magnetic particles may be in the form of flakes, fibers, or the like. Materials such as magnesium ferrite, nickel ferrite, lithium ferrite, yttrium garnet and/or aluminum garnet may be used as magnetic particles. In some embodiments, the lossy material may simultaneously be an electrically-lossy material and a magnetically-lossy material. Such lossy materials may be formed, for example, by using magnetically-lossy filler particles that are partially conductive or by using a combination of magnetically-lossy and electrically-lossy filler particles.
As described above the low loss dielectric material of the signal holders 158 has a loss tangent that is lower than a loss tangent of the lossy material of the ground holders 168. The “loss tangent” refers to electric loss tangent. The loss tangent optionally may also refer to magnetic loss tangent. For example, the low loss dielectric material may have a loss tangent in the range of 0.001 to 0.1. More specifically, the loss tangent of the low loss dielectric material may be in the range of 0.005-0.01, such as 0.008 for example. The lossy material, on the other hand, may have a loss tangent that is higher or greater, such as in the range of 0.1 to 10.0. More specifically, the loss tangent of the lossy material may be in the range of 0.3-3.0, such as 0.5 for example. In an embodiment, the loss tangent of the low loss dielectric material is no more than one-tenth of the loss tangent of the lossy material (such that the loss tangent of the lossy material is at least ten times greater than the loss tangent of the low loss dielectric material). In some embodiments, the loss tangent of the low loss dielectric material may be closer to one-hundredth (for example, 0.01 versus 1.0) of the loss tangent of the lossy material. Thus, the lossy material of the ground holders 168 may absorb significantly more electrical energy than the low loss dielectric material of the signal holders 158.
As described below, in an alternative embodiment, at least some of the ground holders 168 may include both the lossy material and a low loss dielectric material, such that a first portion of the ground holder 168 is composed of the lossy material and a second portion is composed of the low loss dielectric material. The low loss dielectric material of these ground holders 168 may be the same material as the low loss dielectric material of the signal holders 158, or may be a different low loss dielectric material.
Referring to
Referring now to
Referring now to both
In the illustrated embodiment shown in
The ground conductors 166 each include the left and right broad sides 208, 216 and two edge sides 222. The edge sides 222 each extend between the left and right broad sides 208, 216. The edge sides 222 are narrower than the broad sides 208, 216. In an embodiment, the ground holder 168 of each ground wafer 146 engages both edge sides 222 along at least a majority of the length of the respective ground conductor 166 (as shown in the side views in
Like the ground holders 168, the signal holders 158 of the signal wafers 148 may define windows 224 along the left side 162 and the right side 164. The windows 224 may align with the signal conductors 156 such that each window 224 exposes at least a portion of one of the signal conductors 156 through the window 224. The sizes of the windows 224 may be selected or modified in order to tune the impedance of the electrical connector 102 (shown in
Similarly, the ground wafers 146 each include at least one ground conductor 166 with a mating contact 182 that extends from the front edge surface 186 into the upper port 118A and at least one ground conductor 166 with a mating contact 182 that extends into the lower port 118B. The at least one ground conductor 166 of each ground wafer 146 that extends from the mounting side 110 to the upper port 118A is referred to as a long ground conductor 266, and the at least one ground conductor 166 of each ground wafer 146 that extends from the mounting side 110 to the lower port 118B is referred to as a short ground conductor 366. In the illustrated embodiment, each ground wafer 146 includes four ground conductors 166 comprised of two long ground conductors 266 and two short ground conductors 366. The long ground conductors 266 are each longer than each of the short ground conductors 366.
In the illustrated embodiment, the ground holders 168 of the ground wafers 146 are composed of different materials along different portions of the ground holders 168. For example, a first portion 230 of the ground holder 168 is composed of the lossy material, and a second portion 232 of the ground holder 168 is composed of a low loss dielectric material. The low loss dielectric material of the second portion 232 may be the same or a different type of material than the low loss dielectric material of the signal holders 158. The low loss dielectric materials of the signal holders 158 and of the second portions 232 of the ground holders 168 both have a respective loss tangent that is lower than the loss tangent of the lossy material of the first portion 230 of the ground holders 168. For example, the low loss dielectric material of the signal holder 158 and the low loss dielectric material of the second portion 232 of the ground holders 168 may each have a loss tangent that is no more than one-tenth of the loss tangent of the lossy material of the first portion 230 of the ground holders 168.
Optionally, the lossy material of the first portion 230 of each ground holder 168 is not coated on the low loss dielectric layer of the second portion 232, or vice-versa. For example, the ground holders 168 each extend between the left side 172 and the right side 174. The left and right sides 172, 174 of the ground holder 168 along the first portion 230 are both defined by the lossy material, without any low loss dielectric material therebetween. Along the second portion 232, the left and right sides 172, 174 of the ground holder 168 are both defined by the low loss dielectric material, without any lossy material therebetween. In an embodiment, the ground wafers 146 may be formed by a two-shot overmold process in which the first portion 230 of the ground holders 168 is formed over the ground conductors 166 prior to the second portion 232, or vice versa.
In the illustrated embodiment, the intermediate segments 200 of the long ground conductors 266 extend through both the first portion 230 and the second portion 232 of the respective ground holder 168. The intermediate segments 200 of the short ground conductors 366, on the other hand, only extend through the first portion 230 of the respective ground holder 168. For example, as shown in
The low loss dielectric material of the second portion 232 is configured to engage the long ground conductors 266 to a greater degree or extent than the short ground conductors 366 due to the fact that the long ground conductors 266 are longer and therefore engage more lossy material between the front side 112 and the mounting side 110 than the short ground conductors 366. As such, the long ground conductors 266 would experience more electrical energy loss than the short ground conductors 366 if the entirety of the each ground holder 168 was formed of lossy material. By extending the long ground conductors 266 through the second portion 232 of low loss dielectric material, the electrical energy loss through the long ground conductors 266 may be reduced such that the long ground conductors 266 have loss characteristics more similar to the loss characteristics of the short ground conductors 366.
In alternative embodiments, the locations, sizes, and proportions of the first and second portions 230, 232 may be altered or tuned. For example, in one alternative embodiment, the ground holders 168 are formed of only the lossy material without a portion of low loss dielectric material. The thickness of the ground holders 168 along the long ground conductors 266 may be reduced relative to the thickness of the same ground holders 168 along the short ground conductors 366 in order to reduce the volume of lossy material that closely surrounds the long ground conductors 266, thereby reducing the electrical energy loss experienced by the long ground conductors 266 relative to the electrical energy loss experienced by the short ground conductors 366. In yet another alternative embodiment, the short ground conductors 366 may also be routed through both the lossy material of the first portion 230 and the low loss dielectric material of the second portion 232, but a greater length of the long ground conductors 266 may be routed through the low loss dielectric material than the length of the short ground conductors 366 that is routed through the low loss dielectric material.
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 various embodiments 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 patentable scope should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
As used in the description, the phrase “in an exemplary embodiment” and the like means that the described embodiment is just one example. The phrase is not intended to limit the inventive subject matter to that embodiment. Other embodiments of the inventive subject matter may not include the recited feature or structure. 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(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
