# Patent

## Title
Electrical connector with complementary conductive elements

## Abstract

An electrical interconnection system with high speed, differential electrical connectors. The connectors are formed with columns of conductive elements, some of which carry signals some of which act as ground conductors. The conductive elements may contain projections to secure the conductive elements in a housing or to facilitate desirable current flow patterns. To avoid impedance discontinuities caused by the projections, adjacent conductive elements may be formed with complementary portions to provide a relatively uniform edge-to-edge spacing between signal and ground conductors along the length of the signal conductor. To manufacture such a connector in which both the signal and the ground conductive elements contain projections, the conductive elements carrying signals may be inserted into a housing from one side and the conductive elements acting as ground conductors may be inserted from an opposite side.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Application 60/921,696, filed Apr. 4, 2007 and incorporated herein by reference.


BACKGROUND OF INVENTION
1. Field of Invention
This invention relates generally to electrical interconnection systems and more specifically to improved signal integrity in interconnection systems, particularly in high speed electrical connectors.
2. Discussion of Related Art
Electrical connectors are used in many electronic systems. It is generally easier and more cost effective to manufacture a system on several printed circuit boards (“PCBs”) that are connected to one another by electrical connectors than to manufacture a system as a single assembly. A traditional arrangement for interconnecting several PCBs is to have one PCB serve as a backplane. Other PCBs, which are called daughter boards or daughter cards, are then connected through the backplane by electrical connectors.
Electronic systems have generally become smaller, faster and functionally more complex. These changes mean that the number of circuits in a given area of an electronic system, along with the frequencies at which the circuits operate, have increased significantly in recent years. Current systems pass more data between printed circuit boards and require electrical connectors that are electrically capable of handling more data at higher speeds than connectors of even a few years ago.
One of the difficulties in making a high density, high speed connector is that electrical conductors in the connector can be so close that there can be electrical interference between adjacent signal conductors. To reduce interference, and to otherwise provide desirable electrical properties, shield members are often placed between or around adjacent signal conductors. The shields prevent signals carried on one conductor from creating “crosstalk” on another conductor. The shield also impacts the impedance of each conductor, which can further contribute to desirable electrical properties.
Other techniques may be used to control the performance of a connector. Transmitting signals differentially can also reduce crosstalk. Differential signals are carried on a pair of conducting paths, called a “differential pair.” The voltage difference between the conductive paths represents the signal. In general, a differential pair is designed with preferential coupling between the conducting paths of the pair. For example, the two conducting paths of a differential pair may be arranged to run closer to each other than to adjacent signal paths in the connector. No shielding is desired between the conducting paths of the pair, but shielding may be used between differential pairs. Electrical connectors can be designed for differential signals as well as for single-ended signals.
Examples of differential electrical connectors are shown in U.S. Pat. No. 6,293,827, U.S. Pat. No. 6,503,103, U.S. Pat. No. 6,776,659, and U.S. Pat. No. 7,163,421, all of which are assigned to the assignee of the present application and are hereby incorporated by reference in their entireties.
SUMMARY OF INVENTION
Signal integrity in an electrical connector may be improved by forming adjacent conductive elements with complimentary shapes. Conductive elements containing projections are positioned adjacent conductive elements with relieved portions. Such a configuration of conductive elements contributes to a more uniform conductor to conductor spacing, which may impart conductive elements carrying signals with desirable electrical properties.
In some embodiments, the complimentary portions are formed in the regions of the conductive elements containing barbs or other features that engage a housing into which the conductive elements are inserted. To facilitate assembly of connectors with conductive elements containing complimentary sections, conductive elements may be inserted into the housing from two sides, with conductive elements having projections inserted from one side and conductive elements complimentary relieved portions inserted from an opposite side of the housing.



BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
FIG. 1 is a perspective view of an electrical interconnection system according to an embodiment of the present invention;
FIGS. 2A and 2B are views of a first and second side of a wafer forming a portion of the electrical connector of FIG. 1;
FIG. 2C is a cross-sectional representation of the wafer illustrated in FIG. 2B taken along the line 2C-2C;
FIG. 3 is a cross-sectional representation of a plurality of wafers stacked together according to an embodiment of the present invention;
FIG. 4A is a plan view of a lead frame used in the manufacture of a connector according to an embodiment of the invention;
FIG. 4B is an enlarged detail view of the area encircled by arrow 4B-4B in FIG. 4A;
FIG. 5A is a cross-sectional representation of a backplane connector according to an embodiment of the present invention;
FIG. 5B is a cross-sectional representation of the backplane connector illustrated in FIG. 5A taken along the line 5B-5B;
FIGS. 6A-6C are enlarged detail views of conductors used in the manufacture of a backplane connector according to an embodiment of the present invention;
FIG. 7A is a cross-section of a portion of a connector with complimentary conductive elements; and
FIG. 7B illustrates a process of manufacturing a connector with complimentary conductive elements.



DETAILED DESCRIPTION
This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” or “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Referring to FIG. 1, an electrical interconnection system 100 with two connectors is shown. The electrical interconnection system 100 includes a daughter card connector 120 and a backplane connector 150.
Daughter card connector 120 is designed to mate with backplane connector 150, creating electronically conducting paths between backplane 160 and daughter card 140. Though not expressly shown, interconnection system 100 may interconnect multiple daughter cards having similar daughter card connectors that mate to similar backplane connections on backplane 160. Accordingly, the number and type of subassemblies connected through an interconnection system is not a limitation on the invention.
FIG. 1 shows an interconnection system using a right-angle, backplane connector. It should be appreciated that in other embodiments, the electrical interconnection system 100 may include other types and combinations of connectors, as the invention may be broadly applied in many types of electrical connectors, such as right angle connectors, mezzanine connectors, card edge connectors and chip sockets.
Backplane connector 150 and daughter connector 120 each contains conductive elements. The conductive elements of daughter card connector 120 are coupled to traces, of which trace 142 is numbered, ground planes or other conductive elements within daughter card 140. The traces carry electrical signals and the ground planes provide reference levels for components on daughter card 140. Ground planes may have voltages that are at earth ground or positive or negative with respect to earth ground, as any voltage level may act as a reference level.
Similarly, conductive elements in backplane connector 150 are coupled to traces, of which trace 162 is numbered, ground planes or other conductive elements within backplane 160. When daughter card connector 120 and backplane connector 150 mate, conductive elements in the two connectors mate to complete electrically conductive paths between the conductive elements within backplane 160 and daughter card 140.
Backplane connector 150 includes a backplane shroud 158 and a plurality conductive elements (see FIGS. 6A-6C). The conductive elements of backplane connector 150 extend through floor 514 of the backplane shroud 158 with portions both above and below floor 514. Here, the portions of the conductive elements that extend above floor 514 form mating contacts, shown collectively as mating contact portions 154, which are adapted to mate to corresponding conductive elements of daughter card connector 120. In the illustrated embodiment, mating contacts 154 are in the form of blades, although other suitable contact configurations may be employed, as the present invention is not limited in this regard.
Tail portions, shown collectively as contact tails 156, of the conductive elements extend below the shroud floor 514 and are adapted to be attached to backplane 160. Here, the tail portions are in the form of a press fit, “eye of the needle” compliant sections that fit within via holes, shown collectively as via holes 164, on backplane 160. However, other configurations are also suitable, such as surface mount elements, spring contacts, solderable pins, etc., as the present invention is not limited in this regard.
In the embodiment illustrated, backplane shroud 158 is molded from a dielectric material such as plastic or nylon. Examples of suitable materials are liquid crystal polymer (LCP), polyphenyline sulfide (PPS), high temperature nylon or polypropylene (PPO). Other suitable materials may be employed, as the present invention is not limited in this regard. All of these are suitable for use as binder materials in manufacturing connectors according to the invention. One or more fillers may be included in some or all of the binder material used to form backplane shroud 158 to control the electrical or mechanical properties of backplane shroud 150. For example, thermoplastic PPS filled to 30% by volume with glass fiber may be used to form shroud 158.
In the embodiment illustrated, backplane connector 150 is manufactured by molding backplane shroud 158 with openings to receive conductive elements. The conductive elements may be shaped with barbs or other retention features that hold the conductive elements in place when inserted in the opening of backplane shroud 158.
As shown in FIG. 1 and FIG. 5A, the backplane shroud 158 further includes side walls 512 that extend along the length of opposing sides of the backplane shroud 158. The side walls 512 include grooves 172, which run vertically along an inner surface of the side walls 512. Grooves 172 serve to guide front housing 130 of daughter card connector 120 via mating projections 132 into the appropriate position in shroud 158.
Daughter card connector 120 includes a plurality of wafers 1221 . . . 1226 coupled together, with each of the plurality of wafers 1221 . . . 1226 having a housing 260 (see FIGS. 2A-2C) and a column of conductive elements. In the illustrated embodiment, each column has a plurality of signal conductors 420 (see FIG. 4A) and a plurality of ground conductors 430 (see FIG. 4A). The ground conductors may be employed within each wafer 1221 . . . 1226 to minimize crosstalk between signal conductors or to otherwise control the electrical properties of the connector.
Wafers 1221 . . . 1226 may be formed by molding housing 260 around conductive elements that form signal and ground conductors. As with shroud 158 of backplane connector 150, housing 260 may be formed of any suitable material and may include portions that have conductive filler or are otherwise made lossy.
In the illustrated embodiment, daughter card connector 120 is a right angle connector and has conductive elements that traverse a right angle. As a result, opposing ends of the conductive elements extend from perpendicular edges of the wafers 1221 . . . 1226.
Each conductive element of wafers 1221 . . . 1226 has at least one contact tail, shown collectively as contact tails 126 that can be connected to daughter card 140. Each conductive element in daughter card connector 120 also has a mating contact portion, shown collectively as mating contacts 124, which can be connected to a corresponding conductive element in backplane connector 150. Each conductive element also has an intermediate portion between the mating contact portion and the contact tail, which may be enclosed by or embedded within a wafer housing 260 (see FIG. 2).
The contact tails 126 electrically connect the conductive elements within daughter card and connector 120 to conductive elements, such as traces 142 in daughter card 140. In the embodiment illustrated, contact tails 126 are press fit “eye of the needle” contacts that make an electrical connection through via holes in daughter card 140. However, any suitable attachment mechanism may be used instead of or in addition to via holes and press fit contact tails.
In the illustrated embodiment, each of the mating contacts 124 has a dual beam structure configured to mate to a corresponding mating contact 154 of backplane connector 150. The conductive elements acting as signal conductors may be grouped in pairs, separated by ground conductors in a configuration suitable for use as a differential electrical connector. However, embodiments are possible for single-ended use in which the conductive elements are evenly spaced without designated ground conductors separating signal conductors or with a ground conductor between each signal conductor.
In the embodiments illustrated, some conductive elements are designated as forming a differential pair of conductors and some conductive elements are designated as ground conductors. These designations refer to the intended use of the conductive elements in an interconnection system as they would be understood by one of skill in the art. For example, though other uses of the conductive elements may be possible, differential pairs may be identified based on preferential coupling between the conductive elements that make up the pair. Electrical characteristics of the pair, such as its impedance, that make it suitable for carrying a differential signal may provide an alternative or additional method of identifying a differential pair. As another example, in a connector with differential pairs, ground conductors may be identified by their positioning relative to the differential pairs. In other instances, ground conductors may be identified by their shape or electrical characteristics. For example, ground conductors may be relatively wide to provide low inductance, which is desirable for providing a stable reference potential, but provides an impedance that is undesirable for carrying a high speed signal.
For exemplary purposes only, daughter card connector 120 is illustrated with six wafers 1221 . . . 1226, with each wafer having a plurality of pairs of signal conductors and adjacent ground conductors. As pictured, each of the wafers 1221 . . . 1226 includes one column of conductive elements. However, the present invention is not limited in this regard, as the number of wafers and the number of signal conductors and ground conductors in each wafer may be varied as desired.
As shown, each wafer 1221 . . . 1226 is inserted into front housing 130 such that mating contacts 124 are inserted into and held within openings in front housing 130. The openings in front housing 130 are positioned so as to allow mating contacts 154 of the backplane connector 150 to enter the openings in front housing 130 and allow electrical connection with mating contacts 124 when daughter card connector 120 is mated to backplane connector 150.
Daughter card connector 120 may include a support member instead of or in addition to front housing 130 to hold wafers 1221 . . . 1226. In the pictured embodiment, stiffener 128 supports the plurality of wafers 1221 . . . 1226. Stiffener 128 is, in the embodiment illustrated, a stamped metal member. Though, stiffener 128 may be formed from any suitable material. Stiffener 128 may be stamped with slots, holes, grooves or other features that can engage a wafer.
Each wafer 1221 . . . 1226 may include attachment features 242, 244 (see FIGS. 2A-2B) that engage stiffener 128 to locate each wafer 122 with respect to another and further to prevent rotation of the wafer 122. Of course, the present invention is not limited in this regard, and no stiffener need be employed. Further, although the stiffener is shown attached to an upper and side portion of the plurality of wafers, the present invention is not limited in this respect, as other suitable locations may be employed.
FIGS. 2A-2B illustrate opposing side views of an exemplary wafer 220A. Wafer 220A may be formed in whole or in part by injection molding of material to form housing 260 around a wafer strip assembly such as 410A or 410B (FIG. 4). In the pictured embodiment, wafer 220A is formed with a two shot molding operation, allowing housing 260 to be formed of two types of material having different material properties. Insulative portion 240 is formed in a first shot and lossy portion 250 is formed in a second shot. However, any suitable number and types of material may be used in housing 260. In one embodiment, the housing 260 is formed around a column of conductive elements by injection molding plastic.
In some embodiments, housing 260 may be provided with openings, such as windows or slots 2641 . . . 2646, and holes, of which hole 262 is numbered, adjacent the signal conductors 420. These openings may serve multiple purposes, including to: (i) ensure during an injection molding process that the conductive elements are properly positioned, and (ii) facilitate insertion of materials that have different electrical properties, if so desired.
To obtain the desired performance characteristics, one embodiment of the present invention may employ regions of different dielectric constant selectively located adjacent signal conductors 3101B, 3102B . . . 3104B of a wafer. For example, in the embodiment illustrated in FIGS. 2A-2C, the housing 260 includes slots 2641 . . . 2646 in housing 260 that position air adjacent signal conductors 3101B, 3102B . . . 3104B.
The ability to place air, or other material that has a dielectric constant lower than the dielectric constant of material used to form other portions of housing 260, in close proximity to one half of a differential pair provides a mechanism to de-skew a differential pair of signal conductors. The time it takes an electrical signal to propagate from one end of the signal connector to the other end is known as the propagation delay. In some embodiments, it is desirable that each signal within a pair have the same propagation delay, which is commonly referred to as having zero skew within the pair. The propagation delay within a conductor is influenced by the dielectric constant of material near the conductor, where a lower dielectric constant means a lower propagation delay. The dielectric constant is also sometimes referred to as the relative permittivity. A vacuum has the lowest possible dielectric constant with a value of 1. Air has a similarly low dielectric constant, whereas dielectric materials, such as LCP, have higher dielectric constants. For example, LCP has a dielectric constant of between about 2.5 and about 4.5.
Each signal conductor of the signal pair may have a different physical length, particularly in a right-angle connector. According to one aspect of the invention, to equalize the propagation delay in the signal conductors of a differential pair even though they have physically different lengths, the relative proportion of materials of different dielectric constants around the conductors may be adjusted. In some embodiments, more air is positioned in close proximity to the physically longer signal conductor of the pair than for the shorter signal conductor of the pair, thus lowering the effective dielectric constant around the signal conductor and decreasing its propagation delay.
However, as the dielectric constant is lowered, the impedance of the signal conductor rises. To maintain balanced impedance within the pair, the size of the signal conductor in closer proximity to the air may be increased in thickness or width. This results in two signal conductors with different physical geometry, but a more equal propagation delay and more inform impedance profile along the pair.
FIG. 2C shows a wafer 220 in cross section taken along the line 2C-2C in FIG. 2B. As shown, a plurality of differential pairs 3401 . . . 3404 are held in an array within insulative portion 240 of housing 260. In the illustrated embodiment, the array, in cross-section, is a linear array, forming a column of conductive elements.
Slots 2641 . . . 2644 are intersected by the cross section and are therefore visible in FIG. 2C. As can be seen, slots 2641 . . . 2644 create regions of air adjacent the longer conductor in each differential pair 3401, 3402 . . . 3404. Though, air is only one example of a material with a low dielectric constant that may be used for de-skewing a connector. Regions comparable to those occupied by slots 2641 . . . 2644 as shown in FIG. 2C could be formed with a plastic with a lower dielectric constant than the plastic used to form other portions of housing 260. As another example, regions of lower dielectric constant could be formed using different types or amounts of fillers. For example, lower dielectric constant regions could be molded from plastic having less glass fiber reinforcement than in other regions.
FIG. 2C also illustrates positioning and relative dimensions of signal and ground conductors that may be used in some embodiments. As shown in FIG. 2C, intermediate portions of the signal conductors 3101A . . . 3104A and 3101B . . . 3104B are embedded within housing 260 to form a column. Intermediate portions of ground conductors 3301 . . . 3304 may also be held within housing 260 in the same column.
Ground conductors 3301, 3302 and 3303 are positioned between two adjacent differential pairs 3401, 3402 . . . 3404 within the column. Additional ground conductors may be included at either or both ends of the column. In wafer 220A, as illustrated in FIG. 2C, a ground conductor 3304 is positioned at one end of the column. As shown in FIG. 2C, in some embodiments, each ground conductor 3301 . . . 3304 is preferably wider than the signal conductors of differential pairs 3401 . . . 3404. In the cross-section illustrated, the intermediate portion of each ground conductor has a width that is equal to or greater than three times the width of the intermediate portion of a signal conductor. In the pictured embodiment, the width of each ground conductor is sufficient to span at least the same distance along the column as a differential pair.
In the pictured embodiment, each ground conductor has a width approximately five times the width of a signal conductor such that in excess of 50% of the column width occupied by the conductive elements is occupied by the ground conductors. In the illustrated embodiment, approximately 70% of the column width occupied by conductive elements is occupied by the ground conductors 3301 . . . 3304. Increasing the percentage of each column occupied by a ground conductor can decrease cross talk within the connector.
Other techniques can also be used to manufacture wafer 220A to reduce crosstalk or otherwise have desirable electrical properties. In some embodiments, one or more portions of the housing 260 are formed from a material that selectively alters the electrical and/or electromagnetic properties of that portion of the housing, thereby suppressing noise and/or crosstalk, altering the impedance of the signal conductors or otherwise imparting desirable electrical properties to the signal conductors of the wafer.
In the embodiment illustrated in FIGS. 2A-2C, housing 260 includes an insulative portion 240 and a lossy portion 250. In one embodiment, the lossy portion 250 may include a thermoplastic material filled with conducting particles. The fillers make the portion “electrically lossy.” In one embodiment, the lossy regions of the housing are configured to reduce crosstalk between at least two adjacent differential pairs 3401 . . . 3404. The insulative regions of the housing may be configured so that the lossy regions do not attenuate signals carried by the differential pairs 3401 . . . 3404 an undesirable amount.
Materials that conduct, but with some loss, over the frequency range of interest are referred to herein generally as “lossy” materials. Electrically lossy materials can be formed from lossy dielectric and/or lossy conductive materials. The frequency range of interest depends on the operating parameters of the system in which such a connector is used, but will generally be between about 1 GHz and 25 GHz, though higher frequencies or lower frequencies may be of interest in some applications. Some connector designs may have frequency ranges of interest that span only a portion of this range, such as 1 to 10 GHz or 3 to 15 GHz.
Electrically lossy material can be formed from material traditionally regarded as dielectric materials, such as those that have an electric loss tangent greater than approximately 0.003 in the frequency range of interest. The “electric loss tangent” is the ratio of the imaginary part to the real part of the complex electrical permittivity of the material.
Electrically lossy materials can also be formed from materials that are generally thought of as conductors, but are either relatively poor conductors over the frequency range of interest, contain particles or regions that are sufficiently dispersed that they do not provide high conductivity or otherwise are prepared with properties that lead to a relatively weak bulk conductivity over the frequency range of interest. Electrically lossy materials typically have a conductivity of about 1 siemans/meter to about 6.1×107 siemans/meter, preferably about 1 siemans/meter to about 1×107 siemans/meter and most preferably about 1 siemans/meter to about 30,000 siemans/meter.
Electrically lossy materials may be partially conductive materials, such as those that have a surface resistivity between 1 Ω/square and 106 Ω/square. In some embodiments, the electrically lossy material has a surface resistivity between 1 Ω/square and 103 Ω/square. In some embodiments, the electrically lossy material has a surface resistivity between 10 Ω/square and 100 Ω/square. As a specific example, the material may have a surface resistivity of between about 20 Ω/square and 40 Ω/square.
In some embodiments, electrically lossy material is formed by adding to a binder a filler that contains conductive particles. Examples of conductive particles that may be used as a filler to form an electrically lossy material include carbon or graphite formed as fibers, flakes or other particles. Metal in the form of powder, flakes, fibers or other particles may also be used to provide suitable electrically lossy properties. Alternatively, combinations of fillers may be used. For example, metal plated carbon particles may be used. Silver and nickel are suitable metal plating for fibers. Coated particles may be used alone or in combination with other fillers, such as carbon flake. In some embodiments, the conductive particles disposed in the lossy portion 250 of the housing may be disposed generally evenly throughout, rendering a conductivity of the lossy portion generally constant. An other embodiments, a first region of the lossy portion 250 may be more conductive than a second region of the lossy portion 250 so that the conductivity, and therefore amount of loss within the lossy portion 250 may vary.
The binder or matrix may be any material that will set, cure or can otherwise be used to position the filler material. In some embodiments, the binder may be a thermoplastic material such as is traditionally used in the manufacture of electrical connectors to facilitate the molding of the electrically lossy material into the desired shapes and locations as part of the manufacture of the electrical connector. However, many alternative forms of binder materials may be used. Curable materials, such as epoxies, can serve as a binder. Alternatively, materials such as thermosetting resins or adhesives may be used. Also, while the above described binder materials may be used to create an electrically lossy material by forming a binder around conducting particle fillers, the invention is not so limited. For example, conducting particles may be impregnated into a formed matrix material or may be coated onto a formed matrix material, such as by applying a conductive coating to a plastic housing. As used herein, the term “binder” encompasses a material that encapsulates the filler, is impregnated with the filler or otherwise serves as a substrate to hold the filler.
Preferably, the fillers will be present in a sufficient volume percentage to allow conducting paths to be created from particle to particle. For example, when metal fiber is used, the fiber may be present in about 3% to 40% by volume. The amount of filler may impact the conducting properties of the material.
Filled materials may be purchased commercially, such as materials sold under the trade name Celestran® by Ticona. A lossy material, such as lossy conductive carbon filled adhesive preform, such as those sold by Techfilm of Billerica, Mass., US, may also be used. This preform can include an epoxy binder filled with carbon particles. The binder surrounds carbon particles, which acts as a reinforcement for the preform. Such a preform may be inserted in a wafer 220A to form all or part of the housing and may be positioned to adhere to ground conductors in the wafer. In some embodiments, the preform may adhere through the adhesive in the preform, which may be cured in a heat treating process. Various forms of reinforcing fiber, in woven or non-woven form, coated or non-coated may be used. Non-woven carbon fiber is one suitable material. Other suitable materials, such as custom blends as sold by RTP Company, can be employed, as the present invention is not limited in this respect.
In the embodiment illustrated in FIG. 2C, the wafer housing 260 is molded with two types of material. In the pictured embodiment, lossy portion 250 is formed of a material having a conductive filler, whereas the insulative portion 240 is formed from an insulative material having little or no conductive fillers, though insulative portions may have fillers, such as glass fiber, that alter mechanical properties of the binder material or impacts other electrical properties, such as dielectric constant, of the binder. In one embodiment, the insulative portion 240 is formed of molded plastic and the lossy portion is formed of molded plastic with conductive fillers. In some embodiments, the lossy portion 250 is sufficiently lossy that it attenuates radiation between differential pairs to a sufficient amount that crosstalk is reduced to a level that a separate metal plate is not required.
To prevent signal conductors 3101A, 3101B . . . 3104A, and 3104B from being shorted together and/or from being shorted to ground by lossy portion 250, insulative portion 240, formed of a suitable dielectric material, may be used to insulate the signal conductors. The insulative materials may be, for example, a thermoplastic binder into which non-conducting fibers are introduced for added strength, dimensional stability and to reduce the amount of higher priced binder used. Glass fibers, as in a conventional electrical connector, may have a loading of about 30% by volume. It should be appreciated that in other embodiments, other materials may be used, as the invention is not so limited.
In the embodiment of FIG. 2C, the lossy portion 250 includes a parallel region 336 and perpendicular regions 3341 . . . 3344. In one embodiment, perpendicular regions 3341 . . . 3344 are disposed between adjacent conductive elements that form separate differential pairs 3401 . . . 3404.
In some embodiments, the lossy regions 336 and 3341 . . . 3344 of the housing 260 and the ground conductors 3301 . . . 3304 cooperate to shield the differential pairs 3401 . . . 3404 to reduce crosstalk. The lossy regions 336 and 3341 . . . 3344 may be grounded by being electrically connected to one or more ground conductors. This configuration of lossy material in combination with ground conductors 3301 . . . 3304 reduces crosstalk between differential pairs within a column.
As shown in FIG. 2C, portions of the ground conductors 3301 . . . 3304, may be electrically connected to regions 336 and 3341 . . . 3344 by molding portion 250 around ground conductors 3401 . . . 3404. In some embodiments, ground conductors may include openings through which the material forming the housing can flow during molding. For example, the cross section illustrated in FIG. 2C is taken through an opening 332 in ground conductor 3301. Though not visible in the cross section of FIG. 2C, other openings in other ground conductors such as 3302 . . . 33304 may be included.
Material that flows through openings in the ground conductors allows perpendicular portions 3341 . . . 3344 to extend through ground conductors even though a mold cavity used to form a wafer 220A has inlets on only one side of the ground conductors. Additionally, flowing material through openings in ground conductors as part of a molding operation may aid in securing the ground conductors in housing 260 and may enhance the electrical connection between the lossy portion 250 and the ground conductors. However, other suitable methods of forming perpendicular portions 3341 . . . 3344 may also be used, including molding wafer 320A in a cavity that has inlets on two sides of ground conductors 3301 . . . 3304. Likewise, other suitable methods for securing the ground contacts 330 may be employed, as the present invention is not limited in this respect.
Forming the lossy portion 250 of the housing from a moldable material can provide additional benefits. For example, the lossy material at one or more locations can be configured to set the performance of the connector at that location. For example, changing the thickness of a lossy portion to space signal conductors closer to or further away from the lossy portion 250 can alter the performance of the connector. As such, electromagnetic coupling between one differential pair and ground and another differential pair and ground can be altered, thereby configuring the amount of loss for radiation between adjacent differential pairs and the amount of loss to signals carried by those differential pairs. As a result, a connector according to embodiments of the invention may be capable of use at higher frequencies than conventional connectors, such as for example at frequencies between 10-15 GHz or 3 to 6 GHz.
As shown in the embodiment of FIG. 2C, wafer 220A is designed to carry differential signals. Thus, each signal is carried by a pair of signal conductors 3101A and 3101B, . . . 3104A and 3104B. Preferably, each signal conductor is closer to the other conductor in its pair than it is to a conductor in an adjacent pair. For example, a pair 3401 carries one differential signal, and pair 3402 carries another differential signal. As can be seen in the cross section of FIG. 2C, signal conductor 3101B is closer to signal conductor 3101A than to signal conductor 3102A. Perpendicular lossy regions 3341 . . . 3344 may be positioned between pairs to provide shielding between the adjacent differential pairs in the same column.
Lossy material may also be positioned to reduce the crosstalk between adjacent pairs in different columns. FIG. 3 illustrates a cross-sectional view similar to FIG. 2C but with a plurality of subassemblies or wafers 320A, 320B aligned side to side to form multiple parallel columns.
As illustrated in FIG. 3, the plurality of signal conductors 340 may be arranged in differential pairs in a plurality of columns formed by positioning wafers side by side. It is not necessary that each wafer be the same and different types of wafers may be used.
It may be desirable for all types of wafers used to construct a daughter card connector to have an outer envelope of approximately the same dimensions so that all wafers fit within the same enclosure or can be attached to the same support member, such as stiffener 128 (FIG. 1). However, by providing different placement of the signal conductors, ground conductors and lossy portions in different wafers, the amount that the lossy material reduces crosstalk relative for the amount that it attenuates signals may be more readily configured. In one embodiment, two types of wafers are used, which are illustrated in FIG. 3 as subassemblies or wafers 320A and 320B.
Each of the wafers 320B may include structures similar to those in wafer 320A as illustrated in FIGS. 2A, 2B and 2C. As shown in FIG. 3, wafers 320B include multiple differential pairs, such as pairs 3405, 3406, 3407 and 3408. The signal pairs may be held within an insulative portion, such as 240B of a housing. Slots or other structures (not numbered) may be formed within the housing for skew equalization in the same way that slots 2641 . . . 2646 are formed in a wafer 220A.
The housing for a wafer 320B may also include lossy portions, such as lossy portions 250B. As with lossy portions 250 described in connection with wafer 320A in FIG. 2C, lossy portions 250B may be positioned to reduce crosstalk between adjacent differential pairs. The lossy portions 250B may be shaped to provide a desirable level of crosstalk suppression without causing an undesired amount of signal attenuation.
In the embodiment illustrated, lossy portion 250B may have a substantially parallel region 336B that is parallel to the columns of differential pairs 3405 . . . 3408. Each lossy portion 250B may further include a plurality of perpendicular regions 3341B . . . 3345B, which extend from the parallel region 336B. The perpendicular regions 3341B . . . 3345B may be spaced apart and disposed between adjacent differential pairs within a column.
Wafers 320B also include ground conductors, such as ground conductors 3305 . . . 3309. As with wafers 320A, the ground conductors are positioned adjacent differential pairs 3405 . . . 3408. Also, as in wafers 320A, the ground conductors generally have a width greater than the width of the signal conductors. In the embodiment pictured in FIG. 3, ground conductors 3305 . . . 3308 have generally the same shape as ground conductors 3301 . . . 3304 in a wafer 320A. However, in the embodiment illustrated, ground conductor 3309 has a width that is less than the ground conductors 3305 . . . 3308 in wafer 320B.
Ground conductor 3309 is narrower to provide desired electrical properties without requiring the wafer 320B to be undesirably wide. Ground conductor 3309 has an edge facing differential pair 3408. Accordingly, differential pair 3408 is positioned relative to a ground conductor similarly to adjacent differential pairs, such as differential pair 3308 in wafer 320B or pair 3404 in a wafer 320A. As a result, the electrical properties of differential pair 3408 are similar to those of other differential pairs. By making ground conductor 3309 narrower than ground conductors 3308 or 3304, wafer 320B may be made with a smaller size.
A similar small ground conductor could be included in wafer 320A adjacent pair 3401. However, in the embodiment illustrated, pair 3401 is the shortest of all differential pairs within daughter card connector 120. Though including a narrow ground conductor in wafer 320A could make the ground configuration of differential pair 3401 more similar to the configuration of adjacent differential pairs in wafers 320A and 320B, the net effect of differences in ground configuration may be proportional to the length of the conductor over which those differences exist. Because differential pair 3401 is relatively short, in the embodiment of FIG. 3, a second ground conductor adjacent to differential pair 3401, though it would change the electrical characteristics of that pair, may have relatively little net effect. However, in other embodiments, a further ground conductor may be included in wafers 320A.
FIG. 3 illustrates a further feature possible when using multiple types of wafers to form a daughter card connector. Because the columns of contacts in wafers 320A and 320B have different configurations, when wafer 320A is placed side by side with wafer 320B, the differential pairs in wafer 320A are more closely aligned with ground conductors in wafer 320B than with adjacent pairs of signal conductors in wafer 320B. Conversely, the differential pairs of wafer 320B are more closely aligned with ground conductors than adjacent differential pairs in the wafer 320A.
For example, differential pair 3406 is proximate ground conductor 3302 in wafer 320A. Similarly, differential pair 3403 in wafer 320A is proximate ground conductor 3307 in wafer 320B. In this way, radiation from a differential pair in one column couples more strongly to a ground conductor in an adjacent column than to a signal conductor in that column. This configuration reduces crosstalk between differential pairs in adjacent columns.
Wafers with different configurations may be formed in any suitable way. FIG. 4A illustrates a step in the manufacture of wafers 320A and 320B according to one embodiment. In the illustrated embodiment, wafer strip assemblies, each containing conductive elements in a configuration desired for one column of a daughter card connector, are formed. A housing is then molded around the conductive elements in each wafer strip assembly in an insert molding operation to form a wafer.
To facilitate the manufacture of wafers, signal conductors, of which signal conductor 420 is numbered and ground conductors, of which ground conductor 430 is numbered, may be held together on a lead frame 400 as shown in FIG. 4A. As shown, the signal conductors 420 and the ground conductors 430 are attached to one or more carrier strips 402. In one embodiment, the signal conductors and ground conductors are stamped for many wafers on a single sheet. The sheet may be metal or may be any other material that is conductive and provides suitable mechanical properties for making a conductive element in an electrical connector. Phosphor-bronze, beryllium copper and other copper alloys are example of materials that may be used.
FIG. 4A illustrates a portion of a sheet of metal in which wafer strip assemblies 410A, 410B have been stamped. Wafer strip assemblies 410A, 410B may be used to form wafers 320A and 320B, respectively. Conductive elements may be retained in a desired position on carrier strips 402. The conductive elements may then be more readily handled during manufacture of wafers. Once material is molded around the conductive elements, the carrier strips may be severed to separate the conductive elements. The wafers may then be assembled into daughter board connectors of any suitable size.
FIG. 4A also provides a more detailed view of features of the conductive elements of the daughter card wafers. The width of a ground conductor, such as ground conductor 430, relative to a signal conductor, such as signal conductor 420, is apparent. Also, openings in ground conductors, such as opening 332, are visible.
The wafer strip assemblies shown in FIG. 4A provide just one example of a component that may be used in the manufacture of wafers. For example, in the embodiment illustrated in FIG. 4A, the lead frame 400 includes tie bars 452, 454 and 456 that connect various portions of the signal conductors 420 and/or ground strips 430 to the lead frame 400. These tie bars may be severed during subsequent manufacturing processes to provide electronically separate conductive elements. A sheet of metal may be stamped such that one or more additional carrier strips are formed at other locations and/or bridging members between conductive elements may be employed for positioning and support of the conductive elements during manufacture. Accordingly, the details shown in FIG. 4A are illustrative and not a limitation on the invention.
Although the lead frame 400 is shown as including both ground conductors 430 and the signal conductors 420, the present invention is not limited in this respect. For example, the respective conductors may be formed in two separate lead frames. Indeed, no lead frame need be used and individual conductive elements may be employed during manufacture. It should be appreciated that molding over one or both lead frames or the individual conductive elements need not be performed at all, as the wafer may be assembled by inserting ground conductors and signal conductors into preformed housing portions, which may then be secured together with various features including snap fit features.
FIG. 4B illustrates a detailed view of the mating contact end of a differential pair 4241 positioned between two ground mating contacts 4341 and 4342. As illustrated, the ground conductors may include mating contacts of different sizes. The embodiment pictured has a large mating contact 4342 and a small mating contact 4341. To reduce the size of each wafer, small mating contacts 4341 may be positioned on one or both ends of the wafer.
FIG. 4B illustrates features of the mating contact portions of the conductive elements within the wafers forming daughter board connector 120. FIG. 4B illustrates a portion of the mating contacts of a wafer configured as wafer 320B. The portion shown illustrates a mating contact 4341 such as may be used at the end of a ground conductor 3309 (FIG. 3). Mating contacts 4241 may form the mating contact portions of signal conductors, such as those in differential pair 3408 (FIG. 3). Likewise, mating contact 4342 may form the mating contact portion of a ground conductor, such as ground conductor 3308 (FIG. 3).
In the embodiment illustrated in FIG. 4B, each of the mating contacts on a conductive element in a daughter card wafer is a dual beam contact. Mating contact 4341 includes beams 4601 and 4602. Mating contacts 4241 includes four beams, two for each of the signal conductors of the differential pair terminated by mating contact 4241. In the illustration of FIG. 4B, beams 4603 and 4604 provide two beams for a contact for one signal conductor of the pair and beams 4605 and 4606 provide two beams for a contact for a second signal conductor of the pair. Likewise, mating contact 4342 includes two beams 4607 and 4608.
Each of the beams includes a mating surface, of which mating surface 462 on beam 460, is numbered. To form a reliable electrical connection between a conductive element in the daughter card connector 120 and a corresponding conductive element in backplane connector 150, each of the beams 4601 . . . 4608 may be shaped to press against a corresponding mating contact in the backplane connector 150 with sufficient mechanical force to create a reliable electrical connection. Having two beams per contact increases the likelihood that an electrical connection will be formed even if one beam is damaged, contaminated or otherwise precluded from making an effective connection.
Each of beams 4601 . . . 4608 has a shape that generates mechanical force for making an electrical connection to a corresponding contact. In the embodiment of FIG. 4B, the signal conductors terminating at mating contact 4241 may have relatively narrow intermediate portions 4841 and 4842 within the housing of wafer 320D. However, to form an effective electrical connection, the mating contact portions 4241 for the signal conductors may be wider than the intermediate portions 4841 and 4842. Accordingly, FIG. 4B shows broadening portions 4801 and 4802 associated with each of the signal conductors.
In the illustrated embodiment, the ground conductors adjacent broadening portions 4801 and 4802 are shaped to conform to the adjacent edge of the signal conductors. Accordingly, mating contact 4341 for a ground conductor has a complementary portion 4821 with a shape that conforms to broadening portion 4801. Likewise, mating contact 4342 has a complementary portion 4822 that conforms to broadening portion 4802. By incorporating complementary portions in the ground conductors, the edge-to-edge spacing between the signal conductors and adjacent ground conductors remains relatively constant, even as the width of the signal conductors change at the mating contact region to provide desired mechanical properties to the beams. Maintaining a uniform spacing may further contribute to desirable electrical properties for an interconnection system according to an embodiment of the invention.
Some or all of the construction techniques employed within daughter card connector 120 for providing desirable characteristics may be employed in backplane connector 150. In the illustrated embodiment, backplane connector 150, like daughter card connector 120, includes features for providing desirable signal transmission properties. Signal conductors in backplane connector 150 are arranged in columns, each containing differential pairs interspersed with ground conductors. The ground conductors are wide relative to the signal conductors. Also, adjacent columns have different configurations. Some of the columns may have narrow ground conductors at the end to save space while providing a desired ground configuration around signal conductors at the ends of the columns. Additionally, ground conductors in one column may be positioned adjacent to differential pairs in an adjacent column as a way to reduce crosstalk from one column to the next. Further, lossy material may be selectively placed within the shroud of backplane connector 150 to reduce crosstalk, without providing an undesirable level attenuation for signals. Further, adjacent signals and grounds may have conforming portions so that in locations where the profile of either a signal conductor or a ground conductor changes, the signal-to-ground spacing may be maintained.
FIGS. 5A-5B illustrate an embodiment of a backplane connector 150 in greater detail. In the illustrated embodiment, backplane connector 150 includes a shroud 510 with walls 512 and floor 514. Conductive elements are inserted into shroud 510. In the embodiment shown, each conductive element has a portion extending above floor 514. These portions form the mating contact portions of the conductive elements, collectively numbered 154. Each conductive element has a portion extending below floor 514. These portions form the contact tails and are collectively numbered 156.
The conductive elements of backplane connector 150 are positioned to align with the conductive elements in daughter card connector 120. Accordingly, FIG. 5A shows conductive elements in backplane connector 150 arranged in multiple parallel columns. In the embodiment illustrated, each of the parallel columns includes multiple differential pairs of signal conductors, of which differential pairs 5401, 5402 . . . 5404 are numbered. Each column also includes multiple ground conductors. In the embodiment illustrated in FIG. 5A, ground conductors 5301, 5302 . . . 5305 are numbered.
Ground conductors 5301 . . . 5305 and differential pairs 5401 . . . 5404 are positioned to form one column of conductive elements within backplane connector 150. That column has conductive elements positioned to align with a column of conductive elements as in a wafer 320B (FIG. 3). An adjacent column of conductive elements within backplane connector 150 may have conductive elements positioned to align with mating contact portions of a wafer 320A. The columns in backplane connector 150 may alternate configurations from column to column to match the alternating pattern of wafers 320A, 320B shown in FIG. 3.
Ground conductors 5302, 5303 and 5304 are shown to be wide relative to the signal conductors that make up the differential pairs 5401 . . . 5404. Narrower ground conductive elements, which are narrower relative to ground conductors 5302, 5303 and 5304, are included at each end of the column. In the embodiment illustrated in FIG. 5A, narrower ground conductors 5301 and 5305 are including at the ends of the column containing differential pairs 5401 . . . 5404 and may, for example, mate with a ground conductor from daughter card 120 with a mating contact portion shaped as mating contact 4341 (FIG. 4B).
FIG. 5B shows a view of backplane connector 150 taken along the line labeled B-B in FIG. 5A. In the illustration of FIG. 5B, an alternating pattern of columns of 560A-560B is visible. A column containing differential pairs 5401 . . . 5404 is shown as column 560B.
FIG. 5B shows that shroud 510 may contain both insulative and lossy regions. In the illustrated embodiment, each of the conductive elements of a differential pair, such as differential pairs 5401 . . . 5404, is held within an insulative region 522. Lossy regions 520 may be positioned between adjacent differential pairs within the same column and between adjacent differential pairs in adjacent columns. Lossy regions 520 may connect to the ground contacts such as 5301 . . . 5305. Sidewalls 512 may be made of either insulative or lossy material.
FIGS. 6A, 6B and 6C illustrate in greater detail conductive elements that may be used in forming backplane connector 150. FIG. 6A shows multiple wide ground contacts 5302, 5303 and 5304. In the configuration shown in FIG. 6A, the ground contacts are attached to a carrier strip 620. The ground contacts may be stamped from a long sheet of metal or other conductive material, including a carrier strip 620. The individual contacts may be severed from carrier strip 620 at any suitable time during the manufacturing operation.
As can be seen, each of the ground contacts has a mating contact portion shaped as a blade. For additional stiffness, one or more stiffening structures may be formed in each contact. In the embodiment of FIG. 6A, a rib, such as 610 is formed in each of the wide ground conductors.
Each of the wide ground conductors, such as 5302 . . . 5304 includes two contact tails. For ground conductor 5302 contact tails 6561 and 6562 are numbered. Providing two contact tails per wide ground conductor provides for a more even distribution of grounding structures throughout the entire interconnection system, including within backplane 160 because each of contact tails 6561 and 6562 will engage a ground via within backplane 160 that will be parallel and adjacent a via carrying a signal. FIG. 4A illustrates that two ground contact tails may also be used for each ground conductor in daughter card connector.
FIG. 6B shows a stamping containing narrower ground conductors, such as ground conductors 5301 and 5305. As with the wider ground conductors shown in FIG. 6A, the narrower ground conductors of FIG. 6B have a mating contact portion shaped like a blade.
As with the stamping of FIG. 6A, the stamping of FIG. 6B containing narrower grounds includes a carrier strip 630 to facilitate handling of the conductive elements. The individual ground conductors may be severed from carrier strip 630 at any suitable time, either before or after insertion into backplane connector shroud 510.
In the embodiment illustrated, each of the narrower ground conductors, such as 5301 and 5302, contains a single contact tail such as 6563 on ground conductor 5301 or contact tail 6564 on ground conductor 5305. Even though only one ground contact tail is included, the relationship between number of signal contacts is maintained because narrow ground conductors as shown in FIG. 6B are used at the ends of columns where they are adjacent a single signal conductor. As can be seen from the illustration in FIG. 6B, each of the contact tails for a narrower ground conductor is offset from the center line of the mating contact in the same way that contact tails 6561 and 6562 are displaced from the center line of wide contacts. This configuration may be used to preserve the spacing between a ground contact tail and an adjacent signal contact tail.
As can be seen in FIG. 5A, in the pictured embodiment of backplane connector 150, the narrower ground conductors, such as 5301 and 5305, are also shorter than the wider ground conductors such as 5302 . . . 5304. The narrower ground conductors shown in FIG. 6B do not include a stiffening structure, such as ribs 610 (FIG. 6A). However, embodiments of narrower ground conductors may be formed with stiffening structures.
FIG. 6C shows signal conductors that may be used to form backplane connector 150. The signal conductors in FIG. 6C, like the ground conductors of FIGS. 6A and 6B, may be stamped from a sheet of metal. In the embodiment of FIG. 6C, the signal conductors are stamped in pairs, such as pairs 5401 and 5402. The stamping of FIG. 6C includes a carrier strip 640 to facilitate handling of the conductive elements. The pairs, such as 5401 and 5402, may be severed from carrier strip 640 at any suitable point during manufacture.
As can be seen from FIGS. 5A, 6A, 6B and 6C, the signal conductors and ground conductors for backplane connector 150 may be shaped to conform to each other to maintain a consistent spacing between the signal conductors and ground conductors. For example, ground conductors have projections, such as projection 660, that position the ground conductor relative to floor 514 of shroud 510. The signal conductors have complimentary portions, such as complimentary portion 662 (FIG. 6C) so that when a signal conductor is inserted into shroud 510 next to a ground conductor, the spacing between the edges of the signal conductor and the ground conductor stays relatively uniform, even in the vicinity of projections 660.
Likewise, signal conductors have projections, such as projections 664 (FIG. 6C). Projection 664 may act as a retention feature that holds the signal conductor within the floor 514 of backplane connector shroud 510 (FIG. 5A). Ground conductors may have complimentary portions, such as complementary portion 666 (FIG. 6A). When a signal conductor is placed adjacent a ground conductor, complimentary portion 666 maintains a relatively uniform spacing between the edges of the signal conductor and the ground conductor, even in the vicinity of projection 664.
FIGS. 6A, 6B and 6C illustrate examples of projections in the edges of signal and ground conductors and corresponding complimentary portions formed in an adjacent signal or ground conductor. Other types of projections may be formed and other shapes of complementary portions may likewise be formed.
To facilitate use of signal and ground conductors with complementary portions, backplane connector 150 may be manufactured by inserting signal conductors and ground conductors into shroud 510 from opposite sides. As can be seen in FIG. 5A, projections such as 660 (FIG. 6A) of ground conductors press against the bottom surface of floor 514. Backplane connector 150 may be assembled by inserting the ground conductors into shroud 510 from the bottom until projections 660 engage the underside of floor 514. Because signal conductors in backplane connector 150 are generally complementary to the ground conductors, the signal conductors have narrow portions adjacent the lower surface of floor 514. The wider portions of the signal conductors are adjacent the top surface of floor 514. Because manufacture of a backplane connector may be simplified if the conductive elements are inserted into shroud 510 narrow end first, backplane connector 150 may be assembled by inserting signal conductors into shroud 510 from the upper surface of floor 514. The signal conductors may be inserted until projections, such as projection 664, engage the upper surface of the floor. Two-sided insertion of conductive elements into shroud 510 facilitates manufacture of connector portions with conforming signal and ground conductors.
FIGS. 7A and 7B illustrate schematically a connector with complementary conductive elements and a method of manufacturing such a connector. FIG. 7A illustrates in cross-section a portion of an electrical connector. The connector illustrated may be a backplane connector 150 as shown in FIGS. 5A and 5B. However, the specific type of connector is not a limitation on the invention.
The portion illustrated in FIG. 7A is a cross-section through a portion of one column of conductive elements in the connector. As shown, conductive elements 740, 740, 7402, and 7403 have a similar shape. In the embodiment illustrated, conductive elements 7402 and 7403 may serve as signal conductors. Accordingly, these conductive elements may be arranged in pairs. FIG. 7A shows conductive elements 7402 and 7403 arranged as a pair positioned to carry a differential signal. The portion of the connector illustrated in FIG. 7A does not show a second conductive element with which conductive element 740 is paired. However, an additional signal conductor adjacent conductive element 740 may be present. More generally, the pattern of conductive elements illustrated in FIG. 7A may be extended to form a column of conductive elements of any suitable length with any suitable arrangement of conductive elements. The conductive elements in that column may be shaped like either conductive element 740 or conductive element 790. Accordingly, the shape are manufacture of FIGS. 7A and 7B is explained by reference to conductive elements 740 and 790. However, similar description applies to other conductive elements such as conductive elements 7402, 7403 and 7902.
In the embodiment illustrated, conductive elements 740 and 790 each contains a mating contact portion, 754 and 714, respectively. In the embodiment illustrated, each mating contact portion is shaped as a blade. However, the shape of the mating contact portion is not a limitation on the invention and conductive elements may be formed with mating contact portions of any suitable shape.
FIG. 7A also shows conductive element 790 and 7902. A conductive element such as conductive element 790 or 7902 is shown adjacent each pair of conductive elements that acts as signal conductors. In the embodiment illustrated, conductive element 790 is shown to be wider than conductive element 740. Additionally, conductive element 790 is shown with two contact tails, 716A and 716B. As described above, such a configuration may be desirable for a ground conductor. Accordingly, conductive element 790 may represent a ground conductor. Though, the invention is not limited by the type of signals or potentials carried by the conductive elements.
To construct a high-density connector, it may be desirable to position the signal conductors, such as conductive elements 740, 7402 and 7403 close to adjacent ground conductors, such as 790 and 7902. However, in forming an electrical connector, it is sometimes desirable to form conductive elements with projecting portions, such as projections 760 and 730. When the conductive elements are placed close together, projections can have a significant impact on the electrical properties of the conductive elements used for carrying signals.
For example, conductive element 740 is illustrated with projections 760. Projection 760 may be a barb or other retention feature that engages housing 758 when conductive element 740 is inserted into housing 758. Conductive element 790 also contains projections 730. Projections 730 may, like projections 760, serve to engage housing 758. Alternatively, projections 730 may allow separation between contact tails 716A and 716B so that current flows in a desired pattern though conductive element 790 or to position ground vias in a printed circuit board close to vias carrying signals.
Regardless of the reason that conductive elements contain projecting portions, such as projections 730 and 760, when the conductive elements are positioned close together, the projecting portions can alter the electrical characteristics of a conductive element. For example, the spacing between a signal conductor and a ground conductor can influence the impedance of the signal conductor. Having projections or other features on a conductive element that changes the spacing between a signal and ground conductor, even in a relatively limited region, can alter the impedance of the signal conductor and may lead to undesirable signal properties.
To avoid undesirably large changes in impedance, FIG. 7A illustrates that conductive elements 740 and 790 are formed with relieved portions 766 and 736, respectively. Each relieved portion is configured to be complementary to a projection in an adjacent conductive element. For example, relieved portion 736 is configured to be complementary to projection 760. Likewise, relieved portion 766 is configured to be complementary to projection 730. As seen in FIG. 7A, when conductive element 740 and conductive element 790 are affixed to housing 758, projection 760 is adjacent relieved portion 736. Relieved portion 766 is adjacent projection 730. Accordingly, the spacing between conductive element 740 and conductive element 790 is relatively uniform along the length of the conductive elements.
In the example illustrated, conductive element 740 and conductive element 790 have an edge-to-edge spacing D2 in a cross-section through mating contact portions 714 and 754. In a cross-section through projection 760 and relieved portion 736, conductive element 740 and conductive element 790 have an edge-to-edge spacing of D3. In a cross-section through relieved portion 766 and projection 730, conductive element 740 and conductive element 790 have an edge-to-edge spacing of D1. As can be seen from FIG. 7A, the separations D1, D2 and D3 may not be exactly the same. However, because of the presence of relieved portions 736 and 766, there are no marked discontinuities in the edge-to-edge separation between conductive element 740 and conductive element 790 along the length of conductive element 740. Maintaining a relatively uniform spacing may be desirable when one of the conductive elements represents a signal conductor and the other represents a ground conductor.
The complementary features illustrated in FIG. 7A may be particularly desirable when the conductive elements are placed close together. In the embodiment illustrated, center line CL1 of conductive element 740 may be spaced from center line CL2 of conductive element 790 by a spacing on the order of one millimeter. In some embodiments, the spacing between center line CL1 and center line CL2 may be between approximately 0.8 millimeters and 1.5 millimeters. In other embodiments, the spacing may be approximately 1.1 millimeter.
With such small spacings, the projecting portions of adjacent conductive elements may overlap. For example, as shown in FIG. 7A, projection 760 overlaps projection 730. Likewise, projection 7302 overlaps projection 7602 of an adjacent conductive element 7402. FIG. 7B illustrates schematically a method by which a connector containing conductive elements with complementary portions may be assembled. FIG. 7B shows a portion of a connector, such as backplane connector 150 (FIG. 1). In the embodiment illustrated, the connector is assembled by inserting conductive elements, such as conductive elements 740 and 790, into a housing, such as insulative housing 758. Such a housing may be formed with openings to receive conductive elements.
To assemble a connector containing conductive elements 740 and 790, the conductive elements may be inserted into openings in the housing 758. As shown, conductive element 740 is inserted into opening 712 and conductive element 790 is inserted into opening 722. Each of the openings 712 and 722, has a shape that generally matches the portions of the conductive element inserted into the opening. However, some portions of each of the conductive elements may be larger than the corresponding opening. For example, opening 712 may have a width smaller than the width of projection 760, such that when conductive element 740 is inserted into opening 712, projection 760 presses against the walls of opening 712. In other embodiments, housing 758 may be plastic or other soft material that may be displaced by projections 760 when conductive element 740 is inserted into opening 712. Regardless of the specific mechanism by which conductive element 740 engages housing 758, the engaging mechanism may include projections such as projection 760. As illustrated in FIG. 7B, conductive element 740 is inserted from a top surface 710 housing 758. Similarly shaped conductive elements, such as 7402 and 7403 (FIG. 7A) may be inserted in the same operation as conductive element 740. Conductive element 790 is inserted through opening 722 in a lower surface 720 of housing 758. Similar conductive elements, such as conductive element 7902 (FIG. 7A) may be inserted in the same operation. By inserting different types of conductive elements from different sides of the connector housing, and constructing each type of conductive element such that projections that would overlap projections on another type of conductive element are positioned near the surface through which the conductive element is inserted, the projections of adjacent conductive elements do not interfere with each other, even if they overlap
The conductive elements inserted through lower surface 720 and the conductive elements inserted through upper surface 710 may be inserted in the same operation using a tool that can access two surfaces of housing 758 simultaneously. Alternatively, the conductive element inserted through upper surface 710 and the conductive element inserted through lower surface 720 may be inserted in separate, sequential operations. The specific timing of the insertion is not a limitation of the invention. Accordingly, the conductive element may be inserted in any suitable order.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. For example, although many inventive aspects are shown and described with reference to a daughter board connector, it should be appreciated that the present invention is not limited in this regard, as the inventive concepts may be included in other types of electrical connectors, such as backplane connectors, cable connectors, stacking connectors, mezzanine connectors, or chip sockets.
As a further example, connectors with four differential signal pairs in a column were used to illustrate the inventive concepts. However, connectors with any desired number of signal conductors may be used.
Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

## Claims

1. An electrical connector comprising a plurality of conductive elements disposed in a column, the plurality of conductive elements comprising:
a) a first conductor, the first conductor having a first width along a first line in a plane through the column and a second width along a second line in the plane, the second width being greater than the first width; and
b) a second conductor, the second conductor being disposed adjacent the first conductor and having a third width along the first line and a fourth width along the second line, the third width being greater than the fourth width.

2. The electrical connector of claim 1, wherein the center to center spacing between the first conductor and the second conductor is the same along the first line and the second line.

3. The electrical connector of claim 1, wherein the third width is greater than the first width.

4. The electrical connector of claim 3, wherein the second conductor is a ground conductor and the first conductor is a signal conductor.

5. The electrical connector of claim 1, wherein:
i) the connector comprises a housing;
ii) each of the plurality of conductive elements has a portion disposed within the housing; and
iii) the first line is within the housing and the second line is outside the housing.

6. The electrical connector of claim 5, wherein the plurality of conductive elements and the housing comprise a first wafer in a daughter card connector.

7. The electrical connector of claim 6, wherein each of the plurality of conductive elements comprises a mating contact portion extending from the housing and the second line is positioned adjacent the mating contact portions of the plurality of conductive elements.

8. The electrical connector of claim 1, wherein:
i) the connector comprises a housing;
ii) each of the plurality of conductive elements has a portion disposed within the housing; and
iii) the first line is outside the housing and the second line is within the housing.

9. The electrical connector of claim 8, wherein the plurality of conductive elements and the housing comprise a backplane connector.

10. The electrical connector of claim 1, wherein:
i) the connector comprises a housing;
ii) each of the plurality of conductive elements has a portion disposed within the housing; and
iii) a portion of the first conductor of the second width along the second line comprises a retention features for securing the first conductor in the housing.

11. The electrical connector of claim 10, wherein the second conductor further comprises a contact tail extending from a portion of the third width.

12. The electrical connector of claim 1, comprising a plurality of parallel columns comprising the column and a plurality of additional columns parallel to the column, each of the parallel columns comprising:
a) a plurality of first type conductors, each first type conductor having the first width along a line parallel to the first line and a second width along a line parallel to the second line; and
b) a plurality of second type conductors, each second type conductor adjacent a first type conductor, and each second type conductor having the third width along the line parallel to the first line and the fourth width long the line parallel to the second line.

13. The electrical connector of claim 1, wherein:
the connector further comprises an insulative housing;
the first conductor has a first segment with a first edge having a projection along the second line and each of the second conductors has a second segment with a second edge having a projection along the third line; and
the first conductor and the second conductor are inserted into the insulative housing with the first edge of the first conductor facing a second edge of the second conductor.

14. The electrical connector of claim 13, wherein the first conductor is inserted into the housing with the projection of the first conductor engaging the housing.

15. The electrical connector of claim 1, wherein:
the connector further comprises a housing;
first conductor has a first segment with a first edge having a projection;
the second conductor has a second edge with a second segment, the second segment having a relieved portion complementary to the projection of the first conductor; and
the first conductor and the second conductors are inserted in the housing such that the first edge of the first conductor is adjacent the second edge of the second conductor and the first segment is aligned with the second segment.

16. The electrical connector of claim 15, wherein the housing comprises a backplane shroud having opposing side walls and each of the first conductor and the second conductor comprises a blade-shaped mating contact portion and the first conductor and the second conductor are inserted in the housing with the blade-shaped mating contact portions of the first conductor and the second conductor positioned between the opposing side walls.

17. An electrical connector comprising a plurality of conductive elements disposed in a column, the plurality of conductive elements comprising:
a) a first conductor, the first conductor having a first segment with a first edge having a projecting portion; and
b) a second conductor, the second conductor having a second edge, the second conductor being positioned with the second edge adjacent the first edge, the second edge having a second segment complimentary to the projecting portion of the first conductor, the second segment being aligned with the projecting portion along a line parallel to the column.

18. The electrical connector of claim 17, wherein:
i) the second conductor comprises a third segment along the second edge, the third segment having a second projecting portion; and
ii) the first conductor comprises a fourth segment along the first edge, the fourth segment complementary to the second projecting portion.

19. The electrical connector of claim 17, wherein the projecting portion of the first conductor comprises a transition between an intermediate portion of the first conductor and a beam forming a mating contact portion of the first conductor.

20. The electrical connector of claim 17, wherein the first conductor comprises a press-fit contact tail extending from the projecting portion.

21. The electrical connector of claim 17, comprising a plurality of parallel columns, the plurality comprising the column and a plurality of additional columns parallel to the column, each of the additional parallel columns comprising:
a) a plurality of first type conductors, each of the plurality of first type conductors having a first segment with a first edge having a projecting portion; and
b) a plurality of second type conductors, each of the plurality of second type conductors having a second edge adjacent a first edge of a first type conductor, each second edge having a second segment aligned with and complementary to the projecting portion of the first type conductor.

22. The electrical connector of claim 21, wherein the first type conductors comprise ground conductors and the second type conductors comprise signal conductors, the plurality of second type conductors being adapted and configured to provide a plurality of differential pairs, and the first segments and the second segments are adapted and configured to equalize signal to ground spacing over the length of the differential pairs.

23. A method of manufacturing an electrical connector having a housing and a plurality of first conductors and a plurality of second conductors, the method comprising:
a) inserting the first conductors into a housing from a first direction; and
b) inserting the second conductors in the housing from a second direction, opposite the first direction,
wherein:
i) each of the plurality of first conductors has a first segment with a first edge having a projection;
ii) each of the plurality of second conductors has a second edge with a second segment, the second segment having a relieved portion complementary to a projection of a first conductor;
iii) inserting the first conductors and the second conductors comprises inserting the first conductors and the second conductors with a first edge of a first conductor adjacent a second edge of a second conductor until the first segment is aligned with the second segment;
iv) the housing comprises a backplane shroud having opposing side walls;
v) each of the first conductors and the second conductors comprises a blade-shaped mating contact portion; and
vi) inserting the first conductors and inserting the second conductors comprises inserting the first conductors and the second conductors until the blade-shaped mating contact portions of the first conductors and the second conductors are positioned between the opposing side walls.