1. Field of Invention
This invention relates generally to electrical interconnection systems and more specifically to high density, 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. Shields can be in the form of grounded metal structures or may be in the form of electrically lossy material.
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.
Maintaining signal integrity can be a particular challenge in the mating interface of the connector. At the mating interface, force must be generated to press conductive elements from the separable connectors together so that a reliable electrical connection is made between the two conductive elements. Frequently, this force is generated by spring characteristics of the mating contact portions in one of the connectors. For example, the mating contact portions of one connector may contain one or more members shaped as beams. As the connectors are pressed together, these beams are deflected by a mating contact portion, shaped as a post or pin, in the other connector. The spring force generated by the beam as it is deflected provides a contact force.
For mechanical reliability, many contacts have multiple beams. In some instances, the beams are opposing, pressing on opposite sides of a mating contact portion of a conductive element from another connector. The beams may alternatively be parallel, pressing on the same side of a mating contact portion.
Regardless of the specific contact structure, the need to generate mechanical force imposes requirements on the shape of the mating contact portions. For example, the mating contact portions must be large enough to generate sufficient force to make a reliable electrical connection.
These mechanical requirements may preclude the use of shielding or may dictate the use of conductive material in places that alters the impedance of the conductive elements in the vicinity of the mating interface. Because abrupt changes in the impedance of a signal conductor can alter the signal integrity of that conductor, the mating contact portions are often accepted as being the noisy portion of the connector.
In accordance with techniques described herein, improved performance of an electrical connector may be provided with conductive elements configured to electrically compensate for structural artifacts of a manufacturing process.
Accordingly, some embodiments relate to an electrical connector comprising a housing; and a lead frame held within the housing. The lead frame may comprise a plurality of conductive members. The plurality of conductive members may comprise a first conductive member and a second conductive member. The lead frame may comprise an artifact of severing a tie bar between the first conductive member and the second conductive member. The lead frame may also comprise a tie bar compensation portion adjacent the artifact.
In another aspect, a method of manufacturing an electrical connector may be provided. The method may comprise molding a housing around a lead frame, the lead frame comprising a plurality of conductive members, the plurality of conductive members comprising a first conductive member and a second conductive member joined by a tie bar. The method may include, subsequent to the molding, severing the tie bar, leaving an artifact of the severing in the lead frame. The lead frame may comprise a tie bar compensation portion adjacent the artifact.
The foregoing is a non-limiting summary of the invention, which is defined by the appended claims.
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:
The inventors have recognized and appreciated that performance of an electrical interconnection system may be improved through the use of features in conductive elements in an electrical connector to compensate for artifacts of manufacturing steps. In particular, the inventors have recognized and appreciated that some manufacturing processes for electrical connectors result in artifacts on some conductive elements within a lead frame that impact the spacing between edges of adjacent conductive elements. Severing tie bars in a lead frame, for example, may leave projections from some of the conductive elements because of a needed tolerance in the positioning of a punch to sever the tie bars without removing desired portions of the conductive elements.
Though the projections, or other artifacts, may seem small, the inventors have recognized and appreciated that in some locations within the connector, even small artifacts on a conductive element can change the high frequency impedance of conductive members acting as signal conductors. These changes in impedance may create signal reflections or mode conversions that in turn create cross-talk and/or excite resonances in the connector that degrade signal performance.
Accordingly, in some embodiments, an electrical connector may be manufactured with a lead frame that includes compensation portions in close proximity to locations where the manufacturing operation will be performed. These compensation portions may be shaped to electrically offset the effects of an artifact of the manufacturing operation.
As a specific example, the lead frame may be stamped with tie bars, which may ensure a desired spacing between conductive elements. Before the connector is used, the tie bars may be severed to ensure that the conductive elements are electrically isolated from each other within the connector. The connector housing may be formed with a cavity exposing the tie bar such that a punch, or other tool, used to sever the tie bars can access the tie bar without cutting the housing, which could dull the tool quickly. Though, even if the housing is not formed with a cavity, the punch or other tool may create such a cavity within the housing when severing the tie bar.
The inventors have recognized and appreciated that conventional manufacturing approaches have tolerance in positioning the punch relative to the tie bar such that the punch cannot be precisely aligned with the tie bar and only the tie bar to be sever. To compensate for these tolerances, the punch may be smaller than the tie bar such that, after severing the tie bar, portions of the tie bar will remain as projections from an edge of one or both of the conductive elements previously joined by the tie bar. Other edges of the conductive elements may have offsetting features, such as projections or concavities that tend to equalize the impedance at high frequencies along some or all of the conductive elements.
In some embodiments, an electrical connector may be formed with conductive elements shaped to carry differential signals with edge-to-edge coupling. When an artifact appears on one edge of the conductive element shaped to be a differential signal pair, a compensation portion may be formed on an opposite edge of the signal conductor. As a specific example, a lead frame for a differential connector may have conductive elements that are wider, which may be designated as ground conductors, and conductive elements that are narrower, which may be designated as signal conductors. The conductive elements may be arranged in a repeating pattern of ground, signal, signal, ground. Tie bars may be used between each signal and an adjacent ground and between the adjacent signals. However, these tie bars may be laid out so that there are not tie bars directly opposite each other on a signal conductor. Rather, opposite each tie bar may be a compensation portion. Further details and example of compensation portions are described in the following examples.
Techniques as described herein to improve the high frequency performance of an electrical interconnection system may be applied to connectors of any suitable form. However, an example of a connector that may be improved using techniques as described herein is provided in connection with
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.
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 of conductive elements (see
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
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
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
The contact tails 126 extend through a surface of daughter card connector 120 adapted to be mounted to daughter card 140. The contact tails 126 electrically connect the conductive elements within daughter card 140 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. Though, conductive elements with other shapes may be substituted for some or all of the conductive elements illustrated in
In some embodiments, 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.
A connector as shown in
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 plurality of wafers to support the wafers in the desired orientation.
Each wafer 1221 . . . 1226 may include attachment features 242, 244 (see
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, some embodiments 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
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 conductor to the other end is known as the propagation delay. In some embodiments, it is desirable that both signal conductors 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.
Slots 2641 . . . 2644 are intersected by the cross section and are therefore visible in
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
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. However, one approach to increasing the number of signal conductors per unit length in the column direction (illustrated by dimension C in
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
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 or 3 to 6 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. In 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
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
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 coupled to one or more ground conductors. Such coupling may be the result of direct contact between the electrically lossy material and a ground conductor or may be indirect, such as through capacitive coupling. This configuration of lossy material in combination with ground conductors 3301 . . . 3304 reduces crosstalk between differential pairs within a column.
As shown in
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 10-25 GHz.
As shown in the embodiment of
Lossy material may also be positioned to reduce the crosstalk between adjacent pairs in different columns.
As illustrated in
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 (
Each of the wafers 320B may include structures similar to those in wafer 320A as illustrated in
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
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
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
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.
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 to form a lead frame 400 as shown in
The wafer strip assemblies shown in
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.
In the embodiment illustrated in
Each of the beams includes a mating surface, of which mating surface 462 on beam 4601 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
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 of attenuation to 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.
The conductive elements of backplane connector 150 are positioned to align with the conductive elements in daughter card connector 120. Accordingly,
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 (
Ground conductors 5302, 5303 and 5304 are shown to be wide relative to the signal conductors that make up the differential pairs by 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
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
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.
As with the stamping of
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
As can be seen in
As can be seen from
Likewise, signal conductors have projections, such as projections 664 (
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
Regardless of the specific shape and size of the components and the techniques used to manufacture components of an electrical connector, may be selected to provide desired electrical properties, including a relatively uniform impedance along portions of the conductive elements serving as signal conductors. For example, techniques as described herein may be used to provide an impedance that varies by less than +/−10% or 5%, even at relatively high frequencies, for example up to 25 GHz, over the intermediate portions of the signal conductors within the housing. Though, even more precise impedance control may be provided in some embodiments, such as +/−1% or less or +/−0.5%.
One technique for providing a relatively constant impedance is to incorporate compensation portions into the lead frame to compensate for artifacts in the lead frame created during manufacturing operations.
In some embodiments, each conductive element of the lead frame is held to each adjacent conductive element by at least one tie bar, and in some instances multiple tie bars. In the view of
For simplicity of illustration, the housing is not shown in detail in
In the example illustrated, tie bar 810 joins conductive elements 802 and 804. A similar tie bar 812 joins conductive elements 806 and 808. This tie bar is exposed in window 822 of the housing. Tie bar 812 may also be severed, in the same or different step in the manufacturing operation as tie bar 810. If in the same operation, the tool used to sever the tie bars may have multiple punches. If a different operation, the tool and or the wafer may be moved between operations.
In the example illustrated, the conductive elements are elongated in a dimension that runs in the plane of the lead frame. The tie bars 810 and 812 are aligned in a direction transverse to this elongated dimension. However, there is no requirement that the tie bars be aligned.
In this example, conductive elements 802 and 808 may be wider than the pair of conductive elements 804 and 806. Accordingly, conductive elements 802 and 808 may be designated as ground conductors and conductive elements 804 and 806 may be signal conductors.
In this example, the signal to ground tie bars may be aligned. In embodiments in which the interior conductive elements 804 and 806 are intended to form a balanced pair, it may be desirable for the structures adjacent conductive element 804 mirror those adjacent conductive element 806 as close as possible. Though, it is not a requirement of the invention that the tie bars be aligned.
In this example, there is no tie bar between the signal conductors aligned with those signal to ground tie bars. Rather a compensation portion may be provided in the adjacent region between the conductive elements 804 and 806. In the example illustrated in
The manner in which this changed edge-to-edge spacing compensates for the tie bar is illustrated in
These projections, changing the edge-to-edge spacing between a signal conductor and a ground conductor may alter the impedance of the signal conductor. For example, they may increase the impedance in the region of the artifact. Though, other artifacts may decrease the impedance.
Accordingly, a signal propagating along the signal conductor will encounter a first impedance while propagating in sections of the signal conductor with a uniform, nominal width. Upon reaching the section containing the artifact, the signal may encounter a different impedance, which may create undesirable electrical properties, such as insertion loss or cross talk.
To compensate for the change in impedance, a compensation portion may be positioned adjacent the tie bar artifact. The compensation portion may be shaped to offset the change of impedance that would otherwise be caused by the artifacts of severing the tie bar. For example,
If the tie bar artifacts would tend to increase the impedance of the signal conductors, the compensation portions may tend to decreases the impedance. Though, the compensation portion may increase the impedance to offset for a decrease caused by an artifact. For example, the compensation portion may be concave, to increase edge-to-edge spacing as a way to change impedance.
It should be appreciated that the compensation portion is adjacent to the tie bar artifact so that the combined effect of these portions cancel out, rather than create different segments that vary the impedance up and down. The specific dimensions required for the portions to average out may depend on frequency of operation and other parameters. The compensation portion may be aligned with the artifact in a direction perpendicular to the edges, for example as illustrated in
Further, the shape and position of the tie bar compensation portion may vary depending on the shape and position of the tie bar artifacts.
As in the example of
In this example, the edge-to-edge spacing between signal conductors and adjacent grounds is approximately 0.3 mm. Though, the nominal spacing may have any suitable value, including between about 0.1 mm and 0.7 mm or between about 0.2 mm and 0.5 mm.
In the illustrated example, the edge-to-edge spacing between signal conductors is approximately 0.35 mm. Though, the nominal spacing may have any suitable value, including between about 0.1 mm and 0.7 mm or between about 0.2 mm and 0.5 mm.
In this example, the punch used to sever tie bars is approximately 0.2 mm wide. Such a dimension leaves projections of average length of 0.075 mm. Though, the projections may be of any suitable dimension, such as between about 0.01 mm and 0.15 mm or greater. Moreover, it is not a requirement that the tie bar artifacts have equal-sized projections for opposing edges joined by the tie bar.
In the embodiment illustrated, the compensation portions are projections of about 0.1 mm. Though, the projections may be of any suitable dimensions, such as between 0.05 mm and 0.5 mm. or between 0.07 mm and 0.3 mm. These projections may, in some embodiments may be between 10% and 30% of the nominal width of the signal conductors.
Moreover, it is not a requirement that the compensation portions be the same for all tie bar artifacts. The compensation portions may be of different sizes or shapes.
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.
As one example, examples are illustrated of embodiments in which the artifacts of manufacturing operations severing a tie bar are projections from one or more conductive elements. Other types of artifacts may arise during manufacturing operations, and may similarly be compensated for by compensation portions appropriately sized and positioned. As a specific example, punch a tie bar may, because of tolerances in the manufacturing operation, remove some of one or more of the conductive elements joined by the tie bar as part of a step of removing the tie bar. In such an embodiment, the compensation portion may be an offsetting projection along an edge of the conductive element in proximity to the edge containing the artifact.
Also, embodiments were described in which the intermediate portions of conductive members were fully encapsulated within one housing portion. In other embodiments, the intermediate portions of the conductive elements may be partially held within the insulative housing.
As another example, frequencies in the range of 10-25 GHz was provided as an example of an operating range. However, it should be appreciated that other ranges may be used and that those ranges may span higher or lower frequencies, such as up to 30, 35 or 40 GHz, or may end at lower frequencies, such as 20, or 15 GHz.
Further, in some embodiments, to further ensure a uniform impedance along the length of a signal conductor, the holes in the housing through which a punch or other tool passes to sever the tie bar may be filled with an insulative member.
As for other possible variations, examples of techniques for modifying characteristics of an electrical connector were described. These techniques may be used alone or in any suitable combination.
Further, although 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 of possible variations, connectors with four differential signal pairs in a column were described. However, connectors with any desired number of signal conductors may be used.
This invention is not limited in its application to the details of construction and the arrangement of components set forth in the above 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.
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.
This application is a continuation of and claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 14/209,142, entitled “LEAD FRAME FOR A HIGH SPEED ELECTRICAL CONNECTOR,” filed Mar. 13, 2014; which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/779,444, entitled “LEAD FRAME FOR A HIGH SPEED ELECTRICAL CONNECTOR,” filed Mar. 13, 2013, each of which applications are incorporated herein by reference in their entirety.
Number | Date | Country | |
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61779444 | Mar 2013 | US |
Number | Date | Country | |
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Parent | 14209142 | Mar 2014 | US |
Child | 15276586 | US |