Patent Application
20110021083
An electrical connector may include a plurality of leadframe assemblies disposed adjacent to one another in a connector housing. The connector may have a mounting interface that defines a first plane and mating interface that defines a second plane. Where the plane of the mating interface is orthogonal to the plane of the mounting interface, the connector may be referred to as a right-angle connector. Where the plane of the mating interface is parallel to the plane of the mounting interface, the connector may be referred to as a mezzanine connector.
Each such leadframe assembly may include a leadframe housing, which may be made of a dielectric material, such as a plastic, for example. A plurality of electrical contacts may extend through the leadframe housing. The contacts may be made of an electrically conductive material. The contacts may be stamped from a sheet of electrically-conductive material to form a leadframe. The leadframe housing may be overmolded onto the leadframe. Such a leadframe assembly may be referred to as an insert-molded leadframe assembly (IMLA).
Each contact may have a mating end, which may be a receptacle, blade, or other desirable mating end. Each contact may have a respective mounting end, which may be an eye-of-the-needle type mounting end, or a pin, ball, or other desirable mounting end, or terminate in a fusible mounting element, such as a solder ball, for example.
The mating ends of the contacts within a leadframe assembly may form a linear array extending along a first direction. The mating ends of the contacts may be arranged along a common centerline that extends along the first direction. The mounting ends of the contacts may form a linear array extending along a second direction, which may be parallel to the first direction (in the case of a mezzanine connector) or perpendicular to the first direction (in the case of a right angle connector). The mounting ends of the contacts may align along a common centerline that extends along the second direction.
Differential signal pairs of electrical contacts may be arranged edge to edge (i.e., edge-coupled) or broadside-to-broadside (i.e., broadside-coupled). Contacts may be arranged in a signal-signal-ground arrangement along either columns or rows.
A differential signal pair has a differential impedance between the positive conductor and negative conductor of the differential signal pair. Differential impedance is defined as the impedance existing between two signal conductors of the same differential signal pair, at a particular point along the length of the differential signal pair. It is desirable to control the differential impedance to match the impedance of the electrical device(s) to which the connector is connected. Matching the differential impedance to the impedance of electrical device minimizes signal reflection and/or system resonance that can limit overall system bandwidth. Furthermore, it is desirable to control the differential impedance such that it is substantially constant along the length of the differential signal pair, i.e., such that each differential signal pair has a substantially consistent differential impedance profile.
The differential impedance profile can be controlled by the positioning of the signal and ground contacts. Specifically, differential impedance may be determined by the proximity of the signal contact to an adjacent ground contact, and by the gap between edges of signal contacts within a differential signal pair.
To maintain acceptable differential impedance control for high bandwidth systems, it is desirable to control the gap between contacts to within a few thousandths of an inch. Gap variations beyond a few thousandths of an inch may cause an unacceptable variation in the impedance profile; however, the acceptable variation is dependent on the speed desired, the error rate acceptable, and other design factors.
In addition to conductor placement, differential impedance may be affected by the dielectric properties of material proximate to the conductors. Generally, it is desirable to have materials having very low dielectric constants adjacent and in contact with as much of the conductors as possible. The use of air rather than plastic as a dielectric provides a number of benefits.
Additional background may be found in U.S. Pat. No. 7,270,574, U.S. Pat. No. 6,994,569, and U.S. Patent Application Ser. No. 61/141,990, filed Dec. 31, 2008, the disclosure of each of which is incorporated herein by reference.
As disclosed herein, an electrical connector may include a plurality of electrical contacts arranged into rows and columns. An edge-coupled differential signal pair of the contacts may provide a first pre-established differential impedance, while a broadside-coupled differential signal pair of the contacts may provide a second pre-established differential impedance, which may be different from the first pre-established differential impedance. Accordingly, a single connector may be designed to provide an 85±10 Ω differential impedance when wired for edge-coupled pairs and a 100±10 Ω differential impedance when wired for broadside-coupled pairs.
As used herein, the term “pre-established differential impedance” refers to a differential impedance that is designed into the connector, as distinct from a differential impedance that exists merely as a fallout of the design. In other words, the connector is designed to provide two specific differential impedances that are known a priori, as distinct from prior art connectors that are designed to provide one pre-established differential impedance, while the other is not designed into the connector, but rather merely a fallout of design.
The first and second contacts 28, 30 may define an edge-coupled differential signal pair 29 having a first pre-established differential impedance Z1. The first and third contacts 28, 32 may define a broadside-coupled differential signal pair 31 having a second pre-established differential impedance Z2 that is different from the first pre-established differential impedance Z1. For example, the first pre-established differential impedance Z1 may be 85 ohms, while the second pre-established differential impedance is 100 ohms Z2.
As used herein, a stated differential impedance value refers to the stated value plus or minus 10% tolerance for that value. For example, the stated value “100 Ω” refers to 100 Ω±10%, or 90-110 Ω. Similarly, the stated value “85 Ω” refers to 85 Ω±10%, or 76.5-93.5 Ω.
The gap width g and column pitch p may be chosen such that the first and second electrical contacts 28, 30 provide the first pre-established differential impedance Z1, while the first and third electrical contacts 28, 32 provide the second pre-established differential impedance Z2. In other words, the connector may be designed to have a gap width g and column pitch p that cooperate to provide two pre-established differential impedances Z1, Z2 in a single connector. That is, the first and second electrical contacts 28, 30 may be separated by a first distance along the first direction, and the first and third electrical contacts 28, 32 may be separated by a second distance along the second direction, such that the first and second electrical contacts 28, 32 provide a first pre-established differential impedance Z1 and the first and third contacts provide a second pre-established differential impedance Z2. Thus, the contacts may be positioned relative to one another such that the first and second pre-established differential impedances Z1, Z2 provided are provided as a result of the arrangement.
It should be understood that a contact arrangement such as shown herein may include both edge-coupled and broadside-coupled differential signal pairs 29, 31. Thus, the same connector 12 may simultaneously provide both of two pre-established differential impedances Z1, Z2.
As shown in
As shown in
The substrate 36 may be wired such that a certain two of the electrically conductive elements 38 form a differential signal pair. A connector 12 having a square grid footprint (of solder balls or compliant terminal ends, for example), may be set on the substrate 36 in a first orientation, as shown in
As described above, an electrical connector 12 may be provided by pre-establishing two desired differential impedances Z1, Z2, and then designing the connector 12 such that an edge-coupled differential signal pair 29 provides the first of the two differential impedances Z1, while a broadside-coupled differential signal pair 31 in the same connector 12 provides the second of the two differential impedances Z2.
In an example embodiment, the contacts 22 may be arranged in a square grid, with a column pitch of 1.4 mm and row pitch of 1.4 mm. The contacts may be 0.35 mm thick (i.e., have 0.35 mm edges) and 1.0 mm wide (i.e., have 1.0 mm broadsides). Thus, the gap width between adjacent contacts in a column maybe 0.4 mm, and the distance between broadsides of adjacent contacts in a row may be 1.05 mm. A dielectric material having a thickness of 0.8 mm may be disposed between the columns, i.e., between the broadsides of adjacent contacts. Thus, the dielectric may be spaced 0.125 mm from the broadsides of the contacts.
In such a connector 12, where the contacts 22 along a column were arranged in a ground-signal-signal-ground arrangement, the differential impedance Z1 of an edge-coupled differential signal pair 29 was found to be 82-83 Ω. In the same connector 12, where the contacts 22 along a row were arranged in a ground-signal-signal-ground arrangement, the differential impedance Z2 of a broadside-coupled differential signal pair 31 was found to be 98-99 Ω.
This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/228,269 filed on Jul. 24, 2009, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.
| Number | Date | Country | |
|---|---|---|---|
| 61228269 | Jul 2009 | US |
