EP2747216A1

EP2747216A1 - Connector with improved ESD protection

Info

Publication number: EP2747216A1
Application number: EP12306668.0A
Authority: EP
Inventors: Hans-Joachim Goetz; Rainer Haberditzl; Reinhold Seitz
Original assignee: Alcatel Lucent SAS
Current assignee: Alcatel Lucent SAS
Priority date: 2012-12-24
Filing date: 2012-12-24
Publication date: 2014-06-25

Abstract

An apparatus, comprising an electrical connector comprising a main body of non-electrically conductive material; one or more sets of metallic strips physically attached to the main body and extending from a mounting edge of said main body to a coupling edge of said main body; and one or more conductive polymer patches, one of the one or more conductive polymer patches being located on the main body and being in physical contact with the metallic strips of one of the one or more sets.

Description

Field of the Invention

The present invention relates to the field of electronic connectors and backplane connectors.

Background

Electrostatic discharge (ESD) may occur in situations where a material is susceptible to a build-up of electrical charge, and where the material is later brought in contact with a material that is differently charged. ESD is a well known concern in the field of electronics, in particular micro-electronics, because many electronic components are very sensitive to such discharges, to the extent that they may be fatally damaged if they are subjected to a discharge.
Electrostatic discharge may damage component(s) through which such electrical charges are discharged. Afterwards, it is often difficult to identify the source of any resulting problems, because the discharge itself often goes unnoticed by the human operator, and the damage may only gradually manifest itself over time.

Summary

It is an object of various embodiments to provide a connector that at least partially overcomes the problems associated with ESD.
According to some embodiments, an apparatus comprises an electrical connector comprising: a main body of non-electrically conductive material; one or more sets of metallic strips physically attached to the main body and extending from a mounting edge of the main body to a coupling edge of the main body; and one or more conductive polymer patches, one of the one or more conductive polymer patches being located on the main body and being in physical contact with the metallic strips of one of the one or more sets.
Throughout this application, the "mounting edge" is understood to be the side of the connector by which it is intended to be mounted, i.e. mechanically and electrically connected, to a substrate such as a printed circuit board, e.g. by soldering. For this purpose, the mounting edge may be provided with appropriate pins, balls, pads, or other suitably conductive elements that, when the connector is mounted, form a conductive path from the conductors in the connector towards other elements mounted on the substrate. Throughout this application, the "coupling edge" is understood to be the side of the connector by which it is intended to be coupled to an associated connector, for instance an associated connector mounted on another substrate, in order to provide a conductive path towards other elements.
According to some embodiments, a connector has a mounting edge and a coupling edge, the connector comprising a main body and at least one set of metallic strips running from the mounting edge to the coupling edge, each set of metallic strips comprising multiple lines, the connector comprising a conductive polymer patch arranged to form a conductive path between the metallic strips of one of the sets of metallic strips.
According to some embodiments, the patch forms a path that is able to discharge charges between the metal strips without shorting the strips of the set together with respect to signals of high speed links.
In some embodiments, the connector comprises a plurality of sets of metallic strips and conductive polymer patches, each separate patch being arranged to form a conductive path between the metallic strips of a corresponding one of the sets.
The above embodiment may offer an advantage of eliminating accumulated electrical charge without increasing crosstalk between transmission lines carried by the connector.
In another embodiment, the connector comprises a plurality of sets of metallic strips, the conductive polymer patch being arranged to form a conductive path across the metallic strips of the plurality of sets.
The above embodiment may offer the advantage of eliminating accumulated electrical charge with a connector that is relatively easy to manufacture. For example, some such embodiments use one additional patch, which may be within a single cavity moulded in the housing.
In some embodiments of the above connectors, each of the patches forms electrical shunt paths between the strips of one of the one or more sets, each of the shunt paths having a resistance in the range of 10 kΩ to 10 MΩ.
In such embodiments, the resistance may be low enough to safely discharge any built-up charge and may be high enough to not significantly change the impedance of the signal trace.
According to other embodiments, there is provided a printed circuit board comprising a connector mounted thereon. The connector is as already described.
According to another embodiment, there is provided a multi-board system comprising a backplane having a plurality of complementary connectors, and at least one printed circuit board as described above. The printed circuit board is coupled to at least one of the plurality of complementary connectors by its own connector.
Technical effects and advantages of the above-described printed circuit boards and the multi-board systems may include the technical effects of the embodiments of the connector therein.

Brief Description of the Figures

Some embodiments of apparatus and/or methods in accordance with various embodiments are now described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 schematically illustrates a connector according to a first embodiment;
Figure 2 schematically illustrates a connector according to a second embodiment;
Figure 3 schematically illustrates a printed circuit board comprising a connector according to an embodiment; and
Figure 4 schematically illustrates a multi-board system comprising a backplane having a plurality of complementary connectors.

Description of Illustrative Embodiments

The problem of ESD may occur in multi-board systems. In particular, ESD(s) may occur when daughterboard(s) are interconnected via connector(s) to a backplane. The issue of ESD is becoming more important as semiconductor structures shrink and become more vulnerable to ESD.
In the present application, the term "high-speed link" generally designates a link supporting a digital data transmission speed of at least 1 Gigabit per second (Gb/s). Examples of such links are Gigabit Ethernet (1 Gb/s), 10 Gigabit Ethernet (10 Gb/s), and fractions thereof (2.5 Gb/s; 5 Gb/s; 7.5 Gb/s). Links with transmissions speeds of 40 Gb/s and 100 Gb/s are also high- speed links, as are future types of links that reach transmission speeds above 100 G/s. Some examples of the links may operate according to the relevant parts of the IEEE 802.3 standard or any other appropriate standard.
For high speed links, such as those used in some backplanes to connect inserted daughter boards, coupling capacitors (also referred to as "coupling caps") have often been used to avoid DC coupling. These capacitors are in series with interface devices on the respective boards.
During the handling process of a circuit pack, these capacitors can unintentionally become electrical charged, and such charging leads to risks of ESD damage. When a board having capacitors thus charged is later plugged into a system and connected to a link, the coupling caps can be discharged by the device on the other end of the link. Such a discharge can lead to destruction of devices on both ends of the link by the discharging currents from terminals or leads of the coupling caps.
Providing resistors that are connected from the open end of the capacitors to ground, in order to allow selective discharge, may have the disadvantage of creating additional impedance loads to the signal streams. The modification of the load to signal streams may negatively affect the quality of the signals transmitted over the link (in particular, one or more of bandwidth, amplitude, return loss, and cross-talk may be negatively affected).
In various embodiments, the negative impact of such resistors on the transmission quality of the link can be avoided by giving the connector a role in the controlled discharge of electrostatic charges.
This can be achieved, if such a connector includes dissipative material in contact with multiple metal coupling strips on the connector. If an electrostatic charge discharges through one of said strips and the dissipative material shunts said one of the strips to a strip connected to ground during the connection process, the charge may be dissipated from the one of the strips to ground via the dissipative material.
In such embodiments, the dissipative material typically has a shunt resistance that is low enough to safely discharge any built-up charges and is high enough not to change the impedance of the signal trace. The shunt resistance is preferably in the range of 10 kΩ to 10 MΩ. But, values outside this range may also be used, depending on the application.
According to some embodiments, the dissipative material is a conductive polymer shunt. Such a shunt may be easily molded and have a conductivity appropriated to safely shunt such electrostatic charges to a metal strip connected to ground.
Figures 1 and 2 illustrate one example of a connector (110). The connector (110) has a mounting side (120), allowing the connector (110) to be mounted to e.g. a printed circuit board, and a coupling side (160), allowing the connector (110) to be mounted to a complementary connector. The connector (110) comprises a main body (130) or wafer, which may be, e.g., made of a resin. The connector (110) further comprises one or more sets of metallic strips (140) running from the mounting side (120) to the coupling side (160). These strips may be, e.g., arranged in suitable cavities moulded into the wafer.
The connector (110) also comprises at least one conductive polymer patch (150) arranged to form a conductive path between the metallic strips (140) of a corresponding one of the sets. These patches may be arranged in suitable cavities moulded into the wafer or may be otherwise positioned.
If one of the metallic strips (140) of a set connects to a ground during positioning of the connector, the patch can act as an electrical shunt for discharging electrostatic charges from other strip(s) of the same set. Such a connection of the metallic strips is common when the set includes a differential pair that forms a transmission line.
The connector may include decoupling capacitors arranged serially within the various lines, between the mounting side and the coupling side, in order to provide DC decoupling. Alternatively, these decoupling caps may be provided on the printed circuit board onto which the connector is mounted.
Figure 1 schematically illustrates a connector according to a first embodiment.
In the first embodiment, the connector (110) comprises a plurality of sets of metallic strips (140). Without loss of generality, four sets of strips are shown in the illustrated example. The at least one conductive polymer patch (150) comprises a separate conductive polymer patch for each of the sets. Each separate patch is physically in contact with the metallic strips of the corresponding one of the sets, and is thus arranged to form a conductive path between the strips (140) within that set. The strips belonging to different sets are not interconnected by the patches in this embodiment.
Figure 2 schematically illustrates a connector according to a second embodiment.
In the second embodiment, the connector (110) comprises a plurality of sets of metallic strips (140). Without loss of generality, four sets of strips are shown in the illustrated example. In this embodiment, the at least one conductive polymer patch (150) is a single contiguous conductive polymer patch that is in contact with the metallic strips of the various sets. Thus, the patch is arranged to form a conductive path across the metallic strips (140) of the various sets.
The connectors may be mounted on a printed circuit board (100). An exemplary printed circuit board (100) is shown in Figure 3. Such a printed circuit board (100) may serve as a daughter board for a larger electronic system. This board (100) will typically carry an electronic circuit including multiple electronic components; for clarity reasons, only a single exemplary component (170) is shown in the Figure. A multi-board system according to an embodiment comprises a backplane (200) having a plurality of connectors that are complementary to those mounted on the daughter boards. An exemplary system is shown in Figure 4. Without loss of generality, the illustrated backplane (200) has two associated connectors (210), which are shown in a highly simplified form. In such embodiments, least one of the printed circuit boards (100) is physically and electrically coupled to at least one of the complementary connectors (210) by a connector (110) - for clarity reasons, the printed circuit boards (100) are illustrated in a position with their connectors (110) near the associated complementary connectors (210).
Various embodiments may be useful in high-speed telecommunications, data communications, and computing applications. Embodiments of the multi-board system may for example and without limitation include an access node, a telephony switch, a data switch, a router, a personal computer, a server, and a data storage node.
Although the invention has been described hereinabove with respect to illustrative embodiments, the above description was provided for illustrative purposes and was not provided to limit the inventions claimed. The scope of various inventions are determined by the specific recitations of the various claims.

Claims

An apparatus, comprising:
an electrical connector comprising:
a main body of non-electrically conductive material;

one or more sets of metallic strips physically attached to the main body and extending from a mounting edge of said main body to a coupling edge of said main body; and

one or more conductive polymer patches, one of the one or more conductive polymer patches being located on the main body and being in physical contact with the metallic strips of one of the one or more sets.
The apparatus according to claim 1,
wherein the one or more sets comprises a plurality of the sets; and
wherein each of the conductive polymer patches is in physical contact with the metallic strips of a corresponding one of the one or more sets.
The apparatus according to claim 1, wherein the one or more conductive polymer patches is a single contiguous conductive polymer patch in contact with the strips of each of the sets.
The apparatus according to any of the preceding claims, wherein each of said patches forms electrical shunt paths between the strips of one of the one or more sets, each of the shunt paths having a resistance in the range of 10 kΩ to 10 MΩ.
The apparatus of any of the preceding claims, further comprising a printed circuit board, wherein the connector is electrically and physically connected to the printed circuit board by one of the edges.
The apparatus of any of the preceding claims, further comprising a multi-board system comprising a backplane having a plurality of complementary connectors, and at least one printed circuit board according to claim 5 coupled to at least one of said plurality of complementary connectors by the connector.