Electrical connectors – Electromagnetic or electrostatic shield – Shielding individually surrounding or interposed between...
Reexamination Certificate
2001-09-07
2003-02-25
Feild, Lynn D. (Department: 2839)
Electrical connectors
Electromagnetic or electrostatic shield
Shielding individually surrounding or interposed between...
Reexamination Certificate
active
06524134
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electronic connector systems and, more specifically, to low-profile connector systems for pluggable electronic modules, such as transceiver modules for high speed fiber optical communications.
BACKGROUND OF INVENTION
Historically, electrical and opto-electric modules have been connected to printed circuit boards with solder pins. Conventional approaches for soldering the pins to the circuit board include reflow soldering and hand soldering. Although solder reflow is an effective technique for electrically connecting a module to a circuit board, the heat required to achieve reflow tends to be detrimental to heat sensitive components within the module, such as plastic optical components which tend to warp or otherwise distort at high temperatures. Furthermore, to ensure that modules are capable of withstanding the environmental conditions associated with reflow soldering, the industry utilizes high temperature materials that add cost to the modules. Since most modules will be used in more moderate climates (e.g., an air-conditioned office building), the modules are therefore “over-engineered” simply to ensure that they can withstand the reflow soldering process.
To avoid exposing the module to harsh conditions during reflow soldering, often electronic modules are hand soldered instead to a printed circuit board. The need for hand soldering, however, dramatically increases the cost of system comprising such modules.
Aside from the problems associated with soldering the module to the circuit board, there is the added inconvenience that, if a single module fails on a circuit board, which may support many such modules, the entire circuit board must be removed for service.
Therefore, there is a need for a solderless connection of a module to a circuit board. To this end, several pluggable module designs and standards have been introduced in which a pluggable module plugs into a receptacle which is electronically connected to a host circuit board. For example, a well-known type of transceiver developed by an industry consortium is known as a gigabit interface converter (GBIC) or serial optical converter (SOC) and provides an interface between a computer and a data communication network such as Ethernet or Fibre Channel. These standards offer a generally robust design which has been well received in industry.
Although these conventional pluggable designs have been used successfully in the past, they tend to be unsuitable for miniaturization which is an ever-constant objective in the industry. It is desirable to miniaturize transceivers in order to increase the port density associated with the network connection, such as, for example, switch boxes, cabling patch panels, wiring closets, and computer I/O. Recently, a new standard has been promulgated and is referred to herein as the small form factor (SFF) standard which specifies an enclosure height of 9.8 mm and a width of 13.5 mm and a minimum of 20 electrical input/output connections. In addition to miniaturizing the module, it is also desirable to increase its operating frequency. For example, applications are quickly moving from the sub-gigabit realm to well over a gigabit. Conventional pluggable module configurations, however, cannot meet these parameters.
Miniaturizing a module while maintaining or even increasing its operating speed, presents a number of design problems particularly in applications in which data transmission rates are high, e.g., in the range of 1-10 Gbs (Gigabits/second). Of particular concern is reducing electromagnetic interference (EMI) emissions. Due to FCC regulations, there is a need not only to minimize the EMI emissions of the module, but also to contain the EMI emissions of the host system in which the module is mounted regardless of whether a module is plugged in to the receptacle. In conventional designs, this EMI shielding was achieved by using conductive spring-loaded door which was capable of swinging shut and closing the receptacle when the module was removed. Conventional receptacles also had spring clips to ground the receptacles to the opening or “bezel opening” of the host system through which the receptacle protrudes. Providing space for spring-loaded doors and spring clips on the receptacle tends to be problematic if not impossible in miniaturized configurations. Additionally, the small size presents problems in dissipating heat from the module and incorporating traditional mechanisms for ejecting and retaining the module and for electrically connecting the module to the host circuit board.
It has also been found that providing solutions for the aforementioned EMI and miniaturization problems is further complicated by the dimensional various in the industry with respect to bezel opening position vis-a-vis the host circuit board. While many applications require that the bottom of the bezel opening be flush with the top of the circuit board, some applications require that the bezel opening be raised from the top of the host circuit board. For example, the PCI Local Bus Specification, Revision 2.2 specifies that the bottom of the bezel opening must be 0.4±0.1 min above the host circuit board. As used herein, the distance between the bottom of the bezel opening and the top of the host circuit board is refereed to as the “bezel opening offset.” To function properly, a suitable receptacle must be able to accommodate this bezel opening offset while also addressing the EMI and miniaturization concerns mentioned above.
Therefore, there is a need for a versatile module design that conforms to the various dimensional standards, while minimizing EMI emissions and providing convenient pluggable operation. The present invention fulfills this need among others.
SUMMARY OF INVENTION
The present invention provides for a pluggable module and receptacle system that facilitates miniaturization and high operating frequencies by effectively shielding EMI emissions to eliminate leaks and conduct EMI to ground, and by synergistically using components to eliminate conventional discrete mechanisms and their attendant bulk. The present invention also provides for a module and receptacle system which is versatile and able to accommodate a variety of dimensional requirements and bezel opening offsets without comprising the EMI shielding and without a substantial change in the components used.
EMI shielding is achieved by implementing one or more features that serve to minimize gaps through which EMI can escape, and/or to enhance grounding of the receptacle. One such feature is a receptacle housing in which all of its sides except the front comprise conductive walls for blocking EMI. This way, when the receptacle is mounted within a host system and is exposed to the host system's internal EMI, all of the housing sides exposed to the EMI, including the back and the bottom, are conductive and thus suitable for conducting the EMI to ground. Preferably, the housing is electrically connected to ground through a number of elongated members. Another feature for minimizing gaps through which EMI can escape is the use of containment members. Containment members extend downward from the receptacle, preferably between elongated members, and essentially form a picket fence along with the elongated members to prevent EMI emissions.
In addition to minimizing gaps through which EMI can escape, the module and receptacle system of the present invention is extremely well suited for conducting EMI to ground. This grounding is achieved principally by grounding contacts on the front end of the module and grounding tabs around the front opening on the receptacle. This way, the grounding contacts provide a grounding path from the module to the receptacle and the grounding tabs, in turn, provide a grounding path from the receptacle to the host chassis. Preferably, the grounding tabs are cut from the receptacle housing walls and elongated such that the grounding tabs are longer than the respective section of the wall from which each grounding tab was derived. Such a c
Bright Edward J.
Flickinger Steven L.
Herb William
Kemmick Dennis L.
Kerlin Harold W.
Dinh Phuong K T
Feild Lynn D.
Tyco Electronics Corporation
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