Electrical connectors – Electromagnetic or electrostatic shield – Shielding individually surrounding or interposed between...
Reexamination Certificate
2000-12-01
2003-02-11
Patel, Tulsidas (Department: 2839)
Electrical connectors
Electromagnetic or electrostatic shield
Shielding individually surrounding or interposed between...
C439S439000
Reexamination Certificate
active
06517382
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 and copper 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 bezel opening of the host system. 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.
Therefore, there is a need for a module design that conforms to the SFF standard while minimizing EMI emissions and providing convenient pluggable operation. The present invention fulfills this need among others.
SUMMARY OF INVENTION
The present invention provides 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.
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 configuration prevents the grounding tabs from being deflected into the receptacle cavity. This arrangement is particularly preferable in small form factor configurations in which there is no room in the receptacle cavity to accommodate anything other than the module. To enhance the grounding of the module to the receptacle while the module is being inserted therein, the receptacle housing defines rows of ventilation holes, which, in turn, define uninterrupted ground paths therebetween. By spacing the grounding contacts on the module to correspond to the spacing of the grounding paths on the receptacle, the grounding contacts will slide along the grounding paths during insertion and withdrawal of the module from the receptacle, thereby ensuring that the module is continuously grounded during the insertion and withdrawal. Further enhancements to grounding include a latch which serves not only to retain the module within the receptacle, but also to provide a grounding path from the front of the module to the front of the receptacle and to provide an extra picket in the EMI fence as mentioned above.
The module and receptacle system of the present invention also employs components of the receptacle synergistically to avoid separate mechanisms and components which add bulk an
Bright Edward J.
Flickinger Steven L.
Herb William L.
Kemmick Dennis L.
Kerlin Harold W.
Dinh Phuong
Patel Tulsidas
Tyco Electronics Corporation
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