Abstract:
A system includes a circuit board, a modular connector and an EMI shield. The circuit board includes a groundplane and a groundpad that is electrically coupled to the groundplane. The EMI shield includes a first portion to contact and establish an electrically connection with the modular connector. Another portion of the EMI shield contacts the groundpad to electrically couple the first portion to the groundpad to shunt EMI from the modular connector.

Description:
This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/159,232, entitled “EMI SHIELD,” filed on Oct. 13, 1999. 
    
    
     BACKGROUND 
     The invention relates to an Electromagnetic Induction (EMI) shield. 
     EMI poses a serious design challenge to network component design, particularly as supported data throughput rates meet and exceed those specified by the well-known Fast Ethernet (100 Mb/s) and Gigabit Ethernet (1000 Mb/s) standards. EMI is especially problematic where, as a cost-savings effort, “unshielded” cabling and connectors are used to communicate signals that indicate information for high speed local area network (LAN) traffic. 
     Due to the signal distortion that EMI introduces, EMI can cause data loss within and about the network component exhibiting the same, and can interfere with or otherwise adversely affect the operation of other electronic devices adjacent thereto. Accordingly, the FCC of the United States, for example, has promulgated a FCC part 15 subpart A, class A standard that defines the maximum acceptable radiated EMI emissions for electronic devices falling under class A classification. Compliance with this or a similar standard such as the CISPR 22 class A standard, meaning that exhibited EMI emissions for a given electronic device such as a network component will not exceed the defined class A threshold, is desirable in order to maximize potential placement and use of the subject network component within a network, and therefore, maximize its flexibility and value to potential customers. In the past, such network components have incorporated conventional shielded connections to keep radiated EMI to a minimum to comply to these standards. 
     However, as alluded to above, cost considerations have forced network component designers to forgo shielded connections where possible to keep their components price competitive and compatible with the broadcast array of connection and interfacing gear. Therefore, alternative ways of reducing EMI must be explored. 
     SUMMARY 
     In general, according to one embodiment of the invention, a conductive shield includes a first portion to contact and establish an electrical connection with a modular connector and a second portion. The second portion electrically couples the first portion to communicate with ground of a circuit board to shunt EMI from the modular connector. 
     In general, according to another embodiment of the invention, a system includes a circuit board, a modular connector and an EMI shield. The circuit board includes a groundplane and a groundpad that is electrically coupled to the groundplane. The EMI shield includes a first portion to contact and establish an electrical connection with the modular connector. Another portion of the EMI shield contacts the groundpad to electrically couple the first portion to the groundpad to shunt EMI from the modular connector. 
     The advantages of the above-described arrangements may include one or more of the following. These arrangements may provide a cost effective way to shield EMI from a modular connector, such as a network connector, for example. These arrangements may facilitate assembly of modular connectors onto circuit boards. EMI emissions may be reduced. Assembly time may be minimized. 
     Other features and advantages will become apparent from the following description, from the drawings and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a top view of an EMI shield according to an embodiment of the invention. 
     FIG. 2 depicts a cross-sectional view of the EMI shield taken along line  2 — 2  of FIG.  1 . 
     FIG. 3 is an exploded perspective view of an assembly that includes the shield and a connector according to an embodiment of the invention. 
     FIG. 4 is a cross-sectional view of the EMI shield and connector assembly taken along line  4 — 4  of FIG.  3 . 
     FIG. 5 is a front view of the EMI shield according to an embodiment of the invention. 
     FIG. 6 is a cross-sectional view of the EMI shield taken along line  6 — 6  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1 and 3, an embodiment  100  of an EMI shield in accordance with the invention includes features to facilitate the mounting of a modular connector  200  to a printed circuit board  250  and establish electrical contact between a conductive outer surface of the connector  200  and circuitry of the printed circuit board  250  for purposes of reducing EMI emissions from the connector  200 . In this manner, the EMI shield  100  may be located along an edge  203  of the printed circuit board  250  and may be designed to temporarily mount the connector  200  to the printed circuit board  250  before wavesoldering is performed to solder electrical pins of the connector  200  to the printed circuit board  250 . In addition to serving as an aid to attach the connector  200  to the printed circuit board  250 , the EMI shield  100  may also be used to electrically couple the connector  200  to circuitry of the printed circuit board  250 . For example, the EMI shield  100  may couple the connector  200  to ground (digital ground, for example) of the printed circuit board  250  for purposes of shunting EMI from the connector  200 . 
     More particularly, referring also to a cross-sectional view of the connector  200  and EMI shield  100  assembly that is depicted in FIG. 4, in some embodiments of the invention, the EMI shield  100  forms an angled clip-type connection for receiving an edge  216  of the connector  200 . In this manner, a surface  131  of the EMI shield  100  contacts a corresponding conductive surface  209  of the connector  200  to both hold the connector  200  to the printed circuit board  250  and establish electrical connection with an outer housing of the connector  200 . The connector  200  is held to the printed circuit board  250  due to the lateral force that is exerted by the EMI shield  100  on the pins (of the connector  200 ) that extend through vias  420  (see FIG. 3) of the printed circuit board  250   
     The surface  131  is the underlying surface of a portion  120  (of the EMI shield  100 ) that is parallel to the edge  203  of the printed circuit board  250  and is connected to circuit board tabs  110  (see FIG. 1) of the EMI shield  100  via upstanding members  180 , as depicted in a cross-section of the shield  100  in FIG.  2 . As described further below, the tabs  110  both support the EMI shield  100  on the printed circuit board  250  and electrically connect the EMI shield  100  to the printed circuit board  250 . 
     Referring to FIGS. 2 and 4, the upstanding members  180  and the overhanging portion  120  form acute angles to receive the edge  216  of the connector  200 . Due to this arrangement, when the connector  200  is inserted into the EMI shield  100 , the portion  120  is flexed into position to form an approximate ninety degree angle channel with the upstanding members  180  to receive the edge  216 . Due to the resiliency of the material that forms the EMI shield  100 , when the connector  200  is inserted into the EMI shield  100 , the portion  120  deflects to conform to the surface  209 , as depicted in FIG.  4 . In this manner, when the EMI shield  100  receives the connector  200 , the upstanding members  180  contact an upstanding face  211  (of the connector  200 ) that is generally orthogonal to the printed circuit board  200 , and the overhanging portion  120  of the EMI shield  100  contacts the surface  209 . Thus, the EMI shield  100  forms a substantially contoured fit with the edge  216 . In some embodiments of the invention, the surface  209  is generally parallel to the printed circuit board  200 , and in some embodiments of the invention, the face  209  is recessed to form a shoulder  220  that abuts an outer edge  130  of the portion  120 . 
     Referring back to FIG. 1, the tabs  110  may be soldered to groundpads  400  of the printed circuit board  250  to establish an electrical connection between the connector  200  and a groundplane of the printed circuit board  250 . As shown, the tabs  110  extend along the surface of the printed circuit board  250  to both electrically connect the EMI shield  100  to circuitry of the printed circuit board  250  and firmly anchor the EMI shield  100  to the printed circuit board  250  after wavesoldering occurs. Due to the design limitations imposed by, for example, the pin-through vias  420  (see FIG. 4) that are used in this embodiment to assist in securing the connector  200  to the circuit board  250  and electrically coupling the signaling traces (not shown) of the circuit board  250  to corresponding signaling pins (not shown) or status lights (not shown) of the connector  200 , the tabs  110  are spaced apart at regular intervals  150  to allow room for the vias  420  that extend in between. In this manner, the groundpads  400  (see FIG. 1) extend between the vias  420  to meet the tabs  110 . It should be appreciated, however, that in accordance with the present invention, the exact number, length and positioning of the tabs  110  is not dispositive as long as a ground path, preferably a substantially non-circuitous conductive path, can be established between the outer surface of the connector  200  and the electrical ground of the printed circuit board  250  to shunt and dissipate EMI otherwise radiating outwardly from the connector  200 . 
     As depicted in FIG. 1, in some embodiments of the invention, the outer edge  130  of the EMI shield  100  is serrated to enhance a friction fit between the EMI shield  100  and the connector  200  and to accommodate variation in the straightness of the shoulder  220  (see FIG.  4 ). In this manner, in some embodiments of the invention, the edge  130  includes extensions  132  that are spaced at regular intervals  140 . Referring to a front view of the EMI shield  100  that is depicted in FIG. 5, in some embodiments of the invention, the bottom surface  131  of the overhanging portion  120  of the EMI shield  100  may also be serrated to accommodate variations in the flatness of the surface  209  of the connector  200  and to enhance a friction fit between the EMI shield  100  and the surface  209 . 
     Referring back to FIG. 1, in some embodiments of the invention, the EMI shield  100  may have features to temporarily hold the EMI shield  100  to the printed circuit board  250  before wavesoldering is used to solder the tabs  110  (and EMI shield  100 ) to the printed circuit board  250 . For example, in some embodiments of the invention, at the longitudinal. ends of the shield  100  are disposed pin-thru stabilizer tabs  160  to secure the shield  100  to the printed circuit board  250  through either compression, friction or solder fitting employing the use of stabilizer pins  170 , as depicted in FIG.  6 . 
     In some embodiments of the invention, the connector  200  may include at least a conductive portion  204  (see FIG. 4) that contacts the EMI shield  100  to form an electrical connection between the connector body and the circuitry of the printed circuit board  250 . As an example, the connector  200  may be an Ethernet modular connector that is available from AMP electronics for use in high-speed 100 BaseT and 1000 BaseT Ethernet connections. As an example, the connector  200  may be a 2×8 connector. 
     As an example, in some embodiments of the invention, the EMI shield  100  may be made from a conductive material. As examples, this conductive material may be tinned aluminum, gold, silver or copper or any other material that is suitable for shunting EMI from the connector  200 . 
     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.