Electrical connectors – With insulation other than conductor sheath – Plural-contact coupling part
Reexamination Certificate
1999-06-01
2001-07-03
Paumen, Gary F. (Department: 2833)
Electrical connectors
With insulation other than conductor sheath
Plural-contact coupling part
C439S060000
Reexamination Certificate
active
06254435
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the art of electrical connectors and, particularly, to a high performance edge card connector for a printed circuit board.
BACKGROUND OF THE INVENTION
A popular type of electrical connector which is used widely in the electronic industry is called an “edge card” connector. An edge card connector receives a printed circuit board or card having a mating edge and a plurality of contact pads adjacent the edge. Such edge card connectors have an elongate housing defining an elongate receptacle or slot for receiving the mating edge of the printed circuit board. A plurality of terminals are spaced along one or both sides of the slot for engaging the contact pads adjacent the mating edge of the board. In most applications, such edge connectors are mounted on a second printed circuit board. The mating edge board or card commonly is called the “daughter” board, and the board to which the connector is mounted commonly is called the “mother” board, a backplane or a base board.
One of the problems with edge card connectors of the character described above centers around the ever-increasing demands for high speed and miniaturized electronic circuitry. The terminals of such a connector are mounted in a housing fabricated of dielectric material such as plastic or the like. Not only are the terminals becoming ever-increasingly miniaturized, but their density within the housing is becoming greater and greater. The terminals are mounted in rows along the slot of the housing with the terminals being separated by dielectric partitions or walls integral with the housing, and the housing includes side walls for surrounding the terminals. Unfortunately, such high density circuitry can result in increased crosstalk and poor impedance control.
For example, microprocessors operate at ever increasing frequencies and communicate with ancillary devices such as memory, display drivers and the like over wide channels with increasing numbers of parallel connections. The interconnection of such high frequency circuitry may be accomplished with connectors having closely spaced terminals, terminals having relatively small cross sectional areas, or both. The requirement for high frequency operation results in the need for a controlled impedance in order to transmit or pass fast digital pulse rise times with minimal distortion. However, close circuit spacing can result in the aforementioned increased crosstalk due to signal-to-signal coupling. The present invention is directed to solving this myriad of problems and particularly to providing a terminal arrangement wherein the signal terminals are provided with controlled signal-to-ground capacitive coupling and shielding along substantially the entire signal paths of the terminals and therefore resulting in controlled inductance and impedance.
SUMMARY OF THE INVENTION
An object, therefore, of the invention is to provide a new and improved edge card electrical connector for receiving an edge of a printed circuit board having contact pads adjacent the edge.
In the exemplary embodiment of the invention, the edge card connector includes an elongated dielectric housing having a board-receiving face. An elongated slot is disposed in the board-receiving face generally along a longitudinal axis of the housing for receiving the edge of the printed circuit board. A plurality of transversely spaced apart terminal-receiving cavities are provided for receiving respective ones of a plurality of first and second terminals engageable with the contact pads of the printed circuit board. The arrangement of cavities defines at least one row of cavities lengthwise of the housing along the slot. The cavities in the row are separated by transverse walls extending generally perpendicular to the longitudinal axis of the housing. A plurality of first and second terminals are received in the plurality of terminal-receiving cavities.
Each of the first terminals includes a base portion having a retention section mounting the terminal in the housing. A resilient spring arm extends from the base portion and terminates in a contact portion that projects into the slot for engaging one of the contact pads on the printed circuit board. An enlarged head portion may be provided at a distal end of the resilient spring arm and extends from the contact portion away from the slot between an adjacent pair of the transverse walls of the housing. A tail portion extends from the base portion for interconnection to circuitry on a circuit member. A shield portion may project downwardly from the base portion spaced from and in the same direction as the tail portion. A mechanically non-functional impedance-matching section may also project from the base portion.
Each of the second terminals includes a base portion having a retention section mounting the terminal in the housing. The base portion and the retention section of the second terminal may be within the longitudinal profile of the base portion and retention section of the first terminal, i.e., in a direction longitudinally of the housing. A resilient spring arm extends from the base portion and terminates in a contact portion at the slot for engaging one of the contact pads on the printed circuit board. The spring arm of the second terminal is preferably within the longitudinal profile of the spring arm of the first terminal. A finger portion or an enlarged head portion may be provided at a distal end of the narrow resilient spring arm and extends from the contact portion away from the slot between an adjacent pair of the transverse walls of the housing. The finger portion or the enlarged head portion of the second terminal is preferably within the longitudinal profile of the enlarged head portion of the first terminal. A tail portion extends from the base portion for interconnection to circuitry on the circuit member. An enlarged support portion may be provided at the juncture of the tail portion and the base portion outside the housing. The support portion of the second terminal is preferably within the longitudinal profile of the shield portion of the first terminal.
As disclosed herein, the resilient spring arm of the first terminal is wider than the resilient spring arm of the second terminal. Each of the first and second terminals is fabricated of stamped sheet metal material.
Substantially the entire second terminal, except for the contact portion, a small section of the retention section and the tail portion thereof, is within the longitudinal profile of the first terminal. This provides for substantial capacitive coupling between the terminals and, if the first terminal is a ground or reference terminal and the second terminal is a signal terminal, the ground terminal substantially shields the signal terminal.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.
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Cheong Kai Mook
McClelland Timothy R.
McGrath James L.
Nelson Richard A.
Panella Augusto P.
Cohen Charles S.
Gushi Ross
Molex Incorporated
Paumen Gary F.
LandOfFree
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