|Publication number||USRE38736 E1|
|Application number||US 10/051,925|
|Publication date||May 17, 2005|
|Filing date||Jan 17, 2002|
|Priority date||Jul 22, 1998|
|Also published as||CN1143416C, CN1242630A, EP0975055A1, US6015299|
|Publication number||051925, 10051925, US RE38736 E1, US RE38736E1, US-E1-RE38736, USRE38736 E1, USRE38736E1|
|Inventors||Alan S. Walse, Harold Keith Lang, Augusto P. Panella, Irvin R. Triner, Shyh-Lin Tung|
|Original Assignee||Molex Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (52), Non-Patent Citations (1), Referenced by (10), Classifications (16), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to electrical connectors for printed circuit boards, and more particularly to an improved card edge connector for removeably connecting a circuit card to a circuit board.
Devices such as computers using printed circuit boards are exhibiting increasing circuit densities and operate at increasing frequencies. For example, the speed of high frequency digital signals traveling between a computer motherboard and densely populated memory module printed circuit cards on an associated circuit board are becoming higher. These trends create problems for electrical connectors such as edge card connectors that are used to removeably mount a circuit card on a circuit board.
With increasing circuit density, the electrical connectors and the electrical terminals they include are smaller. The terminals must nevertheless be sufficiently flexible and strong to provide reliable contact with a circuit card inserted into the connector.
In addition, it is desirable to keep small the impedance of the circuit paths provided by the electrical terminals of the edge card connector. Meanwhile, inductance must be kept to a minimum, capacitance must be carefully controlled, and crosstalk between different signals must be minimized. These often conflicting goals have led to many approaches for connector and terminal design with varying degrees of success.
U.S. Pat. No. 5,161,987, for example, discloses an electrical connector having a ground bus with a plurality of solder tails. A row of signal contacts is located on each side of the ground bus.
U.S. Pat. No. 5,162,002, meanwhile, discloses a card edge connector with spatially overlapped terminals having relatively shorter and relatively longer contact elements.
This connector has important advantages such as reducing the peak card insertion force, but has electrical characteristics that are not optimized for higher speed digital signals.
U.S. Pat. No. 5,192,220 discloses a dual readout socket wherein crosstalk is reduced by increasing the space between connectors. This approach defeats the goal of increased circuit density.
U.S. Pat. No. 5,259,768 discloses an electrical connector having ground terminals with significantly larger surface areas than the signal terminals. The ground and signal terminals alternate, and the shadowing effect of the ground terminals reduces crosstalk. The ground terminals have both solder tails and grounding feet to reduce impedance generally, while non-functional stubs are sized to provide a specifically desired impedance.
U.S. Pat. No. 5,259,793 discloses an edge connector with terminals arranged in an alternating array along the circuit card insertion slot. Circuit density is diminished because of the alternating array.
U.S. Pat. No. 5,309,630 discloses an electrical connector wherein a desired impedance is obtained by selecting terminals having anchoring portions sized to correspond to the desired impedance. Signal and ground terminals may alternate, and at least the ground terminals are provided with two feet to reduce impedance.
U.S. Pat. No. 5,580,257 discloses a connector in which enlarged ground terminals are adjacent to pairs of signal terminals to reduce crosstalk. Although this arrangement has advantages, three different terminal shapes are required, and the operation of assembling terminals into the connector housing is complex.
Despite these and many other attempts, there remains a long-standing need for a card edge connector that can be made at reasonable cost, is robust and reliable, has high circuit density and performs well in high speed digital circuits.
An object of the present invention is to provide an improved card edge connector. Other objects are to provide a connector with low inductance that can achieve an impedance match with associated circuit assemblies; to provide a connector having minimum cross talk between signal circuits; to provide a connector having high circuit density; to provide a connector that is robust although small; to provide a mechanically and electrically reliable connector that can be manufactured and assembled inexpensively; and to provide an improved card edge connector overcoming disadvantages of connectors used in the past.
In accordance with the invention there is provided a card edge connector for interconnecting a printed circuit board having conductive contact regions and a removable printed circuit card having a mating edge with a plurality of conductive contact pads aligned on opposite surfaces of the card. The card edge connector includes an elongated insulating housing with opposed side walls and top and bottom walls. An elongated slot in the top wall receives the mating edge of the circuit card. The slot has an elongated centerline. A plurality of terminals include signal terminals for conducting signals between the contact pads of the circuit card and the contact regions of the circuit board and reference terminals for making ground and power connections between the contact pads and the contact regions. A plurality of transverse terminal receiving cavities extend between the side walls and extend to both sides of the slot. The terminals are mounted in the cavities. The cavities include signal cavities containing only signal terminals and reference cavities containing only reference terminals. The terminals include card contacts extending into the slot for contacting the contact pads of the inserted card and board contacts extending downward through the bottom wall for contacting the contact regions of the circuit board. The terminals in each signal cavity and each ground cavity include a pair of card contacts engageable with a pair of opposed card contact pads and a pair of board contacts at opposite sides of the centerline.
The present invention together with the above and other objects and advantages may best be understood from the following detailed description of the preferred embodiment of the invention illustrated in the drawings, wherein:
PREFERRED EMBODIMENTS Having reference now to the drawings, in
The pertinent structure of the circuit card 16 and the circuit board 14 are shown in
A fragment of the circuit board 14 is shown in FIG. 9. The upper surface 22 of the board includes an array of conductive regions 24. In the illustrated embodiment, the conductive regions 24 are plated through holes. Other arrangements, such as conductive pads for surface mount soldering connections, are also possible. Circuit traces on and/or in the circuit board 14 provide power, ground and signal paths from the conductive regions 24 to other components (not shown) mounted on the circuit board. When the card edge connector 12 is mounted on the circuit board 14 and when a circuit card 16 is inserted into the card edge connector 12, the connector 12 provides circuit paths between the contact pads 20 and the conductive regions 22.
As seen in
Numerous terminal receiving cavities 44 (
The cavities 44 and 46 are separated by internal separator walls or dividers 48 and extend transversely, perpendicular to the slot 34, between the side walls 32. The cavities 44 and 46 intersect and extend to both opposed sides of the slot 34. The bottom of the slot 34 has a stop surface 50 defined in part by the separator walls 48 and by terminal stop projections 52, spacers 54 in the cavities 44 and terminal retention walls 56 in the cavities 46. The separator walls 48 are connected across cavities 44 by spacer 54 that extends only slightly downward from the stop surface 50 of slot 34 On the other hand, separator walls 48 are connected across cavities 46 by terminal retention walls 56 that extend downward from the stop surface 50 of slot 34 substantially to the bottom of the housing 26. The side walls of the slot 34 are defined by the inner edges of comb-like upper portions 48a of the separator walls 48. The lower portions of the cavities 44 and 46 have opposed internal side walls 58. Each cavity 44 and 46 has an open bottom through which terminals may be inserted into the cavities.
Reference terminals 60 are mounted in the cavities 44. The term “reference terminal” is defined here to mean a terminal that provides ground or power connections between the circuit board 14 and the circuit card 16. Signal terminals 62 are mounted in the cavities 46. The term “signal terminal” is defined here to mean a terminal that provides a circuit path for the transmission of ac signals, typically high speed digital signals, between the circuit board 14 and the circuit card 16.
In the preferred embodiment, the reference terminals 60 are all identical to one another and the signal terminals 62 are all identical to one another. The terminals 60 and 62 are flat, planar bodies of metal of uniform thickness, preferably made by stamping from metal sheet stock without any other forming or bending operations. This provides a more efficient manufacturing operation and a sturdier and more reliable terminal in comparison with electrical connectors having terminals that are both stamped and formed. Preferably the terminals 60 and 62 are stamped of phosphor bronze and plated with tin and lead over nickel, with selective gold plating at electrical contact areas, though other alloys or conductive materials may be used.
A pair of spaced apart board contacts 72 extend downward from the body 64. These contacts are received in the plated through conductive regions 24 of the circuit board 14 to connect the terminal 60 to the circuit board. The conductive regions 24 connected to the reference terminals 60 are at a reference voltage of ground or power supply potential. It is important that the connections made to reference voltage be of low impedance. The use of two spaced board contacts for the single reference terminal 60 results in parallel redundant circuit paths and low inductance.
A pair of opposed spring arms 74 extend upward from the body 64. Each spring arm 74 includes a flexible beam with a vertical portion 76 and an inwardly sloped portion 78. The end of the spring arm 74 includes a large segment 80 defining a lead-in surface 82 and a contact region 84. When the mating edge 18 of the circuit card 16 is inserted into the slot 34, an opposed pair of conductive pads 20 enter into each of the cavities 44. The mating edge 18 engages the opposed lead in surfaces 82 and the spring arms 74 resiliently deflect or separate. When the card 16 is fully inserted, the contact regions 84 engage the pads 20 to complete circuit paths from the terminal 60 to the opposed pair of pads 20. As such, redundant paths are provided between the circuit board 14 and the circuit card 16.
Referring now to
A board contact 92 extends downward from the body 86 of each of the terminals 62 in the cavity 46. These contacts 92 are received in the plated through conductive regions 24 of the circuit board 14 to connect the terminals 62 to the circuit board 14. The conductive regions 24 connected to the signal terminals 62 are used to communicate ac signals such as high frequency digital signals between the circuit board 14 and the circuit card 16. The board contacts 92 are transversely offset from the reference terminal board contacts 72 in a staggered pattern.
A spring arm 94 extends upward from each of the bodies 86. Each spring arm 94 includes a flexible beam with a vertical portion 96 and an inwardly sloped portion 98. The end of the spring arm 94 includes a lead-in surface 100 and a contact region 102. The two identical signal terminals 62 are loaded into opposite sides of the cavity 46 in reversed positions relative to one another. The two terminals 62 are at opposite sides of the slot 34, and because of the reverse orientation, the two opposed spring arms 94 slope toward one another at opposite sides of the slot 34.
When the mating edge 18 of the circuit card 16 is inserted into the slot 34, an opposed pair of conductive pads 20 enter into each of the cavities 46. The mating edge 18 engages the opposed lead-in surfaces 100 and the spring arms 94 resiliently deflect or separate. When the card 16 is fully inserted, the contact regions 102 engage the pads 20 to complete circuit paths from the terminals 62 to the opposed pair of pads 20. The use of two distinct terminals 62 in each cavity 46 permits independent signal connections to be made to the opposed contact pads 20 at opposite sides of the circuit card 16.
Because every signal terminal cavity 46 is immediately adjacent to one of the reference terminal cavities 44, the connector 12 of the present invention includes numerous terminal sets generally designated as 104, each including closely spaced and interfacing reference and signal terminals 60 and 62. One of these many terminal sets 104 is shown in
As seen in
The enlarged segments 80 of the reference terminal contact arms 74 provide a large surface area overlying the ends of the signal terminal contact arms 94. Because these segments are larger than required for the conventional mechanical and electrical functions of the contact arms 74, they are defined as “oversize”. The oversize segments 80 provide several important functions. They increase coupling to the signal terminals 62 without significantly adding mass to functional parts of the terminal and possibly impeding mechanical operation. They provide a sturdy and rugged card lead-in area. The use of numerous such reference terminals 60 all having oversize segments in a symmetrical array at both sides of the circuit card 16 provides increased electrostatic shielding of circuits on both sides of the circuit card 16.
Another advantage of the oversize segments 80 is that the size of the segments 80 can be changed to adjust terminal impedance without interfering with the operation of the terminal. The segments could be reduced in length by having them extend only to the broken lines designated as 106 in FIG. 6. The resulting terminal would have an impedance different from a terminal as illustrated with larger segments 80. Though other sections of the terminal may need to be corresponding resized, this feature permits the terminal to be tailored or tuned to specific impedance requirements without interfering with the mechanical function of the terminal.
As can best be seen in
The card edge connector 12 of the present invention provides an advantageous array of circuit paths between the circuit board 14 and the terminals 60 and 62.
The conductive regions 24 and the board contacts 72 and 92 inserted therein are located in four lines all parallel to the centerline 108, two inner lines 110 and 112 and two outer lines 114 and 116. The inner lines 110 and 112 are closer to the centerline 108 than are the outer lines 114 and 116. In the preferred embodiment, the lines 110, 112, 114 and 116 are equally spaced, but if desired the lines 110 and 112 could be spaced farther apart while maintaining symmetry around the centerline 108.
The inner lines 110 and 112 of conductive regions 24 receive only the contacts of a single type of terminal and the outer lines 114 and 116 receive only the contacts of the other type of terminal. In the illustrated arrangement, the inner lines 110 and 112 of through holes 24 receive only the reference terminal board contacts 72 and the outer lines 114 and 116 receive only signal terminal board contacts 92.
Every reference terminal board contact 72 is transversely aligned with and spaced an equal distance from the centerline 108 as another reference terminal contact 72. A transverse line 118 intersects two contacts 72 and illustrates this relationship. Every signal terminal contact 92 also is transversely aligned with and spaced an equal distance from the centerline 108 as another signal terminal contact 92. Another transverse line 120 intersects two contacts 92 and illustrates this relationship.
The circuit path array resulting from the present invention can facilitate routing of conductive traces on the circuit board 14 in comparison with conventional asymmetrical circuit arrays. In addition, the symmetrical array is a characteristic of a terminal pattern that facilitates connector manufacture and assembly.
In the preferred embodiment of the invention, the board contacts 72 and 92 are solder tails that are soldered to the plated through holes 24 of the circuit board 14. Other types of board contacts such as surface mount feet may be used, while retaining the advantages of the present invention. In addition, for some applications, it may be possible to utilize only one board contact for the reference terminals 60.
While the present invention has been described with reference to the details of the embodiment of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims.
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|International Classification||H01R13/652, H01R107/00, H01R13/648, H01R13/62, H01R24/00, H01R12/72, H01R13/6471, H01R13/6474, H05K1/00, H01R12/00|
|Cooperative Classification||H01R13/6471, H01R13/6474, H01R12/721|
|European Classification||H01R23/00B, H01R23/70B|
|Jul 18, 2007||FPAY||Fee payment|
Year of fee payment: 8
|Aug 22, 2011||REMI||Maintenance fee reminder mailed|
|Jan 13, 2012||LAPS||Lapse for failure to pay maintenance fees|