Electrical connectors – Coupling part having handle or means to move contact...
Reexamination Certificate
1999-06-30
2001-02-13
Bradley, Paula (Department: 2833)
Electrical connectors
Coupling part having handle or means to move contact...
C439S259000
Reexamination Certificate
active
06186812
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to sockets for surface mounted, high pin count integrated circuit packages, and more particularly to sockets for ball grid array integrated circuit packages.
BACKGROUND OF THE INVENTION
Surface mounted, high pin count integrated circuit packages have been dominated by quad flat packs (QFPS) with various pin configurations, for example, leadless, J-leaded, and gull wing leaded. These packages have closely spaced leads for making electrical connections distributed along the four edges of the flat packages. These packages have become limited by being confined to the edges of the flat pack even though the pin to pin spacing is small. To address this limitation, a new package, a ball grid array (BGA) is not so confined because the electrical contact points are distributed over the entire bottom surfaces of the packages. More contact points can be located with greater spacings than with the QFPS. These contacts are eutectic or solder balls, which facilitate flow soldering of the packages onto a printed circuit board.
Sockets that accept BGA's are necessary for testing, burn-in, re-programming, but are becoming popular for production use on printed circuit boards where the integrated circuit may need replacing and where the replacing is difficult and endangers the integrity of the complete board. One obstacle to production use of BGA sockets is the cost of the socket. Such sockets have been developed to satisfy the testing and bum-in needs. But these sockets often prove too expensive to be used in production. One such socket is shown in U.S. Pat. No. 5,556,293 to Pfaff. Two other such sockets are shown in U.S. Pat. Nos. 5,578,870 and 5,646,447 referenced above. The first above patent uses three plates including a bias plate, while the other two use springs. Typically such designs will be too expensive for production use.
It is an object of the present invention to provide a BGA socket needing few and simple physical operations to insert and extract an IC package and suitable for production uses.
Another object of the present invention is to provide electrical connections from the ball leads to the socket contacts and then to the runs on a printed circuit card that are reliable and of low resistance. It is a related object of the present invention to provide a contact design that provides a gas tight, reliable connection to the ball lead.
It is another object of the present invention to provide a socket where there are mechanical forces of the BGA ball leads only and none on the BGA package itself.
It is yet another object of the present invention to provide a BGA socket with no obstructions that need to be avoided when inserting and removing the BGA package.
SUMMARY OF THE INVENTION
The foregoing objects are met in a socket for ball grid array packages including a housing with a top structure, a slidable plate constructed as a part of the top structure and forming a top surface of the housing with through holes arranged to receive the ball leads of the ball grid array integrated circuit, the ball leads arranged to enter the holes from the top surface, a plurality of electrical contacts fixed to said socket with a first end arranged to extend into said holes in the top plate from a direction opposite the direction that the ball leads enter, said first ends engage the top of the ball leads above the equator on either side of a meridian of each ball, near the body of the integrated circuit, such that the ball grid array integrated circuit package is retained in said socket, and where the space between the first ends and the edges of the through holes define openings suitable for accepting the ball leads, a cam with a camming surface and an actuator arm constructed to move the slidable plate in a first and a second direction, the first direction to enlarge the opening for accepting the ball leads and the second direction to reduce said openings wherein, with said ball leads inserted into said openings, said ball leads are driven into the first ends, and where the ball leads are captured and retained between the first ends and the opposing surfaces of said holes, and thus making electrical connection from the ball leads to the electrical contacts.
In a preferred embodiment the socket electrical contact includes a bent or cupped, bifurcated or forked end. The forked extensions have edges, which contact the BGA ball leads above the balls'equator providing a detent action on the ball leads, which are thereby retained. The edges of the bifurcated end are sharp and arranged, in a preferred embodiment, to engage the ball leads on either side of a meridian. When such connections are made to the ball leads, the BGA package is captured and retained in the socket. In a preferred embodiment, there is a flat elongated portion contiguous to the cupped portion, wherein the flat portion is arranged to first contact the ball lead above the equator and astride a meridian with a sliding or wiping action that provides a gas tight, reliable electrical connection.
In a preferred embodiment, the means for driving the slidable plate containing the array of holes includes the cam axle rotated by a lever actuator arm extension in contact with the cam axle, the arm is positioned at the side of the socket and does not interfere with insertion or removal of the integrated circuit. The arm is arranged to rotate over a range of at least 90 degrees. But in other preferred embodiments the range may be substantially greater or less. In another preferred embodiment the arm may be secured at one or both ends of its travel to ensure that the open or closed condition of the socket is maintained and is visually evident.
Other objects, features and advantages will be apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings in which:
REFERENCES:
patent: 5833483 (1998-11-01), Lai et al.
Chinnock Paul S.
Farnsworth Jeffrey A.
Ramsey James Michael
Bradley Paula
Cohen Jerry
Gilman Alexander
Kaye Harvey
PCD Inc.
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