Electrical connectors – Coupling part with actuating means urging contact to move...
Utility Patent
1999-07-23
2001-01-02
Nguyen, Khiem (Department: 2839)
Electrical connectors
Coupling part with actuating means urging contact to move...
C439S266000
Utility Patent
active
06168449
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to test sockets for high pin count integrated circuit packages, and more particularly to test and burn in sockets for ball grid array integrated circuit packages.
2. Description of the Related Art
Surface mounted, high pin count integrated circuit packages have been dominated by quad flat packs (QFPS) with various pin configurations. These packages have closely spaced leads for making electrical connections distributed along four edges of the flat packages. These packages have become limited by being confined to the edges of the flat pack even through the spacing between the pins is small.
A new package, a ball grid array (BGA) has been adopted to meet the requirement of high pin count, in which the electrical contact points are distributed over the entire bottom surface of the packages to overcome the problem of insufficient space in the edges for the pins. More contact points can be located with greater spacing than with the QFPS. These contacts are solder balls that facilitate flow soldering of the packages onto a printed circuit board. Thus, BGA's are popular than QFP's.
Sockets that accept BGA's are necessary for testing, burn-in, re-programming, and sometimes for production use where the integrated circuit may need replacing. Several such sockets have been developed to satisfy this need, and most of them are of a clam shell design, wherein a hinged top opens to allow package entry, and closing the top retains the package within the socket. The socket includes a bed of contacts spaced to match the BGA contacts and a spring load is arranged to press the package onto the bed of contracts to ensure electrical connections. It is, however, found that the socket contacts place forces onto the IC contacts in the same direction. This force drives one side of the package against an abutment of the socket. With a large number of contacts this cumulative force of many spring loaded contacts is very large and may physically damage the package.
U.S. Pat. No. 5,578,870 to Farnsworth et al. on Nov. 26, 1996 discloses a top loading test socket for ball grid arrays. In said patent, a movable plate is used. The ball contacts are lowered into through-holes in the plate when applying a force to a lever arm to move the plate. A spring means returns the plate to its initial position after the force is removed, such that the electrical contacts that extend through the through-holes of the plate are lowered to bear against the ball contacts to thereby retain the BGA IC in place. In such an improved arrangement, each ball contact is born by a corresponding electrical contact in the same direction, while the other side of the ball contact bears against an edge of the corresponding hole. It is, however, found that the BGA IC is ejected out of the test socket as a result of being subjected to uneven forces if the ball contacts bear the corresponding holes in different relative points (see
FIG. 1
of the drawings). In addition, the electrical contacts bear against the ball contacts and thus tend to be damaged in the bearing points after a long-term use.
U.S. Pat. No. 5,556,293 to Pfaff issued on Sep. 17, 1996 discloses a mounting apparatus for ball grid array device that also uses a plate movable in a direction identical to that disclosed by U.S. Pat. No. 5,578,870. Accordingly, the ejection problem of the IC out of the test socket as a result of uneven forces is inevitable.
The present invention is intended to provide improved test sockets for integrated circuits that mitigates and/or obviates the above problem.
SUMMARY OF THE INVENTION
In view of the problem of the prior art, it is a primary object of the present invention to provide a test socket for a ball grid array integrated circuit that is subjected two symmetric forces on both sides, thereby avoiding ejection of the integrated circuit out of the test socket as a result of uneven forces.
It is another object of the present invention to provide electrical contacts that are in arcuate surface contact with the ball contacts to avoid damage to the ball contacts.
It is a further object of the present invention to provide a test socket that allows easy insertion and extraction of the integrated circuit.
In order to achieve the above objects, the conventional test socket has been improved by the present invention such that the sliding plate of the conventional test socket is replaced by two symmetric sliding plates, and two elastic elements are symmetrically disposed to two opposite sides of the sliding plates. By means of provision of the mechanism arranged in the upper lid and the sliding plates, the sliding plates slide horizontally away from each other when the upper lid is subjected to a downward force. The elastic elements provide returning forces after the downward force is removed. In addition, the electrical contact is designed to have a curved section. The lower section of each electrical contact is inserted into the frame body that acts as a base, and the upper curved section of each electrical contact bears against an inner periphery of an associated through-hole of the sliding plate. The upper end of the curved section is arcuate to mate with the ball contact.
When the sliding plates move away from each other as a result of an external force, upper ends of the electrical contacts are displaced by the sliding plates such that the arcuate section of each electrical contact and the inner periphery of the associated through-hole of the sliding plates together defines a space for receiving an associated ball contact. The ball contact moves downwardly along with the integrated circuit to be tested. The external force is then removed to return the sliding plates to their close contact status, while the arcuate section of the upper end of each electrical contact contacts the associated ball contact. Since the sliding plates are symmetrically arranged, the left half electrical contacts and the right half electrical contacts bear against left sides and right sides of the associated ball contacts, respectively. Thus, the integrated circuit to be tested is subjected to even forces to thereby avoid the problem of ejection of the integrated circuit out of the test socket as a result of uneven forces in the prior art.
In addition, the upper lid includes an opening having a size the same as that of the integrated circuit to be tested to allow convenient insertion and extraction of the integrated circuit and to restrain horizontal movement of the integrated circuit.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5556293 (1996-09-01), Pfaff
patent: 5578870 (1996-11-01), Farnsworth
patent: 6036503 (2000-03-01), Tsuchida
patent: 6050836 (2000-04-01), Tohyama
Day Gau-Ching
Horng Rong-Fang
Huang Hsiang-Yu
Huang Ta-Chou
Huang Yuh-Wen
Dykema Gossett PLLC
Industrial Technology Research Institute
Nguyen Khiem
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