Electrical socket

Details Electrical socket Electrical socket

1999-06-29

2001-01-30

Patel, T. C. (Department: 2839)

Electrical connectors

Preformed panel circuit arrangement, e.g., pcb, icm, dip,...

With provision to conduct electricity from panel circuit to...

C439S083000

Reexamination Certificate

active

06179623

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an electrical socket, and particularly to an electrical socket supporting an integrated circuit (IC) chip and being securely surface mounted to a circuit board thereby achieving reliable interconnection between the IC chip and the circuit board.
An integrated circuit chip is commonly mounted to an electrical socket which then is secured to a circuit board via soldered connections between contacts of the socket and the circuit board. At present, the soldering connections between a socket and a circuit board are usually achieved by surface mount technology (SMT) or through hole technology (THT). THT has become less frequently employed since the required through holes do not make an efficient use of space on a circuit board. SMT is used in a wide range of applications due to the small space requirement on a circuit board.
A conventional socket is disclosed in U.S. Pat. No. 5,746,608. Contacts of the socket are adapted to provide electrical connection between the socket and a circuit board.
Another conventional socket is shown in FIG.
3
. An electrical socket assembly
8
comprises a dielectric base
80
, a plurality of contacts
81
, a circuit board
82
and a chip module
83
. The base
80
defines a plurality of engaging slots
84
communicating with the receiving chambers
85
. The contacts
81
are received in corresponding receiving chambers
85
. One end
88
of each contact extends outside of the receiving chambers for being surface mounted to the circuit board
82
via a solder ball
86
attached thereto. The chip module
83
comprise a plurality of engaging terminals
87
extending into the receiving chambers
85
through the engaging slots
84
to electrically engage with the corresponding contacts
81
. Electrical communication between the chip module
83
and the circuit board
82
is thereby achieved.
However, differences in coefficients of thermal expansion (CTE) between a socket and a corresponding circuit board cause problems in conventional surface mount connections. Misalignment between contacts of the socket and corresponding soldering pads of a mating circuit board caused by the CTE problem results in poor communication quality. Furthermore, in the second example discussed above, the solder balls
86
easily wick into the receiving chambers
85
when melted during the surface mount procedure thereby adversely affecting the quality of the connection. Therefore, an improved socket is required for eliminating the negative effects resulting from the CTE problem and for preventing solder from wicking into an interior of the socket.
BRIEF SUMMARY OF THE INVENTION
A main object of the present invention is to provide an electrical socket which can be securely surface mounted to a circuit board via a bottom board made of the same material as the circuit board thereby overcoming problems related to differences in CTE and achieving reliable communication quality.
A second object of the present invention is to provide an electrical socket which can eliminate negative effects resulting from the CTE problem thereby avoiding misalignment between contacts of an electrical socket and soldering pads of a mating circuit board.
A third object of the present invention is to provide an electrical socket having a dielectric base which can prevent solder from wicking into an interior of the base, thereby ensuring signal transmission quality.
In accordance with one aspect of the present invention, an electrical socket mainly comprises a dielectric base having a mating surface, a joining surface and a plurality of receiving chambers defined between the mating surface and the joining surface, a plurality of contacts received in the receiving chambers and a bottom board. Each contact comprises a soldering section and a mating section. The bottom board is made of the same material as a mating circuit board and is disposed between the base and the circuit board. A plurality of engaging apertures are defined in the bottom board for extension of the soldering ends of corresponding contacts therethrough to be soldered onto the mating circuit board. The present invention can overcome the negative effects resulting from the CTE problem because the soldering process occurs between the bottom board and the mating circuit board which have the same CTE.
The soldering section of each contact further forms a curved section which has two corners bent at an appropriate angle for preventing molten solder from wicking into the receiving chambers via the engaging apertures of the bottom board. Moreover, the base forms at least a stand-off projecting toward the bottom board for distancing the bottom board from the base thereby further preventing the molten solder from wicking into the receiving chambers of the base. A space is simultaneously provided for permitting slight deformations of the contacts due to reasons other than the CTE problem of the base and the mating circuit board.
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: 3602875 (1971-08-01), Pierini
patent: 3621444 (1971-11-01), Stein
patent: 4693528 (1987-09-01), Asick et al.
patent: 5834848 (1998-11-01), Iwasaki

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