Electrical connectors – With coupling movement-actuating means or retaining means in... – Including compound movement of coupling part
Reexamination Certificate
2000-01-24
2001-05-15
Paumen, Gary F. (Department: 2833)
Electrical connectors
With coupling movement-actuating means or retaining means in...
Including compound movement of coupling part
C439S070000, C439S083000
Reexamination Certificate
active
06231367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for achieving uniform expansion of a dielectric plate and an electric connector made in accordance therewith.
2. The Prior Art
A computer central processing unit (CPU) is mounted to a main computer board by means of a connector. Conventionally, the CPU connector has contacts extending beyond top and bottom faces thereof for electrical engagement with pins of the CPU and conductive traces of the main board. The contacts are soldered to the main board by a through hole technique. Such a connector structure occupies a substantial amount of space on the main board and requires a sophisticated process to mount the connector thereto.
A ball grid array (BGA) connector effectively overcomes the problems discussed above. As shown in
FIG. 8
of the attached drawings, a BGA connector
8
comprises a dielectric base plate
83
defining a number of contact receiving passages
80
therein between top and bottom faces thereof for receiving and retaining conductive contacts
81
. Each contact
81
has a solder support section
82
extending beyond the bottom face of the base plate
83
. A solder ball
9
is attached to the solder support section
82
by heating the solder support section
82
in advance. The solder balls
9
may be molten and fixed to a circuit board (not shown) by a heating process which provides an efficient and effective way for soldering the connector
8
to the circuit board.
Since the base plate
82
of the connector
8
and the circuit board are generally made of different material having different thermal expansion coefficients, heating the solder balls
9
to fix the contacts
81
to the circuit board will result in different amounts of thermal expansion of the circuit board and the base plate
83
leading to an undesired strain induced in the solder balls
9
.
Furthermore, the base plate
83
is usually made by injection molding. During the molding process, a plasticized dielectric material is injected into a mold. Due to the complicated configuration of the base, a non-uniform distribution of the molecules of the dielectric material will result leading to different thermal expansion coefficients in different directions of the base plate
83
when the base plate
83
is heated during a BGA soldering process. Such non-uniform thermal properties magnify the above problem.
Thus, it is desired to provide a method for achieving substantially uniform thermal expansion of a dielectric plate in order to alleviate the problems discussed above.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a method for achieving substantially uniform thermal expansion of a dielectric plate.
Another object of the present invention is to provide a method for achieving substantially uniform thermal expansion between a connector and a circuit board to which the connector is mounted.
A further object of the present invention is to provide a base plate of a connector which has substantially uniform thermal expansion properties.
A still further object of the present invention is to provide an electrical connector having a base that has substantially uniform thermal expansion in different directions.
To achieve the above objects, an electrical connector includes a dielectric base plate in which steel and copper strips are embedded. The steel and copper strips are respectively arranged in opposite sides of the base plate and are substantially perpendicular to and interconnected to each other whereby when the base is subject to a heating process, the steel and copper strips limit and control thermal expansion in different directions of the base plate and reduce differences in thermal expansion between the base plate and a circuit board to which the connector is mounted.
Furthermore, a method for achieving substantially uniform thermal expansion of a dielectric plate is also provided. The method comprises the steps of (1) providing a dielectric plate made by injection molding and (2) fixing steel and copper strips thereto for limiting and controlling thermal expansion of the plate in different directions to achieve substantially uniform thermal expansion of the plate.
REFERENCES:
patent: 4555157 (1985-11-01), Johnson et al.
Hsiao Shihwei
Szu Ming-Lun
Chung Wei Te
Hon Hai - Precision Ind. Co., Ltd.
Paumen Gary F.
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