Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – Distinct contact secured to panel circuit
Reexamination Certificate
2000-03-15
2001-07-10
Sircus, Brian (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
Distinct contact secured to panel circuit
C439S067000, C439S071000
Reexamination Certificate
active
06257904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a connector assembly with BGA type contacts, and particularly to a connector assembly with an interposer plate for implantation of solder balls thereon.
2. The Related Art
A CPU is a necessary component of a personal computer. For economic reasons the CPU is electrically connected to the mother board by a socket connector. Conventional socket connectors are disclosed in U.S. Pat. Nos. 5,399,108, 5,489,218 and 5,679,020. The conventional socket may be a unitary housing providing a LIF (Low Insertion Force) application or a two piece housing providing a ZIF (Zero Insertion Force) application. Recently SMT (surface mounting technology) has become popular thus such conventional sockets having pin type contacts for wave-soldering attachment to the board can no longer facilitate manufacture.
Ball type contact portions, i.e. BGA (Ball Grid Array), for SMT mounting to a PC board is becoming an increasingly common technique for attaching IC chips. One approach involves attaching ball-like contact leg sections, i.e. solder balls, on a bottom surface of the socket instead of the conventional pin type contact tails. However, the material of the PC board and that of the socket are different. Implantation of the solder balls onto the bottom surface of the socket causes difficulties in manufacture. Additionally, the socket is made by ejection molding and has an inherently loose tolerance in comparison with the PC board which is precisely made with a tight tolerance. The inherent inferior tolerance of the socket may result in positional and coplanarity problems of the implanted balls. Moreover, due to different material properties between the PC board and the socket, CTE (coefficient of Thermal Expansion) mismatch between the socket and the PC board on which the socket is mounted through the solder balls may overstress the solder balls causing rupture of thereof during manufacture.
Therefore, an object of the invention is to provide an improved connector assembly with a BGA (Ball grid Array) contact arrangement which overcomes the problems discussed above.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a connector assembly includes a housing defining a plurality of passageways for receiving a corresponding number of contacts therein. Each contact includes a pin type contact leg section extending a substantial distance beyond an undersurface of the housing. An interposer plate having the same or similar properties as a PC board on which the connector is mounted, is disposed on the undersurface of the housing. A plurality of through holes is provided within the interposer plate in alignment with the corresponding passageways so that a distal end portion of the leg section of each contact can extend into and through the corresponding hole. A solder ball is attachably implanted to a bottom surface of the interposer plate beside each hole, and a trace is provided between each solder ball and the corresponding hole for establishing electrical interconnection therebetween. The leg section of each contact can be retained in the corresponding hole of the interposer plate through a wave soldering procedure, and is electrically connected to the corresponding solder ball through the trace disposed therebetween. The connector together with the associated interposer plate can be mounted to the PC board by applying a reflow process to the solder balls whereby the solder balls partially melt and successively solidify to be attachably soldered to the PC board.
REFERENCES:
patent: 4349862 (1982-09-01), Bajorek et al.
patent: 5691041 (1997-11-01), Frankeny et al.
patent: 5997317 (1999-12-01), Pei et al.
Chung Wei Te
Hon Hai - Precision Ind. Co., Ltd.
Prasad Chaudrika
Sircus Brian
LandOfFree
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