Electrical connectors – With supporting means for coupling part – Comprising or for use with supporting panel
Reexamination Certificate
1999-04-26
2001-03-06
Nguyen, Khiem (Department: 2839)
Electrical connectors
With supporting means for coupling part
Comprising or for use with supporting panel
C439S876000
Reexamination Certificate
active
06196871
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for adjusting differential thermal expansion between an electrical socket and a circuit board having different coefficients of thermal expansion (CTE).
With the rapid development of electronic instruments, a variety of corresponding electrical components are successively developed to support the technological advances gained by the electronic instruments. For a modularized central processing unit (CPU) of a computer, an electrical socket is mounted on a circuit board to firmly assemble the CPU thereto. Such electrical connector is arranged with a number of conductive contacts in arrays. One end of each contact extends from one side of the socket for electrically contacting with corresponding conductive sections of the CPU, while the other end of each contact extends from the other side of the socket for electrically connecting with the circuit board.
Through hole technology is often employed for attaching an electrical socket to a circuit board. One end of each contact of the electrical socket extends into a corresponding through hole of the circuit board. However, the through holes of the circuit board should be arranged in arrays corresponding to the contacts of the electrical socket thereby occupying space on both sides of the circuit board. Such a procedure complicates manufacture of the circuit board and does not promote an efficient use of space thereon, especially when the arrangement of the contacts of the electrical socket is dense.
Therefore, a ball grid array (BGA) type modularized CPU package has been developed, which directly solders a number of solder balls to an electrical socket for electrical connection with a circuit board. The corresponding conductive contacts of the electrical socket each form two opposite ends for respectively engaging with the solder balls and disc-shaped contact pads formed on a surface of the circuit board. The solder balls are then heated to reach a melting point thereof whereby the contacts are soldered to the corresponding contact pads.
Due to new applications and configuration designation requirements, an insulative housing of the electrical socket and the circuit board should be constructed from different material with different coefficients of thermal expansion (CTE). The difference in CTE will result in different thermal expansions thereof which may create a fracture stress exerted on the solder balls attached to the contacts of the socket thereby misaligning some of the contacts of the socket with the corresponding contact pads of the circuit board during the heating process.
Thus, if the solder balls can not be properly deposited on the contact pads, the poor soldering quality and inadequate electrical reliability may result. In serious cases, a short circuit may be formed between the electrical socket and the circuit board. Furthermore, a significant fracture stress acting on the solder balls between the contacts of the socket and the contact pads of the circuit board may result in the contacts becoming disconnected from the socket.
BRIEF SUMMARY OF THE INVENTION
The main object of the present invention is to provide a method for adjusting differential thermal expansion between an electrical socket and a circuit board which are soldered together.
Another object of the present invention is to provide an adjusting device to reduce a fracture stress resulting from differential thermal expansion for preventing the misalignment of a plurality of solder balls attached between conductive contacts of a socket and contact pads of a circuit board.
In accordance with one aspect of the present invention, a method for adjusting differential thermal expansion includes the following steps: manufacturing, planting, adjusting and heat treating. In the adjusting step, an adjusting device is deposited between an electrical socket and a circuit board before the heat treating step for preventing misalignment of the conductive contacts of the electrical socket, and for reducing fracture stress due to the different thermal expansions.
In accordance with another aspect of the present invention, the adjusting device which is made of adhesive fusible material, such as thermoplastic or another suitable material which melts easily when properly heated, is viscidly adhered to an electrical socket and a circuit board thereby effectively eliminating the likelihood of misalignment of the solder balls for ensuring stable and reliable communication between the electrical socket and the 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.
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Chung Wei Te
Hon Hai - Precision Ind. Co., Ltd.
Hyeon Hae Moon
Nguyen Khiem
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