The present invention generally relates to a socket for connecting an IC (Integrated Circuit) to a printed circuit board (PCB), and particularly to a socket including terminals each having a resilient adjustment mechanism which allows the socket to be displaced relative to the PCB due to different coefficients of thermal expansion (CTE) between a housing of the socket and the PCB, without a disconnection between the terminals and the PCB.
Terminals of conventional sockets are mounted to a mother board using Through Hole Technology. Such a method need to form through holes in the mother board thereby hindering an efficient layout of components on the mother board. The related prior art is disclosed in U.S. Pat. Nos. 5,562,474 and 5,730,606.
Newly developed sockets, such as the socket 7 shown in FIG. 8, are mounted to a mother board 8 using Surface Mounting Technology. The socket 7 includes an insulative housing 70 defining a plurality of terminal passageways 73 and a plurality of terminals 74 received in the passageways 73. Each terminal 74 has a curved contact portion 71 and a soldering portion 72 perpendicularly extending from a lower end thereof. The contact portion 71 is adapted to engage a pin 81 of an IC 82. The soldering portion 72 projects out of the passageway 73 for being soldered to an electrical pad 80 on a mother board 8 as follows. A solder ball 9 is attached to the soldering portion 72 of the terminal 74 and then positioned on the pad 80 on the mother board 8. After being processed by an infrared soldering procedure, the solder ball 9 becomes molten and bonds the soldering portion 72 of the terminal 74 and the pad 80 on the mother board 8 together.
It is readily apparent that such a method can promote an efficient use of space on the mother board 8. However, the housing 70 is usually made from a material with a different CTE (Coefficient of Thermal Expansion) than the mother board 8. Thus, the relative position of the housing 70 and the mother board 8 is likely to change significantly during the soldering process, which adversely affects the quality of the solder engagement between the soldering portion 72 of the terminal 74 and the pad 80 of the mother board 8.
A common way to solve the problem of different CETs is to manufacture the housing and the mother board from material having the same CTE. However, such a solution is not workable since the material forming the mother board is expensive thereby increasing the cost of the socket.