Spring biased socket system

A socket may be formed with socket pins that include two spring biased arms biased to extend away from one another. The arms may be provided with tapered upper surfaces that engage contact holes on a pin guide 18 of an integrated circuit package, camming the socket pin arms together. The pin guide may have a tapered via structure that expands as it extends into the package. Thus, as the spring arms spread apart inside the pin guide, they may rotate through an angle which causes contacting surfaces on the spring arms and the pin guide to be parallel, creating good surface contact.

BACKGROUND

This invention relates generally to connecting electrical integrated circuits to printed circuit boards and other devices.

Generally, a socket is used to electrically couple a package containing a semiconductor integrated circuit to a printed circuit board. The socket may be a number of types, including a pin grid array or land grid array architecture. In a pin grid array architecture, pins are mounted on the package land pads. This method may tend to be more expensive and may require maintaining the pins in an unbent configuration. Because a large number of pins are provided and their structural integrity is limited, it may be difficult to avoid damaging the pins.

The land grid array packing approach may involve significant pressure to maintain low contact resistance. This may require a relatively robust and mechanically stiff construction for the socket housing and for the board to which the socket connects. The land grid array may use bent pins that touch land pads located on the package.

Thus, there is a need for other types of packages.

DETAILED DESCRIPTION

Referring toFIG. 1, a socket pin10may protrude from a socket (not shown). The socket pin10may engage a package34. The package34may include a U-shaped pin guide18. While one pin guide18and one socket pin10is shown, conventionally there would be a very large number of socket pins10on the socket and a very large number of mating pin guides18on the package34.

A pair of opposed surfaces24define a slightly narrowed opening25to receive the socket pin10. The pair of opposed sidewalls22extend inwardly into the package34from the surfaces24. The sidewalls22diverge as they extend inwardly so that the inward surface23may be wider than the opening25defined by the surfaces24.

The socket pin10may be made up of two or more arms15which are separated by a slot12, which extends inwardly into the pin10. Conventionally, the pin10may be made of resilient material so that the arms15tend to resiliently spread apart and away from one another.

Each arm15includes a tapered leading edge surface16. The surface16allows the arm15to be wedged towards its opposed arm15by the interaction with the surface24. Each arm15also includes a contact surface14which contacts a sidewall22of the pin guide18.

Thus, when the socket pin10engages the opening25, the surface24cams the surface16to move the arms15together and allow the socket pin10to enter the pin guide18. As it enters the diverging via contact28, the arms15are allowed to spring outwardly, maintaining good contact between the sidewalls22and the surfaces14on the socket pin10. Moreover, a parallel contact surface is achieved because of the angulation of the spreading arms15and the pre-angulation of the via contact28sidewalls22.

In some embodiments, a slide plate (not shown) can be used to hold the arms15in an abutting position for insertion. The closing force supplied by the slide plate may then be removed once the pins10are inserted into the pin guides18, by an appropriate displacement of the slide plate.

In some embodiments, the socket pin10may have a higher contact pressure and, therefore, contact resistance may be lower. Also, the loop inductance for the pin may be lower in some embodiments, compared to land grid arrays and pin grid array designs. The improvement may be due to the shape of the pin10in some embodiments. The total pin length for land grid array pins may be larger than that of the pin10in some embodiments. Compared to the pin grid array design, the electrical current path through the pin10may be shorter in some embodiments and, therefore, the performance may be better. In some embodiments, the pin10has a smaller landing via pad and, therefore, the negative discontinuity effect is lower in higher frequency applications.

Referring toFIG. 2, a bi-directional solution is illustrated. In this case, a printed circuit board42includes vias44that receive the socket pins10. The vias44may correspond to pin guides18in one embodiment. The socket pins10may protrude from two opposed surfaces of a socket40in this embodiment. Thus, the socket pins10, on the upper surface of the socket40, engage vias36in the package34. The vias36may correspond to pin guides18in one embodiment.

The package34may carry a die30in one of a variety of configurations. In the embodiment illustrated inFIG. 2, which is not intended to limit the scope of the invention, the die30may be attached in a surface mount configuration using solder balls32.

Thus, in the embodiment shown inFIG. 2, the pins10may have pairs of arms15on two opposed sides to engage the package34above and the board42below. The package34and board42may each include pin guides18to receive the arm15pairs (not shown inFIG. 2).

Moving toFIG. 3, in this case a mixed solution is illustrated using the via grid array connection shown inFIG. 1for the electrical connection between the package34and the socket40and using a land grid array type connection as well. Thus, the pins54may correspond to the pins10and include arms15(not shown inFIG. 3) only on the upper side to engage vias52in the package34. The vias52may correspond to the pin guides18in one embodiment. The opposed surfaces of the pins54may be connected by solder balls50to the printed circuit board42. Additional pins48may be of the land grid array package type, contacting lands46on the package34in one embodiment.

Referring next toFIG. 4, pins54may correspond to socket pins10with arms15only on one end to engage vias36in the package34. The vias36may correspond to pin guides18in one embodiment. On the opposite end of the pins54, a solder ball connection50may be made to the printed circuit board42. In this embodiment, the land grid array pins48may not be used.

In another embodiment of the present invention, shown inFIG. 5, an array capacitor60may be mounted on the package34. In this case, the single ended pins54may plug into vias62in the array capacitor60. The vias62may correspond in all respects to the pin guide18in one embodiment of the present invention. The upper ends of the pins54may correspond, in one embodiment, to that shown inFIG. 1in one embodiment of the present invention. In this embodiment, the connections between the rest of the package34and the socket64may be implemented using land grid array pins66and lands68on the package34. The package shown inFIG. 5may be particularly applicable to high power devices.

In another embodiment, the connections to the package34may use a pin grid array approach. In other embodiments, all of the connections may utilize the connection type shown inFIG. 1.

FIG. 6shows an embodiment corresponding toFIG. 2, except that the pins10extend completely through the socket40and the printed circuit board42, forming a so-called through-hole board interface solution. The through-hole78is formed completed through the printed circuit board42. The via52in the package34may correspond to the pin guide18in one embodiment. The pins54may have an upper end which corresponds to the socket pin10shown inFIG. 1. The pins54may be fixed to the printed circuit board42using standard solder reflow processes in one embodiment of the present invention.

In some embodiments, the engagement between the socket end10and the pin guide18may be self-aligned and the pin is self-guided. The contacting pressure for holding the pins of the socket structure in a package or board is relatively high and the contacted surfaces may be parallel in some embodiments. The via structures may, therefore, be arranged to distribute contact pressure in one embodiment. A relatively small via pad may be utilized in some embodiments to reduce high frequency discontinuity effects. A larger contacting surface may be provided in some embodiments, increasing contacting pressure compared to pin grid array and land grid array packages. Therefore, in some embodiments, significant socket electrical performance improvement may be achieved.