Socket for an integrated circuit

Details Socket for an integrated circuit Socket for an integrated circuit

1999-10-13

2001-03-27

Thompson, Gregory (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C174S034000, C361S816000, C439S570000, C439S607070

Reexamination Certificate

active

06208515

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a socket for an integrated circuit.
BACKGROUND INFORMATION
Highly complicated and cost-intensive integrated circuits such as processors are available as components in standardized multipolar housings, such as pin grid array (PGA) or staggered pin grid array (SPGA). For assembly on a circuit board, terminal elements of the integrated circuit, known as pins, are optionally joined directly to terminal elements of the circuit board by soldering, or the integrated circuit is detachably inserted into a socket which is itself soldered onto the circuit board and the electric connections are established between the terminal elements of the integrated circuit and the terminal elements of the circuit board. The greater expense in using a socket as an additional component yields the advantage that it is easy to later replace the integrated circuit, e.g., for repair or for upgrading with a more effective component. With a directly soldered integrated circuit, this would be impossible or could only be done at great expense.
German Utility Patent No. 87 16 007 describes such a socket which is also equipped with a heat sink which is snapped into a carrying frame for cooling purposes. It does not describe any special measures for electromagnetic or electrostatic shielding of the integrated circuit.
German Patent No. 39 22 461 C2 describes a shielding housing which can be used to accommodate various circuits. This housing is essentially cuboid-shaped and has one open side which is closed by the circuit board when the latter is mounted on it. The shielding housing is mounted on the circuit board by inserting four mounting legs provided on the lower edge of the shielding housing in mounting holes on the circuit board and bending them over or soldering them. Circuits accommodated in the shielding housing are soldered directly to the circuit board. This shielding housing disadvantageously makes replacement of components even more difficult. Another disadvantage is that the encapsulation of components has a negative effect on heat dissipation, which must be guaranteed with complex integrated circuits in particular.
SUMMARY
An object of the present invention is to create a socket for an integrated circuit that will permit easy replacement of installed integrated circuits despite the good electromagnetic shielding.
An advantage of the socket according to the present invention is that the integrated circuit is accessible after opening the housing cover and can be removed from a socket insert—optionally with the assistance of a simple lifting tool. For easy opening of the cover, it may be attached using screws, clamps or a snap connection, for example. The electric terminal technique of the socket insert can be designed as with traditional terminal forms and is not subject to any additional restrictions. Thus, for example, terminal elements may be designed using plug-in technology on the side of the integrated circuit, and on the circuit board side the terminal elements may be designed in ball grid array (BGA) or stud grid array (SGA). In particular when surface mounted device (SMD) technology is used on the circuit board side, it is advantageous to secure the socket insert in its position using the socket frame which is mounted on the circuit board. This prevents the extraction forces which occur in removing the integrated circuit from acting on the electric contact points on the socket insert, thereby damaging them. Even during assembly of the socket insert by the press-fit technique, the press-fit pins should not be subjected to an excessively high pulling force. Easy accessibility of the integrated circuit for a lifting tool can be achieved by a chamfer on the inside of the socket frame. If a screwdriver, for example, is used as the lifting tool, the socket frame serves as a bearing abutment with a good lever action close to the component in an advantageous manner. In addition, the socket frame is designed to permit the use of a special lifting tool that can also be used for pushing in the component. Due to the fact that the socket frame is composed of multiple parts, different types of frames can also be assembled advantageously according to a modular principle. This does not have a negative effect on the shielding properties of the housing with regard to electromagnetic or electrostatic influences if the parts overlap at the points of contact. For better heat dissipation, the cover and frame of the socket may also be designed as heat sinks with cooling ribs. For good thermal contact between the cover and the integrated circuit, the cover sits in a form-fitting manner on the top of the integrated circuit, optionally with thermal coupling by means of a heat transfer paste. It is also advantageous to use a heat transfer paste between the cover and the frame. The active surface area in heat dissipation can be further enlarged by mounting a bottom plate on the opposite side of the circuit board and coupling it thermally to the frame and cover of the housing. The heat transfer and the ground connection can also be improved through additional modifications of the circuit board, such as large-area copper surfaces on both sides, joined together with the largest possible number of plated-through holes. A recess provided in the bottom plate can ensure to advantage that terminal elements projecting through the circuit board are not short-circuited. Such a bottom plate may also serve as a bearing abutment in mounting a socket insert with press-fit contacts. With a BGA or SGA design of the socket insert, the bottom plate is preferably flat, i.e, there are no recesses, for better dissipation of heat and to serve as a bearing abutment. Use of SMD technology on the circuit board side also has the advantage that integrated circuits with PGA or SPGA terminal forms which are actually designed for plug-in assembly can be assembled on a circuit board using pure SMD (surface mounted device) technology without having to break through the SMD principle. With this socket, integrated circuits with PGA or SPGA terminal forms that are actually designed for a plug-in assembly can also be assembled with on a circuit board in pure SMD (surface mounted device) technology without having to violate the SMD principle. Integrated circuits for plug-in assembly can also be assembled with circuit board technologies that do not allow through-plated contacts as terminal elements. For example, this is the case with circuit boards with multiple surface wiring, where the number of signal layers is drastically reduced by partial through-plated contacts for connecting conductors on different layers. Due to the fact that it is now possible to use pure SMD technology, this eliminates the steps that would be necessary in a mixed technique for assembling and soldering components in plug-in assembly. In other words, a subassembly need no longer be guided to a manual assembly site and over a flow solder bath in the manufacturing operation. This greatly reduces manufacturing costs.


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