Vertically stackable sockets for chip modules

The socket system comprises a set of vertically-stackable sockets. A first socket mounts on a printed circuit board to receive a first chip module, and a second socket stacks on the first socket to receive a second chip module. The first socket includes a first set of embedded contacts to electrically connect the first chip module to the printed circuit board, and a second set of embedded contacts to electrically connect the second socket to the printed circuit board. The second socket includes a third set of embedded contacts to electrically connect the second chip module to the printed circuit board. System upgrades are enabled by replacing the chip modules.

BACKGROUND

The present invention relates generally to sockets for chip modules and, more particularly, to vertically-stackable sockets.

In electronic devices, it is often desirable to permit the upgrading, addition, or replacement of integrated circuits and/or circuit modules. For example, in cellular communication devices, the technology employed in the mobile communication network is constantly evolving. In order to upgrade a cellular communication device, the user may be required to replace an RF module and/or baseband processing module. It would be highly desirable to provide a means for users to upgrade their mobile phones or other cellular communication devices as new technologies are deployed by simply replacing chip modules

Also, as the size of cellular communication devices become increasingly smaller, it is desirable to reduce the space requirements for circuit components in a mobile communication device. One way to reduce space requirements is to reduce the number and/or size of components. However, the trend is toward complex circuits that integrate functions of multiple devices. In general, increasing the complexity or functionality of mobile communication devices requires more processing resources. Therefore, new techniques are needed to reduce space requirements circuit components used in mobile communication devices.

SUMMARY

The present invention provides a modular socket system for electronic devices, such as cellular communication devices, personal digital assistants, and computers. The socket system comprises a set of vertically-stackable sockets. A first socket mounts on a printed circuit board to receive a first chip module, and a second socket stacks on the first socket to receive a second chip module. The first socket includes a first set of embedded contacts to electrically connect the first chip module to the printed circuit board, and a second set of embedded contacts to electrically connect the second socket to the printed circuit board. The second socket includes a third set of embedded contacts to electrically connect the second chip module to the printed circuit board. System upgrades are enabled by replacing the chip modules.

In some embodiments, the first socket further includes a frame surrounding said first opening and a series of first projections that extend from said frame into said first opening for mating with complementary projections on said first chip module.

In some embodiments, the second socket further includes a frame surrounding said second opening and a series of second projections that extend from said frame into said second opening for mating with complementary projections on said second chip module.

In some embodiments, the first set of contacts are disposed on said first projections and wherein said third set of contacts are disposed on said second set of projections.

In some embodiments, the projections in said first and second sockets include side surfaces and wherein said contacts in said first and third sets of contacts are disposed on the side surfaces of said projections.

In some embodiments, one or more of said projections include two contacts disposed on opposing side surfaces of the projection.

In some embodiments, the first socket surface mounts on said printed circuit board and wherein said second socket surface mounts on an upper surface of said first socket.

In some embodiments, the second set of contacts is disposed on said upper surface of said first socket.

In some embodiments, the sockets further include one or more retention members to retain said second socket on said first socket.

In some embodiments, the retention members comprise pins that extend into corresponding pin holes in said first and second sockets.

In some embodiments, the retention members comprise spring clips on at least one of said sockets.

In some embodiments, the first socket further includes a heat sink.

In some embodiments, a radio frequency shield is disposed between said first and second chip modules to isolate said second chip module from radio frequency emissions from said first chip module.

In some embodiments, the second socket further includes a metalized bottom forming said radio frequency shield.

In some embodiments, the frames of said first and second sockets are made of a metalized plastic.

In some embodiments, the socket system further comprises a keying mechanism to prevent incorrect alignment of said first and second sockets.

In some embodiments, the keying mechanism comprises one or more locating pins on at least one of said sockets and one or more corresponding pin holes on the other one of said sockets.

DETAILED DESCRIPTION

FIG. 1illustrates a stackable socket system10according to one exemplary embodiment of the invention. The stackable socket system10comprises a first socket20that mounts to a printed circuit board or other substrate (e.g., flex circuit, LTCC, etc.)12, and a second socket60that stacks on top of the first socket20. The first socket20receives a first chip module100, while the second socket60receives a second chip module120. The first socket20provides an electrical connection between the first chip module100and the printed circuit board12, as well as electrical connections for the second socket60. The second socket60provides an electrical connection between the second chip module120and the printed circuit board12. The electrical connection for the second chip module120goes through the first socket100.

In one exemplary embodiment, the first chip module100comprises a radio frequency (RF) module and the second chip module120comprises a baseband module containing one or more processors and memory to process transmitted and received signals. The chip RF module100inserts into the first socket20. The baseband module120inserts into the second socket60. The RF module100and baseband module120can be designed to insert in a single direction to prevent incorrect assembly. The RF module100and baseband module120may comprise circuit boards or packaged integrated circuits. If packaged integrated circuits are used, the shielding can be integrated with the chip package. Alternatively, shielding can be integrated with the first and second sockets20,60as hereinafter described.

The first socket20comprises a generally square or rectangular frame22defining an opening32to receive the RF module100. The frame22may be made of plastic or other electrically insulating material, which may be metalized to provide electromagnetic shielding. The frame22includes an inner surface24, outer surface26, top surface28, and bottom surface30. A series of projections34extend into the opening32from the inner surface24of the frame22. The height of the projections34is approximately one-half the height of the frame22. The first socket20may also include a series of detents46(FIG. 2) in the outer surface26of the frame22. As will be hereinafter described, the detents46may be engaged by spring clips82or other retention members on the second socket60to retain the second socket60in place.

A first set of contacts38are disposed on the side surfaces36of the projections34. The contacts38may be on one side only of each projection34, or on both sides36. The first set of contacts38electrically connects to solder balls40on the bottom surface30of the frame22. A second set of contacts42is disposed on the top surface28of the frame22for making electrical connection with the second socket60. The second set of contacts42electrically connect to solder balls44on the bottom surface30of the frame22. The solder balls40,44may be the type typically found on ball grid array (BGA) type packaging for similar conductor circuits. The solder balls40,44make electrical connection with contacts14,16on the printed circuit board12to electrically connect the first socket20with the printed circuit board12.

The second socket60is constructed similar to the first socket20. The second socket60comprises a square or rectangular frame62that is sized to fit on top of the first socket20. The frame62defines an opening72to receive the second chip module120. The frame62may be made of a plastic, which can be metalized to provide shielding. The frame62includes an inner surface64, outer surface66, top surface68, and bottom surface70. In contrast to the first socket20, the bottom surface70of the second socket60extends across the opening72to form a closed bottom. A series of projections74extend into the opening72from the inner surface64of the frame62. The height of the projections34is approximately one-half the height of the frame22. In some embodiments, a metallic film or metallic layer71may be applied to the bottom surface70to shield the baseband module120from the RF module100.

A third set of contacts78is disposed on the side surfaces76of the projections74to make electrical connection with the baseband module120. The projections74may have contacts78on one side only or on both sides. The third set of contacts78electrically connect to solder balls80disposed on the bottom surface70of the frame62. The solder balls80on the second socket60may be of the type used in BGA type packaging. The solder balls are arranged to contact the second contacts42on the first socket20when the second socket60is mounted on the first socket20.

In the exemplary embodiment shown in the figures, spring clips82function as retention members to retain the second socket60in place on the first socket20. The spring clips82may be integrally formed with the frame62of the second socket60. Alternatively, the spring clips82can be formed of a resilient material, such as spring steel. The spring clips82engage detents46in the outer surface24of the second socket to retain the second socket62in place.

In some embodiments of the invention, the first socket20may include one or more vertical pins50that fit into corresponding pin holes52in the second socket60as a keying mechanism. Those skilled in the art will appreciate that the second socket50could include one or more pins50that fit into corresponding pin holes52in the first socket20. Other types of keying mechanisms could also be used.

The first chip module100comprises a circuit module102having a series of projections104extending from the sides of the circuit module102. The projections104are complementary to the projections34in the first socket20. As seen inFIG. 3, the projections104include contacts108in the side surfaces106of the projections104that engage the first set of contacts38. Contacts108can be formed on one side of the projections104or on both sides. As previously noted, the first chip module100may comprise an RF module for a cellular transceiver.

The second chip module120comprises a circuit module122having a series of projections124extending from the sides of the circuit module122. The projections124are complementary to the projections74in the second socket60. As seen inFIG. 4, contacts128are disposed on the side surfaces126of the projections124. Contacts128can be formed on one side of the projections124or on both sides. The contacts128engage the third set of contacts78on the second socket60.

The first socket20may be surface mounted to the printed circuit board12. The printed circuit board12includes contacts or conductive traces14,16that are engaged by the solder balls40,44to make an electrical connection between the first socket20and the printed circuit board12. Heat may be applied to reflow the solder balls40,44to permanently mount the first socket20. Alternatively, spring clips or snap features (not shown) can be molded into the frame22of the first socket20to mount the first socket20to the printed circuit board12.

The RF module100inserts into the opening32in the first socket20. In a preferred embodiment, the geometry of the projections104enables the insertion of the RF module100in a single direction to prevent incorrect assembly. A heat sink48may be inserted into the first socket below the RF module100to conduct heat away from the RF module100.

After the insertion of the RF module100, the second socket60is removably mounted or stacked on the first socket20. The bottom70of the second socket encloses the RF module100in the first socket20and shields the baseband module120from emissions from the RF module100. In some embodiments, a metal layer or metallic film71can be provided on the bottom70to shield the baseband module120from the RF module100. As previously noted, the second socket60is preferably retained by resilient retention members in the form of spring clips82that yieldably engage with detents46or other features on the first socket20. Thus, the second socket60can be removed to gain access to the RF module100for servicing or replacement.

Finally, the baseband module120inserts into the opening72in the second socket. In some embodiments, a shielded cover or lid (not shown) may be provided. If a cover or lid is provided, the cover is installed to enclose the baseband module120in the second socket60.

The modular design of the socket system10enables devices to be easily upgraded by replacing the chip modules100,120. Further, the design enables upgrades to be performed by untrained persons. The present invention also allows the stacking of chip modules to reduce the space requirements on the circuit board12. While only two sockets20.60are shown, those skilled I the art will appreciate that any number of sockets can be stacked using the principles described herein.