Patent Application
20060091538
This invention relates to the field of integrated circuits and, in particular, to coupling integrated circuits to circuit boards.
Advances in semi-conductor processing and logic design have permitted an increase in the amount of logic that may be present on integrated circuit devices. As a result, integrated circuits have increased the number of input, output, power, and ground signals that are used to power the integrated circuits, to communicate with external devices, and to receive data/instructions. Moreover, the physical size of a typical integrated circuit package has grown to accommodate the increase in the number of pins/pads.
Often, integrated circuits are packaged individually and later coupled to a circuit board to communicate with other devices. One method of coupling an integrated circuit to a circuit board, such as a motherboard or expansion card, includes directly soldering the integrated circuit device to the circuit board. Although, this creates an adequate electrical connection between the pads of the device and the circuit board, the direct soldering of the device creates potential upgrade and swapability limitations. For example, if a microprocessor is directly soldered to a motherboard and is later found to be defective, then the microprocessor needs to be de-soldered. The de-soldering, replacement, and re-soldering process is potentially expensive and tedious.
Therefore, it is common in the industry to use compression sockets to couple an integrated circuit to a circuit board. For example, current Microprocessors, from Intel Corporation in Santa Clara, Calif., are typically, connected to a motherboard using a grid array compression socket.
Another style of compression socket developed by Tyco Electronics Corp., metallized-particle-interconnect (MPI) socket, is designed to have good high frequency inductance and capacitance characteristics by utilizing a polymer based compressible column with silver particles. A typical compressed height of an MPI column is 0.036 inches. However, on current integrated circuits active and passive devices, such as capacitors coupled to the microprocessor, require more space between the integrated circuit and the circuit board than 0.036 inches.
The present invention is illustrated by way of example and not intended to be limited by the figures of the accompanying drawings.
a illustrates an enlarged portion of
b illustrates an enlarged portion of
In the following description, numerous specific details are set forth such as specific column heights, interposer heights, polymer bases, and other specific materials in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice the present invention. In other instances, well known components or methods, such as well-known packaging, soldering, and force applying/compression techniques, as well as specific heat spreader/sink devices, etc., have not been described in detail in order to avoid unnecessarily obscuring the present invention.
The apparatus and method described herein are for coupling an integrated circuit to a circuit board through a low profile compression socket. It is readily apparent to one skilled in the art, that the method and apparatus disclosed herein may be implemented in any system where a device is coupled to a circuit board. For example, the apparatus and methods described herein may be used for coupling an embedded controller to a printed circuit board or a microprocessor to a motherboard.
Additionally, integrated circuit 205 is not limited to a microprocessor in a flip-chip package. In fact, integrated circuit 205 may include a controller hub, programmable array logic (PAL) device, a clocking circuit, a microcontroller, an embedded processor, a memory device, a network controller, a graphics controller, or an audio controller. Examples of controller hubs include a north bridge or memory controller hub, a south-bridge or interconnect controller hub, or other chipset related device.
Circuit board 235 may be any printed circuit board, including graphics cards, motherboards, device interface cards (network cards, modems, universal serial bus cards, TV tuner cards, etc.), and printed circuit boards used for embedded controllers. As a specific embodiment, circuit board 235 is a multi-layered motherboard for coupling integrated circuit 205 to, as well as a plurality of other integrated circuits.
Physically and electrically coupling/contacting integrated circuit 205 to circuit board 235 is low-profile compression socket 200. Compression socket 200 comprises a plurality of compressible columns, such as compressible column 210, molded and/or disposed in substrate 215. In one embodiment, compressible column 210 comprises a polymer base and metal particles. One example of a polymer compound is a silicone material, such as silicone rubber, where the silicone material has very low compression-set properties. Any metal particles, including silver may be dispersed through out the polymer base to form compressible column 210. Compressible column 210, when compressed, is a conductor, which provides an electrically conductive path. An example of a polymer based compressible column is a metallized-particle interconnect (MPI) column developed by Tyco electronics.
Compressible column 210 usually has a compressed height in the range of 0.030 to 0.042 inches. As a specific example, compressible column 210 has a compressed height of 0.036 inches. As stated above, compressible column 210 is disposed in substrate 215. Substrate 215 is typically used as a stiffener to hold compressible columns 210. Examples of materials used for substrate 215 include: flex cable, rigid board, rigid flex board, and fiber glass/epoxy board, such as FR4. Substrate 215 will be discussed in more detail in reference to
Compression socket 200 further comprises interposer 220. Interposer 220 may comprise any insulating material, such as flex cable, rigid board, rigid flex board, and FR4. Interposer 220 comprises conductive paths, such as conductive path 225. Conductive path 225 is any path for making electrical connection on its overlying side (the side to electrically contact compressible columns 210 in
Interposer 220 has the additional advantage of adding height to low profile compression socket 200, so land-side caps 207 have enough clearance, as not to contact circuit board 207. As an example, land-side caps 207 have a height of 0.055 inches. Compressed columns disposed in a substrate, such as compressible column 210 in substrate 215, have a height of 0.036 inches. If only the compressed columns in compressions socket 200 were used, land-side caps 207 would not have enough clearance. Therefore in this example, interposer 220 with collapsed solder balls 230 have a height of 0.030 inches, creating a total height for compression socket 200 of 0.066 inches; this leaves 0.011 inches of clearance for land-side caps 207. In another embodiment, interposer 220 has a height in the range of 0.015 to 0.045 inches.
Interposer 220 may also comprise, but is not required to include, alignment apertures for alignment pins, such alignment pin 233, which is coupled to substrate/insulator 215. Alignment pins potentially aid in aligning the compressible columns with corresponding conductive paths during assembly.
Also shown in
An alternative to top clamping plate 245 and bottom clamping plate 240 is the use of tension pins to couple integrated circuit board 235. Co-pending application with application Ser. No. ______ entitled “Hybrid Compression Socket Connector for Integrated Circuits,” discloses an apparatus and method for coupling an integrated circuit to a circuit board using tension pins to engage corresponding barrels in the circuit board.
Turning to
Moreover, compressible columns 210, when compressed, make electrical connection with conductive path 225. Conductive path 225, as stated above, may include a press-fit pin or connection pads with a via. Consequently, when compression socket 200 is compressed, conductive path 225 makes electrical connection with compressible column 210 and circuit board connection pad 320 through solder ball 230.
b illustrates another embodiment of compression socket 200. In
b also illustrates connection pad 330, via 335, and an underlying connection pad 340 in place of a press-fit pin for conductive path 225. Just as substrate 215 may be used as an active substrate, interposer 220 may be used as an active interposer, where overlying and underlying connections pads 330 and 340 make electrical connection with interconnects present in interposer 220.
Referring to
Next, in block 515 an integrated circuit is clamped to the circuit board to compress the compressible columns. In one embodiment, clamping includes clamping a top clamping plate to a bottom clamping plate to compress the compressible columns. As an alternative, tension pins are inserted into corresponding barrels in the circuit board, as described in co-pending application with application Ser. No. ______ entitled “Hybrid Compression Socket Connector for Integrated Circuits,” to clamp the integrated circuit to the circuit board and to compress the compressible columns. Finally, in block 520 an external test device, such as an oscilloscope, logic analyzer, spectrum analyzer, or other external device.
As can be seen from the discussion above, adequate clearance for active or passive devices place on the land-side of an integrated circuit is provided in a low profile compression socket comprising a substrate with compressible columns and an interposer with conductive paths, without forfeiting beneficial high-frequency inductance and capacitance characteristics. Furthermore, the substrate may further comprise interconnects and a test port for connecting to an external test device; this potentially allows for quick and easy connection of external devices in testing situation.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
