PLGA-BGA socket using elastomer connectors

An electronic assembly that may include an elastomeric connector. The elastomeric connector may couple the solder ball of a BGA integrated circuit package to a substrate. The elastomeric connector provides an interconnect that may compensate for variations in the solder balls and a lack of flatness in the package and/or substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic assembly that contains an elastomeric connector. The elastomeric connector couples a ball grid array integrated circuit package to a substrate such as the motherboard of a computer.

2. Background Information

Integrated circuits are typically assembled into packages that are mounted to a printed circuit board. There are various types of integrated circuit packages including ball grid array (BGA) packages. BGA packages contain an integrated circuit that is mounted to a substrate. The package also contains a plurality of solder balls that are attached to a bottom surface of the substrate. The BGA substrate typically contains routing traces and vias that connect the solder balls to the integrated circuit. The solder balls can be re-flowed to mount the BGA package to another substrate such as the motherboard of a computer.

Because of manufacturing tolerances one or more of the solder balls may be smaller than the other balls. When re-flowed the smaller solder balls may not form a sufficient electrical connection between the BGA package and the motherboard. The insufficient connection may create an open circuit in the assembly. Additionally, the re-flow process and/or assembly process of the BGA package may create a warpage in the package. The warpage will create a lack of flatness that may result in electrical opens in the final assembly. It would be desirable to provide a BGA electronic package assembly that would reduce the probability of electrical opens in the assembly.

The re-flow process typically requires special solder re-flow equipment. This equipment is expensive to purchase and maintain. Additionally, the re-flow process can degrade both the motherboard and the BGA package. It would be desirable to provide an assembly process for a BGA package that does not require a re-flow of the solder balls.

SUMMARY OF THE INVENTION

One embodiment of the present invention is an electronic assembly that may include an elastomeric connector. The elastomeric connector may couple a solder ball of an integrated circuit package to a substrate

DETAILED DESCRIPTION

Referring to the drawings more particularly by reference numbers, FIG. 1 shows an embodiment of an electronic assembly 10 of the present invention. The assembly 10 may include an elastomeric connector 12 that couples an integrated circuit package 14 to a substrate 16 . The substrate 16 may be a motherboard of a computer. The integrated circuit package 14 may be a ball grid array (BGA) package that contains a plurality of solder balls 18 mounted to a package substrate 20 . The package 14 may also contain an integrated circuit 22 that is mounted to the package substrate 20 . The package substrate 20 may contain routing traces, vias etc. (not shown) that electrically connect the integrated circuit 22 to the solder balls 18 . The integrated circuit 22 may be enclosed by an encapsulant 24 . By way of example, the integrated circuit 22 may be a microprocessor.

The elastomeric connector 12 may contain a plurality of conductive portions 26 that are surrounded by a dielectric elastomeric material 28 . Each conductive portion 26 is aligned with a solder ball 18 and a corresponding conductive surface pad 30 of the substrate 16 . By way of example, the elastomeric connector 12 may contain a plurality of metallic leaves that are embedded into a silicone rubber pad. The leaves may be constructed from a gold or copper material. The conductive portions 26 provide an electrical connection between the solder balls 18 and the conductive surface pads 30 .

The assembly 10 may include a housing 32 that captures and aligns the elastomeric connector 12 with the substrate 16 . The housing 32 may be mounted to the substrate 16 by a plurality of mounting pins 34 . The mounting pins 34 align the housing 32 with the surface pads 30 . The housing 32 has inner walls 36 that define an opening 38 . The integrated circuit package 14 and the elastomeric connector 12 are located within the inner opening 38 .

The dimensions of the inner opening 38 , package substrate 20 and the elastomeric connector 12 may be such that the inner walls 36 align the conductive portions 26 with both the solder balls 18 and the surface pads 30 . The housing 30 may be constructed from a relatively inexpensive molded plastic material.

The assembly 10 may include a heat sink 40 that is coupled to the integrated circuit package 12 . The heat sink 40 may include a plurality of fins 42 that extend from a pedestal 44 . The pedestal 44 is coupled to the integrated circuit package 14 . Heat generated by the integrated circuit 22 may flow through the heat sink 40 and into the ambient. The heat sink 40 improves the thermal efficiency of the assembly 10 as is well known in the art.

The heat sink 40 may be attached to the housing 32 by a spring clip 46 . The spring clip 46 may be attached to corresponding tabs 48 of the housing 32 . The spring 46 may be a steel wire that is flexible enough to wrap around the heat sink 40 but have a high enough yield point to exert a spring force onto the sink 40 and the package 14 . The heat sink 40 may be attached to the housing 32 so that the spring clip 46 applies a downward force onto the elastomeric connector 12 .

The downward force may push the connector 12 into a deflected state. The connector 12 may be deflected an amount which insures electrical contact between all of the solder balls 18 and corresponding surface pads 30 of the substrate 16 . By way of example, the elastomeric connector 12 may be deflected an amount that exceeds the maximum cumulative z-axis tolerances of the substrate 16 , connector 12 , solder balls 18 and package 14 . The elastomeric characteristic of the connector 12 can therefore compensate for variations in the flatness of the package 14 and/or substrate 16 . Additionally, the elastomeric connector 12 can compensate for variations in the volume of each solder ball 18 .

The assembly 10 can be assembled by initially mounting the housing 32 to the substrate 16 . The elastomeric connector 12 and integrated circuit package 14 can then be placed within the inner opening 38 of the housing 32 . The heat sink 40 can be attached to the housing 32 with the spring clip 46 . Attachment of the heat sink 40 may push the package 14 and elastomeric connector 12 into the substrate 16 to insure an electrical connection between all of the solder balls 18 and corresponding surface pads 30 . The process does not require a re-flow of the solder balls 18 . Eliminating the re-flow process may decrease the cost and complexity of assembling the assembly 10 .