Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Device held in place by clamping
Reexamination Certificate
1999-09-07
2001-02-20
Ngô, Ngân V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Device held in place by clamping
C257S692000, C257S698000
Reexamination Certificate
active
06191480
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to mechanisms for engaging electronic circuit modules with or in land grid array (LGA) socket devices. More particularly, the present invention is directed to a mechanism which reduces stress on electronic circuit components while at the same time provides access for direct lid or heat sink attachment. Even more particularly, the present invention is directed to land grid array socket mechanisms which apply a continuous yet distributed force for engagement, but which still permit easy removal of the electronic circuit component portion.
The land grid array interconnection system is one that is widely requested and is a highly desirable mechanism for engagement between electronic circuit components and underlying sockets for mechanical and electrical interconnection. However, land grid array interconnection mechanisms suffer from certain disadvantages. In particular, these mechanisms typically require relatively large compressive forces in order to maintain sufficient electrical contact throughout the card/socket/module system. Typically these forces are generated by clamping a bulky pressure plate which fits entirely over the top surface of the module assembly. This pressure plate is typically fastened to the card via screws. However, the compressive force generated by such a mechanism can impart large tensile, compressive and shear stresses on sensitive electrical components such as the silicon chip, the chip carrier (which is typically ceramic), the chip underfill material, lid adhesive and any thermal compound which may be disposed between the chip and an overlying lid. Accordingly, packaging structures employing direct lid attach (DLA) ceramic packaging are not particularly well suited for standard LGA interconnection mechanisms. However, it is nonetheless very desirable to be able to employ direct lid attach packaging.
Over time it is also possible that certain failures can occur in standard land grid array engagement mechanisms. In particular these include interface delamination, bulk material fracture and material creep. These stresses are predicted to cause some highly stressed modules to fail.
An added disadvantage to the standard pressure plate land grid array interconnection system is that it entirely covers the top surface of the module. Thus, thermal performance is significantly degraded due to the low thermal conductivity of the pressure plate which typically comprises a material such as steel which is provided for its strength. However, the thermal conductivity of steel is significantly less than the thermal conductivity of such materials as aluminum or copper. Additionally, the added thermal interface that exists between the pressure plate and the top surface of the module also acts to degrade thermal performance. Since the land grid array interconnection mechanism is largely targeted for leading edge and high performance, high thermal stress modules, this limitation in thermal performance is very desirable particularly in modules that generate significant amounts of heat.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention a semiconductor packaging assembly includes a land grid array socket together with a land grid array module. This module includes a semiconductor device disposed on top of a carrier which has top portions of its exposed areas surrounding the die so as to form a lip or at least a lip-like structure. More particularly, a ring shaped pressure plate is employed in contact with the lip portion of the module. This pressure plate includes integral spring members which provide a mechanism for urging the pressure plate against the module so as to ensure uniform contact between the module and the land grid array socket.
In accordance with another embodiment of the present invention a semiconductor package assembly comprises a land grid array socket and land grid array module substantially is described above. However, in this alternate embodiment a support frame structure which is affixed to a printed circuit card is provided. This support frame includes two hinge support structures disposed on opposite sides. At least two pressure rails supported by the hinge are disposed so as to be pivotally moved against the lip portion of the semiconductor carrier. Flexible arms disposed through the hinge support are attached to the pivotable pressure rails so as to be able to move them against the top exposed lip portion of the carrier. Additionally, means are provided for lockably engaging these arms so as to ensure continuous pressure being applied to the land grid array module.
Accordingly, it is an object of the present invention to provide a mechanism for insuring electrical and mechanical contact between a land grid array module and its corresponding socket.
It is also an object of the present invention to provide a semiconductor packaging mechanism which provides a land grid array module engagement mechanism for which removability of the land grid array module is readily available.
It is a still further object of the present invention to provide a semiconductor package and packaging mechanism which provides access to an LGA module for purposes of providing either a heatsink or a direct lid attachment to the module.
It is yet another object of the present invention to provide a mechanism for more easily removing thermal energy from semiconductor chip modules, particularly LGA modules.
It is a still further object of the present invention to provide a semiconductor packaging and engagement mechanism for which mechanical stresses have been reduced.
It is also an object of the present invention to provide an LGA interconnection mechanism for producing relatively large compressive forces to maintain electrical contact throughout a card/socket/module assembly.
It is yet another object of the present invention to eliminate the utilization of bulky pressure plate devices employed in LGA engagement mechanisms.
It is still another object of the present invention to eliminate tensile, compressive and shear stresses on sensitive semiconductor module components including silicon ships, chip carriers, chip underfill material, adhesives and thermal compounds found in semiconductor packaging systems.
It is yet another object of the present invention to eliminate stresses in LGA packaging which tend to produce bulk material fractures and material creep.
Lastly, but not limited hereto, it is an object of the present invention to provide an LGA packaging mechanism for high power electronic circuit chips and modules.
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Kastberg Eric
Zitz Jeffrey
Blecker Ira D.
International Business Machines - Corporation
Ngo Ngan V.
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