Patent Application
20050253246
This invention relates generally to packaging integrated circuits.
Integrated circuits, such as microprocessors, may be packaged in various configurations. One such configuration is called a land grid array package. With land grid array packaging, integrated circuit die may be coupled to circuit boards through sockets that electrically and mechanically couple the integrated circuit die to the circuit board. In some cases, the connection may be via socket spring fingers which contact lands on the integrated circuit packages to make a land grid array connection system.
Often, a number of components may be connected together to form a stack. In one example a voltage regulator module board may be assembled on a motherboard through a land grid array connector. The voltage regulator module and motherboard are clamped together between a bolster plate under the motherboard. A heat sink may be positioned on top of the voltage regulator module board. Pairs of standoffs on the bolster plate are used to control the space in between the bolster plate and the heat sink.
Due to the dimensional tolerances of the mechanical parts, the distance between the bolster plate and the heat sink varies on individual assembly. Part of this stack tolerance can be absorbed by the flexibility of the land grid array springs. However, the bending range of land grid array springs is limited and cannot absorb the entire stack tolerance.
In the meantime, a certain level of pressure is required to press the land grid array onto the land pads on the motherboard to meet the requirement of good electrical design.
Thus, there is a need for better ways to connect integrated circuits to boards in the form of stacks.
Referring to
In some embodiments, the spring plate 24 provides the required pressing load on the back of the board 18 and thereafter on the land grid array connector 16, while absorbing the stack tolerance. As mentioned above, due to the dimensional tolerance of the mechanical parts, the distance between the bolster plate 22 and the heat sink 12 may vary on individual assembly. While part of this tolerance can be absorbed by the flexibility of the land grid array connector springs, the entire tolerance cannot be so absorbed. Thus, the spring plate 24 may function to absorb that tolerance. In some embodiments, the spring plate can supply a recovery force while reducing or even minimizing the tilting or uneven contact of the land grid array connector 16 on the board 18.
To this end, the spring plate 24 may include two or more pairs of independent spring legs 32 as shown in
A set of four spring legs 32 may be positioned on the center bar 34 of the spring plate 24 in one embodiment. The spring legs 32 may be partially cut out of the rest of the plate 24 and may be bent upwardly, towards the board 18, as the spring legs extend away from the center bar 34. The free ends 40 of the spring legs 32 may be bent over to prevent gouging of the mating surfaces. The span in the spring legs 32 may be less than half of the plate 24 width in some embodiments.
Clips 26 and 28 may be provided to ease assembly. For example, in one embodiment, the clips 28 extend downwardly from one half of the plate 24 while the clips 26 extend upwardly from the other half of the plate 24, as shown in
In some embodiments of the present invention, the spring plate 24 provides a low profile spring to absorb the stack tolerance while maintaining the desired pressure force in a limited space.
The spring legs 32 may be made by cutting and forming sheet metal in one embodiment of the present invention. For example, stamping may be utilized for this purpose.
The free ends 40 of the spring legs 32 are closer to the edges of the plate 24, while the lower ends sit closer to the plate center bar 34. The free ends 40 contact the object being supported. Larger spacing may be achieved between the free ends 40 due to this configuration which can supply a recovery force to reduce or minimize the tilting of the connector 16 relative to the board 18.
The height of the free ends 40 depends on the application and may be minimized to maintain a low profile in some embodiments. The free state height can be no larger than 10 percent of the plate 24 width in one embodiment of the present invention. The preload height can be less than one millimeter in one embodiment of the present invention. The use of the rounded free ends 40 may avoid any concentrated contact and scratching of other components in some embodiments.
The spring plate 24 uses a closed design as shown in
Alternatively, an opened design may be utilized in the plate 24a as shown in
In one embodiment of the present invention, the length of each spring leg 32 may be 16 millimeters and the span of the spring leg may be 4 millimeters. The free state height of the raised end 40 may be 1.5 millimeters with a plate thickness of 0.4 millimeters in such an embodiment. Such a structure can absorb a working stack tolerance range of about 0.6 millimeters, while maintaining the total pressing force at greater than 40 pounds.
Referring to
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
