High density integrated circuit module with complex...

Details High density integrated circuit module with complex... High density integrated circuit module with complex...

1999-06-30

2001-09-11

Gaffin, Jeffrey (Department: 2841)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S735000, C361S760000, C361S773000, C361S810000, C361S813000, C257S669000, C257S686000, C257S693000, C257S723000

Reexamination Certificate

active

06288907

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high-density, integrated circuit module, which includes a plurality of stacked individual integrated circuit devices including complex geometric or serpentine interconnect rails for selectively interconnecting leads of the stacked integrated circuit devices to each other and to external circuitry, which includes strain relief.
2. Discussion of the Related Technology
One method of achieving an ultra high density integrated circuit module, which includes stacked individual integrated circuit devices, is to use external electrical interconnect rails to interconnect electrical leads extending from the stacked individual integrated circuit devices within the module. This method and high density module is described in U.S. Pat. Nos. 5,279,029 and 5,367,766, which are assigned to the common assignee of the present invention and are incorporated by reference herein for all purposes.
In applications where the high density integrated circuit module includes dissimilar integrated circuit devices, e.g. memory devices, microprocessor, DMA device, etc., or where the lead-to-lead spacing of individual devices is not uniform, there is a need for a non-linear signal path that provides selectable electrical interconnections between the dissimilar integrated circuit devices which make up the module.
In previous methods and apparatus for electrically interconnecting the leads of stacked integrated circuit devices within a high density module, the electrical interconnect rails associated with these prior art devices are typically linear, i.e. the leads in each respective column of leads in the stack of packages are electrically and thermally interconnected to a single linear rail. Thus, making an electrical connection only between alternating leads in a particular column of leads in the stack, or only between leads of every third or fourth device in the stack, is very, difficult. Leads from integrated circuit devices which are not to be electrically connected to the linear rails must be trimmed internally or externally so as to not contact the rail or, at the very least, bent away from the rails so a solder connection between the rails and the leads is not made. This requires a more complex and costly manufacturing process.
Previous methods which use non-linear rail interconnections, such as those described in application Ser. No. 08/377,578, entitled “High Density Integrated Circuit Module With Complex Electrical Interconnect Rails”, assigned to the common assignee of the present invention and incorporated herein for all purposes, use non-linear rails having apertures formed therein for receiving leads to be connected to the non-linear rail. However, the non-linear rail is wider at the aperture portion than at other portion along the rail, since the aperture is completely surrounded by the rail. In applications where the lead centers of integrated circuit devices in the stacked module are closer together, the relatively large width of the rails at the apertures may make it more difficult to route additional non-linear rails between adjacent rails if the rails completely surround the aperture, thereby creating a more narrow space between adjacent rails.
Thus, the need exists for a non-linear rail design which enables complex electrical rails to be routed between adjacent rails as lead centers of devices get more narrow.
SUMMARY OF INVENTION
The present invention provides a method and apparatus for selectively interconnecting leads of individual integrated circuit devices stacked within a high density integrated circuit module. The electrical interconnections are made by rails of the present invention which have a non-linear complex geometric, or serpentine-shape, so as to be readily adapted to selectively interconnect with leads from selected packages within each stack in complex patterns.
It is also a feature of the present invention that the complex rail assembly may be formed much like conventional lead frames used for internal die connections. That is, the rail assembly of the present invention may be formed out of copper sheet metal stock having shorting bars supporting individual conductors or rails until the bars are sheared in final assembly. This method is particularly advantageous in those more complex applications when the rails are narrow and closely spaced.
The serpentine configured rails weave around leads of integrated circuit devices within the module that are not to be connected to that particular rail. Because of this, manufacturing becomes simplified since integrated circuit leads that are not to be connected will not have to be trimmed or otherwise removed and accidental undesired solder connections between unselected leads and the rail will be reduced. However, in applications where the lead centers of devices in the stacked module are closer together, the relatively large width of the rails at the portion of the rails which completely surround the apertures formed therein for receiving leads of devices to be interconnected, may make it more difficult to route other non-linear rails between adjacent rails if the aperture portion of adjacent rails are close together. Therefore, in selected rails, the portion of the rail in proximity to certain apertures in the rail is formed so the rail forms a partial aperture for receiving a selected lead. This provides for greater clearance between adjacent rails so the additional selected non-linear rails can be routed therebetween.
In a case where the high density integrated circuit module includes several SRAM devices, a DMA device, a microprocessor, and other assorted integrated circuit devices, a particular serpentine rail is electrically connected to only to address or data leads of selected integrated circuit devices within the module. It is in these applications where stacks, or modules, made up of dissimilar integrated circuit devices are used, or in applications where lead-to-lead spacing between individual devices is not uniform, that the non-linear serpentine rail configuration is desired.
In addition to the methods described above for increasing the ability of routing additional selected non-linear rails between adjacent rails, the leads of a TSOP device may be straightened and then partially cut to decrease the lead width which increases the gap between adjacent rails. Using this method, additional selected non-linear rails may be routed between adjacent rails, allowing for selected electrical interconnection of leads within the module.
The present invention also provides for strain relief for electrical connections made between the lead/rail electrical connection and the connection of the bottom portion of a rail to an underlying circuit board, or substrate.


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Catalog of Dense-Pac Microsystems, Inc. describing two products: DPS512X16A3 Ceramic 512K X 16 CMOS SRAM MODULE and DPS512X16AA3 High Speed Ceramic 512K X 16 CMOS SRAM Module, pp. 865-870.

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