Stack of multilayer modules with heat-focusing metal layer

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of electronics packaging, and in particular, to high-density electronic modules for housing and interconnecting electronic components located on stacked substrate layers.

2. Description of the Related Art

Increasing the volume density of electronic packaging is crucial for reducing device sizes for a given functionality. Efforts to provide high-density electronic packaging have included three-dimensional stacking technology in an attempt to avoid the inherent geometric constraints of standard two-dimensional semiconductor integrated circuits ("ICs"). By stacking electronic modules on top of one another and providing interconnections between the modules, the multiple layers can provide additional circuit elements without extending the two-dimensional footprint beyond that of a single module. Certain embodiments have also included heat-conducting, electrically insulating layers to improve heat dissipation during operation of these stacked electronic modules.

Numerous packaging schemes have been developed for stacking silicon-based ICs to increase the volume densities of electronic devices. However, while the silicon wafers of the silicon-based ICs provide rigidity and stability for the electronic elements, the ultimate volume densities of the multilayer stacks are inherently limited due to the thicknesses of the silicon wafers. Lapping off excess silicon from the back side of silicon wafers before stacking has been used to decrease the thickness of the silicon layers, and hence increase the number of layers per unit height. However, this procedure is time-consuming and requires precise machining to avoid damaging the circuit elements.

SUMMARY OF THE INVENTION

In accordance with one aspect of an embodiment of the invention, a stack of multilayer modules has a segmentation layer disposed between neighboring multilayer modules. The segmentation layer facilitates the separation of neighboring multilayer modules. The stack of multilayer modules comprises a first multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The stack of multilayer modules further comprises a second multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second multilayer module is disposed to be neighboring the first multilayer module. The stack of multilayer modules further comprises at least one segmentation layer between the first and second multilayer modules. The segmentation layer comprises a metal layer and at least one thermoplastic adhesive layer. When heat is applied, the metal layer conducts heat to the thermoplastic adhesive layer.

In accordance with another aspect of an embodiment of the invention, a method releasably adheres together neighboring multilayer modules of a stack of multilayer modules. The method comprises providing a first multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises providing a second multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second multilayer module is disposed to be neighboring the first multilayer module. The method further comprises disposing a segmentation layer between the first multilayer module and second multilayer module. The segmentation layer comprises a metal layer and a thermoplastic adhesive layer. When heat is applied, the metal layer conducts heat to the thermoplastic adhesive layer.

In accordance with another aspect of an embodiment of the invention, each multilayer module of a stack of multilayer modules has a plurality of layers wherein each layer has a substrate therein. The stack of multilayer modules comprises a first multilayer module comprising a first layer having a top side and bottom side. The first layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The stack of multilayer modules further comprises a second multilayer module comprising a second layer having a top side and bottom side. The second layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The stack of multilayer modules further comprises a metal layer disposed between and adhered to the top side of the first layer and the bottom side of the second layer. The first multilayer module is releasably adhered to the second multilayer module.

In accordance with another aspect of an embodiment of the invention, a method provides a stack of multilayer modules. Each multilayer module has a plurality of layers wherein each layer has a substrate therein. The method comprises providing a first multilayer module comprising a first layer having a top side and bottom side. The first layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises providing a second multilayer module comprising a second layer having a top side and bottom side. The second layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises adhering a metal layer to the top side of the first layer and the bottom side of the second layer. The method further comprises releasably adhering the first multilayer module to the second multilayer module with the metal layer disposed between the first multilayer module and the second multilayer module.

In accordance with another aspect of an embodiment of the invention, each multilayer module of a stack of multilayer modules has a plurality of layers wherein each layer has a substrate therein. The plurality of multilayer modules comprises a first multilayer module comprising a first layer having a top side and bottom side. The first layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The plurality of multilayer modules further comprises a second multilayer module comprising a second layer having a top side and bottom side. The second layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The plurality of multilayer modules further comprises a thermoplastic adhesive disposed between the top side of the first layer and the bottom side of the second layer. The first multilayer module is releasably adhered to the second multilayer module.

In accordance with another aspect of an embodiment of the invention, a method provides a stack of multilayer modules. Each multilayer module has a plurality of layers wherein each layer has a substrate therein. The method comprises providing a first multilayer module comprising a first layer having a top side and bottom side. The first layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises providing a second multilayer module comprising a second layer having a top side and bottom side. The second layer comprises a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises releasably adhering the first multilayer module to the second multilayer module by disposing a thermoplastic adhesive between the top side of the first layer and the bottom side of the second layer.

In accordance with another aspect of an embodiment of the invention, a stack of multilayer modules has a segmentation layer disposed between neighboring multilayer modules. The segmentation layer facilitates the separation of neighboring multilayer modules. The stack of multilayer modules comprises a first multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The stack of multilayer modules further comprises a second multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second multilayer module is disposed to be neighboring the first multilayer module. The stack of multilayer modules further comprises at least one segmentation layer between the first and second multilayer modules. The segmentation layer comprises a plurality of metal layers and at least one thermoplastic adhesive layer. When heat is applied, the metal layers conducts heat to the thermoplastic adhesive layer.

In accordance with another aspect of an embodiment of the invention, a method provides a stack of multilayer modules with a segmentation layer disposed between neighboring multilayer modules. The method comprises providing a first multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises providing a second multilayer module comprising a plurality of active layers each comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second multilayer module is disposed to be neighboring the first multilayer module. The method further comprises releasably adhering the first multilayer module and the second multilayer module by disposing at least one segmentation layer between the first and second multilayer modules. The segmentation layer comprises a plurality of metal layers and at least one thermoplastic adhesive layer. When heat is applied, the metal layers conducts heat to the thermoplastic adhesive layer.

In accordance with another aspect of an embodiment of the invention, a stack of multilayer modules has a segmentation layer disposed between neighboring multilayer modules. The segmentation layer facilitates the separation of neighboring multilayer modules. The stack of multilayer modules comprises a first multilayer module comprising a first active layer comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The stack of multilayer modules further comprises a second multilayer module comprising a second active layer comprising a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second active layer is disposed to be neighboring the first active layer. The stack of multilayer modules further comprises at least one segmentation layer between the first and second active layers. The segmentation layer comprises a metal layer and at least one thermoplastic adhesive layer. When heat is applied, the metal layer conducts heat to the thermoplastic adhesive layer.

In accordance with another aspect of an embodiment of the invention, a method separates a stack of releasably adhered multilayer modules. The method comprises providing a first multilayer module releasably adhered to a second multilayer module by disposing a heat-separating layer between the first and second multilayer modules. The first multilayer module comprises a first layer with a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The second multilayer module comprises a second layer with a substrate, at least one electronic element, and a plurality of electrically-conductive traces. The method further comprises applying heat to the heat-separating layer, thereby releasing the first multilayer module from the second multilayer module. The method further comprises separating the first multilayer module from the second multilayer module.

In accordance with another aspect of an embodiment of the invention, a stack of multilayer modules comprises means for stacking the multilayer modules. The stack of multilayer modules further comprises means for releasably adhering neighboring multilayer modules to one another upon heating. The stack of multilayer modules further comprises means for conducting heat to said means for releasably adhering neighboring multilayer modules to one another.

For the purposes of summarizing the invention, certain aspects, advantages and novel features of the invention have been described herein above. It is to be understood, however, that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B schematically illustrates a multilayer module compatible with an embodiment of the invention having a top layer and a bottom layer.

FIG. 2 schematically illustrates a partial exploded view of the multilayer module schematically illustrated in FIG. 1.

FIG. 3 is a flowchart describing a method of fabricating multilayer modules compatible with an embodiment of the invention.

FIG. 4 schematically illustrates a portion of an active layer sheet compatible with an embodiment of the invention.

FIG. 5 schematically illustrates a registration tool comprising alignment posts which engage registration holes of the active layer sheets and segmentation layer sheets to align the sheets in preparation of lamination.

FIG. 6 is a flowchart describing the process of preparing and adding additional active layer sheets.

FIG. 7 schematically illustrates a portion of a segmentation layer sheet compatible with an embodiment of the invention.

FIG. 8 is a flowchart describing the process of preparing and adding the segmentation layer sheet.

FIG. 9 schematically illustrates a laminated stack of arrays of multilayer modules.

FIG. 10 schematically illustrates an individual stack of multilayer modules obtained after dividing the laminated stack of arrays illustrated in FIG. 9.

FIG. 11 is a flowchart describing the process of preparing the sides of the stack of multilayer modules and forming electrically-conductive lines along the sides.

FIG. 12 schematically illustrates the stack of multilayer modules after the sides have been metallized.

FIG. 13 schematically illustrates the stack of multilayer modules after the excess metallization has been removed, leaving the electrically-conductive lines.

FIG. 14 schematically illustrates the stack of multilayer modules in position within a segmentation tool prior to segmenting the stack into individual multilayer modules.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 schematically illustrate a multilayer module 10 compatible with an embodiment of the invention having a top layer 12 and a bottom layer 14. FIG. 2 is a partial exploded view of the multilayer module 10 schematically illustrated in FIG. 1. The multilayer module 10 comprises a plurality of flexible active layers 20. Each active layer 20 comprises a non-electrically-conductive first substrate 22 with an edge 24, at least one electronic element 26, and a plurality of electrically-conductive traces 28 which provide electrical connection from the edge 24 of the first substrate 22 to the electronic element 26. The active layers 20 are laminated together so that the edges 24 of the first substrates 22 form a side 30 of the multilayer module 10 and the traces 28 of the active layers 20 are aligned in registry with one another.

The multilayer module 10 further comprises a plurality of electrically-conductive lines 32 along the side 30 of the multilayer module 10, the lines 32 providing electrical connection to the traces 28. The multilayer module 10 further comprises at least one flexible segmentation layer 40 laminated to the active layers 20. The segmentation layer 40 comprises a non-electrically-conductive second substrate 42 and a thermally-conductive material 44. The segmentation layer 40 is either the top layer 12 or the bottom layer 14 of the multilayer module 10. The embodiment illustrated in FIGS. 1 and 2 has a segmentation layer 40 as the top layer 12 with the thermally-conductive material 44 on the outward top surface of the multilayer module 10.

In one embodiment of the invention, the non-electrically-conductive first substrate 22 of each active layer 20 comprises a polymeric material. Examples of suitable polymeric materials for the first substrate 22 include, but are not limited to, polyimide film such as Kapton.RTM., which is available from E.I. du Pont de Nemours and Company of Wilmington, Del., or a benzocyclobutene (BCB)-based polymer dielectric such as Cyclotene.RTM., which is available from Dow Chemical Company of Midland, Mich.

The dimensions of the active layers 20 are not critical but are dependent on the desired functionality and packaging size constraints for the multilayer module 10. In the embodiment illustrated in FIGS. 1 and 2, the active layers 20 are approximately 1".times.1" and 0.002" thick. In other embodiments, the thickness of the active layers 20 is preferably between approximately 0.0005" to approximately 0.006", more preferably between approximately 0.0005" to approximately 0.005", and most preferably between approximately 0.0005" to approximately 0.003".

The electronic element 26 of each active layer 20 comprises a polymeric material which is appropriately doped and patterned, typically by photolithographic techniques, to form conductors, insulators, diodes, transistors, memory cells, or other electronic components of the electronic element 26. In certain embodiments, the electronic element 26 can be formed within the first substrate 22 by modification of certain regions of the first substrate 22 by doping or other techniques. In certain other embodiments, the electronic element 26 can be formed on a top side of the active layer 20, or a bottom side of the active layer 20, or on both the top and bottom sides of the active layer 20.

The electrically-conductive traces 28 of each active layer 20 can comprise metallization or a conductive polymeric material, which is patterned onto the first substrate 22. The electrically-conductive traces 28 provide electrical connection between the electronic element 26 and an edge 24 of the first substrate 22. Additionally, in embodiments in which the traces 28 comprise a conductive polymeric material, the traces 28 can be formed within the first substrate 22 by modification of certain regions of the first substrate 22 by doping or other techniques.

As will be described more fully below, the active layers 20 are laminated and held together by an adhesive 50 applied to one or both sides of the active layer 20. In certain embodiments, the bottom side of one active layer 20 is adhered to the top side of another active layer 20. In certain embodiments, the thickness of the combination of two active layers 20 is preferably less than or equal to approximately 0.005", and more preferably between approximately 0.001" and approximately 0.005".

The number of active layers 20 depends on the desired functionality and packaging size constraints for the multilayer module 10. However, the upper limit on the number of active layers 20 which can comprise a multilayer module 10 is effectively limitless. For the embodiment illustrated in FIGS. 1 and 2, the multilayer module 10 comprises 16 active layers 20. In certain embodiments, the active layers 20 are substantially similar to one another and are laminated in registry with one another so that the traces 28 of each active layer 20 are aligned with the corresponding traces 28 of the other active layers 20. In such an embodiment, each active layer 20 can differ from the other active layers 20 by each having a uniquely positioned trace 28 corresponding to an enable bit of the electronic element 26. This registry between the active layers 20 simplifies the process of providing outside interconnects to the electronic elements 26 of the multilayer modules 10, as described below.

The active layers 20 are laminated together so that the edges 24 of the first substrates 22 form the electrical contact sides 30 of the multilayer module 10. At least one side 30 of the multilayer module 10 is formed by edges 24 which have the electrically-conductive traces 28. Such sides 30 have electrically-conductive lines 32 to provide electrical connection to the electronic element 26 of the active layers 20 via the traces 28. As described more fully below, in certain embodiments, the lines 32 are deposited metallization which extend across the side 30 of the multilayer module 10, electrically connecting similar traces 28 of the various active layers 20. Examples of suitable metallizations for the lines 32 include, but are not limited to, gold over titanium, gold over tungsten, copper, and nickel.

The multilayer module 10 further comprises at least one flexible segmentation layer 40 comprising a non-electrically-conductive second substrate 42 and a thermally-conductive material 44. The second substrate 42 of the segmentation layer 40 can comprise a polymeric material. Examples of suitable polymeric materials for the second substrate 42 include, but are not limited to, Kapton.RTM., Cyclotene.RTM., and Zenite.RTM. liquid crystal polymer (LCP) resin, which is available from E.I. du Pont de Nemours and Company of Wilmington, Del. In certain embodiments, the second substrate 42 of the segmentation layer 40 comprises the same polymeric material as do the first substrates 22 of the active layers 20. In addition, the segmentation layer 40 can have generally the same dimensions as do the active layers 20. In certain embodiments, the segmentation layer 40 is the top layer 12 of the multilayer module 10 as illustrated in FIGS. 1 and 2. In other embodiments, the segmentation layer 40 is the bottom layer 14 of the multilayer module 10. In still other embodiments, the multilayer module 10 may have segmentation layers 40 as both the top layer 12 and the bottom layer 14.

The thermally-conductive material 44 is typically a metallic sheet deposited onto one surface of the second substrate 42 of the segmentation layer 40. Other configurations of the thermally-conductive material 44, such as a grid, are also compatible with an embodiment of the invention. Examples of suitable thermally-conductive materials 44 include, but are not limited to, metals or metal alloys such as copper, aluminum, and nickel, semiconductors such as silicon, silicon carbide, and diamond, and other materials such as aluminum nitride. In certain embodiments, the thermally-conductive material 44 is a copper-clad layer approximately 0.35 mils