Multiple die package

[0001] This application is a division of U.S. patent application Ser. No. 10/796,246 (MIO 0069 VA/99-1058), filed Mar. 9, 2004, which is related to a division of U.S. patent application Ser. No. 09/804,051 (MIO 0069 PA/99-1058), filed Mar. 12, 2001, which is related to U.S. patent application Ser. No. 09/992,580 (MIO 0072 VA/00-0785.01), filed Nov. 16, 2001 and Ser. No. 10/229,968 (MIO 0072 NA/00-0785.02), filed Aug. 28, 2002, which applications are a division and continuation of U.S. patent application Ser. No. 09/804,421 (MIO 0072 PA/00-0785), filed Mar. 30, 2001, now U.S. Pat. No. 6,441,483. This application is also related to U.S. patent application Ser. No. 10/229,969 (MIO 0080 VA/99-1053.01), filed Aug. 28, 2002, which is a division of U.S. patent application Ser. No. 09/855,731 (MIO 0080 PA/99-1053), filed May 15, 2001, now U.S. Pat. No. 6,507,107. This application is also related to U.S. Patent Application Serial No. 09/803,045 (99-1046), filed Mar. 12, 2001, now U.S. Pat. No. 6,469,376 and U.S. patent application Ser. No. 09/972,649 (99-1046.01), filed Oct. 10, 2001, and Ser. No. 10/175,291 (99-1046.02), filed Jun. 20, 2002, which both claim the benefit of Ser. No. 09/803,045.

[0002] The present invention relates to stacked multiple die semiconductor assemblies, printed circuit board assemblies, computer systems, and their methods of assembly. More particularly, the present invention relates to an improved scheme for increasing semiconductor die density.

[0003] Conventional Chip On Board (COB) techniques used to attach semiconductor dies to a printed circuit board include flip chip attachment, wirebonding, and tape automated bonding (“TAB”). Flip chip attachment consists of attaching a flip chip to a printed circuit board or other substrate. A flip chip is a semiconductor chip that has a pattern or array of electrical terminations or bond pads spaced around an active surface of the flip chip for face down mounting of the flip chip to a substrate. Generally, the flip chip has an active surface having one of the following electrical connectors: Ball Grid Array (“BGA”)—wherein an array of minute solder balls is disposed on the surface of a flip chip that attaches to the substrate (“the attachment surface”); Slightly Larger than Integrated Circuit Carrier (“SLICC”)—which is similar to a BGA, but having a smaller solder ball pitch and diameter than a BGA; or a Pin Grid Array (“PGA”)—wherein an array of small pins extends substantially perpendicularly from the attachment surface of a flip chip. The pins conform to a specific arrangement on a printed circuit board or other substrate for attachment thereto.

[0004] With the BGA or SLICC, the solder or other conductive ball arrangement on the flip chip must be a mirror-image of the connecting bond pads on the printed circuit board such that precise connection is made. The flip chip is bonded to the printed circuit board by refluxing the solder balls. The solder balls may also be replaced with a conductive polymer. With the PGA, the pin arrangement of the flip chip must be a mirror-image of the pin recesses on the printed circuit board. After insertion, the flip chip is generally bonded by soldering the pins into place. An under-fill encapsulant is generally disposed between the flip chip and the printed circuit board for environmental protection and to enhance the attachment of the flip chip to the printed circuit board. A variation of the pin-in-recess PGA is a J-lead PGA, wherein the loops of the J's are soldered to pads on the surface of the circuit board.

[0005] Wirebonding and TAB attachment generally begin with attaching a semiconductor chip to the surface of a printed circuit board with an appropriate adhesive, such as an epoxy. In wirebonding, bond wires are attached, one at a time, to each bond pad on the semiconductor chip and extend to a corresponding lead or trace end on the printed circuit board. The bond wires are generally attached through one of three industry-standard wirebonding techniques: ultrasonic bonding--using a combination of pressure and ultrasonic vibration bursts to form a metallurgical cold weld; thermocompression bondingBusing a combination of pressure and elevated temperature to form a weld; and thermosonic bondingBusing a combination of pressure, elevated temperature, and ultrasonic vibration bursts. The semiconductor chip may be oriented either face up or face down (with its active surface and bond pads either up or down with respect to the circuit board) for wire bonding, although face up orientation is more common. With TAB, ends of metal leads carried on an insulating tape such as a polyamide are respectively attached to the bond pads on the semiconductor chip and to the lead or trace ends on the printed circuit board. An encapsulant is generally used to cover the bond wires and metal tape leads to prevent contamination.

[0006] Higher performance, lower cost, increased miniaturization of components, and greater packaging density of integrated circuits are ongoing goals of the computer industry. As new generations of integrated circuit products are released, the number of devices used to fabricate them tends to decrease due to advances in technology even though the functionality of these products increases. For example, on the average, there is approximately a 10 percent decrease in components for every product generation over the previous generation with equivalent functionality.

[0007] In integrated circuit packaging, in addition to component reduction, surface mount technology has demonstrated an increase in semiconductor chip density on a single substrate or board despite the reduction of the number of components. This results in more compact designs and form factors and a significant increase in integrated circuit density. However, greater integrated circuit density is primarily limited by the space or “real estate” available for mounting dies on a substrate, such as a printed circuit board.

[0008] U.S. Pat. Nos. 5,994,166 and 6,051,878, the disclosures of which are incorporated herein by reference, represent a number of schemes for increasing semiconductor chip density on a single substrate or board. Despite the advantages of the most recent developments in semiconductor fabrication there is a continuing need for improved schemes for increasing semiconductor die density in printed circuit board assemblies.

[0009] This need is met by the present invention wherein an improved semiconductor die assembly scheme is provided. In accordance with one embodiment of the present invention, a multiple die semiconductor assembly is provided comprising first and second semiconductor dies and an intermediate substrate. The first semiconductor die defines a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. An intermediate substrate is positioned between the first semiconductor die and the second semiconductor die such that a first surface of the intermediate substrate faces the first semiconductor die and such that a second surface of the intermediate substrate faces the second semiconductor die. The intermediate substrate defines a passage there through. One of the first semiconductor die and the second semiconductor die is positioned such that the conductive bond pad on one of the first and second active surfaces is aligned with the passage.

[0010] In accordance with yet another embodiment of the present invention, at least one decoupling capacitor may be conductively coupled to one or both of the first and second semiconductor dies. The thickness dimension of the decoupling capacitor is accommodated in a space defined by a thickness dimension of the first semiconductor die, the second semiconductor die, a topographic contact conductively coupled to the first semiconductor die, or a topographic contact conductively coupled to the second semiconductor die.

[0011] In accordance with yet another embodiment of the present invention, a heat sink including a cap portion and a peripheral portion may be provided. The cap portion is thermally coupled to a major surface of at least one of the first and second semiconductor dies. The peripheral portion engages a mounting zone defined by a lateral dimension of the intermediate substrate extending beyond a periphery of at least one of the first and second semiconductor dies.

[0012] In accordance with yet another embodiment of the present invention, a multiple die semiconductor assembly is provided comprising first and second semiconductor dies and an intermediate substrate. The first semiconductor die defines a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. The intermediate substrate is positioned between the first active surface of the first semiconductor die and the second active surface of the second semiconductor die such that a first surface of the intermediate substrate faces the first active surface and such that a second surface of the intermediate substrate faces the second active surface. The first semiconductor die is electrically coupled to the intermediate substrate by at least one topographic contact extending from the first active surface to the first surface of the intermediate substrate. The intermediate substrate defines a passage there through. The second semiconductor die is secured to the second surface of the intermediate substrate such that the conductive bond pad of the second semiconductor die is aligned with the passage. The second semiconductor die is electrically coupled to the intermediate substrate by at least one conductive line extending from the conductive bond pad of the second semiconductor die through the passage defined in the intermediate substrate and to a conductive contact on the first surface of the intermediate substrate.

[0013] In accordance with yet another embodiment of the present invention, a multiple die semiconductor assembly is provided comprising first and second semiconductor dies, an intermediate substrate, and an additional substrate. The first semiconductor die defines a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. The intermediate substrate is positioned between the second semiconductor die and the first active surface of the first semiconductor die such that a first surface of the intermediate substrate faces the first active surface and such that a second surface of the intermediate substrate faces the second semiconductor die. The intermediate substrate defines a passage there through. The first semiconductor die is secured to the first surface of the intermediate substrate such that the conductive bond pad of the first semiconductor die is aligned with the passage. The first semiconductor die is electrically coupled to the intermediate substrate by at least one conductive line extending from the conductive bond pad of the first semiconductor die through the passage defined in the intermediate substrate and to a conductive contact on the second surface of the intermediate substrate. The additional substrate is positioned such that a first surface of the additional substrate faces the second active surface of the second semiconductor die. The additional substrate defines an additional passage there through. The second semiconductor die is secured to the first surface of the additional substrate such that the conductive bond pad of the second semiconductor die is aligned with the additional passage. The second semiconductor die is electrically coupled to the additional substrate by at least one conductive line extending from the conductive bond pad of the second semiconductor die through the additional passage defined in the additional substrate and to a conductive contact on a second surface of the additional substrate.

[0014] In accordance with yet another embodiment of the present invention, a multiple die semiconductor assembly is provided comprising first and second semiconductor dies, and an intermediate substrate. The first semiconductor die defines a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. The intermediate substrate is positioned between the first active surface of the first semiconductor die and the second active surface of the second semiconductor die such that a first surface of the intermediate substrate faces the first active surface and such that a second surface of the intermediate substrate faces the second active surface. The first semiconductor die is electrically coupled to the intermediate substrate by one or more topographic contacts extending from the first active surface to the first surface of the intermediate substrate. The second semiconductor die is electrically coupled to the intermediate substrate by one or more topographic contacts extending from the second active surface to the second surface of the intermediate substrate.

[0015] In accordance with yet another embodiment of the present invention, a printed circuit board assembly is provided comprising first and second semiconductor dies, an intermediate substrate, and a printed circuit board. The first semiconductor die defines a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. The intermediate substrate is positioned between the first semiconductor die and the second semiconductor die such that a first surface of the intermediate substrate faces the first semiconductor die and such that a second surface of the intermediate substrate faces the second semiconductor die. The intermediate substrate defines a passage there through. Either the first semiconductor die or the second semiconductor die is positioned such that the conductive bond pad on one of the first and second active surfaces is aligned with the passage. The printed circuit board is positioned such that a first surface of the printed circuit board faces the intermediate substrate. A plurality of topographic contacts extend from the intermediate substrate to the first surface of the printed circuit board.

[0016] In accordance with yet another embodiment of the present invention, a computer system is provided comprising a programmable controller and at least one memory unit. The memory unit comprises a printed circuit board assembly comprising first and second semiconductor dies, an intermediate substrate, and a printed circuit board. The first semiconductor die defining a first active surface including at least one conductive bond pad. The second semiconductor die defines a second active surface including at least one conductive bond pad. The intermediate substrate is positioned between the first semiconductor die and the second semiconductor die such that a first surface of the intermediate substrate faces the first semiconductor die and such that a second surface of the intermediate substrate faces the second semiconductor die. The intermediate substrate defines a passage there through. Either the first semiconductor die or the second semiconductor die is positioned such that the conductive bond pad on one of the first and second active surfaces is aligned with the passage. The printed circuit board is positioned such that a first surface of the printed circuit board faces the intermediate substrate. A plurality of topographic contacts extend from the intermediate substrate to the first surface of the printed circuit board.

[0017] In accordance with yet another embodiment of the present invention, a method of stacking a plurality of semiconductor die is provided comprising the steps of: providing a first semiconductor die defining a first active surface, the first active surface including at least one conductive bond pad; providing a second semiconductor die defining a second active surface, the second active surface including at least one conductive bond pad; positioning an intermediate between the first active surface of the first semiconductor die and the second active surface of the second semiconductor die such that a first surface of the intermediate substrate faces the first active surface and such that a second surface of the intermediate substrate faces the second active surface; electrically coupling the first semiconductor die to the intermediate substrate by at least one topographic contact extending from the first active surface to the first surface of the intermediate substrate; securing the second semiconductor die to the second surface of the intermediate substrate such that the conductive bond pad of the second semiconductor die is aligned with a passage formed through the intermediate substrate; electrically coupling the second semiconductor die to the intermediate substrate by at least one conductive line extending from the conductive bond pad of the second semiconductor die through the passage defined in the intermediate substrate and to a conductive contact on the first surface of the intermediate substrate; positioning a printed circuit board such that a first surface of the printed circuit board faces the second surface of the intermediate substrate and such that the second semiconductor die is positioned between the printed circuit board and the intermediate substrate; and forming a plurality of topographic contacts extending from the second surface of the intermediate substrate to the first surface of the printed circuit board.

[0018] In accordance with yet another embodiment of the present invention, a method of stacking a plurality of semiconductor die is provided comprising the steps of: providing a first semiconductor die defining a first active surface, the first active surface including at least one conductive bond pad; providing a second semiconductor die defining a second active surface, the second active surface including at least one conductive bond pad; positioning an intermediate substrate between the second semiconductor die and the first active surface of the first semiconductor die such that a first surface of the intermediate substrate faces the first active surface and such that a second surface of the intermediate substrate faces the second semiconductor die; securing the first semiconductor die to the first surface of the intermediate substrate such that the conductive bond pad of the first semiconductor die is aligned with a passage formed in the intermediate substrate; electrically coupling the first semiconductor die to the intermediate substrate by at least one conductive line extending from the conductive bond pad of the first semiconductor die through the passage defined in the intermediate substrate and to a conductive contact on the second surface of the intermediate substrate; providing an additional substrate positioned such that a first surface of the additional substrate faces the second active surface of the second semiconductor die; securing the second semiconductor die to the first surface of the additional substrate such that the conductive bond pad of the second semiconductor die is aligned with an additional passage formed in the additional substrate; electrically coupling the second semiconductor die to the additional substrate by at least one conductive line extending from the conductive bond pad of the second semiconductor die through the additional passage defined in the additional substrate and to a conductive contact on a second surface of the additional substrate; positioning a printed circuit board such that a first surface of the printed circuit board faces the second surface of the additional substrate and such that the conductive line extends through a space defined between the second surface of the additional substrate and the first surface of the printed circuit board; and forming a plurality of topographic contacts extending from the second surface of the additional substrate to the first surface of the printed circuit board.

[0019] Accordingly, it is an object of the present invention to provide an improved semiconductor die assembly scheme. Other objects of the present invention will be apparent in light of the description of the invention embodied herein.

[0020] The following detailed description of the preferred embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which FIGS. 1-8 are cross sectional schematic illustrations of a variety of printed circuit board assemblies according to the present invention.

[0021] Referring initially to FIG. 1, a printed circuit board assembly 10 is provided comprising a first semiconductor die 20, a second semiconductor die 30, an intermediate substrate 40, a printed circuit board 50, and a pair of decoupling capacitors 60. As will be appreciated by those practicing the present invention, the printed circuit board assembly 10 is typically provided a part of a computer system. In specific applications of the present invention, the semiconductor dies may form an integrated memory unit but may embody a variety of alternative integrated circuit functions.

[0022] The first semiconductor die 20 defines a first active surface 22. The first active surface 22 includes one or more conductive bond pads 24. The second semiconductor die 30 defines a second active surface 32. The second active surface 32 including one or more conductive bond pads 34. For the purposes of describing and defining the present invention, it is noted that a conductive bond pad comprises a conductive surface area defined on or extending from a surface of a semiconductor die. A conductive contact comprises a conductive surface area defined on or extending from a substrate. An active surface comprises a surface of a die or substrate that contains conductive contacts or conductive bond pads.

[0023] The intermediate substrate 40 is positioned between the first active surface 22 of the first semiconductor die 20 and the second active surface 32 of the second semiconductor die 30 such that a first surface 42 of the intermediate substrate 40 faces the first active surface 22 and such that a second surface 44 of the intermediate substrate 40 faces the second active surface 32. For reasons illustrated in further detail herein, the intermediate substrate 40 defines a passage 45 extending from the first surface 42 of the intermediate substrate 40 to the second surface 44 of the intermediate substrate 40. The intermediate substrate 40 further includes a network of conductive contacts 46 formed thereon. As is described in further detail herein the conductive contacts 46, which may embody printed conductive lines, wires, traces, and combinations thereof, electrically couple the various components of the printed circuit board assembly 10 to the printed circuit board 50 and to each other. For the purposes of defining and describing the present invention when reference is made herein to electrical coupling to a substrate or other structure, it is understood that the electrical coupling includes electrical coupling to a contact on a surface of the substrate or other structure. It is also noted that electrical coupling need not be direct and may include coupling through one or more circuitry components.

[0024] In the embodiment illustrated in FIG. 1, the first semiconductor die 20 comprises a flip chip and is electrically coupled to the intermediate substrate 40 by a plurality of topographic contacts 12 extending from the first active surface 22 to the first surface 42 of the intermediate substrate 40. For the purposes of describing and defining the present invention, it is noted that a flip chip comprises a semiconductor die arranged relative to a substrate such that conductive bond pads included in an active surface thereof are aligned with conductive contacts on an opposing surface of the intermediate substrate. In the embodiment of FIG. 1, the conductive bond pads 24 included in the first active surface 22 are aligned with conductive contacts 46 on the first surface 42 of the intermediate substrate 40. It is further noted that a topographic contact comprises any conductive contact that extends between and defines a spacing between an active surface of a substrate or die and an active surface of another substrate or die. Examples include solder balls, conductive polymers, or other types of topographic electrical connections. A pin grid array, where pin recesses are provided in the opposing surface, present a suitable alternative to topographic contacts, where it is not necessary to create a spacing between two surfaces for accommodating structure there between.

[0025] Referring further to FIG. 1, the second semiconductor die 30 comprises a stacked chip secured to the second surface 44 of the intermediate substrate 40 such that the conductive bond pads 34 of the second semiconductor die 30 are aligned with the passage 45. The second semiconductor die 30 is electrically coupled to the intermediate substrate 40 by one or more conductive lines 48 extending from the conductive bond pad 34 of the second semiconductor die 30 through the passage 45 defined in the intermediate substrate 40 and to a conductive contact 46 on the first surface 42 of the intermediate substrate 40. For the purposes of describing and defining the present invention, it is noted that a stacked chip comprises a semiconductor die that is stacked upon a major surface of a substrate or that defines a major surface that is secured to a major surface of a substrate. A conductive line may comprise an electrically conductive lead, trace, bond wire, etc. A printed circuit board comprises a substrate upon which a circuit, network, or plurality of electrically conductive areas are formed.

[0026] It noted that the manner in which the first and second semiconductor dies 20, 30 are electrically coupled to the printed circuit board 50 may vary. For example, electrically conductive traces or other conductors may be provided in the intermediate substrate 40 such that one of the semiconductor dies 20, 30 may be electrically coupled to the intermediate substrate 40 through the other die or independent of the other die. It may be advantageous in particular applications of the present invention to electrically connect the first and second dies 20, 30 to each other or to electrically isolate the dies 20 and 30 from each other. In either case, suitable trace lines or other conductive lines are provided to at least ensure an electrical connection between each die and the printed circuit board 50.

[0027] The decoupling capacitors 60 are mounted to the first surface 42 of the intermediate substrate 40 and are conductively coupled to the first and second semiconductor dies 20, 30. Specifically, according to one aspect of the present invention, each decoupling capacitor 60 is placed in an electrical circuit between the high and low voltage inputs (e.g., V_SS and V_CC) of one of the dies 20, 30. In this manner, the decoupling capacitors 60 decouple the low voltage input from the high voltage input and serves as a power source filter or surge/spike suppressor. Preferably, each decoupling capacitor 60 is placed as close as possible or practical to the semiconductor dies 20, 30.

[0028] The thickness dimension a of each decoupling capacitor 60 is accommodated in a space defined by a thickness dimension b of the topographic contacts 12 conductively coupled to the conductive contact 46 on the first surface 42 of the intermediate substrate 40.

[0029] The printed circuit board assembly 10 illustrated in FIG. 1 may further comprise a conventional underfill material 14 formed between the first semiconductor die 20 and the first surface 42 of the intermediate substrate 40. As will be appreciated by those familiar with semiconductor fabrication underfill materials are generally disposed between flip chips and the printed circuit board or substrate to which they are mounted for enviromental protection and to enhance the attachment of the flip chip to the printed circuit board or substrate. In addition, an encapsulant 16 may be formed over the first semiconductor die 20 and the first surface 42 of the intermediate substrate 40. The encapsulant 16 may be used in place of the underfill material 14 and may also be formed over the second semiconductor die 30. A die attach adhesive 18 (illustrated in FIG. 8) may be positioned to secure the second semiconductor die 30 to the second surface 44 of the intermediate substrate 40. As will be appreciated by those practicing the present invention, the encapsulant and underfill configurations illustrated herein with reference to FIG. 1 may also be employed in the embodiments of FIGS. 2-8.

[0030] In the embodiment illustrated in FIG. 2, a heat sink 70 including a cap portion 72 and a peripheral portion 74 is provided. The cap portion 72 is thermally coupled to a major surface 25 of the first semiconductor die 20 via a layer of heat sink compound 76, which preferably provides some adhesion between the heat sink 70 and the die 20. The peripheral portion 74 engages a mounting zone defined by a lateral dimension of the intermediate substrate 40 extending beyond the periphery of the first semiconductor die 20.

[0031] In the embodiment of FIG. 3, the first semiconductor die 20 comprises a stacked chip secured to the first surface 42 of the intermediate substrate 40 such that the conductive bond pads 24 on the first active surface 22 are aligned with the passage 45. Conductive lines 48 extend from the conductive bond pads 24 on the first active surface 22 to conductive contacts 46 on the second surface 44 of the intermediate substrate 40. The second semiconductor die 30 comprises a flip chip arranged relative to the intermediate substrate 40 such that the conductive bond pads 34 included in the second active surface 32 are aligned with conductive contacts 46 on the second surface 44 of the intermediate substrate 40. Topographic contacts 12 extend between the conductive bond pads 34 of the second active surface 32 and the conductive contacts 46 of the second surface 44 of the intermediate substrate 40.

[0032] The arrangement of FIG. 7 is similar to that illustrated in FIG. 1, with the exception that the second semiconductor die 30 comprises a flip chip. As such, an additional set of topographic contacts 12 extend from the second active surface 32 to the second surface 44 of the intermediate substrate 40.

[0033] Referring now to FIGS. 4-6, an additional substrate 80 is positioned such that a first surface 82 of the additional substrate 80 faces the second active surface 32 of the second semiconductor die 30. The additional substrate 80 defines an additional passage 85 there through. The second semiconductor die 30 is secured to the first surface 82 of the additional substrate 80 such that conductive bond pads 34 of the second semiconductor die 30 are aligned with the additional passage 85. The second semiconductor die 30 is electrically coupled to the additional substrate 80 by conductive lines 88 extending from the conductive bond pads 34 of the second semiconductor die 30 through the additional passage 85 defined in the additional substrate 80 and to a conductive contact 86 on a second surface 84 of the additional substrate 80.

[0034] Referring specifically to FIG. 4, the assembly 10 further comprises a third substrate 90 positioned such that a first surface 92 of the third substrate 90 faces the second surface 84 of the additional substrate 80. The additional substrate 80 is electrically coupled to the third substrate 90 by topographic contacts 12 extending from the second surface 84 of the additional substrate 80 to a first surface 92 of the third substrate 90. A decoupling capacitor 60 is mounted to the first surface 92 of the third substrate 90. The thickness dimension of the decoupling capacitor 90 is accommodated in a space defined by a thickness dimension of the topographic contacts 12 extending from the second surface 84 of the additional substrate 80 to a first surface 82 of the third substrate 90.

[0035] Referring specifically to FIG. 5, the assembly 10 further comprises a third substrate 90 positioned such that a first surface 42 of the intermediate substrate 40 faces a second surface 94 of the third substrate 90. The intermediate substrate 40 is electrically coupled to the third substrate 90 by topographic contacts 12 extending from the second surface 94 of the third substrate 90 to the first surface 42 of the intermediate substrate 40. The decoupling capacitor 60 is mounted to the second surface 94 of the third substrate 90. As is illustrated in FIG. 5, the thickness dimension of the decoupling capacitor 60 and a thickness dimension of the first semiconductor die 20 are both accommodated in the space defined by the thickness dimension of the topographic contact 12 extending from the second surface 94 of the third substrate 90 to the first surface 42 of the intermediate substrate 40.

[0036] Referring specifically to FIG. 6, a pair of decoupling capacitors 60 are mounted to the first surface 42 of the intermediate substrate 40. The thickness dimension of the decoupling capacitors 60 is accommodated in a space defined by a thickness dimension of the first semiconductor die 20. The pair of decoupling capacitors 60 are mounted to the first surface 42 of the intermediate substrate 40. The first semiconductor die 20 is positioned between the pair of decoupling capacitors 60 relative to the first surface 42 of the intermediate substrate 40.

[0037] Referring finally to the embodiment of FIG. 8, it is noted that the intermediate substrate 40 may be provided with a cavity 100 defined therein. The dimensions of the cavity 100 are preferably selected to accommodate the second semiconductor die 30. In this manner, the overall thickness of the printed circuit board assembly 10 may be reduced, as compared with the other illustrated embodiments of the present invention. It is contemplated by the present invention that a cavity 100 may be provided in any of the substrates of any of the illustrated embodiments of the present invention without departing form the scope of the present invention. The depth of the cavity is defined by the thickness of the die to be accommodated therein.

[0038] Conventional stacking, soldering, bonding, under filling, encapsulating, curing, and other semiconductor processing techniques may be modified and arranged to yield the various stacked structures of the present invention. For the purposes of defining the assembly scheme of the present invention it is noted that any claims to a method of assembling a structure are not intended to be limited by the order in which specific process steps are recited in a claim. Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.