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ELECTRICAL ASSEMBLY WITH INTERNAL
MEMORY CIRCUITIZED SUBSTRATE
HAVING ELECTRONIC COMPONENTS
POSITIONED THEREON, METHOD OF
MAKING SAME, AND INFORMATION 5
HANDLING SYSTEM UTILIZING SAME
TECHNICAL FIELD
The present invention relates to circuitized substrates, and 10 more particularly to composite circuitized structures such as printed circuit boards (PCBs) and the like adapted for having electronic components such as chip carriers and semiconductor chips positioned thereon. Such structures, when including these added components, will be referred to herein 15 as electrical assemblies, but may have alternative names in the industry. The present invention also relates to methods for fabricating such structures, and to information handling systems (e.g., computers, servers, etc.) utilizing such assemblies. 20
CROSS REFERENCE TO CO-PENDING
APPLICATION
In Ser. No. 10/900,385 entitled "CIRCUITIZED SUB- 25 STRATE WITH INTERNAL ORGANIC MEMORY DEVICE, METHOD OF MAKING SAME, ELECTRICAL ASSEMBLY UTILIZING SAME, AND INFORMATION HANDLING SYSTEM UTILIZING SAME", filed concurrently herewith under there is defined a circuitized substrate 30 which includes as part thereof an internal memory device capable of being electrically coupled to external electrical components (e.g., a logic semiconductor chip).
BACKGROUND OF THE INVENTION 35
A conventional procedure for forming known laminate circuitized substrates (e.g., PCB) structure includes forming layers of dielectric material and electrically conducting material to provide multiple layers of circuits and voltage 40 planes. Circuits can be discrete wiring patterns known as signal planes. Voltage planes can be either ground plane or power planes, and are sometimes collectively referred to as power planes. In one technique of forming such structures, layers of dielectric material and conductive material are 45 successively applied, e.g., the dielectric material is applied and then circuits or voltage planes are provided thereon and, typically, thru-holes (described in greater detail hereinbelow) are formed, typically by drilling or etching. This method relies on each successive step of adding additional 50 structure and the circuitry layers are formed individually, e.g., in each step in forming the plane having circuit traces or formed power planes. This requires precision drilling to form the plated thru-holes (PTHs) all of which is time consuming, especially where there are a large number of 55 drilled holes required to form PTHs.
Methods have been described that provide a relatively inexpensive photolithographic technique of forming a composite laminate structure (substrate assembly) from individual discrete laminate structures (substrates). For 60 example, see U.S. Pat. No. 6,593,534 entitled "Printed Wiring Board Structure With Z-Axis Interconnections" and filed Mar. 19, 2001. See also U.S. Pat. No. 6,388,204 (Lauffer et al) and U.S. Pat. No. 6,479,093 (Lauffer et al), the teachings of which are incorporated herein by reference. 65
Multilayered structures such as double-sided PCBs often necessitate the provision of the aforementioned thru-holes
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between the various conductive layers or sides of the board. This is commonly achieved by providing metallized, conductive thru-holes in the board which communicate with the sides and layers requiring electrical interconnection. For some applications, it is desired that electrical connection be made with almost if not all of the conductive layers. In such a case, thru-holes are also typically provided through the entire thickness of the board. For these, as well as other applications, it is often desired to also provide electrical connection between the circuitry on one face of the board and one or more of the inner circuit layers. In those cases, "blind vias", passing only part way through the board are provided. In still another case, such multilayered boards often require internal "vias" which are located entirely within the board's structure and covered by external layering, including both dielectric and conductive. Such internal "vias" are typically formed within a sub-part structure of the final board and then combined with other layers during final lamination of the board. For purposes of this application, therefore, the term "thru-hole" is meant to include such conductive openings that pass entirely through the board (plated thru- holes or PTHs), "blind vias" which extend from an external surface of the board into a specified conductive layer of the board, as well as "internal vias" which is internally "captured" by the board's outer layers.
PCB and other substrate complexities have increased significantly over the past few years, due primarily to increased operational requirements for the products in which these substrates are utilized. For example, boards for mainframe computers may have as many as 36 layers of circuitry or more, with the complete stack having a thickness of about 0.250 inch (or 250 mils). These boards are typically designed with three or five mil wide signal lines and twelve mil diameter thru-holes. For increased densification in many of today's PCBs, the industry seeks to reduce signal lines to a width of two mils or less and thru-holes to a diameter of two mils or less. As will be defined herein in greater detail, a primary feature of the instant invention is the provision of a circuitized substrate possessing much greater operational capabilities than such substrates and electrical assemblies utilizing same known in the art. A specific feature of the invention is the inclusion of one or more organic memory devices within the substrate itself, thereby eliminating the need for externally mounted components of this type, thus saving more surface space for components such as hotter operating logic semiconductor chips and the like to even further increase the final product's operational capabilities. Yet another feature is the connection of this memory device to at least one of the external electrical components and the connection of this component to another located nearby on the substrate's external surface.
U.S. Pat. No. 6,704,207, entitled "Device and Method for Interstitial Components in a Printed Circuit Board", issued Mar. 9, 2004, describes a printed circuit board (PCB) which includes a first layer having first and second surfaces, with an above-board device (e.g., an ASIC chip) mounted thereon. The PCB includes a second layer having third and fourth surfaces. One of the surfaces can include a recessed portion for securedly holding an interstitial component. A "via", electrically connecting the PCB layers, is also coupled to a lead of the interstitial component. The described interstitial components include components such as diodes, transistors, resistors, capacitors, thermocouples, and the like. In what appears to be the preferred embodiment, the interstitial component is a resistor having a similar size to a "0402" resistor (manufactured by Rohm Co.), which has a thickness of about 0.014 inches.
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U.S. Pat. No. 6,242,282, entitled "Circuit Chip Package and Fabrication Method", issued Jun. 5, 2001, describes a method for packaging a chip which includes the steps of providing an interconnect layer including insulative material having a first side and a second side, initial metallization patterned on second side metallized portions of the second side and not on second side non-metallized portions of the second side, a substrate via extending from the first side to one of the second side metallized portions, and a chip via extending from the first side to the second side non-metallized portion. The method also includes positioning a chip on the second side with a chip pad of the chip being aligned with the chip via, and patterning connection metallization on selected portions of the first side of the interconnect layer and in the via so as to extend to the second side metallized portion and to the chip pad. A "substrate" or other dielectric material is molded about the chip.
U.S. Pat. No. 6,084,306, entitled "Bridging Method of Interconnects for Integrated Circuit Packages", issued Jul. 4, 2000, describes an integrated circuit package having first and second layers, a plurality of routing pads being integral with the first layer, a plurality of upper and lower conduits, respectively, disposed on the upper and lower surfaces of the first layer, one of the upper conduits electrically connected to one of the lower conduits, a plurality of pads disposed on the second layer, vias that electrically connect the pads to the lower conduits and a chip adhered to the second layer having bonding pads, at least one of which is electrically connected to one of the routing pads.
U.S. Pat. No. 5,831,833, entitled" Bare Chip Mounting Printed Circuit Board and a Method of Manufacturing Thereof by Photo-etching", issued Nov. 3, 1998, describes a method of manufacturing a "bare chip" multi-layer printed circuit board in which arbitrary numbers of wiring circuit conductor layers and insulating layers are alternately stacked on one or both surfaces of a printed circuit board as a substrate, and a recessed portion with an upper opening capable of mounting and resin-encapsulating a bare chip part is formed on the surface of the printed circuit board. In what appears to be the preferred embodiment, one of the insulating layers is made from a photosensitive resin, and the bare chip part mounting recessed portion is formed by photoetching the insulating layer made from the photosensitive resin.
U.S. Pat. No. 5,426,263, entitled "Electronic Assembly Having a Double-sided Leadless Component", issued Jun. 20, 1995, describes an electronic assembly which has a double-sided leadless component and two printed circuit boards. The component has a plurality of electrical terminations or pads on both opposing major surfaces. Each of the printed circuit boards has a printed circuit pattern that has a plurality of pads that correspond to the electrical terminations on both sides of the double-sided leadless component. The electrical terminals on one side of the component are attached to the pads on the first board and the electrical terminals on the other side of the leadless component are attached to the pads on the second board. The printed circuit boards are joined together to form a multilayered circuit board so that the double-sided leadless component is buried or recessed inside. The component is attached to the pads of the printed circuit board using solder.
U.S. Pat. No. 5,280,192, entitled "Three-dimensional Memory Card Structure With Internal Direct Chip Attachment", issued Jan. 18,1994, describes a card structure which includes an internal three dimensional array of implanted semiconductor chips. The card structure includes a power core and a plurality of chip cores. Each chip core is joined
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to the power core on opposite surfaces of the power core, and each chip core includes a compensator core having a two dimensional array of chip wells. Each chip well allows for a respective one of the semiconductor chips to be implanted
5 therein. A compliant dielectric material is disposed on the major surfaces of the compensator core except at the bottoms of the chip wells. The compliant dielectric material has a low dielectric constant and has a thermal coefficient of expansion compatible with those of the semiconductor chips
10 and the compensator core, so that thermal expansion stability with the chips and the compensator core is maintained.
U.S. Pat. No. 5,099,309, entitled "Three-dimensional Memory Card Structure With Internal Direct Chip Attachment", issued Mar. 24, 1992, describes a memory card
15 structure containing an embedded three dimensional array of semiconductor memory chips. The card structure includes at least one memory core and at least one power core which are joined together in an overlapping relationship. Each memory core comprises a copper-invar-copper (CIC) thermal con
20 ductor plane having a two dimensional array of chip well locations on each side of the plane. Polytetrafluoroethylene (PTFE) covers the major surfaces of the thermal conductor plane except at the bottoms of the chip wells. Memory chips are placed in the chip wells and are covered by insulating
25 and wiring levels. Each power core comprises at least one CIC electrical conductor plane and PTFE covering the major surfaces of the electrical conductor plane. Provision is made for providing electrical connection pathways and cooling pathways along vertical as well as horizontal planes internal
30 to the card structure.
U.S. Pat. No. 5,016,085, entitled "Hermetic package for integrated circuit chips, issued May 14, 1991, describes a hermetic package which has an interior recess for holding a semiconductor chip. The recess is square and set at 45
35 degrees with respect to the rectangular exterior of the package. The package uses ceramic layers which make up the package's conductive planes with the interior opening stepped to provide connection points. The lowest layer having a chip opening therein may be left out of the
40 assembly to provide a shallower chip opening recess.
U.S. Pat. No. 4,956,694, entitled "Integrated circuit chip stacking", issued Sep. 11, 1990, describes a device for increasing the density of integrated circuit chips on a printed circuit board. A plurality of integrated circuits are packaged
45 within chip carriers and stacked, on one top of the other, on a printed circuit board. Each of the input/output data terminals, power and ground terminals of the chips are connected in parallel. Each chip is individually accessed by selectively enabling the desired chip.
50 The above patents illustrate that various methods have been implemented for more closely "bonding" electronic components such as semiconductor chips and a substrate as one integral assembly, including the use of chip "recesses" with an appropriate cover or like material and, more spe
55 cifically, as seen in two of these patents (U.S. Pat. Nos. 5,099,309 and 5,280,192), use of internal chip placement and coupling amongst the substrate's layered structure itself.
The present invention represents a significant advancement over the above structures and methods by providing a
60 new and unique circuitized substrate in which one or more organic memory devices are integrally formed as part of the substrate's mutilayered structure and capable of effectively operating in conjunction with other components such as a logic semiconductor chip located externally of the substrate.
65 The resulting electrical assembly, which also provides coupling of the electrical component connected to the internal memory device to other electrical components in a manner
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