Abstract:
A system, method and apparatus for providing a printed circuit board having optimized power delivery planes and signal routing regions are disclosed. In one aspect, the present disclosure teaches a printed circuit board having two or more cores coupled together using a prepreg sheet having selected regions of increased permittivity. In combining the cores with the prepreg sheet, the regions of increased permittivity are preferably aligned with power delivery planes defined between respective cores. By increasing the permittivity within the power delivery planes, the greater the reduction in area of the cores needed for power delivery and the greater the area retained on the cores for providing signal routing. As a result, a printed circuit board incorporating teachings of the present disclosure may support more advanced and complex information handling system implementations.

Description:
TECHNICAL FIELD 
   The present disclosure relates generally to information handling systems and, more particularly, to optimizing power delivery and signal routing in information handling system printed circuit boards. 
   BACKGROUND 
   As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems. 
   As the performance requirements of information handling systems continue to increase, costs associated with printed circuit board (PCB) fabrication also increase. One reason for this increase in costs can be attributed to an increase in PCB complexity. As more signals are added to PCB designs, additional PCB layers are typically required to route those signals and deliver sufficient power to support their functionality. Some high performance system designs have resorted to routing signals on layers that are typically devoted to delivering power. The resulting reduction in available area on these power layers generally yields diminished power delivery performance which, under electrically stressful conditions, may compromise functionality of the entire system. In addition, validating the PCB power delivery, typically a time consuming process, is made considerably more difficult with marginal power delivery designs. As a result, if signal routing must be included on the power delivery layers of a PCB, novel approaches must be devised to mitigate the detrimental effect such routing typically has on power delivery performance. 
   SUMMARY 
   In accordance with teachings of the present disclosure, an information handling system for optimizing power delivery and signal routing on printed circuit board power planes is provided. The information handling system preferably includes a printed circuit board having first and second cores, at least one processor and a memory operably coupled to the processor and the printed circuit board. The printed circuit board preferably further includes a dielectric including glass particles disposed in a portion thereof, where the dielectric is operable to couple the first and second cores substantially parallel one another. 
   In addition, a printed circuit board for optimizing power delivery and signal routing is also provided. The printed circuit board preferably includes a first core, a second core and an insulating material having regions of increased permittivity. The insulating material is preferably operable to couple the first core to the second core where the regions of increased permittivity are disposed proximate at least one power plane defined between the first and second cores. 
   Further, a method for manufacturing an optimized power delivery and signal routing printed circuit board is provided. The printed circuit board preferably includes a first and a second core. The method for manufacturing the printed circuit board preferably includes integrating an insulating material having a first permittivity into at least a portion of a dielectric layer having a second permittivity. The method preferably also includes coupling the first and second cores together about the dielectric layer such that the insulating material integrated portions substantially align with a power delivery plane defined by at least a portion of the first and second cores. 
   In one aspect, teachings of the present disclosure provide the technical advantage of permitting regions of a printed circuit board to be optimized for power and signal routing. 
   In another aspect, teachings of the present disclosure provide the technical advantage of enabling more complex printed circuit board implementations by facilitating an increase in area available for signal routing without compromising effective power delivery. 
   Further, teachings of the present disclosure provide the technical advantages of a low-cost, efficient alternative to printed circuit board fabrication where regions of the circuit board may be selectively optimized for power delivery and signal routing. 
   In addition, teachings of the present disclosure provide the technical advantage of enabling variable capacitance power delivery planes, the capacitance of a selected power delivery plane determined by materials, spacing of materials, as well as other factors controlled by a multilayered printed circuit board fabricator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
       FIG. 1  is a block diagram showing an information handling system including a hybrid printed circuit board power delivery plane, according to teachings of the present disclosure; 
       FIG. 2  is a top view showing a woven fiberglass mesh, according to teachings of the present disclosure; 
       FIG. 3  is a side view of the woven fiberglass mesh of  FIG. 2 , according to teachings of the present disclosure; 
       FIG. 4  is a side view of an exemplary embodiment of a prepreg sheet, according to teachings of the present disclosure; 
       FIG. 5  is a side view showing an exemplary embodiment of a multilayered printed circuit board incorporating a hybrid power delivery plane and at least one signal trace, according to teachings of the present disclosure; and 
       FIG. 6  is an exploded view of an exemplary embodiment of multilayer printed circuit board fabrication, according to teachings of the present disclosure. 
   

   DETAILED DESCRIPTION 
   Preferred embodiments and their advantages are best understood by reference to  FIGS. 1 through 6 , wherein like numbers are used to indicate like and corresponding parts. 
   For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components. 
   Referring first to  FIG. 1 , a block diagram of an information handling system is shown, according to teachings of the present disclosure. Information handling system or computer system  10  preferably includes at least one microprocessor or central processing unit (CPU)  12 . CPU  12  may include processor  14  for handling integer operations and coprocessor  16  for handling floating point operations. CPU  12  is preferably coupled to cache  18  and memory controller  20  via CPU bus  22 . System controller I/O trap  24  preferably couples CPU bus  22  to local bus  26  and may be generally characterized as part of a system controller. 
   Main memory  28  of dynamic random access memory (DRAM) modules is preferably coupled to CPU bus  22  by a memory controller  20 . Main memory  28  may be divided into one or more areas such as system management mode (SMM) memory area (not expressly shown). 
   Basic input/output system (BIOS) memory  30  is also preferably coupled to local bus  26 . FLASH memory or other nonvolatile memory may be used as BIOS memory  30 . A BIOS program (not expressly shown) is typically stored in BIOS memory  30 . The BIOS program preferably includes software which facilitates interaction with and between information handling system  10  devices such as a keyboard (not expressly shown), a mouse (not expressly shown), or one or more I/O devices. BIOS memory  30  may also store system code (note expressly shown) operable to control a plurality of basic information handling system  10  operations. 
   Graphics controller  32  is preferably coupled to local bus  26  and to video memory  34 . Video memory  34  is preferably operable to store information to be displayed on one or more display panels  36 . Display panel  36  may be an active matrix or passive matrix liquid crystal display (LCD), a cathode ray tube (CRT) display or other display technology. In selected applications, uses or instances, graphics controller  32  may also be coupled to an integrated display, such as in a portable information handling system implementation. 
   Bus interface controller or expansion bus controller  38  preferably couples local bus  26  to expansion bus  40 . In one embodiment, expansion bus  40  may be configured as an Industry Standard Architecture (“ISA”) bus. Other buses, for example, a Peripheral Component Interconnect (“PCI”) bus, may also be used. 
   In a portable information handling system embodiment, Personal Computer Memory Card International Association (PCMCIA) controller  42  may also be included and is preferably coupled to expansion bus  40  as shown. PCMCIA controller  42  is preferably coupled to a plurality of information handling system expansion slots  44 . Expansion slots  44  may be configured to receive one or more PCMCIA expansion cards such as modems, fax cards, communications cards, and other input/output (I/O) devices. 
   Interrupt request generator  46  is also preferably coupled to expansion bus  40 . Interrupt request generator  46  is preferably operable to issue an interrupt service request over a predetermined interrupt request line in response to receipt of a request to issue interrupt instruction from CPU  12 . 
   I/O controller  48 , often referred to as a super I/O controller, is also preferably coupled to expansion bus  40 . I/O controller  48  preferably interfaces to an integrated drive electronics (IDE) hard drive device (HDD)  50 , CD-ROM (compact disk-read only memory) drive  52  and/or a floppy disk drive (FDD)  54 . Other disk drive devices (not expressly shown) which may be interfaced to the I/O controller include a removable hard drive, a zip drive, a CD-RW (compact disk-read/write) drive, and a CD-DVD (compact disk—digital versatile disk) drive. 
   Communication controller  56  is preferably provided and enables information handling system  10  to communicate with communication network  58 , e.g., an Ethernet network. Communication network  58  may include a local area network (LAN), wide area network (WAN), Internet, Intranet, wireless broadband or the like. Communication controller  56  may be employed to form a network interface for communicating with other information handling systems (not expressly shown) coupled to communication network  58 . 
   As illustrated, information handling system  10  preferably includes power supply  60 , which provides power to the many components and/or devices that form information handling system  10 . Power supply  60  may be a rechargeable battery, such as a nickel metal hydride (“NiMH”) or lithium ion battery, when information handling system  10  is embodied as a portable or notebook computer, an A/C (alternating current) power source, an uninterruptible power supply (UPS) or other power source. 
   Power supply  60  is preferably coupled to power management microcontroller  62 . Power management microcontroller  62  preferably controls the distribution of power from power supply  60 . More specifically, power management microcontroller  62  preferably includes power output  64  coupled to main power plane  66  which may supply power to CPU  12  as well as other information handling system components. Power management microcontroller  62  may also be coupled to a power plane (not expressly shown) operable to supply power to an integrated panel display (not expressly shown), as well as to additional power delivery planes preferably included in information handling system  10 . 
   Power management microcontroller  62  preferably monitors a charge level of an attached battery or UPS to determine when and when not to charge the battery or UPS. Power management microcontroller  62  is preferably also coupled to main power switch  68 , which the user may actuate to turn information handling system  10  on and off. While power management microcontroller  62  powers down one or more portions or components of information handling system  10 , e.g., CPU  12 , display  36 , or HDD  50 , etc., when not in use to conserve power, power management microcontroller  62  itself is preferably substantially always coupled to a source of power, preferably power supply  60 . 
   In a portable embodiment, information handling system  10  may also include screen lid switch or indicator  70  which provides an indication of when an integrated display is in an open position and an indication of when the integrated display is in a closed position. It is noted that an integrated panel display may be located in the same location in a lid (not expressly shown) of the computer as is typical for clamshell configurations of portable computers such as laptop or notebook computers. In this manner, the integrated display may form an integral part of the lid of the system, which swings from an open position to permit user interaction to a closed position. 
   Computer system  10  may also include power management chip set  72 . Power management chip set  72  is preferably coupled to CPU  12  via local bus  26  so that power management chip set  72  may receive power management and control commands from CPU  12 . Power management chip set  72  is preferably connected to a plurality of individual power planes operable to supply power to respective components of information handling system  10 , e.g., HDD  50 , FDD  54 , etc. In this manner, power management chip set  72  preferably acts under the direction of CPU  12  to control the power supplied to the various power planes and components of a system. 
   Real-time clock (RTC)  74  may also be coupled to I/O controller  48  and power management chip set  72 . Inclusion of RTC  74  permits timed events or alarms to be transmitted to power management chip set  72 . Real-time clock  74  may be programmed to generate an alarm signal at a predetermined time as well as to perform other operations. 
   Referring now to  FIGS. 2 and 3 , a top view and a side view of an exemplary embodiment of a woven fiberglass mesh are shown, respectively. As indicated generally in  FIG. 3 , fiberglass mesh  100  is preferably a woven fiberglass mesh and typical of an FR4-based prepreg sheet used in the manufacturing of printed circuit boards (PCB). In a preferred embodiment, the woven, fiberglass-based construction of a prepreg sheet results in an effective prepreg sheet dielectric constant based on the dielectric constants of both the selected woven fiberglass mesh and the resin or other adhesive material disposed on one or more sides thereof. 
   Referring now to  FIG. 4 , a side view of an exemplary embodiment of a prepreg sheet incorporating woven fiberglass mesh  100  of  FIGS. 2 and 3  is shown, according to teachings of the present disclosure. As illustrated, prepreg sheet  102  preferably includes woven fiberglass mesh  100  as well as adhesive layers  104  and  106  on respective sides of woven fiberglass mesh  100 . The material chosen for adhesive layers  104  and  106  may be varied, and may include, but is not limited to, one or more types of resin or resin compounds. According to teachings of the present disclosure, prepreg sheet  102  is one example of a dielectric or insulator operable to couple together a plurality of cores to form a multilayered printed circuit board. 
   As discussed above, prepreg sheet  102  may be constructed from woven fiberglass mesh  102  and adhesive layers  104  and  106 . Also as mentioned above, adhesive layers  104  and  106  may be formed from resin or another adhesive material according to teachings of the present disclosure. In one embodiment, adhesive layers  104  and  106  are preferably reprocessed such as by heating the prepreg sheet, such that one or more materials or compounds, such as a material component or compound having an increased or high permittivity, may be integrated, embedded, infused or otherwise incorporated therein. In an alternate embodiment, adhesive layers  104  and  106  preferably include an outer layer or surface subject to reprocessing and operable to receive and adhere one or more layers of one or more components or materials thereon. Alternate embodiments of a PCB hybrid power delivery plane disclosed in teachings of the present disclosure may employ dielectrics of other materials. Examples of dielectric materials include, but are not limited to, polyimide, Teflon, Kevlar, Kapton and Pyralux flexible laminates. 
   Referring now to  FIG. 5 , a side view of an exemplary embodiment of a multilayered printed circuit board incorporating teachings of the present disclosure is shown. As illustrated in  FIG. 5 , multilayered PCB  108  preferably includes cores  110  and  112  coupled to adhesive layers  104  and  106  of prepreg sheet  102 , respectively. As shown, core  110  preferably includes insulator or dielectric  114  disposed between copper layers  116  and  118 . Similarly, core  112  preferably includes insulator or dielectric  120  disposed between copper layers  122  and  124 . In some instances, the combination of prepreg sheet  102  with cores  110  and  112  may be referred to as a panel. Depending on the complexity of PCB to be designed, copper layers  116  and  122  of cores  110  and  112 , respectively, may be coupled to one or more additional cores using one or more additional prepreg sheets. 
   Multilayer printed circuit boards, such as multilayered PCB  108 , are often used to implement and support complex information handling system or computer designs. In such implementations, the various copper layers are typically etched, patterned or otherwise subdivided to serve varying purposes throughout the multilayered PCB. Typically, the copper layers of a multilayered printed circuit board are often divided into one or more powered delivery planes as well as into a plurality of signal routing traces. For example, as illustrated in  FIG. 5 , copper layer  124  is divided into a region defined by power delivery plane section  126  and first and second signal routing traces  128  and  130 , respectively. In general, those portions dedicated to power delivery planes are typically employed to distribute power from a power source coupled to the multilayered printed circuit board, such as power source  60  of  FIG. 1 , to the various components mounted or included thereon. Also in such implementations, the plurality of signal routing traces included in one or more copper layers of a multilayered printed circuit board may be employed to communicate signals generated or received by one or more components between the various components included or integrated thereon. 
   According to teachings of the present disclosure, power delivery planes and signal routing traces of a multilayered printed circuit board may be optimized such that the availability of signal routing traces may be maximized while the amount of a given copper layer necessary for proper or appropriate power delivery planes may be minimized. A hybrid power delivery plane incorporating teachings of the present disclosure will generally increase power delivery performance while retaining an area for signal routing traces. According to teachings of the present disclosure, power delivery plane performance can be enhanced by increasing the capacitance between adjacent power and ground regions of a multilayered printed circuit board power delivery plane. An exemplary embodiment of a PCB hybrid power delivery plane board is shown generally in  FIG. 5 . 
   According to teachings of the present disclosure, a hybrid power delivery plane of multilayered PCB  108  is indicated generally at  132  and may be described as that area between and including copper layer  118  of core  110  and power delivery plane copper layer section  126  of core  112 . Prior to infusion, incorporation, mixing, embedding or otherwise implanting higher increased permittivity material  134  substantially within power plane region  132 , prepreg sheet  102  possesses a permittivity generally defined by the combination of its respective components, the permittivity of woven fiberglass mesh  100  and the permittivity of adhesive layers  104  and  106  here. As a result of infusing higher or increased permittivity material  134  substantially within power plane  132 , the overall permittivity of prepreg sheet  102  may be increased. As a result, with copper layer  118  serving as a ground plane and power delivery plane copper layer section  126  serving as the positive power plane, for example, the capacitance measure within power delivery plane  132  may be increased. As a result of this increased permittivity and corresponding increase in capacitance between the power and ground planes, the power delivery performance of power plane  132  is ultimately enhanced. 
   A variety of methodologies may be employed, according to teachings of the present disclosure, for increasing the permittivity and corresponding capacitance substantially within a power delivery plane of a multilayered PCB. In one embodiment, adhesive layers  104  and/or  106  may be reprocessed such that a selected amount of increased permittivity material  134 , such as glass particles, may be infused, embedded, incorporated, or combined therewith in selected regions. In another embodiment, increased permittivity material  134  may be adhered to a surface of one or more of adhesive layers  104  and  106  substantially within the desired power delivery plane regions prior to coupling prepreg sheet  102  with cores  110  and  112 . By selectively increasing the permittivity and capacitance in limited regions of a multilayered PCB, those regions designed for power delivery, such as power delivery plane  132 , may be reduced yet optimized while those areas designed for signal routing, such as the region embodying signal routing traces  128  and  130 , may be expanded and optimized. 
   In an embodiment of a multilayered PCB which couples cores  110  to  112  together with a dielectric or insulator other than prepreg sheet  102 , such a dielectric or insulator may also have desired regions thereof receive higher increased permittivity material  134 . Similar to the methodologies described above, such a dielectric or insulator may be reprocessed, heating for example, such that higher increased permittivity material  134  may be infused or incorporated therein. Such a dielectric or insulator material may also or alternatively be capable of having higher increased permittivity material  134  adhered to one or more exterior surfaces of the dielectric or insulator prior to combination of the dielectric or insulator with cores  110  and  112 . 
   As disclosed herein, a multilayered PCB having a plurality of power delivery planes optimized through varying the capacitance therebetween is contemplated. According to teachings of the present disclosure, the capacitance of a selected power delivery plane may be controlled by, at least, the selection of materials used to form the multilayer and PCB. As such, according to teachings of the present disclosure, a multilayered PCB having a plurality of power delivery planes and where one or more of the power delivery planes possesses a capacitance or permittivity value different from that of the other power delivery planes is contemplated. In one respect, teachings of the present disclosure provide for controlling and varying the capacitance in selected regions of a multilayered printed circuit board through, at least, controlling and varying the spacing between respective cores and copper layers, controlling and varying the materials used to join together cores and the materials selected for increasing the capacitance or permittivity in selected areas or regions of the multilayered PCB design, e.g., one or more power delivery planes. 
   Referring now to  FIG. 6 , an exploded view of an exemplary embodiment of a multilayered printed circuit board incorporating teachings of the present disclosure is shown. As illustrated in  FIG. 6 , multilayered PCB  150  preferably includes cores  152 ,  154 ,  156  and  158 . Core  152  preferably includes copper layers  160  and  162  coupled together using insulator or dielectric  164 . Core  154  preferably includes copper layers  166  and  168  coupled together using insulator or dielectric  170 . Core  156  preferably includes copper layers  172  and  174  coupled together using insulator or dielectric  176 . Similarly, core  158  preferably includes copper layers  178  and  180  coupled together using insulator or dielectric  182 . 
   Copper layer  162  of core  152  is preferably coupled to copper layer  166  of core  154  using prepreg sheet  184 . Copper layer  168  of core  154  is preferably coupled to copper layer  172  of core  156  using prepreg sheet  186 . Similarly, copper layer  174  of core  156  is preferably coupled to copper layer  178  of core  158  using prepreg sheet  188 . In one embodiment, preparing sheets  184 ,  186  and  188  are similar in composition and makeup to prepreg sheet  102  of  FIG. 4 . In addition, varying embodiments of multilayered PCB  150  may subject one or more of prepreg sheet  184 ,  186  and  188  to reprocessing such that one or more selected regions thereof may be optimized for power delivery planes and/or signal routings as desired. 
   As illustrated, multilayered PCB  150  is preferably manufactured as a hybrid power delivery plane printed circuit board. Beginning with prepreg sheet  184 , regions  190  and  192 , between copper layer  162  of core  152  and copper layer  166  of core  154 , are preferably included to create power planes  194  and  196 , respectively. Similarly, regions  198  and  200  of prepreg sheet  186  having high or increased permittivity material included therein preferably cooperate with copper layer  168  of core  154  and copper layer  172  of core  156  to create optimized hybrid power delivery planes  202  and  204 , respectively. Likewise, regions of increased permittivity  206 ,  208  and  210  of prepreg sheet  188  preferably cooperate with copper plate  174  of core  156  and copper plate  178  of core  158  to form optimized hybrid power delivery planes  212 ,  214  and  216 , respectively. 
   It should be noted that detail regarding the numerous signal pathways or signal routing traces component connection points, etc., of multilayered PCB  150  have been omitted from portions of the various FIGURES referenced above to avoid confusion and to focus discussion on concepts of the present disclosure. For example, one or more of the various copper layers of  FIG. 6  may typically include complex patterns of copper signal routing traces, power delivery planes, etc., prior to assembly of multilayered PCB  150 , such as signal routing traces  128  and  130 . Following assembly of a multilayered PCB incorporating teachings of the present disclosure, the multilayered PCB may have one or more vias disposed therein, be subject to more etching, copper deposition, tin sealing, lithographing, etc. 
   Although the disclosed embodiments have been described in detail, it should be understood that various changes, substitutions and alterations can be made to the embodiments without departing from their spirit and scope.