Patent Publication Number: US-2022223522-A1

Title: Apparatus and method for direct power delivery to integrated circuit package

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to power distribution, and more particularly, to direct power delivery to an integrated circuit package. 
     BACKGROUND 
     As ASIC (Application-Specific Integrated Circuit) process nodes advance and device power continues to increase, delivering requisite power is becoming more challenging. In conventional systems, power is typically transferred from a Point-of-Load (POL) to the ASIC through vias and planes internal to a printed circuit board, which has a number of drawbacks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective of a power delivery device electrically coupling power supply components on a printed circuit board to an integrated circuit package, in accordance with one embodiment. 
         FIG. 2  is a top view of the power delivery device, power supply components, and integrated circuit package of  FIG. 1 . 
         FIG. 3  is a cross-sectional schematic illustrating delivery of power from the power supply component to the integrated circuit package by the power delivery device, in accordance with one embodiment. 
         FIG. 4  is a top view of a multi-phase power supply coupled to the integrated circuit package with a power delivery device, in accordance with one embodiment. 
         FIG. 5  is a side view of the multi-phase power supply coupled to the integrated circuit package with a power delivery device comprising stacked conductors, in accordance with one embodiment. 
         FIG. 6  is a block diagram illustrating an example of power distribution through POL (Point-of-Load) modules, in accordance with one embodiment. 
         FIG. 7  is a flowchart illustrating an overview of a process for power delivery from the power supply component to the integrated circuit package with the power delivery device, in accordance with one embodiment. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Overview 
     In one embodiment, an apparatus generally comprises a connecting member configured for positioning on an upper surface of an integrated circuit package and a cable comprising a first end attached to the connecting member and a second end configured for electrically coupling with a power supply component. The connecting member is operable to position the cable for connection to the upper surface of the integrated circuit package to deliver power from the power supply component to the integrated circuit package with the power supply component and the integrated circuit package mounted on an upper surface of a printed circuit board. 
     In another embodiment, an apparatus generally comprises a printed circuit board, a plurality of power supply components mounted on a surface of the printed circuit board, an integrated circuit package mounted on the surface of the printed circuit board, a connecting member positioned on an upper surface of the integrated circuit package, and a plurality of cables coupled to the connecting member and operable to deliver power from the power supply components to the integrated circuit package. 
     In yet another embodiment, a method generally comprises positioning a connecting member on an upper surface of an integrated circuit package mounted on a printed circuit board, the connecting member attached to a cable, electrically coupling the cable to a POL (Point-of-Load) module, and delivering power from the POL module to the integrated circuit package through the cable. 
     Further understanding of the features and advantages of the embodiments described herein may be realized by reference to the remaining portions of the specification and the attached drawings. 
     Example Embodiments 
     The following description is presented to enable one of ordinary skill in the art to make and use the embodiments. Descriptions of specific embodiments and applications are provided only as examples, and various modifications will be readily apparent to those skilled in the art. The general principles described herein may be applied to other applications without departing from the scope of the embodiments. Thus, the embodiments are not to be limited to those shown but are to be accorded the widest scope consistent with the principles and features described herein. For purpose of clarity, details relating to technical material that is known in the technical fields related to the embodiments have not been described in detail. 
     In a conventional Point-of-Load (POL) to ASIC (Application-Specific Integrated Circuit) connection, power is transferred through vias and planes internal to a PCB (Printed Circuit Board) and ASIC package. This results in a number of drawbacks, including for example, efficiency loss due to IR drop of the PCB, vias, and ASIC package, and introduction of resistance and parasitic inductance. Also, there is limited space available for current carrying traces and vias, and PCB congestion often occurs due to a trade-off between heavy copper areas and large high-speed signals that need to break out of a BGA (Ball Grid Array) area. Thus, routing through the PCB sacrifices valuable space and may result in higher layer counts and expensive non-symmetric stack-ups to handle the higher current. Moreover, the current carrying traces that are thermally coupled to the PCB and ASIC substrate and die may result in excess heat and expose components near high current carrying planes to excessive thermal stress. Heat from internal planes also adds to the already high thermal energy of the ASIC as the heat couples to components on a top layer through the PCB to the package substrate. 
     The embodiments described herein provide power delivery from a power supply component (e.g., POL module) to an integrated circuit (e.g., ASIC) by bypassing power planes and vias in a PCB and internal to the ASIC package. As described in detail below, one or more cables (e.g., flexible bus bars) are attached to the ASIC package with a removable connecting member (e.g., stiffener ring) in order to carry power closer to the die. One or more embodiments provide simplified rework options, operates with existing cooling solutions, and enables a reduction in PCB layer count, while providing improved decoupling and space savings on surface layers of the PCB. For example, the embodiments may provide simplified disassembly, reworking, and reassembly of the ASIC package without desoldering an underside BGA of the integrated circuit package. One or more embodiments may be implemented, for example, for power delivery to a high-power ASIC (or other integrated circuit) with current requirements over 200 amps to provide a  3 : 1  improvement ratio in terms of loss due to power delivery from the POL to the ASIC die, as compared to conventional power delivery through the PCB, 
     The embodiments described herein may operate in the context of a data communications network including multiple network devices. The network may include any number of network devices in communication via any number of nodes (e.g., routers, switches, gateways, controllers, edge devices, access devices, aggregation devices, core nodes, intermediate nodes, power sourcing equipment, powered devices, or other network devices), which facilitate passage of data within the network. One or more of the network devices may comprise one or more power delivery devices described herein. The network device may further include any combination of memory, processors, power supply units, and network interfaces. 
     Referring now to the drawings, and first to  FIGS. 1 and 2 , a power delivery device is shown for delivering power from power supply components to an integrated circuit package, in accordance with one embodiment. In one embodiment, an apparatus  10  comprises a connecting member  12  configured for positioning on an upper surface  13  of an integrated circuit package  14  and a cable  15  comprising a first end  16   a  attached to the connecting member and a second end  16   b  configured for electrically coupling with a power supply component  17 . The connecting member  12  is operable to position the cable  15  on the upper surface  13  of the integrated circuit package  14  for delivering power from the power supply component  17  to the integrated circuit package with the power supply component and the integrated circuit package mounted on an upper surface  18  of a printed circuit board  19 . The cable  15  provides a direct connection for power delivery from the power supply component  17  (e.g., POL module) to the integrated circuit package  14  (e.g., ASIC package), while bypassing at least a portion of a power plane and vias in the PCB, thereby eliminating traces and vias used in conventional systems to route power from the POL module to the integrated circuit package and freeing up valuable space in the PCB that may be used for routing high-speed signals, for example. 
     In one embodiment, an apparatus comprises the printed circuit board  19 , a plurality of power supply components  17  mounted on the surface  18  of the printed circuit board, the integrated circuit package  14  mounted on the surface of the printed circuit board, the connecting member  12  positioned on the upper surface  13  of the integrated circuit package  14 , and a plurality of cables  15  attached to the connecting member and operable to deliver power from the power supply components to the integrated circuit package. 
     The connecting member  12  may comprise, for example, a rigid, generally flat and thin element such as a stiffener for positioning on the upper surface  13  of the integrated circuit package  14 . In one or more embodiments, the connecting member comprises a frame (e.g., rectangular or circular ring with a central opening or semicontinuous structure (e.g., bar, U-shaped bar) which may be formed from metal, plastic, or any other suitable material. In the example shown in  FIGS. 1 and 2 , the connecting member  12  comprises a ring with the cables  15  attached to three sides thereof for delivering power from three power supply components  17  to the integrated circuit package  14 . The connecting member  12  may be formed in any shape, size or thickness based on the number of connecting cables  15  and size or shape of the integrated circuit package  14 . The central opening of the ring  12  is configured for receiving one or more die  20 ,  22  mounted on a substrate  24  of the integrated circuit package  14 . For example, an ASIC  20  and one or more other die  22  (e.g., memory component) may be positioned within the central opening of the ring  12 . Any number of cables  15  may be affixed to the ring  12  (e.g., one or more cables on one or more sides of the ring). Three cables  15  are shown in  FIGS. 1 and 2 , however, any number of cables may be attached to the ring  12  for delivering power from any number of power supply components  17 . As described below, the connecting member  12  positions and secures the cable to a contact area on the upper surface  13  of the integrated circuit package  14 . 
     The cable  15  may comprise, for example, a flexible bus bar, semi-rigid flex type PCB, or any other type of cable having any size, thickness, diameter, or cross-sectional shape (e.g., round, rectangular). As described below, the cable  15  may have any number of conductors in any arrangement (e.g., interleaved, stacked). The cable  15  may be ordered to size or bent to adapt to various routing configurations, thereby providing flexibility as to the positioning of the power supply components  17  on the printed circuit board  19 . Bus bar dimensions may be increased to accommodate increased current, without any changes to the PCB. The cables  15  are preferably insulated for safety. For example, flex bus bar cables  15  may be insulated to provide safe handling with currents greater than 500 amps. The cable  15  is preferably configured to carry both power and return current and may be configured with additional electrical components (e.g., capacitors, power supply components, current sense resistors, and the like) integrated into the semi-rigid or flex cable design. 
     The first end  16   a  of the cable  15  may be connected to the upper surface  13  of the integrated circuit package  14  with a removable spring finger connection (e.g., conductive pads or pins) or any other suitable contacts or connector. The cable  15  is affixed underneath the connecting member  12 , which is configured to position and secure cable contacts to a voided conductive contact power plane on the uppermost buildup layers (upper surface) of the integrated circuit package  14 . 
     The second end  16   b  of the cable  15  is electrically coupled to the power supply component  17  through any suitable conductive element (e.g., substrate, trace, via, power plane, ground plane) on the surface of the PCB  19  or formed within the PCB. In the example shown in  FIGS. 1 and 2 , six screw terminals  26  extend through the cable  15  and into a substrate  27  of the power supply component  17 . In one example, power is transmitted from a power module through the substrate  27  to the screw terminals  26 . Screw tops  26  of the bus bar terminations may be covered with an insulator for safety. Any other low-loss removable power connector may also be used to electrically couple the cable to the power component. As described below with respect to  FIG. 3 , power may be transmitted within the power supply component or between a POL and the power connector through one or more planes  28  (e.g., power plane, ground plane) formed in one or more layers of the PCB. 
     Direct attachment of the cable  15  to the upper surface  13  of the integrated circuit package  14  provides a path from the power supply component  17  with lower resistance as compared to conventional routing of power from the POL to the ASIC through power planes in the PCB. Airflow over the cable  15  provides improved thermal performance and reduces thermal heating to PCB substrate and nearby components by eliminating power planes. Simplified rework of the ASIC is provided by removing the connecting member and cable assembly of the power delivery device  10  as a one piece removable assembly. 
     In one or more embodiments, the integrated circuit package  14  comprises a lidless package for direct thermal contact with a cooling element, as described below. The integrated circuit package  14  may comprise one or more components  20 ,  21  (e.g., ASIC, NPU (Network Processing Unit), memory (e.g., on-substrate memory, high-bandwidth memory), SerDes (Serializer/Deserializer), optical engine, photonic chip, or any other electronic component, optical component, chip, chiplet, die, and the like) mounted on the substrate  24  with or without a lid. As shown in  FIG. 1 , the integrated circuit package  14  may be mounted on the PCB  19  with a BGA  25  or other suitable connection. 
     The power supply component  17  may comprise a POL module that receives power from a power source (power supply or other power component) positioned on the printed circuit board or another circuit board. For example, the POL may receive power from a PSU (Power Supply Unit) through a backplane and power may be transmitted to the POL through one or more planes within the PCB and transferred through one or more vias to the POL module. 
     It is to be understood that the term “power supply component” as used herein may refer to any type of power supply, power converter, power regulator, or other power supply component, including for example, discrete POLs and modules or power delivery block-based voltage regulator designs. Also, it may be noted that the POLs may be single phase or multi-phase POLs that may work together to deliver one or more output. As described below with respect to  FIG. 6 , the term “POL module” as used herein may also refer to one component or portion of a POL (e.g., regulated POL), with a fixed POL located separately from the regulated POL and providing power through a power plane in the PCB, for example. 
     Also, it should be noted that the terms lower, upper, bottom, top, below, above, and the like, which may be used herein are relative terms dependent upon the orientation of the package and components and should not be interpreted in a limiting manner. These terms describe points of reference and do not limit the embodiments to any particular orientation or configuration. 
       FIG. 3  is a cross-sectional schematic illustrating a power delivery path through the power delivery device, in accordance with one embodiment. An integrated circuit package comprising a die  32  and substrate  38  is mounted on a PCB  39 . For simplification, only one cable  35  is shown in  FIG. 3 . The die  32  may be coupled to the substrate  38  and the integrated circuit package coupled to the PCB  39  through a solder ball connection (e.g., BGA)  31   a ,  31   b , respectively. A connecting member  34  and attached cable  35  of the power delivery device are positioned on an upper surface of the substrate  38  and coupled via a removable connector (e.g., spring fingers)  31   c.    
     As previously described, the cable  35  transmits power directly from a POL module  37  to the integrated circuit package. The cable  35  is electrically coupled to the power supply component with a power connector  33  (e.g., screw terminal). In the example shown in  FIG. 3 , the PCB  39  comprises a power plane  42   a  and ground plane  42   b  electrically coupling the POL  37  to the connector  33  through vias  41   a  and  41   b.    
     Arrows in  FIG. 3  illustrate a power delivery path from the power supply component (e.g., POL  37 , substrate  40 , and associated vias  41   a ,  41   b , and power plane  42   a ) through the power delivery device (power connector  33 , cable  35 , spring fingers  31   c ) to the integrated circuit package. In the example shown in  FIG. 3 , the POL  37  transmits power through via  41   a  and power plane  42   a  to via  41   b  electrically coupled to power connector (e.g., screw terminal)  33 . The power connector  33  may also be electrically coupled to the POL  37  through a ground plane  42   b , for example. In another example, power may be transmitted through a surface plane (substrate)  40  on a surface of the PCB  39 . 
     Details of power delivery from the cable  35  to the ASIC  32  are shown in a cutout view in  FIG. 3 . Power transmitted through the cable  35  passes through connector  31   c  to the substrate  38  of the integrated circuit package. Power passes through one or more power planes  36  and vias to the die  32 . By transmitting power to the upper surface of the substrate  38 , rather than to a lower surface at the PCB interface, current flowing through the integrated circuit package core and micro-vias is reduced, thereby prolonging the lifespan of the integrated circuit package. 
     It is to be understood that the electrical path shown in  FIG. 3  is only an example and other power connections through different arrangements of power planes, ground planes, vias, surface planes, substrates, or connectors may be used for power transfer between the power delivery device and POL or power delivery device and ASIC, without departing from the scope of the embodiments. As can be observed from  FIG. 3 , routing of power through the power delivery device opens up all of the PCB space below the cable  35  for other uses (e.g., transmittal of high-speed signals). 
     In the example shown in  FIG. 3 , a cooling element  30  (e.g., heat sink, vapor chamber, or cold plate (liquid, gas, or multi-phase based cooling)) is thermally coupled to the lidless die  32  and clamps the connecting member  34  and attached cable  35  to the integrated circuit package. The cooling element  30  is attached to the printed circuit board  39  with fasteners (e.g., spring loaded screws) (not shown in  FIG. 3 ). Attachment of the cooling element  30  to the PCB  39  provides sufficient downward force to clamp the cable  35  to the upper surface of the integrated circuit package. The cables are positioned so as not to interfere with the connection points between the cooling element  30  and the printed circuit board  39 . The power delivery device may easily be removed by first removing the cooling element  30  and then unplugging the cable connectors  31  from the upper surface of the integrated circuit package and removing the connecting member and attached cable. 
       FIG. 4  is a top view of a connecting member  43  and affixed semi-rigid flex cable coupled to an integrated circuit package  49 , in accordance with one embodiment. The connecting member comprises a stiffener ring  43  and the cable comprises the semi-rigid flex cable comprising a plurality of conductors  45   a ,  45   b ,  45   c  and integrated rigid PCB section  44  positioned adjacent to the ring  43 . In the example shown in  FIG. 4 , the ring  43  clamps the rigid portion  44  to the integrated circuit package  49 . In another example, the ring  43  may be replaced with the member  44  of the cable, which acts as the connecting member. 
     Multi-phase pulse power (Extended Safe Power (ESP)) is delivered to power components  47   a  (V 1 ),  47   b  (V 2 ), and  47   c  (V 3 ). Conductors  45   a ,  45   b ,  45   c  of the cable carry the three phases V 1 , V 2 , V 3 , along with reference voltage V REF . It is to be understood that the cable arrangement shown in  FIG. 4  is only an example and the cable may be configured for single-phase or multi-phase power delivery in an interleaved arrangement or another configuration. 
     As previously noted, the cable assembly may include one or more electrical components  46 . For example, the semi-rigid PCB type cable may be designed to include space to mount the electrical components  46  including, for example, decoupling capacitors, power supply components, current sense resistors, or any combination thereof, directly on the rigid section of the PCB  44  or flex cable, thereby minimizing board real estate and migrating these components closer to the load (e.g., ASIC die on integrated circuit package  49 ). The very close proximity of decoupling components to the die makes the high frequency decoupling provided by these components very effective. In the example shown in  FIG. 4 , seven decoupling capacitors  46   a  are positioned at various locations along the cable assembly. 
       FIG. 5  is a side view illustrating another example of a flexible cable  55  with stacked conductors (flex PCB stack-up), in accordance with one embodiment. A cooling element  50  is positioned over connecting member  52  affixed to the cable  55 . The cooling element  50  is thermally coupled to die  54   a  mounted on substrate  54   b  of the integrated circuit package. Power is provided to a POL module  57  mounted on PCB  59  by an ESP power source  58 . As shown in  FIG. 5 , a first end of the cable  55  is electrically coupled to an upper side of the substrate  54   b  of the integrated circuit package and a second end of the cable is electrically coupled to the POL module  57  at power connector  51 . In this example, the cable  55  carries three phases V 1 , V 2 , and V 3  on conductors  53   a ,  53   b ,  53   c  and reference voltage at  53   d  (as shown at cutout view in  FIG. 5 ). Decoupling capacitors (or other electrical components)  56  are attached to an upper and lower side of the cable near the first end of the cable. 
     As previously noted, a power supply component coupled to the cable may comprise a POL module, or a portion of a POL (e.g., regulated POL).  FIG. 6  is a block diagram illustrating an example of power distribution through a POL power supply located on a board  60 . Power is delivered at power source  62  to a plurality of POLs (POL modules (circuits), power supplies)  64   a ,  64   b ,  64   c ,  64   d . In one example, pulse power at a voltage greater than 100V (e.g., 108V, 380V) or any other suitable voltage, is delivered to the POL (or a fixed POL component). In another example, the power source  62  delivers 54 VDC (or any other suitable voltage (e.g., intermediate bus voltage level selected based on overall system efficiency, routeability, and cost)) to one or more POL modules. The fixed POL  64   a  transfers power (e.g., at 54 VDC or other voltage) to the regulated POL (POL converter, POL regulator)  64   b , which distributes power to integrated circuit  66  (e.g., ASIC or other die, chip, multi-chip module, and the like). The fixed POL  64   a  may be connected to the regulated POL  64   b  through a bus bar interconnect or any other suitable electrical connection. The regulated POL  64   b  may provide, for example 150 amp or greater output. 
     As described above with respect to  FIGS. 4 and 5 , ESP may be supplied to one or more of the POL modules. The term “ESP” or “pulse power” (also referred to as “pulsed power”) as used herein refers to power that is delivered in a plurality of voltage pulses (sequence of voltage pulses)  68   a  in which voltage varies between a very small voltage (e.g., close to 0V, 3V) during a pulse-off time  69   a  and a larger voltage (e.g., ≥12V) during a pulse-on time  69   b . High voltage pulse power (high voltage pulses) (e.g., &gt;56V, ≥60V, ≥300V) may be transmitted from power sourcing equipment (PSE) to a powered device (PD) for use in powering the powered device, whereas low voltage pulse power (low voltage pulses) (e.g., ˜12V, ˜24V, ≤30V, ≤56V) may be used over a short interval for start-up (e.g., initialization, synchronization, charging local energy storage, powering up a controller, testing, or any combination thereof). The pulse power may also be delivered in multiple phases, with the pulses offset from one another between phases to provide continuous power, as shown in the simplified voltage traces  68   b ,  68   c  of  FIG. 6 . 
     It is to be understood that the voltage, power, and current levels described herein are only provided as examples and power may be delivered at different levels (volts, amps, watts) than described herein without departing from the scope of the embodiments. 
       FIG. 7  is a flowchart illustrating an overview of a process for implementing the power deliver device described herein, in accordance with one embodiment. The connecting member  12  and attached cable  15  are mounted on the integrated circuit package  14  and the cable is coupled to the upper surface  13  of the integrated circuit package (step  70 ) ( FIGS. 1 and 7 ). This may include, for example, positioning the connecting member over the integrated circuit package and attaching the connector (e.g., spring fingers  31   c ) to the upper surface of the substrate  38  ( FIG. 3 ). The cable  15  is electrically coupled to the power supply component  17  mounted on the PCB  19  with the integrated circuit package  14  (step  72 ) ( FIGS. 1 and 7 ). For example, a power connector (e.g., screw terminals  26 ) may be connected to the power supply component  17  through a power plane within or on the PCB. Power is delivered from the power supply component  17  directly to the integrated circuit package  14  through the cable  15  (step  74 ). The cable  15  allows power to be delivered to the upper side  13  of the integrated circuit package  14 , thereby bypassing power planes and vias in the PCB and integrated circuit package. 
     It is to be understood that the process shown in  FIG. 7  and described above is only an example and steps may be added, modified, combined, or reordered without departing from the scope of the embodiments. 
     As can be observed from the foregoing, one or more embodiments described herein provide advantages over conventional power delivery systems. For example, one or more embodiments provide a reduced resistance POL to ASIC connection and an improvement in path resistance and path loss efficiency over conventional connection methods. The embodiments allow for higher amounts of power to be carried into an ASIC by reducing the power losses and parasitics encountered in a conventional power delivery system. By rerouting the current from PCB power planes, vias under the ASIC, ASIC attach, and most of the z-axis ASIC substrate, thermal coupling from the PCB power planes is reduced. One or more embodiments provide dedicated off-board space for decoupling capacitors or other electrical components, thereby further reducing board usage. One or more embodiments provide a reduction in the current flow through the integrated circuit package core and micro-vias, thereby increasing lifespan of the ASIC and reducing design time previously needed for high power routing within the ASIC package and on the PCB. As described above, simplified rework options are also provided with the embodiments described herein. 
     Although the apparatus and method have been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations made to the embodiments without departing from the scope of the embodiments. Accordingly, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.