Patent Description:
Japanese patent application no. <CIT> and European patent application no. <CIT> are useful for understanding the present invention.

According to the present invention there is provided an integrated circuit (IC) package comprising: an IC die carrying electronic circuitry; an encapsulation material at least partially covering the IC die, wherein the encapsulation material defines a plurality of cavities in a top surface of the encapsulation material; a plurality of microfans located in the plurality of cavities; and a plurality of sensors, wherein each sensor of the plurality of sensors produces a signal indicating a temperature at a location of the sensor.

Optionally each of the plurality of cavities is configured to hold a corresponding one of the plurality of microfans.

Optionally the plurality of cavities are arranged in a two-dimensional array along the top surface of the encapsulation material.

Optionally, the plurality of sensors are arranged in a two-dimensional array parallel to the top surface of the encapsulation material.

Optionally each of the plurality of sensors is aligned vertically relative to each of the plurality of microfans.

Optionally, each of at least some of the plurality of sensors is aligned vertically relative to space between adjacent microfans of the plurality of microfans.

Optionally each of the plurality of microfans is configured to create airflow upward from the top surface of the encapsulation material.

Optionally, the encapsulation material further defines at least one air vent communicatively coupled to at least one of the plurality of cavities such that air is drawn through the air vent into the at least one of the plurality of cavities.

Optionally each of the plurality of microfans defines at least one air vent such that air is drawn through the air vent into the at least one of the plurality of cavities.

According to the present invention there is further provided a cooling system for an integrated circuit (IC) package, the cooling system comprising: a plurality of microfans located in a plurality of cavities in a top surface of an encapsulation material of the IC package, wherein the encapsulation material at least partially covers an IC die carrying electronic circuitry; a plurality of sensors located in the IC package, wherein each sensor of the plurality of sensors produces a signal indicating a temperature at a location of the sensor; and fan control logic that: receives, from each sensor of the plurality of sensors, the signal indicating the temperature at the location of the sensor; and sets, for each microfan of the plurality of microfans, in response to the signals indicating the temperature at the location of each of a subset of the plurality of sensors associated with the microfan, a speed of the microfan.

Optionally, the fan control logic sets the speed of each microfan of the plurality of microfans in response to the signal from one sensor of the plurality of sensors closest to the microfan.

Optionally the one sensor of the plurality of sensors closest to the microfan is located vertically relative to the microfan.

Optionally the fan control logic sets the speed of each microfan of the plurality of microfans in response to the signals from more than one sensor of the plurality of sensors closest to the microfan.

Optionally the more than one sensor of the plurality of sensors closest to the microfan are adjacent the microfan.

Optionally the fan control logic sets the speed of each microfan of the plurality of microfans in response to an average of the temperatures at the location of each of the more than one sensor of the plurality of sensors closest to the microfan.

Optionally the fan control logic sets the speed of each microfan of the plurality of microfans in response to a maximum of the temperatures at the location of each of the more than one sensor of the plurality of sensors closest to the microfan.

According to the present invention, there is yet further provided a method of cooling an integrated circuit (IC) package, the method comprising: receiving, from each sensor of a plurality of sensors included in the IC package that includes an IC die carrying electronic circuitry, a signal indicating a temperature at a location of the sensor; and setting, for each microfan of a plurality of microfans located in a plurality of cavities in a top surface of an encapsulation material at least partially covering the IC die, in response to the signals indicating the temperature at the location of each of a subset of the plurality of sensors associated with the microfan, a speed of the microfan.

Optionally the speed of each microfan of the plurality of microfans is set in response to the signal from one sensor of the plurality of sensors closest to the microfan.

Optionally the speed of each microfan of the plurality of microfans is set in response to the signals from more than one sensor of the plurality of sensors closest to the microfan.

Optionally the speed of each microfan of the plurality of microfans is based on a maximum value of the temperatures at the location of each of the more than one sensor.

The accompanying drawings illustrate a number of exemplary embodiments and are a part of the specification. Together with the following description, these drawings demonstrate and explain various principles of the present disclosure.

Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. While the exemplary embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the present disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

As integrated circuit (ICs) designers and fabricators continue to increase the functionality and speed available within a single IC package, the amount of power consumed, and thus the amount of heat dissipated, by the IC continues to increase similarly. Consequently, those ICs that tend to consume the most power, including, but not limited to, central processing units (CPUs), graphics processing units (GPUs), and the like, are traditionally the focus of most IC-specific passive heat mitigation efforts.

Depending on the size of the IC package, the circuit design of the IC, the speed at which the IC is to be operated, and other factors, the maximum amount of heat to be dissipated under a maximum expected workload (often referred to as the "thermal design power" (TDP) of the IC) may indicate whether an IC-specific heat mitigation strategy is required. In some examples, a TDP of at least <NUM> watts (W) may indicate the need for a passive heat sink. Typically, a heat sink (e.g., fashioned from an aluminum alloy, copper, or other metal) is coupled to a top flat surface of the IC package using a thermal adhesive to maximize heat transfer from the top of the IC package to the heat sink. Further, the heat sink may incorporate a number of fins or similar physical features to increase an amount of surface area of the heat sink. Air flow across the fins of the heat sink may then serve to remove thermal energy from the heat sink to increase the cooling effect of the heat sink on the corresponding IC package. In some examples, this air flow may be provided by way of a separate fan installed in an enclosure that surrounds the IC package and other circuitry, or via an IC-specific fan coupled more directly to the heat sink.

IC packages with higher TDPs, such as those exceeding <NUM> W, may benefit from the use of a liquid cooling system coupled to a top of the IC package. Such a system may include tubing that carries a liquid (e.g., distilled water) by way of a pump to a metallic device (e.g., a water block) that is coupled to the top of the IC package, as well as a radiator. In operation, the liquid is pumped through the water block (e.g., to extract heat from the IC package) and through the radiator (e.g., to extract the heat from the liquid, possibly assisted by an external fan).

The ability of heat sinks, water blocks, and other devices that may be attached to a top external surface of an IC package to extract a sufficient amount of heat therefrom continues to be challenged, as ICs with increasing TDPs (e.g., <NUM> kW or more) continue to be proposed and designed.

The present disclosure is generally directed to an IC package with a plurality of microfans (e.g., fans of several millimeters in diameter) embedded therewithin. Also included within the IC package may be a plurality of sensors (e.g., heat sensors) distributed therein. Control logic, which may be incorporated within the IC package or located external thereto, may individually control the operation of each of the plurality of fans based on the signals received from the plurality of sensors to maintain a desired temperature level for the IC. As will be explained in greater detail below, embodiments of the present disclosure may facilitate greater heat extraction than more conventional technologies, thus supporting the use of high-TDP ICs.

Features from any of the embodiments described herein may be used in combination with one another in accordance with the general principles described herein. These and other embodiments, features, and advantages will be more fully understood upon reading the following detailed description in conjunction with the accompanying drawings and claims.

The following will provide, with reference to <FIG>, detailed descriptions of IC packages with a plurality of embedded microfans, as well as associated cooling systems and methods employing such packages. An exemplary IC package configured to implement an embedded fan-based cooling system for the package is described in conjunction with <FIG> and <FIG>. In association with <FIG>, the exemplary IC package, including an installed plurality of microfans and associated sensors, is discussed. An exemplary cooling system including the exemplary IC package, as well as an exemplary method of operating such a cooling system, are explained in connection with <FIG> and <FIG>, respectively.

<FIG> is a side cross-section of an exemplary IC package <NUM> that is configured to implement an embedded fan-based cooling system. In the description of IC package <NUM>, various directional references (e.g., top, bottom, up, down, and so on) are provided relative to the horizontal orientation of IC package <NUM>, as illustrated in <FIG>. However, such directional references are provided only for explanatory purposes, and other orientations of IC package <NUM>, when deployed in an electronic system, are also possible.

As depicted in <FIG>, IC package <NUM> may include an IC die <NUM> that carries electronic circuitry, the operation of which may generate heat. To enable electrical connection to various portions of the circuitry carried by IC die <NUM>, a plurality of conductive pads <NUM> coupled to various points of the circuitry may be distributed (e.g., in a two-dimensional grid) along one or more surfaces (e.g., along the bottom) of IC die <NUM>. Further, in some embodiments, corresponding conductive pads <NUM> may be provided along a surface (e.g., along the top) of a substrate <NUM> to be positioned under ID die <NUM>. Substrate <NUM> may be a multilayer organic substrate, although substrate <NUM> may include other types of materials and/or structures in other examples. Substrate <NUM> may include a plurality of traces <NUM> that conductively couple conductive pads <NUM> along the top of substrate <NUM> to a plurality of solder bumps <NUM> along an opposing surface (e.g., along the bottom) of substrate <NUM>. In some examples, solder bumps <NUM> may be spaced to facilitate electrical connection with corresponding pads of a printed circuit board (PCB) (not shown in <FIG>), such by heat or another soldering process. Also, in some embodiments, conductive pads <NUM> of IC die <NUM> may be electrically connected to corresponding conductive pads <NUM> of substrate <NUM> by way of conductive bumps <NUM> (e.g., solder bumps). In addition, in some embodiments, after coupling IC die <NUM> to substrate <NUM>, as described above, an underfiller <NUM> made of a nonconductive substance may be applied (e.g., heated and flowed) between IC die <NUM> and substrate <NUM> such that, when underfiller <NUM> cools, the combination of IC die <NUM>, substrate <NUM>, and underfiller <NUM> forms a mechanically stable structure in the presence of physical shock, extreme heat, and/or other challenging physical events.

While <FIG> depicts a particular structure that includes IC die <NUM> and an interconnection structure for facilitating electrical connection between IC die <NUM> and a PCB or other electronic structure, other structures involving IC die <NUM> may be employed in IC package <NUM> in other embodiments.

To facilitate protection of IC die <NUM> from a variety of environmental conditions, an encapsulation material <NUM> (e.g., an epoxy that is molded over IC die <NUM>) may be applied over IC die <NUM>, as well as possibly substrate <NUM> and underfiller <NUM>. Conventionally, passive cooling systems, such as heat sinks, are applied to an external surface of such an encapsulation material to facilitate the cooling of the associated IC package. Instead, as illustrated in <FIG> and described more fully below, encapsulation material <NUM> may define a plurality of cavities <NUM> in a top surface of encapsulation material <NUM> that are configured to include a plurality of microfans (not depicted in <FIG>) such that operation of one or more of the microfans may facilitate extraction of heat that is generated from the operation the electronic circuitry carried in IC die <NUM>.

<FIG> is a top cross-section view of IC package <NUM> in which encapsulation material <NUM> defines cavities <NUM> for microfans in the top surface of encapsulation material <NUM>. As depicted in <FIG>, each microfan cavity <NUM> is sized and configured to retain a single microfan (not shown in <FIG> and <FIG>). However, each microfan cavity <NUM> may be configured to retain two or more microfans in other embodiments. Further, as indicated in <FIG>, microfan cavities <NUM> may be aligned in a two-dimensional array or grid. In other examples, microfan cavities <NUM> may be aligned such that every other row or column of microfan cavities <NUM> is offset relative to the adjacent rows or columns of microfan cavities <NUM>. In yet other embodiments, microfan cavities <NUM> may form a checkerboard pattern in encapsulation material <NUM>. Other patterns for microfan cavities <NUM> are also possible.

Also, as illustrated in <FIG>, encapsulation material <NUM> may define a plurality of sensor cavities <NUM> that are configured to retain sensors (not illustrated in <FIG>), each of which may generate a signal indicating (in other words, indicative of) a temperature at the location of the sensor. These sensors may include heat sensors, heat flux sensors, temperature sensors, and/or other sensors that provide some indication of temperature at the location of the sensor.

In the particular example of <FIG>, sensor cavities <NUM> are aligned in a two-dimensional array or grid such that sensor cavities <NUM> reside at a center of each two-by-two grouping of microfan cavities <NUM>. Other locations for sensor cavities <NUM> are also possible, such as, for example, between pairs of microfan cavities <NUM>, underneath microfan cavities <NUM> (e.g., between each microfan cavity <NUM> and IC die <NUM>), and the like. In yet other embodiments, the sensors may be located in IC die <NUM> (e.g., incorporated with other electronic circuitry therein) or atop IC die <NUM>.

Encapsulation material <NUM>, in some examples, may also include space (e.g., pathways) for electrical traces or wires (not shown in <FIG>) to couple a power supply and/or fan control logic with the microfans and/or sensors.

In some embodiments, encapsulation material <NUM> may be molded, machined, or otherwise processed to form microfan cavities <NUM>, sensor cavities <NUM>, and/or other cavities therein. In some examples, a layering process (e.g., three-dimensional printing) in which multiple layers of encapsulation material <NUM> are deposited upon IC die <NUM> to facilitate generation of the cavities. As shown in <FIG>, encapsulation material <NUM> remaining between microfan cavities <NUM> may facilitate retention of the mechanical strength of encapsulation material <NUM> that may be desired to protect IC die <NUM> and other portions of IC package <NUM>. However, a lesser or greater amount of encapsulation material <NUM> remaining between microfan cavities <NUM> and/or sensor cavities <NUM> may be employed in other examples.

<FIG> is a top cross-section of IC package <NUM> after installation of a plurality of microfans <NUM> in corresponding microfan cavities <NUM> and installation of sensors <NUM> in sensor cavities <NUM> in encapsulation material <NUM>. In some examples, a microfan <NUM> may be a small electrically-driven fan of several millmeters (e.g., <NUM>-<NUM>) in width. In some embodiments, microfans <NUM> are configured to create airflow upward (e.g., upward from IC die <NUM>) to extract heat from IC package <NUM>. In some embodiments, each microfan <NUM> may be include one or more air vents <NUM> through which cooler air may be drawn into the corresponding microfan cavity <NUM> for subsequent extraction via microfan <NUM>. In other embodiments, an air vent for a microfan <NUM> may be incorporated as a cavity or channel in encapsulation material <NUM> that couples an exterior of encapsulation material <NUM> (e.g., at a location adjacent microfan <NUM>) with the corresponding microfan cavity <NUM>. In yet other examples, neither encapsulation material <NUM> nor microfans <NUM> may define a separately identifiable air vent.

<FIG> is a block diagram of an exemplary cooling system <NUM> including microfans <NUM> and sensors <NUM>, as incorporated in IC package <NUM>. As shown in <FIG>, cooling system <NUM> may also include a power supply <NUM> and fan control logic <NUM>. Also, as depicted in <FIG>, power supply <NUM> and fan control logic <NUM> may reside externally to IC package <NUM>. For example, power supply <NUM> and fan control logic <NUM> may reside on a PCB upon which IC package <NUM> is installed, or in another portion of an electronic system incorporating IC package <NUM>. However, in other examples, power supply <NUM> and/or fan control logic <NUM> may be incorporated within IC package <NUM> (e.g., within or on IC die <NUM>, embedded within encapsulation material <NUM>, or elsewhere). In some embodiments, power supply <NUM> may supply electrical power to operate microfans <NUM>, sensors <NUM>, and/or fan control logic <NUM>.

Fan control logic <NUM>, in some examples, may be hardware control logic or a small algorithmic controller executing instructions stored in a memory device. Generally, fan control logic <NUM> may receive signals from one or more sensors <NUM> that each indicate a temperature at a location of the corresponding sensor <NUM> and, based on those signals, operate microfans <NUM> associated with that location.

<FIG> is a flow diagram of an exemplary method <NUM> of operating cooling system <NUM> of <FIG>. While various embodiments of method <NUM> are described below in view of IC package <NUM> as illustrated in <FIG>, other embodiments of IC package <NUM>, as discussed more generally above, may also benefit from application of method <NUM>.

In method <NUM>, at step <NUM>, a signal may be received (e.g., at fan control logic <NUM>) from each sensor of a plurality of sensors (e.g., sensors <NUM>) embedded in an IC package (e.g., IC package <NUM>) indicating a temperature at a location of the sensor. At step <NUM>, a speed may be set for each microfan of a plurality of microfans (e.g., microfans <NUM>) embedded in the IC package in response to the signal indicating the temperature at the location of each of a subset of the plurality of sensors associated with the microfan. Further, in some examples, the receiving of the signals and the setting of fan speed may be performed continuously, periodically, or repeatedly over at least some length of time.

More specifically, in some embodiments, in response to one or more sensor <NUM> signals that indicate an elevated temperature at a particular location or area of IC package <NUM>, fan control logic <NUM> may increase a rotational rate of one or more microfans <NUM> located at or near the corresponding sensors <NUM>. Oppositely, a decrease in temperature at a particular location of IC package <NUM>, as indicated by one or more sensor <NUM> signals associated with that location, may result in fan control logic <NUM> reducing a rotational rate of one or more microfans <NUM> located at or near the one or more sensors <NUM> providing those signals. In the environment of <FIG>, in which sensors <NUM> are located at corner locations of each microfan <NUM>, each individual microfan <NUM> may be operated in view of the signals from the four sensors <NUM> located adjacent to (e.g., at the four corners of) that microfan <NUM>. In some embodiments, the speed of a particular microfan <NUM> may be based on an average temperature indicated by the signals received from the four sensors <NUM> at the corners of the particular microfan <NUM>. In other examples, the speed of a specific microfan <NUM> may be based on a maximum temperature indicated among the signals received from the four corresponding sensors <NUM>. In yet other examples, signals generated by additional sensors <NUM> near a particular microfan <NUM>, such as those surrounding one or more microfans <NUM> adjacent the particular microfan <NUM>, also may be considered when setting the speed of the particular microfan <NUM>. In that case, the temperatures indicated by the signals from sensors <NUM> located more remotely from microfan <NUM> may be weighted less than the temperatures indicated by the signal from sensors <NUM> positioned adjacent to microfan <NUM>.

In yet other arrangements of sensors <NUM>, such as a single sensor <NUM> located near each microfan <NUM> (e.g., positioned under microfan <NUM>, such as on IC die <NUM>, or between microfan <NUM> and IC die <NUM>), the rotational speed of a specific microfan <NUM> may depend solely upon the temperature indicated by the signal generated by the single sensor <NUM> corresponding to that specific microfan <NUM>. In other embodiments, temperatures indicated by signals associated with other nearby sensors <NUM>, such as each sensor <NUM> adjacent the single sensor <NUM>, may also be considered when setting the rotational speed of the specific microfan <NUM>. Other relationships between sensors <NUM> and microfans <NUM> other than those discussed above are also possible.

As explained above in conjunction with <FIG>, the IC packages described herein, as well as the associated cooling systems and methods discussed above, may facilitate more effective and efficient cooling of an IC package, especially one that exhibits a high TDP that demands an extraordinary level of cooling. More specifically, in some embodiments, heat extraction may be targeted at those portions of the IC package that are currently generating the most heat, and the extraction may be increased or decreased at those specific locations according to the level of heat being detected at the time. Additionally, compared to a heat sink or other passive technology, the cooling system embodiments discussed herein may consume much less volume above the IC package being cooled, possibly resulting in a lower-profile electronic device that employs the IC package.

Claim 1:
An integrated circuit (IC) package (<NUM>) comprising:
an IC die (<NUM>) carrying electronic circuitry;
an encapsulation material (<NUM>) at least partially covering the IC die (<NUM>), wherein the encapsulation material (<NUM>) defines a plurality of cavities (<NUM>) in a top surface of the encapsulation material (<NUM>);
characterized by a plurality of microfans (<NUM>) located in the plurality of cavities (<NUM>); and
a plurality of sensors (<NUM>), wherein each sensor (<NUM>) of the plurality of sensors (<NUM>) produces a signal indicating a temperature at a location of the sensor (<NUM>).