Patent Application
20230137684
Embodiments of the present description generally relate to the field of thermal management for integrated circuit devices, and, more specifically, to boiling enhancement for two-phase immersion cooling of integrated circuit devices.
The integrated circuit industry is continually striving to produce ever faster, smaller, and thinner integrated circuit devices and packages for use in various electronic products, including, but not limited to, computer servers and portable products, such as portable computers, electronic tablets, cellular phones, digital cameras, and the like.
As these goals are achieved, the integrated circuit devices become smaller. Accordingly, the density of power consumption of electronic components within the integrated circuit devices has increased, which, in turn, increases the average junction temperature of the integrated circuit device. If the temperature of the integrated circuit device becomes too high, the integrated circuits may be damaged or destroyed. Thus, heat dissipation devices are used to remove heat from the integrated circuit devices in an integrated circuit package. In one example, heat spreading and dissipation devices may be thermally attached to integrated circuit devices for heat removal. The heat spreading and dissipation devices, in turn, dissipate the heat into the surrounding atmosphere. In another example, a cooling device, such as a heat exchanger or a heat pipe, may be thermally attached to integrated circuit devices for heat removal. However, as power densities and power envelopes increase to reach peak performance, these methods are becoming ineffective in removing sufficient heat.
One emerging heat removal technique is two-phase immersion cooling. This technique essentially comprises immersing an integrated circuit assembly into a liquid cooling bath containing a low boiling point liquid which vaporizes and, thus, cooling the integrated circuit assembly through latent heat transfer, as it generates heat. Although it is a promising technology, two-phase immersion cooling has various challenges to effective operation, as will be understood to those skilled in the art.
For example, in one embodiment of a two-phase immersion cooling assembly, a support substrate, such as a copper block, having a first surface and an opposing second surface, may have a boiling enhancement coating on the first surface and may have the second surface in thermal contact with the heat dissipation device by a thermal interface material layer, such as an indium/aluminum foil. However, the thermal interface material layer may contribute to the thermal resistance of the assembly, which may result in the assembly being incapable of removing a sufficient amount of heat.
In another example of an embodiment of a two-phase immersion cooling assembly, a boiling enhancement structure, such as a multi-layer copper meshing, may be attached to the heat dissipation device or to the integrated circuit devices directly with a low melting temperature solder, such as a 52% bismuth/48% tin solder. Although this configuration eliminates the thermal resistance of the thermal interface material layer of the previous example, the boiling enhancement structure is substantially permanently bonded to the heat dissipation device, and, thus, not effectively removable or replaceable at the end user, nor is it capable of being re-tested by the manufacturer. Therefore, a failing assembly would have to be scrapped.
Thus, there is an on-going effort to improve the operation and efficiency of two-phase immersion cooling assemblies.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It is understood that the accompanying drawings depict only several embodiments in accordance with the present disclosure and are, therefore, not to be considered limiting of its scope. The disclosure will be described with additional specificity and detail through use of the accompanying drawings, such that the advantages of the present disclosure can be more readily ascertained, in which:
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the claimed subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the subject matter. It is to be understood that the various embodiments, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the claimed subject matter. References within this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present description. Therefore, the use of the phrase “one embodiment” or “in an embodiment” does not necessarily refer to the same embodiment. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the claimed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the subject matter is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the appended claims are entitled. In the drawings, like numerals refer to the same or similar elements or functionality throughout the several views, and that elements depicted therein are not necessarily to scale with one another, rather individual elements may be enlarged or reduced in order to more easily comprehend the elements in the context of the present description.
The terms “over”, “to”, “between” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over” or “on” another layer or bonded “to” another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers.
The term “package” generally refers to a self-contained carrier of one or more dice, where the dice are attached to the package substrate, and may be encapsulated for protection, with integrated or wire-bonded interconnects between the dice and leads, pins or bumps located on the external portions of the package substrate. The package may contain a single die, or multiple dice, providing a specific function. The package is usually mounted on a printed circuit board for interconnection with other packaged integrated circuits and discrete components, forming a larger circuit.
Here, the term “cored” generally refers to a substrate of an integrated circuit package built upon a board, card or wafer comprising a non-flexible stiff material. Typically, a small printed circuit board is used as a core, upon which integrated circuit device and discrete passive components may be soldered. Typically, the core has vias extending from one side to the other, allowing circuitry on one side of the core to be coupled directly to circuitry on the opposite side of the core. The core may also serve as a platform for building up layers of conductors and dielectric materials.
Here, the term “coreless” generally refers to a substrate of an integrated circuit package having no core. The lack of a core allows for higher-density package architectures, as the through-vias have relatively large dimensions and pitch compared to high-density interconnects.
Here, the term “land side”, if used herein, generally refers to the side of the substrate of the integrated circuit package closest to the plane of attachment to a printed circuit board, motherboard, or other package. This is in contrast to the term “die side”, which is the side of the substrate of the integrated circuit package to which the die or dice are attached.
Here, the term “dielectric” generally refers to any number of non-electrically conductive materials that make up the structure of a package substrate. For purposes of this disclosure, dielectric material may be incorporated into an integrated circuit package as layers of laminate film or as a resin molded over integrated circuit dice mounted on the substrate.
Here, the term “metallization” generally refers to metal layers formed over and through the dielectric material of the package substrate. The metal layers are generally patterned to form metal structures such as traces and bond pads. The metallization of a package substrate may be confined to a single layer or in multiple layers separated by layers of dielectric.
Here, the term “bond pad” generally refers to metallization structures that terminate integrated traces and vias in integrated circuit packages and dies. The term “solder pad” may be occasionally substituted for “bond pad” and carries the same meaning.
Here, the term “solder bump” generally refers to a solder layer formed on a bond pad. The solder layer typically has a round shape, hence the term “solder bump”.
Here, the term “substrate” generally refers to a planar platform comprising dielectric and metallization structures. The substrate mechanically supports and electrically couples one or more IC dies on a single platform, with encapsulation of the one or more IC dies by a moldable dielectric material. The substrate generally comprises solder bumps as bonding interconnects on both sides. One side of the substrate, generally referred to as the “die side”, comprises solder bumps for chip or die bonding. The opposite side of the substrate, generally referred to as the “land side”, comprises solder bumps for bonding the package to a printed circuit board.
Here, the term “assembly” generally refers to a grouping of parts into a single functional unit. The parts may be separate and are mechanically assembled into a functional unit, where the parts may be removable. In another instance, the parts may be permanently bonded together. In some instances, the parts are integrated together.
Throughout the specification, and in the claims, the term “connected” means a direct connection, such as electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices.
The term “coupled” means a direct or indirect connection, such as a direct electrical, mechanical, magnetic or fluidic connection between the things that are connected or an indirect connection, through one or more passive or active intermediary devices.
The term “circuit” or “module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function. The term “signal” may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal. The meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.”
The vertical orientation is in the z-direction and it is understood that recitations of “top”, “bottom”, “above” and “below” refer to relative positions in the z-dimension with the usual meaning. However, it is understood that embodiments are not necessarily limited to the orientations or configurations illustrated in the figure.
The terms “substantially,” “close,” “approximately,” “near,” and “about,” generally refer to being within +/−10% of a target value (unless specifically specified). Unless otherwise specified the use of the ordinal adjectives “first,” “second,” and “third,” etc., to describe a common object, merely indicate that different instances of like objects to which are being referred and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.
For the purposes of the present disclosure, phrases “A and/or B” and “A or B” mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
Views labeled “cross-sectional”, “profile” and “plan” correspond to orthogonal planes within a cartesian coordinate system. Thus, cross-sectional and profile views are taken in the x-z plane, and plan views are taken in the x-y plane. Typically, profile views in the x-z plane are cross-sectional views. Where appropriate, drawings are labeled with axes to indicate the orientation of the figure.
Embodiments of the present description relate to the use of two-phase immersion cooling for integrated circuit assemblies. In one embodiment of the present description, the integrated circuit assembly may comprise an integrated circuit package having a heat dissipation assembly thermally coupled to at least one integrated circuit device, wherein the heat dissipation assembly includes a heat dissipation device having a boiling enhancement structure attached thereto with a chemically soluble adhesive material; and a thermal interface material between the boiling enhancement structure and the heat dissipation device. Utilizing a chemically soluble adhesive material allows for the boiling enhancement structure to be removed by dissolving the adhesive material, thus allowing for testing, rework, and/or replacement.
The electronic substrate 110 may further include conductive routes 118 or “metallization” (shown in dashed lines) extending through the electronic substrate 110. As will be understood to those skilled in the art, the conductive routes 118 may be a combination of conductive traces (not shown) and conductive vias (not shown) extending through the plurality of dielectric material layers (not shown). These conductive traces and conductive vias are well known in the art and are not shown in
The at least one integrated circuit package 200 may be electrically attached to the electronic substrate 110 in a configuration generally known as a flip-chip or controlled collapse chip connection (“C4”) configuration, according to an embodiment of the present description. The integrated circuit package 200 may comprise a package substrate or interposer 210 with a first surface 212 and an opposing second surface 214, and an integrated circuit device 220 electrically attached proximate the second surface 214 of the package interposer 210. In an embodiment of the present description, the package interposer 210 may be attached to the electronic substrate or board 110 with a plurality of package-to-substrate interconnects 116. In one embodiment of the present description, the package-to-substrate interconnects 116 may extend between bond pads (not shown) proximate a first surface 112 of the electronic substrate 110 and bond pads (not shown) proximate the first surface 212 of the package interposer 210.
The package interposer 210 may comprise any of the materials and/or structures as discussed previously with regard to the electronic substrate 110. The package interposer 210 may further include conductive routes 218 or “metallization” (shown in dashed lines) extending through the package interposer 210, which may comprise any of the materials and/or structures as discussed previously with regard to the conductive routes 118 of the electronic substrate 110. Bond pads (not shown) proximate the first surface 212 of the package interposer 210 may be in electrical contact with the conductive routes 218, and the conductive routes 218 may extend through the package interposer 210 and be electrically connected to bond pads (not shown) proximate the second surface 214 of the package substrate 210. As will be understood to those skilled in the art, the package interposer 210 may be a cored substrate or a coreless substrate.
The integrated circuit device 220 may be any appropriate device, including, but not limited to, a microprocessor, a chipset, a graphics device, a wireless device, a memory device, an application specific integrated circuit, a transceiver device, an input/output device, combinations thereof, stacks thereof, and the like. As shown in
In an embodiment of the present description, the integrated circuit device 220 may be electrically attached to the package interposer 210 with a plurality of device-to-substrate interconnects 232. In one embodiment of the present description, the device-to-substrate interconnects 232 may extend between bond pads (not shown) on the second surface 214 of the package interposer 210 and bond pads (not shown) on the first surface 222 of the integrated circuit device 220. The device-to-substrate interconnects 232 may be any appropriate electrically conductive material or structure, including, but not limited to, solder balls, metal bumps or pillars, metal filled epoxies, or a combination thereof. In one embodiment of the present description, the device-to-substrate interconnects 232 may be solder balls formed from tin, lead/tin alloys (for example, 63% tin/37% lead solder), and high tin content alloys (e.g. 90% or more tin—such as tin/bismuth, eutectic tin/silver, ternary tin/silver/copper, eutectic tin/copper, and similar alloys). In another embodiment of the present description, the device-to-substrate interconnects 232 may be copper bumps or pillars. In a further embodiment of the present description, the device-to-substrate interconnects 232 may be metal bumps or pillars coated with a solder material.
The device-to-substrate interconnects 232 may be in electrical communication with integrated circuitry (not shown) within the integrated circuit device 220 and may be in electrical contact with the conductive routes 218. The conductive routes 218 may extend through the package interposer 210 and be electrically connected to package-to-board interconnects 116. As will be understood to those skilled in the art, the package interposer 210 may reroute a fine pitch (center-to-center distance) of the device-to-interposer interconnects 232 to a relatively wider pitch of the package-to-substrate interconnects 116. The package-to-substrate interconnects 116 may be any appropriate electrically conductive material, including, but not limited to, metal filled epoxies and solders, such as tin, lead/tin alloys (for example, 63% tin/37% lead solder), and high tin content alloys (e.g. 90% or more tin—such as tin/bismuth, eutectic tin/silver, ternary tin/silver/copper, eutectic tin/copper, and similar alloys). Although
As further shown in
The heat dissipation device 260 may be made of any appropriate thermally conductive material, including, but not limited to, at least one metal material and alloys of more than one metal, or highly doped glass or highly conductive ceramic material, such as aluminum nitride. In an embodiment of the present description, the heat dissipation device 260 may comprise copper, nickel, aluminum, alloys thereof, laminated metals including coated materials (such as nickel coated copper), and the like. The internal thermal interface material 254 may be any appropriate, thermally conductive material, including, but not limited to, a thermal grease, a thermal gap pad, a polymer, an epoxy filled with high thermal conductivity fillers (such as metal particles or silicon particles), a metal alloy (such as solder or liquid metal), and the like.
As illustrated in
The attachment adhesive 252 may be any appropriate material, including, but not limited to, silicones (such as polydimethylsiloxane), epoxies, and the like. It is understood that the boundary wall 272 not only secures the heat dissipation device 260 to the package interposer 210, but also helps to maintain a desired distance (e.g., bond line thickness) between the first surface 264 of the heat dissipation device 260 and the second surface 224 of the integrated circuit device 220.
Prior to the attachment of the heat dissipation device 260, an electrically-insulating underfill material 242 may be disposed between the integrated circuit device 220 and the package interposer 210, which substantially encapsulates the device-to-interposer interconnects 232. The underfill material 242 may be used to reduce mechanical stress issues that can arise from thermal expansion mismatch between the package interposer 210 and the integrated circuit device 220. The underfill material 242 may be an appropriate material, including, but not limited to epoxy, cyanoester, silicone, siloxane and phenolic based resins, that has sufficiently low viscosity to be wicked between the integrated circuit device 220 and the package interposer 210 by capillary action when introduced by an underfill material dispenser (not shown), which will be understood to those skilled in the art. The underfill material 242 may be subsequently cured (hardened), such as by heat or radiation.
As shown in
In the embodiments of the present description, a boiling enhancement structure 330 may be attached to the second surface 266 of the main body 262 of the heat dissipation device 260 with a chemically soluble adhesive material 310. In one embodiment, the chemically soluble adhesive material 310 contacts the heat dissipation device 260 and the boiling enhancement structure 330. In an embodiment of the present description, a thermal interface material 320 may be between the boiling enhancement structure 330 and the heat dissipation device 260. In a specific embodiment of the present description, the thermal interface material 320 may contact the boiling enhancement structure 330, the heat dissipation device 260, and the chemically soluble adhesive material 310. It will be understood that the boiling enhancement structure 330 may provide high surface area for the dielectric low-boiling point liquid 120 in a liquid state to nucleate and form the vapor or gas state 122. It will be further understood that having the dielectric low-boiling point liquid 120 close to the heat source (e.g., the integrated circuit device 220) and maximizing the contact area between the dielectric low-boiling point liquid 120 and heat dissipation device 260 may increase heat dissipation efficiency.
In one embodiment of the present description, the chemically soluble adhesive material 310 may, optionally, be partially cured with heat and/or light to form a dam to contain the thermal interface material 320 to be deposited. As shown in
As shown in
As shown in
The boiling enhancement structure 330 may be any appropriate structure that has a high surface area to provides nucleation sites for the dielectric low-boiling point liquid 120. In an embodiment of the present description, the boiling enhancement structure 330 may comprise a carbon foam or metal foam (such as copper foam, nickel foam, and the like), which is generically represented as element 330 in
In another embodiment of the present description, the boiling enhancement structure 330 may comprise a support substrate 340 having a boiling enhancement layer 350 thereon, as shown in
In one embodiment of the present description, the boiling enhancement material layer 350 may be a micro-porous coating. As will be understood to those skilled in the art, a micro-porous coating may provide capillarity for fluid travel of the dielectric low-boiling point liquid 120 (see
Although not specifically illustrated, it is understood that the support substrate 340 may be modified to enhance the surface area of the boiling enhancement layer 350, such as by roughening, forming projections (such as fins or pillars), forming trenches (such as slots), and the like. Furthermore, although only one integrated circuit device 220 is illustrated in
As previously discussed, the chemically soluble adhesive 310 is dissolvable in an appropriate solvent. Thus, the boiling enhancement structure 330 may be removed by exposing the chemically soluble adhesive 310 to the appropriate solvent. In a specific embodiment, the chemically soluble adhesive material 310 may comprise acrylic, such as a ultraviolet glue, and the solvent may be acetone, which is compatible with existing package assembly and test flow, and, thus, requires no additional steps or changes to existing assembly/test equipment.
Although the embodiments of the present description are primarily directed to immersive cooling, it is understood that the embodiments are not so limited. Where appropriate, the embodiments of the present description may be incorporated into various heat dissipation assemblies.
The communication chip enables wireless communications for the transfer of data to and from the computing device. The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device may include a plurality of communication chips. For instance, a first communication chip may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.
The entire computing device 500 or at least one of the integrated circuit components within the computing device 500 may be immersed in a two-phase immersion system. In one embodiment, the integrated circuit component may comprise an integrated circuit package having a heat dissipation assembly comprises a heat dissipation device; a boiling enhancement structure attached to the heat dissipation device with a chemically soluble adhesive material; and a thermal interface material between the boiling enhancement structure and the heat dissipation device.
In various implementations, the computing device may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a tablet, a personal digital assistant (PDA), an ultra-mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device may be any other electronic device that processes data.
It is understood that the subject matter of the present description is not necessarily limited to specific applications illustrated in
The following examples pertain to further embodiments and specifics in the examples may be used anywhere in one or more embodiments, wherein Example 1 is an apparatus, comprising a heat dissipation device, a boiling enhancement structure attached to the heat dissipation device with a chemically soluble adhesive material, and a thermal interface material between the boiling enhancement structure and the heat dissipation device.
In Example 2, the subject matter of Example 1 can optionally include the chemically soluble adhesive material contacting the heat dissipation device and the boiling enhancement structure.
In Example 3, the subject matter of any of Examples 1 to 2 can optionally include the thermal interface material contacting the boiling enhancement structure, the heat dissipation device, and the chemically soluble adhesive material.
In Example 4, the subject matter of any of Examples 1 to 3 can optionally include the boiling enhancement material structure comprising a metal mesh.
In Example 5, the subject matter of any of Examples 1 to 3 can optionally include the boiling enhancement material structure comprising a metal foam.
In Example 6, the subject matter of any of Examples 1 to 3 can optionally include the boiling enhancement material structure comprising a support substrate having a boiling enhancement layer.
In Example 7, the subject matter of any of Examples 1 to 6 can optionally include the thermal interface material comprising a liquid metal.
In Example 8, the subject matter of any of Examples 1 to 7 can optionally include the chemically soluble adhesive material comprising an ultraviolet glue.
Example 9 is an apparatus, comprising an integrated circuit device having a first surface and an opposing second surface, a heat dissipation device having a first surface and an opposing second surface, wherein the first surface of the first surface of the heat dissipation device is thermally attached to the second surface of the integrated circuit device; a boiling enhancement structure attached to the heat dissipation device with a chemically soluble adhesive material, and a thermal interface material between the boiling enhancement structure and the heat dissipation device.
In Example 10, the subject matter of Example 9 can optionally include the chemically soluble adhesive material contacting the heat dissipation device and the boiling enhancement structure.
In Example 11, the subject matter of any of Examples 9 to 10 can optionally include the thermal interface material contacting the boiling enhancement structure, the heat dissipation device, and the chemically soluble adhesive material.
In Example 12, the subject matter of any of Examples 9 to 11 can optionally include the boiling enhancement material structure comprising a metal mesh.
In Example 13, the subject matter of any of Examples 9 to 11 can optionally include the boiling enhancement material structure comprising a metal foam.
In Example 14, the subject matter of any of Examples 9 to 11 can optionally include the boiling enhancement material structure comprising a support substrate having a boiling enhancement layer.
In Example 15, the subject matter of any of Examples 9 to 14 can optionally include the thermal interface material comprising a liquid metal.
In Example 16, the subject matter of any of Examples 9 to 15 can optionally include the chemically soluble adhesive material comprising an ultraviolet glue.
Example 17 is a system, comprising an electronic board and an integrated circuit package electrically attached to the electronic board, wherein the integrated circuit package comprises an integrated circuit device having a first surface and an opposing second surface, a heat dissipation device having a first surface and an opposing second surface, wherein the first surface of the first surface of the heat dissipation device is thermally attached to the second surface of the integrated circuit device; a boiling enhancement structure attached to the heat dissipation device with a chemically soluble adhesive material, and a thermal interface material between the boiling enhancement structure and the heat dissipation device.
In Example 18, the subject matter of Example 17 can optionally include the chemically soluble adhesive material contacting the heat dissipation device and the boiling enhancement structure.
In Example 19, the subject matter of any of Examples 17 to 18 can optionally include the thermal interface material contacting the boiling enhancement structure, the heat dissipation device, and the chemically soluble adhesive material.
In Example 20, the subject matter of any of Examples 17 to 19 can optionally include the boiling enhancement material structure comprising a metal mesh.
In Example 21, the subject matter of any of Examples 17 to 19 can optionally include the boiling enhancement material structure comprising a metal foam.
In Example 22, the subject matter of any of Examples 17 to 19 can optionally include the boiling enhancement material structure comprising a support substrate having a boiling enhancement layer.
In Example 23, the subject matter of any of Examples 17 to 22 can optionally include the thermal interface material comprising a liquid metal.
In Example 24, the subject matter of any of Examples 17 to 23 can optionally include the chemically soluble adhesive material comprising an ultraviolet glue.
Having thus described in detail embodiments of the present invention, it is understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof.
