具体实施方式：
[0022]Configurations of the present disclosure are directed to, among other things, a display module for an electronic device having a thermal management structure integrated on a backside of the display module. When the thermal management structure described herein is integrated in a display module of an electronic device, the electronic device can conserve resources with respect to power resources (e.g., battery), and/or other resources while better managing the thermal load created by heat generating components within the electronic device. The thermal management structure described herein can also improve the mechanical strength (i.e., stiffness) of the electronic device while maintaining a thin profile. Technical effects other than those mentioned herein can also be realized from an implementation of the technologies disclosed herein.
[0023]FIG. 1 illustrates an exploded perspective view of example components of an example electronic device 100 including a display module 102 having a thermal management structure 104 (abbreviated to “TMS 104” in FIG. 1) integrated on a backside of the display module 102. A front view 106 and a side view 108 of the electronic device 100 are also shown at the top of FIG. 1 for illustrating various planes of reference. For example, the front view 106 of the electronic device 100 shows an imaginary midsagittal plane that runs through the middle of the electronic device 100 and splits the electronic device 100 into right and left sides (in the context of a landscape orientation of the display). The front view 106 also shows an imaginary transverse plane that runs through the middle of the electronic device 100 and splits the electronic device 100 into superior (top/upper) and inferior (bottom/lower) parts. Finally, the side view 108 shows an imaginary frontal plane that runs through the middle of the electronic device 100 and splits the electronic device 100 into front and back parts. The front view 106 also shows a two-dimensional (2D) coordinate reference plane (e.g., an X-Y plane) that is parallel to the frontal plane, while the side view 108 shows a 2D coordinate reference plane (e.g., a Y-Z plane) that is parallel to the midsagittal plane.
[0024]The electronic device 100 can be implemented as any type of display device, including, without limitation, a personal computer, a laptop computer, a desktop computer, a portable digital assistant (PDA), a mobile phone, tablet computer, an electronic book (eBook) reader device, a television, a wall mounted display, a panel display, an automobile display, a navigation device display (e.g., global positioning system (GPS) device display), a point of sale terminal display, an automated teller machine (ATM) display, a wearable computing device having a display (e.g., a smart watch, electronic “smart” glasses, a fitness tracker, etc.), or any other electronic device that is configured to display digital images to a user on the display of the electronic device 100. FIG. 1 shows the electronic device 100 in the form of a tablet computer for illustrative purposes.
[0025]The components of the electronic device 100 shown in the exploded perspective view of FIG. 1 can include, without limitation, the display module 102 and a logic board 110 that is disposed behind the display module 102. The logic board can comprise any suitable substrate, such as a printed circuit board (PCB), configured to support electrical components including, without limitation, one or more central processing units (CPUs), one or more field programmable gate arrays (FPGAs), one or more graphics processing units (CPUs), one or more complex programmable logic devices (CPLDs), one or more application specific integrated circuits (ASICs), one or more system-on-chip (SoCs), and so on. Often these electrical components generate heat during operation of the electronic device 100 when power is supplied to the components mounted on the logic board 110. Hence, at least some of the components on the logic board 110 are referred to herein as “heat generating components 112.”FIG. 1 depicts a few example heat generating components 112 that can be disposed on a front surface of the logic board 110.
[0026]The display module 102 of the electronic device 100 can include, (from top to bottom in FIG. 1), without limitation, a cover lens 114, a display layer 116, and a backlight unit 118. Although the display module 102 of FIG. 1 can be based on any suitable display technology, the display module 102 is shown to include the backlight unit 118, which is not found in some display technologies, such as OLED displays, and oftentimes, electrophoretic displays. Thus, the display module 102 of FIG. 1 can represent any suitable display technology known to a person having ordinary skill in the art that includes a backlight unit 118, such as an LCD display, which includes the backlight unit 118. In general, the display module 102 is configured to generate an image that is viewable to a user via the display screen of the electronic device 100.
[0027]The cover lens 114 can be configured to protect the internal components of the electronic device 100. The cover lens 114 is transparent to enable a viewing user of the electronic device 100 to view displayed images generated by the other components of the display module 102. The cover lens 114 can be made of a rigid, or semi-rigid, material that provides sufficient protection to the internal components from objects and environmental elements (e.g., water or moisture, dirt/dust, etc.). For example, the cover lens 114 can be made of glass, plastic, or some composite or combination thereof. In some cases, the cover lens 114 can be made of polycarbonate (PC), poly(methyl methacrylate (PMMA), or the like.
[0028]The cover lens 114 can be disposed in front of the display layer 116, and the cover lens 114 has a front surface 120 that, in general, faces the viewing user when the electronic device 100 is used as a viewing device (e.g., when the electronic device 100 is used to view images, documents, videos, etc.). Accordingly, the front surface 120 is oriented in the positive z-direction and is parallel to the frontal plane of the electronic device 100. It is to be appreciated that each of the components of the electronic device 100 shown in FIG. 1 can include surfaces that can be referenced in a similar manner. That is, each of the components shown in the exploded perspective view of the electronic device 100 can have a front surface oriented in the positive z-direction of FIG. 1 and a rear (or back) surface oriented in the negative z-direction of FIG. 1, where both front and rear surfaces are parallel to the frontal plane shown in FIG. 1.
[0029]The display layer 116 can be disposed behind the cover lens 114. In some configurations, the display layer 116 can comprise an LCD panel that is configured to turn pixels on/off and to change the pixel color of the image that is displayed by the display module 102. Depending on the type of display technology implemented in the display module 102, the display layer 116 can generally be configured to activate individual pixels in terms of either emitting light or allowing light to pass through the pixel area, and to generate a pixel color (e.g., red, green, or blue). Accordingly, the display layer 116 can comprise an array of liquid crystals that respond (e.g., twist or untwist) to supplied electric current, which, in turn, controls the amount of light that passes through the display layer 116. It is to be appreciated that, for touch display modules, one or more touch layers can be disposed in the display stack, such as between the cover lens 114 and the display layer 116. For example, a capacitive touch sensor, a resistive touch sensor, or the like, can be disposed between the cover lens 114 and the display layer 116 to enable touch sensing functionality for a touch screen display of the electronic device 100. It is also to be appreciated that optically clear adhesive (OCA) layers can be disposed between various layers/components shown in FIG. 1 in order to bond adjacent layers together in a manner that does not obstruct light passage through the layers of the display module 102. Any suitable OCA material can be used for the purpose of bonding adjacent layers of the display module 102 together.
[0030]The backlight unit 118 can be disposed behind the display layer (e.g., an LCD panel), and the backlight unit 118 can comprise multiple components that constitute the backlight unit 118. The backlight unit 118 is generally configured to project light that is emitted from a light source(s) of the backlight unit 118 in a direction towards the display layer 116 (i.e., in the positive z-direction and substantially perpendicular to the frontal plane, as shown in FIG. 1). The backlight unit 118 can include, (from top to bottom in FIG. 1), without limitation, a plurality of optical sheets 122 (or optical films), a light guide 124 (or light guide plate 124), one or more light sources 126, a reflector 128, and the thermal management structure 104.
[0031]The plurality of optical sheets 122 can be disposed behind the display layer 116 at the front of the backlight unit 118. The plurality of optical sheets 122 can be configured to control light that is emitted from the light source(s) 126 in a particular manner. The plurality of optical sheets 122 can be arranged in a stack and can comprise any suitable number of optical sheets. Although FIG. 1 shows three optical sheets 122, this number is illustrated merely for exemplary purposes and is not limiting on the number of optical sheets 122 that can be included in the backlight unit 118. The optical sheets 122 can include a diffuser sheet, a polarizer sheet, a filter sheet, and/or any other suitable type of optical sheet 122 for a display backlight unit 118.
[0032]The light guide 124 can be disposed behind the optical sheets 122 and is configured to distribute or diffuse the light emitted from the light source(s) 126 behind the display layer 116. The light guide 124 can be made of a plastic material and can include a series of unevenly distributed bumps that diffuse light in a particular manner e.g., generally an even distribution of light across an area of the light guide 124)
[0033]The light source(s) 126 can be disposed on substantially the same plane (parallel to the frontal plane) as the light guide 124. This coplanar arrangement of the light sour s) 126 and the light guide 124 can represent an edge-light type backlight unit 118. In some configurations, the light source(s) 126 can comprise a series of light emitting diodes (LEDs) arranged in a row and oriented such that the light emitted from the light source(s) 126 is directed toward the light guide 124. FIG. 1 shows a row of light sources 126(1) arranged along an axis that is parallel to the x-axis, and another row of light sources 126(2) arranged along an axis that is parallel to the y-axis. It is to be appreciated, however, that the display module 102 can comprise a single row of light sources 126(1) or 126(2), or multiple rows, as shown in FIG. 1, which can include rows of light sources 126 at two or more side edges of the light guide 124 (including two opposing side edges of the light guide 124). Furthermore, the light sources 126 can comprise an array of light sources 126 distributed over a substrate on a 2D plane that is parallel to the frontal plane of FIG. 1, and the substrate of light sources 126 can be disposed behind the optical sheets 122. In this scenario, the backlight unit 118 can represent a direct-light type backlight unit 118 where the light guide 124 can be omitted from the backlight unit 118.
[0034]The reflector 128 can be disposed behind the light guide 124 and the light source(s) 126, and is configured to reflect light toward the display layer 116 (i.e., in the positive z-direction of FIG. 1). For example, the light source(s) 126 can emit some light in the negative z-direction, which would be wasted light if it were not reflected in the positive z-direction. Thus, the reflector 128 can optimize the brightness of the display module 102.
[0035]The thermal management structure 104 can be disposed behind the reflector 128 and, in some configurations, the thermal management structure 104 can be in contact with the reflector 128. In some configurations, the reflector 128 can be omitted from the display module 102, in which case the thermal management structure 104 can be in contact with the light guide 124, or, if the backlight unit 118 is a direct-light type backlight unit 118, a substrate on which the light sources 126 are mounted. In any case, the thermal management structure 104 can be described as being disposed behind any one of the components situated in front of the thermal management structure 104 (i.e., situated a distance from the thermal management structure 104 in the positive z-direction). In this manner, the thermal management structure 104 is sometimes described herein as being disposed behind the display layer 116, even though components of the backlight unit 118 can be disposed in between the display layer 116 and the thermal management structure 104, in some configurations.
[0036]In this manner, the thermal management structure 104 is integrated on a backside of the display module 102. FIG. 1 shows a configuration where the thermal management structure 104 is a rear component of the backlight unit 118 that serves the additional purpose of a frame that supports the remaining components of the backlight unit 118 and holds them in place on a front external surface 130 of the thermal management structure 104. For example, the thermal management structure 104 can be in the shape of a five-sided box with an open front so that the remaining components of the backlight unit 118 can be disposed within a recess on the front side of the thermal management structure 104. For example, the reflector 128, the light guide 124, and the optical sheets 122 can be stacked within an open recess defined on the front of the thermal management structure 104 when the layers of the backlight unit 118 are assembled together. Said another way, the thermal management structure 104 can comprise one or more retainers disposed at a perimeter of the front external surface 130, the retainers protruding in a direction generally perpendicular to the front external surface 130 (i.e., in the positive z-direction). The retainers can be configured to retain the reflector 128, the light guide 124, the light source(s) 126, and/or the optical sheets 122 on the front external surface 130 of the thermal management structure 104. Thus, the thermal management structure 104 serves a structural purpose in supporting remaining components of the backlight unit 118 and creating rigidity or stiffness for the display module 102 itself.
[0037]It is to be appreciated that the thermal management structure 104 can wholly replace the metal frame that is typically found in a traditional backlight unit, where the traditional metal frame is much less structurally supportive than the thermal management structure 104. For example, today's overly-thin metal frames that are used in backlight units merely hold the optical sheets of the backlight unit like a paper tray holds paper, but they otherwise provide little structural support and serve no other useful purpose, yet they come at the cost of added thickness. These factors that compromise the mechanical strength of the electronic device detract from the user's touch experience on the display. They also detract from the perceived quality of the electronic device because thin and weak displays distort easily. Thus, by eliminating the traditional metal frame and replacing it with the thermal management structure 104 described herein, a thin device profile (as measured as a distance in the z-direction) can be maintained while providing additional technical improvements to the display module 102.
[0038]In some configurations, the front external surface 130 of the thermal management structure 104 can be configured to reflect light. In order to reflect light, the front external surface 130 can be made of a metal material that is polished during manufacturing to make the front external surface 130“light reflective.” Alternatively, a light-reflective film, or a light-reflective coating (e.g., silver plating) can be applied on the front external surface 130 of the thermal management structure 104. In any case, a reflective front external surface 130 can allow for the elimination of the reflector 128 from the backlight unit 118, and as such, the reflector 128 is a purely optional component of the display module 102. When the thermal management structure 104 can reflect light off of its front external surface 130, the omission of the reflector 128 can further reduce the thickness of the device profile to create an even thinner electronic device 100 (as measured as a distance in the z-direction).
[0039]The thermal management structure 104—as its name implies—can be configured to dissipate, or otherwise spread, heat in order to prevent the temperature inside the electronic device 100 from increasing, reduce the rate at which temperature increases inside the electronic device 100, or otherwise reduce the temperature inside the electronic device 100. Due to the density at which the components (many of which generate heat during operation) are often packed within a thin housing of the electronic device 100, the extent to which the electronic device 100 can use available computing power is limited by the temperature at which the electrical components within the device 100 operate. This is because these electrical components can overheat and become inoperable at a particular temperature threshold. This is especially true with today's tablet computing devices that pack all of the components into a single housing that is very thin. As electronic devices become thinner, cooling air paths become more obstructed, which creates an additional burden for existing thermal management systems. Fans are reaching their useful limit for controlling rising temperatures within electronic devices at today's thin standards. Moreover, displays themselves are also producing more heat due to the additional backlighting that is being supplied to meet the increasing demand for brightness. Thus, proper heat management allows for better utilization of the available computing power of the electronic device 100.
[0040]In addition, if the external surface temperature of the device's 100 housing increases above a particular threshold, the housing can become unsafe to touch with a bare hand or finger. A localized “hot spot” where the touch temperature rises to unsafe levels can be created at a location on the external housing where a heat-generating source is disposed. Accordingly, the thermal management structure's 104 ability to spread heat can mitigate the occurrence of these localized “hot spots,” thereby making the electronic device 100 safe to touch during operation. Thus, the thermal management structure 104 represents a passive heat management solution that is configured to manage the thermal load from various heat generating sources in the electronic device 100, such as the heat generating components 112 mounted on the logic board 110, and/or the light source(s) 126 of the backlight unit 118. Thus, the proximity of the thermal management structure 104 to the heat generating components 112, and to the light sources 126, makes the thermal management structure 104 more effective in dissipating the heat generated from those heat sources.
[0041]In some configurations, one or more of the heat generating components 112 can be coupled to a rear external surface of the thermal management structure 104. In some configurations, the coupling of the heat generating component(s) 112 to the rear external surface of the thermal management structure 104 can be accomplished using a thermal interface material a heat conductive paste or pad) that bonds the heat generating component(s) 112 to the rear external surface of the thermal management structure 104 and improves the efficiency of heat transfer from the heat generating component(s) 112 to the thermal management structure 104.
[0042]As will be described in more detail below, the thermal management structure's 104 heat dissipating characteristics can be enabled by a cavity defined within the thermal management structure 104, the cavity containing a material configured to change phase during operation of the electronic device. This material (sometimes referred to herein as a “phase change material”) can change phase from a solid to a liquid, or from a liquid to a gas, at a particular temperature within the temperature range of about 30° C. to about 110° C.
[0043]FIG. 2 illustrates a side, cross-sectional view of the example electronic device 100 of FIG. 1 along section A-A. Many of the same components introduced in FIG. 1 are shown in FIG. 2. FIG. 2 shows the structure of the thermal management structure 104 in greater detail, and also illustrates an example of how the components the electronic device 100 can be coupled together after assembly. For example, FIG. 2 shows that one or more heat generating components 112 can be mounted on the logic board 110 and coupled to a rear external surface 200 of the thermal management structure 104 using a thermal interface material (TIM) 202, as mentioned with reference to FIG. 1. The thermal interface material 202 can comprise a thermally conductive pad, paste, glue, or grease that is configured to reduce the thermal impedance between the heat generating component(s) 112 and the thermal management structure 104, allowing for a more efficient transfer of heat than an air gap would allow for. In some configurations, the light source(s) 126, such as an LED package, can be coupled to the thermal management structure 104 using the same, or a different, thermal interface material 202 as is used to couple the heat generating component(s) 112 to the thermal management structure 104. In this manner, the heat generated from the light source(s) 126 can also be more efficiently transferred to the thermal management structure 104.
[0044]The thermal management structure 104 is shown as being integrated on a backside of the display module 102 by virtue of the thermal management structure 104 being a rear-most component of the backlight unit 118. The front external surface 130 of the thermal management structure 104 is shown as being in contact with the reflector 128. In configurations where the reflector 128 is omitted, the front external surface 130 of the thermal management structure 104 can be in contact with the light guide 124 (or in contact with a substrate supporting an array of light sources 126 in a direct-light type backlight unit 118). Furthermore, retainers that protrude in a direction generally perpendicular from the front external surface 130 of the thermal management structure 104 can house the remaining components of the backlight unit 118, and can be coupled to the rear surface of the display layer 116.
[0045]The thermal management structure 104 is shown in FIG. 2 as comprising a cavity 204 that contains a phase change material 206 (i.e., a material configured to change phase during operation of the electronic device). In some configurations, the phase change material 206 is configured to change phase within a temperature range of about 30° C. to about 110° C. In some configurations, the temperature range in which the phase change material 206 changes phase can be from about 10° C. to about 130° C. In some configurations, the temperature at which the phase change material 206 begins to change phase can be at least about 10° C., at least about 15° C., at least about 20° C., at least about 25° C., at least about 30° C., at least about 35° C., or at least about 40° C. In some configurations, the temperature at which the phase change material 206 begins to change phase can be no greater than about 130° C., no greater than about 125° C., no greater than about 120° C., no greater than about 115° C., no greater than about 110° C., no greater than about 105° C., or no greater than about 100° C.
[0046]In some configurations, the phase change material 206 changes phase from a liquid to a gas at a temperature within a suitable temperature range, as described herein. In this scenario, the cavity 204 of the thermal management structure 104 can represent a vapor chamber, and the phase change material 206 can be considered to be the “working fluid” of the vapor chamber. In this configuration, a first portion of the phase change material 206 is in a liquid state and a second portion of the phase change material 206 is in a gaseous state. As the electronic device 100 is operated and heat sources (e.g., the heat generating component(s) 112 on the logic board 110, the light source(s) 126, etc.) within (or external to) the electronic device 100 generate heat, the generated heat is transferred through the heat conductive material of the thermal management structure 104 where the temperature of the phase change material 206 (in this case, a working fluid/liquid) increases. When the liquid portion of the phase change material 206 reaches a particular temperature, the liquid portion starts to change from a liquid form to a gaseous form. Gas expands and moves to cold regions inside the cavity 204 where the gas condenses into a liquid, and the condensed liquid then moves back to the hotter regions to create an internal cycle that continually dissipates heat by virtue of the cyclic vaporizing and condensing of the liquid and gas phases, respectively. In this configuration, the phase change material 206 can comprise any suitable working fluid, including, without limitation water (e.g., deionized water), ammonia, ethanol, methanol, acetone, mercury, and/or similar materials with a phase transition temperature within a suitable temperature range, as described herein.
[0047]The material of the thermal management structure 104 is heat conductive material, and is to be compatible with the phase change material 206 in the scenario where the phase change material 206 changes from a liquid to a gas during the phase change. “Compatibility,” in this context means two materials that do not result in the development of corrosion, oxidation, or the like, which can affect the purity of the phase change material 206 and cause the internal cooling cycle to stop working. Depending on the working fluid chosen for the phase change material 206, the heat conductive material of the thermal management structure 104 can include, without limitation, a metal, such as copper, aluminum, stainless steel, titanium, or the like. Copper is known to be compatible with water as the working fluid, and copper has a high thermal conductivity relative to other suitable metals that can be used for the heat conductive material of the thermal management structure 104. Aluminum is known to be compatible with ammonia as the working fluid. However, any suitable combination of compatible materials for the thermal management structure 104 and the phase change material 206 are contemplated herein. A thermal management structure 104 made of copper and including a cavity 204 containing water as a working fluid is known to have a thermal conductivity on the order of 3000 watts per meter kelvin. Integrating such a thermal management structure 104 on a backside of the display module 102 to leverage the large area of the display can provide an efficient and effective heat management solution for the electronic device 100.
[0048]In some configurations, the phase change material 206 changes phase from a solid to a liquid at a temperature within a suitable temperature range, as described herein. In this scenario, the thermal management structure 104 acts as a “thermal battery.” In the thermal battery context, heat is transferred to the thermal management structure 104, causing the temperature of the phase change material 206 to rise to its melting point and change from solid form into a liquid form. Once all of the solid changes to a liquid, the efficacy of the thermal management structure 104 (in terms of cooling the electronic device 100) declines. This is due to the fact that the temperature of the phase change material 206 stays constant during the phase change from solid to liquid until enough energy is put into the system to overcome the latent heat of the system, and then the temperature of the phase change material 206 (now in liquid form) begins to rise again as more heat is generated. In this scenario, the electronic device 100 can operate at a high workload in teats of processing power, and the temperature inside the electronic device 100 (during the phase change of the phase change material 206) will stay substantially constant.
[0049]If the workload of the electronic device 100 decreases (or ceases) before all of the solid changes to a liquid, the temperature may decrease, causing the liquid to return to a solid state, and the thermal management structure 104 can thereafter be re-used as a passive heat management solution when the workload increases at a subsequent point in time. This “thermal battery” configuration—where the phase change material 206 changes from a solid to a liquid at a temperature within a suitable temperature range, as described herein—is ideal for dissipating heat during intermittent peak usage of the electronic device 100. In this configuration, the phase change material 206 can comprise any suitable solid-to-liquid phase change material, including, without limitation wax, naphthalene, and/or any similar material with a melting point within a suitable temperature range, as described herein. The vapor chamber configuration—where the phase change material 206 changes from a liquid to a gas at a temperature within a suitable temperature range, as described herein—is better (as compared to the thermal battery configuration) for dissipating heat during sustained high workloads of the electronic device 100.
[0050]The cavity 204 inside the thermal management structure 104 is sealed and, in some configurations, a vacuum is created inside the cavity 204. Furthermore, the cavity 204 can be any size depending on the configuration. FIG. 2 shows the cavity 204 spanning substantially the entire length (or width) of the thermal management structure 104 (and the display module 102) in the x-direction. The cavity 204 can also span substantially the entire width (or length) of the display in the y-direction. Thus, the area of the cavity 204 can be substantially equal to the area of the display (in a plane that is parallel to the frontal plane) to take advantage of the large area of the display, which can be used for spreading heat across the entire electronic device 100. Said another way, a viewable portion of the display module 102 can be defined by an area of the display layer 116 (e.g., the area of an LCD panel) as defined in a plane parallel to the x-y plane, or to the frontal plane shown in FIG. 1. The area of the cavity 204, as defined by its x-dimension multiplied by its y-dimension, can be substantially equal to the area of the display layer 116. “Substantially equal” in this context means a difference between the area of the display layer 116 and the area of the cavity 204 can be due to the wall thickness, w, of the side walls that define part of the cavity 204, as shown in FIG. 2. In some configurations, the wall thickness, w, can be on the order of 0.3 mm. Thus, if the area of the cavity 204 is calculated by a cavity length on the x-axis multiplied by a cavity width on the y-axis, then the area of the cavity 204 can be considered to be “substantially equal” to the area of the display layer 116 (as defined in respective planes that are parallel to the frontal plane) if the area of the cavity 204 is less than the area of the display layer 116 by about 0.6*cavity width+0.6*cavity length−0.36 (assuming a uniform wall thickness, w, around all four sides of a rectangular cavity 204). Although the cavity 204 can span substantially the entire display area, as described herein, the size of the cavity 204 is not so limited. Rather, the cavity 204 can be of any suitable size, as described in more detail below. Furthermore, the thermal management structure 104 can comprise more than one cavity 204, in some configurations.
[0051]It is to be appreciated that, though the heat sources within the electronic device 100 that generate the most heat (e.g., one or more CPUs) may be on the logic