Embodiments of the invention relate generally to electronic devices and, more particularly, to a system for providing thermal management of electronic devices in a balanced fashion and via multiple thermal pathways.
Small form electronic devices, such as handheld computing devices (e.g., smart phones, tablet computers e-book readers, etc.) and embedded computing systems, present significant thermal management challenges. There is ongoing user demand for devices that are not only smaller form factor for greater portability but also powerful enough to handle video and other computing intensive tasks. The provision for significant computing power in a relatively small form device often translates into the need for significant thermal management of the heat dissipating devices.
One common solution used to transfer heat from a processor in a small form device includes the use of a heat spreader that is in thermal contact with the processor or active device/component. The heat spreader is in turn, in thermal contact with a heat exchanger via a heat pipe or other structure—with the heat exchanger often including an air mover, such as a fan, that vents air to the external ambient by way of a small vent.
It is recognized, however, that conventional thermal management systems such as the one described above have known limitations and drawbacks associated therewith. As one example, it is recognized that in such conventional thermal management systems only one mechanism is in place to remove the heat—that being the heat pipe and heat exchanger connected to a surface of the processor/active device. Therefore, if the heat pipe or a component of the heat exchanger were to fail (e.g., the fan in the heat exchanger plugging with dust), a potential thermal runaway could occur that causes overheating and/or damage to the device to occur.
As another example, even during normal operation of a conventional thermal management system, it is recognized that a portion of the heat generated by the processor or active component is not transferred to the heat pipe, but travels through a back surface of the processor (i.e., surface not connected to the heat pipe) to the printed circuit board (PCB) on which the processor is mounted. Accordingly, this portion of the heat that goes from the processor to the PCB has a poor thermal management, and this heat can have a thermal impact on neighboring devices, as well as create localized hot spots on the PCB. Given the fact that, in many applications, the PCB is in a close proximity to the case/skin of the computing device, heat transferred to the PCB can therefore also lead to hot spots on the case/skin, with which a user may come in contact with.
Still another potential pitfall associated with the conventional thermal management system just described is the issue of both acoustic and electrical noise associated with a cooling fan. Such issues can be reduced though not completely eliminated through the use of appropriate noise filtering circuitry and fan and vent design. However, there remains the issue of power consumption to run the fan.
Therefore, it would be desirable to provide a thermal management system for small form electronic devices that overcomes the aforementioned drawbacks, with such a system providing multiple thermal pathways, greater reliability, and reduced power consumption and acoustic noise generation.
In accordance with one aspect of the invention, an electronic device includes an outer case generally defining an internal volume, a circuit board positioned within the internal volume and having a first surface and a second surface, one or more active components mounted on the first surface of the circuit board, and a thermal management system configured to provide cooling for the one or more active components. The thermal management system further includes a first heat spreader in thermal contact with at least one active component of the one or more active components, a second heat spreader in thermal contact with the second surface of the circuit board, a thermal carrier coupled to each of the first heat spreader and the second heat spreader to remove thermal energy therefrom, and a heat exchanger coupled to the thermal carriers to receive thermal energy therefrom and dissipate the thermal energy, wherein one thermal carrier is routed between the first heat spreader and the heat exchanger and the other thermal carrier is routed between the second heat spreader and the heat exchanger.
In accordance with another aspect of the invention, an electronic device includes an outer case generally defining an internal volume, a circuit board positioned within the internal volume and having a first surface and a second surface, one or more active components mounted on the first surface of the circuit board, and a thermal management system configured to provide cooling for the one or more active components. The thermal management system further includes a first heat spreader in thermal contact with at least one active component of the one or more active components and a second heat spreader in thermal contact with the second surface of the circuit board, wherein the second heat spreader is also in thermal contact with the outer case, such that thermal energy is transferred to the case and spread thereacross, so as to dissipate the thermal energy.
In accordance with yet another aspect of the invention, a method for removing heat from an electronic device includes thermally coupling a first heat spreader with at least one heat generating active component mounted on a first surface of a circuit board and thermally coupling a second heat spreader with a second surface of the circuit board that is opposite the first surface of the circuit board, such that the first heat spreader and the second heat spreader form a thermal clamp about the at least one heat generating active component and the circuit board, so as to provide double-sided heat removal therefrom. The method also includes thermally coupling the second heat spreader with an outer case of the electronic device, coupling a thermal carrier to each of the first heat spreader and the second heat spreader to remove heat therefrom that is generated by the at least one active component, and coupling the first and second thermal carriers to a single heat exchanger such that the heat exchanger receives heat from the thermal carriers and dissipates the heat.
Various other features and advantages will be made apparent from the following detailed description and the drawings.
The drawings illustrate preferred embodiments presently contemplated for carrying out the invention.
In the drawings:
Embodiments of the invention relate generally to cooling electronics systems and, more particularly, to a thermal management system that utilizes multiple thermal paths to provide cooling to active components and other devices in such electronics systems.
Various types of small form electronics systems or devices may benefit from incorporation of embodiments of the invention, including handheld computing devices such as smart phones, tablet computers and e-book readers, as discussed herein. However, it is recognized that embodiments of the invention are not limited only to use with such handheld computing devices and that embodiments of the invention may be employed in other electronics system, such as embedded computing systems. Accordingly, the scope of the invention is not meant to be limited by the specific embodiments set forth here below.
Referring to
Additional details of the electronic device 10 may be understood by referring to
A circuit board 22 is positioned in the internal volume 16 and may be secured to an underside of the peripheral shelf 20 by way of one or more screws (not shown) or other fasteners. The circuit board 22 may be a system board, a daughter board or other type of printed circuit board and composed of a variety of materials, such as well-known ceramics, organic materials such as one or more epoxy layers or other materials. The circuit board 22 includes plural surface and/or internal conductor traces (not visible) interconnected by vias as desired—with the circuit board having a front surface 24 and back surface 26. Depending on the complexity of the electronic device 10, the circuit board 22 may be populated by numerous components.
A few exemplary components are shown in
A thermal management system 32 is also included in the device 10 that is designed to keep the temperature of the active (and passive) components 28, 30 and the exterior surface of the case 12 (i.e., skin 34) within acceptable/comfortable limits. The thermal management system 32 functions to provide a balanced thermal management to the electronic device 10 by providing a plurality of thermal pathways to remove heat from the active component 28, as well as from the other components 3 and from the circuit board 22.
As shown in
According to an exemplary embodiment of the invention, the main and secondary thermal carriers 36, 38 are in the form of heat pipes. At the hot interface of each heat pipe 36, 38—where the heat pipe is in thermal contact with the active component 28 or the circuit board 22—a liquid within the heat pipe 36, 38 that is in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe 36, 38 to the cold interface—where the heat pipe 36, 38 is connected to the heat exchanger 42—and condenses back into a liquid, thereby releasing the latent heat. The liquid then returns to the hot interface through either capillary action, centrifugal force, or gravity, and the cycle repeats. Due to the very high heat transfer coefficients for boiling and condensation, heat pipes are highly efficient thermal conductors (e.g., effective thermal conductivity can approach 100,000 W/m K).
It is recognized, however, that the main and secondary thermal carriers 36, 38 may be provided in other forms and as other devices. That is, rather than being provided as heat pipes, the thermal carriers may take the form of vapor chamber (i.e., a metal container that has two phase flow movement), or a metal or high thermal conductive carrier.
As shown in
The end 46 of secondary thermal carrier 38 is coupled to or integrated with a separate heat spreader 52 (e.g., metal plate), such as via solder bonding for example, with the secondary thermal carrier 38 and heat spreader 52 being positioned adjacent the back surface 26 of the circuit board 22. The heat spreader 52 is placed in thermal contact with the circuit board 22 via an electrically insulating and relatively compliant thermal pad 54 positioned between the heat spreader 52 and the circuit board 22, with a surface of the heat spreader being secured to the thermal pad either via the inherent tackiness of the thermal pad 54 or via fasteners (not shown). The thermal pad 54 may be composed of relatively compliant heat transfer materials such as TFlex 740 or 340 from Laird or dispensable polymeric materials such as T570 or T630 from Chomerics. In this way, heat is transferred not only from the active component 28 but also from other heat generating components 30 that may be present on the surface 24 of the circuit board 22.
While heat is removed from the back side 26 of the circuit board 22 via the secondary thermal carrier 38 and heat spreader 52, heat is also removed from the back side of the circuit board 22 via the thermal coupling of the circuit board 22 to the case 12 of electronic device 10. As shown in
In combination, the heat spreader 48 and heat spreader 52 form a “thermal clamp” about the circuit board 22 and the components 28, 30 thereon, to provide for double-sided heat removal therefrom. For dissipating the heat removed from the circuit board 22 and components 28, 30 by the thermal clamp 48, 52, multiple thermal pathways are provided from the heat spreaders 48, 52—including the thermal carriers 36, 38 connected between the heat spreaders 48 and 52 and the heat exchanger 42, and the thermal pad 56 connected between heat spreader 52 and the case 12.
Referring still to
The heat sink 58 of heat exchanger 42 is of standard construction and thus may be constructed of aluminum, for example, or another metal having a relatively high thermal conductivity, such as a copper or a copper-aluminum combination. As depicted in
According to embodiments of the invention, the air mover 60 of heat exchanger 58 may take one of several forms. As one example, the air mover 60 may be a fan of standard type that is powered to direct an air flow across heat sink 58. As another example, and in a preferred embodiment, the air mover 60 is formed of one or more synthetic jet actuators that are powered to direct an air flow across heat sink 58. The general structure of a synthetic jet (and mechanism for mounting the synthetic jet) that could be utilized as the air mover 60 of heat exchanger 58 is shown and described in
Referring first to
Referring now to
Actuators 82, 84 are coupled to respective first and second plates, 74, 76 to form first and second composite structures or flexible diaphragms 86, 88, which are controlled by driver 70 via a controller assembly or control unit system 90. For example, each flexible diaphragm 86, 88 may be equipped with a metal layer and a metal electrode may be disposed adjacent to the metal layer so that diaphragms 86, 88 may be moved via an electrical bias imposed between the electrode and the metal layer. As shown in
In one embodiment, actuators 82, 84 are piezoelectric motive (piezomotive) devices that may be actuated by application of a harmonic alternating voltage that causes the piezomotive devices to rapidly expand and contract. During operation, control system 90 transmits an electric charge, via driver 70, to piezoelectric actuators 82, 84, which undergo mechanical stress and/or strain responsive to the charge. The stress/strain of piezomotive actuators 82, 84 causes deflection of respective first and second plates 74, 76 such that a time-harmonic or periodic motion is achieved that changes the volume of the internal chamber 72 between plates 74, 76. The resulting volume change in internal chamber 72 causes an interchange of gas or other fluid between internal chamber 72 and the exterior volume, with a gas being drawn into the internal chamber 72 through orifice 80 when first and second plates 74, 76 move outward and the volume of the internal chamber 72 is increased—generally indicated in phantom by 92—and with a gas being ejected from the internal chamber 72 through orifice 80 as a cooling jet when first and second plates 74, 76 move inward and the volume of the internal chamber 72 is decreased—generally indicated in phantom by 94.
Beneficially, embodiments of the invention thus provide a thermal management system 32 for a small form electronic device, such as a smart phone, tablet computer, e-book reader, or embedded computing system, for example. The thermal management system 32 provides a balanced thermal management of the electronic device from different directions via the use of multiple thermal carriers 36, 38 and heat spreaders 48, 52. The thermal carriers 36, 38 conduct heat from various surfaces of a circuit board 22, and components 28, 30 thereon, away to a heat exchanger 42 for dissipation to the ambient environment. Additionally, a thermal path is provided from the circuit board 22 to the case 12 of the electronic device—with heat from the circuit board 22 being spread across the case 12 in such a fashion as to reduce the hot localized skin temperature of the device.
The multiple and balanced thermal pathways in thermal management system 32 provide for dissipation of heat generated by the components 28, 30, even in the event that a thermal carrier 36, 38 or the heat exchanger 42 (e.g., air mover 60 in the heat exchanger) fails, thereby preventing a potential thermal runaway that might occur in a typical cooling system were the thermal carrier or the heat exchanger to fail. The multiple and balanced thermal pathways in thermal management system 32 also allow for the air mover 60 of the heat exchanger to operate at a reduced load and/or for the air mover 60 to operate less frequently. This reduced operation of the air mover 60 can reduce the lower acoustic noise and mechanical vibration in the heat exchanger 42.
Therefore, according to one embodiment, an electronic device includes an outer case generally defining an internal volume, a circuit board positioned within the internal volume and having a first surface and a second surface, one or more active components mounted on the first surface of the circuit board, and a thermal management system configured to provide cooling for the one or more active components. The thermal management system further includes a first heat spreader in thermal contact with at least one active component of the one or more active components, a second heat spreader in thermal contact with the second surface of the circuit board, a thermal carrier coupled to each of the first heat spreader and the second heat spreader to remove thermal energy therefrom, and a heat exchanger coupled to the thermal carriers to receive thermal energy therefrom and dissipate the thermal energy, wherein one thermal carrier is routed between the first heat spreader and the heat exchanger and the other thermal carrier is routed between the second heat spreader and the heat exchanger.
According to another embodiment, an electronic device includes an outer case generally defining an internal volume, a circuit board positioned within the internal volume and having a first surface and a second surface, one or more active components mounted on the first surface of the circuit board, and a thermal management system configured to provide cooling for the one or more active components. The thermal management system further includes a first heat spreader in thermal contact with at least one active component of the one or more active components and a second heat spreader in thermal contact with the second surface of the circuit board, wherein the second heat spreader is also in thermal contact with the outer case, such that thermal energy is transferred to the case and spread thereacross, so as to dissipate the thermal energy.
According to yet another embodiment, a method for removing heat from an electronic device includes thermally coupling a first heat spreader with at least one heat generating active component mounted on a first surface of a circuit board and thermally coupling a second heat spreader with a second surface of the circuit board that is opposite the first surface of the circuit board, such that the first heat spreader and the second heat spreader form a thermal clamp about the at least one heat generating active component and the circuit board, so as to provide double-sided heat removal therefrom. The method also includes thermally coupling the second heat spreader with an outer case of the electronic device, coupling a thermal carrier to each of the first heat spreader and the second heat spreader to remove heat therefrom that is generated by the at least one active component, and coupling the first and second thermal carriers to a single heat exchanger such that the heat exchanger receives heat from the thermal carriers and dissipates the heat.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
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Number | Date | Country | |
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20150342023 A1 | Nov 2015 | US |