Abstract:
A media device includes at least one piezoelectric fan selectively located to draw or urge air past one or more electrical components, such as an integrated circuit chip. Preferably, the piezoelectric fan is located within a channel milled or otherwise formed in the chip, however the fan may be located proximate the channel yet in fluid communication therewith. The piezoelectric fan operates to convectively cool the electrical component and may also prevent heat that has been generated by the electrical component from moving toward another electrical component within the media device. Thus, the configuration and location of the piezoelectric fan may advantageously cool one component while preventing heat energy from building up around one or more other components mounted nearby.

Description:
BACKGROUND 
     A media device, which may take the form of a set top box (STB), is configured to deliver selected media content and typically connects to a flat screen television and an external signal source in which the signal (e.g., cable signal) is converted into viewable media content. However, the media device may operate with other systems such as, but not limited to, other televisions (TVs), personal computers (PCs), stereos, personal digital assistants (PDAs), surround-sound systems, and digital video recorders (DVRs). Particular media content may be selected by a user who provides instructions to the media device. The selected media content may then be presented to the user. For example, if the selected media content is a movie, the video portion of the movie is displayed on a screen of the TV, a monitor of the PC, or some other display medium. The audio portion of the movie may concurrently be presented over the speakers of the TV, the stereo, or the surround-sound system. In some instances, the selected media content may be stored into a DVR or other recording device for later retrieval and presentation. The DVR may be an integrated component of the media device, or the DVR may be a stand-alone device that is communicatively coupled to the media device. 
     For a variety of reasons such as consumer demand, portability, spatial constraints and aesthetics, the tendency in the marketplace has been toward more streamlined components still capable of providing a high quality media content (e.g., flat screen televisions and small, wall mounted speakers). However, one of the continual challenges of making a low profile, streamlined media device remains the heat transfer issues to or from various electrical components within the media device, where such electrical components are typically mounted on a printed circuit board (PCB). Conventional media devices generally promote heat transfer with an active cooling system that employs one or more convention fans or blowers having rotating blades to move air through the media device. Some drawbacks of a conventional fan are the amount of spatial envelope needed within the media device to mount and adequately operate the fan, noise generated by the operating fan, the additional heat generated by the operating fan, and a limited operational life due to mechanical or environmental wear or stress. 
     SUMMARY 
     A media device, which may take the form of a set top box, includes a piezoelectric fan selectively located to push or pull air past an electrical component, such as an integrated circuit chip (IC chip) having a hot die, a microprocessor chip, a memory chip, etc. In one embodiment, the piezoelectric fan is selectively located within a channel milled or otherwise formed in the chip. In another embodiment, the piezoelectric fan is located with a channel formed within a panel of a chassis for the media device. The chassis for the media device generally includes a top panel, side or rim panels, and a bottom panel. The piezoelectric fan operates to convectively cool the electrical component and may be arranged to prevent heat generated by the electrical component from moving toward an adjacent electrical component also mounted to the circuit board. 
     In accordance with one aspect, a system includes a chassis having at least one panel with opposing surfaces, and one of the opposing surfaces is exposed to an ambient environment. A circuit board is located within the chassis with at least one electrical component mounted on the circuit board. The electrical component includes a channel or duct formed therein. A piezoelectric fan is located within the chassis to generate a thermally convective flow of air proximate the electrical component, which may include generating an air flow along the channel formed in the electrical component. 
     In accordance with another aspect, a system includes a chassis having a top panel with an interior surface and an exterior surface. The exterior surface is exposed to an ambient environment. A heat shield extends from the interior surface and includes an upper end portion coupled to the top panel and a free end portion distal from the upper end portion. A circuit board is located within the chassis and has at least two electrical components mounted proximate each other on the circuit board. The electrical components are spaced apart such that the free end portion of the heat shield extends into the spaced apart region. One of the electrical components includes a channel formed therein. A piezoelectric fan located within the chassis generates air flow along the channel and beneath the free end portion of the heat shield. 
     In accordance with yet another aspect, a method for cooling within a media device includes (1) activating a piezoelectric fan to generate an air flow within the media device; (2) directing the air flow through a channel formed in an electrical component mounted on a circuit board within the media device; and (3) convectively transferring heat from the electrical component to another region within the media device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings may not be necessarily drawn to scale. For example, the shapes of various elements, thicknesses and angles may not be drawn to scale, and some of these elements may be arbitrarily enlarged or positioned to improve drawing legibility. Preferred and alternative embodiments are described in detail below with reference to the following drawings: 
         FIG. 1  is an exploded, cross-sectional, schematic view of a media device having a piezoelectric fan arranged in a channel of an electrical component in accordance with one embodiment; 
         FIG. 2  is a perspective view an electrical component having a channel and a piezoelectric fan positioned within the electrical component in accordance with another embodiment; 
         FIG. 3  is a cross-sectional view of an electrical component having a lid with a channel and further having a piezoelectric fan positioned to generate an air flow through the channel in accordance with another embodiment; and 
         FIG. 4  is a cross-sectional view of an electrical component having another lid with a channel and further having a piezoelectric fan positioned to generate an air flow through the channel in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic, cross-sectional view of a media device  100 , otherwise referred to as a set top box (STB), having a low-profile, two-piece chassis  102 . The chassis  102  includes a top panel  104  and a bottom panel  106 . The top panel includes an interior surface  103  and an exterior surface  105 , in which the latter is exposed to an ambient environment  107 . Arranged within the chassis  102  is a circuit board  108 , such as a printed circuit board (PCB), and at least two electrical components  110 ,  112  mounted to the circuit board  108 . 
     The term “low-profile” as used herein broadly refers to an external spatial envelope taken up by the assembled media device  100 . A low-profile chassis may take the form of an enclosure whose dimensions are dictated by the physical size of the internal components necessary for providing product feature and function with little or no additional capacity/expansion in the enclosure&#39;s envelope for supporting active or passive cooling components. By way of example, the low-profile chassis  102  may have a height of about 8.0 mm to about 25.4 mm. In use, the low-profile chassis  102  may be spatially oriented in a variety of ways, such a vertically behind a wall mounted television or horizontally on a shelf or media cabinet. Thus, the directional references used herein are for interpretation of the drawings and are not meant to limit the scope of the invention. For example, convective or conductive heat transfer may occur in a variety of directions regardless of the two-dimensional examples shown in the drawings. 
     The media device  100  may include a heat transferring unit  114 , which provides a thermally conductive path from the component being cooled  110  to the chassis  102 . The conductive path may include one or more additional layers, such as, but not limited to a thermal interface layer  116  and a gap filling layer  118 , where one or both layers may provide a means to account for physical, dimensional tolerance adjustments within the media device  100  and/or provide bonding means between the respective components. 
     The electrical components  110 ,  112  may have similar or different configurations and/or functions, for example the electrical component  110  includes a hot die  122  while the other electrical component  112  does not. In the illustrated embodiment, the electrical component  110 , includes a channel  120  formed therein to support a piezoelectric fan  124 , which may push or pull air around other components mounted on the circuit board  108 , prevent hot air caused by radiated heat to build up around the hot die  122 , or some combination thereof. By way of example, the electrical components may take the form of integrated circuit chips (IC chips) with or without the hot die  122 , microprocessor chips, or memory chips, and the components  110 ,  112  may perform different functions and/or have different configurations. 
     The chassis  102  optionally includes a heat shield  126 , which may also take the form of a heat bridge or some combination of a shield and a bridge. The heat shield  126  may be integrally formed with the chassis  102 . The heat shield  126  includes an upper end portion  128  coupled to the top panel  104  and a free end portion  130  distally located from the upper end portion  128 . Preferably, the free end portion  130  does not contact the circuit board  108  after the media device  100  has been fully assembled. Stated otherwise, the free end portion  130  is spaced apart from the circuit board  108 . 
     The piezoelectric fan  124  is arranged proximate to or supported in the channel  120  to push or pull air toward the hot die  122  and to contemporaneously move air past the heat shield  126  as indicated by directional air flow arrows  132 . In one embodiment, the piezoelectric fan  124  includes a flexible blade attached to a ceramic element, and the blade is set in motion by applying a minimal (e.g., low power) alternating current (AC) or a minimal, pulsing direct current (DC) to the ceramic element. The blade is typically made of Mylar, and the ceramic element is typically a piezoceramic bending element. The minimal current of electricity causes the piezoceramic to elongate and contract, which in turn bends the blade back and forth to impart a flapping action of the blade or blades that directs a desired rate of air flow in a desired direction. The length and thickness ratios of the piezoceramics and the blades may be customized to provide an appropriate amount of air flow to convectively transfer heat from a variety of electrical components as arranged within different types and different sized media devices. 
     The piezoelectric fan  124  may have a variety of advantages over conventional fans or blowers. For example, the piezoelectric fan  124  allows the chassis  102  of the media device  100  to be low profile (e.g., thinner) as compared to a media device having a conventional fan with rotating blades. The piezoelectric fan  124  may require less power than a convention fan while producing negligible heat. Moreover, the piezoelectric fan  124  does not have any bearings or wearing parts and is much quieter, if not essentially noiseless, as compared to conventional fans. 
       FIG. 2  shows an assembly  200  within a media device (not shown). The assembly  200  includes an electrical device  202  mounted on a circuit board  204 . The electrical device  202  includes a body  206 , a lid  208 , a hot die  210  located within the body  206 , and a piezoelectric fan  212  also located within the body  206 . The electric device  202  may take the form of a pre-fabricated integrated circuit chip in which the hot die  210  and the fan  212  are installed using known semiconductor assembly techniques. The fan  212  is positioned within the body  206  to move (e.g., push or pull) air  216  through a channel  214  formed in the body  206 . The channel  214  is shown as an open channel or trench that may be etched, machined or otherwise formed in the body  206 . Alternatively, the channel  214  may be a closed channel or duct, may have various shapes (e.g., square, round, oval, rectangular, etc.), and may be aligned as illustrated or have a curve or bend. The piezoelectric fan  212  may situated toward one end of the body  206  to move air either toward or away from the hot die  210 . 
       FIG. 3  shows a cross-sectional view of another assembly  300  having a chip  302  mounted on a circuit board  304 . A hot die  306  is located within the chip  302 , which in turn is covered with a lid  308  having a channel  310 . In the illustrated embodiment, the lid  308  has a C-shape with an open side of the “C” facing downward toward the hot die  306 . A piezoelectric fan  312  may be located on a bridge portion  314  of the chip  302  or positioned outside of the chip  302 , yet aligned with the channel  310 . Alternatively, the fan  312  may be mounted or bonded to the lid  308 . The channel  310  is preferably wide enough to permit a sufficient amount of air flow at a sufficient rate to convectively transfer heat generated by the hot die  306  within the chip  302 . The assembly  300  may further include a heat spreader  316  in thermally conductive contact with the lid  308 . 
       FIG. 4  shows a cross-sectional view of still another assembly  400  having a chip  402  mounted on a circuit board  404 . A hot die  406  is located within the chip  402 , which in turn is covered with a lid  408  having a channel  410 . In the illustrated embodiment, the lid  408  has a C-shape with an open side of the “C” facing upward such that a piezoelectric fan  412  may be supported on a portion of the lid  408 . Again, the channel  410  is preferably wide enough to permit a sufficient amount of air flow at a sufficient rate to convectively transfer heat generated by the hot die  406  within the chip  402 . While the channel  410  is shown formed in the lid  408 , it is understood that a channel or duct may be part of or formed in other mechanical parts within the chassis, and thus the location of the channel is not limited to just the electrical component and/or the lid. A heat spreader  414  may optionally be in thermally conductive contact with the lid  408 . 
     It should be emphasized that the above-described embodiments are merely possible examples of implementations of the invention. Many variations and modifications may be made to the above-described embodiments. For example, the piezoelectric fan may be positioned to push or pull air through a duct instead of an open channel. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.