Abstract:
An LED light arrangement is provided. The light arrangement includes LED light emitting components mounted to a flexible circuit board having a flexible graphite substrate. The flexible circuit board includes a dielectric layer formed an the surface of the flexible graphite substrate and an electrically conductive layer formed on the surface of the dielectric. The high in-plane thermal conductivity graphite substrate provides enhanced heat transfer capability to effectively move of heat away from the electronic components for improved cooling of the heat generating light emitting component and surrounding devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/029073 filed Jul. 25. 2014. 
       TECHNICAL FIELD  
       [0002]    The present invention relates to a circuit board having a flexible graphite substrate with examples including flexible circuit board arrangements having a flexible graphite substrate with a dielectric layer and at electrically conductive layer and one or more electronic components mounted to the flexible graphite substrate to form an electrical circuit arrangement. The circuit arrangement can include LED light arrangements for a display device. 
       BACKGROUND 
       [0003]    With the development of more and more sophisticated electronic components, relatively extreme temperatures can be generated. This is clearly true with respect to electronic components capable of increasing processing speeds and higher frequencies, having, smaller size and higher power density requirements, those generating new lighting advancements or exhibiting other technological advances. These components include microprocessors a id integrated circuits in electronic and electrical devices and systems as well as in other devices such as high power optical devices. However, microprocessors, integrated circuits and other sophisticated electronic components typically operate efficiently only under a certain range of threshold temperatures. The excessive heat generated during operation of these components can not only harm their own performance, but can also degrade the performance and reliability of the overall system and can even cause system failure. The increasingly wide range of environmental conditions, including temperature extremes, in which electronic systems are expected to operate, exacerbates these negative effects. 
         [0004]    With the increased need for heat dissipation from electronic devices caused by these conditions, thermal management becomes an increasingly important element of the design of electronic products. As noted, both performance reliability and life expectancy of electronic equipment are inversely related to the component temperature of the equipment. For instance, a reduction in the operating temperature of a device such as a typical silicon semiconductor can correspond to an exponential increase in the reliability and life expectancy of the device. Therefore, to maximize the life-span and reliability of a component, controlling the device operating temperature within the limits set by the designers is of paramount importance. 
         [0005]    Electronic components are typically mounted to a circuit hoard, also known as a printed circuit board (PCB). The PCB has electrically conductive elements arranged to form an electrical circuit. With traditional PCBs, such as FR4 PCBs, and metal core printed circuit boards (“MCPCB”), the electrically conductive elements are arranged on a substrate. An example of a conventional substrate include Fiber reinforced boards, commonly used as FR4 PCBs. Another example of a conventional substrate is a metal base layer, such as for example aluminum, copper, or other known metal which are typically used in MCPCBs and IMSPCBs. Another example of a conventional substrate is ceramics and ceramic compositions. 
         [0006]    It is desirable to improve the thermal management of circuit boards to address the needs discussed above. 
         [0007]    A liquid crystal display, or LCD, is a display apparatus that utilizes an image display panel formed of two transparent sheets of polarizing material separated by a liquid containing rod-shaped crystals where the polarizing areas of the two sheets are align-d perpendicular to each other. The LCD is constructed to display an image by passing an electric current through the liquid that causes the crystals to align to block light. Each crystal can be controlled individually and acts like a shutter. When the current is applied to specific pixel-like areas, those crystals align to create dark area, or images. The dark areas are combined with light areas to create text and images on the panel. LCD panels do not emit light. Instead, they control how light which is emitted from an external source passes through the LCD and onto the screen to form an image. LEDs are typically used as the light source. The LCDs are back-lit or side-lit by the LEDs depending on the arrangement used. 
         [0008]    As manufacturers continually improve the performance of LCD displays, such as by increasing the display&#39;s brightness ever-brighter LEDs are being utilized. As a result, the power consumption of the LEDs has increased substantially. LEDs convert at least 70% of their power to heat. The heat generated in the light source is detrimental to the operation and viewing of a liquid crystal display. The light source discharge heat that is transferred to the image display panel, other electrical components in liquid crystal display, and the support structure of the liquid crystal display. Indeed, some of the electrical components in the display panel are themselves heat sources which compounds the problem. However, these other components of the liquid crystal display normally possess poor thermal spreading properties and are not normally designed to dissipate heat front the light source, especially in directions parallel to the image display panel face. 
         [0009]    In addition, the illuminating light of a liquid crystal display remains in an energized state and at a consistent power level regardless of the image characteristics on the viewing panel. Variances in the image are control by the arrangement and alignment of the crystals in the image display panel. As such, the components of the liquid crystal display are in need of relief from the constant heat generated by the illuminating light. The constant heat generation can accelerate thermal deterioration of the liquid crystal material from which the display is formed and shorten the useful lifespan of the liquid crystal display device. Heat may also negatively affect the refresh rate of the screen. 
         [0010]    Conventional display devices typically utilize a thick, heavy metal support member (often a thick aluminum sheet, or set of multiple sheets) to which is attached both the display panel unit, the light source (which, in the case of LEDs, may be mounted to printed circuit boards, such as a metal core printed circuit board (MCPCB) with a thermally conductive dielectric material) and associated electronic components. Heat passing from these heat sources contributes to uneven temperature distributions created on the panel unit itself, which adversely affects the image presented on the display panels as well as display panel reliability. 
         [0011]    The conventional support member provides both a mechanical function (i.e., for mounting the panel unit and associated electronics), as well as a thermal function (i.e., to help sink and spread heat generated by the light source(s) and/or the associated electronics). Accordingly, the support member is typically fabricated from a solid sheet of aluminum, on the order of about 2.0 mm thick. It will be recognized that, since most metals are relatively thermally isotropic, the in-plane thermal conductivity is not substantially different from the through-plane thermal conductivity of the material. 
         [0012]    LCD device manufacturers are under extreme pressure to reduce the cost and weight of their existing display solutions, while there has simultaneously been a desire to increase the brightness and luminous efficiency of the panel units. This can mean more power being sent to the light sources, which increases the thermal load on the system and requires additional heat dissipation capabilities within the display units. In addition to increasing brightness and luminous efficiency of the displays, display manufacturers are also under increasing pressure to produce larger panel sires, which tends to increase the weight of the frame system (especially the support member) proportionately. 
         [0013]    Thus, what is desired is a light weight and cost effective system fur display devices which provides enhanced heat transfer capabilities fur the light source circuits. 
       SUMMARY 
       [0014]    A light emitting diode (LED) light arrangement is provided. The light arrangement includes a flexible circuit board including a flexible graphite substrate having a first major surface and a second major surface, a dielectric layer disposed on at least one of the first and second major surfaces, and an electrically conductive layer arranged to form an electrical circuit disposed on the dielectric layer, and an LED mounted to the flexible graphite substrate and in electrically conductive contact with the electrically conductive layer thereby forming a component of the electrical circuit. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description provide embodiments of the invention and are intended to provide an overview or structure of understanding of the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification. The drawings illustrate various embodiments of the invention and together with the description serve to describe the principles and operations of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE: DRAWINGS 
         [0016]      FIG. 1  is a side view of a flexible circuit board as described herein; 
           [0017]      FIG. 2  is a side view of the flexible circuit hoard of  FIG. 1  shown in a curved configuration; 
           [0018]      FIG. 3  is a side view of another example of a flexible circuit hoard as described herein; 
           [0019]      FIG. 4  is a side view of another example of a flexible circuit hoard as described herein; 
           [0020]      FIG. 5  side view of another example of a flexible circuit board in accordance with invention; 
           [0021]      FIG. 6  is a side view of another example of a flexible circuit board as described herein; 
           [0022]      FIG. 7  is a perspective view of the circuit board of  FIG. 5  having a rigid frame; 
           [0023]      FIG. 8  is a perspective view of the circuit board of  FIG. 7  forming a light engine in a display device; 
           [0024]      FIG. 9  is a perspective view of the circuit board of  FIG. 1  having a rigid frame and forming a light engine in a display device; 
           [0025]      FIG. 10  is a plan view of the circuit board of  FIG. 1  having to rigid frame and forming a light engine in a display device; 
           [0026]      FIG. 11  is a perspective view of circuit board of FIG  1  having a rigid frame and forming a light assembly for an LED light; and 
           [0027]      FIG. 12  is a sectional view of an electronic circuit arrangement forming an LED down light. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0028]    With reference now to  FIGS. 1 and 2 , an embodiment of a circuit board in accordance with the present invention is shown and generally designated by the reference numeral  102 . It should be noted that for the sake of clarity not all the components and elements of the circuit board  102  may be shown and/or marked in all the drawings. Also, as used in this description, the terms “up,” “down,” “top,” “bottom,” etc. refer to device  110  when in the orientation shown in  FIG. 1 . However, the skilled artisan will understand that device  102  can adopt any particular orientation when in use. 
         [0029]    As shown in  FIG. 1 , circuit board  102  includes a substrate  103  formed of a one or more graphite sheets  105 , as shall be described in further detail below. The circuit board substrate  103  is formed of graphite, in the form of one or more sheets of compressed particles of expanded graphite, such as for example exfoliated graphite, and/or one or more sheets of graphitized polymer synthetic graphite, both of which are referred to herein as flexible graphite  105 . Thus, in at least one example the flexible graphite  105  includes one or more sheets of compressed particles of expanded graphite. In another example the flexible graphite  105  includes one or more sheets of graphitized polymer synthetic graphite. In another example, the flexible graphite includes one or more sheets of compressed particles of expanded graphite and one or more sheets of graphitized polymer synthetic graphite. In another example at least one flexible graphite sheet  105  includes both compressed particles of expanded graphite and graphitized polymer synthetic graphite. 
         [0030]    In at least one example, the flexible graphite sheet has a thickness ranging from about 0.001 mm to about 1.0 mm. In another example, the flexible graphite sheet has a thickness ranging from about 0.025 mm to about 0.5 mm. In another example the flexible graphite sheet has a thickness ranging from about 0.120 mm to about 0.250 mm. 
         [0031]    In at least one example, the flexible graphite sheet  105  is substantially resin-free, wherein resin-free is defined as being below conventional detection limits. In other examples, the flexible graphite sheet  105  has less than 1% by weight resin. 
         [0032]    In at least at least one example, the flexible graphite sheet  105  is not epoxy impregnated. 
         [0033]    The flexible graphite sheet  105  can have a relatively small amount of binder, or no binder. In at least one example, the flexible graphite  1 . 05  sheet can have less than 10% by weight of binder. In another example the flexible graphite sheet  105  can have less than 5% by weight of binder. In at least one, the flexible graphite sheet  105  can substantially binder-free, wherein hinder-free is defined as being below conventional detection limits. 
         [0034]    The flexible graphite substrate  103  can be one or more sheets synthetic graphite  105 . The synthetic graphite can be formed of a polymer film selected from polyphenyleneoxadiazoles (POD), polybenzothiazole (PBT), polybenzobisthiazole (PBBT), polybenzooxazole (PBO), polybenzobisoxazole (PBBO), poly(pyromellitimide) (PI), poly(phenyleneisophthalamide) (PPA), poly(phenylenebezoimidazole)(PBI), poly(phenylenebenzobisimidazole) (PPBI), polythiazole (PT), and poly(para-phenylenevinylene) (PPV). The polyphenyleneoxadiazoles include poly-phenylene-1,3,4-oxadiazole and isomers thereof. These polymers are capable of conversion into graphite of good quality when thermally treated in an appropriate manner. Although the polymer for the starting film is stated as selected from POD, PBT, PBBT, PBO, PBBO, PI, PPA, PBI, PPBI, PT and PPV, other polymers which can yield graphite of good quality by thermal treatment may also he used. 
         [0035]    As noted above, the thusly-formed sheets  105  of compressed particles of exfoliated graphite arid/or synthetic graphite forming the substrate  103  are anisotropic in nature; that is, the thermal conductivity of the sheets is greater in the in-plane, or “a” directions, as opposed to the through-sheet, or “c” direction. In this way, the anisotropic nature of the graphite sheet directs the heat along the planar direction of the thermal solution (i.e., in the “a” direction along the graphite sheet). Such a sheet generally has a thermal conductivity in the in-plane direction of at least about 140, more preferably at least about 200, and most preferably at least about 250 W/m°K and in the through-plane direction of no greater than about 12, more preferably no greater than about 10, and most preferably no greater than about 6 W/m° K. Thus, the heat dispersion material forming the substrate  103  has a thermal anisotropic ratio (that is, the ratio of in-plane thermal conductivity to through-plane thermal conductivity) of no less than about 10. 
         [0036]    The flexible graphite sheet  105  has flexibility characteristics as determined by its bend radius. The bend radius can be measured by wrapping the sheet  105   360 * around a cylindrical mandrel of a predetermined radius. The flexible graphite sheet  105  achieves the bend radius without negatively affecting the structural integrity of the sheet or effecting the function of the electrical circuit. In this respect, “bend radius” as used herein, can also be referred to as the “useful bend radius”. The bend radius is smaller than or equal to a threshold bend radius. The bend radius of the sheet  105  can be equal or smaller than the bend radius (described below) achievable by the entire flexible circuit  102  which is formed of the flexible graphite sheet. 
         [0037]    The flexible graphite sheet  105  has a bend radius of less than about 600 mm, more preferably less than about 150 mm, more preferably less than about 75 mm, more preferably less than about 25 mm, more preferably less than about 18 mm, and more preferably less than about 12 mm, and more preferably less than about 8 mm. In at least one example, 0.5 mm thick sheet  105  has a bend radius of about 6.0 mm. In at least one other example, 0.25 mm thick sheet  105  has a bend radius of about 3.0 mm. 
         [0038]    The substrate  103  of the circuit hoard  102  shown in  FIGS. 1 and 2  is formed of a single sheet of flexible graphite  105 , though it should be appreciated that the substrate can be formed of a plurality of flexible graphite sheets as discussed in further detail below. In at least example, the substrate  103  has a thickness ranging from about 0.001 mm to about 1.0 mm. In another example, the substrate  103  has a thickness ranging from about 0.025 mm to about 0.5 mm. In another example the substrate  103  has a thickness ranging from about 0.120 mm to about 0.250 mm. 
         [0039]    The substrate  130  has flexibility characteristics that are at least as flexible as the flexible circuit board  102 , as described below, that is to say, it has a bend radius that is equal to or smaller than the flexible circuit board enabling the substrate to be bent or otherwise distorted from a planar configuration in a manner while maintaining its properties suitable for use as a circuit board as described herein. 
         [0040]    Referring again to  FIGS. 1 and 2 , the circuit hoard substrate  103  has oppositely disposed major surfaces  104   a ,  104   b . A dielectric layer  106  is disposed on at least one of the surfaces  104   a ,  104   b . In at least one example, the dielectric layer  106  is disposed directly on the at least one of the surfaces  104   a ,  104   b . In another example, one or more thin coatings or films can be applied directly on the at least one of the surfaces  104   a ,  104   b  and the dielectric layer  106  is disposed directly the one or more thin coatings. Examples of these thin coatings or films can include a thin conductive foil or sputtered coating, such as for example a sputtered conductive coating. It is desirable that any such coaling or film disposed directly on the surface of the substrate would not provide a significant thermal barrier and thus would not adversely affect the heat transfer from the dielectric layer  106  (and/or any thermally conductive conduit  116  discussed below) to the substrate  103 . Thickness ranges can include 1.0 μm micron to 250 μm, and in other examples the thickness can he about 10 μm to about 100 μm, and still in other examples the thickness can be about 25 μm to about 50 μm. Multiple layers of conductive and insulated inks can be applied to create multiples of single thicknesses, as determined by the desired electrical requirements. 
         [0041]    The dielectric layer  106  can be formed of a thick film paste, 
         [0042]    An example of a suitable dielectric layer formed of a thick film paste has a preferable breakdown voltage of about 1000 VDC/mil, ranging from about 500 VDC/mil to about 1500 VDC/mil, with other examples ranging from about 800 VDC/mil to about 1200 VDC/mil, with other examples ranging from about 900 VDC/mil to about 1100 VDC/mil, 
         [0043]    The thick film dielectric layer  106  can have a thickness which can range from about 5 μm to about 100 μm. In another example, the dielectric thickness can range from about 5 μm to 50 μm, in another example, the dielectric thickness can range from about 5 μm to 20 μm and in another example, the dielectric thickness can range from about 15 to 20 μm. 
         [0044]    In at least one example, the dielectric layer  106  can he a polyimide, 
         [0045]    The dielectric layer  106  is flexible, and capable of being bent or otherwise distorted from a planar configuration as described in further detail below, as shown in  FIG. 2 , while maintaining dielectric properties suitable for use in a circuit board. The dielectric layer  106  can be as flexible as the flexible graphite substrate  103  while maintaining dielectric properties suitable for use in a circuit board. 
         [0046]    Dielectric layers used in the printed circuit, board industry for conventional less flexible and/or rigid printed circuit boards are unsuitable for use in the flexible circuit board  102  described herein. Thus, the dielectric layer  106  is not a glass fiber formed as a laminate, polytetrafluoroethylene (PTFE), commercially available as Teflon brand materials, and expanded PTFE, sometimes denoted ePTFE, commercially available as Gore-Tex brand materials, as well as resin—impregnated or—imbibed versions of the foregoing. 
         [0047]    An electrically conductive layer  108  is applied onto the dielectric layer  106  such that the dielectric layer is disposed between the electrically conductive layer  108  and the graphite sheet substrate  103 . In at least one example, the electrically conductive layer  108  can be formed directly on the surface of the dielectric layer  106 . The electrically conductive layer  108  is configured to form an electrical circuit  109 . 
         [0048]    The electrically conductive, layer  108  can include at least one of silver, copper, aluminum. In another example, the electrically conductive layer  108  can include a conductor paste, such as for example copper conductor paste, silver conductor paste or aluminum conductor paste. The conductor paste can be as thick Film conductor paste commercially available from Heraeus Materials Technology LLC. In another example, the electrically conductive layer  108  can include a metal foil. 
         [0049]    The thick film electrically conductive layer  108  can have a thickness which can range from about 5 to about 100 μm. In another example, the electrically conductive layer thickness can range from about 5 to 50 μm, in another example, the electrically conductive layer thickness can range from about 5 to 20 μm and in another example, the electrically conductive layer thickness can range from about 15 to 20 μm. 
         [0050]    The electrically conductive layer  108  can he flexible, capable of being bent or otherwise distorted from a planar configuration as described in further detail below, as shown in  FIG. 2 , while maintaining electrically conductive properties suitable for functioning, as an electrical circuit on a circuit board  102 . The electrically conductive layer  108  can be as flexible as the flexible graphite substrate  103 , while maintaining electrically conductive properties suitable for functioning as an electrical circuit on a circuit board  102 . 
         [0051]    The electrically conductive layer  108  can be applied to the dielectric layer  106  using suitable printing, techniques, such as for example screen printing or 3D printing. 
         [0052]    In at least one example, the flexible circuit board  102  has a thickness ranging from about 1.0 μm to about 1.1 mm, and more preferably from about 0.100 mm to about 0.800 mm, and more preferably from about 0.200 mm to about 0.650 mm. 
         [0053]    Thus formed as described above, the flexible circuit board  102  including, the flexible graphite substrate  103 , dielectric layer(s)  106  and conductive layer(s)  108  has similar flexural characteristics as the flexible graphite sheet  105   
         [0054]    The flexible circuit board  102  has flexibility characteristics which enable it to be bent, flexed or otherwise distorted from a planar configuration without negatively affecting its performance as a circuit hoard, thereby maintaining suitable integrity of the board and suitable electrical performance of the circuit  109 . 
         [0055]    The flexible circuit board  102  has flexibility characteristics as determined by its bend radius. The bend radius can be measured by wrapping the hoard  102  360° around a cylindrical mandrel of a predetermined radius, as described above. The flexible circuit board  102  achieves the bend radius without negatively affecting the structural integrity of the substrate  103  or effecting the function of the electrical circuit. 
         [0056]    The flexible circuit board  102  has a bend radius of less than about 600 mm, more preferably less than about 150 mm, more preferably less than about 75 mm, more preferably less than about 25 mm, more preferably less than about 18 mm, and more preferably less than about 12 mm, and more preferably less than about 8 mm. In at least one non-limiting example, 0.5 mm thick circuit board  102  has a bend radius of about 6.0 mm. In at least one other non-limiting example, a 0.25 mm thick circuit board  102  has a bend radius of about 3.0 mm. In one other non-limiting example the flexible circuit hoard  102  has a thickness of about 0.300 mm, and a bend radius of 2 cm. In another non-limiting example, the flexible circuit board  102  has a thickness of about 0.650 mm and a bend radius of about 5 cm. 
         [0057]    One or more electrical or electronic components  110  are attached to the electrically conductive layer  108  of the circuit board  102  to form an electronic circuit. The electronic component  110  can include one or more electrically conductive feet  112 , which are bonded to the electrically conductive layer  108  in a manner which forms an electrically conductive path therebetween. 
         [0058]    in at least one example, the screen printed electrically conductive, layer thick film  108  is arranged in a predetermined electrical circuit  109 . The one or more electrical components  110  are then mounted to the flexible graphite substrate  103  of the circuit board  102  by placing them in physical contact with the electrically conductive layer  108  and the electrically conductive layer is cured to bond the one or more electrical components in electrically conductive contact to the electrically conductive layer thereby firming an forming components of the electrical circuit. The curing process cart include heating the circuit board  102  in a heat cycle. 
         [0059]    In another example, one or more of the electrical components  110  can be soldered to the electrically conductive layer  108 . 
         [0060]    The electronic component  110  can comprise any electronic device or electrical device that produces an amount of heat that is desired to be dissipated away from component  110 . In one non-limiting example, the heat generated from component  1101  is dissipated to prevent it from interfering with the operation of the electronic component or the system of which the electronic component is an element. The electronic component  110  can be a surface mount component, or a wire bond component suitable for mounting to the circuit hoard  102 . Other examples of the electronic component  110  can include, a microprocessor or computer chip, an integrated circuit, a hybrid integrated circuit, a power transistor including but not limited to a power transistor, a resistor, control electronics such as for example for an optical device like a laser, a field-effect transistor (FET), a printed circuit board (PCB) circuit, or components thereof, or other electronic/electrical element. In at least one example, the electronic component  110  can be one or more LEDs, OLEDs, or combinations thereof. 
         [0061]    The graphite substrate  103  of the flexible circuit board  102  provides effective cooling of the LEDs. It has been found that compared to an aluminum light engine arrangement of similar thickness and construction, a flexible graphite substrate used as an LED circuit board has demonstrated a 9.8° C. junction temperature reduction of an LED at 4W of electrical power. 
         [0062]    The electronic component  110  becomes a heat source during operation. It includes at least one surface from which heat radiates and this surface can be used as a source of heat to be dissipated from the electronic component. The flexible graphite substrate.  103  facilitates this dissipation of heat. An optional thermally conductive conduit  116  can he disposed in physical and thermal contact with the surface of the electronic component  110  and with the graphite substrate  103  to conduct heat away from the electronic component  110  and towards/into the graphite substrate where it is then moved away from the component. 
         [0063]    Examples of the thermally conductive conduit  116  can include a material similar to the material used in the conductive layer, such as for example thick film conductive paste including, but not limited to a silver paste. The thermally conductive conduit  116  also include a thermal grease or other thermally conductive materials. In another example, the thermally conductive conduit  116  can also he one or more layers of flexible exfoliated graphite. In another example, the dielectric can be used as the thermally conductive conduit  116 . 
         [0064]    As shown in  FIG. 3 , another example of a flexible circuit board is shown generally at  302 . The flexible circuit hoard  302  includes a substrate  103  formed of a plurality of flexible graphite sheets  105  disposed in a stratified, laminated arrangement. In at least one example, the plurality of sheets of flexible graphite  105  arc laminated together in direct contact with each other. In another example, the laminated arrangement, of graphite sheets  105  forming the substrate  103  has a layer of a different material interposed between at least two of the graphite sheets, such as for example an adhesive. Though the example shown includes three sheets of flexible graphite  105  it should be appreciated that the plurality of graphite sheets can include any suitable number of graphite sheets laminated together. 
         [0065]    A dielectric layer  106  is applied to the substrate surface  104   a . In this example the dielectric layer  106  includes a plurality of dielectric layers  106   a ,  106   b  disposed on top of each other. Though 2 layers  106   a ,  106   b  are shown, it should be appreciated that the dielectric layer can include any suitable number of layers disposed on top of and in contact with each other. 
         [0066]    An electrically conductive layer  108  is applied onto the dielectric layer  106  such that the dielectric layer is disposed between the electrically conductive layer  108  and the graphite sheet substrate  103 . The electrically conductive layer  108  can be formed directly on the surface of the dielectric layer  106 . In this example, the electrically conductive layer  108  includes a plurality of electrically conductive layer  108   a ,  108   b  disposed on top of each other. Though 2 layers  108   a ,  108   b  are shown, it should be appreciated that the electrically conductive layer  108  can include any suitable number of layers disposed on top of and in contact with each other. 
         [0067]    A surface of the body of the electronic component  310  is disposed in physical and thermal contact with the graphite substrate  103  to conduct heat away from the electronic component  310  and towards/into the graphite substrate  103  obviating the use of the thermally conductive conduit  116 . 
         [0068]    Referring now to  FIG. 4 , another example of a flexible circuit board is shown generally at  402 . A surface mount electronic component  410  is attached to the flexible circuit board by bonding one or more electrically conductive mounting pads  412  to the electrically conductive layer  108 . A plurality of separate circuit traces, each including a dielectric layer  106  and conductive layer, can he connected to the component  410  in this manner. A thermally conductive conduit  116  is shown in physical and thermal contact with both the electrical component  410  and flexible substrate  103  for conducting heat from the component to the substrate as described above. 
         [0069]    Referring now to  FIG. 5 , another embodiment of the flexible circuit board is shown generally at  502 . The flexible circuit board  502  includes a continuous flexible graphite sheet  105  forming the substrate  103 . The substrate  103  includes component section  520 , a heat dissipation section  522  and a curved portion  524  disposed between the component section and the heat dissipation section. 
         [0070]    A dielectric layer  106  and electrically conductive layer  108  are formed on the component section  520  in a manner as described above. One or more electrical or electronic components  510  are attached electrically conductive layer  108  on the component section  520  to form an electronic circuit. In at least one example, the dielectric layer  106  and electrically conductive layer  108  are not formed on the heat dissipation section  577  or the curved portion  524 . 
         [0071]    The flexible characteristics of the circuit board substrate  103  enable the heat dissipation section  522  to extend along a different orientation than the component section. In the example provided, the component section  520  and the heat dissipation section  522  each generally planer, extending alone different planes which are approximately perpendicular to each other. However, it should be appreciated that other orientations are contemplated, such as for example one or both of the component section  520  and the heat dissipation section  522  can be curved or otherwise non-planer and/or the sections can extend at different angles relative to each other. 
         [0072]    The heat dissipation section  522  can have a similar sized area as the component section  520 . In other examples the heat dissipation section  522  can define an area that is smaller than the heat dissipation section. In still other examples, heat dissipation section  522  can define an area that larger than the component section  520 , such as about twice the area of the component section, or 3 time the area of the component section, or more than 3 times larger than the area of the component section. The heat dissipation section  522  provides effective removal of heat from the substrate  103  when exposed to moving air, such as in the maimer described in further detail below. 
         [0073]    Referring now to  FIG. 6 , another embodiment of the flexible circuit board is shown generally at  602  which is similar to the flexible circuit board  502  describe above. The flexible circuit board  602  includes a substrate  103  formed of a plurality of flexible graphite sheets  105  in a manner as described above. 
         [0074]    Referring now to  FIGS. 7 and 8  an electronic circuit arrangement, also referred to as an LED light engine, for a display device is shown generally at  700 . The LED light engine  700  includes the flexible circuit hoard  502  described above. A plurality of light emitting electrical components  710  are bonded to the electrically conductive layer  108  disposed on the dielectric layer  106  of the component section  520  in a similar manner as at least one of the electrical components  110 ,  310 ,  410 ,  510  described above. 
         [0075]    The electrical components  710  are LEDs operatively coupled to an LCD display panel  882  of an image display device  880  as shown generally in  FIG. 8 . The LCD display panel  882  can he a back-lit LCD panel or a side-lit LCD panel. The example of  FIGS. 7 and 8 , use side lit LCD display panel  882 , wherein the LCD light sources  710  extend in a linear array along the sides, top and bottom edges of the LCD panel so as to emit light towards the edges of the display panel. 
         [0076]    Optics, sometimes referred to as light guides, can be employed to even out the light distribution across the rear of the LCD panel so the light does not appear to be originating from or more pronounced at the edges or sides of the panel. In a back-lit LCD panel, rows of the LED light sources  710  can be mounted on a flexible circuit board  110  such that the LEDs sit directly behind the LCD panel to provide direct lighting to the rear of the LCD panel. In addition, whether back-lit or side-lit, LCDs can have a reflective material disposed so as to thither facilitate even light distribution from the light sources to the rear of the LCD panel. 
         [0077]    A frame  730  is provided for supporting the flexible circuit board  502 . The frame  730  is formed of a plastic, or other rigid material to support the flexible circuit board  502 , at a desired orientation. As shown in  FIG. 8 , the circuit hoard  502  can he oriented such that the array of LEDs  710  extend vertically to illuminate the vertical edges of the LCD display  882 . The circuit hoard  502  can also he oriented such that the array of LEDs  710  extend horizontally to illuminate the top and bottom edges of the LCD display. 
         [0078]    The frame  730  includes a first portion  732  supporting, the heat dissipation section  522  and a second portion  734  supporting the component section  520 . The first portion  732  forms an angle with respect to the second portion  734  of approximately 90 degree though it should he appreciated that other orientations are contemplated. 
         [0079]    The first portion  732  includes a vertically extending support member  736  having a support surface  738 . The first portion  732  also includes a vertically extending channel  740  disposed adjacent the support member  736 . The flexible circuit board  530  is disposed against the support surface  738  such that the support surface supports the flexible circuit hoard heat dissipation section  522  in a spaced apart relationship with the channel  740  to form an air duct  742  between the channel and the flexible circuit hoard heat dissipation section. The air duct  742  includes an inlet  744  for receiving relatively cooler air A C  and an outlet  746  for exhausting relatively warmer air A W  thereby directing air past the heat dissipation section  5 . 22  to provide convective cooling of the circuit hoard  502 . The air duct  742  extends generally vertically from the inlet.  744  to the outlet  746  to enhance the flow of convective air currents. 
         [0080]    The frame  730  can include a plurality of spaced apart support members  736  each having a respective support surface  736  for supporting the circuit hoard  502  in a spaced apart relationship to one or more channels  740  to form one or more air ducts  742  for moving cooling air past the graphite substrate  103  for cooling, the circuit board in this manner. 
         [0081]    The flexible circuit board  502  can be secured to the frame  730  using one or more damp members  760 . In the examples provided in  FIG. 8 , one clamp member  760  is shown in a vertical orientation and two damp members are shown in a horizontal orientation, though it should be appreciated that more than two can be used. The heat dissipation section  522  is held against the one or more support surfaces  738  using a clamp member  760 . The clamp member can extend vertically along the vertically extending support members  736 , horizontally in a perpendicular orientation with respect to the support members, or in other suitable orientations. The clamp member  760  is pressed against the surface  104   a  of the heat dissipation section biasing the opposite surface  104   b  of the heat dissipation section against the support surface  738 . The clamp member  760  can be fastened to the frame  730  using mechanical fasteners such as screws, bolts, rivets, clips, and the like, as known in the art, or adhesives, or using other frame members. Additionally or alternatively, the flexible circuit board  502  can be secured to the frame  730  using fasteners, or adhesives disposed between the frame and the circuit board. 
         [0082]    Referring now to  FIGS. 9 and 10  an electronic circuit arrangement forming an LED light arrangement, also referred to as an LED light engine, for a display device  980  is shown generally at  900 . The LED light engine  900  includes a flexible circuit board  902  similar to the flexible circuit board  102  described above. A plurality of light emitting electrical components  910  are bonded to the electrically conductive layer  108  disposed on the dielectric layer  106  in a similar manner as at least one of the electrical components  110 ,  310 ,  410 ,  510  described above. 
         [0083]    The electrical components  910  are LEDs operatively coupled to an LCD display panel  982  of an image display device  980  as shown generally in  FIG. 9 . The LCD display panel  982  can be a back-lit LCD panel or a side-lit LCD panel. The example of  FIGS. 9 and 10 , includes a back-lit LCD display panel  982 , wherein the LED light sources  910  are disposed so as to extend in a plurality of linear arrays or rows (only one of which is shown for clarity) so as to emit light towards the back side of the display panel, opposite the viewing, side. However, it should he appreciated that the LED light sources  910  can be disposed so as to extend in a linear array along the sides, top and bottom edges of an edge-lit LCD panel  982  so as to emit light towards the edges of the display panel. 
         [0084]    A frame  930  is provided for supporting the flexible circuit board  902 . The frame  930  is formed of a plastic, or other rigid material to support the flexible circuit hoard  902  at a desired orientation. The frame  930  includes a support member  936  having a support surface  938 . In the example provided, the support surface  938  is generally planar. The flexible graphite substrate  903  is disposed against the support surface  938  such that the support member surface  938  supports the component section of the flexible circuit board in a generally planar configuration. The frame  930  can be mounted to the display device  980  such that the LED components  910  assume a vertical orientation in relation to the display while it is in use. In other examples, frame  930  can he mounted to the display device  980  such that the LED components  910  assume a horizontal orientation in relation to the display while it is in use. 
         [0085]    The support member  936  can include an optional aperture  939  disposed in the support surface  938 , such that the support surface supports the outer periphery of the flexible graphite substrate  103  and the aperture provides convective air cooling to a surface of the flexible graphite substrate. 
         [0086]    The flexible circuit hoard  902  can be secured to the frame  930  using fasteners and/or adhesives. Alternatively or additionally, the flexible circuit board  902  can be secured to the frame  930  using one or more clamp members  960 . In the examples provided in  FIG. 9 , one clamp member  960  is shown, though it should be appreciated that more than one can be used. The clamp member  960  can he a FR4 circuit board biasing the flexible circuit hoard  902  against the support surface  938 . In at least one example the FR4 hoard is not electrically connected to the flexible circuit board  902 . In another example, the FR4 circuit board includes an electrically conductive layer  962  providing an electrical connection between LEDs  910 . In this example, the FR4 hoard includes electrically conductive pads  964  that mate with and are electrically connected to the electrically conductive layer  108 . In this manner, a power supply  966  can provide power to FR4 board and power the LEDs during operation as shown. 
         [0087]    Referring now to  FIG. 11 , an electronic circuit arrangement forming an LED light arrangement is shown generally at  1100 . The light arrangement  1100  includes a flexible circuit board  102  similar to the flexible circuit board  102  described above. A plurality of light emitting electrical components  1110  are bonded to the electrically conductive layer  108  disposed on the dielectric layer  106  in a similar manner as at least one of the electrical components  110 .  310 ,  4   10 ,  510 ,  710 ,  910  described above. The plurality of light emitting electrical components  1110  can be LEDs. 
         [0088]    The flexible graphite substrate  103  defines a cylinder such that the first major surface  104   a  is a radially outer surface of the cylinder and the dielectric layer  106  is disposed on the radially outer surface, wherein the plurality of LEDs  1110  are mounted at the radially outer surface so as to be in contact with the electrically conductive layer  108 . The electrically conductive layer  108  can form a circuit trace  111  forming at least part of the electrical circuit  109  having a length L extending substantially longer than its width W, examples of which can include equal length L equal to about 4*W, L equal to about 8*W, and L greater than about 10*W. The circuit trace  111  can extend axially and/for circumferentially along the cylindrical surface  104   a  of the flexible graphite substrate  103  to form the circuit  109 . In other examples, the circuit trace  111  can extend in other directions in addition to axially and/or circumferentially to form the circuit  109 . 
         [0089]    A rigid frame  1130  supports the flexible circuit board in this configuration. The rigid frame  1130  includes a central portion  1131  extending in a longitudinal direction along the axis of the cylinder. The frame  1130  includes a plurality of support members  1136  extending radially from central portion  1131 , each terminating in a radially outwardly facing support surface  1138 . The support surfaces  1138  are in supportive physical contact with the second major surface  104   b  of the flexible graphite substrate  103 . The frame  1130  includes a plurality of channels  1140 , each channel being disposed between pairs of adjacent support members  1136 . 
         [0090]    The cylindrically shaped flexible circuit board  1130  is disposed against the support surfaces  1138  such that the support surfaces support the flexible circuit board in a spaced apart relationship with the channels  1140  to form air ducts  1142  between the channel and the flexible circuit board. The air ducts  1142  include an inlet  1144  for receiving relatively cooler air A C  and an outlet  1146  for exhausting relatively wanner air A W  thereby directing air past the portion of the circuit board to which the LEDs  1110  are mounted to provide convective cooling of the circuit hoard  1102 . The rigid frame  1130  can be mounted such that the air duct  1142  extends generally vertically from the inlet  1144  to the outlet  1146  to enhance the flow of convective air currents. 
         [0091]    Referring now to  FIG. 12 , an further embodiment of an electronic circuit arrangement forming an LED downlight is shown generally at  1200 . The down light  1200  includes a housing  1207  enclosing as flexible circuit board  1202  similar to the flexible circuit board  102  described above. A plurality of light emitting electrical components  1210  are bonded to the electrically conductive layer  108  disposed on the dielectric layer  106  arranged on a first major surface  1202   a  of the flexible surface  1202  in a similar manner as at least one of the electrical components  110 ,  310 ,  410 ,  510 ,  710 ,  910  described above. The plurality of light emitting electrical components  1210  can be LEDs. 
         [0092]    The down light also includes a heat sink  1210  which can be formed of metal, such as aluminum or other metal material for dissipating the heat generated by light emitting electrical components  1210 . The heat sink  1210  can extend outside of the housing  1207  or alternatively be formed of (i.e. integral to), at least in part, of the housing if so desired. 
         [0093]    The downlight  1210  also includes a rigid structural  1209  plate. The structural plate  1209  can be formed of plastic, or other non-conductive materials having suitable rigidity for use as described herein. 
         [0094]    The flexible circuit board  1202  includes a second major surface  1202   b  disposed opposite the first major surface  1202   a  disposed adjacent a surface  1210   a  of the heat sink  1210 . The structural plate  1209  is pressed against the first major surface  1202   a  of the flexible circuit board  1202  and secured to the heat sink with a plurality of fasteners  1216 . In one non-limiting example, the fasteners are screws/bolts which extend through the structural plate  1209  and the flexible circuit hoard.  1202  and into the heat sink  1210  to secure the structural plate to the heat sink. The flexible circuit board  1202  is clamped between the structural plate  1209  and the heat sink  1210  and pressed against the heat sink surface  1202   a  so as to be in effective conductive thermal communication with the heat sink. The rigid structural plate  1209  applies a clamping to press the flexible circuit board  1202  against the heat sink  1210  thereby reducing the bond line thermal resistance between the metal heat sink  1210  and graphite substrate  103  of the flexible circuit board. In this manner, the heat generated by the light emitting electrical components  2110  is transferred by the flexible graphite circuit board  1202  to the heat sink  1210  for effective conductive and convective dissipation. 
         [0095]    This arrangement can eliminate the need for a thermal interface material between the circuit hoard  1202  and the heat sink  1210 . Alternatively, an optional thermal interface material  1218  can he disposed between the second major surface  1202   b  and the heat sink surface  1210   a  to further improve heat transfer. 
         [0096]    The structural plate  1209  can include reflector surfaces  1220  encircling the light emitting electrical components  1210  to enhance the illumination provided by the downlight  1200 . In at least one example, the reflective surfaces  1220  can he tapered apertures extending through the structural plate  1209  and located in alignment with the positions of the light emitting electrical components  1210  so as to receive and encircle them when the circuit board is disposed between the heat sink and the structural plate. In this manner, the reflective surfaces  1220  can eliminate the need for a white reflective coating, such as a PET coating or the like, or a printed silkscreen on the circuit board. 
         [0097]    All cited patents and publications referred to in this application are incorporated by reference in their entirety. 
         [0098]    The invention thus being described, it will clear that it may he varied in many ways. Modifications and alterations will occur to others upon reading and understanding the preceding specification. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof