Abstract:
A method of making a light-emitting diode (LED) bulb and an LED bulb comprising a base, a shell connected to the base forming an enclosed volume. A thermally conductive liquid is held within the enclosed volume. A laminate support structure connected to the base and a plurality of flange portions formed in the laminate support structure. A plurality of LEDs are attached to the plurality of flange portions and arranged in a radial array.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. 119(e) of prior U.S. Provisional Patent Application No. 61/569,191, filed Dec. 9, 2011, U.S. Provisional Patent Application No. 61/579,626, filed Dec. 22, 2011, U.S. Provisional Patent Application No. 61/585,226, filed Jan. 10, 2012, and U.S. Provisional Patent Application No. 61/682,163, filed Aug. 10, 2012, each of which is hereby incorporated by reference in the present disclosure in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates generally to light-emitting diode (LED) bulbs, and more specifically to using a laminate structure for mounting LEDS in a liquid-filled LED bulb. 
     2. Description of Related Art 
     Traditionally, lighting has been generated using fluorescent and incandescent light bulbs. While both types of light bulbs have been reliably used, each suffers from certain drawbacks. For instance, incandescent bulbs tend to be inefficient, using only 2-3% of their power to produce light, while the remaining 97-98% of their power is lost as heat. Fluorescent bulbs, while more efficient than incandescent bulbs, do not produce the same warm light as that generated by incandescent bulbs. Additionally, there are health and environmental concerns regarding the mercury contained in fluorescent bulbs. 
     Thus, an alternative light source is desired. One such alternative is a bulb utilizing an LED. An LED comprises a semiconductor junction that emits light due to an electrical current flowing through the junction. Compared to a traditional incandescent bulb, an LED bulb is capable of producing more light using the same amount of power. Additionally, the operational life of an LED bulb is orders of magnitude longer than that of an incandescent bulb, for example, 10,000-100,000 hours as opposed to 1,000-2,000 hours. 
     While there are many advantages to using an LED bulb rather than an incandescent or fluorescent bulb, LEDs have a number of drawbacks that have prevented them from being as widely adopted as incandescent and fluorescent replacements. One drawback is that an LED, being a semiconductor, generally cannot be allowed to get hotter than approximately 120° C. As an example, A-type LED bulbs have been limited to very low power (i.e., less than approximately 8 W), producing insufficient illumination for incandescent or fluorescent replacements. 
     One approach to alleviating the heat problem of LED bulbs is to use a thermally conductive liquid to cool the LEDS. To facilitate thermal dissipation, it may be advantageous to increase the thermal paths from the LED to the environment. 
    
    
     
       DESCRIPTION OF THE FIGURES 
         FIG. 1  depicts a cross-sectional view of a liquid-filled LED bulb with a laminate support structure and a hub with a short center protrusion. 
         FIG. 2  depicts a cross-sectional view of a liquid-filled LED bulb with a laminate support structure and a hub with a tall center protrusion. 
         FIG. 3A  depicts the top surface of a flat laminate support structure. 
         FIG. 3B  depicts the bottom surface of a flat laminate support structure. 
         FIGS. 4A and 4B  depict cross-sectional views of exemplary laminate support structures. 
         FIG. 5  depicts an exemplary method of making a liquid-filled LED bulb having a laminate support structure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the various embodiments. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims. 
     Various embodiments are described below relating to LED bulbs. As used herein, an “LED bulb” refers to any light-generating device (e.g., a lamp) in which at least one LED is used to generate light. Thus, as used herein, an “LED bulb” does not include a light-generating device in which a filament is used to generate the light, such as a conventional incandescent light bulb. It should be recognized that the LED bulb may have various shapes in addition to the bulb-like A-type shape of a conventional incandescent light bulb. For example, the bulb may have a tubular shape, a globe shape, or the like. The LED bulb of the present disclosure may further include any type of connector; for example, a screw-in base, a dual-prong connector, a standard two- or three-prong wall outlet plug, bayonet base, Edison Screw base, single-pin base, multiple-pin base, recessed base, flanged base, grooved base, side base, or the like. 
       FIGS. 1 and 2  depict a cross-sectional view of an exemplary LED bulb  100 . For convenience, all examples provided in the present disclosure describe and show LED bulb  100  being a standard A-type form factor bulb. However, as mentioned above, it should be appreciated that the present disclosure may be applied to LED bulbs having any shape, such as a tubular bulb, a globe-shaped bulb, or the like. 
     In some embodiments, LED bulb  100  may use 6 W or more of electrical power to produce light equivalent to a 40 W incandescent bulb. In some embodiments, LED bulb  100  may use 20 W or more to produce light equivalent to or greater than a 75 W incandescent bulb. Depending on the efficiency of the LED bulb  100 , between 4 W and 16 W of heat energy may be produced when the LED bulb  100  is illuminated. 
     LED bulb  100  includes a shell  122  and base  124 , which interact to form an enclosed volume  120  over one or more LEDs  102 . As shown in  FIGS. 1 and 2 , the base  124  includes an adaptor for connecting the bulb to a lighting fixture. In some cases, the shell  122  and base  124  have a form factor similar to an A-type shape of a conventional incandescent light bulb. 
     Shell  122  may be made from any transparent or translucent material such as plastic, glass, polycarbonate, or the like. Shell  122  may include dispersion material spread throughout the shell to disperse light generated by LEDs  102 . The dispersion material prevents LED bulb  100  from appearing to have one or more point sources of light. 
     A thermally conductive liquid fills the volume  120 . As used herein, the term “liquid” refers to a substance capable of flowing. Also, the substance used as the thermally conductive liquid is a liquid or at the liquid state within, at least, the operating, ambient-temperature range of the bulb. An exemplary temperature range includes temperatures between −40° C. to +40° C. The thermally conductive liquid may be mineral oil, silicone oil, glycols (PAGs), fluorocarbons, or other material capable of flowing. In the examples discussed below, 20 cSt viscosity polydimethylsiloxane (PDMS) liquid sold by Clearco is used as a thermally conductive liquid. It may be desirable to have the liquid chosen be a non-corrosive dielectric. Selecting such a liquid can reduce the likelihood that the liquid will cause electrical shorts and reduce damage done to the components of LED bulb  100 . 
     The thermally conductive liquid is able to transfer heat away from the LEDs  102  and components in thermal connection with the LEDs  102 . Typically, the thermally conductive liquid transfers the heat via conduction and convection to other, cooler components of the LED bulb  100 , including the shell  122  and base  124 . During typical operation, the temperature of the LEDs  102  is higher than that of the shell  122  and base  124 . In some cases, the temperature difference between the LEDs  102  and the shell  122  results in passive convective flow of the thermally conductive liquid. The temperature difference between the LEDs  102  and the base  124  may also contribute to the induction of passive convective flow of the thermally conductive liquid. In general, the more heat that can be dissipated into the thermally conductive liquid, the greater the temperature difference between the components resulting in more passive convective flow. 
     LED bulb  100  also includes a laminate support structure  150  for mounting the plurality of LEDs  102 . As shown in  FIGS. 1 and 2 , the laminate support structure  150  forms a cylindrical or conical shape and the plurality of LEDs  102  are mounted in a radial pattern within the shell  122 . The laminate support structure  150  is attached to the base  124  via a hub  126 / 128 . 
     In the present embodiment, a laser welded bond is used to attach the laminate support structure  150  to the hub  126 . The laser weld forms a structural bond between the laminate support structure  150  and the hub  126 . In the present embodiment, there is no threaded connection between the laminate support structure  150  and the hub  126 . In addition to forming a structural bond between the two pieces, the laser weld also forms a thermal bond between the laminate support structure  150  and the hub  126 . Thus, heat generated by the LED can be conducted through the laminate support structure  150  and dissipated to the hub  126  via the laser weld. Heat that is conducted to the hub  126  may also be conducted to base  124  and other components of the LED bulb  100 . In an alternative embodiment, the laminate support structure  150  may be laser welded directly to a base to form a structural and thermal bond between the two pieces. In other embodiments, Other types of connections can also be used to attach the laminate support structure to the hub or base, including adhesive bonding, mechanical fastening, clamping, and the like. 
       FIG. 1  depicts the laminate support structure  150  attached to hub  126  having a center protrusion  202  that is shorter than the laminate support structure  150 . The laminate support structure  150  is attached at the lower flange  204  of the hub  126 . The LED bulb  100  of  FIG. 1  with a center protrusion  202  that is shorter than the laminate support structure  150  allows for more thermally conductive liquid in the center of the enclosed volume  120 . This configuration may result in passive convective flow of the thermally conductive liquid in the center of the enclosed volume. The central passive convective flow may assist in thermal dissipation from the inward facing surfaces of the laminate support structure  150 . 
       FIG. 2  depicts the laminate support structure  150  attached to hub  128  having a center protrusion  212  that is approximately the same height as the laminate support structure  150 . It is not necessary that the center protrusion  212  be the same height as the laminate support structure  150 . The LED bulb  100  of  FIG. 2  with center protrusion  212  may allow for multiple attachment points between the laminate support structure  150  and the hub  128 . For example, the laminate support structure  150  in  FIG. 2  may be attached at a lower flange  210  of the hub  128  and at the upper edge of the center protrusion  212 . Having multiple attachment points may assist in thermal conduction between the laminate support structure  150  and the hub  128 . In  FIG. 2 , an amount of thermally conductive liquid is also disposed between the hub  128  and the inward facing surfaces of the laminate support structure  150 . Thus, the thermally conductive liquid can also assist in dissipating heat from the inward facing surfaces of the laminate support structure  150 . 
       FIGS. 3A and 3B  depict an exemplary laminate support structure  150  having flange portions  320  for mounting LEDs  102 . The flange portions  320  are separated by a small gap to allow for passive convective flow of the thermally conductive liquid when the laminate support structure  150  is installed in the LED bulb. The flange portions  320  are wider than the LED  102  to facilitate heat dissipation. The extra width facilitates heat dissipation in at least two ways. First, the extra width of the flange portion  320  provide an increased cross-sectional area of the flange portion for improved thermal conduction from the LED  102  to the base of the laminate support structure  150 . The extra width of the flange portion  320  also provides an increased external surface area increasing the contact area between the laminate support structure  150  and the thermally conductive liquid. The increased surface area improves heat transfer into the thermally conductive liquid. 
     In the present embodiment, the laminate support structure  150  is a laminate.  FIGS. 4A and 4B  depict cross-sectional view of exemplary laminate support structure  150  that is a laminate. As shown in  FIGS. 4A and 4B , the laminate support structure  150  includes, at least two layers, a flexible circuit layer  340  and a mechanical support layer  330 . As shown in  FIG. 4B , the laminate support structure  150  includes additional layers  350  and  360 . The additional layers  350  can be located between the flexible circuit layer  340  and mechanical support layer  330  or on either side of the flexible circuit layer  340  or mechanical support layer  330 . 
     The flexible circuit layer  340  includes mounting pads for mechanically and electrically attaching the LEDs  102 . (See, for example,  FIG. 3A  for LEDs attached to a flexible circuit layer  340 .) The flexible circuit layer  340  also includes conductive traces electrically connecting the LEDs  102  to each other. The conductive traces may terminate in one or more terminal connection points that can be used to attach leads from a power supply circuit. The flexible circuit layer  340  also includes one or more dielectric layers to electrically insulate and protect the conductive traces. 
     The mechanical support layer  330  of the laminate support structure  150  may be formed from a thermally conductive material, such as aluminum, copper, brass, magnesium, zinc, or the like. Since the mechanical support layer  330  is formed using a thermally conductive material, heat generated by LEDs  102  may be conductively transferred to other elements of the LED bulb  100 . For example, because the laminate support structure  150  is at least partially immersed in the thermally conductive liquid, the mechanical support layer  330  is able to dissipate heat to the thermally conductive liquid. The mechanical support layer  330  is also connected to the base  124  via the hub  126 / 128 . Depending on the type of connection between the components, the mechanical support layer  330  may conduct heat to the hub  126 / 128  and base  124 . 
       FIG. 5  depicts a flow chart of an exemplary process  500  for making a liquid-filled LED bulb with a laminate support structure. The operations of process  500  are not necessarily performed in the sequence depicted in  FIG. 5 . 
     In operation  502 , a plurality of flange portions are formed in a laminate support structure.  FIGS. 3 and 4  depict an exemplary flat laminate support structure  150 . The flange portions may be formed in the laminate support structure  150  using traditional metal plate machining techniques including laser cutting, milling, stamping, or the like. It may be advantageous to form the flange portions in the laminate support structure  150  when the laminate is flat. It is also possible to form the flange portions when the laminate support structure is formed in a cylindrical or conical shape. 
     In operation  504 , the plurality of LEDs are attached to the flange portion of the laminate support structure. To utilize traditional surface mount or electronic assembly techniques, it may be advantageous to attach the LEDs to the flange portions of the laminate support structure  150  when the laminate is flat.  FIG. 3  depicts laminate support structure  150  having a plurality of LEDs attached to the flexible circuit layer  340 . 
     In an optional operation  506 , the laminate support structure can be formed into a cylindrical or conical shape. This operation is not required if the laminate support structure is not flat and has already been formed into a cylindrical or conical shape. In some cases, the laminate support structure  150  is formed using a mandrel or round forming tool.  FIG. 4  depicts exemplary relief cuts  310  made into the mechanical support layer  330  of the laminate support structure  150 . The relief cuts  310  remove part of the material of the mechanical support layer  330  and allow the laminate support structure  150  to be formed into a cylindrical or conical shape while reducing stress and the possibility of cracking or other material failure. 
     It may be advantageous to form the laminate support structure into a cylindrical or conical shape after the flange portions have been formed and LED components attached. However, it is not necessary that the laminate support structure  150  be attached to the LEDs or completely machined before forming. For example, the base of the laminate support structure may be machined flat or turned true after being formed into a cylindrical shape. 
     In another optional operation  508 , the flange portions of the laminate support structure are bent to form a bent face. This operation is optional because some embodiments do not include a flange portion with a bent face. This operation is also not required if the flange portions have already been bent. Relief cuts  310  (shown in  FIG. 3B ) allow the flange portions  320  of the laminate support structure  150  to be bent inward toward the center of the laminate support structure  150  forming a bent face. The LEDs  102  can be mounted to the bent face so that the like emitted from the LEDs is angled slightly up. In some embodiments, the angle between the bent face and the central axis of the LED bulb (or laminate support structure  150 ) is at least 5 degrees. As shown in  FIGS. 1 and 2 , the laminate support structure  150  may include multiple bends to achieve the desired angle. 
     In operation  510 , the laminate support structure is connected to the base. As shown in  FIGS. 1 and 2 , the laminate support structure  150  may be connected to the base  124  using hub  126 / 128 . As previously mentioned, in some embodiments, the laminate support structure  150  may be laser welded to the hub  126 / 128 . In the present embodiment, the laser weld forms a structural and thermal bond between the laminate support structure  150  and the hub  126 / 128 . Typically, the laser weld is a continuous or near continuous bead around the perimeter of the laminate support structure. The bead typically has a cross sectional area that is sufficient to conduct the heat flux generated by the LEDs  102  when the bulb is in operation. There are no threaded fasteners or threaded connections between the laminate support structure  150  and the hub  126 / 128 . 
     In operation  512 , the shell is attached to the base to form an enclosed volume. As shown in  FIGS. 1 and 2 , the shell  122  may be attached to the base  124  forming enclosed volume  120 . In operation  514 , the LED bulb is at least partially filled with the thermally conductive liquid. On some embodiments, other portions of the LED bulb are at least partially filled with the thermally conductive liquid. 
     Although a feature may appear to be described in connection with a particular embodiment, one skilled in the art would recognize that various features of the described embodiments may be combined. Moreover, aspects described in connection with an embodiment may stand alone.