Patent Publication Number: US-2016230972-A1

Title: Light emitting module having wafer with integrated power supply device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/976,653, filed on Jul. 31, 2013, which is the National Stage entry of International Application No. PCT/KR2011/006173, filed on Aug. 22, 2011, and claims priority from Korean Application No. 10-2010-0137868, filed on Dec. 29, 2010, which are all hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a light emitting module having a light emitting diode chip, and more particularly, to a light emitting module configured by integrating a power supply device and one or more light emitting diode chips on one wafer. 
     2. Discussion of the Background 
     A light emitting diode is a representative semiconductor light emitting device that emits light through recombination of electrons and holes between n-type and p-type semiconductor layers when current is applied thereto. A light emitting diode has many advantages of continuous light emission using low voltage and low current, small electric power consumption, and the like, as compared with a conventional light source. 
     Generally, a light emitting diode package fabricated by mounting one or more light emitting diode chips to a package is frequently used. The light emitting diode package comprises a package body, which is mounted with lead frames corresponding to the light emitting diode chip. The lead frames and the light emitting diode chip are electrically connected by a wire(s), and thus, the light emitting diode chip that receives electric power applied from the outside can generate light. 
     Recently, there has been developed a light emitting module fabricated by mounting a light emitting diode chip on a wafer such as a silicon wafer, and the light emitting module is referred to as a ‘wafer-level package.’ 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     A conventional light emitting module has a disadvantage in that a light emitting diode chip on a wafer should operate depending on an external AC power source or a battery. Since the light emitting module always operates depending on conditions of the external power source, there is a limitation in using the light emitting module in a power failure or another emergency situation. 
     In a fabrication method of the conventional light emitting module, a plurality of light emitting diode chips are mounted on a front surface of a wafer, but the applicability of a rear surface of the wafer is considerably lowered. A via or electrode extending to the rear surface of the wafer is used as a terminal. Otherwise, the rear surface of the wafer is hardly utilized. 
     Meanwhile, a method of mounting light emitting diode chips on one large-sized wafer, performing wire connection and then cutting the wafer into a plurality of pieces is used as an example of a conventional fabrication method of a wafer-level package or light emitting module. It has been known that the method has a high productivity as compared with other conventional fabrication methods of a light emitting diode package. However, all components such as a power supply device and the like, which participate in the operation of a light emitting diode chip, are still separately assembled for each light emitting module. 
     Accordingly, an object of the present invention is to provide a light emitting module, in which light emitting diode chips are disposed on a first surface of a wafer, and a power supply device such as a capacitor or secondary battery is integrated on a second surface opposite to the first surface, thereby increasing the applicability of the surfaces of the wafer. 
     Another object of the present invention is to provide a light emitting module, in which light emitting diode chips are disposed on a first surface of a wafer, a power supply device such as a capacitor or secondary battery is integrated on a second surface opposite to the first surface, and a photoelectric conversion device for converting sunlight into electricity is additionally provided, so that the photoelectric conversion device and the power supply device allow the light emitting module not to use external power or to use only minimum external power. 
     A light emitting module according to an aspect of the present invention comprises a wafer having first and second surfaces; a light emitting diode chip disposed on the first surface of the wafer; a power supply device for supplying power to the light emitting diode chip; and a photoelectric conversion device for converting sunlight into electricity and providing it to the power supply device, wherein the power supply device is disposed on the second surface of the wafer. Preferably, the first and second surfaces are opposite to each other. 
     In detailed descriptions and claims, the first surface of the wafer means a surface on which one or more light emitting diode chips are mounted, and the second surface of the wafer means any surface different from the first surface. 
     According to one embodiment, the power supply device may be a capacitor, secondary battery, or fuel cell. The power supply device may comprise an anode layer, a cathode layer and a solid electrolyte interposed between these layers. In such a case, insulation films may be formed on one surface of the power supply device, which is in contact with the wafer, and an opposite surface of the power supply device, respectively. 
     According to one embodiment, the light emitting module may further comprise a lens or light guide for condensing sunlight to the photoelectric conversion device. 
     According to one embodiment, the photoelectric conversion device may be mounted to be in contact with the first or second surface of the wafer. 
     A light emitting module according to another aspect of the present invention comprises a wafer having first and second surfaces; a plurality of light emitting diode chips disposed on the first surface of the wafer; and a power supply device for supplying power to the plurality of light emitting diode chips, wherein the power supply device is disposed on the second surface of the wafer. 
     According to one embodiment, the power supply device may be a capacitor, secondary battery, or fuel cell. Furthermore, the power supply device may comprise an anode layer, a cathode layer and a solid electrolyte interposed between these layers. Insulation films may be formed on one surface of the power supply device, which is in contact with the wafer, and an opposite surface of the power supply device, respectively. 
     According to one embodiment, the light emitting module may further comprise a photoelectric conversion device for converting sunlight into electricity and providing it to the power supply device. 
     There are provided a plurality of the photoelectric conversion devices, wherein the plurality of photoelectric conversion devices may be disposed to surround a periphery of the power supply device or to surround a periphery of the light emitting diode chips. 
     Preferably, the plurality of photoelectric conversion devices are connected in series. 
     Preferably, at least two of the plurality of light emitting diode chips are connected in series or parallel. 
     The light emitting module may further comprise a transparent encapsulant for individually or entirely encapsulating the plurality of light emitting diode chips, and a phosphor positioned in the inside of the encapsulant or between the encapsulant and the light emitting diode chip. 
     Preferably, the light emitting module may further comprise an optical sensor for measuring external brightness, and a controller for controlling turning on and off of the light emitting diode chips based on information on the brightness provided from the optical sensor. 
     Preferably, the light emitting module may further comprise a voltage/current variable circuit. 
     In the light emitting module according to the present invention, light emitting diode chips are disposed on a first surface of a wafer, and a power supply device is disposed on a second surface opposite to the first surface, thereby improving the surface applicability of the wafer. Further, there is an advantage in that the light emitting module can remove or minimize use of an external power source. 
     A large number of wafer-level packages or light emitting modules can be fabricated by cutting a large-sized wafer having a large number of light emitting diode chips disposed thereon into a plurality of pieces. In this case, a large number of power supply devices are disposed on a second surface of the large-sized wafer, and the large-sized wafer is then cut into the plurality of pieces, so that the wafer-level package or light emitting module with the integrated light emitting diode chip and power supply device can be easily, rapidly and inexpensively fabricated. This mainly results from a decrease in the number of fabricating processes. 
     A photoelectric conversion device for converting sunlight into electricity is added to the aforementioned wafer-level package or light emitting module, so that the light emitting diode chip can be operated without external power or by minimally using external power. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a sectional view showing a light emitting module according to an embodiment of the present invention. 
         FIG. 2  is an enlarged sectional view showing circle A of  FIG. 1 . 
         FIG. 3  is an enlarged sectional view showing ellipse B of  FIG. 1 . 
         FIG. 4  is a view showing an example of an arrangement of photoelectric conversion devices in the light emitting module shown in  FIG. 1 . 
         FIG. 5  is a sectional view showing a light emitting module according to another embodiment of the present invention. 
         FIG. 6A ,  FIG. 6B , and  FIG. 6C  are sectional views showing light emitting modules having various types of encapsulants according to the present invention. 
         FIG. 7A ,  FIG. 7B , and  FIG. 7C  are sectional views showing light emitting modules having various types of light condensing means according to the present invention. 
         FIG. 8  is a block diagram showing an example of an illumination device comprising the light emitting module shown in  FIG. 1  to  FIG. 7C . 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various exemplary embodiments. It is apparent, however, that various exemplary embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring various exemplary embodiments. 
     In the accompanying figures, the size and relative sizes of layers, films, panels, regions, etc., may be exaggerated for clarity and descriptive purposes. Also, like reference numerals denote like elements. 
     When an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present. When, however, an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms “first,” “second,” etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. Thus, a first element, component, region, layer, and/or section discussed below could be termed a second element, component, region, layer, and/or section without departing from the teachings of the present disclosure. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for descriptive purposes, and, thereby, to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of an apparatus in use, operation, and/or manufacture in addition to the orientation depicted in the drawings. For example, if the apparatus in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and, as such, the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Various exemplary embodiments are described herein with reference to sectional illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments disclosed herein should not be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to be limiting. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is a part. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
       FIG. 1  is a sectional view showing a light emitting module according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a light emitting module  1  according to the embodiment of the present invention comprises a wafer  10 , a plurality of light emitting diode chips  20  disposed on a front surface of the wafer  10 , and a power supply device  80  disposed on a rear surface of the wafer  10 . The wafer  10  is preferably a silicon (Si) wafer. However, wafers made of other materials such as Al 2 O 3 , SiC, ZnO, GaAs, GaP, Bn, LiAl 2 O 3 , AlN and GaN may be used as the wafer  10 . 
     The light emitting diode chip  20  is preferably made of a Group-III nitride compound semiconductor. 
     The power supply device  80  is a device that can store and supply electric energy, and may be, for example, a capacitor, secondary battery, fuel cell, or the like. 
     According to a preferred embodiment, the power supply device  80  may comprise an anode layer  82 , a cathode layer  84 , and a solid electrolyte  86  interposed between these layers, as shown in  FIG. 2 . A first insulation film  81  is formed on one surface of the power supply device that is in contact with the wafer  10 , and a second insulation film  87  is formed on an opposite surface of the power supply device. The first insulation film  81  is provided to insulate the power supply device  80  from a portion of a via or electrode (not shown) that may be formed on the rear surface of the wafer  10 . The second insulation film  87  is provided to insulate the power supply device  80  from other electric circuits or electric components disposed in a periphery of the power supply device. 
     Although not shown, the wafer  10  is provided with a power source or power path for supplying power of the power supply device  80  to the light emitting diode chips  20 , and the power source or power path may be provided with a voltage/current variable circuit. 
     Referring back to  FIG. 1 , the light emitting module  1  comprises a plurality of photoelectric conversion devices  90  for converting sunlight from the outside into electricity and providing it to the power supply device  80 . The photoelectric conversion devices  90  are preferably integrated into the wafer  10 , but may be disposed to be spaced apart from the wafer  10 . In this case, the photoelectric conversion devices  90  may be supported by a portion of the light emitting module other than the wafer  10 , e.g., a housing (not shown) of the light emitting module  1 , or the like. 
     Referring to  FIG. 4 , the plurality of photoelectric conversion devices  90  are disposed on the rear surface of the wafer  10  to surround the periphery of the power supply device  80 . The plurality of photoelectric conversion devices  90  are connected in series by wires  91  so as to improve photoelectric conversion efficiency. A pair of terminal pads  92  are installed at both ends of an array of the photoelectric conversion devices  90 , respectively. The photoelectric conversion device  90  is preferably made of a Group III-V semiconductor compound. 
     Referring to  FIG. 3 , the light emitting chips  20  mounted on the wafer  10  are enlarged and shown. The structure, shape and arrangement of the light emitting diode chips  20  shown in  FIG. 3  is a preferred embodiment of the present invention. However, it is noted that if one or more of the light emitting diode chips  20  are disposed on the front surface of the wafer  10 , the structure, shape and arrangement of the light emitting diode chips  20  may be variously changed or modified within the technical scope of the present invention. 
     According to a preferred embodiment, grooves  11  are formed in the front surface of the wafer  10 , and the light emitting diode chips  20  are mounted on the wafer  10  so that lower portions of the light emitting diode chips are partially disposed in the grooves  11 , respectively. 
     The light emitting diode chip  20  comprises a substrate  21 , and a first conductive semiconductor layer  22 , an active layer  23  and a second conductive semiconductor layer  24 , which are laminated on the substrate  21 . The substrate  21  may be a growth substrate for growing these layers made of a compound semiconductor, and the growth substrate is preferably a sapphire substrate suitable for the growth of a Group-III nitride semiconductor. In case of a light emitting diode chip having a sapphire substrate as the growth substrate  21 , the first conductive semiconductor layer  22  may be an n-type compound semiconductor layer, and the second conductive semiconductor layer  24  may be a p-type compound semiconductor layer. Although shown, a transparent electrode layer or current diffusion layer such as an ITO layer may be formed on the second conductive semiconductor layer  24 . 
     The first conductive semiconductor layer  22 , the active layer  23  and the second conductive semiconductor layer  24  may be formed of a Group-III nitride compound semiconductor, e.g., an (Al, Ga, In)N semiconductor. Each of the first and second conductive semiconductor layers  22  and  24  may be formed to have a single or multiple layer structure. For example, the first conductive semiconductor layer  22  and/or the second conductive semiconductor layer  24  may comprise contact and clad layers, and may further comprise a superlattice layer. Also, the active layer  23  may be formed to have a single or multiple quantum well structure. 
     In this embodiment, a partial region of the first conductive semiconductor layer  22  is exposed by partially removing the second conductive semiconductor layer  24  and the active layer  23 . A first conductive electrode pad  20   a  is formed on the exposed first conductive semiconductor layer  22 , and a second conductive electrode pad  20   b  is formed on the second conductive semiconductor layer  24 . 
     Meanwhile, an insulation film  40  is formed on the front surface of the wafer  10  so as to entirely cover the light emitting diode chips  20  except the electrode pads  20   a  and  20   b.  In addition, the insulation film  40  covers not only the light emitting diode chips  20  but also the front surface of the wafer  10  in a periphery of the light emitting diode chips  20 . The insulation film  40  serves to insulate an electrode film  30  and the light emitting diode chips  20  from each other. Furthermore, the insulation film serves to insulate the semiconductor layers from each other at side surfaces of the light emitting diode chip  20 . Particularly, the insulation film  40  becomes a base layer for the electrode film  30 , a reflection film  50  and a protection film  60 . 
     Thus, the insulation film  40  also serves to variously adjust the heights of these films with respect to the light emitting diode chip  20  or its corresponding semiconductor layers, particularly the active layer, by changing the thickness of the insulation film  40 . The insulation film  40  is preferably formed of SiO 2  or an insulative material containing SiO 2  as a major component. 
     In the front surface of the wafer  10 , regions of the insulation film  40 , in which the first and second conductive electrode pads  20   a  and  20   b  of the light emitting diode chips  20  exist, are removed, and therefore, the first and second conductive electrode pads  20   a  and  20   b  are exposed from the insulation film  40 . The electrode film  30  described above is regionally formed on the insulation film  40 , to electrically connect the first and second electrode pads  20   a  and  20   b  of the adjacent light emitting diode chips to each other. 
     The electrode film  30  is preferably formed of a metal material having excellent electric conductivity. More preferably, the electrode film is formed of at least one metal material of Au, Cu and Al, or an alloy material containing the metal material. 
     The reflection film  50  for reflecting upward the light emitted from the side surfaces of the adjacent light emitting diode chips  20  is formed to cover at least a part of the electrode film  30  between the light emitting diode chips  20 . Although not specifically shown, the reflection film  50  may be formed to have a width greater than that of the electrode film  30 . In this case, a part or most of the reflection film  50  is positioned on the insulation film  40  while being in direct contact with the insulation film. At this time, the reflection film  50  is preferably positioned lower than the active layer  23  of the light emitting diode chip  20 . The reflection film  50  positioned below the active layer  23  more effectively reflects the light, which is generated from the active layer  23  and then emitted to the side surface of the light emitting diode chip  20 , so that the light can be guided in a desired direction. The reflection film  50  is preferably formed of a metal material having excellent reflexibility. More preferably, the reflection film  50  is formed of at least one metal material of Ag, Au and Ni, or an alloy material containing the metal material. Finally, the protection film  60  is provided to entirely cover the reflection film  50 , the electrode film  30 , the insulation film  40  and the light emitting diode chips  20 . 
     Although not shown, separate electrodes or electrode pads (not shown) may be further formed together with the light emitting diode chips  20  on the front surface of the wafer  10 . The electrodes or electrode pads may be connected to a conducting portions (not shown) such as vias, which are continued from the front surface of the wafer  10  to the rear surface thereof. 
       FIG. 5  shows a sectional view of a light emitting module according to another embodiment of the present invention. Referring to  FIG. 5 , in a light emitting module  1  according to this embodiment, a plurality of photoelectric conversion devices  90  together with light emitting diode chips  20  are disposed on a front surface of a wafer  10 . The plurality of photoelectric conversion devices  90  are preferably connected in series while being disposed to surround a periphery of the light emitting diode chips  20 . Like the aforementioned embodiment, a power supply device is disposed on a rear surface of the wafer  10 . 
     In  FIG. 6A ,  FIG. 6B  and  FIG. 6C , an encapsulant  71 ,  72  or  73  for protecting the light emitting diode chips  20  disposed on the front surface of the wafer  10  is shown together with the light emitting diode chips. As shown in Figs.  FIG. 6A  and  FIG. 6C , the single encapsulant  71  or  73  may be formed to cover all the light emitting diode chips  20  disposed on the front surface of the wafer  10 . The encapsulant  71  shown in  FIG. 6A  has a plurality of lens shapes corresponding to the respective light emitting diode chips  20 . Meanwhile, as shown in  FIG. 6B , a plurality of encapsulants  72  may be formed to individually cover the light emitting diode chips  20 . Phosphors for generating white light, for example, may be contained in the inside of the encapsulant  71 ,  72  or  73 , or between the light emitting diode chips  20  and the encapsulant  71 ,  72  or  73 . 
       FIG. 7A  to  FIG. 7C  show light condensing means for condensing light to the photoelectric conversion device  90 . 
     Referring to  FIG. 7A , a light condensing lens  74  such as a Fresnel lens is used as the light condensing means. In this case, sunlight passes through the light condensing lens  74  and is then condensed toward the photoelectric conversion device  90  disposed below the light condensing lens. 
     Referring to  FIG. 7B  and  FIG. 7C , a light guide  75  or  76  is used as the light condensing means. In this case, sunlight is incident through an upper incident surface of the light guide  75  or  76 . The light entering the light guide  75  or  76  moves inside of the light guide  75  or  76 , exits from the light guide  75  or  76  through a side surface of the light guide  75  or an exiting surface positioned in a hollow at the center of the light guide  76 , and then enters the photoelectric conversion device  90 . 
     For example, a prism pattern, hologram pattern or the like may be formed in a bottom surface of the light guide  75  or  76  in order to smoothly guide the light. 
     In  FIG. 7C , prism patterns having a plurality of concentric circles having different diameters about a hollow of the light guide  76  are formed in a bottom surface of the light guide  76 . The photoelectric conversion device  90  is disposed near the hollow of the light guide. In this case, the light incident on a portion distant from the center of the light guide moves to the vicinity of the hollow in which the photoelectric conversion device  90  is disposed and then enters the photoelectric conversion device  90 . 
       FIG. 8  is a block diagram showing an example of an illumination device comprising the aforementioned light emitting module. 
     The illumination device shown in  FIG. 8  comprises the light emitting diode chip  20 , the power supply device  80  and the photoelectric conversion device  90 , which are described above, and a controller  100 , a driving circuit  110  and an optical sensor  130 . Electric power generated by the photoelectric conversion device  90  is provided and stored in the power supply device  80 , and electricity of the power supply device  80  is used to operate the controller  100 , the driving circuit  110  and the light emitting diode chips  20 . The optical sensor  130  measures brightness at the installation position of the illumination device and provides the measured brightness as a signal to the controller  100 . The controller  100  then controls the driving circuit  110  based on the information on the external brightness provided from the optical sensor  130 , and turns on and off the light emitting diode chips  20  according to whether the surroundings of the illumination device are bright or dark. The illumination device may comprise a current/voltage variable circuit and an ESD protection circuit. 
     Although some exemplary embodiments are disclosed herein, it should be understood that these embodiments are not intended to be exclusive. For example, individual structures, elements, or features of a particular embodiment are not limited to that particular embodiment and can be applied to other embodiments without departing from the spirit and scope of the present disclosure.