Abstract:
A light emitting apparatus includes a substrate, a first metal layer, at least one light emitting device and a protective layer for covering the light emitting device. The first metal layer is disposed on the substrate and includes a structure for increasing the light emitting efficiency. The light emitting device is disposed at a predetermined position of the first metal layer and on the substrate. The light emitting device emits a light and the light is then reflected and concentrated to project out by the structure of the first metal layer. Thus, the light emitting efficiency is improved.

Description:
DETAILED DESCRIPTION OF THE INVENTION 
     Cross Reference To Related Applications 
       [0001]    This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 095115255 filed in Taiwan, Republic of China on Apr. 28, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The invention relates to a light emitting apparatus and in particular to a light emitting apparatus having good heat dissipating efficiency. 
         [0004]    2. Related Art 
         [0005]    With the development of the opto-electronic industry, light emitting devices, such as LEDs (Light Emitting Diodes), have been widely and variously applied to display functions of electronic products. 
         [0006]    Referring to  FIG. 1 , a conventional LED light emitting apparatus  1  includes a substrate  10 , an insulating layer  11 , a plurality of LED light emitting devices  12 , a metal layer  13  and a package layer  14 . The insulating layer  11  is disposed on the substrate  10 . The light emitting devices  12  are disposed on the insulating layer  11 . The metal layer  13  is disposed on the insulating layer  11  and is electrically connected to the light emitting devices  12  by way of wire bonding. The package layer  14  covers the LED light emitting devices  12  so as to protect the light emitting devices  12  from being influenced and damaged by mechanical factors, heat, moisture or other factors. 
         [0007]    When the conventional LED light emitting apparatus  1  emits lights, parts of the lights leaks from the lateral side of the light emitting device  12  and the outputted lights can not be completely converged onto the light emitting surface, so that the light emitting efficiency cannot be effectively enhanced. Meanwhile, with the development of ever higher efficiency and ever higher luminance of the light emitting apparatus  1 , the light emitting device  12  also generates heat during its operation, and the accumulated heat raises the temperature, influencing the light emitting efficiency and shortening the lifetime of the light emitting device  12 . Further, because the conventional light emitting device  12  is disposed on the insulating layer  11  with a poor heat dissipating property, and the airtight seal of the package layer  14  prevents the heat generated by the light emitting device  12  from being dissipated easily, the heat dissipating problem becomes increasingly significant. 
         [0008]    It is therefore a subject of the invention to provide a light emitting apparatus, which can be manufactured simply and has high light emitting efficiency, high heat dissipating effect and reduced cost. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the foregoing, the invention is to provide a light emitting apparatus, which can be manufactured simply and has high light emitting efficiency, high heat dissipating effect and reduced cost. 
         [0010]    To achieve the above, the invention discloses a light emitting apparatus including a substrate, a first metal layer, at least one light emitting device and a protective layer. The first metal layer is disposed on the substrate and has a structure for increasing the light emitting efficiency. The light emitting device is disposed at a predetermined position of the first metal layer and on the substrate, and the protective layer covers the light emitting device. 
         [0011]    As mentioned hereinabove, the light emitting device is disposed at the predetermined position of the first metal layer in the light emitting apparatus according to the present invention. Regarding to the material characteristics of the first metal layer, an insulating layer can be directly formed after performing a ceramization procedure, and the light emitting device can be disposed on the insulating layer. Also, the light emitting efficiency is enhanced because the structure on the first metal layer can reflect and concentrate the light outputted from the light emitting device. Meanwhile, superior heat dissipating effect and thus longer lifetime of the light emitting apparatus may be achieved by using the substrate which has advantages of good thermal conductivity, large area, and may be composed of metal or alloys to guide and dissipate the heat generated by the light emitting device during operation. Compared with the prior art, it is unnecessary to dispose and attach a heat sink in this invention. So, it is possible to reduce the manufacturing cost, reduce the manufacturing time, simplify the manufacturing steps, avoid the problems of high thermal resistance and ageing caused by the heat sink, and thus enhance the heat dissipating efficiency and the product reliability. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein: 
           [0013]      FIG. 1  is a schematic illustration showing a conventional LED light emitting apparatus; and 
           [0014]      FIGS. 2 to 5  are schematic illustrations showing various light emitting apparatuses according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
         [0016]    Referring to  FIG. 2 , a light emitting apparatus  2  according to a first embodiment of the invention includes a substrate  20 , a first metal layer  23 , a first insulating layer  21 , a connecting layer  26 , a second metal layer  23 ′, at least one light emitting device  22  and a protective layer  29 . 
         [0017]    In this embodiment, the material of the substrate  20  is mainly composed of the material with good thermal conductivity for providing proper heat dissipating efficiency. Preferably, the material of the substrate  20  is copper, copper alloy, or a thermal conductive material. 
         [0018]    The first metal layer  23  of the light emitting apparatus  2  is disposed on the substrate  20 . The material of the first metal layer  23  includes aluminum, magnesium, titanium or their alloys. Considering of the material characteristics of the first metal layer  23 , the first insulating layer  21  may be directly formed by oxidizing, nitridizing or carbidizing the surface of the first metal layer  23 . The material of the first insulating layer  21  accordingly may be aluminum oxide, magnesium oxide, titanium oxide, aluminum nitride, magnesium nitride, titanium nitride, aluminum carbide, magnesium carbide or titanium carbide. Also, the first metal layer  23  has a structure  201  for increasing the light emitting efficiency. 
         [0019]    The light emitting device  22  is disposed at a predetermined position of the first metal layer  23  and on the substrate  20 . In this embodiment, the light emitting device  22  includes a first electrode, a second electrode and a light emitting layer (not shown). More specifically, the light emitting device  22  may be a light emitting diode (LED), a laser diode (LD) or an organic light emitter diode (OLED). 
         [0020]    The light emitting apparatus  2  of this embodiment may further include a second metal layer  23 ′ disposed on the first insulating layer  21 . The second metal layer  23 ′ is directly electrically connected to the light emitting device  22 , preferably, by wire bonding. The material of the second metal layer  23 ′ may be silver, gold, copper, aluminum or alloys thereof. 
         [0021]    In order to dispose the second metal layer  23 ′ on the first insulating layer  21 , the connecting layer  26  may further be formed between the second metal layer  23 ′ and the first insulating layer  21 . The connecting layer  26  is adhesive, or has a property of enabling the second metal layer  23 ′ to be formed thereon. For example, the initial layer required may be made of chromium, titanium, nickel or alloys thereof when the second metal layer  23 ′ is formed by way of plating. 
         [0022]    In this embodiment, the protective layer  29  is disposed on the light emitting device  22  to cover and protect the light emitting device  22 . Meanwhile, the surface shape of the protective layer  29  are curved so that the protective layer  29  functions as a lens for diverging or converging the light outputted from the light emitting device  22  to meet various display requirements. 
         [0023]    In this embodiment, the structure  201 , for increasing the light emitting efficiency on the surface of the first metal layer  23 , is a recess of spherical shape, elliptical shape or parabolic shape. Preferably, the light emitting device  22  is disposed at a focus of the recess. Thus, when the lateral light outputted from the light emitting device  22  strikes the structure  201 , the curved structure  201  can reflect and converge the lateral light generated by the light emitting device  22  and then output the converged lateral light. Thus, the light emitting efficiency may be directly enhanced. In addition, the light emitting apparatus  2  may further include a reflective layer  28  disposed on the structure  201 , as shown in  FIG. 4 , for enhancing the effects of reflection and convergence for the lateral light of the light emitting device  22 . The material of the reflective layer  28  may include silver, gold or nickel. 
         [0024]    In addition, the invention provides the second embodiment, shown in  FIG. 3 , in which the light emitting apparatus  2  further includes a second insulating layer  21 ′. The material of the second insulating layer  21 ′ may be aluminum oxide, magnesium oxide, titanium oxide, aluminum nitride, magnesium nitride, titanium nitride, aluminum carbide, magnesium carbide, titanium carbide, or their combinations, and may be deposited by oxidizing, nitridizing or carbidizing the surface of the first metal layer  23 . 
         [0025]    A third metal layer  23 ″ may be additionally disposed on the second insulating layer  21 ′ and electrically connected to the light emitting device  22  via a wire  24 . In order to enable the third metal layer  23 ″ to be disposed on the second insulating layer  21 ′, a connecting layer  26  may also be formed between the third metal layer  23 ″ and the second insulating layer  21 ′. The connecting layer  26  is adhesive or has a property of enabling the third metal layer  23 ″ to be formed thereon. For example, the initial layer required may be made of chromium, titanium, nickel or alloys thereof when the third metal layer  23 ″ is formed by way of plating. 
         [0026]    In this embodiment, the light emitting device  22  is electrically connected to the third metal layer  23 ″ via the wires  24  so that the light emitting device  22  may be directly disposed at the predetermined position of the first metal layer  23  so that it become unnecessary to dispose the insulating layer at the predetermined position. Of course, this is only an example and is not for limitations of the present invention. 
         [0027]    The invention also provides another light emitting apparatus  2  according to the third embodiment, as shown in  FIG. 4 . The light emitting device  22  is electrically connected to an external circuit via a lead frame  27  disposed on the second insulating layer  21 ′. The lead frame  27  has a first electrode pin  271  and a second electrode pin  272 , which may be respectively connected to the first electrode (not shown) and the second electrode (not shown) of the light emitting device  22  via the wires  24 . 
         [0028]    As shown in  FIG. 5 , the second insulating layer  21 ′ according to the fourth embodiment of the invention may also cover the external surface of the substrate  20 . There is a plurality of connecting pads  25  disposed under the substrate  20  for being electrically connected with the light emitting device  22 . The third metal layer  23 ″ above the second insulating layer  21 ′ is electrically connected to the first electrode and the second electrode of the light emitting device  22 . The connecting pads  25  may be electrically connected to the second metal layers  23 ′ via wires (not shown) or the conductive layers  24 ′, respectively. To be noted, the above-mentioned connection way by wire is for illustrations only and is not for limitations of the present invention. For example, a U-shaped metal element (not shown) may be used to clip one side of the light emitting apparatus  2  so as to construct the second metal layer and connecting pads with the same functions of the previously mentioned elements. Thus, the connecting pads  25  underneath the second insulating layer  21 ′ may be electrically connected to the external circuit by way of surface mount technology (SMT). 
         [0029]    In summary, the first metal layer of the light emitting apparatus is formed with the structure for increasing the light emitting efficiency, and the light emitting device is disposed at the predetermined position of the first metal layer in the light emitting apparatus according to the present invention. Regarding to the material characteristics of the first metal layer, an insulating layer can be directly formed after performing a ceramization procedure, and the light emitting device can be disposed on the insulating layer. Also, the light emitting efficiency is enhanced because the structure on the first metal layer can reflect and concentrate the light outputted from the light emitting device. Meanwhile, superior heat dissipating effect and thus longer lifetime of the light emitting apparatus may be achieved by using the substrate which has advantages of good thermal conductivity, large area, and may be composed of metal or alloys to guide and dissipate the heat generated by the light emitting device during operation. Compared with the prior art, it is unnecessary to dispose and attach a heat sink in this invention. So, it is possible to reduce the manufacturing cost, reduce the manufacturing time, simplify the manufacturing steps, avoid the problems of high thermal resistance and ageing caused by the heat sink, and thus enhance the heat dissipating efficiency and the product reliability. 
         [0030]    Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.