Abstract:
The present invention is related to a light emitting diode having an adhesive layer provided with heat paths. In the present invention, an adhesive layer is formed to bond the substrate and the LED stack. There are a plurality of metal protrusions or semiconductor protrusions passing through the adhesive layer to form heat-dissipation paths to improve the heat-dissipation effect of the LED so as to enhance the stability and the light-emitting efficiency of the LED.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to an LED having an adhesive layer, and more particularly, to an LED having an adhesive layer formed with a plurality of heat paths.  
         [0003]     2. Description of the Related Art  
         [0004]     LEDs are widely utilized today, for example, in optical displays, traffic signs, data storage, communication devices, lighting devices, and medical devices. Therefore, increasing the luminance of LEDs is an important consideration in producing LEDs.  
         [0005]     U.S. Publication No. 2003/0155579 discloses an LED and the production method thereof. The production method is to form an LED epitaxial structure on a light-absorbing first substrate, and utilize a polymer dielectric adhesive layer to connect the surface of the LED epitaxial structure to a second substrate of high thermal conductivity. This increases the heat-dissipation efficiency of the chip, and increases the light-emitting efficiency of the LED. In the above-mentioned patent, the epitaxial layer is formed on the light-absorbing first substrate and the adhesive layer is utilized to connect the epitaxial layer to the second substrate. Then, the first substrate is removed to reduce the thermal resistance, raise the heat-dissipation efficiency, and raise the light-emitting efficiency. However, because the thermal resistance of the LED is about equal to the sum of thermal resistances of the epitaxial layer, the dielectric adhesive layer, and the second substrate, wherein the thermal conductivity of the dielectric adhesive layer is between 0.1 W/mk and 0.3 W/mk, the LED cannot well utilize the heat-dissipation characteristic of the second substrate of high thermal conductivity. Therefore, the LED has a disadvantage of low heat-dissipation.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore an object of the invention to provide a method of solving the heat-dissipation problem of an LED having an adhesive layer, and a method of solving the heat-dissipation problem of a high-power LED.  
         [0007]     In order to solve the above-mentioned disadvantage, the inventor got an inventive concept of providing a plurality of heat paths in the form of a plurality of metal protrusions or semiconductor protrusions passing through or penetrating into the adhesive layer for bonding an LED stack and a substrate so that the heat generated by the LED stack can be dissipated to the substrate through the heat paths. This can efficiently solve the heat-dissipation problem of an LED having an adhesive layer, or of a high power LED.  
         [0008]     In order to achieve the above-mentioned object, the present invention discloses an LED having formed with heat paths. The LED comprises a high heat-dissipation substrate, an adhesive layer formed with a plurality of heat path protrusions on the high heat-dissipation substrate, a reflective layer formed on the adhesive layer, an electrical insulation layer formed on the reflective layer, and a transparent conductive layer formed on the electrical insulation layer, wherein the protrusions pass through or penetrate into the adhesive layer to form heat paths. Furthermore, the upper surface of the transparent conductive layer comprises a first surface area and a second surface area. The LED comprises a first contact layer formed on the first surface area, a first cladding layer formed on the first contact layer, a light-emitting layer formed on the first cladding layer, a second cladding layer formed on the light-emitting layer, a second contact layer formed on the second cladding layer, a first wire bonding electrode formed on the second contact layer, and a second wire bonding electrode formed on the second surface area. In addition, another electrical insulation layer can be formed between the high heat-dissipation substrate and the adhesive layer. This is also within the spirit of the present invention.  
         [0009]     The above-mentioned high heat-dissipation substrate is made of a material selected from the group consisting of GaP, Si, SiC, and metal.  
         [0010]     The above-mentioned heat path protrusions can be in the form of metal heat path protrusions or semiconductor heat path protrusion, the heat path protrusions are made of a material selected from the group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, PbSn, AuZn, GaP, Si, SiC, and the like.  
         [0011]     The above-mentioned adhesive layer is made of a material selected from the group consisting of Pi, BCB, PFCB, and the like.  
         [0012]     The above-mentioned reflective layer is made of a material selected from the group consisting of In, Sn, Al, Au, Pt, Zn, Ag, Ti, Pb, Pd, Ge, Cu, AuBe, AuGe, Ni, PbSn, and AuZn.  
         [0013]     The above-mentioned electrical insulation layer is made of a material selected from the group consisting of SiNx, SiO2, Al2O3, TiO2, and the like.  
         [0014]     The above-mentioned transparent conductive layer is made of a material selected from the group consisting of Tin Indium oxide, Tin Cadmium Oxide, Tin Antimony Oxide, Zinc Oxide, and Tin Zinc Oxide.  
         [0015]     The above-mentioned first contact layer is made of a material selected from the group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, and AlGaN.  
         [0016]     The above-mentioned first cladding layer is made of a material selected from the group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, and AlGaInN.  
         [0017]     The above-mentioned light-emitting layer is made of a material selected from the group consisting of AlGaInP, InGaP, GaN, AlGaN, InGaN, and AlGaInN.  
         [0018]     The above-mentioned second cladding layer is made of a material selected from the group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, and AlGaInN.  
         [0019]     The above-mentioned second contact layer is made of a material selected from the group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, and AlGaN.  
         [0020]     The above and other objects of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments that are illustrated in the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0021]      FIG. 1  is a diagram of a preferred embodiment of an LED structure in accordance with the present invention.  
         [0022]      FIG. 2  is a diagram of another preferred embodiment of an LED structure in accordance with the present invention.  
         [0023]      FIG. 3  is a diagram of a yet another preferred embodiment of an LED structure in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Embodiment 1  
       [0024]     Referring to  FIG. 1 , an LED comprises a high heat-dissipation substrate  11 , an adhesive layer  13  having a plurality of heat path protrusions  12  formed on the high heat-dissipation substrate  11 , a reflective layer  14  formed on the adhesive layer  13 , an electrical insulation layer  15  formed on the reflective layer  14 , and a transparent conductive layer  16  formed on the electrical insulation layer  15 , wherein the protrusions  12  pass through or penetrate into the adhesive layer  13  to form heat paths, and the upper surface of the transparent conductive layer  16  comprises a first surface area and a second surface area. The LED further comprises a first contact layer  17  formed on the first surface area, a first cladding layer  18  formed on the first contact layer  17 , a light-emitting layer  19  formed on the first cladding layer  18 , a second cladding layer  20  formed on the light-emitting layer  19 , a second contact layer  21  formed on the second cladding layer  20 , a first wire bonding electrode  9  formed on the second contact layer  21 , and a second wire bonding electrode  8  formed on the second surface area of the transparent layer  16 . Furthermore, another electrical insulation layer can also be formed between the high heat-dissipation substrate and the adhesive layer. This is also within the spirit of the present invention.  
       Embodiment 2  
       [0025]     Referring to  FIG. 2 , an LED comprises a high heat-dissipation substrate  10  having a plurality of heat path protrusions, an electrical insulation layer  111  formed on the high heat-dissipation substrate  10 , an adhesive layer  13  formed on the electrical insulation layer  111 , and a transparent conductive layer  16  formed on the electrical insulation layer  111  and the adhesive layer  13 , wherein the protrusions pass through or penetrate into the adhesive layer  13 , and the transparent conductive layer  16  comprises a first surface area and a second surface area. The LED further comprises a first contact layer  17  formed on the first surface area, a first cladding layer  18  formed on the first contact layer  17 , a light-emitting layer  19  formed on the first cladding layer  18 , a second cladding layer  20  formed on the light-emitting layer  19 , a second contact layer  21  formed on the second cladding layer  20 , a first wire bonding electrode  9  formed on the second contact layer  21 , and a second wire bonding electrode  8  formed on the second surface area of the transparent conductive layer  16 .  
       Embodiment 3  
       [0026]     Referring to  FIG. 3 , which is a diagram of another preferred embodiment of an LED providing with an adhesive layer formed with a plurality of heat paths in accordance with the present invention. This embodiment is quite similar to embodiment 1. The difference between them lies in that the upper surface of the electrical insulation layer  15  comprises a plurality of first surface areas and a plurality of second surface areas, and a plurality of transparent conductive layers  16  are respectively formed on the first surface areas of the electrical insulation layer  15 . Furthermore, the upper surfaces of the transparent conductive layers  16  comprise a plurality of first surface areas and a plurality of second surface areas, and a plurality of LED stacking layers are respectively formed on the first surface areas of the transparent conductive layers. In addition, the LED stack comprises a first contact layer  17 , a first cladding layer  18 , a light-emitting layer  19 , a second cladding layer  20 , a second contact layer  21 , an electrical insulation layer  112  formed on the second surface area of the electrical insulation layer  15  and the LED stack, an electrode  7  formed on the second surface areas of the transparent conductive layers  16  and connected to the second contact layer  21  of the adjacent LED stack, a first wire bonding electrode  9  formed on a specific second contact layer  21 , and a second wire bonding electrode  8  formed on a second surface area of a specific transparent conductive layer  16 . The above-mentioned LED stacks are electrically connected to each other by demands to form an LED array.  
         [0027]     The above-mentioned high heat-dissipation substrate is made of a material selected from the group consisting of GaP, Si, SiC, and metal.  
         [0028]     The above-mentioned heat path protrusion can be a metal heat path protrusion or a semiconductor heat path protrusion, where the heat path protrusion is made of a material selected from the group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, PbSn, AuZn, GaP, Si, SiC, and the like.  
         [0029]     The above-mentioned adhesive layer is made of a material selected from the group consisting of Pi, BCB, PFCB, and the like.  
         [0030]     The above-mentioned reflective layer is made of a material selected from the group consisting of In, Sn, Al, Au, Pt, Zn, Ag, Ti, Pb, Pd, Ge, Cu, AuBe, AuGe, Ni, PbSn, and AuZn.  
         [0031]     The above-mentioned electrical insulation layer is made of a material selected from the group consisting of SiNx, SiO2, Al2O3, TiO2, and the like.  
         [0032]     The above-mentioned transparent conductive layer is made of a material selected from the group consisting of Tin Indium oxide, Tin Cadmium Oxide, Tin Antimony Oxide, Zinc Oxide, and Tin Zinc Oxide.  
         [0033]     The above-mentioned first contact layer is made of a material selected from the group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, and AlGaN.  
         [0034]     The above-mentioned first cladding layer is made of a material selected from the group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, and AlGaInN.  
         [0035]     The above-mentioned light-emitting layer is made of a material selected from the group consisting of AlGaInP, InGaP, GaN, AlGaN, InGaN, and AlGaInN.  
         [0036]     The above-mentioned second cladding layer is made of a material selected from the group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, and AlGaInN.  
         [0037]     The above-mentioned second contact layer is made of a material selected from the group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, and AlGaN.  
         [0038]     Those skilled in the art can readily understand that numerous modifications and alterations of the device and method may be made within the scope and spirit of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.