Abstract:
A light emitting diode (LED) device including a transparent substrate, a plurality of LED chips, a circuit, and a transparent encapsulant is provided. The LED chips are fixed on the transparent substrate, and utilized for radiating at least a light beam. The circuit is disposed on the transparent substrate and electrically connected to the LED chips. The transparent encapsulant is utilized for packaging the LED chips. The light beam of the LED chips can propagate from two opposite sides of the transparent substrate. Blue LED chips and the circuit of the transparent substrate can be directly soldered, and the phosphors are arranged to convert the wavelength of blue light, so a dual-side white light emitting device can therefore be provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a dual-side white light emitting device and a method of packaging the same. 
         [0003]    2. Description of the Prior Art 
         [0004]    Compared with traditional cold cathode light source, the LED package components are smaller in size, lower in power consumption, while having a better performance in brightness, colorfulness and a higher reaction speed to allow for high-frequency operation. Besides, the components of LED package are environmentally friendly in that they are recyclable and impact resistant. Also they can be easily developed into thin-and-small sized products. All those advantages described above make the LED packages more competitive in the market. Generally speaking, the traditional LED package includes a package cup and a LED chip which is fixed on the cup. The traditional package cup has two inner terminals and two outer terminals. The inner terminals can be soldered to the positive electrode and negative electrode of the LED to form the electric connection. And the outer terminals are used to electrically connect to an opaque printed circuit board (PCB). In addition, the PCB also provides electric connection with external controlling device via its outer terminal which enables ECD to get electronically connected with the LED chip through the circuit of PCB and package cup. 
         [0005]    As mentioned above, traditional method of LED integration is to mount the LED chip on the cup to form a LED package. Then, several LED package components are connected to PCB to form a LED device. In addition to the inevitable increase in its size, the complexity of production will also grow accordingly, which not only increases the production costs but also limits the application of LED device at the same time. Therefore, to produce a light LED device providing excellent optical effect is an important challenge in the development of LED technology. 
       SUMMARY OF THE INVENTION 
       [0006]    Therefore, one of the objectives of this invention is to provide an LED device and the related package method to simplify the process and minimize the size. The provided LED device can also be used as a dual-side white LED. 
         [0007]    According to the preferred embodiment of the present invention, an LED device includes a first transparent substrate, a plurality of LED chips mounted on the first transparent substrate to emit at least one light beam having a first wavelength, a transparent encapsulant encapsulating the LED chips, and a circuit formed on the first transparent substrate. The circuit is electrically connected to the LED chips. The LED chips emit a part of the light beam in one side of the first transparent substrate and emit a part of light beam penetrating through the first transparent substrate in the opposite side thereof. 
         [0008]    From one aspect of the present invention, a method of packaging an LED device is disclosed. First, a first transparent substrate is provided. Subsequently, a circuit is formed on the first transparent substrate. Next, a plurality of LED chips are mounted on the transparent substrate, and electrically connecting the LED chips to the circuit. Furthermore, a transparent encapsulant is formed on the first transparent substrate to encapsulate the LED chips. 
         [0009]    Since this invention placed the LED chip on the first transparent substrate, the LED package is also a dual-side white LED. Moreover, the LED chip is directly fixed on the first transparent substrate, and electrically connected with it. Therefore, this invention can simplify the production of LED and provide a light LED device. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic structural diagram illustrating a LED device in accordance with a first preferred embodiment of the present invention. 
           [0012]      FIG. 2  is a schematic top view illustrating the first transparent substrate shown in  FIG. 1 . 
           [0013]      FIG. 3  is a schematic explosion diagram illustrating the LED chips and the first transparent substrate shown in  FIG. 1 . 
           [0014]      FIG. 4  is a schematic explosion diagram illustrating a LED device in accordance with a second preferred embodiment of the present invention. 
           [0015]      FIG. 5  is a schematic structural diagram illustrating the LED chips shown in  FIG. 4 . 
           [0016]      FIG. 6  is a schematic structural diagram illustrating a LED device in accordance with a third h preferred embodiment of the present invention. 
           [0017]      FIG. 7  is a schematic structural diagram illustrating a LED device in accordance with a fourth preferred embodiment of the present invention. 
           [0018]      FIG. 8  is a schematic flow chart illustrating a method of packaging a LED device according to a fifth preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Please refer to  FIG. 1  through  FIG. 3 .  FIG. 1  is a schematic structural diagram illustrating a LED device  100  in accordance with a first preferred embodiment of the present invention,  FIG. 2  is a schematic top view illustrating the first transparent substrate  124  shown in  FIG. 1 , and  FIG. 3  is a schematic explosion diagram illustrating the LED chips  128  and the first transparent substrate  124  shown in  FIG. 1 . As shown in  FIG. 1 , an LED device  100  can include a first transparent substrate  124 , a plurality of LED chips  128  mounted on the first transparent substrate  124 , and a transparent encapsulant  130  covering the LED chips  128 . The first transparent substrate  124  can include any light-pervious materials, such as a glass substrate or a plastic substrate. The LED chips  128  can be various types LED chips. It is preferred that each of the LED chips  128  may emits uniform light from both the top surface and the bottom surface, and the emitted light can has a wavelength in the range between 380 nanometers (nm) and 680 nm, but should not be limited thereto. Since the LED chips is disposed on the transparent substrate in the present invention, and the LED chip  128  may emits uniform light from both the top surface and the bottom surface, a dual-side light emitting device can therefore be provided. Although nine the LED chips  128  are shown in  FIG. 1  for illustration, number of the LED chips  128  should not be limited by the drawings in the present invention. 
         [0020]    The transparent encapsulant  130  can include any proper geometric shapes. In this embodiment, the transparent encapsulant may be semispherical encapsulants, and each of the semispherical encapsulants can encapsulate a corresponding LED chip  128 . The transparent encapsulant  130  can include insulating and light-pervious materials that can be solidified and waterproof, such as epoxy resin or silica gel. In addition, the LED chip  128  may be a LED chip with a small wavelength range of the light, so the LED chips  128  may not emit a predetermined color light or a pure white light directly. In order to provide a LED device  100  emitting light in predetermined color, the transparent encapsulant  130  may have at least one first phosphor material  146 . The first phosphor material  146  converts a part of the light beam having the first wavelength into a light beam having a second wavelength, and the remaining light beam having the first wavelength and the light beam having the second wavelength are mixed to form a predetermined color light. For example, when the light beam emitted by the LED chips  128  is blue light, the first phosphor material  146  may be a yellow-light emitting phosphor, and a yellow light emitted by the first phosphor material  146  and the remaining blue light are mixed to form a predetermined white light. Therefore, the LED device  100  may be a dual-side white light emitting device. In another embodiment, the first phosphor material  146  may include a red-light emitting phosphor and a green-light emitting phosphor. The red light and the green light emitted by the first phosphor material  146 , and the remaining blue light emitted by the LED chips  128  are mixed to form a white light. 
         [0021]    In the first embodiment, the first transparent substrate  124  may optionally include a second phosphor material  148  to adjust the appeared light color emitted from the LED chips  128  through the first transparent substrate  124 , and the second phosphor material and the first phosphor material may includes the same materials. In another embodiment, the first transparent substrate  124  may include no phosphor. 
         [0022]    As shown in  FIG. 2 , the LED device  100  may include a circuit  150  disposed on the surface of the first transparent substrate  124 , and the LED chips  128  may be arranged as a dot matrix on the surface of the first transparent substrate  124 . The specific positions of the LED chips  128  should not be limited by  FIG. 2 . For clearness, the LED chips  128  are shown as a transparent structure in  FIG. 2 . In fact, the LED chips  128  may be opaque. The circuit  150  may include a plurality of first conductive lines  151  and a plurality of second conductive lines  152 . Both the first conductive line  151  and the second conductive line  152  have an external terminal  154  for electrically connecting the LED chips  128  to an external control device (not shown in the drawings). The control device may being electrically connected to both the first conductive lines  151  and the second conductive lines  152  to control the LED chips  128 . The LED chips  128  disposed in one line are parallel connected to one of the first conductive lines  151 , and the LED chips  128  disposed in one column are parallel connected to one of the second conductive lines  152 . 
         [0023]    As shown in  FIG. 3 , each of the LED chips  128  may have a first electrode  132  and a second electrode  134 . The first conductive lines  151  and the second conductive lines  152  may be electrically connected to the first electrodes  132  and the second electrodes  134  of the LED chips  128  respectively to control each of the LED chips  128 . In order to increase the reliability of connecting the LED chips  128 , a connecting material  155  may be included to mount the LED chips  128  on the first transparent substrate  124 . For clearness, both the LED chips  128  and the connecting material  155  are shown as a transparent structure in  FIG. 3 . In fact, the LED chips  128  and the connecting material  155  may be opaque. It is preferred that the connecting material  155  is a eutectic metal, a silver colloid or a silver paste. The eutectic metal, the silver colloid or the silver paste can directly mount the LED chips  128  on the first transparent substrate  124 , and electrically connecting the LED chips  128  to the circuit  150  on the first transparent substrate  124 . 
         [0024]    In the aforementioned embodiment, the transparent encapsulant includes semispherical encapsulants  130  to encapsulate the LED chips  128  respectively, so the individual shapes, sizes or the phosphor material of the transparent encapsulant  130  may be adjusted according to the product requirement or the types of the LED chips  128 , and the aforementioned embodiment may use fewer material amount of the transparent encapsulant  130  for the package. However, the present invention should not be limited thereto. In other embodiments, different packaging forms may be adopted in different structures of the LED devices in the present invention. 
         [0025]    Please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a schematic explosion diagram illustrating a LED device  200  in accordance with a second preferred embodiment of the present invention, and  FIG. 5  is a schematic structural diagram illustrating the LED chips  200  shown in  FIG. 4 . As shown in  FIG. 4  and  FIG. 5 , the LED device  200  may include a first transparent substrate  124 , a second transparent substrate  126 , a plurality of LED chips  128  mounted on the first transparent substrate  124  and arranged in a dot matrix, a transparent encapsulant  230  disposed between the first transparent substrate  124  and the second transparent substrate  126 , and a circuit disposed on the first transparent substrate  124  and electrically connected to the LED chips  128 . The said circuit in this embodiment is similar to the circuit  150 , and not shown in  FIG. 4  and  FIG. 5 . The first transparent substrate  124  can include any light-pervious materials, such as a glass substrate or a plastic substrate, and a connecting material  155  may be included to mount the LED chips  128  on the first transparent substrate  124 , but should not be limited thereto. 
         [0026]    The transparent encapsulant  230  may be coated on the first transparent substrate  124 , and is disposed on all the LED chips  128 . The transparent encapsulant  230  can include insulating and light-pervious materials that can be solidified and waterproof, such as epoxy resin or silica gel. In order to provide a LED device  100  emitting light in predetermined color, the transparent encapsulant  130  may also have at least one first phosphor material  146 . The first phosphor material  146  may include a yellow-light emitting phosphor, or include a red-light emitting phosphor and a green-light emitting phosphor, but should not be limited thereto. 
         [0027]    Accordingly, this embodiment not only can simplify the process of forming the transparent encapsulant  230 , but also can protect both the top surface and the bottom surface of the LED chips  128  by the second transparent substrate  126  and the first transparent substrate  124  respectively. As a result, the LED device  200  is more suitable for applying as a dual-side light emitting device. 
         [0028]    The present invention may further include spacers in order to keep a space between the first transparent substrate  124  and the second transparent substrate  126  for disposing the LED chips  128 . Please refer to  FIG. 6  and  FIG. 7 .  FIG. 6  and  FIG. 7  are schematic structural diagrams illustrating a LED device  300  and a LED device  400  in accordance with a third and fourth preferred embodiments of the present invention respectively. As shown in  FIG. 6 , the main difference between the LED device  200  and the LED device  300  is that the LED device  300  may further include at least one spacer, such as a pad  156 , disposed around the LED chips  128 . For instance, the LED device  300  may further include a rectangular frame-like pad surrounding all the LED chips  128  to keep a space between the first transparent substrate  124  and the second transparent substrate  126  for disposing the LED chips  128 . The height H of the pad  156  is preferably larger than the thickness of the LED chips  128 , and the pad  156  may preferably include transparent materials. As shown in  FIG. 7 , the main difference between the LED device  200  and the LED device  400  is that the transparent encapsulant  230  of the LED device  400  may further include a plurality of spacers, such as spherical spacers  158  in this embodiment. The spherical spacers  158  may directly mixed in materials of the transparent encapsulant  230  so as to keep a space between the first transparent substrate  124  and the second transparent substrate  126  for disposing the LED chips  128 . The diameter D of the spherical spacers  158  may larger than the thickness of the LED chips  128 , and the spherical spacers  158  may preferably include transparent materials. 
         [0029]    Furthermore, a method of packaging a LED device is provided to the utilization of the transparent substrate in the present invention. Please refer to  FIG. 8 .  FIG. 8  is a schematic flow chart illustrating a method of packaging a LED device according to a fifth preferred embodiment of the present invention. This flow chart may shows the aforementioned steps of forming the structures of the first through the fourth embodiments, so the structures shown in  FIG. 1  through  FIG. 5  may also be referred to in the steps of  FIG. 8 . 
         [0030]    As shown in  FIG. 8 , a transparent substrate is first provided, such as the first transparent substrate  124 . Subsequently, at least one metal evaporation process and at least one lithography process are performed in turn to form a circuit  150  on the surface of the first transparent substrate  124 . Thereafter, at least one spacer is disposed on the first transparent substrate  124  to support the first transparent substrate  124  and the following-formed second transparent substrate  126 . Next, a plurality of LED chips  128  are provided. The LED chips  128  may be directly mounted on the first transparent substrate  124  by a conductive glue or eutectic materials, and a eutectic metal, a silver colloid or a silver paste may electrically connecting the LED chips  128  to the circuit  150  on the first transparent substrate  124 . After that, a second transparent substrate  126  covering the LED chips  128  is provided. 
         [0031]    Next, a transparent encapsulant is formed on the first transparent substrate  124  to encapsulate the LED chips  128 . For example, the transparent encapsulant  130  or the transparent encapsulant  230  may be formed, and the transparent encapsulants  130 ,  230  may include at least one phosphor material. The transparent encapsulant may be disposed on the first transparent substrate  214  by coating process or may be disposed between the first transparent substrate  124  and the second transparent substrate  126  by filling process. Thereafter, a curing process may be preformed on the transparent encapsulants  130 ,  230  to form the LED device. 
         [0032]    In comparison with the traditional LED device, the present invention may include the following benefits. First, since a transparent substrate is utilized to support the LED chips in the present invention, the LED device can therefore be a dual-side light emitting device. Subsequently, since the transparent encapsulant or the transparent substrate may have phosphor materials to adjust the appeared light color of the LED device, the LED device may be a dual-side white light emitting device. In addition, since the LED chips are directly mounted on the transparent substrate, and may be directly connected to the circuit of the transparent substrate, processes of packaging the LED device may be simplified in the present invention, and a chip-level LED device can be provided. Furthermore, the LED chips of the present invention may be arranged as a dot matrix on the transparent substrate, and the circuit has metal traces arranged as a checker corresponding to the LED chips can turn on/off each of the LED chips. Thus, the LED device can be a display device that shows images or information on two opposite side, a lighting device that can adjust its brightness, luminance or light-emitting description, or a light source module. It is noticed that the arrangement of the LED chips should not be limited to the above-mentioned embodiment in the present invention, and the LED chips may be arranged in a single line, in random, or the present invention may even include only one LED chip in an LED device. 
         [0033]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.