Abstract:
A light emitting diode package includes a substrate, several light emitting diodes mounted on the substrate, and a package member enveloping the light emitting diodes. The light emitting diodes are electrically coupled to the substrate. The package member includes at least two layers, the first layer and the second layer. The first layer is spread on the substrate and completely covers the light emitting diodes and the wires. The second layer is formed on the first layer. Fluidity of colloid forming the second layer is worse than that of the first layer. A method is also provided to manufacture the present light emitting diode package.

Description:
FIELD 
     The disclosure relates to a semiconductor package structure, and particularly relates to a light emitting diode package and manufacturing method thereof. 
     BACKGROUND 
     There are a variety of package ways for light emitting diodes, such as chip on board (COB) package. COB package is obtained by mounting a light emitting chip on a printed circuit board and further coating the light emitting chip with resin. The resin has good waterproofing quality and prevents moisture and dust from infiltrating into the light emitting diode package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures: 
         FIG. 1  is a cross-section view of a light emitting diode package in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 2  is a flow chart of a method for manufacturing the light emitting diode package in  FIG. 1 . 
         FIG. 3  is a top view of the light emitting diode package processed after a step of wiring in  FIG. 2 . 
         FIG. 4  is a top view of the light emitting diode package processed by a first colloid injection step in  FIG. 2 . 
         FIG. 5  is a top view of the light emitting diode package processed by a second colloid injection step in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the exemplary embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the exemplary embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure. 
     Referring to  FIG. 1 , a light emitting diode package  100  in the present disclosure includes a substrate  10 , a plurality of light emitting diodes  20  mounted on the substrate  10 , and a package member. In this exemplary embodiment, the package member includes two layers. The two layers are named as a first layer  30  and a second layer  40 . The first layer  30  and the second layer  40  are formed on the substrate  10  in sequence. The first layer  30  is configured to cover the light emitting diodes  20 . The second layer  40  is formed on the first layer  30 . 
     The substrate  10  is a board with a conductive circuit (not shown), such as a ceramic substrate, a metal substrate, a PLCC and so on. The substrate  10  is flat. The substrate  10  includes a bottom surface  11  and a top surface  12  opposite to the bottom surface  11 . The top surface  12  is used for carrying the light emitting diodes  20 . A plurality of bonding areas  13 , first electrodes  14  and second electrodes  15  are configured on the top surface  12 . A number of the first/second electrodes  14 / 15  is equal to that of the bonding areas  13 . Each first electrode  14  and a corresponding second electrode  15  are fixed on two sides of a corresponding bonding area  13 , respectively. 
     Each light emitting diode  20  includes a P-type electrode  21  and an N-type electrode  22 . The light emitting diodes  20  are fixed on the bonding areas  13  respectively. The P-type electrode  21  of the light emitting diode  20  is electrically connected to the first electrode  14  of the substrate  10  through a wire  51 . The N-type electrode  22  of the light emitting diode  20  is electrically connected to the second electrode  15  of the substrate  10  through a wire  52 . The wires  51  and  52  can be selected from copper, gold and other appropriate metal material. In this exemplary embodiment, the wires  51  and  52  are gold wire. 
     The first layer  30  is formed on the top surface  12  of the substrate  10 . The first layer  30  covers the light emitting diodes  20  and wires  51 ,  52  completely. The first layer  30  is spread on the top surface  12 . The first layer  30  includes a pasting surface  31  and a supporting surface  32 . The pasting surface  31  is attached on the substrate  10 . The supporting surface  32  is used for supporting the second layer  40 . In this exemplary embodiment, the supporting surface  32  is flat. In other embodiments, the supporting surface  32  can also be a concave cured surface recessed toward the substrate  10 . 
     The second layer  40  is formed on the supporting surface  32  of the first layer  30 . The second layer  40  is located above the light emitting diodes  20  and wires  51 ,  52 . The second layer  40  can be hemispherical shaped. The second layer  40  includes an adhesion surface  41  and a curved molding surface  42 . The adhesion surface  41  is adhered on the supporting surface  32  of the first layer  30 . The curved molding surface  42  is protruded backward from the substrate  10 . The fluidity of colloid composing the first layer  30  is greater than the fluidity of colloid composing of the second layer  40 . 
     Compared to traditional package structures, the light emitting diode package  100  in the present disclosure does not use a cofferdam structure to limit colloid overflow. So a height of the package member (the first layer  30  and the second layer  40 ) can be flexibly adjusted by controlling differences in fluidity and volume of colloid of the package member according to different requests. The height of the package member can even be higher than 0.5 mm. Thereof, a package structure with a relatively high height and a desired shape can be obtained. Because of the high height of the package member, the light emitting diode package  100  obtains a large light mixing distance, which can achieve better optical extraction efficiency. 
     A method for manufacturing a light emitting diode package  100  is also provided in the present disclosure. Referring to  FIG. 2 , the method of manufacturing the light emitting diode package  100  includes steps as following: 
     Step 1: die bonding. A substrate and a plurality of light emitting diodes are provided. The light emitting diodes are mounted on the substrate. 
     Step 2: wiring. A plurality of wires are provided. The light emitting diodes are electrically connected to the substrate through the wires. 
     Step 3: first colloid injecting. A first colloid is provided. The first colloid is injected on one side of the substrate where the light emitting diodes mounted on. 
     Step 4: roasting. The first colloid is roasted until it is semi-solidified to form a first layer. 
     Step 5: second colloid injecting. A second colloid is provided. The second colloid is injected on the first layer. The fluidity of the first colloid is greater than the fluidity of the second colloid. 
     Step 6: solidifying. The second colloid is roasted to form a second layer. The first layer and the second layer are completely solidified. 
     The detail steps of manufacturing the light emitting diode package  100  is described as following: 
     Referring to  FIG. 3 , a substrate  10  is provided. A plurality of bonding areas  13 , first electrodes  14  and second electrodes  15  are configured on the top surface  12  of the substrate  10 . A plurality of light emitting diodes  20  are provided. Each light emitting diode  20  is fixed on the substrate  10  with a process of die bonding. In this exemplary embodiment, die bonding is processed in a common way: the light emitting diodes  20  are positioned on a surface of a gum machine with a silver layer scraped; a right amount of sliver paste is pointed on the bonding areas  13  of the substrate  10 ; each light emitting diodes  20  is fixed on a corresponding bonding area  13  through a thorn crystal pen. Then the substrate  10  is put into a heat circulation oven to stand for a period of time and then is removed until the sliver paste solidified. 
     A plurality of wires  50  are provided. In this exemplary embodiment, the wires  50  are gold wires. The light emitting diodes  20  are electrically connected to the substrate  10  by a wire bonder. 
     Referring to  FIG. 4 , a first colloid  33  is provided. The first colloid  33  is injected on the top surface  12 . The first colloid  33  is spread on the top surface  12  and covers the light emitting diodes  20  and wires  50  completely. The substrate  10  is put into a heat circulation oven to stand for a period of time until the first colloid  33  is semi-solidified to form the first layer  30 . 
     Referring to  FIG. 5 , a second colloid  43  is provided. The fluidity of the first colloid  33  is greater than the fluidity of the second colloid  43 . The second colloid  43  is injected on the supporting surface  32  of the first layer  30 . The substrate  10  is put into a heat circulation oven to stand for a period of time until the first layer  30  and the second colloid  43  are completely solidified. The second colloid  43  is solidified as a second layer  40  on the first layer  30 . The second layer  40  is hemispherical. 
     In aforesaid processes, phosphor may also be doping in the first colloid  33  and the second colloid  43 . 
     Kinds of the first colloid  33  and the second colloid  43  may be different. In this exemplary embodiment, the first colloid  33  and the second colloid  43  are the same and both of them are silica gel. But in this exemplary embodiment, viscosity coefficient of the first colloid  33  rages from 5000 to 6000 mpas and viscosity coefficient of the second colloid  43  is 3400 mpas. In other embodiments, the first colloid  33  and the second colloid  43  may also be other types of colloid. 
     In a process of the first colloid injection, because of greater fluidity, the first colloid  33  is spread on the top surface  12  of the substrate  10  more quickly and easily with covering the light emitting diodes  20  and wires  50 . 
     In the process of the second colloid injection, when the second colloid  43  is injected on the first colloid  33 , weight of the second colloid  43  is insufficient to overcome the flow-ability of the semi-solidified first colloid  33 , thereof the supporting surface  32  of the first layer  30  remains flat. Herein, a solidification degree of the first colloid  33  can be adjusted by controlling solidification time. In this exemplary embodiment, the fluidity of the second colloid  43  is greater than the fluidity of the semi-solidified first layer  30 . The second colloid  43  cannot destroy horizontality of the supporting surface  32  of the first layer  30 . So the second colloid  43  does not fall into the inside of the first layer  30  or even contact the light emitting diodes  20  or wires  50 , further with damaging the integrity of the structural. Because of lower fluidity, the second colloid  43  does not spread on the first layer  30 , but be hemispherical under the effect of its cohesion. In other exemplary embodiments, the solidification time of roasting the first colloid  33  can be shortened, then the supporting surface  32  of the first layer  30  can be slightly recessed toward the substrate  10  to form a concave curved surface under the weight of the second colloid  43 . 
     Colloid volume of the first colloid  33  and the second colloid  43  are quantificationally controlled by an injection machine, thereby maintaining consistency of the molding of the first layer  30  and the second layer  40 . 
     Compared to traditional package structures, the light emitting diode package  100  in the present disclosure does not use a cofferdam structure to limit colloid overflow. The package member is formed under the worse mobility between two silica layers and cohesion of the silica layers. The step of configuring a cofferdam structure can be omitted in the manufacturing process, so that the production method is simpler. 
     The embodiment shown and described above is only an example. Many details are often found in the art such as the other features of the package members. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.