Abstract:
An LED light bar includes a plurality of LEDs and a circuit board supporting the LEDs. Solder points are formed on a bottom surface of the LEDs. An anti-solder layer is coated on the circuit board so as to create a plurality of discrete anti-solder pads. A first tenon which is formed on each of the LEDs locates in a void in a corresponding one of the anti-solder pads so as to position the LEDs precisely on the circuit board and maintain their positions.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure relates to light emitting diodes, and particularly to an LED light bar and a method for manufacturing the LED light bar. 
         [0003]    2. Description of the Related Art 
         [0004]    Light emitting diodes (LEDs) have many advantages, such as high luminosity, low operating voltage, low power consumption, compatibility with integrated circuits, long term reliability, and environmental friendliness which have promoted their wide use as a light source. Now, light emitting diodes are commonly applied in environmental lighting. 
         [0005]    A common LED light bar includes a circuit board and a plurality of LEDs arranged on the circuit board. A method for manufacturing the common LED light bar is that solder paste is coated on solder points arranged on the bottom surface of the common LED. The LED is arranged on the circuit board and the solder points are arranged on the connection areas of the circuit board. And then, an electrically connection is completed by a reflow process. However, the solder points may be misaligned with the connection areas of the circuit board because the melting solder causes the LED to shift. That affects the quality of the LED light bar. 
         [0006]    Therefore, it is desirable to provide a particularly to an LED light bar and a method for manufacturing the LED light bar which can overcome the described limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present LED light bar and a method for manufacturing the LED light bar. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0008]      FIG. 1  is a cross-sectional view of an LED light bar in accordance with a first embodiment. 
           [0009]      FIG. 2  is an enlarged drawing of circle II of the LED light bar of  FIG. 1 . 
           [0010]      FIG. 3  is the process flow of the manufacturing of the LED light bar of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of an LED light bar and a method for manufacturing the LED light bar as disclosed are described in detail here with reference to the drawings. 
         [0012]    Referring to  FIG. 1 , an LED light bar  1  includes an LED  10 , and a circuit board  20  supporting the LED  10 . 
         [0013]    The LED  10  includes a substrate  11 , a first electrode  12  and a second electrode  122  arranged on the substrate  11 , an LED chip  13  arranged on the first electrode  12  and electrically connecting with the first electrode  12  and the second electrode  122  via two metallic wires  17 , and an encapsulation  14  covering the LED chip  13  and the metallic wires  17  on the substrate  11 . 
         [0014]    The substrate  11  is a plate, and a first tenon is arranged on a bottom surface. In this embodiment, the first tenon which is extending from the bottom surface of the substrate  11  is a protrusion  15 . The protrusion  15  is in the shape of a symmetrical trapezoid, having the longest side on the bottom surface of the substrate  11 . The protrusion  15  has at least one inclined plane  151  inclining upwards towards the bottom surface of the substrate  11 . 
         [0015]    In this embodiment, a cross section of the protrusion  15  shows two inclined planes  151  extending downwards from the bottom surface of the substrate  11 , and a flat  152  connecting to the two inclined planes  151 . The flat  152  is parallel to the bottom surface of the substrate  11 . In other embodiments, the protrusion  15  can have any other geometry having the two inclined planes  151 . The substrate  11  can be sapphire, silicon, ceramic and metal and is formed in one piece. 
         [0016]    The first and second electrodes  12 ,  122  arranged on the substrate  11  extend from the top surface of the substrate  11  to the bottom surface of the substrate  11 . Solder points  16  are formed on bottoms of the first and second electrodes  12 ,  122  for electrically connecting to the circuit board  20 . The thickness of the solder point  16  is the same as the height of the protrusion  15 . 
         [0017]    The circuit board  20  is used for supporting the LED  10 . The LED  10  is connected to an external power source by the circuit board  20 . The circuit board  20  is plate. An anti-solder layer  21  is arranged on the top surface of the circuit board  20 . The anti-solder layer  21  forms a plurality of anti-solder pads  24  which are separated from each other. A solder area(s)  22  respectively defined by adjacent anti-solder layers  21  is exposed for connecting to the solder points  16  of the LED  10 . A second engaging unit arranged on a part of the anti-solder pad  24  is used for embedding the protrusion  15  of the LED  10 . In this embodiment, the second engaging unit is the recession  23  which acts as an initial guide and final locator for the protrusion  15  of the LED  10 . Each of the three adjacent anti-solder pads  24  on a straight line corresponds to the LED  10 . Two solder areas  22  are formed between each of the three adjacent anti-solder pads  24 . Two solder areas  22  connect to the two solder points  16  of the LED  10 . The second engaging unit is arranged at the center of the anti-solder pad  24  between the two solder areas  22  and is used for engaging the first tenon. The thickness of the anti-solder layer  21  is less than the thickness of the solder point  16  of the LED  10 . 
         [0018]    The position of the recession  23  depends upon the protrusion  15  of the LED  10 . When the protrusion  15  meets the anti-solder pad  24 , the solder points  16  of the LED  10  make contact with the two solder areas  22  on either side of the anti-solder pad  24 . 
         [0019]    Referring to  FIG. 2 , when the LED  10  is arranged on the circuit board  20 , the protrusion  15  of the LED  10  enters the recession  23 , and the LED  10  is thus arranged on the circuit board  20 . The recession  23  is a square void in a center of the anti-solder pad  24 . The width of the recession  23  exceeds the smallest width of the protrusion  15  and is less than the largest width of the protrusion  15 . 
         [0020]    When the protrusion  15  is inserted into the recession  23 , until the flat  152  of the protrusion  15  makes contact with the circuit board  20 , the inclined plane  151  of the protrusion  15  contacts a side surface  231  of the recession  23  as defined by the anti-solder pads  24 . In this embodiment, the smallest width of the protrusion  15  is equal to the width of the flat  152  of the protrusion  15 . The side surface  231  of the recession  23  as defined by the anti-solder pads  24 , by the inclined plane  151  of the protrusion  15 , and by the top surface of the circuit board  20  forms a right triangle  30 , where the height “h” of the right triangle  30  is equal to the thickness of the anti-solder pad  24 . The length of the bottom “d” of the right triangle  30  is one half of the distance between two adjacent anti-solder pads  24 , subtracting the width of flat  152  of the protrusion  15 . The ratio of the height “h” and the length of the bottom “d” is equal to or greater than 2:1. 
         [0021]    By applying this ratio, it can be ensured that the protrusion  15  is embedded into the recession  23 . The length of the bottom “d” of the right triangle  30  is equal to the installation tolerance of the LED  10 . For example, when the installation tolerance of the LED  10  is 0.1 mm, the length of the bottom “d” is at least 0.1 mm and the height is at least 0.2 mm. Thus, it can be ensured that the protrusion  15  is embedded into the recession  23  firmly. Because the protrusion  15  of the LED light bar extending from the bottom surface of the substrate  11  contacts the circuit board  20 , any heat from the LED chip  13  is conducted quickly to the circuit board  20  by the protrusion  15 . Thus, that enhances the heat dissipation of the LED light bar. 
         [0022]    In another embodiment, the first tenon can be the recession  23  from the bottom surface of the substrate  11  caving towards an inside of the bottom surface of the substrate  11 . The second engaging unit can be the protrusion  15  extending from the top surface of the anti-solder pad  24 . The protrusion  15  of the anti-solder pad  24  enters the recession  23  with the substrate  11 . Thus, the LED  10  can be precisely fixed. 
         [0023]      FIG. 3  shows the process flow of the manufacturing of the LED light bar. A method for the manufacturing the LED light bar includes the following steps: 
         [0024]    Provide the LED  10 , with solder points  16  arranged on the bottom surface of the LED  10 . The first tenon is arranged on the bottom surface of the LED  10 . The first tenon is the protrusion  15  extending from the bottom surface of LED  10 . The height of the protrusion  15  is equal to the thickness of the solder points  16 . 
         [0025]    Provide the circuit board  20 , with an anti-solder layer  21  coated on the top surface of the circuit board  20 . A plurality of the anti-solder pads  24  is formed on the anti-solder layer  21 . Two solder areas  22  are formed between every three adjacent anti-solder pads  24 . The second engaging unit is arranged on the middle one of the three adjacent anti-solder pads  24 . 
         [0026]    The LED  10  is arranged on the circuit board  10 . The protrusion  15  is aligned with the second engaging unit. Thus, the protrusion  15  of the LED  10  is embedded in the second engaging unit. Therefore, the solder points  16  of the LED  10  are always maintained in precise alignment with two solder areas  22 . 
         [0027]    The circuit board  20  carrying the LED  10  is placed in the oven. Thus, the solder paste of the solder areas  22  melts. And then, cooling down. Thus, the solder areas  22  become conductively fixed on the solder points  16  of the LED  10 . 
         [0028]    While the disclosure has been described by way of example and in terms of an exemplary embodiment, it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.