Abstract:
A method for assembling light emitting diode units and a substrate in a light source module and a structure thereof are provided. The light emitting diode unit is made of a light emitting diode and a carrier. Every light emitting diode has a flanged profile in the bottom to form a leaned plane, and a corresponding hole is formed on the substrate. Hence, when the light emitting diodes are pressed on the surface of a radiator by the substrate to make a closer contact, the light emitting diodes will be able to bear the pressure by the flanged design.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to a light source module, and more particularly relates to a method and structure for assembling light emitting diode units and a substrate in a light source module. 
   DESCRIPTION OF THE PRIOR ART 
   In the light source module of the prior art, the method and structure for assembling light emitting diode units and a substrate and the step of attaching the assembly structure on a radiator are provided in  FIG. 1A  to  FIG. 1C . Now referring to  FIG. 1A , a cross-sectional view of the light source module comprising a plurality of light emitting diode units  12  and a substrate  11  to carry the light emitting diode units  12  is shown. The substrate  11  has a first surface  111  (in the bottom) and a second surface  112  (in the top) corresponding to each other. A plurality of through holes  113  are formed to pass through the substrate  11 . The patterned conductive circuit  114  is formed in the first surface  111  of the substrate  11 . 
   Still referring to  FIG. 1A , each light emitting diode unit  12  comprises a light emitting diode  121  and a carrier  122 . A plurality of leads  124  are electrically connected to the light emitting diode  121  and extend out from the sidewalls of the carrier  122 . 
   Referring to  FIG. 1B , when the light emitting diode unit  12  is moved and passed through the corresponding through hole  113  from the first surface  111 , the light emitting diode  121  passes through the substrate  11  and over the second surface  112 . And the exposed lead  124  is leaned on a patterned conductive circuit  114  on the surrounding area of the through hole  113 . Then, a solder  13  can be used to bond the lead  124  to the patterned conductive circuit  114  to complete the electrical connection between the light emitting diode unit  12  and the substrate  11  and the structure. 
   Referring to  FIG. 1C , in order to efficiently dissipate the heat generated in the operation of the light emitting diode unit  12 , the light emitting diode unit  12  and the substrate  11  which are bonded together can be turned  180  degrees so as to lean the bottom of the carrier  122  of the light emitting diode unit  12  against the thermal pad  14 . And the thermal pad  14  is contacted with the surface of the radiator  15 . However, when a downward pressure is applied to the substrate  11  along the direction of the arrow to achieve a tighter contact between the light emitting diode units  12  and the substrate  11  and increase the efficiency of the heat dissipation, the substrate  11  transfers the downward pressure to the lead  124  of the light emitting diode units  12  which bends the lead and damages the patterned conductive circuit  114 . 
   SUMMARY OF THE INVENTION 
   According to the drawbacks described above, the structure for assembling the light emitting diode unit and the substrate cannot be closely connected to the radiator. An assembling method and structure of the light emitting diode unit and the substrate are provided herein. The purpose is to let the light emitting diode units closely attached on the radiator and the light emitting diode unit wouldn&#39;t be damage. 
   According to the purpose described above, an assembling method and structure of a light source module including light emitting diode units and a substrate are provided. The bottom of a carrier of a light emitting diode unit for carrying a light emitting diode has a fixed portion with a leaned plane. A through hole is formed in a substrate, and the diameter thereof is larger than the diameter of the light emitting diode but smaller than that of the fixed portion. Therefore, when the light emitting diode is attached on the radiator, the pressure from the substrate would render the light emitting diode unit and the substrate contacting tightly and increase the efficiency of the heat dissipation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompany drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
       FIGS. 1A-1C  show the conventional steps of assembling light emitting diode units to the substrate and a radiator; 
       FIGS. 2A-2C  show the steps of the preferred embodiment of the present invention for assembling light emitting diode units to a substrate and a radiator; 
       FIG. 2D  is a 3-Dimensional view illustrating the light source module in the preferred embodiment of the present invention; 
       FIG. 2E  is a 3-Dimensional view illustrating an assembly structure of a substrate with through trenches and light emitting diode units; 
       FIGS. 2F and 2G  are cross-sectional drawings illustrating a reflective sheet formed on the light source module according to the preferred embodiment of the present invention; 
       FIG. 2H  is a cross-sectional drawing illustrating a heat sink attaching on a light source module according to the preferred embodiment of the present invention; and 
       FIG. 2I-2J  are the drawings illustrating two embodiments of a fixed portion of a light emitting diode unit in the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The following is the detailed description of the present invention, which describes the light source module of the invention, but the detailed structure and the operating theory are not discussed. The portions relating to the conventional techniques are briefly described, and the parts of the drawings are not proportionally drafted. While embodiments are discussed, it is not intended to limit the scope of the present invention. Except expressly restricting the amount of the components, it is appreciated that the quantity of the disclosed components may be greater than that of disclosed. 
   One of the preferred embodiments of the present invention provides an assembling method and structure of a light source module including light emitting diode units and a substrate and the assembly structure can closely attached on a radiator. Now referring to  FIG. 2A , a cross-sectional view is shown. The light source module comprises a plurality of light emitting diode units and a substrate used to carry the light emitting diode units. In the present embodiment, the substrate  21  comprises a printed circuit board or any other multi-layer board. The substrate  21  has a first surface  211  (on the bottom) and a second surface  212  (on the top) corresponding to each. other. And a plurality of through holes are formed in the substrate  21  and are corresponding to the position of the light emitting diode units. Beside, a patterned conductive circuit  214  which is formed by a copper layer or other conductive layer is exposed on the first surface  211  of the substrate  21 . 
   Still referring to  FIG. 2A , the light emitting diode unit  22  comprises a light emitting diode  221  and a carrier  222 . Wherein the diameter of the light emitting diode  221  is smaller than the diameter of the first through hole  213 . However, the bottom of the carrier  222  extends to form a fixed portion, which has a larger diameter than the diameter of the first through hole  213 . A plurality of leads  224  electrically connecting to the light emitting diode  221  extend from two sides of fixed portion  223 . 
   Referring to  FIG. 2B , when the light emitting diode units  22  are moved is going through the corresponding first surface  211  of the first through hole  213 , the light emitting diode  221  can pass through the first through hole  213  and exposed on the second surface  212  of the substrate  21 . The fixed portion  223  is on the first surface  211  and the portion close to the first through hole  213  cannot be passed through. Solders  23  are used to bond the leads  224  to the patterned conductive circuit  214  to complete the electrical connection between the light emitting diode unit  22  and the substrate  21  of the assembly structure. 
   Referring to  FIG. 2C , the heat generated in the operation of the light emitting diode  221  can be dissipated by turning the light emitting diode unit  22  and the substrate  21  180 degrees and connecting with a radiator  25  via the connection between a plurality of thermal pads  24  and the bottom of the carrier  222 . The carrier  222  provided in the present invention includes a fixed portion  223  and the diameter is larger than the diameter of the first through hole  213 . Therefore, the downward pressure applied along the direction of the arrow results in a tight contact/connection between the light emitting diode unit  22  and the radiator  25  and increases the efficiency of the heat dissipation. Therefore, the deformation of the lead of the carrier in the light emitting diode unit of the prior art when a downward pressure is applied and the problem of the peeling of the patterned conductive circuit can be avoided. 
   A 3-Dimensional view of a light source module of the invention is shown in  Fig. 2D , wherein each light emitting diode  221  passes through the corresponding through hole  213  and exposed on the second surface  212  of the substrate  21 . In other embodiments of the present invention, the substrate has through trenches corresponding to a plurality of light emitting diode units as shown in  FIG. 2E . The width of the through trench  215  is larger than the diameter of the light emitting diode  221  but smaller than the diameter of the fixed portion  223 . Therefore, a plurality of the light emitting diodes  221  pass through the through trench  215  and are exposed on the second surface  212  of the substrate  21 . The fixed portion of each light emitting diode unit has a leaned plane  2231  against the surrounding area of the through trench  215  of the first surface of the substrate  21 . 
   Furthermore, referring to  FIG. 2F , a reflective component can be added on the substrate  21  depending on the properties of the light emitting diode unit  22  or the need of the light source module in the present invention. For example, if the light emitting diode  221  is a side emitting light emitting diode  22 , a reflective sheet  26  (or a reflective surface) can be attached/formed on the second surface  212  of the substrate  21  and a plurality of second through holes  261  are formed in the positions corresponding to the first through hole  213  in the reflective sheet  26 . In addition, the diameter of the second through hole  261  is larger than the diameter of the light emitting diode as shown in  FIG. 2F . The light emitting diode  221  directly passes through the second through hole  261  and extends out the reflective sheet  26 . Alternatively, in other embodiments of the present invention, second through holes having a diameter, which is equal to the diameter of the carrier and smaller than the diameter of the first through hole  2 l 3  ,can be formed in the reflective sheet  26 . As shown in  FIG. 2G , the reflective sheet  26  is close to the light emitting diode and the loss of light can be avoided. Thus the illumination output will be more efficient. 
   Besides, in other embodiments of the present invention, the radiator can be chosen from a heat dissipation sheet or a heat sink as shown in  FIG. 2H  to increase the effect of the heat dissipation. The thermal pad  24  disposed between the bottom of the carrier  222  and the heat sink  27  can be a whole piece as shown in  FIG. 2H . 
   Referring to  FIG. 2I  and  FIG. 2J , two embodiments of the light emitting diode units  22  of the present invention are shown. Each fixed portion  223  is the extension of the bottom of the carrier  222  and has a leaned plane  2231 . When the light emitting diode  221  and the carrier  222  pass through the first through hole from the top of the substrate, the fixed portion having a diameter larger than the through hole can lean against the first through hole by the leaned plane and the bonding of the lead  224  and the patterned conductive circuit can be performed successfully. Besides, when the assembly structure of the light emitting diode units  22  and the substrate uses the thermal pad to lean against the surface of the radiator, the pressure on the light emitting diode from the substrate cannot be transferred to the lead  224 , which is bonded with the patterned conductive circuit. The shape of the fixed portion of the light emitting diode unit  22  provided in the present invention, as shown in  FIG. 2I  and  FIG. 2J , is a cube or a cylinder and can be formed with a leaned plane having a larger diameter than the diameter of the through hole to achieve a similar leaned effect. 
   The foregoing description is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. In this regard, the embodiment or embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.