Patent Publication Number: US-2007109788-A1

Title: Backlight module

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a backlight module, and more particularly, to a backlight module with a LED as a light-emitting element.  
      2. Description of the Prior Art  
      Please refer to  FIG. 1 .  FIG. 1  is a diagram of a conventional backlight module  100 . The backlight module  100  includes a backing plate  110 , a reflective plate  120 , a plurality of LEDs  130 , a LED driver  1306 , and a plurality of circuit boards  140  for supporting the LEDs  130 .  
      The backing plate  110  is usually made of metal material or other material with a good thermal conductivity. The lateral sides of the backing plate  110  are protruding upwardly to form a box for supporting the circuit boards  140  and for dissipating heat generated by the LEDs  130 . The reflective plate  120  is disposed between the backing plate  110  and the circuit boards  140 . The reflective plate  120  includes a plurality of openings for the LEDs  130  to pass through. The reflective plate  120  reflects light emitted from the LEDs  130  in order to increase the luminance and the uniformity of brightness of the backlight module  100 . Please refer to  FIG. 2 .  FIG. 2  is a sectional view of the conventional backlight module  100 . Each LED  130  includes a light-emitting chip  1301  for being driven so that the LED  130  emits the light, a heat-conducting structure  1302  for conducting heat generated by the LED  130 , and at least one pin  1304 . Each circuit board  140  is a printed circuit board (PCB). Each circuit board  140  includes a substrate  1402 , a copper line layer  1404 , and a solder resist layer  1406 . The pin  1304  of the LED  130  is electrically connected to the copper line layer  1404  by soldering. The circuit board  140  is electrically connected to the LED driver  1306  for driving the LED  130  to emit light.  
      Generally, the operation temperature of the LED  130  influences the light-emitting efficiency and stability of the LED  130 . When the operation temperature of the LED  130  increases, the light-emitting efficiency and stability of the LED  130  decrease. However, the substrate  1402  of the backlight module  100  is a fiber glass substrate (FR4) with a poor thermal conductivity. It causes that the heat generated by the LED  130  is not dissipated from the backing plate  110  but is gathered at the heat-conducting structure  1302 . The operation temperature of the LED  130  increases so that the light-emitting efficiency and stability of the LED  130  decrease and the voltage resistivity of the substrate  1402  decreases.  
      Please refer to  FIG. 3 .  FIG. 3  is a sectional view of another conventional backlight module  200 . The backlight module  200  includes a backing plate  210 , a reflective plate  220 , a plurality of LEDs  230 , and a plurality of metal core printed circuit boards (MCPCB)  240  for supporting the LEDs  230 . Each LED  230  includes a heat-conducting structure  2302  for conducting heat generated by the LED  230 , and at least one pin  2304 . Each metal core printed circuit board  240  includes a metal substrate  2402 , a copper line layer  2404 , a solder resist layer  2406 , and an insulating thermal membrane  2408 . The metal core printed circuit board  240  with a good voltage resistivity and thermal conductivity to dissipate the heat generated by the LED  230  effectively. However the metal core printed circuit board  240  is much more expensive than the printed circuit board made of fiber glass substrate. In addition, the insulation of the metal core printed circuit board  240  is provided by the insulating thermal membrane  2408  with a thickness about 75 to 200 μm, and the insulating thermal membrane  2408  peels off easily so as to affect the electrical contact when manufacturing the metal core printed circuit board  240  improperly.  
     SUMMARY OF THE INVENTION  
      It is therefore a primary objective of the claimed invention to provide a backlight module for solving the above-mentioned problem.  
      According to the claimed invention, a backlight module includes a heat-dissipating element such as a backing plate, at least one light-emitting element disposed on the heat-dissipating element, and a reflective plate disposed on the heat-dissipating element. The reflective plate includes at least one opening for the light-emitting element to pass through. The backlight module further includes a circuit board disposed between the heat-dissipating element and the reflective plate for driving the light-emitting element to pass through. circuit board includes at least one opening for the light-emitting element to pass through, and at least one electrical connection part for electrically connecting the circuit board and the light-emitting element.  
      According to the claimed invention, a backlight module includes a heat-dissipating pad, at least one light-emitting element disposed on the heat-dissipating pad, and a backing plate disposed on the heat-dissipating pad. The backing plate includes at least one opening for the light-emitting element to pass through. The backlight module further includes a reflective plate disposed on the heat-dissipating pad. The reflective plate includes at least one opening for the light-emitting element to pass through. The backlight module further includes a circuit board disposed between the heat-dissipating pad and the backing plate for driving the light-emitting element. The circuit board includes at least one opening for the light-emitting element to pass through, and at least one electrical connection part for electrically connecting the circuit board and the light-emitting element.  
      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  
       FIG. 1  is a diagram of a conventional backlight module.  
       FIG. 2  is a sectional view of the backlight module shown in  FIG. 1 .  
       FIG. 3  is a sectional view of another conventional backlight module.  
       FIG. 4  is a sectional view of a backlight module according to a first embodiment of the present invention.  
       FIG. 5  is an exploded diagram of the backlight module shown in  FIG. 4 .  
       FIG. 6  is a sectional view of a backlight module according to a second embodiment of the present invention.  
       FIG. 7  is a sectional view of a backlight module according to a third embodiment of the present invention.  
       FIG. 8  is a sectional view of a backlight module according to a fourth embodiment of the present invention.  
       FIG. 9  is a sectional view of a backlight module according to a fifth embodiment of the present invention.  
       FIG. 10  is a sectional view of a backlight module according to a sixth embodiment of the present invention.  
       FIG. 11  is a sectional view of a backlight module according to a seventh embodiment of the present invention.  
       FIG. 12  is a sectional view of a backlight module according to an eighth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      Please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a sectional view of a backlight module  500   a  according to a first embodiment of the present invention.  FIG. 5  is an exploded diagram of the backlight module  500   a  shown in  FIG. 4 . The backlight module  500   a  includes a backing plate  510 , a reflective plate  520 , a plurality of LEDs  530 , and a plurality of circuit boards  540 . The backing plate  510  includes at least one first protruding part  5102  and at least one second protruding part  5104 . The backing plate  510  is a heat-dissipating element and usually made of metal material or other material with a good thermal conductivity. The first protruding part  5102  supports the LED  530 , and the second protruding part  5104  supports the reflective plate  520 . The reflective plate  520  is made of metal material in order to reflect light emitted from the LED  530  so as to increase the luminance and the uniformity of the light emitted from the LED  530 . The reflective plate  520  includes an opening  5201  for the LED  530  to pass through. The LED  530  is a light-emitting element. The LED  530  includes a light-emitting chip  5301 , a heat-conducting structure  5302 , and at least one pin  5304 . The heat-conducting structure  5302  is disposed on the bottom of the light-emitting chip  5301  and connected to the first protruding part  5102  of the backing plate  510  by heat-conducting glue  550  or soldering. The heat generated by the light-emitting chip  5301  is conducted to the heat-conducting structure  5302  and the backing plate  510  and dissipated out from the backing plate  510 . The circuit board  540  is disposed on a surface of the backing plate  510  facing the reflective plate  520  and disposed between the heat-dissipating element and the reflective plate  520 . The circuit board  540  includes at least one opening  5401  for the first protruding part  5102  of the backing plate  510  and the LED  530  to pass through. The pin  5304  of the LED  530  is electrically connected to a copper line layer of the circuit board  540  facing the reflective plate  520  by soldering. A gap is located between the pin  5304  and the reflective plate  520  so as to prevent the poor electrical contact due to the connection between the pin  5304  or solder joint thereon and the reflective plate  520  made of metal material.  
      The heat-conducting structure  5302  contacts with the backing plate  510  capable of conducting and dissipating heat effectively via the opening  5401  of the circuit board  540  so as to separate the heat-dissipating path of the LED  530  from the electrical path of driving the LED  530 . That is, when a LED driver (not shown in figures) electrically connected to the circuit board  540  drives the light-emitting chip  5301  to emit the light, the heat generated by the LED  530  is conducted to the backing plate  510  from the heat-conducting structure  5302  and dissipated from the backing plate  510  instead of blocking by the circuit board  540  so as to increase the heat-dissipating efficiency of the LED  530 . In addition, the circuit board  540  is affected by less heat so as to increase the voltage resistivity of the circuit board  540 . The heat is not conducted via the circuit board  540 , and there is no need to utilize the expensive metal core printed circuit board with a good thermal conductivity so as to reduce the cost of the backlight module  500   a.    
      Please refer to  FIG. 6 .  FIG. 6  is a sectional view of a backlight module  500   b  according to a second embodiment of the present invention. The difference between the first embodiment and the second embodiment is that the circuit  540  of the backlight module  500   b  is disposed on a surface of the reflective plate  520  facing the backing plate  510  and the pin  5304  of the LED  530  is electrically connected to a surface of the circuit board  540  facing the backing plate  510 . A gap is located between the pin  5304  of the LED  530  and the backing plate  510  so as to prevent the poor electrical contact due to the connection between the pin  5304  or solder joint thereon and the backing plate  510  made of metal material.  
      Please refer to  FIG. 7 .  FIG. 7  is a sectional view of a backlight module  600   a  according to a third embodiment of the present invention. The structure of the backlight module  600   a  of the third embodiment is similar to the structure of the backlight module  500   a  according to the first embodiment of the present invention. The difference between the first embodiment and the third embodiment is described as follow. The backlight module  600   a  includes a backing plate  610  made of material with a good thermal conductivity, such as metal material. A heat-dissipating pad  660  is disposed on the backing plate  610 . The heat-dissipating pad  660  and the backing plate  610  are formed a heat-dissipating element. The heat-dissipating pad  660  includes two support parts  6602  on two lateral sides and a protruding part  6608  in the center thereof. The support parts  6602  support a reflective plate  620 . A LED  630  is disposed on the protruding part  6608 . A heat-conducting structure  6302  disposed on the bottom of the LED  630  is connected to the protruding part  6608  of the heat-dissipating pad  660  by heat-conducting glue  650 . A circuit board  640  is disposed on a surface of the heat-dissipating pad  660  facing the reflective plate  620 . The circuit board  640  includes at least one opening  6401  for the protruding part  6608  of the heat-dissipating pad  660  and the LED  630  thereon to pass through. A pin  6304  of the LED  630  is electrically connected to a copper line layer of the circuit board  640  facing the reflective plate  620  by soldering. A gap is located between the pin  6304  and the reflective plate  620  so as to prevent the poor electrical contact due to the connection between the pin  6304  or solder joint thereon and the reflective plate  620  made of metal material. The heat-dissipating pad  660  according to the third embodiment of the present invention replaces the first protruding part  5102  and the second protruding part  5104  of the reflective plate  510  according to the first embodiment of the present invention so as to simplify the structure of the reflective plate  61   0 . The heat-dissipating path of the LED  630  and the electrical path of driving the LED  630  are separated so as to increase the heat-dissipating efficiency of the LED  630 . In addition, the circuit board  640  is affected by less heat so as to increase the voltage resistivity of the circuit board  640 .  
      Please refer to  FIG. 8 .  FIG. 8  is a sectional view of a backlight module  600   b  according to a fourth embodiment of the present invention. The structure of the backlight module  600   b  according to the fourth embodiment is similar to the structure of the backlight module  600   a  according to the third embodiment of the present invention. The difference between the fourth embodiment and the third embodiment is that the backlight module  600   b  further includes an insulation tape  680  attached to the pin  6304  of the LED  630  so as to prevent the poor electrical contact due to the connection between the pin  6304  or solder joint thereon and the reflective plate  620  made of metal material.  
      Please refer to  FIG. 9 .  FIG. 9  is a sectional view of a backlight module  600   c  according to a fifth embodiment of the present invention. The structure of the backlight module  600   c  according to the fifth embodiment is similar to the structure of the backlight module  600   a  according to the third embodiment. The difference between the fifth embodiment and the third embodiment is that the circuit board  640  is disposed on a surface of the reflective plate  620  facing the heat-dissipating pad  660 . The pin  6304  of the LED  630  is electrically connected to a surface of the circuit board  640  facing the heat-dissipating pad  660 . A gap is located between the pin  6304  and the heat-dissipating pad  660  so as to prevent the poor electrical contact due to the connection between the pin  6304  or solder joint thereon and the heat-dissipating pad  660  made of metal material.  
      Please refer to  FIG. 10 .  FIG. 10  is a sectional view of a backlight module  700   a  according to a sixth embodiment of the present invention. The backlight module  700   a  includes a backing plate  710 , a reflective plate  720 , a plurality of LEDs  730 , a plurality of circuit boards  740 , and a heat-dissipating pad  760 . The backing plate  710  is made of metal material with a good thermal conductivity. The reflective plate  720  is disposed on the backing plate  710 . Both of the reflective plate  720  and the backing plate  710  include at least one opening for the LED  730  to pass through. The heat-dissipating pad  760  is disposed under the backing plate  710 . The heat-dissipating pad  760  includes two support parts  7602  on two lateral sides and a protruding part  7608  in the center thereof. The support parts  7602  support the backing plate  710 . The heat-dissipating pad  760  further includes a thermal fin (not shown in  FIG. 10 ). The LED  730  is a light-emitting element. The LED  730  includes a light-emitting chip  7301 , a heat-conducting structure  7302 , and at least one pin  7304 . The heat-conducting structure  7302  is connected to the protruding part  7608  of the heat-dissipating pad  760  by heat-conducting glue  750 . The heat generated by the LED  730  is conducted to the heat-conducting structure  7302  and the heat-dissipating pad  760  and dissipated out from the heat-dissipating pad  760 . The circuit board  740  is disposed on a surface of the reflective plate  720  facing the heat-dissipating pad  760  and disposed between the heat-dissipating pad  760  and the backing plate  720 . The circuit board  740  includes at least one opening  7401  for the protruding part  7608  of the heat-dissipating pad  760  and the LED  730  thereon to pass through. The pin  7304  of the LED  730  is electrically connected to a copper line layer of the circuit board  740  facing the heat-dissipating pad  760  by soldering. A gap is located between the pin  7304  and the heat-dissipating pad  760  so as to prevent the poor electrical contact due to the connection between the pin  7304  or solder joint thereon and the heat-dissipating pad  760  made of metal material. When a LED driver (not shown in  FIG. 10 ) electrically connected to the circuit board  740  drives the light-emitting chip  7301  to emit light, the heat generated by the LED  730  is conducted to the heat-dissipating pad  760  via the heat-conducting structure  7302  so as to dissipate heat effectively. The heat-dissipating path of the LED  730  and the electrical path of driving the LED  730  are separated so as to increase the heat-dissipating efficiency of the LED  730 . In addition, the circuit board  740  is affected by less heat so as to increase the voltage resistivity of the circuit board  740 .  
      Please refer to  FIG. 11 .  FIG. 11  is a sectional view of a backlight module  700   b  according to a seventh embodiment of the present invention. The structure of the backlight module  700   b  according to the seventh embodiment is similar to the structure of the backlight module  700   a  according to the sixth embodiment of the present invention. The difference between the seventh embodiment and the sixth embodiment is that the backlight module  700   b  further includes a thermal pad  7604 . The thermal pad  7604  includes a plurality of thermal fins. The thermal pad  7604  is attached to the heat-dissipating pad  760  by heat-conducting glue  7502  or the thermal pad  7604  is formed with the heat-dissipating pad  760  integrally so as to increase the heat-dissipating efficiency further.  
      Please refer to  FIG. 12 .  FIG. 12  is a sectional view of a backlight module  700   c  according to an eighth embodiment of the present invention. The structure of the backlight module  700   c  according to the eighth embodiment is similar to the structure of the backlight module  700   a  according to the sixth embodiment of the present invention. The difference between the eighth embodiment and the sixth embodiment is that the backlight module  700   c  further includes a heat pipe  790 . The heat pipe  790  is installed inside the heat-dissipating pad  760  and connected to the heat-conducting structure  7302  of the LED  730  so as to increase the heat-dissipating efficiency and temperature uniformity of the LED  730  further.  
      In contrast with the conventional backlight module, the present invention separates the heat-dissipating path of the LED and the electrical path of driving the LED so as to increase the heat-dissipating efficiency of the LED. In addition, the circuit board is affected by less heat so as to increase the voltage resistivity of the circuit board. Because the heat is not conducted via the circuit board, there is no need to utilize the expensive metal core printed circuit board with a good thermal conductivity so as to reduce the cost of the backlight module.  
      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. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.