Abstract:
A circuit board for driving a flip-chip light emitting chip is disclosed. The circuit board includes a metal substrate having a first surface and a second surface, the first surface including a first electrode area, a second electrode area and a heat conduction area; a first metal electrode formed on the first electrode area for providing a first voltage; a first insulation layer formed between the first metal electrode and the metal substrate; a second metal electrode formed on the second electrode area for providing a second voltage; a second insulation layer formed between the second metal electrode and the metal substrate; and a solder resist layer covering the first surface; wherein the heat conduction area is exposed from the solder resist layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a circuit board for driving a flip-chip light emitting chip and a light emitting module, and more particularly, to a circuit board for driving a flip-chip light emitting chip and a light emitting module capable of improving heat dissipation efficiency. 
         [0003]    2. Description of the Prior Art 
         [0004]    Since light emitting diodes (LEDs) have advantages of long service life, small size and low power consumption, the light emitting diodes are widely used in various kinds of illumination devices. Generally, when temperature of the light emitting diodes rises, light emitting efficiency of the light emitting diodes is significantly decreased and service life of the light emitting diodes is reduced as well. As the light emitting diodes are gradually used for various kinds of illumination devices, the heat dissipation problem of the light emitting diodes becomes more important. 
         [0005]    In the prior art, a substrate for carrying light emitting diodes is made of aluminum oxide (Al 2 O 3 ) or other materials with insulation and high heat-conductive characteristics, so as to dissipate heat of the light emitting diodes. However, thermal conductivity of the aluminum oxide is still lower than thermal conductivity of a metal material. Therefore, the prior art cannot further improve heat dissipation efficiency of a light emitting diode illumination device. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a circuit board for driving a flip-chip light emitting chip and a light emitting module, in order to solve the problems of the prior art. 
         [0007]    The circuit board for driving the flip-chip light emitting chip of the present invention comprises a metal substrate having a first surface and a second surface opposite to the first surface, the first surface comprising a first electrode area, a second electrode area and a heat conduction area; a first metal electrode formed on the first electrode area for providing a first voltage; a first insulation layer formed between the first metal electrode and the metal substrate; a second metal electrode formed on the second electrode area for providing a second voltage; a second insulation layer formed between the second metal electrode and the metal substrate; and a solder resist layer covering the first surface of the metal substrate; wherein the heat conduction area is exposed from the solder resist layer. 
         [0008]    The light emitting module of the present invention comprises a flip-chip light emitting chip and a circuit board. The flip-chip light emitting chip comprises a first electrode and a second electrode. The circuit board comprises a metal substrate having a first surface and a second surface opposite to the first surface, the first surface comprising a first electrode area, a second electrode area and a heat conduction area; a first metal electrode formed on the first electrode area for providing a first voltage to the first electrode of the flip-chip light emitting chip; a first insulation layer formed between the first metal electrode and the metal substrate; a second metal electrode formed on the second electrode area for providing a second voltage to the second electrode of the flip-chip light emitting chip; a second insulation layer formed between the second metal electrode and the metal substrate; and a solder resist layer covering the first surface of the metal substrate; wherein the heat conduction area is exposed from the solder resist layer and the heat conduction area is connected to the flip-chip light emitting chip. 
         [0009]    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 
         [0010]      FIG. 1  is a diagram showing a circuit board of a flip-chip light emitting chip of the present invention. 
           [0011]      FIG. 2  is a cross-sectional view of the circuit board of the flip-chip light emitting chip in  FIG. 1 . 
           [0012]      FIG. 3  is a diagram showing a light emitting module according to a first embodiment of the present invention. 
           [0013]      FIG. 4  is a diagram showing a light emitting module according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a diagram showing a circuit board of a flip-chip light emitting chip of the present invention.  FIG. 2  is cross-sectional view of the circuit board of the flip-chip light emitting chip in  FIG. 1 . As shown in figures, the circuit board  100  of the flip-chip light emitting chip comprises a metal substrate  110 , a first metal electrode  120 , a first insulation layer  130 , a second metal electrode  140 , a second insulation layer  150  and a solder resist layer  160 . The metal substrate  110  has a first surface  170 , and a second surface  180  opposite to the first surface  170 . The first surface  170  comprises a first electrode area  172 , a second electrode area  174  and a heat conduction area  176 . The first electrode area  172  and the second electrode area  174  can be recessed areas formed by etching the first surface, but the present invention is not limited thereto. The first metal electrode  120  is formed on the first electrode area  172 . The first insulation layer  130  is formed between the first metal electrode  120  and the metal substrate  110 , in order to prevent conduction between the first metal electrode  120  and the metal substrate  110 . The second metal electrode  140  is formed on the second electrode area  174 . The second insulation layer  150  is formed between the second metal electrode  140  and the metal substrate  110 , in order to prevent conduction between the second metal electrode  140  and the metal substrate  110 . Due to the arrangement of the first insulation layer  130  and the second insulation layer  150 , the heat conduction area  176  is not electrically connected to the first metal electrode  120  and the second metal electrode  140 . The solder resist layer  160  is formed to cover the first surface  170  of the metal substrate  110 . The solder resist layer  160  can prevent solder from flowing around, and has an insulation function. The heat conduction area  176  is exposed from the solder resist layer  160 . 
         [0015]    In addition, the circuit board  100  of the present invention can further comprise a first power electrode  192  and a second power electrode  194 . The first power electrode  192  can be electrically connected to the first metal electrode  120 , and is configured to receive a first voltage V 1  (such as a positive voltage). The second power electrode  194  can be electrically connected to the second metal electrode  140 , and is configured to receive a second voltage V 2  (such as a ground voltage) different from the first voltage V 1 . As such, the first metal electrode  120  and the second metal electrode  140  can respectively provide the first voltage V 1  and the second voltage V 2  to a flip-chip light emitting chip, for driving the flip-chip light emitting chip to emit light. Moreover, the circuit board  100  of the present invention can further comprise a first anti-oxidative metal layer  122  formed on the first metal electrode  120 , and a second anti-oxidative metal layer  142  formed on the second metal electrode  140 . The first anti-oxidative metal layer  122  and the second anti-oxidative metal layer  142  can be made of gold or silver, in order to prevent the first metal electrode  120  and the second metal electrode  140  from being oxidized. 
         [0016]    On the other hand, the circuit board of the present invention can comprise a plurality of first metal electrodes  120 , second metal electrodes  140 , and heat conduction areas  176 . The plurality of first metal electrodes  120 , second metal electrodes  140 , and heat conduction areas  176  can be evenly distributed on the circuit board in a circular or array form. As such, when the circuit board of the present invention provides power to a plurality of flip-chip light emitting chips for driving the plurality of flip-chip light emitting chips to emit light, the circuit board of the present invention can rapidly and uniformly dissipate heat of the plurality of flip-chip light emitting chips. Moreover, when the circuit board of the present invention comprises the plurality of first metal electrodes  120 , second metal electrodes  140 , and heat conduction areas  176 , electrical connections (such as serial connection or parallel connection) among the first metal electrodes  120 , the second metal electrodes  140 , the first power electrode  192 , and the second power electrode  194  can vary according to design requirements. 
         [0017]    Please refer to  FIG. 3 .  FIG. 3  is a diagram showing a light emitting module according to a first embodiment of the present invention. As shown in  FIG. 3 , a flip-chip light emitting chip  200  of the present invention can be arranged on the circuit board  100 , so as to form a light emitting module  10 . The circuit board  100  in  FIG. 3  is identical to the circuit board  100  in  FIG. 2 . Thus no further illustration for the circuit board is provided. The flip-chip light emitting chip  200  comprises a first electrode  210  and a second electrode  220 . The first metal electrode  120  of the circuit board  100  can be electrically connected to the first electrode  210  of the flip-chip light emitting chip  200  via solder paste  202 , for providing the first voltage V 1  to the first electrode  210  of the flip-chip light emitting chip  200 . The second metal electrode  140  of the circuit board  100  can be electrically connected to the second electrode  220  of the flip-chip light emitting chip  200  via solder paste  202  as well, for providing the second voltage V 2  to the second electrode  220  of the flip-chip light emitting chip  200 . In addition, the heat conduction area  176  can be connected to the flip-chip light emitting chip  200  through a heat dissipation material  204  (such as solder paste or heat dissipation paste) . In other embodiments of the present invention, the heat conduction area  176  can be directly connected to the flip-chip light emitting chip  200  as well. 
         [0018]    According to the above arrangement, heat generated by the flip-chip light emitting chip  200  when emitting light can be rapidly guided to the metal substrate  110  by the heat conduction area  176 , and the heat can be further dissipated by the metal substrate  110 . In one embodiment of the present invention, the metal substrate  110  can be a copper substrate. Since thermal conductivity of copper is higher than thermal conductivity of aluminum oxide, the circuit board  100  of the present invention can improve heat dissipation efficiency. Moreover, the flip-chip light emitting chip  200  can further comprise a heat dissipation metal sheet  230  without being electrically connected to the first electrode  210  and the second electrode  220 . The heat conduction area  176  can be connected to the heat dissipation metal sheet  230  of the flip-chip light emitting chip  200  via the heat dissipation material  204  (or directly connected to the heat dissipation metal sheet  230 ), in order to further improve heat dissipation efficiency. 
         [0019]    On the other hand, the solder resist layer  160  can be made of a light reflective material for reflecting light emitted by the flip-chip light emitting chip  200 , such that light emitting efficiency of the light emitting module  10  can be improved. In one embodiment of the present invention, the flip-chip light emitting chip  200  is a flip-chip light emitting diode chip, but the present invention is not limited thereto. 
         [0020]    Please refer to  FIG. 4 .  FIG. 4  is a diagram showing a light emitting module according to a second embodiment of the present invention. As shown in  FIG. 4 , a light emitting module  20  of the present invention comprises a plurality of flip-chip light emitting chips  200  connected in series on a circuit board  300 , for further forming alight strip. Arrangement of first metal electrodes  120 , second metal electrodes  140 , and heat conduction areas  176  in  FIG. 4  can refer to  FIG. 2 . The flip-chip light emitting chip  200  in  FIG. 4  can be identical to the flip-chip light emitting chip  200  in  FIG. 3 , but the present invention is not limited thereto. In the light emitting module  20  in  FIG. 4 , only two metal electrodes at head and tail ends are respectively coupled to a positive voltage source and a ground voltage source, and middle metal electrodes between the head and tail metal electrodes are shared, in order to drive the flip-chip light emitting chip  200  to emit light. In addition, the heat conduction area  176  can be connected to the flip-chip light emitting chips  200  through the heat dissipation material, or the heat conduction area  176  can be directly connected to the flip-chip light emitting chips  200  as well. 
         [0021]    According to the above arrangement, heat generated by each of the flip-chip light emitting s  200  when emitting light can be rapidly guided to the metal substrate  110  by the corresponding heat conduction area  176 , and the heat can be further dissipated by the metal substrate  110 , so as to improve heat dissipation efficiency. 
         [0022]    In contrast to the prior art, the present invention utilizes the metal substrate as a circuit substrate of the flip-chip light emitting chip, and the metal substrate has an exposed heat conduction area for being indirectly or directly connected to the flip-chip light emitting chip, in order to rapidly guide heat generated by the flip-chip light emitting chip when emitting light to the metal substrate via the heat conduction area, and to further dissipate heat by the metal substrate. Therefore, the circuit board of the flip-chip light emitting chip and the light emitting module of the present invention have better heat dissipation efficiency. 
         [0023]    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.