Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a complex circuit board and a fabrication method thereof, particularly to a technology of combining circuit boards using corresponding fixing structures thereof to form the complex circuit board without extra attachment units. 
     2. Description of the Prior Art 
     Various display electronic products have been developed in recent years. Among various types of flat displays, liquid crystal displays (LCD) have become the mainstream products, for example, LCD TVs and computer LCD monitors. 
       FIG. 1  is a schematic view of a conventional liquid crystal apparatus. A display apparatus  1  has a display panel  100  and a backlight module  200 . The backlight module  200  has a light-emitting device  210 . The light-emitting device  210  supplies backlight for the display panel  100 . Therefore the display apparatus  1  displays full color image for viewers. 
       FIG. 2A  is a schematic view of the light-emitting device  210 . The light-emitting device  210  has light sources  212  and circuit boards  214 . The circuit boards  214  transmit signals to the light sources  212  to control the power or the brightness of light sources  212 . Light emitting diodes (LEDs) could be used as the light sources  212 . The circuit boards  214  include a printed circuit board assembly (PCBA)  216  and a flexible printed circuit (FPC)  218  combined with each other. The printed circuit board assembly  216  has a supporting surface  215  and the light sources  212  are disposed on the supporting surface  215 . The printed circuit board assembly  216  has a combining section  217  for attaching a bend portion of the flexible printed circuit  218  onto the printed circuit board assembly  216  and electrically transmitting driving signals of light sources. 
       FIG. 2B  illustrates a combining method for the circuit boards  214  of the conventional display apparatus  1 . The flexible printed circuit  218  is bent and attached onto the printed circuit board assembly  216 , wherein attachment units  219  (e.g. tapes) are attached onto the combining section  217 , thereby strengthening the pull strength of flexible printed circuit  218  and reducing the possibility of poor signal transmission induced by the stress acting on the combining section  217 . However, the above combining method needs additional processes for attaching the attachment units  219  to strengthen the combining portion  217 . Furthermore, the ability of the attachment units  219  in strengthening the pull strength of the combining section  217  is limited. For large-size display application, the combining strength of circuit boards  214  should be further improved. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a complex circuit board which combines a printed circuit board assembly and a flexible printed circuit. 
     It is another object of the present invention to provide a complex circuit board to improve the pull strength of a flexible printed circuit. 
     It is a further object of the present invention to provide a complex circuit board without extra attachment units on the combining sections of circuit boards. 
     It is yet another object of the invention to provide a display apparatus, including a display panel and a backlight module. A light-emitting device of the backlight module supplies backlight for the display panel. The light-emitting device has light sources and circuit boards. The circuit boards transmit control signals to the light sources to control power and brightness of the light sources. The complex circuit board includes a printed circuit board assembly (PCBA) and a flexible printed circuit (FPC). 
     The printed circuit board assembly has a supporting section and a connecting section. The supporting section has a supporting surface for supporting the light sources. The connection section extends from the one side of the supporting section and has a first surface extending from the supporting surface, a first side surface adjacent to the first surface, and a first fixing portion disposed on the first side surface. The flexible printed circuit has a contacting section disposed parallel to the connecting section. The contacting section has a first fixing hole and the first fixing portion is inserted into the first fixing hole to couple the flexible printed circuit with the printed circuit board assembly. 
     Furthermore, the flexible printed circuit has a first bend portion and a second bend portion. The first bend portion and the second bend portion are located on two opposite sides of the contacting section. The flexible printed circuit changes the extending direction at the first bend portion and has an angle with the contacting section, wherein the first fixing hole is located on the first bend portion. 
     The printed circuit board assembly further has a first connecting unit disposed on the connecting section. The flexible printed circuit has a second connecting unit disposed on the contacting section. The second connecting unit is electrically connected to the first connecting unit to transmit control signals of the light sources. 
     It is another object of the present invention to provide a fabrication method of a complex circuit board. The method includes forming a first fixing portion on a printed circuit board assembly and a first fixing hole on a flexible printed circuit. The first fixing hole is corresponding to the first fixing unit and the first fixing unit is inserted into the first fixing hole to couple the flexible printed circuit with the printed circuit board assembly to accomplish the fixing process of the circuit boards. 
     By the above complex circuit board and the fabrication method, the strength of fixing the printed circuit board assembly and the flexible printed circuit is improved to effectively increase the pull strength therebetween. Moreover, without using extra attachment units (e.g. tapes), the assembly procedure is simplified. Consequently, the throughput is increased and the cost is reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a conventional display apparatus. 
         FIG. 2A  is a schematic view of a conventional light-emitting module. 
         FIG. 2B  is a schematic view showing the assembly of the conventional light-emitting module. 
         FIG. 3A  is a schematic view of the light-emitting module of the present invention. 
         FIG. 3B  is a schematic view showing the structure of the complex circuit board of the present invention. 
         FIG. 3C  is a combined view of the complex circuit board of the present invention. 
         FIG. 4A  is another embodiment of the light-emitting module. 
         FIG. 4B  is another embodiment of the complex circuit board. 
         FIG. 4C  is a combined view of another embodiment of the complex circuit board. 
         FIGS. 5A-5C  are embodiments of fixing structures. 
         FIG. 6  is a flow chart of the fabrication method for the complex circuit board of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a complex circuit board and a fabrication method thereof by using mechanical-combining technique to effectively increase the pull strength of the complex circuit board and strengthen the connection of a printed circuit board assembly and a flexible printed circuit. Furthermore, the elimination of the conventional step of attaching attachment units simplifies the assembly procedure and reduces the cost of attachment units. The complex circuit board of the present invention and a fabrication method thereof can achieve the advantages of improving the strength of the complex circuit board and reducing the product cost. 
     As shown in  FIG. 3A , the complex circuit board includes a printed circuit board assembly  300  and a flexible printed circuit  400 . The printed circuit board assembly  300  has a supporting section  310  and a connecting section  320 . The supporting section  310  supports several light sources  212 . Specifically, the supporting section  310  has a supporting surface  312  and the light sources  212  are disposed on the supporting surface  312 . The light sources  212  are preferably light emitting diodes (LEDs) for supplying illumination. The connecting section  320  extends from one end of the supporting section  310  and is provided for fixing and electrically connecting with the flexible printed circuit  400 . The flexible printed circuit  400  is preferably formed by cutting from a flexible circuit board and has a contacting section  420 . The contacting section  420  of the flexible printed circuit  400  is disposed corresponding to the connecting section  320  of the printed circuit board assembly and electrically connected thereto to transmit control signals of the light sources  212 . 
       FIG. 3B  is a partially enlarged view of the complex circuit board. The connecting section  320  of the printed circuit board assembly  300  extends form the end of supporting section  310 . The connecting section  320  has a first surface  322  extending from the supporting surface  312  and a first side surface  324  adjacent to the first surface  322 . A first fixing portion  325  is disposed on the first side surface  324 . In the present embodiment, the first fixing portion  325  is a protrusion on the first side surface  324 . The connecting section  320  further includes a second surface  328  corresponding or opposite to the first surface  322 , preferably parallel to the first surface  322 . The first side surface  324  is situated between the first surface  322  and the second surface  328  and approximately perpendicular to the first surface  322  and the second surface  328 . A first connecting unit  327  is disposed on the connecting section  320  and correspondingly adjacent to the first fixing portion  325 . In the present embodiment, the first connecting unit  327  is disposed on the second surface  328  and can be, for example, electrical conductive patterns or contact pads to transmit control signals of the light sources  212 . The material of the first connecting unit  327  is preferably copper, aluminum or alloys thereof. 
     The contacting section  420  of the flexible printed circuit  400  has a second connecting unit  427 . The contacting section  420  has a third surface  422  and a fourth surface  424  opposite to the third surface  422 , wherein the second connecting unit  427  can be disposed on the third surface  422  or the fourth surface  424 . In the present embodiment, the second connecting unit  427  is disposed on the third surface  422 . The second connecting unit  427  can be electrical conductive patterns or contact pads and the material can be copper, aluminum or alloys thereof. When the third surface  422  of the contacting section  420  and the second surface  328  of the connecting section  320  are correspondingly disposed, the second connecting unit  427  is electrically connected to the first connecting unit  327  of the printed circuit board assembly  300 . For example, the second connecting unit  427  can be soldered to the first connecting unit  327  using a hot bar process or electrically connected to the first connecting unit  327  by a thermal press process. A first fixing hole  425  is located between the second connecting unit  427  and the end of flexible printed circuit  400 . The first fixing portion  325  is inserted into the first fixing hole  425  to couple the printed circuit board assembly  300  and the flexible printed circuit  400 . After the printed circuit board assembly  300  and the flexible printed circuit  400  are combined, the extending directions of the circuit boards  300 ,  400  are approximately perpendicular to each other. 
     Referring to  FIG. 3C , the first fixing portion  325  is inserted into the first fixing hole  425  to assemble the printed circuit board assembly  300  with the flexible printed circuit  400  and electrically connect the first connecting unit  327  and the second connecting unit  427 . 
     As shown in the  FIG. 3B  and  FIG. 3C , the flexible printed circuit  400  is bent to form a first bend portion  410  and a second bend portion  430 . The extending direction of the flexible printed circuit  400  is changed via the first bend portion  410  and the second bend portion  430  from the contacting section  420 . The first bend portion  410  and the second bend portion  430  respectively have a bending angle. For example, the bending angle is 90 degrees or other specific degrees modulated according to the product design. In other words, the first bend portion  410  and the second bend portion  430  are located on two opposite sides of the contacting section  420 . 
     Furthermore, as shown in  FIG. 3B  and  FIG. 3C , a first indentation  326  is preferably formed on the connecting section  320  and disposed on at least one side of the first fixing portion  325 . In the present embodiment, the first indentations  326  are disposed on two opposite sides of the first fixing portion  325 . The first indentation  326  at least partially accommodates the first bend portion  410  of the flexible printed circuit  400 . When combining the complex circuit board, the strength of the combining section  330  is improved and the smoothness of the complex circuit board is promoted. Similarly, another indentation can be disposed on the other side surface opposite to the first fixing portion  325  to at least partially accommodate the second bend portion  430  of the flexible printed circuit  400 . 
     By means of the above structural design, the pull strength of the complex circuit board is structurally enhanced without using extra attachment units on the combining portion  330  and the assembly of the complex circuit board is easily accomplished. 
     As shown in  FIG. 4A  to  FIG. 4C , the present invention provides another embodiment, wherein the elements with same reference numbers are the same as those disclosed in the previous embodiment. As shown in  FIG. 4A , the complex circuit board includes a printed circuit board assembly  300  and a flexible printed circuit  400 . The printed circuit board assembly  300  has a supporting section  310  and a connecting section  320 . The supporting section  310  supports several light sources  212 . Specifically, the supporting section  310  has a supporting surface  312  and the light sources  212  are disposed on the supporting surface  312 . The light sources  212  preferably include light emitting diodes (LEDs) for supplying illumination. The connecting section  320  extends from one end of the supporting section  310  and is provided for fixing and electrically connecting with the flexible printed circuit  400 . The flexible printed circuit  400  is preferably formed by cutting from a flexible circuit board and has a contacting section  420 . The contacting section  420  of the flexible printed circuit  400  is disposed correspondingly to and electrically connected with the connecting section  320  of the printed circuit board assembly  300  to transmit control signals of the light sources  212 . 
       FIG. 4B  is a partially enlarged view of the complex circuit board. The connecting section  320  of the printed circuit board assembly  300  extends form the end of the supporting section  310 . The connecting section  320  has a first surface  322  extending from the supporting surface  312  and a first side surface  324  adjacent to the first surface  322 . A first fixing portion  325  is disposed on the first side surface  324 . In the present embodiment, the first fixing portion  325  is a protrusion on the first side surface  324 . A first connecting unit  327  is disposed on the first surface  322  of the connecting section  320  and adjacent to the first fixing portion  325 . In the present embodiment, the second side surface  329  is parallel to the first side surface  324 . A second fixing portion  321  is disposed on the second side surface  329  and is preferably a protrusion on the second side surface  329 . In the present embodiment, the protrusions of first fixing portion  325  and second fixing portion  321  are symmetrically located on two opposite sides of the first connecting unit  327 . The protrusion of first fixing portion  325  or second fixing portion  321  can be aligned to the first connecting unit  327 , but not limited thereto. That is, the protrusion of first fixing portion  325  or second fixing portion  321  can be not aligned to the first connecting unit  327 . The first connecting unit  327  is electrical conductive patterns or contact pads for transmitting control signals of the light sources  212 . The most common material of the first connecting unit  327  is copper, aluminum or alloys thereof. 
     The contacting section  420  of the flexible printed circuit  400  has a second connecting unit  427 . The second connecting unit  427  is disposed on the fourth surface  424 . The second connecting unit  427  can be electrical conductive patterns or contact pads and the material is copper, aluminum or alloys thereof. When the fourth surface  424  of the contacting section  420  and the first surface  322  of the connecting section  320  are correspondingly disposed, the second connecting unit  427  is electrically connected to the first connecting unit  327  of the printed circuit board assembly  300 . For example, the second connecting unit  427  can be soldered to the first connecting unit  327  using a hot bar process or electrically connected to the first connecting unit  327  by a thermal press process. The contacting section  420  of the flexible printed circuit  400  further includes a first hook  401  and a second hook  402 . A first fixing hole  425  and a second fixing hole  421  are disposed on the first hook  401  and the second hook  402 , respectively. The first hook  401  and the second hook  402  are bent to form a first bend portion  410  and a second bend portion  430 . The first fixing portion  325  is inserted into the first fixing hole  425  and the second fixing portion  321  is inserted into the second fixing hole  421  to couple and fix the printed circuit board assembly  300  and the flexible printed circuit  400 . After the printed circuit board assembly  300  and the flexible printed circuit  400  are combined, the extending directions ( 300   a ,  400   a , see  FIG. 4B ) of the circuit boards  300 ,  400  are approximately parallel. 
     Finally, the flexible printed circuit  400  is bent to form a third bend portion  440 . The extending direction of the flexible printed circuit  400  is changed via the third bend portion  440 . The third bend portion  440  has a bending angle. The bending angle can be a specific degree modulated according to the product design. 
     In the present embodiment, the first bend portion  410  and the second bend portion  430  of the contacting section  420  are symmetrically disposed on two opposite sides of the second connecting unit  427 . The first hook  401  or the second hook  402  can be aligned or not aligned with the second connecting unit  427 . 
     A first indentation  326  and a second indentation  323  are disposed on one side of the first fixing portion  325  and the second fixing portion  321 , respectively. The first indentation  326  is disposed between the first fixing portion  325  and the supporting section  310 . The second indentation  323  is disposed between the second fixing portion  321  and the supporting section  310 . The first indentation  326  and the second indentation  323  at least partially accommodate the first bend portion  410  and the second bend portion  430  of the flexible printed circuit  400 , respectively. Therefore, the strength of the complex circuit board is improved due to the structural design. 
     Moreover, as shown in  FIG. 5A  to  FIG. 5C , to enhance the strength of the combining section  330 , the first fixing portion  325  and the second fixing portion  321  can be rectangle, wedge, or arc shaped protrusions, so that the flexible printed circuit  400  and the printed circuit board assembly  300  are prevented from being detached from each other. 
     The present invention also provides a fabrication method of the complex circuit board. As shown in  FIG. 6 , the step S 10  is forming a first fixing portion  325  on a connecting section  320  of a printed circuit board assembly  300 . In another embodiment, a second fixing portion  321  is further formed on the printed circuit board assembly  300 . The step S 10  further includes forming a first indentation  326  and a second indentation  323  on one side of the first fixing portion  325  and the second fixing portion  321 , respectively. 
     The step S 20  includes forming a first fixing hole  425  on a contacting section  420  of the flexible printed circuit  400 . The first fixing hole  425  corresponds to the first fixing portion  325 . In another embodiment, a second fixing hole  421  is formed on the flexible printed circuit  400  and the second fixing hole  421  is disposed corresponding to the second fixing portion  321 . 
     The step S 30  includes inserting the first fixing portion  325  into the first fixing hole  425  and inserting the second fixing portion  321  into the second fixing hole  421  to combine the flexible printed circuit  400  and the printed circuit board assembly  300 . 
     The step S 40  includes bending the flexible printed circuit  400  at the first fixing hole  425  to form the first bend portion  410 . In another embodiment, the first hook  401  with the first fixing hole  425  and the second hook  402  with the second fixing hole  421  are bent to form the first bend portion  410  and the second bend portion  430  of the flexible printed circuit  400 . The first bend portion  410  is parallel to the second bend portion  430 . The first indentation  326  and the second indentation  323  at least partially accommodate the first bend portion  410  and the second bend portion  430  of the flexible printed circuit  400 , respectively. 
     The step S 50  includes bending the flexible printed circuit  400  from another side of the contacting section  420  to form a third bend portion  440 . In another words, before the third bend portion  440  is formed, the bending directions of the first hook  401  and the second hook  402  are respectively perpendicular to the extending direction of the flexible printed circuit  400 . 
     The step S 60  includes electrically connecting the flexible printed circuit  400  and the printed circuit board assembly  300 . The circuit boards  300 ,  400  are soldered using the hot bar process. The flexible printed circuit  400  and the printed circuit board assembly  300  are combined and electrically connected via the first connecting unit  427  and the second connecting unit  327 . 
     Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.

Technology Category: 4