Abstract:
A flexible printed circuit board (FPC) with an extensible element for liquid crystal display (LCD) module is provided, wherein the extensible element can extend when it is forced. It can be used for different LCD modules to achieve the purpose of simplifying manufacturing process.

Description:
RELATED APPLICATION 
     The present application is based on, claims priority from, Taiwan Application No. 92135532, filed Dec. 16, 2003, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a flexible printed circuit board (FPC) for liquid crystal display (LCD) module, more particularly to a FPC with an extensible element for LCD module. It can be used in the different LCD modules to achieve the purpose of simplifying manufacturing process because the extensible element can be extended when it is applied a force. 
     2. Description of the Prior Art 
     While the science and technology evolved frequently, the display technology and the monitor played a very important role in the development process of the information technology. The portable devices and the display panel incorporated into each electric apparatus or meter, such as the computer, television, mobile phone, BP, and PDA (Personal Digital Assistant), provided large information in our daily life and work. Especially, the LCD (liquid crystal display), which has many advantages such as the low power consumption, low radiation, slim body and better display quality, becomes the main product in the plain display market. 
     As illustrated in  FIG. 1 , a LCD module  10 , which uses the LED (Light Emitting Diode) as the light source, comprises a LCD panel  110 , a LED back light source  120 , a light source connecting FPC (flexible printed circuit board)  130 , a panel connecting FPC  140 , a connector  150  and a PCB (print circuit board)  160 . The light source connecting FPC  130  connects the panel connecting FPC  140  via the connector  150 . However, in consideration of the reliability and the thickness, another method to connect the light source connecting FPC  130  and the panel connecting FPC  140  on the PCB  160  is achieved by a bonding or a soldering process, so as to spare the space for the connector  150 . Please refer to  FIG. 2 , the light source connecting FPC  130  and the panel connecting FPC  140  is mounted on the PCB  160  by the bonding or soldering process. One end of the light source connecting FPC  130  is connected with the back light source  120  and one end of the panel connecting FPC  140  is connected with the LCD panel  110 , and the other ends of the both should be positioned and exactly connected to the PCB  160  by proper tools (not shown in  FIG. 2 ). Then, the light source connecting FPC  130  and the panel connecting FPC  140  are turned over to the reverse side of the LED back light source  120 . Due to the different radiuses of these two FPCs, it is resulted in one protruding length (L′) on the light source connecting FPC  130  other than the panel connecting FPC  140  as illustrated in  FIG. 2 . The circuit on the light source connecting FPC  130  can supply the power to the LED back light source  120 , and the circuit on the panel connecting FPC  140  can transmit signal to control the LCD panel  110 . The above back light source  120  uses the LED as the light source. In fact, the light source for the back light source  120  can also be CCFL (Cold Cathode Fluorescent Lamp) or other similar luminous components. 
     Because a FPC has flexibility and can be curved to a predetermined shape without damaging itself and the circuit thereon, it is used to serves as the light source connecting FPC  130  and the panel connecting FPC  140 . Please refer to  FIG. 3 , three FPCs  310 ,  320 ,  330  in different size but with same circuit layout are shown for being applied to different types of LCD modules  31 ,  32 ,  33 . One end of the FPC  310 / 320 / 330  is connected to a LCD panel  312 / 322 / 332  and the other end of the FPC  310 / 320 / 330  is soldered to a pad  314 / 324 / 334  on the PCB (not shown in  FIG. 3 ). It increases the complication of preparing the material and the space of storing the FPC. Sometimes, the shape of the FPC must be redesign once the position of the pad on the PCB is changed. As illustrated in  FIG. 4 , the shape of a FPC  410  is redesign to the shape of a FPC  420 , there being same circuit layout thereon, in order to be applied to the condition that the position of the pad on the PCB is changed. It not only spends time but also wastes resource to design different FPC shapes for different LCD modules. Therefor, we need a FPC with same circuit layout to be directly applied to different LCD modules. 
     SUMMARY OF THE INVENTION 
     In light of the state of the art described above, it is an object of the present invention to provide a FPC with an extensible element applicable to different LCD modules by extending the FPC to a predetermined length when a force is applied thereon. The FPC is flexible subject to its elasticity by utilizing the extensible element, and it is easy and cheap to implement this invention. 
     It is another object of this invention to provide a FPC with an extensible element that can be applied to different LCD modules, wherein the FPC and the extensible element can be manufactured in a single (all-in-one) process. 
     It is a further object of this invention to provide a FPC with an extensible element that can be applied to different LCD modules. After the FPC is turned over, its length will be shortened, due to the shorter distance and the elastic force between two ends thereof, to reduce the protruding length. 
     In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a flexible printed circuit board (FPC) for liquid crystal display (LCD) module that comprises a first end connected to a LCD panel, a second end connected to a printed circuit board (PCB), a circuit on said FPC connecting electrically said LCD panel and said PCB, and an extensible element that could extend to a first length when a force is applied thereon. 
     Base on the idea described above, said extensible element and said FPC are manufactured in a single (all-in-one) process. 
     Base on the aforementioned idea, said extensible element extends to said first length in a longitudinal direction upon a force applied thereon. 
     Base on the idea described above, said extensible element extends to said first length in a laterally direction upon a force applied thereon. 
     Base on the aforementioned idea, the shape of the cross section view of said extensible element is one selected from the group consisting of embossing, saw-tooth and arc. 
     Base on the idea described above, the shape of the cross section view of said extensible element is composed of at least two ones selected from the group consisting of embossing, saw-tooth and arc. 
     Base on the aforementioned idea, the shape of the cross section view of said extensible element is continuous. 
     Base on the idea described above, the material of said FPC is one selected from the group consisting of Polymer and Polyester. 
     Base on the aforementioned idea, said extensible element is located in a straightaway portion of said FPC so as to extend to said first length in a longitudinal direction. 
     Base on the idea described above, wherein said extensible element is located in an oblique portion of said FPC so as to extend to said first length in a laterally direction. 
     In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a flexible printed circuit board (FPC) with an extensible element that extends to a first length upon a force applied thereon. 
     Base on the idea described above, said extensible element and said FPC are manufactured in a single (all-in-one) process. 
     Base on the aforementioned idea, said extensible element extends to said first length in a longitudinal direction upon a force applied thereon. 
     Base on the idea described above, said extensible element extends to said first length in a laterally direction upon a force applied thereon. 
     Base on the aforementioned idea, the shape of the cross section view of said extensible element is one selected from the group consisting of embossing, saw-tooth and arc. 
     Base on the idea described above, the shape of the cross section view of said extensible element is composed of at least two ones selected from the group consisting of embossing, saw-tooth and arc. 
     Base on the aforementioned idea, the shape of the cross section view of said extensible element is continuous. 
     Base on the idea described above, the material of said FPC is one selected from the group consisting of Polymer and Polyester. 
     Base on the aforementioned idea, said extensible element is located in a straightaway portion of said FPC so as to extend to said first length in a longitudinal direction. 
     Base on the idea described above, wherein said extensible element is located in an oblique portion of said FPC so as to extend to said first length in a laterally direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates a view of a conventional LCD module using a connector to connect the light source connecting FPC and the panel connecting FPC on the PCB; 
         FIG. 2  illustrates a view of a conventional LCD module to connect the light source connecting FPC and the panel connecting FPC on the PCB by a bonding or soldering process; 
         FIG. 3  illustrates three FPCs in different size but with same circuit layout for being applied to different types of LCD modules; 
         FIG. 4  illustrates a shape of the FPC that must be redesigned once for the position of a pad on the PCB is changed; 
         FIGS. 5A and 5B  illustrate a top view and a side view of the FPC according to a first embodiment of this invention respectively, wherein the FPC is not forced yet; 
         FIGS. 6A and 6B  illustrate a top view and a side view of the FPC according to the first embodiment of this invention respectively, wherein the FPC extends to a predetermined length upon a force applied on one end thereof; 
         FIG. 7A  illustrates a top view of the FPC according to a second embodiment of this invention, wherein the FPC is not forced yet; 
         FIG. 7B  illustrates a top view of the FPC according to the second embodiment of this invention, wherein the FPC extends to a predetermined length upon a force applied on one end thereof; 
         FIG. 8A  illustrates a top view of the FPC according to a third embodiment of this invention, wherein the FPC is not forced yet; 
         FIG. 8B  illustrates a top view of the FPC according to the third embodiment of this invention, wherein the FPC extends to a predetermined length upon a force applied on one end thereof; 
         FIG. 9A  illustrates a top view of the FPC according to a fourth embodiment of this invention, wherein the FPC is not adjusted to a predetermined shape yet; 
         FIG. 9B  illustrates a top view of the FPC according to the fourth embodiment of this invention, wherein the FPC is adjusted to the predetermined shape; and 
         FIG. 10  illustrates a cross section view of another extensible element of the FPC according to another embodiment of this invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Some illustrated embodiments of the present invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims. 
     The material of FPC is Polymer or Polyester. Such board has flexibility, and can be curved to a predetermined shape without damaging itself and the circuit thereon. Hence, the basic concept of this invention is to design a portion of the FPC as an extensible element so as to fit different sizes of LCD modules. An FPC  50  according to a first embodiment of this invention is illustrated in  FIGS. 5A and 5B .  FIG. 5A  shows a top view of the FPC  50  and  FIG. 5B  shows a side view of the FPC  50 . An extensible element  52  provided in the FPC  50  according to this embodiment presents a shape of an embossing and/or a saw-tooth. When one end of the FPC  50  is fixed and the other end of the FPC  50  is pulled by a force F 1  (pulling force), the FPC  50  can be extended to a predetermined length without damaging itself and the circuit thereon. The top view and the side view of the FPC  50  under an extended situation are illustrated in  FIGS. 6A and 6B . Its longitudinal length is changed from an unextended length A to an extended length B (B&gt;A). Therefore, the FPC  50  provided with the extensible element  52  can be applied to any the LCD modules that need a longitudinal length between A and B so as to achieve the purpose of applying a single FPC to different LCD modules and the demand of simplifying producing procedures. The extensible element  52  of the PFC  50  can be formed by adding a hot-press step, which does not destroy the circuit layout thereon, in the manufacturing process of the PFC. 
     An FPC  70  according to a second embodiment of this invention is illustrated in  FIGS. 7A and 7B .  FIG. 7A  shows a top view of the FPC  70  that is not forced yet and  FIG. 7B  shows a top view of the FPC  70  that has been forced. An extensible element  72  provided in the FPC  70  is located in an oblique portion of the FPC  70  according to this embodiment of the present invention. When one end of the FPC  70  is fixed and the other end of the FPC  70  is pulled by a force F 2  (pulling force), the FPC  70  can be extended to a predetermined length without damaging itself and the circuit thereon. Its lateral length is changed from an unextended length C to an extended length D (D&gt;C). Therefore, the FPC  70  with extensive element  72  can be applied to any LCD modules that need a lateral length between C and D and thus achieves the purpose of applying a single FPC to different LCD modules and the demand of simplifying producing procedures. 
     Besides, two or more extensible elements can be formed in a single FPC. An FPC  80  according to a third embodiment of this invention is illustrated in  FIGS. 8A and 8B .  FIG. 8A  shows a top view of the FPC  80  that is not forced yet and  FIG. 8B  shows a top view of the FPC  80  that is forced. An extensible element  82  is located in an oblique portion of the FPC  80  and an extensible element  84  is located in a straightaway portion of the FPC  80  according to this embodiment of the present invention. When one end of the FPC  80  is fixed and the other end of the FPC  80  is pulled by a force F 3  (pulling force), the FPC  80  can extends to a predetermined length without damaging itself and the circuit thereon. Not only its longitudinal length is changed from an unextended length E to an extended length F (F&gt;E), but also its lateral length is changed from an unextended length G to an extended length H (H&gt;G). Therefore, the FPC  80  provided with the extensible elements  82 ,  84  can be applied to any LCD modules that need longitudinal length between E and F and lateral length between G and H simultaneously. 
     An FPC  90  according to a fourth embodiment of this invention is illustrated in  FIGS. 9A and 9B .  FIG. 9A  shows a top view of the FPC  90  that is not adjusted to a predetermined shape yet and  FIG. 9B  shows a top view of the FPC  90  that is adjusted to a predetermined shape. Extensible elements  92 ,  94  are located in oblique portions of the FPC  90  according to this embodiment of the present invention. We can adjust two ends of the FPC  90  laterally with a movement of a distance I without damaging itself and the circuit thereon. Therefore, the FPC  90  with the extensible elements  92 ,  94  can be applied to a condition that the position of the pad in the LCD module is changed. 
     Although only the extensible elements having an embossing and/or saw-tooth shape are shown in the above FIGs, any extensible elements with any geometric shapes, which can be flexible in any special directions, fall in the scope of this invention. For example, please refer to  FIG. 10 , an extensible element in an arc shape is also available for this invention. Certainly, subject to the actual need, such shape (e.g. embossing, saw-tooth, and arc) can be designed as several continuous or non-continuous parts or a combination thereof. 
     In accordance with the above concept, we can design the FPC in the shorter length, which can be extended to a predetermined length without damaging itself and the circuit thereon when it is connected on the PCB for bonding or soldering. After the FPC is turned over, the length of such board is shorter than the predetermined length due to the shorter distance and the elastic force between two ends thereof. Because the two ends thereof are fixed, the protruding length of the FPC can be reduced so as to spare the space. 
     This invention provides a FPC with an extensible element that can be applied to different LCD modules without increasing complication of preparing the material and the space of storing the FPC. The FPC is flexible subject to its elasticity by utilizing the extensible element, and it is easy and cheap to implement this invention. Besides, this invention can not only be applied to the LCD module, but also any product which uses a FPC. 
     Although the specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.