Patent Publication Number: US-11050207-B2

Title: Crimping apparatus and system for crimping a flexible printed circuit

Description:
This application claims the benefit of Taiwan Patent Application Serial No. 104111190, filed Apr. 8, 2015, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a technique for electrically connecting two mutually isolated circuit layers to each other and, more particularly, to a crimping apparatus and system and method for electrically connecting two mutually isolated circuit layers formed on a flexible printed circuit to each other through mold pressing. 
     2. Description of the Prior Art 
     Please refer to  FIG. 1A , which illustrates a flexible printed circuit. Generally, the flexible printed circuit  1  comprises an isolation layer  10 , a first circuit layer  11 , and a second circuit layer  12 . The isolation layer  10  is formed from a flexible material and the first and second circuit layers  11  and  12  are respectively formed on upper and bottom surface of the isolation layer  10  whereby the first circuit layer  11  is electrically isolated from the second circuit layer  12 . In one specific application, there is a need for electrically connecting the first circuit layer  11  to the second circuit layer  12  which is implemented by a crimping operation where a stress is acted on the flexible printed circuit  1  such that a portion of metal material of the first circuit layer  11  penetrates throughout the isolation layer  10 , thereby binding to a portion of metal material of the second circuit layer  12  such that the first circuit layer is electrically connected to the second circuit layer  12 . 
     In the conventional art, the crimping process is performed by using a resilient element for storing a resilient force by which the mold pressing can be operated. Thereafter, the resilient force is released for driving a mold to press the flexible printed circuit  1  whereby the first circuit layer  11  formed on the upper surface of the isolation layer  10  is penetrated throughout the isolation layer  10  and electrically connected to the second circuit layer  12  formed on the bottom surface of the isolation layer  10 . In one operation embodiment, such as roll-to-roll manufacturing process, since a plurality of flexible printed circuits are sequentially arranged on the flexible substrate, it is necessary to control a plurality of resilient elements for simultaneously performing the crimping process on the plurality flexible circuits respectively corresponding to the plurality of resilient elements. It is well known that the key for performing crimping process toward a plurality of flexible printed circuits simultaneously is the compression control of the resilient elements, i.e., the height of the pressing mold. However, a compression control for ensuring each resilient element to possess the same compression magnitude at the same time so as to generate the same resilient force for mold pressing is difficult. Accordingly, the consequence of crimping process using resilient elements will induce unstable of electrical conduction between the first and second circuit layers  11  and  12  as well as will cause the difficulties of the same compression magnitude of each resilient element adjusted and tuned by the engineers. 
     It is also known that the crimping quality depends on the stability control of the compressive stress exerted on the flexible printed circuit  1  during crimping process. If the compressive stress is insufficient, such as the illustration shown in  FIG. 1B , the binding force between the first and second circuit layers  11  and  12  is not enough thereby causing circuit layer  11  to break away from the circuit layer  12  in the subsequent manufacturing process and, finally, it will become a defect within the product of the flexible printed circuit after the roll-to-roll manufacturing process. On the contrary, if the compressive stress is excessively applied to the flexible printed circuit, such as the condition shown in  FIG. 1C , a damaged portion  13  is easily generated thereby affecting the binding strength and the electrical conduction between the first and second circuit layers  11  and  12 . In addition, since there a damaged portion  13  on the flexible printed circuit  1 , the upper and bottom molds will mutually contact with each other during the crimping process thereby causing the upper mold to rub against the bottom mold directly so as to reduce the lifetime of the mold. 
     Accordingly, there is a need for a crimping apparatus and system and method that is insensitive to the pressing height of mold press and to the influence of pressed material and is also easily adjusted by the user for electrically connecting two mutually isolated circuit layers to each other thereby solving the conventional problem of the crimping process. 
     SUMMARY OF THE INVENTION 
     The present invention provides a crimping apparatus and system and method for crimping the flexible printed circuit in which a fluid pressure is converted into an action force acting on the pressing mold and the pressing mold is driven to move by a translation module for pressing an object with a constant stress. By means of controlling the fluid pressure, the action force or stress acting on the object during the press procedure can be kept constant thereby generating better quality of crimping result. In addition to preventing the flexible printed circuit from being pressed by excessively applied action force, thereby generating damaged structures, the present invention further prevents friction between the pressing molds, e.g. upper mold and bottom mold, so as to extend the lifetime of pressing mold. 
     In one embodiment, the present invention provides a crimping apparatus, comprising a pressure module, a pressing mold, a translation module, and a pressure control module. The pressure module is configured to provide a pressure through a fluid. The pressing mold is connected to the pressure module for receiving the pressure provided from the pressure module. The translation module is connected to the pressure module for moving the pressure module toward an object whereby the pressing mold is moved to press the object. The pressure control module is configured to control the pressure of the fluid within the pressure module when the pressing mold presses the object so that an action force that the pressing mold acts on the object is kept constant. 
     In another embodiment, the present invention further provides a crimping system, comprising a roll-to-roll conveying module for conveying a flexible substrate roll, at least one pressure control module, and a plurality of crimping apparatus. The roll-to-roll conveying module has a plurality of flexible printed circuits formed thereon, and each flexible printed circuit comprises an isolation layer, a first circuit layer formed on an upper surface of the isolation layer, and a second circuit layer formed on a bottom surface of the isolation layer. Each crimping apparatus is configured to correspond to one of the flexible printed circuit and comprises a pressure module, a pressing mold, and a translation module. The pressure module is configured to provide a pressure through a fluid. The pressing mold is connected to the pressure module for receiving the pressure from the pressure module. The translation module is connected to the pressure module for moving the pressure module toward the corresponding flexible printed circuit so as to move the pressing mold to press the flexible printed circuit thereby causing the first circuit layer to penetrate throughout the isolation layer and connect to the second circuit layer. The at least one pressure control module is configured to control the pressure of the fluid within each the pressure module when the pressing mold presses the flexible printed circuit so that an action force that the pressing mold acts on the flexible printed circuit is kept constant. 
     In a further embodiment, the present invention further provides a method for crimping a flexible printed circuit. At first, at least one flexible printed circuit and a crimping system are provided, wherein each flexible printed circuit comprises an isolation layer, a first circuit layer formed on an upper surface of the isolation layer, and a second circuit layer formed on a bottom surface of the isolation layer and the crimping system comprises at least one crimping apparatus respectively corresponding to the at least one flexible printed circuit, each crimping apparatus further comprising a pressure module, a pressing mold coupled to the pressure module, and a translation module. The crimping system further comprises at least one pressure control module for controlling a fluid flowing into the pressure module. After that, a step of controlling the translation module of each crimping apparatus to move the pressure module thereof toward the corresponding flexible printed circuit is performed thereby leading the pressing mold to press the corresponding flexible printed circuit. Finally, a step of controlling the pressure generated by the fluid inside the pressure module is performed whereby an action force generated by the pressing mold is kept constant during the pressing mold pressing the flexible printed circuit such that the first circuit layer penetrates throughout the isolation layer and electrically connects to the second circuit layer. 
     All of these objectives achieved by the crimping apparatus and system and method for electrically connecting two mutually isolated circuit layers formed on a flexible printed circuit to each other are described below. The accompanying figures are schematic and are not intended to be drawn to scale. In the figures, each identical, or substantially similar component that is illustrated in various figures may be represented by a single numeral or notation (though not always). For purposes of clarity, not every component is labeled in every figure. Nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which: 
         FIG. 1A  illustrates schematic view of a flexible printed circuit; 
         FIGS. 1B and 1C  illustrate a schematic view of defective flexible printed circuit after crimping process; 
         FIG. 2  illustrates one embodiment of the crimping apparatus according to the present invention; 
         FIGS. 3A to 3D  respectively shown flow of a crimping process for the flexible printed circuit according to the present invention; and 
         FIG. 4  illustrates one embodiment of roll-to-roll crimping system according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention disclosed herein is directed to a crimping apparatus and system and method for crimping a flexible printed circuit using the same. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instances, well-known components are not described in detail in order not to unnecessarily obscure the present invention. 
     Please refer to  FIG. 2 , which illustrates one embodiment of the crimping apparatus according to the present invention. In the present embodiment, the crimping apparatus  2  comprising pressure module  20 , pressing mold  21 , translation module  22  and a pressure control module  23 . The pressure module  20  provides pressure through a fluid flowing therein. In one embodiment, the pressure module  20  is a cylinder assembly coupled to the pressing mold  21 . In the present embodiment, the cylinder assembly comprising a pressure cylinder  200  and a piston rod  201 , wherein the pressure cylinder  200  has an accommodating space for allowing the fluid  90  flowing therein. The pressing mold  21  is coupled to the pressure module  20  through the piston rod  201 . A portion of the piston rod  201  is accommodated inside the pressure cylinder  200  and one end of the piston rod  201  is coupled to the pressing mold  21  through a clamping element  202 . The pressure generated by the fluid inside the pressure cylinder  200  is converted into force acting on the piston rod  201  whereby the force is further transmitted to the pressing mold  21 . It is noted that the cylinder assembly is a known art in the related field, which will not be described further hereinafter. 
     In the present invention, the pressing mold  21  further comprises an upper mold  210  and a bottom mold  211 , in which the upper mold  210  is coupled to the piston rod  201  of the pressure module  20  whereas the bottom mold  211  is at a specific distance away from the upper mold  210  for supporting an object  91  corresponding to the upper mold  210 . In one embodiment, the object  91  is a flexible printed circuit. It is noted that there has no specific limitation on the profile of the pressing mold  21  and it is designed according to the user&#39;s need so that the mold is not limited to the present described embodiment having upper mold and bottom mold but instead may be variously embodied according to the actual needs. 
     The pressure control module  23 , in one embodiment, comprises a pressure source  230  and an adjusting device  231 . The pressure source  230  is configured to provide fluid  90 , which can be liquid such as oil liquid, or gas, such as air, which can be properly selected according to the actual need. In the present embodiment, the fluid  90  is a gas. Correspondingly, the pressure cylinder  200  can be a single-acting cylinder or double-acting cylinder, wherein, in the present embodiment, the pressure cylinder  200  is a single-acting cylinder. In addition, the adjusting device  231  respectively coupled to the pressure module  20  and pressure source  230  through pipes  232  for adjusting the fluid amount flowing into the pressure module  20  whereby the force acting on the piston rod  201  converted from the pressure inside the pressure module  20  can be controlled by the adjusting device  231  and transmitted to the pressing mold  21 . It is noted that the pressure range required for generating the action force can be implemented by using, but is not be limited to, pressure gauge or any mechanical or electrical control valves, which can be properly designated by the user according to the actual need. 
     The translation module  22  comprises a base  220  and a driving unit  221 . The base  220  is coupled to the pressure module  20 . In the present embodiment, a clamping element  222  is arranged on the base  220  for claiming and fastening the pressure module  20  on the base  220  through fasteners  223  such as, for example, a combination of bolt and nut. It is noted that the clamping element is not limited to the embodiment shown in the present invention. The one having ordinary skilled in the art can determine the proper means for claming and fastening the pressure module  20  on the base  220  according to the actual need. 
     It is noted that, in the embodiment shown in  FIG. 2 , since the adjusting device  231  is coupled to the pressure module  20  through pipes  232 , which are flexible, the driving unit  221  can move the pressure module  20  upward or downward. Furthermore, in one alternative embodiment, the adjusting device  231  is integrated with the pressure module  20  thereby moving upward or downward with the movement of the pressure module  20 . The connection between the pressure module  20  and the adjusting device  231  can be varied according the actual need so it is not limited by the embodiment shown in  FIG. 2 . It is also noted that, in one embodiment, the arrangement between the pressure control module  23  and pressure module  20  can be one-to-one relationship or, alternatively, one-to-many relationship, i.e., a single pressure control module  23  controlling a plurality of pressure modules  20 . 
     Next, please refer to  FIGS. 2 and 3A to 3D , which illustrates an operation procedure of the present invention. Firstly, as shown in  FIG. 3A , an object is provided. In the present embodiment, the object is a flexible printed circuit  91  having an isolation layer  910 , a first circuit layer  911  and a second circuit layer  912  wherein the first circuit layer  911  is formed on the upper surface of the isolation layer  910  while the second circuit layer  912  is formed on the bottom surface of the isolation layer  910 . The first circuit layer  911  and second circuit layer  912  is formed by metal material with electrically conducting capability, which can be, but is not limited to, alumni, copper, gold, or alloys thereof. Furthermore, in one embodiment, the flexible printed circuit  91  is a radio frequency identification (RFID) device, in which the first circuit layer  911  and the second circuit layer  912  can be, but is not limited to, an antenna circuit or bridge circuit of the RFID, such as a combination of RFID chip and passive components, e.g., capacitor, resistor, inductor, and etc. In the present embodiment, the first circuit layer  911  is the antenna circuit of the RFID while the second circuit layer  912  is the bridge circuit. The material for making the isolation layer  910  can be, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), or polyethylene (PE). In one embodiment, the thickness of the object, i.e., the flexible printed circuit  91 , is less than or equal to 100 μm. The pressure control module  23  controls and adjusts the pressure inside the pressure module  20  simultaneously so that the force transmitted to the pressing mold  21  is kept constant whereby the action force or stress that the pressing mold  21  acts on the flexible printed circuit  91  is kept constant during the crimping process. 
     Next, as shown in  FIG. 3B , the translation module  22  is controlled to drive the pressure module  20  to move toward the flexible printed circuit  91  such that the front part of the pressing mold  21  presses the flexible printed circuit  91 . In the present embodiment, the upper mold  210  continues to press the flexible printed circuit  91  such that the isolation layer  910  is broken by the stress or action force received from the pressing mold while the first circuit layer  911  is deformed to penetrate throughout the isolation layer  910  thereby electrically connecting to the second circuit layer  912 . It is noted that, during the press process, the pressure controlling module  23  detects the fluid pressure inside the pressure module  20  and controls the fluid amount flowing into the pressure module  20  from pressure source  230  thereby keeping the action force acting on the pressing mold  21  constant so as to provide constant pressing stress acting on the flexible printed circuit  91  from the upper mold  210 . After pressing downward on the flexible printed circuit  91  a certain of distance, as shown in  FIG. 3C , the translation module  22  moves the upper mold  210  upward and the flexible printed circuit  91  will become the structure shown in  FIG. 3D . From  FIG. 3D , it is clear that the first circuit layer  911  penetrates throughout the isolation layer  910  and electrically connects to the second circuit layer  912 . 
     Please refer back to  FIG. 2 , it is known that the conventional pressure cylinder  200  is usually utilized to be an actuator for moving the piston rod  201  outward from the cylinder  200  and backward to the cylinder  200  periodically through the filling or releasing of fluid inside the cylinder  200 ; however, differing from the usage of the conventional pressure cylinder, the pressure cylinder  200  actuates the piston rod  201  to fixedly extend at a specific distance without moving the piston rod back and forth. Regarding the control of moving piston rod  201 , it is performed by the control of the translation module  22  to move the pressure module  20  forward (downward) and backward (upward) rather than control the piston rod  201  to move forward from the cylinder  200  or backward to return the pressure cylinder  200 . Since the translation module  22  is utilized to control the movement of the pressing mold  21  acting on the flexible printed circuit  91  and the action force, converted from the pressure and transmitted to the pressing mold  21 , is kept constant by adjusting the fluid pressure inside the pressure module  20  through the pressure control module  23 , the stress or reaction force acting on the object can be maintained constant during the crimping process whereby the unstable stress or reaction force acting on the object during the crimping process can be effectively improved. 
     In another embodiment, the crimping apparatus can be further applied in a roll-to-roll process for forming a crimping system shown in  FIG. 4 . In the present embodiment, the crimping system  3  comprises a roll-to-roll transportation module  30  for transporting a flexible substrate roll  31  on which a plurality of flexible printed circuits  91  are formed. Each flexible printed circuit  91 , as shown in  FIG. 3A , comprises an isolation layer  910  having an upper and bottom surfaces on a first circuit layer  911  and a second circuit layer  912  are respectively formed. In one embodiment, a thickness of each flexible printed circuit  91  is less than or equal to 100 μm. The roll-to-roll transportation module  30  comprises a plurality of rollers  301 ,  302 , and  303  including at least one steering roller and a plurality of driven rollers, wherein a roller  302  carries the flexible substrate roll  31 . One end of the flexible substrate roll  31  is coupled to the roller  303  utilized to receive the flexible substrate roll  31  passing through the plurality of rollers  301 . 
     In the present embodiment, since the surface area of the flexible substrate roll  31  is large, a plurality of crimping apparatuses  2  such as the embodiment shown in  FIG. 2 , for example, can be arranged along the width direction of the flexible substrate roll  31 , each of which is corresponding to a flexible printed circuit  91  formed on the flexible substrate roll  31 . By means of the transportation of the flexible substrate roll  31  through the roll-to-roll transportation module  30  along the X direction, each crimping apparatus  2  performs crimping process toward the flexible printed circuit  91  passing there through, thereby making one circuit layer to penetrate throughout the isolation layer and connecting to the other circuit layer. It is noted that, as shown in  FIGS. 2 and 4 , a pressure control module  23  has one-to-one relationship to pressure module  20  for each crimping apparatus  2 ; alternatively, the pressure control module  23  has one-to-many relationship to the pressure modules  20 , i.e., a single pressure control module for controlling and adjusting the pressure of the pressure module of each crimping apparatus arranged within the crimping system  3 . In addition to the crimping apparatus shown in the  FIG. 4 , it is noted that there can be arranged any necessary processing stage along the roll-to-roll transportation direction X in the crimping system  3 . 
     Accordingly, the crimping apparatus, crimping system and method for crimping the flexible printed circuit in the present invention are capable of providing constant action force or stress that the pressing mold presses on the object during the crimping process whereby one circuit layer is pressed to penetrate throughout the isolation layer and electrically connect to the other circuit layer which is formerly isolated from the pressed circuit layer without generating defects so that not only can the electrical connection between two circuit layers be greatly improved but also the pressing mold can be protected from being rubbed thereby increasing the usage lifetime of the pressing mold. 
     While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.