Patent Document

BACKGROUND 
     1. Technical Field 
     The present invention relates to printed circuit boards, particularly to a method for manufacturing a rigid-flexible printed circuit board. 
     2. Description of Related Art 
     Rigid-flexible printed circuit boards (R-F PCBs) are widely used in electronic devices. Rigid-flexible printed circuit board has a rigid region and a flexible region. The rigid region is configured for assembling electronic components and maintaining electrical connections among the electronic components. The flexible region is connected to the rigid region and can be bent relative to the rigid region. Thus, a number of electronic components can be assembled on the rigid region of the rigid flexible printed circuit board without occupying a large amount of space. 
     A typical method for manufacturing a rigid-flexible printed circuit board is shown in  FIGS. 7-10 . As shown in  FIG. 7 , a rigid substrate  60  and a flexible substrate  70  are provided. The rigid substrate  60  has a first product region  61  and a first periphery region  62  around the first product region  61 . The flexible region  70  has a second product region  71  corresponding to the first product region  61  and a second periphery region  72  corresponding to the first periphery region  62 . As shown in  FIG. 8 , an opening  63  is formed in a predetermined position of the first product region  61  of the rigid substrate  60 . As shown in  FIG. 9 , the rigid substrate  60  and the flexible substrate  70  are laminated to form a laminated substrate  8  having a predetermined region  81  and a pre-cut region  82 . In detail, the first and second product region  61 ,  71  are laminated to form the predetermined region  81 , the first and second periphery region  62 ,  72  are laminated to form the pre-cut region  82 . In the predetermined region  81 , a portion of the second product region  71  exposed from the opening  63  is adapted to form a flexible region, other portion of the second product region  71  laminated with the first product region  61  is adapted to form a rigid region. As shown in  FIGS. 9-10 , the laminated substrate  8  is cut along the boundary between the predetermined region  81  and the pre-cut region  82 , thus the pre-cut region  82  of the laminated substrate  8  is removed and the predetermined region  81  forms a rigid-flexible printed circuit board  9  which has a flexible region  91  and a rigid region  92 . 
     However, a material property of the rigid region  92  is different to that of the flexible region  91 , when the pre-cut region  82  around the predetermined region  81  is removed simultaneously with a milling cutter, burrs may be formed on the margin of the flexible region  91 . In addition, the thickness of the rigid region  92  is larger than that of the flexible region  91 , thus, when the laminated substrate  8  is cut with the same cutting parameter, the cutting precision of the rigid region  92  and the flexible region  91  is different. Thus, the quality of the rigid-flexible printed circuit board  9  is affected. 
     What is needed, therefore, is a method for manufacturing the rigid-flexible printed circuit board which can overcome the above-described problems. 
     SUMMARY 
     An exemplary embodiment of a method for manufacturing a rigid-flexible printed circuit board includes following steps. Firstly, a flexible substrate is provided. The flexible substrate includes a main portion and a peripheral margin portion. The main portion includes a first laminating section and an exposed section. Secondly, at least one slit is defined in the flexible substrate along at least one first imaginary boundary line between the exposed section and the peripheral margin portion. Thirdly, a rigid substrate is provided. The rigid substrate includes a main portion and a peripheral margin portion. The main portion includes a second laminating section having a similar shape to the first laminating section and an unwanted section having a similar shape to the exposed section. Fourthly, the flexible substrate is laminated to the rigid substrate to obtain a laminated substrate in such a matter that the first and second laminating sections coincide with each other, and the exposed section coincide with the unwanted section. Fifthly, the unwanted section is removed. Sixthly, the laminated substrate is cut along an imaginary boundary line between the second laminating section and the peripheral margin portion to remove the peripheral margin portions of the flexible substrate and the rigid substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic view of a flexible substrate, the flexible substrate including a main portion and a peripheral margin portion, the main portion including a first laminating section and an exposed section. 
         FIG. 2  is similar to  FIG. 1 , but showing two slits defined in the flexible substrate along two first imaginary boundary lines between the exposed section and the peripheral margin portion. 
         FIG. 3  is a schematic view of two rigid substrates each having a main portion and a peripheral margin portion, the main portion including a second laminating section having a similar shape to the first laminating section and an unwanted section having a similar shape to the exposed section. 
         FIG. 4  is a schematic view of a laminated substrate, wherein the rigid substrates are laminated on opposite sides of the flexible substrate. 
         FIG. 5  is similar to  FIG. 4 , but showing unwanted sections are removed. 
         FIG. 6  is a schematic view of a rigid-flexible printed circuit board, which is obtained by cutting the laminated substrate along an imaginary boundary line between the second laminating section and the peripheral margin portion. 
         FIG. 7  is a schematic view of a typical flexible substrate and a rigid substrate. 
         FIG. 8  is a schematic view of the rigid substrate of  FIG. 7  with an opening is formed therein. 
         FIG. 9  is a schematic view of a laminated substrate, which is obtained by laminating the rigid substrate of  FIG. 8  onto the flexible substrate of  FIG. 7 . 
         FIG. 10  is a schematic view of a rigid-flexible printed circuit board, which is obtained by removing the pre-cut region from the laminated substrate shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A method of manufacturing a rigid-flexible printed circuit board according to an embodiment will now be described in detail below with reference to the drawings. 
     The method includes the steps in no particular order of:
         (1) providing a flexible substrate, the flexible substrate including a main portion and a peripheral margin portion, the main portion including a first laminating section and an exposed section;   (2) defining at least one slit in the flexible substrate along at least one first imaginary boundary line between the exposed section and the peripheral margin portion;   (3) providing a rigid substrate, the rigid substrate comprising a main portion and a peripheral margin portion, the main portion including a second laminating section having a similar shape to the first laminating section and an unwanted section having a similar shape to the exposed section;   (4) laminating the flexible substrate to the rigid substrate to obtain a laminated substrate in such a matter that the first and second laminating sections are coincide with each other, and the exposed section is coincide with the unwanted section;   (5) removing the unwanted section; and   (6) cutting the laminated substrate along an imaginary boundary line between the second laminating section and the peripheral margin portion to remove the peripheral margin portions of the flexible substrate and the rigid substrate.       

     Referring to  FIG. 1 , in step (1), a flexible substrate  10  is provided. 
     The flexible substrate  10  is a double-sided flexible copper clad laminate (double-sided FCCL), and includes a first electrically conductive layer  101 , a second electrically conductive layer  102 , and an insulating layer  103  positioned between the first and second electrically conductive layers  101 ,  102 . The flexible substrate  10  defines a main portion  11  and a peripheral margin portion  12 . In the present embodiment, the main portion  11  includes two first laminating sections  111  and an exposed section  112  connected between the two first laminating sections  111 . The first laminating sections  111  and the exposed section  112  are all rectangular shaped. In the illustrated embodiment, a width B 2  of the exposed section  112  is less than a width B 1  of each of the first laminating sections  111 . The first laminating sections  111  and the exposed section  112  each have electrically conductive patterns (not shown) formed therein, which are formed in the first and second electrically conductive layers  101 ,  102 . The first laminating sections  111  and the exposed section  112  cooperatively constitute a printed circuit board. The peripheral margin portion  12  around the main portion  11  is configured for supporting the main portion  11  and will be removed in a later step, so no electrically conductive pattern formed in the peripheral margin portion  12  is needed. 
     It is noted that the flexible substrate  10  also can be a single-sided board or a multilayer board. It is also noted that the number of the first laminating sections  111  of the flexible substrate  10  is not limit to be two, less or more may be defined therein according to practical need. 
     Referring to  FIG. 1  and  FIG. 2 , in step (2), at least one slit  13  is defined in the flexible substrate  10  along at least one first imaginary boundary line  14  between the exposed section  112  and the peripheral margin portion  12 . 
     In the present embodiment, the flexible substrate  10  has two parallel straight first imaginary boundary lines  14  between the exposed section  112  and the peripheral margin portion  12 , thus, the flexible substrate  10  has two parallel straight slits  13  along the two first imaginary boundary lines  14 . The slits  13  can be formed using a laser beam, a blanking die or other means having high cutting accuracy. Each of the slits  13  penetrates through the first electrically conductive layer  101 , the second electrically conductive layer  102  and the first insulating layer  103 . 
     Additionally, if the flexible substrate  10  has only one first laminating section  111  and one exposed section  112 , the first imaginary boundary line  14  defined between the exposed section  122  and the peripheral margin portion  12  would be a continuous polygonal line, and the slit  13  formed in the flexible substrate  10  would be a continuous polygonal shaped groove. 
     Referring to  FIG. 3 , in step (3), two rigid substrates  20  each have a structure (e.g., appearance, electrically conductive patterns or other elements) corresponding to the flexible substrate  10 . 
     In the present embodiment, each of the rigid substrates  20  is a single-sided copper clad laminate (single-sided CCL), and includes a third electrically conductive layer  201  and a second insulating layer  203 . Correspondingly, the rigid substrates  20  each include a main portion  21  and a peripheral margin portion  22 . The main portion  21  includes two second laminating sections  211  having a similar shape to the first laminating sections  111 , and an unwanted section  212  having a similar shape to the exposed section  112 . Electrically conductive patterns can be formed in each of the second laminating sections  211  using the third electrically conductive layer  201 . No electrically conductive patterns formed in the unwanted section  212  and the peripheral margin portion  22  are needed. 
     It is noted that the number of the rigid substrate  20  is not limited to be two, less or more may be provided according to practical need. 
     Referring to  FIG. 4 , in step (4), the flexible substrate  10  is aligned with and laminated onto/sandwiched therebetween the rigid substrates  20  to obtain a laminated substrate  3  in such a matter that the first laminating sections  111  coincide with and are combined with the corresponding second laminating sections  211  to form first sections  311 , the exposed section  112  coincides with and is combined with the unwanted sections  212  to form a second section  312 , and the peripheral margin portions  12 ,  22  coincide with and are combined with each other to form a third section  32 . 
     In the present embodiment, the flexible substrate  10  is disposed and laminated between the two rigid substrates  20 . The first electrically conductive layer  101  is in contact with the second insulating layer  203  of one rigid substrate  20 , the second electrically conductive layer  102  is in contact with the second insulating layer  203  of another rigid substrate  20 . 
     In order to ensure the laminated substrate  3  can be formed into a rigid-flexible printed circuit board, it is noted that if the laminated substrate  3  includes a number of flexible substrates  10  and a number of rigid flexible substrates  20 , the rigid substrates  20  should be arranged at the outermost sides of the laminated substrate  3 . 
     Referring to  FIG. 5 , in step (5), the unwanted sections  212  of the rigid substrates  20  are removed, and the exposed section  112  of the flexible substrate  10  is exposed. Thus, the exposed section  112  can be regarded as a flexible section of the laminated substrate  3 . 
     Referring to  FIG. 5  to  FIG. 6 , in step (6), the laminated substrate  3  is cut along imaginary boundary lines  35  between the first sections  311  and the third section  32  to remove the third section  32 , i.e., peripheral margin portions  12 ,  22  of the flexible substrate  10  and the rigid substrate  20 . The imaginary boundary lines  35  between the first sections  311  and the third section  32  coincide with the borderlines between the second laminating sections  211  and the peripheral margin portion  22  of the rigid substrate  20 , whilst coincide with the borderlines between the first laminating sections  111  and the peripheral margin portion  112  of the flexible substrate  10 . In the present embodiment, the first sections  311  each have an imaginary boundary line  35  between the first section  311  and the third section  32  which is a continuous polygonal line. 
     After the third section  32  of the laminated substrate  3  is removed, a rigid-flexible printed circuit board  4  is obtained. The rigid-flexible printed circuit board  4  has two rigid regions  41  formed from the first sections  311  and one flexible region  42  formed from the exposed section  212 . 
     Furthermore, a plurality of plated through holes (not shown) can be formed in the rigid-flexible printed circuit board  4  to electrically interconnect the first, second and third electrically conductive layers  101 ,  102  and  201 . A coverlayer (not shown) can be formed on the rigid-flexible printed circuit board  4  to protect the conductive patterns formed by the third electrically conductive layers  201 . 
     In the present embodiment, because slits  13  are formed in the flexible substrate  10  before laminating the flexible substrate  10  and the rigid substrates  20 , no burrs are occurred in the flexible region  42 . The appearance of the rigid-flexible printed circuit board  4  can be more precisely controlled than prior art manufacturing methods. Thus, the quality of the rigid-flexible printed circuit board  4  is improved. 
     While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.

Technology Category: 4