Patent Publication Number: US-2022240372-A1

Title: Circuit Board for High Frequency Transmission and Shielding Method

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to Chinese patent application No. 201910611393.2, filed to the China National Intellectual Property Administration on Jul. 8, 2019, the disclosure of which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure belongs to the field of electronic communication, for example, relates to a circuit board for high frequency transmission and a shielding method. 
     BACKGROUND 
     With the development of electronic and communication products towards multi-function and complexity, a structure of a circuit board is required to be lighter, thinner, shorter, and smaller. Stronger functions and high speed signal transmission are further required. In order to satisfy the above requirements of the circuit board, working frequencies are getting higher and higher. However, with the increasing of the working frequencies, leaky waves may occur on two sides of the circuit board, causing a signal to not be completely transmitted, so that the integrity of signal transmission is strongly influenced, resulting in signal distortion. 
     Summary 
     Some embodiments of the present disclosure provide a circuit board for high frequency transmission and a shielding method. Thus, leaky waves at a lateral side of a circuit board body are effectively avoided, the integrity of signal transmission is guaranteed, and thin structure is realized. 
     A technical solution includes as follows. 
     In some embodiments, a circuit board for high frequency transmission includes a first shielding film, a second shielding film, and a circuit board body. The circuit board body includes a first surface and a second surface that are arranged opposite to each other. The first shielding film covers the first surface, and the second shielding film covers the second surface. The circuit board body is provided with a wire region. The first shielding film and the second shielding film are in electrical connection at a lateral side of the wire region. 
     A junction of the first shielding film and the second shielding film may not be located in the center of a cross section of the circuit board body. The connection of the first shielding film and the second shielding film at the lateral side of the wire region includes the following. The first shielding film crosses an edge of the first surface, and the second shielding film crosses an edge of the second surface, so as to make the first shielding film to be connected with the second shielding film; or the first shielding film is connected with the second shielding film after crossing the edge of the first surface and the edge of the second surface; or the second shielding film is connected with the second shielding film after crossing the edge of the second surface and the edge of the first surface. As long as the first shielding film and the second shielding film are connected to wrap the lateral side of the circuit board body so as to avoid leaky waves. Edges of the first surface and the second surface include a boundary of the entire wire region and an edge of an opening on the circuit board body. The connection of the first shielding film and the second shielding film at the lateral side of the wire region includes external connection protruding out of the boundary of the entire wire region, or internal connection protruding out of the edge of the opening on the circuit board body. 
     The operation that the first shielding film covers the first surface of the circuit board body includes as follows. The first shielding film covers a part of the first surface; or the first shielding film covers the entire first surface; or the first shielding film not only covers the entire first surface but also protrudes out of the boundary of the first surface; or the first shielding film covers a part of the first surface, and a part of the first shielding film protrudes out of the boundary of the first surface. The operation that the second shielding film covers the second surface of the circuit board body includes as follows. The second shielding film covers a part of the second surface; or the second shielding film covers the entire second surface; or the second shielding film not only covers the entire second surface but also protrudes out of the boundary of the second surface; or the second shielding film covers a part of the second surface, and a part of the second shielding film protrudes out of the boundary of the second surface. 
     In some embodiments, the circuit board body further includes a transition portion. An end of the transition portion is connected to the wire region, and another end of the transition portion is a free end. A thickness of at least one part of the transition portion is less than a thickness of the wire region. 
     In some embodiments, the transition portion is provided with a smooth transition surface. 
     In some embodiments, the first shielding film is connected with the second shielding film in a manner of bonding. 
     In some embodiments, the circuit board body further includes a blank region. The blank region is provided with an opening. The opening communicates the first surface and the second surface. The first shielding film is electrically connected with the second shielding film through the opening. 
     In some embodiments, a junction of the first shielding film and the second shielding film is accommodated in the opening. 
     In some embodiments, the first shielding film covers surfaces of the wire region and the blank region, and is connected with the second shielding film at the opening; or/and, the second shielding film covers the surfaces of the wire region and the blank region, and is connected to the first shielding film at the opening. In some embodiments, the circuit board body is provided with more than two wire regions. The blank region is disposed between the wire regions, and is provided with the opening. The first shielding film and the second shielding film cover the more than two wire regions. The first shielding film is connected with the second shielding film through the opening. 
     In some embodiments, a circuit board for high frequency transmission includes a circuit board body and a shielding film. The circuit board body includes a main wire layer and a conductor layer. The main wire layer is provided with a third surface and a fourth surface that are arranged opposite to each other. The conductor layer is disposed on the fourth surface. The main wire layer is provided with an opening. The third surface communicates with the conductor layer through the opening. The shielding film covers the third surface, and extends into the opening to be electrically connected with the conductor layer. 
     In some embodiments, a shielding method for a circuit board for high frequency transmission includes: covering a first shielding film on a first surface of a circuit board body; covering a second shielding film on a second surface of the circuit board body; and electrically connecting the first shielding film and the second shielding film at a lateral side of a wire region of the circuit board body. The operation of covering the first shielding film on the first surface of the circuit board body and the operation of covering the second shielding film on the second surface of the circuit board body are in a random order. 
     In some embodiments, a blank region of the circuit board body is provided with an opening configured to communicating the first surface and the second surface. The first shielding film is connected with the second shielding film through the opening. 
     In some embodiments, before the first shielding film is connected with the second shielding film, the opening is processed in the blank region. 
     In some embodiments, the first shielding film protrudes out of an edge of the circuit board body. The second shielding film protrudes out of the edge of the circuit board body. The first shielding film and the second shielding film are in electrical connection at a lateral side of the circuit board body. 
     In some embodiments, the first shielding film is connected with the second shielding film through bonding. 
     The beneficial effects of the present disclosure are as follows. 
     1. The first shielding film and the second shielding film are in electrical connection at a lateral side of the wire region of the circuit board body. In this way, a barrier is formed at the lateral side of the wire region, so as to avoid leaky waves at the lateral side of the wire region, thereby guaranteeing the integrity of signal transmission. Through a manner that the first shielding film and the second shielding film are in connection at the lateral side of the wire region after wrapping the circuit board body, convenient manufacturing is achieved. 
     2. The first shielding film and the second shielding film are viscous. “The operation of bonding the first shielding film and the second shielding film, the operation of bonding the first shielding film to the first surface, and the operation of bonding the second shielding film to the second surface” are simultaneously performed, which all belong to a “bonding” process (that is, including normal temperature and pressure bonding, heating bonding, or pressure bonding). The process is simple. The first shielding film and the second shielding film may be directly bonded without other operation after the first shielding film and the second shielding film are bonded on the circuit board body. Therefore, simple process and high production efficiency are realized. 
     3. All openings may be simultaneously processed. The first shielding film and the second shielding film are covered. Then, the first shielding film and the second shielding film in the openings are pressed (that is, pressure bonding). In this way, mass production and high efficiency are achieved. In addition, the circuit board body is clamped between the pressed first shielding film and second shielding film, so that the first shielding film and the second shielding film are fixed on the circuit board body. On the other hand, through the manner of viscous pressing, convenient production and high efficiency are achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view from a front view of an unshielded circuit board body according to a first embodiment of the present disclosure. 
         FIG. 2  is a top view of the circuit board body according to the first embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram I of steps of a shielding method for a circuit board for high frequency transmission according to a first embodiment of the present disclosure. 
         FIG. 4  is a schematic diagram II of steps of the shielding method for the circuit board for high frequency transmission according to the first embodiment of the present disclosure. 
         FIG. 5  is a top view of  FIG. 4 . 
         FIG. 6  is a schematic diagram III of steps of the shielding method for the circuit board for high frequency transmission according to the first embodiment of the present disclosure. 
         FIG. 7  is a schematic diagram IV of steps of the shielding method for the circuit board for high frequency transmission according to the first embodiment of the present disclosure. 
         FIG. 7-1  is a schematic structural diagram of a circuit board body being a multilayer board according to the first embodiment of the present disclosure. 
         FIG. 7-2  is a schematic structural diagram of a circuit board body being a single sided board according to the first embodiment of the present disclosure. 
         FIG. 7-3  is a schematic structural diagram of a circuit board body being a double sided board according to the first embodiment of the present disclosure. 
         FIG. 8  is a top view of  FIG. 7 . 
         FIG. 9  is a cross-sectional view from a front view of a circuit board body according to a second embodiment of the present disclosure. 
         FIG. 10-1  is a schematic diagram I of steps of a shielding method for a circuit board for high frequency transmission according to a third embodiment of the present disclosure. 
         FIG. 10-2  is a schematic structural diagram of a modification of  FIG. 10-1 . 
         FIG. 11  is a schematic diagram II of steps of the shielding method for the circuit board for high frequency transmission according to the third embodiment of the present disclosure. 
         FIG. 12  is a schematic diagram III of steps of the shielding method for the circuit board for high frequency transmission according to the third embodiment of the present disclosure. 
         FIG. 13  is a schematic diagram I of steps of a shielding method for a circuit board for high frequency transmission according to a fourth embodiment of the present disclosure. 
         FIG. 14  is a schematic diagram II of steps of the shielding method for the circuit board for high frequency transmission according to the fourth embodiment of the present disclosure. 
         FIG. 15  is a schematic diagram III of steps of the shielding method for the circuit board for high frequency transmission according to the fourth embodiment of the present disclosure. 
         FIG. 16  is a schematic diagram I of steps of a shielding method for a circuit board for high frequency transmission according to a fifth embodiment of the present disclosure. 
         FIG. 17  is a schematic diagram II of steps of the shielding method for the circuit board for high frequency transmission according to the fifth embodiment of the present disclosure. 
         FIG. 18  is a schematic diagram III of steps of the shielding method for the circuit board for high frequency transmission according to the fifth embodiment of the present disclosure. 
     
    
    
     REFERENCE NUMERALS 
       100 . Circuit board body,  101 . Wire region,  102 . Blank region,  103 . First surface,  104 . Second surface,  110 . Opening,  120 . Transition portion,  121 . Smooth transition surface; 
       201   a  and  201   b.  Conductive adhesive layer,  202   a  and  202   b.  Conductive layer,  203   a  and  203   b.  Insulation layer,  210 . First shielding film,  220 . Second shielding film,  230 . Shielding film; 
       300 . Function layer,  310 . First protective film,  320 . Second protective film,  330 . Second insulation layer,  340 . First insulation layer,  350 . Wire layer; 
       400 . Main wire layer,  403 . Third surface,  404 . Fourth surface; 
       500 . Conductor layer. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure is described in detail below, but implementations of the present disclosure are not limited herein. 
     Embodiment I 
     As shown in  FIG. 1  to  FIG. 8 . 
     As shown in  FIG. 1  and  FIG. 2 , a circuit board for high frequency transmission includes a first shielding film  210 , a second shielding film  220 , and a circuit board body  100 . The circuit board body  100  includes a wire region  101  and a blank region  102 . The circuit board body  100  is provided with a first surface  103  and a second surface  104 . The wire region  101  refers to a region having a wire function, includes interconnection lines, and further includes a gap between the above interconnection lines. The wire region  101  represents a region that the wire function is required to be shielded at a lateral side. It cannot be understood that the wire region  101  does not include an insulation portion. The blank region  102  is relative to the wire region  101 , and refers to a region capable of being provided with openings  110 . Any position on the circuit board body  100  except for the wire region  101  may be considered as the blank region  102 , which does not mean that there is nothing in the blank region  102  or the blank region  102  is not conductive. 
     A shielding method for the circuit board for high frequency transmission includes the following steps. 
     (1) As shown in  FIG. 4  and  FIG. 5 , the blank region  102  of the circuit board body  100  is provided with the openings  110 . The openings  110  communicate with the first surface  103  and the second surface  104 . The openings  110  are configured to connect the first shielding film  210  and the second shielding film  220  through the openings  110 . In this embodiment, the blank region  102  is provided with the openings  110 , but the present disclosure is not limited herein, alternatively, in some embodiments, the circuit board body  100  has the openings  110  itself. The connection between the first shielding film  210  and the second shielding film  220  includes bonding without pressure and heating, or may further include bonding under pressure or heating. 
     (2) As shown in  FIG. 6 , in some embodiments, the first shielding film  210  covers the first surface  103  of the circuit board body  100 , the second shielding film  220  covers the second surface  104  of the circuit board body  100 . “The operation of covering the first shielding film  210  on the first surface  103  of the circuit board body  100 ” and “the operation of covering the second shielding film  220  on the second surface  104  of the circuit board body  100 ” are in a random order. 
     In this embodiment, as shown in  FIG. 6 , the first shielding film  210  is flush with an edge of the first surface  103 , and the second shielding film  220  is flush with an edge of the second surface  104 , but the present disclosure is not limited herein. Alternatively, in some embodiments, referring to  FIG. 11 , the first shielding film  210  protrudes out of the edge of the first surface  103 , and the second shielding film  220  protrudes out of the edge of the second surface  104 . 
     (3) The first shielding film  210  and the second shielding film  220  are connected through pressure bonding at the openings  110 , so as to acquire the circuit board for high frequency transmission shown as  FIG. 7 . A junction of the first shielding film  210  and the second shielding film  220  is accommodated in the openings  110 , so as to avoid the press bonding portion of the first shielding film  210  and the second shielding film  220  from being influenced in following processes or avoid influencing the implementation of the following processes, such as a warping of the junction. On the other hand, the press bonding portion is accommodated in the openings  110 , so as to improve space utilization. 
     The acquired circuit board for high frequency transmission is shown as  FIG. 7 . The first shielding film  210  covers the first surface  103  of the circuit board body  100 . The second shielding film  220  covers the second surface  104  of the circuit board body  100 . The first shielding film  210  and the second shielding film  220  are connected at the lateral side of the wire region (wherein “the lateral side” includes all orientations shown in  FIG. 3 ). On one hand, the first shielding film  210  and the second shielding film  220  respectively shield the first surface  103  and the second surface  104  of the circuit board body  100 . On the other hand, the first shielding film  210  and the second shielding film  220  are connected by crossing an edge of the wire region  101 , so as to shield the lateral side of the wire region  101 . In this way, leakage from the lateral side of the wire region  101  is effectively prevented. 
     In this embodiment, the openings  110  refer to through holes. The openings  110  are in the circuit board body  100 . But the present disclosure is not limited herein. In some embodiments, the openings  110  are notches. When the openings  110  are at the edge of the circuit board body  100 , the openings  110  are the notches at the edge of the circuit board body  100 . 
     In some embodiments, a binding material is disposed on a side of the first shielding film  210  that faces the first surface  103  or a side of the second shielding film  220  that faces the second surface  104 , so as to achieve connection. Alternatively, pressure connection may be directly performed without disposing the binding material. 
     In this embodiment, the first shielding film  210  and the second shielding film  220  are two independent films. The first shielding film  210  is attached to the first surface  103  from a side of the circuit board body  100 . The second shielding film  220  is attached to the second surface  104  from another side of the circuit board body  100 . But the present disclosure is not limited herein. In some embodiments, the first shielding film  210  and the second shielding film  220  may also be two parts of an entire shielding film. The two parts respectively cover the first surface  103  and the second surface  104  on the two sides of the circuit board body  100  after the entire shielding film is folded in half. The part covering the first surface  103  is the first shielding film  210 , and the part covering the second surface  104  is the second shielding film  220 . Since one side edges of the first shielding film  210  and the second shielding film  220  are integrally connected, it is only required to connect the other sides of the first shielding film  210  and the second shielding film  220 . 
     The shape of the junction of the first shielding film  210  and the second shielding film  220  is not limited to that shown in this embodiment, which may be in any other shapes. 
     This embodiment only shows one wire region  101 , which is not limited herein. Alternatively, the circuit board body  100  is provided with more than two wire regions  101 . A blank region  102  is disposed between the wire regions  101 , and provided with at least two openings  110 . The first shielding film  210  and the second shielding film  220  cover the more than two wire regions  101 . The first shielding film  210  is connected with the second shielding film  220  in the openings  110 . By connecting the first shielding film  210  and the second shielding film  220  in the blank region  102 , the two adjacent wire regions  101  are simultaneously shielded, so as to prevent mutual interference, and leaky waves from the lateral side of the two adjacent wire regions  101  are prevented simultaneously, so that signal transmission of the two adjacent wire regions  101  is effectively guaranteed. Synchronous connection is achieved at a plurality of openings  110  of a plurality of blank regions  102 , so that high production efficiency is realized. For example, in some embodiments, all openings  110  may be synchronously processed. The first shielding film  210  and the second shielding film  220  are covered. Then, the first shielding film  210  and the second shielding film  220  in all the openings  110  are synchronously connected. In this way, mass production and high efficiency are achieved. 
     Electrical connection between the first shielding film  210  and the second shielding film  220  at the lateral side of the wire region  101  of the circuit board body  100  includes as follows. In a first method, the shielding film includes an insulation layer, a conductive layer, and a conductive adhesive layer that are in lamination arrangement in order. In a second method, the shielding film includes an insulation layer, a conductive layer, and an adhesive layer. A protruding portion electrically connected to the conductive layer is disposed on a side of the conductive layer that is close to the adhesive layer. The protruding portion of the first shielding film penetrates the second shielding film to be electrically connected to the conductive layer of the second shielding film. The protruding portion of the second shielding film penetrates the first shielding film to be electrically connected to the conductive layer of the first shielding film. Alternatively, the protruding portion of the first shielding film is electrically connected to the protruding portion of the second shielding film. In this way, the first shielding film is electrically connected to the second shielding film through mutual contact of the protruding portions. A third method combines the first method and the second method, that is, the shielding film includes the protruding portion and the conductive adhesive layer, so that the first shielding film is electrically connected to the second shielding film through the protruding portion and conducting particles. In this embodiment, by adopting the first connecting method, as shown in  FIG. 7-1 , the first shielding film  210  includes an insulation layer  203   a,  a conductive layer  202   a,  and a conductive adhesive layer  201   a  that are in lamination arrangement in order. The second shielding film  220  includes an insulation layer  203   b,  a conductive layer  202   b,  and a conductive adhesive layer  201   b  that are in lamination arrangement in order. The first shielding film  210  is electrically connected to the second shielding film  220  by contact between the conductive adhesive layers  203   a  and  203   b.  Since the conductive adhesive layers  203   a  and  203   b  contain conducting particles and are viscous, so that the conductive adhesive layers may be bonded together, including bonding under pressure or heating, or bonding under normal temperature and pressure. When the conductive adhesive layers  203   a  and  203   b  are in contact with each other, respective conducting particles are in contact with each other, so as to realize electrical connection. 
     The circuit board body  100  includes but is not limited to a single sided plate, a double sided plate, and a multilayer plate, as long as circuit boards being provided with wires. In this embodiment, as shown in  FIG. 7-1 , the circuit board body  100  is the multilayer plate, but is not limited herein. The circuit board body  100  may also be the single sided plate or the double sided plate. As shown in  FIG. 7-2 , the circuit board body  100  is the single sided plate. The circuit board body  100  includes a first protective film  310 , a function layer  300 , and a second protective film  320  that are laminated in order. The function layer  300  is a part of the circuit board body  100  that excluding the first protective film  310  and the second protective film  320 . The first protective film  310  (or the second protective film  320 ) includes but is not limited to a PI film, a PET film, a PE film, a PP film, a PPS film, and the like. As shown in  FIG. 12-2 , the circuit board body  100  is the double sided plate. The circuit board body  100  includes a first protective film  310 , a first wire layer, an insulation layer, a second wire layer, and a second protective film  320  laminated in order. 
     Embodiment II 
     A difference between Embodiment II and Embodiment I lies in that: as shown in  FIG. 9 , the blank region  102  is provided with the openings  110 . The first shielding film  210  covers surfaces of the wire region  101  and the blank region  102 , and is connected with the second shielding film  220  at the openings  110 . The second shielding film  220  covers surfaces of the wire region  101  and the blank region  102 , and is connected with the first shielding film  210  through the openings  110 . 
     The first shielding film  210  is connected with the second shielding film  220  at the openings  110 , and also covers the surfaces of the wire region  101  and the blank region  102 . The second shielding film  220  is connected with the first shielding film  210  at the openings  110 , and also covers the surfaces of the wire region  101  and the blank region  102 . In this way, the junction of the first shielding film  210  and the second shielding film  220  is simultaneously limited by the first shielding film  210  and the second shielding film  220  in the wire region  101  and the blank region  102 , which cannot be randomly moved, so as to avoid the occurrence of warping. 
     In this embodiment, the first shielding film  210  covers the surfaces of the wire region  101  and the blank region  102 . The second shielding film  220  covers the surfaces of the wire region  101  and the blank region  102 . Not limited by this embodiment, alternatively, in some embodiments, the circuit board body  100  is provided with more than two wire regions  101 . The blank region  102  is disposed between the wire regions  101 , and provided with the openings  110 . The first shielding film  210  and the second shielding film  220  cover the more than two wire regions  101  and the blank region  102 . The first shielding film  210  is connected with the second shielding film  220  through the openings  110 . 
     Embodiment III 
     A difference between Embodiment III and Embodiment I lies in that: 
     Embodiment III is shown in  FIG. 10  to  FIG. 12 . 
     As shown in  FIG. 10-1 , a circuit board body  100  includes a first protective film  310 , a function layer  300 , and a second protective film  320 . The circuit board body  100  further includes a transition portion  120 . An end of the transition portion  120  is connected to a wire region  101 , and another end of the transition portion  120  is a free end. A thickness of at least one part of the transition portion  120  is less than a thickness of the wire region. In this embodiment, the thickness of the transition portion  120  is gradually reduced from a first end to a second end. However, the transition portion  120  is not limited to that shown in this embodiment, which may also be in other shapes. 
     As shown in  FIG. 10-1 , a surface of the transition portion  120  that faces a first surface  103  of the circuit board body  100  is provided with a smooth transition surface  121 . The smooth transition surface  121  guides a first shielding film  210  to bend to a second shielding film  220 . A surface of the transition portion  120  that faces a second surface  104  of the circuit board body  100  is also provided with a smooth transition surface  121 . The smooth transition surface  121  guides the second shielding film  220  to bend to the first shielding film  210 . By providing the smooth transition surface  121 , the first shielding film  210 /the second shielding film  220  is bent gently, so that the fracturing of the first shielding film  210 /the second shielding film  220  due to excessive bending is avoided. In this embodiment, the smooth transition surface  121  only occupies parts of upper and lower surfaces of the transition portion  120 , which is not limited herein. Alternatively, in some embodiments, all connecting surfaces of the transition portion  120  from the first surface  103  to the second surface  104  are designed as the smooth transition surface  121 , as shown in  FIG. 10-2 . 
     As shown in  FIG. 11 , the first shielding film  210  covers the first surface  103 , and protrudes out of an outer edge of the circuit board body  100 . The second shielding film  220  covers the second surface  104 , and protrudes out of the outer edge of the circuit board body  100 . Then, the first shielding film  210  and the second shielding film  220  are connected at a lateral side of the circuit board body  100  (in this case, that is, the first shielding film  210  and the second shielding film  220  are connected at a lateral side of a wire region  101 ), so as to form a structure shown in  FIG. 12 . The transition portion  120  provides transitional support for the connection between the first shielding film  210  and the second shielding film  220 . The circuit board body  100  and the transition portion  120  form a structure similar to steps, so as to make the first shielding film  210 /the second shielding film  220  to achieve two-stage bending of “firstly bending toward the transition portion  120  and then bending and connecting from the transition portion  120 ”, so that the bending degree of the first shielding film  210 /the second shielding film  220  is reduced, and the fracturing of the first shielding film  210 /the second shielding film  220  is avoided. Definitely, in some embodiments, a multi-stage transition portion  120  (similar to multi-stage steps) is disposed. 
     In this embodiment, the transition portion  120  is disposed on an outer edge of the circuit board body  100 , which is not limited herein. In some embodiments, the transition portion  120  is disposed on an inner edge of the opening  110 . 
     In this embodiment, the transition portion  120  is disposed on the edge of the circuit board body  100 , which is not limited by this embodiment. Alternatively, in some embodiments, the transition portion  120  is not disposed on the edge of the circuit board body  100 . The first shielding film  210  and the second shielding film  220  are connected at the lateral side of the circuit board body  100  (in this case, the circuit board body  100  corresponds to the wire region  101 , that is, the first shielding film  210  and the second shielding film  220  are connected at the lateral side of the wire region  101 ). 
     Embodiment IV 
     A difference between Embodiment IV and Embodiment III lies in that: 
     Embodiment IV is shown in  FIG. 13  to  FIG. 15 . 
     As shown in  FIG. 13 , a circuit board body  100  includes a wire region  101  and a blank region  102 . The circuit board body  100  includes a first protective film  310 , a function layer  300 , and a second protective film  320  that are laminated in order. The first protective film  310  and the second protective film  320  are connected at a lateral side of the function layer  300 . A laminated part of the first protective film  310 , the function layer  300 , and the second protective film  320  forms the wire region  101 . The part that the first protective film  310  connected to the second protective film  320  forms the blank region  102 . 
     As shown in  FIG. 14 , openings  110  are manufactured in the blank region  102 . After the openings  110  are manufactured, a transition portion  120  is formed by a part of a junction of the first protective film  310  and the second protective film  320  which is connected to the wire region  101 . That is to say, at the connecting part with the wire region  101 , a part that the first protective film  310  is connected to the second protective film  320  forms the transition portion  120 . A thickness of the wire region  101  equals to “the first protective film  310 +the function layer  300 +the second protective film  320 ”. A thickness of the blank region  102  equals to “the first protective film  310 +the second protective film  320 ”. The thickness of the blank region  102  is less than the thickness of the wire region  101 . Therefore, the transition portion  120  is naturally formed after the openings  110  are manufactured in the blank region. In this way, when the first protective film  310  and the second protective film  320  wrap the function layer  300 , the transition portion  120  is manufactured. Through a bonding connection process, simple process is realized. By connecting edges of the first protective film  310  and the second protective film  320 , the first protective film  310  and the second protective film  320  are tightly attached to the function layer  300 , thereby avoiding peeling off. As shown in  FIG. 14 , in this embodiment, a boundary line is formed at a junction of the first protective film  310  and the second protective film  320 , but the present disclosure is not limited herein. In some embodiments, the pressed first protective film  310  and the second protective film  320  are penetrated into each other, and no obvious boundary lines are formed at the junction. 
     As shown in  FIG. 15 , a first shielding film  210  covers a first surface  103 . A second shielding film  220  covers a second surface  104 . Then, the first shielding film  210  and the second shielding film  220  are connected at a lateral side of the circuit board body  100 , and a junction is accommodated in the openings  110 . 
     Embodiment V 
     A difference between Embodiment V and Embodiment I lies in that: 
     as shown in  FIG. 18 , a circuit board for high frequency transmission includes a circuit board body  100  and a shielding film  230 . The circuit board body  100  includes a main wire layer  400  and a conductor layer  500 . The main wire layer  400  is provided with a third surface  403  and a fourth surface  404  that are arranged opposite to each other. The conductor layer  500  is disposed on the fourth surface  404 . The main wire layer  400  includes a first insulation layer  340 , a wire layer  350 , and a second insulation layer  330  that are laminated in order. The conductor layer  500  is disposed on a surface of the first insulation layer  340  that is away from the wire layer  350 , that is, the conductor layer  500  is disposed on the fourth surface  404 . 
     The main wire layer  400  is provided with openings  110 . The third surface  403  communicates with the conductor layer  500  through the openings  110 . The shielding film  230  covers the third surface  403 . The shielding film  230  extends into the openings  110  to achieve press connection with the conductor layer  500 . The shielding film  230  is electrically connected to the conductor layer  500 . The conductor layer  500  has a shielding effect itself. The shielding film  230  is in press connection with the conductor layer  500 , so that leaky waves at a lateral side of the main wire layer  400  are avoided. 
     A shielding method for the circuit board for high frequency transmission includes the following steps, as shown in  FIG. 16  to  FIG. 18 . 
     (1) As shown in  FIG. 16 , a circuit board body  100  includes a main wire layer  400  and a conductor layer  500 . The main wire layer  400  includes a third surface  403  and a fourth surface  404  that are arranged opposite to each other. The conductor layer  500  is disposed on the fourth surface  404 . 
     (2) As shown in  FIG. 16 , the circuit board body  100  includes a wire region  101  and a blank region  102 . As shown in  FIG. 17 , openings  110  are provided in the blank region  102  of the main wire layer  400 . The third surface  403  communicates with the conductor layer  500  through the openings  110 . 
     (3) The shielding film  230  covers the third surface  403 . The shielding film  230  extends into the openings  110  to achieve press connection with the conductor layer  500 . The shielding film  230  is electrically connected to the conductor layer  500 . 
     In this way, the shielding film  230  and the conductor layer  500  are in electrical connection at a lateral side of the wire region  101 , so as to form a structure shown as  FIG. 18 , thereby shielding leaky waves at the lateral side of the wire region  101 . 
     Various technical features of the above embodiments may be combined arbitrarily. For brevity of description, description is not made to all possible combinations of the various technical features of the above embodiments are described. However, all the combinations of these technical features should be considered to fall within the scope of disclosure contained in the specification as long as there is no contradiction between the combinations of those technical features. 
     The above embodiments merely illustrate several implementations of the present disclosure, which are specifically described in detail, but are not to be construed as limiting the scope of the present patent for the present disclosure.