Patent Publication Number: US-11399436-B2

Title: Circuit board

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of patent application Ser. No. 16/231,997, filed on Dec. 25, 2018, assigned to the same assignee, which is based on and claims priority to China Patent Application No. 201811133481.8 filed on Sep. 27, 2018, the contents of which are incorporated by reference herein. 
    
    
     FIELD 
     The subject matter herein generally relates to circuit boards, and more particularly to a circuit board adapted for multi-signal transmission. 
     BACKGROUND 
     As electronic devices become smaller, circuit boards of the electronic devices are required to be smaller. Thus, a density of signal lines on the circuit board may become denser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present disclosure will now be described, by way of embodiments only, with reference to the attached figures. 
         FIG. 1  is a cross-sectional view of a first embodiment of a baseboard of a circuit board. 
         FIG. 2  shows the baseboard in  FIG. 1  with a through hole. 
         FIG. 3  is a top view of the baseboard in  FIG. 2 . 
         FIG. 4  is an isometric view of the baseboard in  FIG. 2 . 
         FIG. 5  shows the baseboard in  FIG. 4  after metalizing the through hole. 
         FIG. 6  shows the baseboard in  FIG. 5  having a plurality of conductive circuit lines. 
         FIG. 7  shows the baseboard in  FIG. 6  having a metal layer of the through hole removed. 
         FIG. 8  is a cross-sectional view of a second embodiment of a baseboard of a circuit board. 
         FIG. 9  shows the baseboard in  FIG. 8  with a through hole. 
         FIG. 10  is an isometric view of the baseboard in  FIG. 9 . 
         FIG. 11  shows the baseboard in  FIG. 10  after metalizing the through hole and forming a plurality of conductive circuit lines. 
         FIG. 12  shows the baseboard in  FIG. 11  having a metal layer of the through hole removed. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. Additionally, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. 
       FIGS. 1-7  show a first embodiment of a method for making a circuit board  100 . 
     As shown in  FIG. 1 , a baseboard  10  is provided. 
     The baseboard  10  is a double-sided board including a base layer  11 , a first base copper layer  12  formed on a first side of the base layer  11 , and a second base copper layer  13  formed on a second side of the base layer  11 , second side being opposite to the first side. 
     In one embodiment, the base layer  11  is a flexible resin layer, such as polyimide, polyethylene terephthalate, or polyethylene naphthalate. 
     As shown in  FIG. 2 , at least one through hole  101  is defined in the baseboard  10 . The through hole  101  passes through the first base copper layer  12 , the base layer  11 , and the second base copper layer  13  in sequence. 
     The through hole  101  can be defined by laser processing, machine cutting, or other suitable methods. 
     As shown in  FIGS. 3 and 4 , a plurality of grooves  103  are defined in an inner wall of the through hole  101 . Each of the plurality of grooves  103  passes through the first base copper layer  12 , the base layer  11 , and the second base copper layer  13  in sequence. 
     The plurality of grooves  103  can be defined by laser processing, machine cutting, or other suitable methods. 
     In one embodiment, a quantity of the plurality of grooves  103  is four. The four grooves  103  are equally spaced apart around the through hole  101 . In other embodiments, a quantity of the plurality of grooves  103  can be changed according to requirements. 
     As shown in  FIG. 5 , the through hole  101  and the plurality of grooves  103  are metalized to form a metal layer  23   a  on an inner wall of the through hole  101  and fill in the plurality of grooves  103  with metal. The metal layer  23   a  forms a via  20 , and the metal filled in the plurality of grooves  103  forms a plurality of conductive lines  21   a . Each of the plurality of conductive lines  21   a  electrically couples the first base copper layer  12  to the second base copper layer  13 . 
     In other embodiments, a copper layer (not shown) is formed on a surface of the first copper layer  12  and a surface of the second copper layer  13 . 
     As shown in  FIG. 6 , the first base copper layer  12  is circuit processed to form a first conductive circuit layer  120  from the first base copper layer  12 , and the second base copper layer  13  is circuit processed to form a second conductive circuit layer  130  from the second base copper layer  13 . The first conductive circuit layer  120  includes a plurality of first conductive circuit lines  121 , and the second conductive circuit layer  130  includes a plurality of second conductive circuit lines  131 . Each conductive line  21   a  electrically couples one of the plurality of first conductive circuit lines  121  to a corresponding one of the plurality of second conductive circuit lines  131 . 
     As shown in  FIG. 7 , the metal layer  23   a  is removed from the inner wall of the through hole  101 . In one embodiment, the metal layer  23   a  is removed by machine drilling the via  20 . In other embodiments, the metal layer  23   a  may be removed by laser cutting, etching, or other suitable methods. 
       FIGS. 8-11  show a second embodiment of a method for making a circuit board  100 . 
     As shown in  FIG. 8 , an insulated base layer  11  is provided. 
     The insulated base layer  11  may be made of polyimide, polyethylene terephthalate, or polyethylene naphthalate. 
     As shown in  FIG. 9 , at least one through hole  110  is defined in the base layer  11 . The through hole  110  can be defined by laser processing, machine cutting, or other suitable method. 
     The insulated base layer  11  includes two opposite surfaces  11   a  and  11   b.    
     As shown in  FIG. 10 , a plurality of via slots  113  are defined in an inner wall of the through hole  110 . Each of the plurality of via slots  113  passes through the surfaces  11   a ,  11   b  of the insulated base layer  11 . 
     The via slots  113  can be defined by laser processing, machine cutting, or other suitable method. 
     As shown in  FIG. 11 , circuits are created on the surface  11   a  by a fully additive process to form a first conductive circuit layer  120  from the surface  11   a , circuit process the surface  11   b  to form a second conductive circuit layer  130  from the surface  11   b , form a conductive line  21   b  in each of the via slots  113 , and a metal layer  23   b  on an inner wall of the through hole  110 . The metal layer  23   b  forms a via  20 . The first conductive circuit layer  120  includes a plurality of first conductive circuit lines  121 , and the second conductive circuit layer  130  includes a plurality of second conductive circuit lines  131 . Each of the plurality of conductive lines  21   b  electrically couples one of the first conductive circuit lines  121  to a corresponding one of the second conductive circuit lines  131 . 
     As shown in  FIG. 12 , the metal layer  23   b  is removed from the inner wall of the through hole  110 . In one embodiment, the metal layer  23   b  is removed by a machine drilling process. In other embodiments, the metal layer  23   b  can be removed by laser cutting, etching, or other suitable method. 
     In another embodiment, the first conductive circuit layer  120 , the second conductive circuit layer  130 , the conductive lines  21   b , and the via  20  are formed by a semi-additive process. 
     In another embodiment, the plurality of grooves  103  and/or the plurality of via slots  113  are roughened before being metalized. 
     As shown in  FIG. 7 , a circuit board  100  includes a base layer  11 , a first conductive circuit layer  120 , and a second conductive circuit layer  130 . The first conductive circuit layer  120  and the second conductive circuit layer  130  are respectively formed from opposite sides of the base layer  11 . The first conductive circuit layer  120  includes a plurality of first conductive circuit lines  121 , and the second conductive circuit layer  130  includes a plurality of second conductive circuit lines  131 . The circuit board  100  further defines at least one through hole  101 . A plurality of conductive lines  21   a  are formed in an inner wall of each of the through holes  101 . Each of the conductive lines  21   a  electrically couples one of the first conductive circuit lines  121  to a corresponding one of the second conductive circuit lines  131 . 
     As described in the embodiments above, the circuit board  100  includes a plurality of conductive lines  21   a  ( 21   b ) formed in each through hole  101 . Each conductive line  21   a  ( 21   b ) electrically couples one of the plurality of first conductive circuit lines  121  to a corresponding one of the plurality of second conductive circuit lines  131  to achieve multi-signal transmission through the same through hole  101 . Thus, the circuit board  100  can be made in a small size with a high density of signal transmission. 
     The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including, the full extent established by the broad general meaning of the terms used in the claims.