Patent Publication Number: US-2022225510-A1

Title: Circuit board and method for manufacturing the same

Description:
FIELD 
     The present disclosure relates to a circuit board and a manufacturing method thereof. 
     BACKGROUND 
     Electronic products are widely used in daily work and life, and light, thin, and small electronic products are becoming more and more popular. As a main component of electronic products, circuit boards occupy a large amount of space in the electronic products. The size of the circuit boards greatly affects the size of the electronic products. Large-size circuit boards are difficult to be installed in thin, short, and small-size electronic products. 
     A solution to reduce the size of a circuit board is to improve a density of electronic components (such as resistors and capacitors) on the circuit board, and also to use smaller electronic components. To improve the density or to use smaller electronic components, pin ports with a smaller size and a higher density need to be used. The pin ports are generally formed on the circuit board by a solder mask process, but it is difficult to form pin ports with small size and high precision due to expansion and contraction of film and the influence of exposure to the environment. In addition, the pin ports formed by the solder mask process have a trapezoidal structure, which makes it difficult for gas in the pin ports to be discharged during reflow soldering with solder paste, resulting in poor soldering and reducing reliability of components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawn figures are to be viewed in conjunction with the embodiments described herein. 
         FIG. 1  is a diagrammatic view showing an inner laminated structure according to an embodiment of the present disclosure. 
         FIG. 2  is a schematic diagram of the inner laminated structure of  FIG. 1  laser-etched through a mask. 
         FIG. 3  is a plan view of the inner laminated structure of  FIG. 2 . 
         FIG. 4  is a schematic diagram of a second opening with residue according to an embodiment of the present disclosure. 
         FIG. 5  is a schematic diagram of a surface of a connection pad exposed for a surface treatment in the second opening of  FIG. 4 . 
         FIG. 6  is a schematic diagram of a metal coating formed on the connection pad of  FIG. 5 . 
         FIG. 7  is a schematic diagram of a conductive paste formed on the metal coating of  FIG. 6 . 
         FIG. 8  is a schematic diagram of an electronic component mounted in the second opening of  FIG. 7 . 
         FIG. 9  is a schematic cross-sectional view showing a circuit board according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout. 
     The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used herein, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     A method for manufacturing a circuit board  1  (shown in  FIG. 9 ) according to an embodiment of the present disclosure includes the following steps: 
     Step S 1 , referring to  FIG. 1 , an inner laminated structure  10  is provided. The inner laminated structure  10  includes a conductive wiring layer  102  and a cover layer  104 , the cover layer  104  is on the outermost side of the inner laminated structure  10 , and the conductive wiring layer  102  includes a connection pad  105 . 
     In one embodiment, a prefabricated wiring board is provided, the prefabricated wiring board is the inner laminated structure  10 . The inner laminated structure  10  may include a first base board  101 , the conductive wiring layer  102 , an adhesive layer  103 , and the cover layer  104 . The conductive wiring layer  102  is disposed on a surface of the first base board  101 , the adhesive layer  103  is disposed on a side of the conductive wiring layer  102  away from the first base board  101 , and the cover layer  104  is disposed on a side of the adhesive layer  103  away from the conductive wiring layer  102 . The cover layer  104  is bonded with the first base board  101  and the conductive wiring layer  102  through the adhesive layer  103  and covers the conductive wiring layer  102 . 
     In one embodiment, the inner laminated structure  10  is a double-layer plate, two conductive wiring layers  102  are disposed on opposite surfaces of the first base board  101 , and two cover layers  104  are bonded with the two conductive wiring layers  102  through two adhesive layers  103 . 
     In one embodiment, the inner laminated structure  10  does not include a solder mask. The solder mask has a limited etching accuracy, so small-size and high-precision etching and component placement is difficult to achieve. The omitting of the solder mask means that the cover layer  104  provides protection for the inner laminated structure  10 , so that the manufacturing method is simplified, the cost is reduced, and the reliability of product is improved. 
     Step S 2 , referring to  FIG. 2 , a mask  20  is provided on a side of the cover layer  104  away from the conductive wiring layer  102 . The mask  20  defines a plurality of first openings  21  penetrating the mask  20 . The cover layer  104  is etched with a laser cutting head  22  through the mask  20  to form a second opening  106  to expose the connection pad  105 . 
     In one embodiment, the mask  20  covers a surface of the cover layer  104 , and the laser cutting head  22  emits laser light to etch the inner laminated structure  10 . In the etching process, at least part of the cover layer  104  corresponding to the first opening  21  is removed to form the second opening  106 . 
     In one embodiment, the mask  20  may be a prefabricated structure, and the prefabricated mask  20  can be used again. 
     In one embodiment, if the inner laminated structure  10  includes the adhesive layer  103 , part of the adhesive layer  103  corresponding to the first opening  21  is removed in the etching process, to expose the connection pad  105 . 
     In one embodiment, in a direction perpendicular to the inner laminated structure  10 , a diameter of the second opening  106  gradually increases from the inside to the outside of the inner laminated structure  10 . In one embodiment, the second opening  106  has a trapezoid shape which tapers downwards, a top of the second opening  106  is wider than a bottom of the second opening  106 . Such second opening  106  promotes release of any gas in the subsequent printing process. 
     In one embodiment, there are multiple first openings  21  and second openings  106 . The multiple second openings  106  are spaced apart from each other. 
     In one embodiment, the multiple second openings  106  are of different sizes and are formed in one scanning path of the laser cutting head  22 . In the etching process, due to the existence of the mask  20 , the laser cutting head  22  etches the inner laminated structure  10  only when scanning to the first opening  21 . That is, etching with the laser in cooperation with the mask  20  reduces the replacement of the laser cutting head  22  and the adjustment of energy parameters, so that the etching of the multiple second openings  106  can be realized in one scanning process, the manufacturing efficiency is improved. Referring to  FIG. 3 , using laser in cooperation with the mask  20 , the etching of the multiple second openings  106  in one scanning process is realized, so that damage to the inner laminated structure  10  caused by over-etching is avoided and the etching accuracy is improved. In the etching process, a shape of the second opening  106  is determined by a shape of the first opening  21  on the mask  20 , and is not limited by a maximum rounding of the laser cutting head  22 . 
     Step S 3 , a surface treatment is applied to the inner laminated structure  10 . 
     Step S 31 , the mask  20  is removed. 
     In one embodiment, the removed mask  20  can be used again in the above processes. 
     Step S 32 , referring to  FIG. 4 , residue  24  may exist in the second opening  106  after laser etching. The residue  24  may be residue of glue or debris after etching. The residue  24  in the second opening  106  is removed by plasma or other degumming process to fully expose a surface of the connection pad  105 . 
     Step S 33 , referring to  FIG. 5 , the surface treatment is applied to the surface of the connection pad  105 . The surface treatment can improve the finish and flatness of the connection pad  105 . 
     Step S 34 , referring to  FIG. 6 , a metal coating  11  is formed on the surface of the connection pad  105  exposed from the second opening  106 . In one embodiment, the metal coating  11  is formed by chemical vapor deposition or physical vapor deposition, the metal coating  11  may be of nickel or of gold. 
     Step S 35 , referring to  FIG. 7 , a conductive paste  12  is formed in the second opening  106  to electrically connect the metal coating  11 . That is, the conductive paste  12  is electrically connected with the connection pad  105  through the metal coating  11 . 
     Step S 4 , referring to  FIG. 8 , an electronic component  13  is provided to electrically connect with the connection pad  105 . 
     In one embodiment, at least part of the electronic component  13  is disposed in the second opening  106  and is electrically connected with the connection pad  105  through the conductive paste  12 . Specifically, the electronic component  13  includes a first surface  131  and a second surface  132  opposite to each other, the first surface  131  is in contact with the inner laminated structure  10 , and the second surface  132  is on a side of the electronic component  13  away from the inner laminated structure  10 . The electronic component  13  also includes two connection pins  130 , which are arranged in the second opening  106  and electrically connected with the metal coating  11  through the conductive paste  12 . The two connection pins  130  can be arranged in two adjacent second openings  106 . When the two connection pins  130  are pressed down, the conductive paste  12  arranged in each second opening  106  with narrow bottom and wide top gradually fills the second opening  106 , and gas in the second opening  106  is allowed sufficient time to be discharged. 
     Referring to  FIG. 9 , the circuit board  1  prepared by the above manufacturing method is also disclosed. 
     The circuit board  1  includes the inner laminated structure  10 , the metal coating  11 , the conductive paste  12 , and the electronic component  13 . 
     The inner laminated structure  10  includes the first base board  101 , the conductive wiring layer  102 , the adhesive layer  103 , and the cover layer  104 . The conductive wiring layer  102  is disposed on a surface of the first base board  101 , the adhesive layer  103  is disposed on a side of the conductive wiring layer  102  away from the first base board  101 , and the cover layer  104  is disposed on a side of the adhesive layer  103  away from the conductive wiring layer  102 . The cover layer  104  is bonded with the first base board  101  and the conductive wiring layer  102  through the adhesive layer  103  and covers the conductive wiring layer  102 . 
     In one embodiment, the inner laminated structure  10  is a double-layer plate, two conductive wiring layers  102  are disposed on opposite surfaces of the first base board  101 , and two cover layers  104  are bonded with the two conductive wiring layers  102  through two adhesive layers  103 . 
     In one embodiment, the inner laminated structure  10  does not include a solder mask. The solder mask has a limited etching accuracy, so it is difficult to realize small-size and high-precision etching and component placement. The omitting of the solder mask means that the cover layer  104  provides protection for the inner laminated structure  10 , so that the manufacturing method is simplified, the cost is reduced, and the reliability of product is improved. 
     The inner laminated structure  10  also includes the second opening  106 , and the conductive wiring layer  102  includes the connection pad  105 . The second opening  106  penetrates parts of the adhesive layer  103  and the cover layer  104  to expose at least part of the connection pad  105 . 
     In a direction perpendicular to the inner laminated structure  10 , a diameter of the second opening  106  gradually increases from the inside to the outside of the inner laminated structure  10 . In one embodiment, the second opening  106  has a downwardly-tapering trapezoidal cross-section, an edge of the second opening  106  in contact with the connection pad  105  is a bottom edge of the trapezoid shape. 
     The metal coating  11  is disposed on a surface of the connection pad  105  in the second opening  106 . In one embodiment, the metal coating  11  is formed by chemical coating or physical coating, the metal coating  11  may be of nickel or gold. 
     In one embodiment, the conductive paste  12  is disposed in the second opening  106  and fills at least part of the second opening  106 , the conductive paste  12  is electrically connected with the metal coating  11 . 
     The electronic component  13  is electrically connected with the conductive wiring layer  102  through the metal coating  11 . 
     In one embodiment, the electronic component  13  includes a first surface  131  and a second surface  132  opposite to each other, the first surface  131  is in contact with the inner laminated structure  10 , and the second surface  132  is on a side of the electronic component  13  away from the inner laminated structure  10 . The electronic component  13  also includes two connection pins  130 , which are arranged in the second opening  106  and electrically connect with the metal coating  11  through the conductive paste  12 . The two connection pins  130  can be arranged in two adjacent second openings  106 . In other embodiments, the first surface  131  of the electronic component  13  is not in contact with the inner laminated structure  10 . 
     In one embodiment, the cover layer  104  is made of an elastic polymer material, a material of the cover layer  104  includes one of a group consisting of liquid crystal polymer, polypropylene, polyethylene terephthalate, polyimide, polytetrafluoroethylene, polyolefin, and a combination thereof. When the first surface  131  is in contact with the covering layer  104 , the cover layer  104  of the elastic polymer material absorbs a part of the pressure when the electronic component  13  is pressed against the inner laminated structure  10 , thereby avoiding rupture of the electronic component  13 . 
     The above is only a preferred embodiment of the present disclosure, and is not intended to limit the scope of the present disclosure. Although embodiments of the present disclosure are described above, it is not intended to limit the present disclosure. The present disclosure may be modified or modified to equivalent variations without departing from the technical scope of the present disclosure by any person skilled in the art. Any simple modifications, equivalent changes and modifications made to the above embodiments remain within the scope of the technical solutions of the present disclosure.