Abstract:
A capacitor includes a first patterned conductive layer, a second patterned conductive layer and a first patterned dielectric layer. The first patterned conductive layer resembles a comb with internal teeth, and the second patterned conductive layer resembles a comb with external teeth, the internal and the external teeth being interlaced in one plane. A thin first patterned dielectric layer within the same plane is shaped and arranged to infill all the gaps between the teeth. The first patterned conductive layer, the second patterned conductive layer, and the first patterned dielectric layer create a single coplanar layer, and a number of such interconnected coplanar layers are stacked within and contained by a multilayer circuit board.

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to a capacitor and a multilayer circuit board using the capacitor. 
     2. Description of the Related Art 
     A capacitor on a circuit board may include two opposite metal layers and a dielectric layer positioned between the two opposite metal layers. Capacitance of the capacitor is proportional to an area of the metal layers, and is inversely proportional to a thickness of the dielectric layer. That is, capacitance of the capacitor can be improved by increasing the area of the metal layers or by decreasing thickness of the dielectric layer. However, increasing the area of the metal layers may cause the capacitor to occupy much more space, and decreasing the thickness of the dielectric layer may affect impedance matching with other circuits of the circuit board. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of an exemplary capacitor and multilayer circuit board 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 exemplary capacitor and multilayer circuit board. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment. 
         FIG. 1  is a schematic view of a capacitor according to an exemplary embodiment. 
         FIG. 2  is an exploded view of the capacitor shown in  FIG. 1 . 
         FIG. 3  is a plane view of a first electronic layer and a third electronic layer of the capacitor shown in  FIG. 1 . 
         FIG. 4  is a plane view of a second electronic layer and a fourth electronic layer of the capacitor shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view taken along line V-V of the capacitor shown in  FIG. 1 . 
         FIG. 6  is a schematic view of a multilayer circuit board according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , a capacitor  10  according to an exemplary embodiment is shown. The capacitor  10  includes at least two stacked conductive layers positioned in close proximity to each other and a dielectric layer  119  positioned between each two conductive layers. In this exemplary embodiment, the capacitor  10  includes four stacked conductive layers, with the dielectric layer  119  positioned between each two conductive layers. The four conductive layers are a first conductive layer  11 , a second conductive layer  12 , a third conductive layer  13  and a fourth conductive layer  14 . Each of the four conductive layers  11 ,  12 ,  13  and  14  includes a positive electrode  80  and a negative electrode  90 . The positive electrodes  80  are electronically connected through a first connector to form a positive electrode of the capacitor  10 , and the four negative electrodes  90  are electronically connected through a second connector to form a negative electrode of the capacitor  10 . The first conductive layer  11  may have a same shape as the third conductive layer  13 , and the second conductive layer  12  may have the same shape as the fourth conductive layer  14 . 
     The first conductive layer  11  includes a first negative portion  113 , a first positive portion  115  and a first dielectric layer  117 . The first negative portion  113 , the first positive portion  115  and the first dielectric layer  117  are coplanar. The first positive portion  115  is a patterned conductive layer defining a plurality of openings. The first negative portion  113  has a shape corresponding to the openings defined in the first positive portion  115 . The first dielectric layer  117  is a patterned dielectric layer. The first negative portion  113  and the first dielectric layer  117  are located corresponding to the openings of the first positive portion  115 , and the first dielectric layer  117  is sandwiched between the first positive portion  113  and the first negative portion  115 . The first negative portion  113  has a shape which is complementary relative to the first positive portion  115 , in that the first positive portion  115  can be said to be inserted into the first negative portion  113 . In detail, the first dielectric layer  117  is positioned in the gaps between the first negative portion  113  and the first positive portion  115  so as to infill all the spaces between the two portions. The first positive portion  115  is electronically coupled to the positive electrode  80  of the first conductive layer  11 , the first negative portion  113  is electronically coupled to the negative portion  90  of the first conductive layer  11 . The first positive portion  115  may be comb-shaped, and includes a first coupling portion  1153  and a plurality of first branch portions  1154  extending from a side of the first coupling portion  1153 . Each of the first branch portions  1154  includes a first main part  1156  and a plurality of first branch parts  1157 . The plurality of first branch parts  1157  may be parallel with each other, and parallel in particular to the first coupling portion  1153 , each two adjacent first main parts  1156  having a uniform space. The plurality of the first main parts  1156  may be spaced substantially evenly and arranged in parallel, in particular being perpendicular to the plurality of first branch parts  1157 . The first branch parts  1157  radiate from two opposite sides of the first main part  1156 . The first branch parts  1157  may be symmetrically arranged about the first branch parts  1157 . One side of the first coupling portion  1153  is perpendicularly connected to the positive electrode  80 , and the opposite side of the first coupling portion  1153  is perpendicularly connected to the plurality of first main parts  1156 . In this embodiment, the first coupling portion  1153 , the plurality of first main parts  1156  and the plurality of first branch parts  1157  are approximately strip shaped. The first coupling portion  1153  and the plurality of first branch portions  1154  are all coplanar. 
     The first negative portion  113  includes a second coupling portion  1133  and a plurality of second branch portions  1134  extending from a side of the second coupling portion  1133 . Each of the second branch portions  1134  includes a second main part  1136  and a plurality of second branch parts  1137 . The plurality of the second branch parts  1137  may be parallel with each other, and in particular parallel to the second coupling portion  1133 , each two adjacent second main parts  1136  having a uniform space. The plurality of the second main parts  1136  may be spaced substantially evenly and arranged in parallel, in particular being perpendicular to the plurality of the second branch parts  1137 . One side of the second coupling portion  1133  is perpendicularly connected to the negative electrode  90 , and the other opposite side of the second coupling portion  1133  is perpendicularly connected to the second main parts  1136 . The two second main parts  1136  are positioned at the two ends of the second coupling portion  1133  and a plurality of second branch parts  1137  extend therefrom, and a distance between the two adjacent second branch parts  1137  is slightly greater than the width of the positive electrode  80 . The other second main parts  1136  extend from two opposite sides to form a plurality of second branch parts  1137  symmetrical arranged about the second main parts  1136 . One side of the second coupling portion  1133  is perpendicularly connected to the negative electrode  90 , and the opposite side of the second coupling portion  1133  is perpendicularly connected to the plurality of the second main parts  1136 . In this embodiment, the second coupling portion  1133 , the plurality of second main parts  1136  and the plurality of second branch parts  1137  are approximately strip shaped. The second coupling portion  1133  and the plurality of second branch portions  1134  are coplanar. The first coupling portion  1153  is parallel to the second coupling portion  1133 . 
     The first coupling portion  1153  and the first branch portion  1154  are positioned with a gap between the second coupling portion  1133  and the second branch portion  1134 . The plurality of first main parts  1156  and the plurality of second main parts  1136  are alternately arranged along a first arrangement direction. The plurality of first branch parts  1157  and the plurality of second branch parts  1137  are inserted in the spaces between the first main parts  1156  and the second main parts  1136  and are alternately arranged along a second arrangement direction in each space. The second arrangement direction may be an extending direction of the first or second main part  1156 ,  1136 , and the first arrangement direction is perpendicular to the second arrangement direction. The first dielectric layer  117  is positioned between the first negative portion  113  and the first positive portion  115  to create a capacitive arrangement and capability between the first negative portion  113  and the first position portion  115 . The first dielectric layer  117  is sandwiched between the first branch part  1157  and the adjacent second branch parts  1137 , between the first branch parts  1157  and the second main parts  1136 , and between the second branch parts  1137  and the first main parts  1156  to form a dielectric insulator between the first branch portion  1154  and the second branch portion  1134 . 
     Referring to  FIG. 4  and  FIG. 5 ,  FIG. 4  is a plane view of a second conductive layer  12  and a fourth electronic layer  14  of the capacitor shown in  FIG. 1 .  FIG. 5  is a cross-sectional view taken along line V-V of the capacitor shown in  FIG. 1 . The second electronic layer  12  includes a second negative portion  123 , a second positive portion  125  and a second dielectric layer  127 . The second negative portion  123 , the second positive portion  125  and the second dielectric layer  127  are coplanar. Materials, dimensions, and functions of the second negative portion  123 , the second positive portion  125  and the second dielectric layer  127  are in all respects substantially identical to those of the first negative portion  113 , the first positive portion  115  and the first dielectric layer  117  respectively. 
     The first conductive layer  11 , the second conductive layer  12 , the third conductive layer  13  and the fourth electrode  14  are stacked from top to bottom in that order with the dielectric layer  119  between two coplanar conductive layers which are in close proximity. Each positive electrode on one conductive layer is opposite to the negative electrode of other adjacent conductive layer, each negative electrode on one conductive layer is opposite to a positive electrode of another adjacent conductive layer, and on the same coplanar layer, each negative electrode is opposite to a positive electrode (as shown in  FIG. 5 ). 
       FIG. 6  is a schematic view of a multilayer circuit board  100  according to an exemplary embodiment. The multilayer circuit board  100  includes a top layer  30 , a bottom layer  50  and each layer of the capacitor  10  is between a top layer  30  and a bottom layer  50 . The top layer  30  and the bottom layer  50  cover and enclose the capacitor  10  together. The top layer  30  and the bottom layer  50  are dielectric layers, and wires (not shown) are positioned on the surface of the top layer  30  and the bottom layer  50  to be electronically coupled to electronic components positioned on the surface of the top layer  30  and the bottom layer  50 . 
     Each conductive layer includes a plurality of first coupling parts interlaced with a plurality of second coupling parts. There are not only electrical fields created between the layers in the stack, but also electrical fields created between the negative portions and the positive portions in the same coplanar layer. Therefore, the capacitance of the capacitor is increased without changing the size of the capacitor. Furthermore, the capacitor is in itself a multilayer component, and can be located within the multilayer circuit board so the individual coplanar layers match the multiple layers of the multilayer circuit board, hence a wiring and other space of the multilayer circuit board is saved. 
     It is to be understood, however, that even though numerous characteristics and advantages of the exemplary disclosure have been set forth in the foregoing description, together with details of the structure and function of the exemplary disclosure, the disclosure is illustrative only, and changes may be made in detail, especially in the matters of shape, size, and arrangement of parts within the principles of exemplary disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.