Patent Publication Number: US-8975996-B2

Title: Electronic component and method of manufacturing the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Application No. 2012-037547 filed on Feb. 23, 2012, the entire contents of this application being incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The technical field relates to electronic components and methods of manufacturing the electronic components. More specifically, the technical field relates to electronic components including a multilayer body formed by stacking a plurality of insulating layers, and to methods of manufacturing the electronic components. 
     BACKGROUND 
     Examples of known existing electronic components include an electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2000-236157. In the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2000-236157, a plurality of insulating layers are stacked on an insulating substrate. A plurality of helical coil conductors are stacked together with the insulating layers. Via hole conductors extending through the insulating layers connect the plurality of the helical coil conductors to one another. The electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2000-236157 is manufactured using a photolithography method. 
     SUMMARY 
     The present disclosure provides an electronic component in which the occurrence of disconnections between line conductor layers and via hole conductor can be suppressed and a method of manufacturing the electronic component. 
     An electronic component according to an embodiment of the present disclosure includes: a multilayer body formed by stacking a plurality of insulating layers including a first insulating layer and a second insulating layer; a conductor layer provided on the first insulating layer; a line conductor layer provided on the second insulating layer, which is provided on an upper side of the first insulating layer in a stacking direction; and a via hole conductor that connects an end portion of the line conductor layer to the conductor layer and that extends through the second insulating layer in the stacking direction. In the via hole conductor, a connection surface connected to the line conductor layer is formed of a circular portion and a protrusion. The protrusion protrudes from the circular portion in a first direction in which the line conductor layer extends from the end portion. 
     A method of manufacturing the electronic component described above includes: forming the first insulating layer; forming the conductor layer on the first insulating layer; forming, on the conductor layer, the second insulating layer in which the via hole connected to the conductor layer is formed; and forming the via hole conductor by filling a conductor into the via hole and forming the line conductor layer on the second insulating layer, using a photolithography method. In the forming of the second insulating layer, the via hole conductor having an upper end surface formed of a circular portion and a protrusion protruding from the circular portion in the first direction is formed. 
     Embodiments according to the present disclosure can suppress the occurrence of disconnections between line conductor layers and via hole conductor layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a transparent view of an electronic component according to an exemplary embodiment. 
         FIG. 2  is a perspective view of coil conductor layers and a via hole conductor. 
         FIGS. 3A to 3D  are sectional process diagrams for illustrating manufacture of the electronic component. 
         FIGS. 4A to 4D  are sectional process diagrams for illustrating manufacture of the electronic component. 
         FIGS. 5A to 5D  are sectional process diagrams for illustrating manufacture of the electronic component. 
         FIGS. 6A to 6C  are sectional process diagrams for illustrating manufacture of the electronic component. 
         FIG. 7  is a diagram illustrating a photo mask. 
         FIG. 8  is a process diagram illustrating the details of a process step illustrated in  FIG. 5A . 
         FIG. 9  is a diagram illustrating a via hole conductor and coil conductor layers according a modification. 
         FIG. 10  is a diagram of a via hole conductor according to a second modification when viewed in plan from the z-axis direction. 
         FIG. 11  is a sectional structure diagram of a via hole conductor, coil conductor patterns, and insulating layers. 
     
    
    
     DETAILED DESCRIPTION 
     The inventors realized that in the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2000-236157, disconnections may occur between the via hole conductors and the coil conductor patterns.  FIG. 11  is a sectional structure diagram of a via hole conductor  500 , coil conductor patterns  502   a  and  502   b , and insulating layers  504   a  and  504   b.    
     The coil conductor pattern  502   a  is provided on the insulating layer  504   a . The insulating layer  504   b  is provided on the coil conductor pattern  502   a  and the insulating layer  504   a . The coil conductor pattern  502   b  is provided on the insulating layer  504   b . The via hole conductor  500  extends through the insulating layer  504   b  in the stacking direction and connects the coil conductor pattern  502   a  and the coil conductor pattern  502   b.    
     The via hole conductor  500  and the coil conductor pattern  502   b  described above are formed using a photolithography method. The via hole conductor  500  and the coil conductor pattern  502   b  shrink when the via hole conductor  500  and the coil conductor pattern  502   b  are dried. In particular, a portion at which the via hole conductor  500  and the coil conductor pattern  502   b  are connected to each other, which has a larger volume than other portions, considerably shrinks. As a result, the via hole conductor  500  shrinks in the thickness direction of the insulating layer  504   b  and, hence, becomes thinner than the insulating layer  504   b . Consequently, disconnections may occur between the coil conductor pattern  502   a  and the via hole conductor  500  and between the via hole conductor  500  and the coil conductor pattern  502   b.    
     Hereinafter, an electronic component and a method of manufacturing the electric component according to exemplary embodiments of the present disclosure that can address the above-described shortcoming will now be described with reference to the figures. 
       FIG. 1  is a transparent view of an electronic component  10  according to a first exemplary embodiment. Hereinafter, the stacking direction of the electronic component  10  is defined as the z-axis. When viewed in plan from the z-axis direction, the direction in which the long sides of the electronic component  10  extend is defined as the x-axis direction, and the direction in which the short sides of the electronic component  10  extend is defined as the y-axis direction. Hereinafter, viewing in plan from the positive z-axis direction is simply expressed as viewing in plan from the z-axis direction. 
     As illustrated in  FIG. 1 , the electronic component  10  includes a multilayer body  12 , external electrodes  14  ( 14   a ,  14   b ), and a coil L. 
     The multilayer body  12  is shaped like a rectangular parallelepiped, and is formed by stacking rectangular insulating layers  15  and  16   a  to  16   h  ( 16 ) in this order from the positive z-axis direction side to the negative z-axis direction side, as illustrated in  FIG. 1 . The insulating layer  15  is stacked on furthest toward the positive side in the z-axis direction and is a surface marker layer having a marker formed thereon indicating the orientation of the multilayer body. 
     The coil L includes coil conductor layers  18   a  to  18   g , sometimes collectively referred to herein as coil conductor layers  18 , and via hole conductors V 1  to V 6 , sometimes collectively referred to herein as via hole conductors V. The coil conductor layers  18   a  to  18   g , which are respectively provided on the insulating layers  16   b  to  16   h , are line conductor layers revolving around the respective intersections of the diagonals of the insulating layers  16   b  to  16   h , when viewed in plan from the z-axis direction. 
     A first end of the coil conductor layer  18   a  extends to the negative x-axis direction side end surface of the multilayer body  12 . A second end of the coil conductor layer  18   g  extends to the positive x-axis direction side end surface of the multilayer body  12 . 
     The via hole conductors V 1  to V 6  respectively extend through the insulating layers  16   b  to  16   g  in the z-axis direction and connect the corresponding ends of the coil conductor layers  18   a  to  18   g  that neighbor one another in the z-axis direction. In more detail, the via hole conductor V 1  connects the second end of the coil conductor layer  18   a  to a first end of the coil conductor layer  18   b . The via hole conductor V 2  connects the second end of the coil conductor layer  18   b  to a first end of the coil conductor layer  18   c . The via hole conductor V 3  connects the second end of the coil conductor layer  18   c  to a first end of the coil conductor layer  18   d . The via hole conductor V 4  connects the second end of the coil conductor layer  18   d  to a first end of the coil conductor layer  18   e . The via hole conductor V 5  connects the second end of the coil conductor layer  18   e  to a first end of the coil conductor layer  18   f . The via hole conductor V 6  connects the second end of the coil conductor layer  18   f  to the first end of the coil conductor layer  18   g . The coil L formed in the manner described above extends in the z-axis direction in a helical shape. 
     The external electrode  14   a  covers the negative x-axis direction side end of the multilayer body  12 , and is connected to the first end of the coil conductor layer  18   a . The external electrode  14   b  covers the positive x-axis direction side end of the multilayer body  12 , and is connected to the second end of the coil conductor layer  18   g . As a result, the coil L is connected between the external electrodes  14   a  and  14   b.    
     The electronic component  10  has a configuration described below in order to suppress the occurrence of disconnections between the coil conductor layers  18  and the via hole conductors V. The via hole conductor V 6  will be described below as an example.  FIG. 2  is a perspective view of the coil conductor layers  18   f  and  18   g  and the via hole conductor V 6 . 
     The insulating layer  16   g  (second insulating layer) is stacked on the positive z-axis direction side of the insulating layer  16   h  (first insulating layer). The coil conductor layer  18   g  (conductor layer) is provided on the insulating layer  16   h . The coil conductor layer  18   g  extends in the x-axis direction. The coil conductor layer  18   f  (line conductor) is provided on the insulating layer  16   g . The coil conductor layer  18   f  extends in the x-axis direction. The first end of the coil conductor layer  18   g  and the second end of the coil conductor layer  18   f  are superposed with each other when viewed in plan from the z-axis direction. 
     The via hole conductor V 6  connects the second end of the coil conductor layer  18   f  to the first end of the coil conductor layer  18   g , and extends through the insulating layer  16   g  in the z-axis direction. Hereinafter, a surface of the via hole conductor V 6  connected to the coil conductor layer  18   f  is called a connection surface S 1 . 
     The connection surface S 1  is formed of a circular portion P 1  and a protrusion P 2 . The circular portion P 1  is shaped like a circle when viewed in plan from the z-axis direction. The protrusion P 2 , when viewed in plan from the z-axis direction, protrudes from the circular portion P 1  in a direction in which the coil conductor layer  18   f  extends from the second end of the coil conductor layer  18   f  (i.e., the negative x-axis direction). The protrusion P 2  is shaped like a triangle. The angle θ of the apex of the protrusion P 2  is preferably between 15 degrees and 60 degrees inclusive. The optimal value of the angle θ is 30 degrees. 
     As a result of the connection surface S 1  being formed of the circular portion P 1  and the protrusion P 2 , the via hole conductor V 6  has the shape of a protrusion P 4  combined with a truncated cone P 3 . The truncated cone P 3  has a shape whose diameter becomes smaller from the positive z-axis direction side to the negative z-axis direction side. The protrusion P 4  has the shape of a triangular pyramid in which the amount of protrusion from the truncated cone P 3  becomes smaller from the positive z-axis direction side to the negative z-axis direction side. In the embodiment shown in  FIG. 2 , protrusion protrudes from the circular portion towards a first direction in which the coil conductor layer  18   f  extends from its end portion. More particularly, a straight line passing through a center of the circular portion P 1  and a midpoint of a width of the protrusion P 2  is substantially parallel with the direction in which conductor  18   f  extends from an end portion of conductor  18   f  where the via hole conductor V 6  is positioned. 
     Note that since the via hole conductors V 1  to V 5  can have the same shape as the via hole conductor V 6 , description thereof is not provided as it can be understood from the above description. 
     Hereinafter, an exemplary method of manufacturing the electronic component  10  will be described with reference to the figures.  FIGS. 3A to 6C  are sectional process diagrams for illustrating manufacture of the electronic component  10 .  FIG. 7  is a diagram illustrating a photo mask M 2 .  FIG. 8  is a sectional process diagram illustrating the process step of  FIG. 5A  in detail. 
     First, an insulating layer  116   h  is formed using a photolithography method. Specifically, as illustrated in  FIG. 3A , the insulating layer  116   h  is formed by application of a photosensitive insulating material (e.g., a photosensitive resin including glass powder) using a printing method. At this time, the insulating layer  116   h  is formed in such a manner that the insulating layer  116   h  after sintering has a thickness of 10 μm. After that, the insulating layer  116   h  is dried. 
     Next, as illustrated in  FIG. 3B , the insulating layer  116   h  is subjected to exposure, whereby the insulating layer  116  is hardened. Through the process steps illustrated in  FIG. 3A  and  FIG. 3B , the insulating layer  116   h  is formed. 
     Next, the coil conductor layer  18   g  is formed on the insulating layer  116   h  using, for example, a photo lithography method. Specifically, as illustrated in  FIG. 3C , a conductor layer  118   g  is formed by applying a photosensitive conductive material over the whole surface of the insulating layer  116   h  using a printing method. At this time, the conductor layer  118   g  is formed in such a manner that the coil conductor layer  18   g  after sintering has a thickness of 8 μm. After that, the conductor layer  118   g  is dried. Although not illustrated, the conductor layer  118   g  shrinks while being dried. The shrinking ratio of the conductor layer  118   g  is between 0.6 and 0.9 inclusive. Here, the shrinking ratio of the conductor layer  118   g  is a value obtained by dividing the volume of the conductor layer  118   g  after having been dried by the volume of the conductor layer  118   g  before being dried. 
     Next, as illustrated in  FIG. 3D , the conductor layer  118   g  is subjected to exposure using a photo mask M 1  which allows light to pass through only a portion thereof corresponding to the coil conductor layer  18   g . As a result, only a portion of the conductor layer  118   g  corresponding to the coil conductor layer  18   g  is hardened. 
     Next, a portion of the conductor layer  118   g  which has not been hardened is removed using a developing solution. As a result, the coil conductor layer  18   g  is developed, as illustrated in  FIG. 4A . Through the process steps illustrated in  FIG. 3C ,  FIG. 3D , and  FIG. 4A , the coil conductor layer  18   g  is formed. 
     Next, an insulating layer  116   g  in which a via hole h 6  connected to the coil conductor layer  18   g  is formed is formed on the coil conductor layer  18   g  using a photolithography method. Specifically, as illustrated in  FIG. 4B , an insulating layer  116   g  is formed by applying a photosensitive insulating material over the whole exposed surfaces of the insulating layer  116   h  and the coil conductor layer  18   g  using a printing method. After that, the insulating layer  116   g  is dried. 
     Next, as illustrated in  FIG. 4C , the insulating layer  116   g  is subjected to exposure using the photo mask M 2  that does not allow light to pass therethrough only at a portion where the via hole conductor V 6  is to be formed, thereby hardening the insulating layer  116   g . As illustrated in  FIG. 7 , the photo mask M 2  is made in such a manner that a Cr plating portion having the same shape as the connection surface S 1  of the via hole conductor V 6  is formed on a transparent plate, such as a glass plate. As a result, the insulating layer  116   g  excluding a portion thereof where the via hole conductor V 6  is to be formed is hardened. 
     Next, a portion of the insulating layer  116   g  which has not been hardened is removed using a development solution. As a result, referring to  FIG. 4D , the via hole h 6  is formed in the insulating layer  116   g . Note that as a result of using the photo mask M 2  illustrated in  FIG. 7 , the top end of the via hole h 6  is formed of a circular portion and a protrusion protruding from the circular portion in the negative x-axis direction. Further, the via hole h 6  becomes thinner, or has decreasing area in the x-axis and y-axis plane in the negative z-axis direction. This is because, in the process illustrated in  FIG. 4D , it becomes harder for a development solution to reach a deeper portion of the insulating layer  116   g . Through the process steps illustrated in  FIG. 4B to 4D , the insulating layer  116   g  is formed. 
     Next, using a photolithography method, the via hole h 6  is filled with a conductor, thereby forming the via hole conductor V 6  having a diameter of 50 μm, and the coil conductor layer  18   f  is formed on the insulating layer  116   g . Specifically, as illustrated in  FIG. 5A , a conductor layer  118   f  made of a photosensitive conductive material is applied over the whole surface of the insulating layer  116   g  using a printing method. After that, the conductor layer  118   f  is dried. As illustrated in  FIG. 8 , the conductor layer  118   f  and the via hole conductor V 6  shrink while being dried. In particular, the via hole conductor V 6 , which has a larger volume per unit area when viewed in plan than the rest of the conductor layer  118   f , considerably shrinks. However, the connection surface S 1  of the via hole conductor V 6  is formed of the circular portion P 1  and the protrusion P 2 . Hence, the via hole conductor V 6  has the shape of the protrusion P 4  combined with the truncated cone P 3 , as a result of the connection surface S 1  being formed of the circular portion P 1  and the protrusion P 2 . Consequently, even when the via hole conductor V 6  shrinks, since the protrusion P 4  is shaped like a triangular pyramid, the volume gradually decreases in the protruding direction and, hence, the degree of shrinkage due to drying also gradually decreases. In other words, the degree of shrinkage of the protrusion P 4  gradually decreases in the protruding direction. Hence, connection between the via hole conductor V 6  and the conductor layer  118   f  is maintained, and disconnection is prevented from occurring. 
     Next, as illustrated in  FIG. 5B , the conductor layer  118   f  is subjected to exposure using a photo mask M 3  which allows light to pass through a portion thereof corresponding to the coil conductor layer  18   f . As a result, only a portion of the conductor layer  118   f  corresponding to the coil conductor layer  18   f  is hardened. 
     Next, a portion of the conductor layer  118   f  which has not been hardened is removed using a development solution. As a result, the coil conductor layer  18   f  is developed as illustrated in  FIG. 5C . 
     After that, by repeating the process steps illustrated in  FIG. 4B  to  FIG. 5C , insulating layers  116   a  to  116   f , the coil conductor layers  18   a  to  18   e , and the via hole conductors V 1  to V 5  are formed, as illustrated in  FIG. 5D . 
     Next, as illustrated in  FIG. 6A , an insulating layer  115  made of a photoconductive material is applied using a printing method. Then, the insulating layer  115  is dried. As a result, a mother multilayer body  112  is obtained. 
     Next, as illustrated in  FIG. 6B , a plurality of multilayer bodies  12  are obtained by cutting the mother multilayer body  112  using a dicer or the like. Note that the mother multilayer body  112  is cut in such a manner that the multilayer bodies  12  each having a size of 0.3 mm×0.3 mm×0.6 mm are obtained after sintering. After that, the multilayer bodies  12  are sintered at a predetermined temperature. 
     Next, as illustrated in  FIG. 6C , the multilayer bodies  12  are subjected to barrel finishing, whereby the edges of the multilayer bodies  12  are chamfered. 
     Finally, as illustrated in  FIG. 1 , the external electrodes  14   a  and  14   b  are formed. Specifically, underlying electrodes are formed by applying conductive paste made of Ag. The external electrodes  14   a  and  14   b  are formed by plating the underlying electrodes with Ni and Sn. Through the process steps described above, the electronic component  10  is manufactured. 
     The electronic component  10  configured as described above and the method of manufacturing the electronic component  10  allow for suppression of the occurrence of disconnections between the coil conductor layers  18  and the via hole conductors V. In more detail, as illustrated in  FIG. 8 , the conductor layer  118   f  and the via hole conductor V 6  shrink while being dried. In particular, the via hole conductor V 6  considerably shrinks since the volume per unit area is large when the conductor layer  118   f  is viewed in plan. 
     Hence, the connection surface S 1  of the via hole conductor V 6  is formed of the circular portion P 1  and the protrusion P 2 . The protrusion P 2  protrudes in a direction in which the coil conductor layer  18   f  obtained by developing the conductor layer  118   f  extends. As a result, the via hole conductor V 6  has the shape of the protrusion P 4  combined with the truncated cone P 3 . Hence, even when the conductor layer  118   f  shrinks, connection between the protrusion P 4  and the conductor layer  118   f  can be maintained. Consequently, disconnection between the conductor layer  118   f  and the via hole conductor V 6  can be prevented from occurring. 
     In the electronic component  10 , the angle θ of the apex of the protrusion P 2  is preferably between 15 degrees and 60 degrees inclusive. As a result of the angle θ being 15 degrees or more, a developing solution is allowed to easily penetrate into the protrusion P 4 , and the protrusion P 4  shaped like a triangular pyramid having a sufficiently large size is formed. As a result of the angle θ being 60 degrees or less, the diameter of the via hole conductors V is prevented from becoming too large. When the angle θ is larger than 60 degrees, a developing solution penetrates into the protrusion P 4  too much and the protrusion P 4  becomes too large. In this case, the length of the protrusion P 4  becomes too large and the protrusion P 4  may protrude from the coil conductor layer  18  and come in contact with another coil conductor layer  18 . Hence, it is preferable that the angle θ be 60 degrees or less. Note that the optimal value of the angle θ is 30 degrees. 
     Although ways of suppressing disconnection may include forming the coil conductor layers  18  in such a manner as to have a large thickness in advance, when the ratio of the thickness of the insulating layers  16  in the z-axis direction to the thickness of the coil conductor layers  18  in the z-axis direction is 1.0 or less, the thickness of the insulating layers  16  in the z-axis direction becomes small. Hence, the distance between the coil conductor layers  18  becomes small and stray capacitance between the coil conductor layers  18  becomes large. As a result, the Q characteristics of the coil of the electronic component  10  are degraded. Consequently, in the electronic component  10 , it is preferable that the ratio of the thickness of the insulating layers  16  in the z-axis direction to the thickness of the coil conductor layers  18  in the z-axis direction be larger than 1.0. 
     It is preferable that the thickness of the conductor layers  118  in the z-axis direction before sintering be larger than or equal to 6 μm. This is because when the thickness of the conductor layers  118  in the z-axis direction before sintering is smaller than 6 μm, it is difficult to form the coil conductor layers  18 . 
     Hereinafter, a via hole conductor V 6  according to a first exemplary modification will be described with reference to the figures.  FIG. 9  is a diagram illustrating the via hole conductor V 6  and coil conductor layers  18   g  and  18   f  according to the first modification. 
     When the coil conductor layer  18   g  extends in the y-axis direction and the coil conductor layer  18   f  extends in the x-axis direction, the via hole conductor V 6  is provided in a corner formed by the coil conductor layers  18   f  and  18   g . In this case, the protrusion P 2  may face in a slanting direction with respect to the x-axis direction. As can be seen in  FIG. 9 , the protrusion P 2  faces towards a direction in which conductor  18   f  extends from an end portion of conductor  18   f . However, it is required that the protrusion P 2  do not protrude from the coil conductor layer  18   f  when viewed in plan from the z-axis direction and that the protrusion P 2  form an acute angle with the negative x-axis direction. That is, it can be seen that a straight line passing through a center of the circular portion P 1  and a midpoint of a width of the protrusion P 2  (i.e., the apex) forms an acute angle with a longitudinal axis of the conductor  18   f.    
     Hereinafter, a via hole conductor Va according a second exemplary modification and a via hole conductor Vb according to a third exemplary modification will be described with reference to the figures.  FIG. 10  is a diagram of the via hole conductor Va according to the second modification when viewed in plan from the z-axis direction. 
     As illustrated in  FIG. 10 , the protrusion P 2  may be shaped like a rectangle. Furthermore, there may be a plurality of protrusions. 
     The electronic component  10  configured as described above and the manufacturing method are not limited to the electronic component  10  and the manufacturing method according to the embodiments described above, and various modifications are possible within the scope of the disclosure. 
     The dimensions of the electronic component  10  are exemplary, and not limited to those described in the embodiments. Examples of the dimensions of the electronic component  10  will be described below. 
     The size of the electronic component  10 : 0.2 mm×0.2 mm×0.6 mm, 0.5 mm×0.5 mm×1.0 mm
     The thickness of the coil conductor layers  18 : 6 μm-13 μm after sintering (8 μm-17 μm before sintering)   The thickness of the insulating layers  16 : 7 μm-15 μm after sintering (9 μm-30 μm before sintering)   The diameter of the via hole conductors V: 20 μm-65 μm after sintering   

     As described above, embodiments consistent with the present disclosure are useful in electronic components and methods of manufacturing them, and in particular have an advantage in suppression of disconnections between line conductor layers and via hole conductor layers.