Patent Publication Number: US-11031174-B2

Title: Thin film type inductor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2017-0134150 filed on Oct. 16, 2017 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a thin film type inductor, and more particularly, to a thin film type power inductor advantageous for high inductance and miniaturization. 
     BACKGROUND 
     In accordance with the development of information technology (IT), apparatuses have been rapidly miniaturized and thinned. Therefore, market demand for small, thin devices has increased. 
     Korean Patent Laid-Open Publication No. 10-1999-0066108 provides a power inductor including a substrate having a via hole and coils disposed on opposite surfaces of the substrate and electrically connected to each other by the via hole of the substrate, in accordance with such a technical trend to provide an inductor including coils having uniform and high aspect ratios. 
     Further, in a design of the power inductor, generally, upper and lower coils are connected to each other by filling a via hole. Here, a line width of a via hole pad portion may be designed to be wider than that of other coil patterns. Therefore, a plating layer in the vicinity of the pad portion may grow rapidly, as compared to other coil patterns, and when an additional planarization process is not subsequently performed, it may be difficult to provide a plating pattern having a desired thickness without a plating deviation. 
     SUMMARY 
     An aspect of the present disclosure may provide a thin film type inductor in which a plating deviation is decreased by controlling line widths of upper and lower coil patterns directly connected to a via hole not to excessively grow as compared to a line width of other coil patterns. 
     According to an aspect of the present disclosure, a thin film type inductor may include: a body including an internal coil including a plurality of coil patterns, a support member supporting the internal coil, and a magnetic material encapsulating the internal coil and the support member, the body having upper and lower surfaces facing each other in a thickness (T) direction, first and second end surfaces in a length (L) direction, and first and second side surfaces in a width (W) direction; and external electrodes disposed on an external surface of the body and electrically connected to the internal coil. The internal coil may include an upper coil and a lower coil disposed on upper and lower surfaces of the support member, respectively, in the thickness direction. The upper and lower coils may be connected to each other by a via penetrating through the support member. A plurality of first coil patterns forming the upper coil and a plurality of second coil patterns forming the lower coil may include an upper connection pattern and a lower connection pattern, respectively, which are directly connected to the via. At least one of an upper portion of the upper connection pattern and an upper portion of the lower connection pattern may include an inclined surface. 
     According to another aspect of the present disclosure, a thin film type inductor may include: a body including an internal coil including a plurality of coil patterns, a support member supporting the internal coil, and a magnetic material encapsulating the internal coil and the support member, the body having upper and lower surfaces facing each other in a thickness (T) direction, first and second end surfaces in a length (L) direction, and first and second side surfaces in a width (W) direction; and external electrodes disposed on an external surface of the body and electrically connected to the internal coil. The internal coil may include an upper coil and a lower coil disposed on upper and lower surfaces of the support member, respectively, in the thickness direction. The upper and lower coils may be connected to each other by a via penetrating through the support member. A plurality of first coil patterns forming the upper coil and a plurality of second coil patterns forming the lower coil may include an upper connection pattern and a lower connection pattern, respectively, which are directly connected to the via. Each of the upper and lower connection patterns may include an upper region and a lower region, the upper region located at a farther side from the support member, the lower region located at a nearer side to the support member and directly connected to the via. A cross section of the lower region of at least one of the upper and lower connection patterns in a width-thickness (W-T) direction may have a rectangular shape, and a cross section of the upper region of at least one of the upper and lower connection patterns in the width-thickness (W-T) direction may have a trapezoidal shape, which has a decreasing width in the width direction from the nearer side to the farther side of the support member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view of a thin film type inductor according to an exemplary embodiment in the present disclosure; 
         FIG. 2  is a plan view of an internal coil of  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view taken along line I-I′ of  FIG. 1 ; 
         FIG. 4  is a schematic cross-sectional view of a modified example of the thin film type inductor of  FIG. 3 ; and 
         FIG. 5  is a schematic cross-sectional view of another modified example of the thin film type inductor of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. 
     Hereinafter, a thin film type inductor according to an exemplary embodiment in the present disclosure will be described, but is not necessarily limited thereto. 
       FIG. 1  is a schematic perspective view of a thin film type inductor  100  according to an exemplary embodiment in the present disclosure, and  FIG. 2  is a schematic plan view of an internal coil of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the thin film type inductor  100  may include a body  1  and external electrodes  21  and  22  disposed on an external surface of the body. 
     Next, the body  1  may form an exterior of the thin film type inductor, have upper and lower surfaces opposing each other in a thickness (T) direction, first and second end surfaces opposing each other in a length (L) direction, and first and second side surfaces opposing each other in a width (W) direction, and be substantially hexahedron. However, an external shape of the body is not limited. 
     The body  1  may contain a magnetic material  11  having magnetic properties. Here, as the magnetic material  11 , any material may be used as long as it has magnetic properties. For example, the magnetic material  11  may be ferrite or a material in which metal magnetic particles are filled in a resin, wherein the metal magnetic particle may contain one or more selected from the group consisting of iron (Fe), silicon (Si), chromium (Cr), aluminum (Al), and nickel (Ni). 
     The magnetic material  11  may serve as an encapsulant encapsulating a support member  12  to be described below and an internal coil  13  supported by the support member  12 . 
     The first and second external electrodes  21  and  22  may be connected to lead portions of the internal coil  13  exposed to the first and second end surfaces of the body opposing each other in the length direction, respectively. The first and second external electrodes may be formed to be extended to the upper and lower surfaces and the first and second side surfaces of the body adjacent to the first and second end surfaces of the body as well as the first and second end surfaces thereof to thereby entirely have an alphabet C shape, but are not limited thereto. That is, the first and second external electrodes may also be formed of L-shaped electrodes or bottom-surface electrodes. 
     Referring to  FIGS. 1 and 2 , a region A including a coil pattern in the vicinity of a via connecting upper and lower coils  131  and  132  of the internal coil  13  to each other is illustrated. The region A illustrates that the thin film type inductor  100  according to the present disclosure includes a coil pattern having a substantially uniform line width as compared to a thin film type inductor according to the related art. Since the line width of the coil pattern in the region A is substantially the same as that of other coil patterns, it may be appreciated that a plating deviation between the coil patterns is not large. This may be appreciated from the fact that generally, in a case of designing a coil pattern to have a wide line width at a specific point, at the time of plating the coil pattern, since a plating growth rate at the specific point is faster than a plating growth rate at other points, over-plating of the coil pattern occurs at the specific point. When the over-plating occurs at the specific point as described above, only in a case of adjusting the thickness of the coil pattern to be uniform using a separate method such as a polishing method, or the like, the coil pattern having a uniform thickness may be obtained. Meanwhile, as illustrated in the region A of  FIGS. 1 and 2 , since the line width of the coil pattern in the vicinity of the via is substantially the same as that of other points, a filling rate of the magnetic material  11  filled in a through hole H may be increased. 
     Next, a specific shape of a plurality of coil patterns including the region A of  FIGS. 1 and 2  will be described in more detail with reference to  FIG. 3 . 
       FIG. 3  is a schematic cross-sectional view taken along line I-I′ of  FIG. 1 . Referring to  FIG. 3 , the internal coil  13  may include the upper coil  131  supported on an upper surface of the support member and the lower coil supported on a lower surface of the support member based on the support member  12 . Meanwhile, since a detailed description of the upper coil  131  may be applied to the lower coil  132  as it is, hereinafter, for convenience of explanation, a separate description of the lower coil  132  will be omitted. 
     A through hole H and a via hole spaced apart from the through hole H by a predetermined distance may be included in the support member  12 . As described above, the magnetic material  11  may be filled in the through hole H, and the via hole may be filled with a conductive material to form a via  15 . Here, the via  15  may serve to connect the upper and lower coils  131  and  132  to each other. 
     The via  15  may be directly connected to an upper connection pattern  131   c  among the plurality of coil patterns of the upper coil  131  and directly connected to a lower connection pattern  132   c  among the plurality of coil patterns of the lower coil. In this case, a connection structure between the via  15  and the upper connection pattern  131   c  and between the via  15  and the lower connection pattern  132   c  may be suitably selected by those skilled in the art in consideration of process conditions and desired characteristics. For example, the via  15  may be formed so that a side surface of the via hole is enclosed by a seed pattern and a portion of the via  15  penetrating through the via hole is formed integrally with the upper and lower connection patterns  131   c ,  132   c  without a boundary line therebetween, but is not limited thereto. 
     The upper connection pattern  131   c  directly connected to the via  15  may include lower and upper regions  1311   c  and  1312   c . Although the upper and lower regions  1311   c  and  1312   c  are formed integrally with each other without a boundary line therebetween, for convenience of explanation, these regions are illustrated as configurations distinguished from each other. A cross section of the lower region  1311   c  of the upper connection pattern  131   c  in a width-thickness (W-T) direction may have a rectangular shape. Since an insulating part  14  insulating the plurality of coil patterns from each other serves as a guide of the upper connection pattern  131   c , the cross section described above may be obtained. Since the insulating part  14  is prepared before a plating process for the internal coil  13  is performed, the internal coil  13  may grow only in a space in an opening portion prepared in the insulating part  14 . As a result, the lower region  1311   c  of the upper connection pattern  131   c  may grow so as to have a rectangular cross section. 
     Next, a cross section of the upper region  1312   c  of the upper connection pattern  131   c  in the width-thickness (W-T) direction may have a trapezoidal shape. One surface of the upper region  1312   c  may be an inclined surface, which inclines toward a center of a core of the internal coil  13 , and a method of forming the inclined surface is not limited, but for example, the inclined surface may be formed by performing exposure and development at least two times. As a specific example, after laminating an insulating sheet on the support member, performing primary exposure, and subsequently performing secondary exposure, development may be performed. At the time of performing the primary exposure, exposure may be performed at an exposure amount of 1000 mJ/cm 2  to 3000 mJ/cm 2 , and the secondary exposure may be additionally performed only on a region in which the inclined surface will be formed. In this case, it is suitable that an exposure amount of the secondary exposure is selected in a range of 2.5% to 15% of the exposure amount of the primary exposure, and may be preferably about 50 mJ/cm 2  to 400 mJ/cm 2 . The inclined surface may be substantially formed by additionally performing the secondary exposure. An inclined angle of the inclined surface or a maximum width of the inclined surface may be suitably determined by those skilled in the art. 
     A width W 1  of an edge of the upper connection pattern  131   c  coming into contact with the support member  12  may be wider than a width W 2  of an upper surface of the upper connection pattern  131   c  in parallel with the support member  12 . A width W 3  of an edge of the lower connection pattern  132   c  coming into contact with the support member  12  may be wider than a width W 4  of an upper surface of the lower connection pattern  132   c  in parallel with the support member  12 . 
     A width W 1  of an edge of the upper connection pattern  131   c  coming into contact with the support member  12  may be substantially equal to a maximum width of a coil pattern closest to the upper connection pattern  131   c  among the plurality of coil patterns forming the upper coil  131 . A width W 3  of an edge of the lower connection pattern  132   c  coming into contact with the support member  12  is substantially equal to a maximum width of a coil pattern closest to the lower connection pattern  132   c  among the plurality of coil patterns forming the lower coil  132 . When the cross section of the upper region  1312   c  of the upper connection pattern  131   c  in the width-thickness (W-T) direction has the trapezoidal shape, an innermost insulating part  141   a  disposed to be adjacent to the center of a magnetic core of the internal coil  13  while coming into contact with the inclined surface of the upper region  1312   c  of the upper connection pattern  131   c  may also have an inclined surface corresponding to the inclined surface of the upper region  1312   c . The innermost insulating part  141   a  may be composed of a basic insulating part  1412   a  and a remaining insulating part  1411   a  including the inclined surface. The remaining insulating part  1411   a  may be formed by secondary exposure. The remaining insulating part  1411   a  may serve to prevent over-plating of the upper connection pattern, and since the remaining insulating part  1411   a  serves as a guide for plating growth, the remaining insulating part  1411   a  may serve to control the over-growth of the upper connection pattern  131   c  in the width or thickness direction. As a result, the upper connection pattern  131   c  may not have an over-plating growth defect in the upper region  1312   c  thereof while having the lower region  1311   c  wide enough to prevent an open failure of the via  15  from occurring. 
     The insulating part  14  may further include insulating parts  141   b   1 ,  141   b   2 ,  142   b   3 ,  142   b   4 , and  142   b   5  serving as growth guides of the coil pattern in addition to the innermost insulating part  141   a  disposed in an innermost portion of the insulating part  14 . The insulating parts  141   b   1 ,  141   b   2 ,  142   b   3 ,  142   b   4 , and  142   b   5  may be formed simultaneously with forming the basic insulating part  1412   a  of the innermost insulating part  141   a . A coil pattern having a high aspect ratio may be stably formed by the insulating parts  141   b   1 ,  141   b   2 ,  142   b   3 ,  142   b   4 , and  142   b   5 . Cross sections of the insulating parts  141   b   1 ,  141   b   2 ,  142   b   3 ,  142   b   4 , and  142   b   5  in the W-T direction may have a rectangular shape, but a design for the cross-sectional shape thereof may be suitably changed into a suitable shape by those skilled in the art at the time of exposure. 
     In addition, an additional insulating part  16  may be further disposed on the insulating part  14 . The additional insulating part  16  may be a configuration for insulation between the upper surface of the coil pattern and the magnetic material  11 , but may be simultaneously disposed on the insulating part  14 , such that a double insulation effect may be implemented. A method of forming the additional insulating part  16  is not limited. For example, the additional insulating part may be formed by laminating an insulating sheet. There is no need to use a photosensitive insulating material as a material of the additional insulating part  16 , but any material may be used as long as it has insulation properties. On the contrary, since the insulating part  14  needs to be subjected to exposure and development, it is advantageous to form the insulating part  14  using the photosensitive insulating material. 
       FIG. 4  is a schematic cross-sectional view of a modified example of the thin film type inductor of  FIG. 3 . A thin film type inductor  200  of  FIG. 4  is substantially equal to the thin film type inductor  100  of  FIG. 3  except that a shape of an additional insulating part  16 ′ is different. For convenience of explanation, a description of components overlapping those of the thin film type inductor of  FIG. 3  will be omitted, and the overlapping components will be denoted by the same reference numerals. 
     Referring to  FIG. 4 , the additional insulating part  16 ′ of the thin film type inductor  200  may be formed only on upper surfaces of respective coil patterns. The additional insulating part  16 ′ may be formed only on the upper surfaces of the coil patterns but is not formed on an upper or side surface of an insulating part  14 , such that there is no double insulation effect, but a thickness of the insulating layer may be entirely decreased. A spare space in which a magnetic material  11  may be filled may be further secured corresponding to a decrease in thickness of the insulating layer as compared to an inductor having the same size. As a result, permeability of the thin film type inductor may be improved. Here, the additional insulating part  16 ′ has a uniform thickness, and the thickness of the additional insulating part  16 ′ may be preferably 1 μm or more to 10 μm or less. When the thickness of the additional insulating part  16 ′ is thinner than 1 μm, it may be difficult to secure insulation reliability between the coil pattern and the magnetic material  11 , and when the thickness of the additional insulating part  16 ′ is thicker than 10 μm, the space in which the magnetic material  11  may be filled may be insufficient. A method of forming the additional insulating part  16 ′ is not limited, but in order to insulate only the upper surfaces of the coil patterns, for example, a method of forming an oxide layer may be applied. 
     Since the additional insulating part  16 ′ insulates only the upper surfaces of the coil patterns, an upper surface of the insulating part  14  may come in direct contact with the magnetic material  11 . 
     Next,  FIG. 5  is a schematic cross-sectional view of a modified example of the thin film type inductor of  FIG. 3 . A thin film type inductor  300  of  FIG. 5  is substantially equal to the thin film type inductor  100  of  FIG. 3  except that an insulation structure including an insulating part and an additional insulating part is different. For convenience of explanation, a description of components overlapping those of the thin film type inductor  100  of  FIG. 3  will be omitted, and the overlapping components will be denoted by the same reference numerals. 
     Referring to  FIG. 5 , an insulator  17  may be disposed along surfaces of coil patterns. The insulator  17  may insulate the coil patterns and a magnetic material  11  from each other while insulating a plurality of coil patterns from each other. A method of forming the insulator  17  is not limited, but for example, the insulator  17  may be formed by depositing a parylene resin, or the like, on the surface of the coil pattern using a chemical vapor deposition method. A thickness of the insulator  17  may be uniformly formed. Here, the term “uniform thickness” means that a width of the insulator insulating between the coil patterns and a thickness of the insulator insulating the upper surfaces of the coil pattern are substantially equal to each other. 
     A method of forming the insulator  17  is not particularly limited, but in the thin film type inductor  100  of  FIG. 3 , the insulating part disposed before forming the coil patterns by plating is removed after the coil pattern is formed by the plating and subsequently, the insulator  17  may be formed using a chemical vapor deposition method. 
     Since the insulator  17  insulates the coil patterns at a relative thin thickness along the surfaces of the coil patterns, a space in which the magnetic material  11  may be filled may be relatively sufficiently secured. Particularly, since the magnetic material  11  as well as the insulator  17  may be disposed on inclined surfaces of upper regions  1312   c  of upper and lower connection patterns  131   c ,  132   c , respectively, a filling rate of the magnetic material in the vicinity of the center of the core may be increased. Further, in the vicinity of the center of the core, a case in which a flow of a magnetic flux is not smooth due to an increase in magnetic flux density may frequently occur, but the flow of the magnetic flux may be controlled to be optimized along the inclined surfaces of the upper and lower connection patterns  131   c ,  132   c.    
     With the above-mentioned thin film type inductor, particularly, a plating deviation of coil patterns may be decreased in a power inductor field requiring an ultra small size and high inductance, and the flow of the magnetic flux in the vicinity of the center of the core and the filling rate may be improved. Since there is no need to add a new process line at the time of deriving the structure of the thin film type inductor, it may be easy to change a design. Requirements for a limit size for preventing the open failure of the via or facility restrictions may be satisfied, and at the same time, a deviation between the coil pattern and the connection pattern connected to the via may be significantly decreased. 
     As set forth above, according to exemplary embodiments in the present disclosure, the thin film type inductor capable of increasing the filling rate of the magnetic material in the center of the core of the coil and decreasing the plating deviation between the coil patterns by decreasing the size of the coil pattern connected to the via may be provided. 
     While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present invention as defined by the appended claims.