Patent Publication Number: US-2023142850-A1

Title: Inductor, inductor fabrication method, and power supply circuit containing inductor

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is based upon and claims priority to Chinese Patent Application No. 202111312334.9, filed on Nov. 8, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of semiconductors, and specifically, to an inductor, an inductor fabrication method, and a power supply circuit containing the inductor. 
     BACKGROUND 
     The inductor is one of the components commonly used in power supply circuits, which can convert electrical energy into magnetic energy and store it. In some circuits which use 220V alternating current as the power source, some part circuits that are sensitive to electromagnetic interference (EMI) require inductor to be connected to both the power source input terminals for filtering to reduce EMI and ripple noises. However, the inductor, serving as a power device, generates a magnetic field during operation which is easily radiated to the outside, affecting the normal operation of other circuits and components. Therefore, it is necessary to magnetically shield the inductor. 
     Commercially available inductors are usually magnetically shielded by wrapping one or more layers of copper foil around two sides of the inductors and fixing the copper foil through tin soldering. 
     However, the above technology has at least the following defects: The copper foil covers the two symmetrical terminals only, and other positions are not covered, causing defects such as a small shielding range and poor shielding effect. Due to the small coverage, the inductor radiates a large magnetic field to the outside and produces radiation to the external environment. 
     SUMMARY 
     Given this, the purpose of this application is to propose an inductor, an inductor fabrication method, and a power supply circuit containing the inductor to resolve prior-art problems such as small range and poor effect of electromagnetic shielding and potential instability of the inductor, thereby achieving a better electromagnetic shielding effect and keeping the potential of the inductor stable. 
     This application provides an inductor including an encapsulation shell with an inductive component encapsulated inside; an input electrode exposed on a surface of the encapsulation shell and configured to receive an alternating voltage; an output electrode exposed on the surface of the encapsulation shell and configured to output a direct current voltage, where the input electrode and the output electrode are electrically isolated by the encapsulation shell; and a metal shield layer asymmetrically covering the surface of the encapsulation shell and electrically connected to the output electrode, where the metal shield layer keeps the input electrode electrically isolated from the output electrode. 
     Further, the metal shield layer covers at least one surface of the encapsulation shell. 
     Further, the input electrode is exposed on the bottom surface of the encapsulation shell, the output electrode is exposed on the same bottom surface of the encapsulation shell as the input electrode, and the metal shield layer covers at least part or all of the top surface of the encapsulation shell opposite to the bottom surface. 
     Further, the encapsulation shell is a flat cuboid, and the bottom surface and the top surface each have an area larger than the other sides of the cuboid. 
     Further, the metal shield layer extends from the top surface of the flat cuboid to the bottom surface along a side adjacent to the output electrode until contacting the output electrode. 
     Further, the metal shield layer covers areas including the top surface of the flat cuboid, a part of the bottom surface on which the output electrode is located, and the side adjacent to, but not in contact with, the output electrode. The three areas make the metal shield layer connected as a whole. 
     Further, the metal shield layer extends from the top surface of the flat cuboid to the bottom surface along multiple sides, avoids the input electrode, and contacts the output electrode. 
     Further, the metal shield layer covers areas including the top surface of the flat cuboid, a part of the bottom surface on which the output electrode is located, a side adjacent to, but not in contact with, the output electrode, and a part or all of the two sides in contact with the output electrode. A part of the metal shield layer covering the two sides in contact with the output electrode avoids the input electrode, such that the output electrode and the input electrode are electrically isolated. 
     As a purpose of this application, an inductor fabrication method is further provided including the following steps: 
     encapsulating an inductive component to form an encapsulation shell and exposing an input electrode and an output electrode on the bottom surface of the encapsulation shell; 
     electroplating a metal layer on the encapsulation shell; and 
     patterning the electroplated metal layer to form a metal shield layer, where 
     the metal shield layer asymmetrically covers the surface of the encapsulation shell after patterning and covers at least a top surface of the encapsulation shell opposite to the bottom surface, and the metal shield layer keeps the input electrode electrically isolated from the output electrode. 
     Further, the metal shield layer is in electrical contact with the output electrode, such that the potential of the metal shield layer is the same as the potential of the output electrode. 
     As another purpose of this application, a power supply circuit is further provided, including a power circuit configured to provide an alternating voltage; the inductor described above, where an input electrode of the inductor receives the alternating voltage output by the power circuit; and a circuit constituting a loop of the power circuit and the inductor. 
     Compared with the prior art, the benefits of this application include: The metal shield layer provided on the encapsulation shell significantly increases the shielding area of the inductor, such that the inductor has a better electromagnetic shielding effect, not only preventing external EMI but also minimizing the EMI caused by the inductor to the outside while maintaining a stable potential. In addition, the inductor fabrication process of this application is simple and reliable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings described here are provided for further understanding of the present disclosure and constitute a part of this application. The exemplary examples and illustrations thereof of the present disclosure are intended to explain the present disclosure without forming inappropriate limitations to the present disclosure. In the accompanying drawings: 
         FIG.  1    is a schematic diagram of a power supply circuit according to this application; 
         FIGS.  2 A and  2 B  are schematic composition diagrams of an inductor; 
         FIGS.  3 A and  3 B  are schematic diagrams of a metal shield layer and an encapsulation shell; and 
         FIG.  4    is a flowchart of an inductor fabrication method. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The embodiments of this application provide an inductor, an inductor fabrication method, and a power supply circuit containing an inductor to resolve prior-art problems such as small range and poor effect of electromagnetic shielding and potential instability of the inductor, thereby achieving a better electromagnetic shielding effect and keeping the potential of the inductor stable. 
     The technical solution in the embodiments of this application is intended to resolve the above-mentioned problems in the prior art, and the general idea is as follows: 
     Metal shield layer  125  is provided on the surface of encapsulation shell  121  to ensure that at least part of output electrode  123  of inductor  12  is covered by the metal shield layer  125  while the input electrode  122  is electrically isolated from the output electrode  123 , that is, a current received by the input electrode  122  is not directly transmitted to the output electrode  123 . In addition, the encapsulation material between the input electrode  122  and the output electrode  123  is also provided with an area mostly covered by the metal shield layer  125 , and a device (such as a magnetic core) disposed between the input electrode  122  and the output electrode  123  may also be wrapped by the metal shield layer  125  to prevent other components in the power supply circuit from causing EMI to the magnetic core, such that the inductor  12  can maintain a stable potential. 
     The present disclosure is described in detail below with reference to various implementations shown in the accompanying drawings, but these implementations are not intended to limit this application, and functions, methods, or structural equivalent transformations or replacements made by those of ordinary skill in the art according to these implementations fall within the protection scope of this application. 
     As shown in  FIG.  1   , this application provides power supply circuit  100 . The power supply circuit  100  includes power circuit  11 , inductor  12 , and a circuit constituting a loop of the power circuit  11  and the inductor  12 . The loop may further include a capacitor and other components. The power circuit  11  is configured to provide an alternating voltage, and the inductor  12  and the capacitor receive the alternating voltage and convert it to a direct current voltage and output to a subsequent circuit. 
     As shown in  FIGS.  2 A and  2 B , the inductor  12  includes encapsulation shell  121 , input electrode  122 , output electrode  123 , and metal shield layer  125 . Inductive component  124  is encapsulated inside the encapsulation shell  121 , and the input electrode  122  is exposed on the surface of the encapsulation shell  121  and configured to receive the alternating voltage output by the power circuit  11 . The output electrode  123  is configured to output a direct current voltage, the output electrode  123  and the input electrode  122  are exposed on the surface of the encapsulation shell  121 , and the encapsulation shell  121  electrically isolates the input electrode  122  from the output electrode  123 . The metal shield layer  125  asymmetrically covers the surface of the encapsulation shell  121 , the metal shield layer  125  is in electrical contact with the output electrode  123 , and the metal shield layer  125  keeps the input electrode  122  electrically isolated from the output electrode  123 . The metal shield layer  125  is provided to ensure a good electromagnetic shielding effect of the inductor  12  and can reduce the size of the inductor  12 , thereby facilitating the miniaturization of the inductor  12  and reducing the difficulty of arranging the inductor  12  in the circuit. 
     It should be noted that if the coverage of the metal shield layer  125  is too large and a current is transmitted between the input electrode  122  and the output electrode  123  through the metal shield layer  125 , there is no electrical isolation between the input electrode  122  and the output electrode  123 . In this case, the inductor  12  is easily short-circuited, or there is a risk of current breakdown for the inductor  12 . To prevent the inductor  12  from being short-circuited by the metal shield layer  125 , the metal shield layer  125  keeps the input electrode  122  electrically isolated from the output electrode  123 , that is, spacing needs to be maintained between the metal shield layer  125  covering the input electrode  122  and the metal shield layer  125  covering the output electrode  123 . The spacing keeps the input electrode  122  electrically isolated from the output electrode  123 , thus allowing the inductor  12  to operate normally. 
     In an implementation, the input electrode is exposed on one side of the encapsulation shell, the output electrode is exposed on another side of the encapsulation shell opposite to the input electrode, and the metal shield layer covers at least a part of two bottom surfaces of the encapsulation shell adjacent to the side on which the output electrode is located. In this implementation, the metal shield layer covers the side on which the output electrode is located and the bottom surface adjacent to the side on which the output electrode is located and can be electrically connected to the output electrode. Such a setting is conducive to expanding the coverage of the metal shield layer  125 , such that the metal shield layer  125  can have a better electric field shielding effect. 
     In an implementation, the metal shield layer  125  covers at least one surface of the encapsulation shell  121 , and such an arrangement enables the metal shield layer  125  to isolate, from at least one direction, the radiation of the external electric field to the inductor  12  or the radiation of the internal electric field of the inductor  12  to the outside. The arrangement is also conducive to expanding the coverage of the metal shield layer  125 , such that the metal shield layer  125  can have a better electric field shielding effect. In this implementation, the input electrode  122  is exposed on the bottom surface of the encapsulation shell  121 , the output electrode  123  is exposed on the same bottom surface of the encapsulation shell  121  as the input electrode  122 , and the metal shield layer  125  covers at least part or all of the top surface of the encapsulation shell  121  opposite to the bottom surface. 
     In an implementation, the encapsulation shell  121  is a flat cuboid, and the encapsulation shell  121  may be made of magnetic material or other materials, which is not limited in this embodiment. The flat cuboid covers the input electrode  122 , the inductive component  124 , and the output electrode  123 ; the input electrode  122  is disposed on a side of the encapsulation shell  121 ; the output electrode  123  is disposed on a side of the encapsulation shell  121  away from the input electrode  122 ; the inductive component  124  is disposed between the input electrode  122  and the output electrode  123 . The bottom surface of the encapsulation shell  121  and the opposite top surface each have an area larger than the other sides of the flat cuboid. In an implementation, the metal shield layer  125  covers the top surface of the flat cuboid, and the metal shield layer  125  extends from the top surface to the bottom surface along the side near the output electrode  123  until it contacts the output electrode  123  exposed on the bottom surface, such that the potential of the metal shield layer  125  is the same as that of the output electrode  123 . The metal shield layer  125  extends from the top surface to the side adjacent to, but not in contact, with the output electrode  123 . In this way, the metal shield layer  125  covers areas including the top surface of the flat cuboid, a part of the bottom surface on which the output electrode  123  is located, and the side adjacent to, but not in contact with, the output electrode  123 . The three areas make the metal shield layer  125  connected as a whole, such that the coverage of the metal shield layer  125  can increase as much as possible, and the inductor  12  can have a better electric field shielding effect and reduce the radiation of the inductor  12  to the external environment. In the prior art, the copper foil usually covers the side near the input electrode  122  and the side near the output electrode  123 , while the inductive component  124  between the input electrode  122  and the output electrode  123  is not covered. Consequently, the magnetic force entering the inductor  12  from outside easily affects the inductive component  124 , and the inductive component  124  generates the near field, thus changing the internal potential difference of the inductor  12 , resulting in an unbalanced electron transfer in the inductor  12 . In contrast, the metal shield layer  125  in this application covers a larger area on the surface of the encapsulation shell  121 . The metal shield layer  125  can isolate the electric field from the outside and also prevent the near field generated inside the inductor  12  from radiating to the outside. The alternating voltage received by the input electrode  122  in this application passes the inductive component  124  and then is output by the output electrode  123 . In this case, the voltage output by the output electrode  123  is a stable direct current voltage, that is, there is no induced electromotive force generated at the output electrode  123 . The metal shield layer  125  near the output electrode  123  is in contact with the output electrode  123  exposed on the bottom surface of the encapsulation shell  121 , such that the metal shield layer  125  has the potential same as that of the output electrode  123 . Because the input electrode  122  receives the alternating voltage from the power circuit  11 , an alternating electric field is generated on the inductor  12 , which is shielded by a stable potential or zero potential. The metal shield layer  125  is electrically connected to the output electrode  123 , such that the metal shield layer  125  has a relatively stable potential, and thus can shield the outward radiation of the alternating electric field. In this way, the energy of the alternating electric field can be suppressed and the impact of the inductor  12  on the external environment is greatly reduced. 
     As shown in  FIGS.  3 A and  3 B , in another implementation, the metal shield layer  125  extends from the top surface of the flat cuboid to the bottom surface along multiple sides of the flat cuboid. On a side adjacent to the input electrode  122 , the metal shield layer  125  avoids the input electrode  122 , and on a side adjacent to the output electrode  123 , the metal shield layer  125  contacts the output electrode  123 , such that the potential of the metal shield layer  125  is the same as that of the output electrode  123 . In this way, the metal shield layer  125  covers areas including the top surface of the flat cuboid, a part of the bottom surface on which the output electrode  123  is located, a side adjacent to, but not in contact with, the output electrode  123 , and all or part of two sides in contact with the output electrode  123 . Spacing is kept between the input electrode  122  and the metal shield layer  125  covering the two sides in contact with the output electrode  123 , such that the output electrode  123  is electrically isolated from the input electrode  122 . During the operation of the inductor  12 , when the current input via the input electrode  122  passes the inductive component  124 , the inductive component  124  generates a changing magnetic field. When the magnetic field moves toward the top surface of the flat cuboid, the magnetic field meets the metal shield layer  125 , and eddy currents are generated, which counteract the changes in the magnetic field. The top surface of the flat cuboid can counteract most of the magnetic field generated by the inductive component  124  because the metal shield layer  125  covers the top surface. This greatly reduces the magnetic field radiated to the outside by the inductive component  124 , thus reducing the magnetic field interference from the inductor  12  to the outside. 
     The input electrode  122  is provided on the bottom surface of the flat cuboid, the input electrode  122  is at least partially exposed on the bottom surface of the flat cuboid, and the input electrode  122  is located on a side of the inductive component  124 . The input electrode  122  is made of conductive material. In an implementation, the input electrode  122  may be a copper foil solder pin made of copper foil, and the copper foil solder pin may be a plug-in pin soldered to the flat cuboid or a surface-mounted device (SMD) soldered to the flat cuboid, which is not specifically limited in this embodiment. 
     The output electrode  123  is also provided on the bottom surface of the flat cuboid, the output electrode  123  is at least partially exposed on the bottom surface of the flat cuboid, and the output electrode  123  is located on a side of the inductive component  124  away from the input electrode  122 . The output electrode  123  is made of conductive material. In an implementation, the input electrode  122  may be a copper foil solder pin made of copper foil, and the copper foil solder pin may be a plug-in pin soldered to the flat cuboid or an SMD soldered to the flat cuboid, which is not specifically limited in this embodiment. 
     The inductive component  124  is located between the input electrode  122  and the output electrode  123 , and a terminal of the inductive component  124  is connected to the input electrode  122 , and the other terminal of the inductive component  124  is connected to the output electrode  123 . 
     As shown in  FIG.  4   , this application further proposes a fabrication method for the inductor  12  described above, including the following steps: 
     encapsulating inductive component  124  to form encapsulation shell  121  and exposing input electrode  122  and output electrode  123  on the bottom surface of the encapsulation shell  121 ; 
     electroplating a metal layer on the encapsulation shell  121 ; and 
     patterning the electroplated metal layer to form the metal shield layer  125 . 
     The metal shield layer  125  asymmetrically covers the surface of the encapsulation shell  121  after patterning and covers at least a top surface of the encapsulation shell  121  opposite to the bottom surface, and the metal shield layer  125  keeps the input electrode  122  electrically isolated from the output electrode  123 . 
     The metal shield layer  125  is in electrical contact with the output electrode  123 , such that the potential of the metal shield layer  125  is the same as that of the output electrode  123 . The metal shield layer  125  may be in a mesh structure or other graphic structures. 
     The inductor  12  provided in this application is made through the method described above. According to the fabrication method, a metal layer is deposited on the surface of the encapsulation shell  121  through electroplating, and then the metal layer is patterned to form the metal shield layer  125  covering the top surface of the encapsulation shell  121 . The coverage of the metal shield layer  125  is increased as much as possible, and the input electrode  122  is electrically isolated from the output electrode  123 . The traditional method usually winds the copper foil through manual operation, which causes low production efficiency and is not conducive to production automation. Compared with the prior art, the fabrication method proposed in this application can improve production efficiency. In addition, the inductor  12  fabricated in this method has a better anti-interference ability, maximizes the shielding effect, maintains a stable potential, and reduces the risk of open or short circuits. 
     In the claims, “comprise” does not exclude other units or steps, and “a” or “an” does not exclude plural cases. In the claims, ordinal words such as “first” and “second” describing claim elements do not mean that a claim element has priority, order, or chronological order over another claim element, of performance of the action, but merely to distinguish one claim element from another. Although some specific technical features are documented separately in distinct dependent claims, this does not mean that these specific technical features cannot be utilized in combination. Aspects of the present disclosure may be used individually, in combination, or in various arrangements not specifically described in the embodiments above, so as not to limit their application to the details and arrangement of the components described before or shown in the accompanying drawings. For example, multiple aspects described in one embodiment may be used in any manner in combination with multiple aspects described in other embodiments. The steps, functions, or features documented in a plurality of modules or units may be performed or satisfied by a single module or a single unit. The steps of the method disclosed herein are not limited to being performed in any particular order, and it is possible to perform some or all of the steps in other orders. Any reference numeral in the claims should not be considered as limiting on the involved claims. 
     Although preferred embodiments of this application have been disclosed for exemplary purposes, those of ordinary skill in the art should realize that various improvements, additions, and substitutions are possible without departing from the scope and spirit of this application as disclosed by the appended claims.