Abstract:
An electronic device is provided, which includes: a magnetically conductive element having at least a through hole; a conductor structure formed on the magnetically conductive element and in the through hole; and a base body encapsulating the magnetically conductive element and the conductor structure, thereby allowing the electronic device to generate a higher magnetic flux and thus cause an increase in inductance.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to electronic devices, and more particularly, to an electronic device having a magnetically conductive element. 
         [0003]    2. Description of Related Art 
         [0004]    Along with the rapid development of electronic industries, electronic products are developed toward the trend of multi-function and high performance. To meet the miniaturization requirement of semiconductor packages, packaging substrates for carrying chips are becoming thinner. Further, the chips are required to have high-integration electronic circuits and high-density I/O connections to increase memory capacities and operating frequencies and reduce voltage requirements, thereby allowing the electronic products to become lighter, thinner, shorter, smaller and faster. 
         [0005]    In semiconductor application devices such as communication or high-frequency semiconductor devices, most RF passive elements such as resistors, inductors, capacitors and oscillators are electrically connected to semiconductor chips so as to cause the semiconductor chips to have certain current characteristics or send signals 
         [0006]    For example, in a BGA (Ball Grid Array) semiconductor device, most passive elements are mounted on a surface of a substrate. However, to prevent the passive elements from adversely affecting the electrical connection and configuration between semiconductor chips and bonding pads of the substrate, the passive elements are generally mounted at corners of the substrate or a region outside the chip mounting region. 
         [0007]    Such a limitation on the position of the passive elements reduces the routing flexibility. Further, the position of the bonding pads limits the number of the passive elements mountable on the substrate, thereby hindering high integration of the semiconductor device. Furthermore, as the high-performance requirement of the semiconductor package causes a great increase in the number of the passive elements, the surface area of the substrate must be increased to accommodate both the semiconductor chips and the passive elements. As such, the semiconductor package is increased in volume and cannot meet the miniaturization requirement. 
         [0008]    To overcome the above-described drawbacks, most passive elements are fabricated as lumped elements, for example, chip-type inductors, and integrated at regions between the semiconductor chips and the bonding pads.  FIG. 1  is a schematic cross-sectional view of a conventional semiconductor package  1 . Referring to  FIG. 1 , a substrate  10  is provided and a circuit layer  11  having a plurality of bonding pads  110  is formed on the substrate  10 . A plurality of inductor elements  12  and a semiconductor chip  13  are mounted on the substrate  10 , and the semiconductor chip  13  is electrically connected to the bonding pads  110  through a plurality of bonding wires  130 . 
         [0009]    However, as the number of I/O connections per unit area of the semiconductor device increases, the number of the bonding wires  130  increases. Generally, the height of the inductor elements  12  (0.8 mm) is greater than the height of the semiconductor chip  13  (0.55 mm) As such, the bonding wires  130  easily come into contact with the inductor elements  12 , thereby causing a short circuit to occur. 
         [0010]    To overcome the drawback of short circuit, the wire loop of the bonding wires  130  needs to be pulled up and positioned over the inductor elements  12 . But such a method increases the bonding difficulty and complicates the fabrication process. Also, since the length of the wire loop of the bonding wires  130  is increased, the fabrication cost of the bonding wires  130  is increased significantly. In addition, if the bonding wires  130  lack an effective support, the bonding wires  130  easily sag under gravity and come into contact with the inductor elements  12 , thus causing a short circuit to occur. 
         [0011]    Further, the inductor elements  12 , especially those in power supply circuits, are chip-type and have a large volume. In addition, the parasitic effect increase as the distance between the inductor elements  12  and the semiconductor chip  13  increases. 
         [0012]    Referring to  FIG. 1 ′, the inductor elements  12  are replaced with coil-type inductors  12 ′ to overcome the above-described drawbacks. However, since the coil-type inductors  12 ′ are only mounted on the substrate  10 , the simulated inductance value of the inductors  12 ′ is 17 Nh (on an area of 2.0 mm×1.25 mm) As such, the inductance value of the coil-type inductors  12 ′ is too small to meet the requirement. 
         [0013]    Therefore, how to overcome the above-described drawbacks has become critical. 
       SUMMARY OF THE INVENTION 
       [0014]    In view of the above-described drawbacks, the present invention provides an electronic device, which comprises: a magnetically conductive element having a first surface, a second surface opposite to the first surface, an outer side surface adjacent to and connecting the first surface and the second surface, and at least a through hole communicating the first surface and the second surface; a conductor structure formed on the first surface, the second surface and the outer side surface of the magnetically conductive element and extending into the through hole for generating a magnetic flux; and a base body encapsulating the magnetically conductive element and the conductor structure. 
         [0015]    In the above-described electronic device, the base body can comprise a substrate and an encapsulant, wherein the magnetically conductive element and the conductor structure are positioned on the substrate and encapsulated by the encapsulant. 
         [0016]    In the above-described electronic device, the magnetically conductive element can be made of ferrite, Fe, Mn, Zn, Ni or an alloy thereof. 
         [0017]    In the above-described electronic device, the conductor structure can comprise a circuit layer formed on the first surface of the magnetically conductive element and a plurality of conductive wires formed over the second surface of the magnetically conductive element, wherein each of the conductive wires has two opposite ends electrically connected to the circuit layer. In an embodiment, the circuit layer has a plurality of conductive traces, and the two opposite ends of each of the conductive wires are electrically connected to different two of the conductive traces, respectively. 
         [0018]    In the above-described electronic device, the conductor structure can further comprise a plurality of bonding pads formed on the second surface of the magnetically conductive element, and each of the conductive wires can have two segments bonded to a corresponding one of the bonding pads, wherein one of the segments extends in the through hole of the magnetically conductive element for connecting the circuit layer and the bonding pad and the other segment extends over the outer side surface of the magnetically conductive element for connecting the circuit layer and the bonding pad. 
         [0019]    In an embodiment, the conductor structure further comprises a plurality of conductive posts formed on the circuit layer in the through hole of the magnetically conductive element, wherein one ends of the conductive wires are bonded to the conductive posts. 
         [0020]    In an embodiment, the conductor structure further comprises a plurality of conductive posts formed on the circuit layer at an outer periphery of the outer side surface of the magnetically conductive element, wherein one ends of the conductive wires are bonded to the conductive posts. Furthermore, a plurality of conductive posts can be formed on the circuit layer in the through hole of the magnetically conductive element, and the other ends of the conductive wires are bonded to the conductive posts in the through hole. 
         [0021]    In the above-described electronic device, the through hole can be a closed through hole or an open through hole. The open through hole can have at least an opening. 
         [0022]    According to the present invention, the conductor structure is formed around the magnetically conductive element having a through hole so as to generate a magnetic flux and thus cause an increase in inductance. 
         [0023]    Further, since the magnetically conductive element facilitates to increase the inductance value of a single coil, the present invention can achieve the same inductance value as the prior art by using a reduced number of coils. Therefore, the volume of the inductor is minimized. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0024]      FIGS. 1 and 1 ′ are schematic cross-sectional views of conventional semiconductor packages; 
           [0025]      FIG. 2  is a schematic cross-sectional view of an electronic device according to a first embodiment of the present invention; 
           [0026]      FIG. 2 ′ is a schematic partial perspective view of the electronic device of  FIG. 2 ; 
           [0027]      FIG. 3  is a schematic cross-sectional view of an electronic device according to a second embodiment of the present invention; 
           [0028]      FIGS. 4A to 4C  are schematic cross-sectional views of electronic devices according to a third embodiment of the present invention; 
           [0029]      FIG. 5  is a schematic upper view of an electronic device according to a fourth embodiment of the present invention; and 
           [0030]      FIGS. 6A to 6G  are schematic upper views of electronic devices according to a fifth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those in the art after reading this specification. 
         [0032]    It should be noted that all the drawings are not intended to limit the present invention. Various modifications and variations can be made without departing from the spirit of the present invention. Further, terms such as “first”, “second”, “on”, “a” etc. are merely for illustrative purposes and should not be construed to limit the scope of the present invention. 
         [0033]      FIGS. 2 and 2 ′ show an electronic device  2  according to a first embodiment of the present invention. 
         [0034]    Referring to  FIGS. 2 and 2 ′, the electronic device  2  has a magnetically conductive element  21 , a conductor structure  22  formed around the magnetically conductive element  21 , and a base body  20  encapsulating the magnetically conductive element  21  and the conductor structure  22 . 
         [0035]    The magnetically conductive element  21  has high permeability and is made of ferrite, Fe, Mn, Zn, Ni or an alloy thereof. The magnetically conductive element  21  has a first surface  21   a,  a second surface  21   b  opposite to the first surface  21   a,  an outer side surface  21   c  adjacent to and connecting the first surface  21   a  and the second surface  21   b,  and a through hole  210  communicating the first surface  21   a  and the second surface  21   b . Therefore, the magnetically conductive element  21  has a ring shape. The wall surface of the through hole  210  constitutes an inner side surface  21   d  of the magnetically conductive element  21 . 
         [0036]    The conductor structure  22  is formed on the first surface  21   a,  the second surface  21   b  and the outer side surface  21   c  of the magnetically conductive element  21  and extends into the through hole  210  so as to cause the conductor structure  22  and the magnetically conductive element  21  to generate a magnetic flux and cause the conductor structure  22  and the magnetically conductive element  21  to constitute an inductor. 
         [0037]    The base body  20  has a substrate  200  and an encapsulant  201 . The magnetically conductive element  21  and the conductor structure  22  are positioned on the substrate  200  and encapsulated by the encapsulant  201 . In particular, the substrate  200  is a ceramic substrate, a metal plate, a copper foil substrate, a circuit board, a wafer, a chip or a package. The encapsulant  201  is made of a molding compound and formed by molding. Further, the encapsulant  201  is filled in the through hole  210 . In addition, the substrate  200  can have internal circuits (not shown) and a plurality of conductive vias (not shown) formed in dielectric layers of the substrate  200  for electrically connecting the internal circuits. 
         [0038]    Further, an electronic element can be disposed on the substrate  200  of the base body  20 . The electronic element can be an active element such as a semiconductor chip, a passive element such as a resistor, a capacitor or an inductor, or a combination thereof. 
         [0039]    In the present embodiment, the conductor structure  22  has a circuit layer  220  formed on the first surface  21   a  of the magnetically conductive element  21  and a plurality of conductive wires  221  formed over the second surface  21   b  of the magnetically conductive element  21 . Each of the conductive wires  221  has two opposite ends  221   a,    221   b  electrically connected to the circuit layer  220  in a manner that the conductor structure  22  is formed with a plurality of coils connected in series and positioned around the ring-shaped magnetically conductive element  21 . 
         [0040]    In particular, the conductive wires  221  are bonding wires such as gold wires and formed by a wire bonding process. The circuit layer  220  is made of copper. By performing a sputtering, coating or electroplating process, the circuit layer  220  is formed on the dielectric layer of the substrate  200  and electrically connected to the internal circuits and the conductive vias of the substrate  200 . 
         [0041]    In the present embodiment, two conductive wires  221  are provided at a single wire bonding position. In other embodiments, one or more than two conductive wires can be provided at a single wire bonding position. 
         [0042]    Further, the circuit layer  220  has a plurality of conductive traces  220   a,    220   b.  The two opposite ends  221   a,    22   b  of each of the conductive wires  221  are electrically connected to different two of the conductive traces  220   a,    220   b,  respectively. 
         [0043]    In addition, the conductive wires  221  extend from the circuit layer  220  at an outer periphery of the outer side surface  21   c  of the magnetically conductive element  21 , over the second surface  21   b  of the magnetically conductive element  21 , to the circuit layer  220  in the through hole  210 . 
         [0044]    In other embodiments, the base body  20  can be a dielectric layer (not shown) made of a dielectric material. The dielectric material is filled in the through hole  210  to embed the magnetically conductive element  21  in the dielectric layer, and the circuit layer  220  is formed in the dielectric layer. 
         [0045]      FIG. 3  is a schematic cross-sectional view of an electronic device  3  according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in the configuration of the conductor structure  32 . 
         [0046]    Referring to  FIG. 3 , the conductor structure  32  further has a plurality of bonding pads  320  formed on the second surface  21   b  of the magnetically conductive element  21 . Each of the conductive wires  321  has a first segment  321   a  and a second segment  321   b  bonded to a corresponding one of the bonding pads  320 . In particular, the first segment  321   a  extends in the through hole  210  of the magnetically conductive element  21  for connecting the circuit layer  220  and the bonding pad  320 , and the second segment  321   b  extends over the outer side surface  21   c  of the magnetically conductive element  21  for connecting the circuit layer  220  and the bonding pad  320 . 
         [0047]    In the present embodiment, the bonding pads  320  are made of copper and formed by a routing process. 
         [0048]      FIGS. 4A to 4C  are schematic cross-sectional views of electronic devices  4 ,  4 ′,  4 ″ according to a third embodiment of the present invention. The third embodiment differs from the first embodiment in the configuration of the conductor structures  42 ,  42 ′,  42 ″. 
         [0049]    Referring to  FIG. 4A , the conductor structure  42  further has a plurality of conductive posts  420  formed on the circuit layer  220  in the through hole  210  of the magnetically conductive element  21 , and one ends  221   a  of the conductive wires  221  are bonded to the conductive posts  420 . 
         [0050]    Referring to  FIG. 4B , the conductor structure  42 ′ further has a plurality of conductive posts  420 ′ formed on the circuit layer  220  at an outer periphery of the outer side surface  21   c  of the magnetically conductive element  21 , and one ends  221   b  of the conductive wires  221  are bonded to the conductive posts  420 ′. 
         [0051]    Referring to  FIG. 4C , the conductor structure  42 ″ further has a plurality of conductive posts  420 ″ formed on the circuit layer  220  in the through hole  210  and at an outer periphery of the outer side surface  21   c  of the magnetically conductive element  21 . One ends of the conductive wires  221  are bonded to the conductive posts  420 ″ formed on the circuit layer  220  in the through hole  210  and the other ends of the conductive wires  221  are bonded to the conductive posts  420 ″ formed at the outer periphery of the outer side surface  21   c  of the magnetically conductive element  21 . 
         [0052]    In the present embodiment, the conductive posts  420 ,  420 ′,  420 ″ are made of copper and formed by a routing process. 
         [0053]    In the electronic device  2 ,  3 ,  4 ,  4 ′,  4 ″, the magnetically conductive element  21  is provided with a through hole  210  to allow the conductor structure  22 ,  32 ,  42 ,  42 ′,  42 ″ to be formed around the magnetically conductive element  21 . As such, the magnetic field tends to focus on a ferromagnetic path of low magnetic reluctance, thereby increasing the magnetic flux and resulting in an increase in inductance. The inductance value of the present invention can be increased to 75 nH, which is far greater than the conventional inductance value of 17 nH. 
         [0054]    Further, since the magnetically conductive element  21  having the through hole  210  facilitates to increase the inductance value of a single coil, the present invention can achieve the same inductance value as the prior art by using a reduced number of coils. For example, compared with the conventional coil-type inductor that needs three coils to achieve an inductance value of 17 nH, the present invention only needs one coil to achieve the inductance value of 17 nH. 
         [0055]    By reducing the number of coils, the present invention reduces the volume of the inductor constituted by the conductor structure  22 ,  32 ,  42 ,  42 ′,  42 ″ and the magnetically conductive element  21 . Further, since the magnetically conductive element  21  has no circuit formed therein, the volume of the magnetically conductive element  21  can be reduced according to the practical need. Therefore, the inductor of the present invention meets the miniaturization requirement. 
         [0056]    Compared with the prior art, the electronic device  2 ,  3 ,  4 ,  4 ′,  4 ″ of the present invention occupies less space and achieves a larger inductance value. 
         [0057]      FIG. 5  and  FIGS. 6A to 6G  are schematic upper views of electronic devices according to fourth and fifth embodiments of the present invention. The fourth and fifth embodiments differ from the first embodiment in the configuration of the magnetically conductive element. 
         [0058]    Referring to  FIG. 5 , the magnetically conductive element  51  has a plurality of through holes  510 . In the present embodiment, the magnetically conductive element  51  has two through holes and has a “         ” shape in upper view. In other embodiments, the magnetically conductive element  51  can have more through holes and have such as a “         ” shape in upper view. 
         [0059]    Referring to  FIGS. 6A to 6G  different from the closed through hole  210  of the magnetically conductive element  21  of the first embodiment, the magnetically conductive element  61  of the fifth embodiment has one or more open through holes  610 ′. For example, referring to  FIG. 6A , the magnetically conductive element  61  has one open through hole  610 ′ having one opening  610   a.  Referring to  FIGS. 6B and 6C , the magnetically conductive element  61  has one open through hole  610 ′ having a plurality of openings  610   a.  Referring to  FIGS. 6D and 6E , the magnetically conductive element  61  has a plurality of open through holes  610 ′ each having a plurality of openings  610   a . Referring to  FIG. 6F , the magnetically conductive element  61  has two open through holes  610 ′ having a common opening  610   a.  Referring to  FIG. 6G  the magnetically conductive element  61  has a closed through hole  610  and an open through hole  610 ′ having an opening  610   a.    
         [0060]    The above-described descriptions of the detailed embodiments are only to illustrate the preferred implementation according to the present invention, and it is not to limit the scope of the present invention. Accordingly, all modifications and variations completed by those with ordinary skill in the art should fall within the scope of present invention defined by the appended claims.