Patent Publication Number: US-6992556-B2

Title: Inductor part, and method of producing the same

Description:
This application is a U.S. National Phase application of PCT International application PCT/JP02/02115. 
   TECHNICAL FIELD 
   The present invention relates to an inductor device including an inductor for use in various consumer equipment for noise filtering, and to a method of manufacturing the device. 
   BACKGROUND ART 
     FIG. 9  is an exploded perspective view of a conventional inductor device,  FIG. 10  is the perspective view of the device, and  FIG. 11  shows impedance-frequency characteristics of the device. 
   The conventional inductor device includes a magnetic section  1  made of magnetic material, a coil pattern formed of a spiral conductive portion  2  in the magnetic section  1 , and an external electrode  3  coupled to the coil pattern electrically. 
   Plural magnetic layers  4  are laminated to form the magnetic section  1 . Each magnetic layer  4  is provided with the spiral conductive portion  2  of the coil pattern having an arc shape of less than one turn. Arc-shaped conductive portions  2  on magnetic layers  4  are electrically coupled through a via-hole  5 , thus providing the coil pattern of a few turns in the magnetic section  1 . 
   Conductive portion  2  functions as a common-mode choke coil.  FIG. 11  shows impedance-frequency characteristics of the choke coil. 
   In the conventional inductor device, magnetic section  1  includes plural magnetic layers  4  each having arc-shaped conductive portion  2  thereon are laminated to form the coil pattern in the magnetic section. Therefore, the magnetic material of magnetic section  1  is disposed between conductive portions  2  adjacent to each other on magnetic layers  4  adjacent to each other. Magnetic permeability between conductive portions  2  increases since the layers sandwiches magnetic layer  4 , thus increases magnetic flux passing through inside of conductive portion  2  (leakage flux). Magnetic flux passing through the coil pattern decreases accordingly, and this decreases an impedance and resulting insufficient attenuation. 
   Magnetic material having high permeability generally increases the magnetic flux around the coil pattern, and thus, increase the impedance for preventing attenuation from decreasing. 
   However, the magnetic material having the high permeability decreases attenuation properties at a high frequency band since a peak of the impedance shifts to a lower frequency band. As shown in the impedance-frequency characteristics in  FIG. 11 , the inductor device, being used especially as a common mode choke coil, have its attenuation properties decrease in a high frequency band since a peak impedance  6  for a common-mode current, i.e., a noise component, shifts to a lower frequency band. In addition, since a peak impedance  7  for a normal-mode current, i.e., an information signal component, shifts to a lower frequency band, the information signal component attenuates in a lower frequency band. 
   Magnetic layers  4  are pressed against the coil patterns in their laminating process. For this process, a cross-section of the conductive portion must have a stripe shape having its lateral size smaller than its thickness, so that magnetic layer  4  may be placed easily between conductive portions  2  of the coil pattern. 
   This configuration, however, increases an area of conductive portions  2  placed on magnetic layers  4  facing each other, and generates stray capacitance in the area. The capacitance decreases the attenuation properties in a high frequency band since the peak impedance shifts to a lower frequency band. 
   As mentioned above, the conventional inductor device has the decreased attenuation properties in a high frequency band, and hardly have a low profile since a lot of magnetic layers  4  are necessarily be stacked to have the coil of only a few turns. 
   SUMMARY OF THE INVENTION 
   An inductor device includes an insulation substrate, a coil pattern including a spiral conductive portion on the insulation substrate, a magnetic section over the coil pattern, the magnetic section being disposed on the insulation substrate, and an external electrode coupled to the coil pattern. The conductive portion is formed through sintering conductive material on the insulation substrate together with the insulation substrate. 
   The inductor device exhibits excellent attenuation characteristics in a high frequency band and has a low profile because of the magnetic section being thin. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of an inductor device according to a first exemplary embodiment of the present invention. 
       FIG. 2  is a perspective view of the inductor device according to the first embodiment. 
       FIG. 3  is an enlarged cross-sectional view of part A of  FIG. 1  of the inductor device according to the first embodiment. 
       FIG. 4  is an enlarged cross-sectional view of part B in  FIG. 1  of the inductor device according to the first embodiment. 
       FIG. 5  is a plan view of an insulation substrate provided with a coil pattern in the inductor device according to the first embodiment. 
       FIG. 6  shows impedance-frequency characteristics of the inductor device according to the first embodiment. 
       FIG. 7  shows processes of manufacturing the inductor device according to the first embodiment. 
       FIG. 8  shows other processes of, manufacturing an inductor device according to a third exemplary embodiment of the invention. 
       FIG. 9  is an exploded perspective view of a conventional inductor device. 
       FIG. 10  is a perspective view of the conventional inductor device. 
       FIG. 11  shows impedance-frequency characteristics of the conventional inductor device. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   (First Exemplary Embodiment) 
     FIG. 1  is a cross-sectional view of an inductor device according to a first exemplary embodiment of the present invention.  FIG. 2  is a perspective view of the inductor device.  FIG. 3  is an enlarged cross-sectional view of part A of  FIG. 1  of the inductor device.  FIG. 4  is an enlarged cross-sectional view of part B in  FIG. 1  of the inductor device.  FIG. 5  is a plan view of an insulation substrate provided with a coil pattern in the inductor device.  FIG. 6  shows impedance-frequency characteristics of the inductor device.  FIG. 7  shows processes of manufacturing the inductor device. 
   As shown in FIG.  1  through  FIG. 5 , the inductor device according to the first embodiment has outside dimensions of 0.5 mm to 1.6 mm in length, 1.0 mm to 3.2 mm in width, and 0.9 mm to 1.2 mm in height. The device includes insulation substrate  10  composed of Ni-based ferrite having a relative permeability of approximately 650, spiral coil pattern  13  formed of conductive portion  12  composed of Ag on insulation substrate  10 , magnetic section  15  composed of Ni-based ferrite having a relative permeability of approximately 100 on insulation substrate  10 , and external electrode  17  electrically coupled to coil pattern  13  via lead-out electrode  30 . 
   Insulation substrate  10  has a thickness (H 1 ) larger than a thickness (H 2 ) of magnetic section  15  but smaller than three times the thickness (H 2 ). Conductive portion  12  is shaped spirally in not less than two turns. A gap between portions adjacent to each other of conductive portion  12  has a width (W 1 ) larger than half of the width (W 2 ) of the conductive portion but smaller than twice the width (W 2 ). 
   Non-magnetic section  23  made of non-magnetic material, such as non-crystallized glass, is formed around conductive portion  12  of coil pattern  13  to surround coil pattern  13 . The non-magnetic material infiltrates into magnetic section  15  to form a non-magnetic layer at a portion of the section  15  adjoining to non-magnetic section  23 . 
   First protective glass  25  made of crystallized glass is laminated on a surface of insulation substrate  10  opposite to coil pattern  13 . Second protective glass  27  made of crystallized glass is laminated in parallel with first protective glass  25  on magnetic section  15  on insulation substrate  10 . 
   A via-hole provided in magnetic section  15  is filled with conductive paste composed of Ag to form via-portion  29  which couples coil pattern  13  to external electrode  17  electrically. 
   Plural magnetic layers  31  each having a through-hole are laminated to form magnetic section  15 . Plural via-layers  32  formed through filling the through-holes with the conductive paste are laminated to form via-portion  29 . Edge  34  of via-layer  32  protrudes between through-hole peripheries  33  each located between magnetic layers  31  adjoining to each other. 
   Through-hole peripheries  33  of magnetic layers  31  and edges  34  of via-layers  32  are laminated alternately. 
     FIG. 6  shows impedance-frequency characteristics of the inductor device. Especially in case that the inductor device having coil pattern  13  formed of conductive portion  12  of two turns is used as a common mode choke coil, impedance  35  for a common mode current, i.e., a noise component, shifts to a higher frequency band compared with conventional inductor devices. And impedance  36  for a normal mode current, i.e., an information signal component, is small within a range covering lower to higher frequency bands,. That is, the inductor device has impedance  36  for the normal mode current, i.e., the information signal component, not reduced in a higher frequency band, while the device has impedance  35  for the common mode current, i.e., the noise component. Therefore, the inductor device has an advantage in transferring a information signal at a high speed of some hundreds Mbps in a high frequency band of approximately 1 GHz. 
   As shown in  FIG. 7 , a method of manufacturing the inductor device includes insulation-substrate-forming process  11  to form insulation substrate  10 , coil-forming process  14  to form coil pattern  13 , having spiral conductive portion  12  on insulation substrate  10 , magnetic-section-forming process  16  to forming magnetic section  15  on insulation substrate  10 , external-electrode-forming process  18  to form external electrode  17 , and coupling process  19  to couple coil pattern  13  to external electrode  17  electrically. 
   Insulation-substrate-forming process  11  includes insulation-substrate-sintering process  20  to sinter insulation substrate  10  before coil-forming process  14 . Magnetic-section-forming process  16  includes magnetic-section-sintering process  21  to sinter laminated magnetic section  15 . 
   Coil-forming process  14  includes intaglio-printing process in which a printing substrate having a spiral recess filled with conductive paste is stacked on insulation substrate  10 , the conductive paste is transferred onto insulation substrate  10 , and the conductive paste with insulation substrate  10  is sintered to form coil pattern  13  on a surface of insulation substrate  10 . 
   In non-magnetic-section-forming process  24  after coil-forming process  14 , non-magnetic section  23  is formed of non-magnetic material, such as non-crystallized glass, around conductive portion  12  of coil pattern  13  to surround pattern  13 . 
   In first-protective-glass-forming process  26  after magnetic-section-forming process  16 , first protective glass  25  is stacked on a surface of insulation substrate  10  opposite to printed coil patterns  13 , and is then sintered. In second-protective-glass-forming process  28 , second protective glass  27  is applied on magnetic section  15  on insulation substrate  10  in parallel with first protective glass  25 , and is the sintered. 
   In coupling process  19 , a via-hole is formed in magnetic section  15  and is filled with conductive paste to form via-portion  29 , which couples coil pattern  13  to external electrode  17  electrically. Then, coil pattern  13  is electrically coupled to lead-out electrode  30  through via-portion  29 . 
   Plural magnetic layers  31  each having a through-hole formed therein are laminated to form magnetic section  15 . Plural via-layers  32  each formed through filling the through-hole with conductive paste are laminated to form via-portion  29 . Edges  34  of via-layers  32  protrude between through-hole peripheries  33  of magnetic layers  31  adjoining to each other. Through-hole peripheries  33  of magnetic layers  31  and edges  34  of via-layers  32  are laminated alternately. 
   Above configure and manufacture processes provide the inductor device with coil pattern  13  having very high-density spiral conductive portion  12  easily. Especially since coil pattern  13  is not divided or formed on different layers in magnetic section  15 , whole coil pattern  13  is formed on a single surface. Therefore, magnetic section  15  is not disposed between conductive portions  12  adjacent to each other. This arrangement decreases magnetic flux passing through conductive portions  12  (leakage flux), and increase magnetic flux traveling the coil pattern accordingly. In addition, coil pattern  13  exhibits a strong magnetic coupling, which prevents its attenuation from decreasing. 
   Magnetic section  15  formed of magnetic material with a low magnetic permeability shifts a peak impedance to a lower frequency band, thus preventing attenuation properties from decreasing. 
   Magnetic section  15  formed of magnetic material with a low magnetic permeability generally shifts a peak impedance to a lower frequency band, and reduces attenuation properties. However, the strong magnetic coupling of coil patterns  13  prevents attenuation properties from decreasing, while a peak impedance shifts to a high frequency band. 
   Stray capacitance generated between conductive portions  12  adjacent to each other decreases according to the reduction of the area where conductive portions  12  faces each other since coil pattern  13  is formed on a single plane. Therefore, the inductor device has the peak impedance shifting to a higher frequency band, and has a low profile because of the thin dimensions of magnetic section  15 . 
   Non-magnetic section  23  is formed of non-magnetic material to enclose coil pattern  13  around conductive portion  12  of coil pattern  13 . Section  23  decreases magnetic permeability in conductive portion  12 , and increases magnetic flux traveling around non-magnetic section  23  enclosing coil patterns  13  since magnetic flux generated in coil pattern  13  is reduced significantly to pass through inside of conductive portion  12 , This makes magnetic coupling between conductive portion  12  of coil pattern  13  stronger, thus increasing attenuation properties. 
   The non-magnetic material, being especially made of glass, can not only reduce magnetic flux passing through conductive portion  12  of coil pattern  13 , resulting a stronger magnetic coupling, but also produces no hollow cavity in and around conductive portions  12  of coil pattern  13 . Therefore, conductive portion  12  can be prevented from corrosion or migration caused by, for example, moisture existing in air in the hollow cavity. 
   First protective glass  25  is laminated on a surface of insulation substrate  10  opposite to coil patterns  13 , and second protective glass  27  is laminated in parallel with first protective glass  25  on magnetic section  15  on insulation substrate  10 . These prevent the surface of insulation substrate  10  and the surface of magnetic section  15  from damage, such as cracks. 
   Since no hollow cavity is produced on a plane on which magnetic section  15  and via-portion contact to each other, via-portion  29  is prevented from corrosion due to, for example, moisture included in air in the hollow cavity. Via-layers  32  adjoining to each other are electrically coupled precisely even if respective through-holes of the adjoining layers of magnetic section  15  are not positioned correctly each other. Therefore, the inductor device has magnetic section  15  and via-portion  29  with predetermined thicknesses without incorrect electrical coupling. 
   Coil pattern  13  has spiral conductive portion  12  of not less than two turns. Conductive portion  12  has a gap between portions adjacent to each other having a width larger than ½ but smaller than twice of that of conductive portion  12 . This arrangement allows coil pattern  13  of plural turns on a single surface of insulation substrate  10  to be formed accurately without breakage or short-circuit, 
   The inductor device according to the first embodiment has outside dimensions of 0.5 mm to 1.6 mm in length, 1.0 mm to 3.2 mm in width and 0.9 mm to 1.2 mm in height. An inductor having a smaller dimensions, however, can includes coil pattern  13  accurately without breakage or short-circuit. 
   Insulation substrate  10  has a thickness larger than that of magnetic section  15  but smaller than three times the thickness of section  15 . This arrangement provides the inductor device with smaller outside dimensions precisely without breakage or short-circuit. 
   According to the first embodiment, since coil pattern  13  is formed on a single surface of insulation substrate  10 , magnetic section  15  is not sandwiched between conductive portions  12  adjacent to each other. Therefore, the inductor device exhibits an excellent attenuation properties in a higher frequency band, while having low profile because of thin magnetic section  15 . 
   Additionally, ceramics or insulation resin may be employed instead of the glass for the non-magnetic material in the inductor device according to the first embodiment. Non-magnetic section  23  can be provided only around conductive portion  12  of coil pattern  13 . This arrangement shortens magnetic flux passing around coil pattern  13 , thus reducing the noise component in a higher frequency band. 
   Coil pattern  13  having plural spiral conductive portion  12  can be applied to, for example, a common mode choke coil requiring plural conductive portion  12 . 
   Each of coil-forming process  14  and magnetic-section-forming process  16  is carried out only once according to the first embodiment, however, each process can be carried out plural times to laminate coil pattern  13  and magnetic section  15  alternatively. 
   (Second Exemplary Embodiment) 
   An inductor device according to a second exemplary embodiment is a modification of that of the first embodiment. The device has a hollow cavity instead of non-magnetic section  23 , and a non-magnetic layer where non-magnetic infiltrates into magnetic section  15  and insulation substrate  10  around the cavity. 
   A method of manufacturing the inductor device will be described. 
   In non-magnetic-section-forming process  24  of the first embodiment, a space in and around conductive portion  12  of coil pattern  13  is filled with glass as the non-magnetic material. During or after magnetic-sintering process  21 , the glass is liquefied at a temperature lower than a temperature at the sintering of magnetic section  15  to infiltrate into magnetic section  15  and insulation substrate  10 . Glass layers are formed around coil pattern  13 , while leaving a hollow cavity formed in and around conductive portion  12 . 
   According to the above configuration, glass filled in and around conductive portion  12  of coil pattern  13  as the non-magnetic material is liquefied to infiltrate into magnetic section  15  and insulation substrate  10 . This allows the hollow cavity formed in residual places to function as non-magnetic section  23 . 
   This arrangement decreases a magnetic permeability around conductive portion  12 , thus preventing magnetic flux generated in coil pattern  13  from passing around conductive portion  12 . Therefore, magnetic flux generated efficiently for traveling around coil pattern  13  induces strong magnetic coupling in conductive portion  12  and increases attenuation properties accordingly. 
   Moreover, a low dielectric constant of the hollow cavity reduces stray capacitance around conductive portion  12 , thus allowing a peak impedance to shift to a higher frequency band. 
   In addition, the liquefied glass infiltrates into magnetic section  15  and insulation substrate  10  around conductive portion  12  of coil pattern  13  to form the glass layers. The layers reduces the magnetic permeability of magnetic section  15  and allows magnetic section  15  to have non-magnetic properties. That is, non-magnetic section  23  is formed around the hollow cavity. This arrangement lowers the magnetic permeability around conductive portion  12 , and thus, prevents the magnetic flux generated in coil pattern  13  from passing through around conductive portion  12 . Therefore, magnetic flux generated efficiently for traveling around coil pattern  13  induces strong magnetic coupling in conductive portion  12 , thus increases attenuation properties, and allows magnetic section  15  around the hollow cavity to have non-magnetic properties. Therefore, a dielectric constant of the hollow cavity and proximity of the hollow cavity reduces stray capacitance induced around conductive portion  12 , and thus, allows a peak impedance to shift to a higher frequency band. 
   The glass layers formed around the hollow cavity especially prevent moisture from infiltrating into the hollow cavity even if magnetic section  15  has moisture absorption. This arrangement prevents conductive portion  12  from corrosion or migration due to, for example, moisture in the hollow cavity. 
   (Third Exemplary Embodiment) 
   A method of manufacturing an inductor device according to a third exemplary embodiment is a modification of that of the first embodiment. 
   As shown in  FIG. 8 , the method of manufacturing the inductor device according to the third embodiment includes insulation-substrate-forming process  11  to form insulation substrate  10 , coil-forming process  14  to form coil pattern  13  having spiral conductive portion  12  on insulation substrate  10 , magnetic-section-forming process  16  to stack magnetic section  15  on insulation substrate  10 , external-electrode-forming process  18  to form external electrode  17 , coupling process  19  to couple coil pattern  13  to external electrode  17  electrically, and simultaneously-sintering process  20  to sinter insulation substrate  10 , coil patterns  13 , and magnetic section  15  together. Simultaneously-sintering process  20  allows insulation substrate  10  and magnetic section  15  not to be sintered in advance. 
   In intaglio-printing process  22  in coil-forming process  14 , a printing substrate having a spiral recess filled with conductive paste is placed on insulation substrate  10 , the conductive paste is then transferred onto insulation substrate  10 , and coil pattern  13  is then formed on a single surface of insulation substrate  10 . 
   In non-magnetic-section-forming process  24  after coil-forming process  14 , non-magnetic section  23  is formed of non-magnetic material, such as glass around conductive portion  12  of coil pattern  13  to surround coil pattern  13 . 
   In coupling process  19 , a via-hole is provided in magnetic section  15  and is filled with conductive paste to form via-portion  29 . Coil pattern  13  and external electrode  17  are electrically coupled through lead-out electrode  30  and via-portion  29  made of conductive material. 
   Plural magnetic layers  31  each having a through-hole are laminated to form magnetic section  15 . Plural via-layers  32  each having the through-hole filled with conductive paste are laminated to form via-portion  29 . Each of edges  34  of via-layers  32  protrudes between through-hole peripheries  33  of magnetic layers  31  adjacent to each other. Through-hole peripheries  33  of magnetic layers  31  and edges  34  of via-layers  32  are laminated alternately. 
   According to the above configuration, similarly to the first embodiment, coil pattern  13  is formed on a single surface, and magnetic section  15  is not placed between conductive portions  12 . Therefore, the inductor device exhibits excellent attenuation properties in a higher frequency band, while having a low profile. 
   (Fourth Exemplary Embodiment) 
   A method of manufacturing a inductor device according to a fourth exemplary embodiment is a modification of that of the third embodiment. 
   In non-magnetic-section-forming process  24  of the third embodiment, an inductor device is filled with glass as non-magnetic material around conductive portion  12  of coil pattern  13 . In simultaneously-sintering process  20 , a liquefied glass infiltrates into magnetic section  15  and insulation substrate  10  to form a glass layer surrounding coil pattern  13 . Simultaneously, a hollow cavity is formed around conductive portion  12 . 
   According to the above configuration, the liquefied glass infiltrates into magnetic section  15  and insulation substrate  10 , and thus, allows the hollow cavity formed in a residual place of the glass to function as a non-magnetic section  23 . 
   The above arrangement lowers a magnetic permeability around conductive portion  12 , and thus prevents magnetic flux generated in coil pattern  13  from passing through around conductive portion  12 . Therefore, magnetic flux generated for traveling around coil pattern  13  induces strong magnetic coupling in conductive portion  12 , and increases attenuation properties. In addition, a low dielectric constant of the hollow cavity reduces stray capacitance induced in conductive portion  12 , and thus, allows a peak impedance to shift to a higher frequency band. 
   In addition, the liquefied glass infiltrates into magnetic section  15  around conductive portion  12  of coil pattern  13  to form a glass layer. The layer lowers a magnetic permeability of magnetic section  15  and allows magnetic section  15  to have non-magnetic properties. That is, non-magnetic section  23  is formed also around the hollow cavity. In this case, the lowered magnetic permeability around conductive portion  12  prevents magnetic flux generated in coil pattern  13  from passing through around conductive portion  12 . Therefore, magnetic flux generated for traveling around coil pattern  13  induces strong magnetic coupling in conductive portion  12 , and thus increases attenuation properties. 
   Moreover, magnetic section  15  having the non-magnetic properties around the hollow cavity reduces a dielectric constant in and near the hollow cavity more, thus reduces stray capacitance induced around conductive portion  12 , and thus allows a peak impedance to shift to a higher frequency band. 
   In particular, the glass layer formed around the hollow cavity prevents moisture from infiltrating into the hollow cavity through magnetic section  15  even if magnetic section  15  has a moisture absorption. Therefore, conductive portion  12  can be prevented from corrosion or migration due to, for example, moisture in the hollow cavity. 
   Ceramics or insulation resin can be employed instead of the glass as the non-magnetic material for the inductor device according to the fourth embodiment. The ceramics does not produce the hollow cavity in non-magnetic-section-forming process  24 . The insulation resin can provide the hollow cavity since the resin is burnt off at a temperature lower than a temperature at the sintering of magnetic section  15 . 
   INDUSTRIAL APPLICABILITY 
   In an inductor device according to the present invention, a coil pattern is formed on a single surface. Conductive portions are not formed on magnetic layers adjacent to each other, and thus, no magnetic material sandwiched between the conductive portions. This arrangement allows the inductor device to exhibit excellent attenuation properties and to have a low profile because of a thin magnetic section.