Patent Application
20130222101
The present invention relates to a coil component and its manufacturing method and, more particularly, to a coil component suitably usable as a power supply inductor and a coil component having a plane spiral conductor formed on a printed circuit board by electrolytic plating and its manufacturing method.
A surface-mounting type coil component is now widely used in consumer or industrial electronic equipment. Particularly, in small mobile equipment, there has occurred, along with its enhancement of functionality, a need to obtain a plurality of voltages from a single power supply in order to drive various devices provided therein. Such a coil component for power supply use is demanded to be small/thin, excellent in insulating performance and electrical reliability, and to be manufactured at low cost.
As a structure of a coil component that meets the above requirement, a planar coil structure based on a printed circuit board technology is known. The coil component of such a type has a structure in which planar coil patterns are formed respectively on both top and back surfaces of a printed circuit board and the printed circuit board is sandwiched between, e.g., EE type or EI type of sintered ferrite cores. With this configuration, a closed magnetic path is formed around the planar coil patterns.
The coil component for power supply use is required not to exhibit a decrease in inductance thereof due to magnetic saturation even when a certain high direct bias current is applied thereto. To meet the above requirement, a coil component described in Patent Document 1 has first and second magnetic layers covering upper and lower surfaces of an insulating substrate on each of which a planar spiral conductor is formed, and these two resin layers each have a gap in a thickness direction at an outer edge area of the coil pattern. This can suppress magnetic saturation in a magnetic circuit to increase an inductance of the magnetic circuit.
Patent Document 2 discloses a coil component having a structure in which an air-core coil is embedded in a packaging resin to be integrated therewith. This coil component includes a resin containing metal magnetic powder. In particular, by using a compound material in which two or more types of amorphous metal magnetic powder having different average particle diameters and an insulating binder are mixed with each other, it is possible to obtain high density, high magnetic permeability, and low core loss even under low pressure molding conditions.
In a field of commercial or industrial electronic equipment, the surface-mounting type coil component has come to be used frequently as a power supply inductor. This is because the surface-mounting type coil component is small/thin, excellent in insulating performance, and capable of being manufactured at low cost.
A planar coil structure using a printed circuit board technology is known as one of a specific structure of the surface-mounting type coil component. The following briefly describes the planar coil structure in terms of a manufacturing process thereof. First, a seed layer (base film) having a planar spiral conductor shape is formed on a printed circuit board. Then, the resultant circuit board is immersed in plating solution, and DC current (hereinafter, referred to as “plating current”) is applied to the seed layer to cause metal ions in the plating solution to be electrodeposited onto the seed layer. As a result, a planar spiral conductor is formed and, thereafter, an insulating resin layer covering the formed planar spiral conductor and a metal-magnetic-powder-containing resin layer serving as both of a protective layer and a magnetic path are sequentially formed, whereby manufacturing of the coil component is completed. This structure allows high dimensional and positional accuracy to be maintained, as well as, a reduction in size and thickness. Patent Document 1 discloses a planar coil element having such a planar coil structure.
In the conventional coil component disclosed in Patent Document 1, it is necessary to form a gap in order to increase an inductance. However, adjustment of a width of the gap is very difficult in terms of assembly accuracy or processing accuracy.
The conventional coil component described in Patent Document 2 uses a resin containing metal magnetic powder as a core material; however, since the conventional coil component uses an air-core coil formed by winding a wire, a size of the entire coil component is very large. In addition, it is difficult to maintain a shape of the coil, which poses a problem that an inner diameter of the coil and a position of the air-core coil are varied significantly.
An object of the present invention is therefore to provide a high-performance coil component which is excellent in DC superimposition characteristics and which does not require formation of a magnetic gap. Another object of the present invention is to provide a coil component which is high in dimension processing accuracy and which is small and thin.
A coil component used as a power supply inductor is required to have a possibly low DC resistance. Thus, a plan is being studied in which a plurality of substrates (hereinafter, referred to as “basic coil component”) on both surfaces of each of which a planar spiral conductor is formed are laminated and connected in parallel.
If the plurality of the basic coil components are simply laminated, opposing two planer spiral conductors are brought into contact with each other. If the two planar spiral conductors make contact with each other between the same turns with respect to all turns, the contact is equivalent to an increase in a film thickness of the planer spiral conductor. Therefore, no problem occurs in terms of characteristics. However, since it is not possible to completely control positions of the two basic coil components practically, it is inevitable that some displacement occurs. Therefore, there is a possibility that a contact between the turns which are not the same turns occurs.
Still another object of the present invention is therefore to provide a coil component capable of preventing, in a case where a plurality of basic coil components are laminated, two opposing planar spiral conductors from contacting each other except for contacts between the same turns, and its manufacturing method.
A coil component according to the present invention includes: a first substrate; a second substrate disposed such that a top surface thereof faces a back surface of the first substrate; first and second planar spiral conductors formed, by electrolytic plating, on the top and back surfaces of the first substrate, respectively, inner peripheral ends thereof being connected to each other through a first spiral conductor penetrating the first substrate; third and fourth planar spiral conductors formed, by electrolytic plating, on the top and back surfaces of the second substrate, respectively, inner peripheral ends thereof being connected to each other through a second spiral conductor penetrating the second substrate; an insulating layer formed between the second planer spiral conductor and third planar spiral conductor; a first external electrode connected to an outer peripheral end of the first planar spiral conductor and an outer peripheral end of the fourth planar spiral conductor; a second external electrode connected to an outer peripheral end of the second planar spiral conductor and an outer peripheral end of the third planar spiral conductor; a first insulating resin layer covering the first planar spiral conductor; an upper core covering the top surface of the first substrate on which the first insulating resin layer is formed; a second insulating resin layer covering the second planar spiral conductor; and an upper core covering the top surface of the second substrate on which the second insulating resin layer is formed. At least one of the upper and lower cores is formed of a metal-magnetic-powder-containing resin. The coil component further includes connecting portions disposed respectively at center and outside portions of each of the first and second substrates so as to physically connect the upper and lower cores.
According to the present invention, it is possible to provide a high-performance coil component capable of exhibiting excellent DC superimposition characteristics and capable of eliminating the need to form a magnetic gap. Further, there can be provided a coil component capable of achieving a high dimension processing accuracy and capable of reducing the size and thickness. Further, formation of the insulating film can prevent the facing second and third planar spiral conductors from being brought into contact with each other.
In the above coil component, film thicknesses of innermost and outermost turns of each of the second and third planar spiral conductors may be larger than those of the other turns thereof. A top surface of the innermost turns of the second planer spiral conductor and a top surface of the innermost turn of the third planar spiral conductor may penetrate the insulating layer to be brought into contact with each other. Atop surface of the outermost turn of the second planer spiral conductor and a top surface of the outermost turn of the third planar spiral conductor may penetrate the insulating layer to be brought into contact with each other. Top surfaces of turns of the second planar spiral conductor other than the innermost and outermost turns and top surfaces of turns of the third planar spiral conductor other than the innermost and outermost turns may be electrically isolated from each other by the insulating layer.
A coil component according to an aspect of the present invention includes: at least one insulating substrate; a spiral conductor formed on at least one main surface of the insulating substrate, an upper core covering the one main surface of the insulating substrate; and a lower core covering the other main surface of the insulating substrate. At least one of the upper and lower cores is formed of a metal-magnetic-powder-containing resin. The coil component further includes connecting portions disposed respectively at center and outside portions of the insulating substrate so as to physically connect the upper and lower cores.
According to the present invention, the metal-magnetic-powder-containing resin is used as a material of a closed magnetic path, so that a resin exists between the metal magnetic powder particles to form minute gaps. This increases a saturation flux density, eliminating the need to form a gap, unlike a case where a ferrite core is used. Therefore, it is not necessary to perform machine processing for the magnetic core with high accuracy, and a small and thin coil component can be provided.
In the present invention, both the upper and lower cores are preferably formed of the metal-magnetic-powder-containing resin. With this configuration, the entire magnetic core is formed of the metal-magnetic-powder-containing resin, so that a coil component having sufficiently high DC superimposition characteristics can be provided.
In the present invention, it is preferable that one of the upper and lower cores is formed of the metal-magnetic-powder-containing resin and the other one thereof is formed of a ferrite substrate. With this configuration, a metal-magnetic-powder-containing resin paste can be applied by using the ferrite substrate as a support substrate, thereby facilitating formation of the magnetic core using the metal-magnetic-powder-containing resin. Further, a saturation flux density can be sufficiently increased by the magnetic core formed of the metal-magnetic-powder-containing resin, so that even if one of the cores is formed of the ferrite substrate, there can be provided a coil component capable of exhibiting high DC superimposition characteristics without forming a gap.
In the present invention, the connecting portions each connecting the upper and lower cores are preferably disposed at respective four corner portions of the insulating substrate. Formation of the closed magnetic paths at the four corners results in an increase in an area for forming the spiral conductor, thereby increasing a loop size. This can achieve a low coil resistance, a high inductance, and a reduction in size. Further, the connecting portions can be formed by using a comparatively wide margin area in which the spiral conductor is not formed, thereby increasing a sectional area of the closed magnetic path.
In the case where the connecting portions each connecting the upper and lower cores are disposed at the respective four corners of the insulating substrate, the connecting portions at the respective four corners may be disposed in contact with an edge of each of the corner portions of the insulating substrate or may be disposed inward of the edge thereof. In the case where the connecting portions at the respective four corners are disposed in contact with the edge of each of the corner portions of the insulating substrate, the connecting portions can be processed easily at the mass production. That is, the connecting portions of the individual chips can be formed by forming a connecting portion common to adjacent four chips and dividing it into four parts. On the other hand, in the case where the connecting portions are disposed inward of the edge of each of the corner portions of the insulating substrate, a plating conductor pattern to be described later can be easily disposed.
The coil component according to the present invention further preferably includes a plating conductor pattern formed on the one main surface of the insulating substrate. One end of the plating conductor pattern is preferably electrically connected to the spiral conductor and the other end thereof extends up to the edge of the insulating substrate. Further, at the mass production time when a plurality of coil components are formed on a single substrate, the plating conductor pattern preferably constitutes a part of a short-circuiting pattern electrically connecting the spiral conductors of adjacent coil components. With this configuration, the conductor pattern of a plurality of adjacent chips can be subjected to plating at a time, thereby increasing efficiency of the manufacturing process.
The coil component according to the present invention further preferably includes a pair of terminal electrodes formed on outer peripheral surfaces of a laminated body constituted by the insulating substrate and the upper and lower cores, and an insulating film covering surfaces of the upper and lower cores. Preferably, the insulating film is interposed between the pair of terminal electrodes and the upper and lower cores. In this case, the insulating film is preferably an insulating layer obtained by chemical conversion treatment using iron phosphate, zinc phosphate, or zirconia dispersed solution. With this configuration, insulation between the pair of terminal electrodes can be ensured.
In the present invention, the insulating film is also preferably formed of an Ni-based-ferrite-containing resin. With this configuration, the insulating film can be made to function as a part of the closed magnetic path.
The coil component according to the present invention preferably includes a plurality of the insulating substrates. The plurality of insulating substrates are preferably laminated substantially without intervention of the metal-magnetic-powder-containing resin, and the spiral conductors formed on the respective insulating substrates are connected in parallel or in series through the pair of terminal electrodes. There is a limit to a sectional area of the spiral conductor that can be formed on the insulating substrate; however, by laminating a plurality of insulating substrates and connecting the spiral conductors formed on the respective insulating substrates in parallel, a configuration equivalent to that in which the sectional area of the spiral conductor is increased can be obtained. Further, by connecting the spiral conductors formed on the respective insulating substrates in series, the number of turns of the coil required in each substrate is reduced, so that it is possible to increase a wire width and a wire thickness of the spiral conductor, thereby sufficiently increasing the sectional area of the spiral conductor. As a result, a DC resistance of the coil component can be reduced.
A coil component according to another aspect of the present invention includes: a first substrate; a second substrate disposed such that a top surface thereof faces to a back surface of the first substrate; first and second planar spiral conductors formed, by electrolytic plating, on the top and back surfaces of the first substrate, respectively, inner peripheral ends thereof being connected to each other through a first spiral conductor penetrating the first substrate; third and fourth planar spiral conductors formed, by electrolytic plating, on the top and back surfaces of the second substrate, respectively, inner peripheral ends thereof being connected to each other through a second spiral conductor penetrating the second substrate; an insulating layer formed between the second planer spiral conductor and third planar spiral conductor; a first external electrode connected to an outer peripheral end of the first planar spiral conductor and an outer peripheral end of the fourth planar spiral conductor; and a second external electrode connected to an outer peripheral end of the second planar spiral conductor and an outer peripheral end of the third planar spiral conductor.
According to the present invention, formation of the insulating layer can prevent the facing second and third planer spiral conductors from being brought into contact with each other.
In the above coil component, film thicknesses of innermost and outermost turns of each of the second and third planar spiral conductors may be larger than those of the other turns thereof. A top surface of the innermost turn of the second planer spiral conductor and a top surface of the innermost turn of the third planar spiral conductor may penetrate the insulating layer to be brought into contact with each other. Atop surface of the outermost turn of the second planer spiral conductor and a top surface of the outermost turn of the third planar spiral conductor may penetrate the insulating layer to be brought into contact with each other. Top surfaces of turns of the second planar spiral conductor other than the innermost and outermost turns and top surfaces of turns of the third planar spiral conductor other than the innermost and outermost turns may be electrically isolated from each other by the insulating layer. With the above configuration, even if the displacement occurs between the second and third planar spiral conductors, it is avoided that the contact between a given turn of one of the second and third planer spiral conductors and a different turn of the other one thereof occurs. Further, it is possible to bring the two planar spiral conductors close to each other to such a degree that the innermost and outermost turns thereof contact each other, thereby achieving a high inductance and a reduction in height. That the film thicknesses of the innermost and outermost turns of the respective second and third planar spiral conductors are larger than those of the other turns thereof is a feature of the electrolytic plating.
In the above coil component, the film thicknesses of the turns of the second planar spiral conductors may be made uniform, and the film thicknesses of the turns of the third planar spiral conductors may be made uniform. The uniformity in the film thicknesses of the turns of each of the second and third planar spiral conductors each of which is formed by the electrolytic plating indicates that the film thicknesses of the respective innermost and outermost turns are reduced after the electrolytic plating. Thus, according to the above coil component, a distance (distance between top surfaces) between the second and third planar spiral conductors each formed by the electrolytic plating can be minimized, thereby achieving a high inductance and a reduction in height.
Further, in the above coil component, the film thicknesses of the turns of the first planar spiral conductor may be made uniform, and the film thicknesses of the turns of the fourth planar spiral conductor may be made also uniform. This further reduces the height.
The above each coil component may further include an insulating resin layer covering the first and fourth planar spiral conductors and a metal-magnetic-powder-containing resin layer covering the surfaces of the first and fourth surfaces on which the insulating resin layer is formed. With this configuration, it is possible to obtain a power supply choke coil excellent in DC superimposition characteristics.
A manufacturing method of a coil component according to the present invention includes: a conductor formation step of forming first and second planar spiral conductors on respective top and back surfaces of a first substrate by electrolytic plating, forming a first through hole conductor penetrating the first substrate so as to connect an inner peripheral end of the first planar spiral conductor and an inner peripheral end of the second planar spiral conductor, forming third and fourth planar spiral conductors on respective top and back surfaces of the second substrate by the electrolytic plating, and forming a second through hole conductor penetrating the second substrate so as to connect an inner peripheral end of the third planar spiral conductor and an inner peripheral end of the fourth planar spiral conductor; an insulating resin layer formation step of forming a first insulating resin layer covering top surfaces of turns of the second planar spiral conductor other than at least the outermost and innermost turns and forming a second insulating resin layer covering top surfaces of turns of the third planar spiral conductor other than at least the outermost and innermost turns; a lamination step of laminating the first and second substrates such that the back surface of the first substrate and the top surface of the second substrate face each other; and an external electrode formation step of forming a first external electrode connecting an outer peripheral end of the first planar spiral conductor and an outer peripheral end of the fourth planar spiral conductor and a second external electrode connecting an outer peripheral end of the second planar spiral conductor and an outer peripheral end of the third planar spiral conductor.
According to the present invention, formation of the first and second insulating resin layers can prevent the facing second and third planar spiral conductors from being brought into physical contact with each other, excluding at least contacts between outermost turns and between innermost turns.
In the above coil component manufacturing method, the first insulating resin layer may cover also the top surfaces of the outermost and innermost turns of the second planar spiral conductor, and the second insulating resin layer may cover also the top surfaces of the outermost and innermost turns of the third planar spiral conductor. The insulating resin layer formation step may include a grinding step of applying grinding to the surface of the first insulating resin layer to expose the top surfaces of the outermost and innermost turns of the second planar spiral conductor from the surface of the first insulating resin layer and applying grinding to the surface of the second insulating resin layer to expose the top surfaces of the outermost and innermost turns of the third planar spiral conductor from the surface of the second insulating resin layer. The lamination step may laminate the first and second substrates in a state where the top surfaces of the outermost and innermost turns of the second planar spiral conductor are exposed from the surface of the first insulating resin layer and where the top surfaces of the outermost and innermost turns of the third planar spiral conductor are exposed from the surface of the second insulating resin layer. With the above configuration, even if a displacement occurs between the second and third planar spiral conductors, the contact between a given turn of one of the second and third planer spiral conductors and a different turn of the other one thereof does not occur. Further, it is possible to bring the two planar spiral conductors close to each other to such a degree that the innermost and outermost turns thereof contact each other, thereby achieving a high inductance and a reduction in height.
In the above coil component manufacturing method, the insulating resin layer formation step may include a grinding step of applying grinding to the surface of the first insulating resin layer to expose the top surfaces of respective turns of the second planar spiral conductor from the surface of the first insulating resin layer and applying grinding to the surface of the second insulating resin layer to expose the top surfaces of respective turns of the third planar spiral conductor from the surface of the second insulating resin layer, and a step of forming a third insulating resin layer covering at least one of the surfaces of the first and second insulating resin layers. The top surfaces of the respective turns of the second planar spiral conductor and top surfaces of the respective turns of the third planar spiral conductor may be electrically isolated from each other by the third insulating resin layer. As a result, it is possible to minimize a distance (distance between top surfaces) between the second and third planar spiral conductors each formed by electrolytic plating, thereby achieving a high inductance and a reduction in height.
The above coil component manufacturing method may further include, after the lamination step, a step of forming a fourth insulating resin layer covering the first and fourth planar spiral conductors and further forming a metal-magnetic-powder-containing resin layer covering the first and fourth surfaces on which the fourth insulating resin layer is formed, and a step of forming an insulating layer on a surface of the metal-magnetic-powder-containing resin layer. The external electrode formation step may form the first and second external electrodes after the formation of the insulating layer. With this configuration, it is possible to obtain a power supply choke coil excellent in DC superimposition characteristics.
Further, in the above coil component manufacturing method, the insulating resin layer formation step may further include a step of forming the first insulating resin layer so as to cover also the first planar spiral conductor, forming the second insulating resin layer so as to cover the fourth planar spiral conductor and forming a metal-magnetic-powder-containing resin layer covering the first and fourth surfaces on which the first and second insulating resin layers are formed, and a step of forming an insulating layer on a surface of the metal-magnetic-powder-containing resin layer. The external electrode formation step may form, after the formation of the insulating layer, the first and second external electrodes. With this configuration, it is possible to obtain a power supply choke coil excellent in DC superimposition characteristics.
According to the present invention, it is possible to provide a high-performance coil component capable of exhibiting excellent DC superimposition characteristics and capable of eliminating the need to form a magnetic gap. Further, there can be provided a coil component capable of achieving a high dimension processing accuracy and capable of reducing the size and thickness. Further, formation of the insulating layer can prevent the facing second and third planar spiral conductors from being brought into contact with each other.
Preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings.
As illustrated in
The insulating substrate 11 serves as a base layer for forming the first and second spiral conductors 12 and 13. The insulating substrate 11 is formed into a rectangular shape and has, at a center portion thereof, a circular opening 11h. The insulating substrate 11 is preferably formed of a common printed board material obtained by impregnating a glass fiber cloth with an epoxy resin. For example, a BT base material, an FR4 base material, an FR5 base material, or the like may be used. In a case where the printed board material is used, the spiral conductor can be formed by plating, not by sputtering in so-called a thin film method, so that a thickness of the conductor can be made sufficiently large. In order to avoid an increase in floating capacitance, a dielectric constant of the insulating substrate 11 is preferably equal to or less than 7 (μ≦7). Although not especially limited, a dimension of the insulating substrate 11 can be set to, e.g., 2.5 mm×2.0 mm×0.3 mm.
The first and second spiral conductors 12 and 13 are each a circular spiral and are each disposed so as to surround the opening 11h of the insulating substrate 11. Although the first and second spiral conductors 12 and 13 are roughly overlapped with each other as viewed from the above, they do not completely coincide with each other. That is, the first spiral conductor 12 forms a counterclockwise spiral extending from an outer peripheral end 12b to an inner peripheral end 12a as viewed from the upper surface 11a side of the insulating substrate 11, and the second spiral conductor 13 forms a counterclockwise spiral extending from an inner peripheral end 13a to an outer peripheral end 13b as viewed from also the upper surface 11a side of the insulating substrate 11. With this configuration, directions of magnetic fluxes generated upon flowing of current through the spiral conductors 12 and 13 are made coincide with each other. As a result, the magnetic fluxes generated in the spiral conductors 12 and 13 are superimposed to reinforce one another, thereby allowing a high inductance to be obtained.
The pair of terminal electrodes 17a and 17b are mounted to two opposing side surfaces 18a and 18b, respectively, of a laminated body constituted by the insulating substrate 11, upper core 15, and lower core 16. The outer peripheral end 12b of the first spiral conductor 12 is drawn up to the first side surface 18a and connected to the terminal electrode 17a. The outer peripheral end 13b of the second spiral conductor 13 is drawn up to the second side surface 18b and connected to the terminal electrode 17b. The inner peripheral end 12a of the first spiral conductor 12 and inner peripheral end 13a of the second spiral conductor 13 are connected to each other through a through hole conductor 11i penetrating the insulating substrate 11. Thus, the first and second spiral conductors 12 and 13 are connected in series to constitute a single coil.
As a material for the first and second spiral conductors 12 and 13, Cu having a high conductivity and being easily processed is preferably used. Although not especially limited, a width, height, and a pitch of each of the first and second spiral conductors 12 and 13 can be set to 70 μm, 120 μm, and 10 μm, respectively. Such first and second spiral conductors 12 and 13 are each preferably formed by plating. In a case where the first and second spiral conductors 12 and 13 are formed by plating, an aspect ratio thereof can be increased and, thus, a coil having a comparatively large cross section and having a low DC resistance can be formed.
The upper and lower cores 15 and 16 are each formed of a metal-magnetic-powder-containing resin. In the present embodiment, the upper and lower cores 15 and 16 are formed of the same material and formed integrally, so that a boundary between them is not clear in appearance; actually, however, the upper core 15 is formed as an E-type core including a flat-plate portion and a columnar portion (connecting portion) protruding downward from the flat-plate portion, and the lower core 16 is formed as an I-type core constituted by a plate-like portion.
The upper core 15 are connected to the lower core 16 through a connecting portion 15a provided in a center portion of a rectangular flat area and two connecting portions 15b formed along two opposing side surfaces 18c and 18d, whereby a completely-closed magnetic path is formed. That is, the connecting portions 15a and 15b penetrate the insulating substrate 11 and insulating resin layers 14a and 14b and, thus, no gap exists in the closed magnetic path. In a case where sintered ferrite cores are used, a gap needs to be formed so as not to cause magnetic saturation even if a certain level or more of current is made to flow; on the other hand, in a case where the metal-magnetic-powder-containing resin is used, the resin exists between the metal magnetic particles to form minute gaps. This increases a saturation flux density, so that it is possible to prevent the magnetic saturation without forming an air gap between the upper and lower cores 15 and 16. Therefore, it is not necessary to perform machine processing for the magnetic core with high accuracy in order to form a gap.
The metal-magnetic-powder-containing resin is a magnetic material obtained by mixing metal magnetic powder in the resin. As the metal magnetic powder, a permalloy-based material is preferably used. Specifically, it is preferably to use metal magnetic powder obtained by mixing a Pb—Ni—Co alloy having an average particle diameter of 20 μm to 50 μm, which is used as first metal magnetic powder and carbonyl iron having an average particle diameter of 3 μm to 10 μm, which is used as second metal magnetic powder, at a predetermined weight ratio (e.g., 70:30 to 80:20, preferably, 75:25). A content percentage of the metal magnetic powder is preferably 90% by weight to 96% by weight. Alternatively, the content percentage of the metal magnetic powder may be 96% by weight to 98% by weight. When an amount of the metal magnetic powder relative to the resin is reduced, the saturation flux density is reduced and, conversely, when the amount of the metal magnetic powder relative to the resin is increased, the saturation flux density is increased. That is, by controlling only the amount of the metal magnetic powder, the saturation flux density can be controlled.
It is particularly preferable to use metal magnetic powder obtained by mixing the first metal magnetic powder having an average particle diameter of 5 μm and the second metal magnetic powder having an average particle diameter of 50 μm at a predetermined ratio, e.g., 75:25. When the two kinds of metal magnetic powder having different particle diameters are used as described above, a high-density magnetic core can be formed under low pressure or non-pressure conditions, thereby achieving a magnetic core having high permeability and low core loss.
The resin contained in the metal-magnetic-powder-containing resin functions as an insulating binder. As a material for the resin, a liquid epoxy resin or a powder epoxy resin is preferably used. A content percentage of the resin is preferably 4% by weight to 10% by weight.
The upper and lower cores 15 and 16 preferably have the same thickness, and a sum of the thicknesses thereof is preferably 0.3 mm to 1.2 mm. When the sum of the thicknesses of the upper and lower cores 15 and 16 is smaller than 0.3 mm, not only mechanical strength of the component, but also the inductance of the coil is reduced, and when the sum of the thicknesses is larger than 1.2 mm, the inductance is saturated and not increased any more despite an increase in the thickness of the component.
In the present embodiment, an insulating film 19 is preferably formed on surfaces of the upper and lower cores 15 and 16. The insulating film 19 can be formed by chemical conversion treatment, andiron phosphate, zinc phosphate, or zirconia is preferably used in the chemical conversion treatment. When the metal-magnetic-powder-containing resin is used as the material constituting the closed magnetic path as described above, an insulating property between the terminal electrodes 17a and 17b becomes an issue because the metal magnetic powder is a conductor. However, according to the present embodiment, a surface of the metal-magnetic-powder-containing resin is insulating-coated, so that it is possible to ensure a sufficient insulating property between the terminal electrodes 17a and 17b.
In the manufacturing process of the coil component 10, as illustrated in
Subsequently, electrolytic plating is performed using the resist pattern as a mask to form a thick Cu film on the Cu base film. Thereafter, the resist is removed, and the base film is removed by etching to leave only the spiral conductors. With the above procedure, an insulating substrate (hereinafter, TFC (Thin Film Coil) substrate 21) on which the spiral conductors are formed is obtained.
Subsequently, as illustrated in
Subsequently, as illustrated in
Subsequently, as illustrated in
As described above, the coil component 10 according to the present embodiment, in which the magnetic body covering the first and second spiral conductors 12 and 13 is resin-molded, has a very high dimension processing accuracy. Further, since a plurality of the coil components are formed as an assembly on the substrate surface, coil position accuracy is significantly high, and a reduction in size and thickness is allowed. The magnetic body, which is formed of the metal magnetic material, has more excellent DC superimposition characteristics than the ferrite, thus eliminating the need to form a magnetic gap.
As illustrated in
In the manufacturing process of the coil component 20, the TFC substrate 21 illustrated in
As described above, in the coil component 20 according to the present embodiment, the metal-magnetic-powder-containing resin is used to form the upper core 15, so that the same effects as those of the coil component 10 according to the first embodiment can be achieved. Further, the ferrite substrate can be used as a support substrate at a time of formation of the resin paste, thus eliminating the need to use the UV tape 22, facilitating the manufacturing process of the coil component 20.
As illustrated in
In the present embodiment, the material of the lower core 16 is not especially limited as long as the connecting portions 15d are each formed of the metal-magnetic-powder-containing resin. Thus, the material of the lower core 16 may be the metal-magnetic-powder-containing resin or ferrite substrate. In either case, the upper and lower cores 15 and 16 are completely connected to each other at the four corners of the insulating substrate 11, so that a closed magnetic path having no gap can be formed as in the case of the first embodiment. Further, in the present embodiment, formation of the closed magnetic paths at the four corners results in an increase in an area for forming the spiral conductors 12 and 13, thereby increasing a loop size. This can achieve a low coil resistance, a high inductance, and a reduction in size.
In the manufacturing process of the coil component 30, the TFC substrate 21 is first produced. A production method of the TFC substrate 21 is the same as that for the coil component 10 according to the first embodiment except that, as illustrated in
As illustrated in
Further, a plating conductor pattern 24 for short-circuiting conductor patterns of adjacent chips in the mass production process is provided in the coil component 40. The conductor pattern 24 is provided for allowing voltage to be simultaneously applied to all the conductor patterns during electroplating in the mass production. For example, in the coil component 30 according to the third embodiment illustrated
In a state of a finished article (in an individual chip obtained by cutting the insulating substrate), one end of the plating conductor pattern 24 is electrically connected to the spiral conductor 12 (or spiral conductor 13), and the other end thereof extends up to the edge of the insulating substrate 11 to be an open end. The conductor pattern 24 need not always be formed at the edge of the insulating substrate 11, but may be formed at an arbitrary position. In that case, the conductor pattern 24 can be formed in, for example, the coil component 30 according to the third embodiment.
As illustrated in
When the metal-magnetic-powder-containing resin is used as a magnetic core for constituting the closed magnetic path as described above, an insulating property between the terminal electrodes 17a and 17b becomes an issue because the metal magnetic powder is a conductor. However, according to the present embodiment, the surface of the metal-magnetic-powder-containing resin is insulating-coated, so that it is possible to ensure a sufficient insulating property between the terminal electrodes 17a and 17b. Further, in the coil component 10 according to the first embodiment, the surfaces of the upper and lower cores 15 and 16 are insulating-coated by the chemical conversion treatment; however, the insulating coating part does not function as the closed magnetic path. According the present invention, it is possible to allow the insulating film to function as part of the closed magnetic path while ensuring the insulating property, which can in turn improve inductance characteristics.
In the manufacturing process of the coil component 50, the metal-magnetic-powder-containing resin is formed on the both surfaces of the TFC substrate 21 (see
Then, as illustrated in
Subsequently, the TFC substrate 21 is diced along the cutting lines Cx and Cy to divide a coil assembly into pieces (see
As illustrated in
In the above structure, the metal-magnetic-powder-containing resin unintentionally exists between the insulating substrates 11A and 11B for manufacturing reasons. However, such a metal-magnetic-powder-containing resin does not adversely affect the insulating property. Thus, there is no problem unless the metal-magnetic-powder-containing resin exists in essence between the insulating substrates 11A and 11B.
The first and second spiral conductors 12 and 13 formed on the upper and lower surfaces of the insulating substrate 11A constitute a single coil, and the first and second spiral conductors 12 and 13 formed on the upper and lower surfaces of the insulating substrate 11B also constitute a single coil. The outer peripheral end 12b of the first spiral conductor 12 on the insulating substrate 11A and the outer peripheral end 12b of the first spiral conductor 12 on the insulating substrate 11B are electrically connected to each other through the first terminal electrode 17a, and the outer peripheral end 13b of the second spiral conductor 13 on the insulating substrate 11A and the outer peripheral end 13b of the second spiral conductor 13 on the insulating substrate 11B are electrically connected to each other through the second terminal electrode 17b, whereby the two coils are connected to each other in parallel. The parallel connection between the coils having the same structure corresponds to doubling of a sectional area of the coil conductor, so that it is possible to reduce the resistance of the coil to half, thereby allowing a reduction in the DC resistance.
As illustrated in
The series connection between the first and second coils 71A and 71B needs to be made through an external terminal electrode. Thus, a terminal electrode 17c for series connection is provided in addition to the pair of terminal electrodes 17a and 17b. As illustrated in
In the case where the two insulating substrates 11A and 11B are used and where the single coils 71A and 71B formed respectively on the insulating substrates 11A and 11B are connected in series, the number of turns of the coil required in one substrate is reduced, thereby allowing an increase in a wire width of the spiral conductor. The increase in the wire width in turn allows an increase in plating thickness, which can sufficiently increase a sectional area of the spiral conductor and can thus reduce the DC resistance.
Although the first to seventh embodiments of the present invention are described above, the invention is not limited to the embodiments. Various modifications can be made without departing from the scope of the present invention, and obviously the modifications are included in the scope of the present invention.
For example, although the inner peripheral end 12a of the first spiral conductor 12 and inner peripheral end 13a of the second spiral conductor 13 are connected to each other through the through hole conductor 11i in the above first to seventh embodiments, the present invention is not limited to this. For example, the inner peripheral ends may be connected to each other through a conductor pattern formed in an inner peripheral surface of the opening 11h of the printed board.
As illustrated in
As a material of each of the substrates 2a and 2b, a common printed board which is obtained by impregnating a glass fiber cloth with an epoxy resin is preferably used. Further, for example, a BT resin base material, an FR4 base material, an FR5 base material may be used.
A planar spiral conductor 30a (first planar spiral conductor) is formed at a center portion of a top surface 2at of the substrate 2a. Similarly, a planar spiral conductor 30b (second planar spiral conductor) is formed at a center portion of the back surface 2ab. A conductor-embedding through hole 32s (first through hole) is formed in the substrate 2a, and a through hole conductor 32a (first through hole conductor) is embedded inside the through hole 32s. An inner peripheral end of the planar spiral conductor 30a and an inner peripheral end of the planar spiral conductor 30b are connected to each other through the through hole conductor 32a.
A planar spiral conductor 30c (third planar spiral conductor) is formed at a center portion of the top surface 2bt of the substrate 2b. Similarly, a planar spiral conductor 30d (fourth planar spiral conductor) is formed at a center portion of a back surface 2bb. A conductor-embedding through hole 32t (second through hole) is formed also in the substrate 2b, and a through hole conductor 32b (second through hole conductor) is embedded inside the through hole 32t. An inner peripheral end of the planar spiral conductor 30c and an inner peripheral end of the planar spiral conductor 30d are connected to each other through the through hole conductor 32b.
The planar spiral conductor 30a and planar spiral conductor 30b are wound in opposite directions to each other. That is, the planar spiral conductor 30a is wound in a counterclockwise direction from its inner peripheral end to outer peripheral end as viewed from the top surface 2at side, and the planar spiral conductor 30b is wound in a clockwise direction from its inner peripheral end to outer peripheral end as viewed from also the top surface 2at side. With such a configuration, when current is made to flow between the outer peripheral end of the planar spiral conductor 30a and outer peripheral end of the planar spiral conductor 30b, both the planar spiral conductors generate magnetic fields of the same direction to reinforce one another. Thus, the basic coil component 1a functions as one inductor.
The same can be said for the planar spiral conductors 30c and 30d. However, the planar spiral conductor 30c has the same planar shape as that of the planar spiral conductor 30b as viewed from the top surface 2at side, and planar spiral conductor 30d has the same planar shape as that of the planar spiral conductor 30a as viewed from also the top surface 2at side. That is, the basic coil component 1a and basic coil component 1b have vertically inverted shapes.
Lead-out conductors 31a and 31b are formed on the top surface 2at and back surface 2ab of the substrate 2a, respectively. The lead-out conductor 31a (first lead-out conductor) is formed along a side surface 2ax of the substrate 2a. The lead-out conductor 31b (second lead-out conductor) is formed along a side surface 2ay opposite to the side surface 2ax. The lead-out conductor 31a is connected to the outer peripheral end of the planar spiral conductor 30a, and the lead-out conductor 31b is connected to the outer peripheral end of the planar spiral conductor 30b.
Similarly, Lead-out conductors 31c and 31d are formed on the top surface 2bt and back surface 2bb of the substrate 2b, respectively. The lead-out conductor 31c (third lead-out conductor) is formed along a side surface 2by of the substrate 2b. The side surface 2by is a side surface on the same side as the side surface 2ay of the substrate 2a. The lead-out conductor 31d (fourth lead-out conductor) is formed along a side surface 2bx opposite to the side surface 2by. The side surface 2bx is a side surface on the same side as the side surface 2ax of the substrate 2a. The lead-out conductor 31c is connected to the outer peripheral end of the planar spiral conductor 30c, and the lead-out conductor 31d is connected to the outer peripheral end of the planar spiral conductor 30d.
The planar spiral conductors 30a to 30d and lead-out conductors 31a to 31d are each obtained by forming a base layer through an electroless plating process and then by performing a electrolytic plating process two times. Both materials of the base layer and a plated layer formed in the two electrolytic plating processes are preferably Cu. The plated layer formed in the first electrolytic plating process serves as a seed layer in the second electrolytic plating process. This will be described in detail layer.
As illustrated in
The top surface 2at of the substrate 2a and the back surface 2bb of the substrate 2b which are covered by the insulating resin layer 41 are further covered by a metal-magnetic-powder-containing resin layer 42. The metal-magnetic-powder-containing resin layer 42 are formed of a magnetic material (metal-magnetic-powder-containing resin) obtained by mixing metal magnetic particles with a resin. As the metal magnetic powder, a permalloy-based material is preferably used. Specifically, it is preferable to use metal magnetic powder obtained by mixing a Pb—Ni—Co alloy having an average particle diameter of 20 μm to 50 μm and carbonyl iron having an average particle diameter of 3 μm to 10 μm at a predetermined weight ratio of 70:30 to 80:20, preferably, 75:25. A content percentage of the metal magnetic powder in the metal-magnetic-powder-containing resin layer 42 is preferably 90% by weight to 96% by weight. Alternatively, the content percentage of the metal magnetic powder in the metal-magnetic-powder-containing resin layer 42 may be 96% by weight to 98% by weight. As a material for the resin, a liquid epoxy resin or a powder epoxy resin is preferably used. A content percentage of the resin in the metal-magnetic-powder-containing resin layer 42 is preferably 4% by weight to 10% by weight. The resin functions as an insulating binder. In the metal-magnetic-powder-containing resin layer 42 having the above configuration, the smaller an amount of the metal magnetic powder relative to the resin is, the lower the saturation flux density and, conversely, the larger the amount of the metal magnetic powder relative to the resin is, the higher the saturation flux density.
As illustrated in
Further, as illustrated in
As illustrated in
Functions and effects of the coil component 1 will be described in detail below.
When the two basic coil components 1a and 1b are laminated one over the other for a reduction in the DC resistance, a distance between the two components is preferably as small as possible so as to strengthen the magnetic coupling between the planar spiral conductors for an increase in inductance and to reduce a height of the entire component.
Actually, however, a coil-turn displacement inevitably occurs when the two basic coil components 1a and 1b are laminated one over the other, which makes it difficult to achieve the laminated state as illustrated in
In order to cope with this, as illustrated in
Amass production process of the coil component 1 will be described. Although the following description is made first focusing on the basic coil component 1a, the same can be applied to the basic coil component 1b.
In the following description, the basic coil component 1a in which through holes 34a are formed at the four corner portions of the substrate 2a (substrate 2a after cutting) as illustrated in
First, as illustrated in
Then, as illustrated in
Similarly, on the back surface 2ab of the substrate 2a, the planar spiral conductor 30b whose inner peripheral end covers the through hole 32s is formed for each rectangular area. Further, the lead-out conductor 31b to be connected to the outer peripheral end of the planar spiral conductor 30b is formed along one of the four sides of the rectangular area that is opposed to the lead-out conductor 31a. The lead-out conductor 31b is also shared between two adjacently disposed rectangular areas and is formed so as to be connected to the outer peripheral ends of the planar spiral conductors 30b formed in the two rectangular areas.
Further, on both the top surface 2at and back surface 2ab of the substrate 2a, planar conductors 33 connecting adjacent two planar spiral conductors in an x-direction are formed. The planer conductors 33 are formed for causing plating current to flow in both x- and y-directions in the second electrolytic plating process to be described later.
A specific formation method of the planar spiral conductors 30a and 30b, etc. in a stage illustrated in
The conductors thus formed on the top surface 2at and back surface 2bb of the substrate 2a serve as the seed layers in the second electrolytic plating process. The seed layers are connected to each other through the lead-out conductors 31a and 31b, through hole conductors 32a, and planar conductors 33 in both the x- and y-directions, so that the plating current can be made to flow in both the x- and y-directions in the second electrolytic plating process.
Subsequently, as illustrated in
Subsequently, as illustrated in
Then, as illustrated in
The same processes are applied as for the basic coil component 1b. That is, the planar spiral conductors 30c and 30d, lead-out conductors 31c and 31d, and through hole conductors 32b are formed on the substrate 2b. Then, the both surfaces of the resultant substrate 2b is covered with the insulating resin layer 41 (second insulating resin layer), and grinding is applied to the both surfaces of the substrate 2b to the same degree as for the basic coil component 1a. Thereafter, the insulating resin is formed once again on the back surface 2bb side of the substrate 2b to cover once again the top surface of the exposed planar spiral conductor 30d, etc., with the insulating resin layer 41.
After the basic coil components 1a and 1b are formed in the manner as described above, the two basic coil components 1a and 1b are laminated such that the back surface 2ab of the substrate 2a and top surface 2bt of the substrate 2b face each other, as illustrated in
After the lamination, the top surface 2at of the substrate 2a and back surface 2bb of the substrate 2b are covered with the metal-magnetic-powder-containing resin layer 42. Specifically, a UV tape (not illustrated) for preventing warpage of the substrates 2a and 2b is attached to the back surface 2bb of the substrate 2b, and the metal-magnetic-powder-containing resin paste is screen-printed on the top surface 2at of the substrate 2a. In place of the UV tape, a thermal release tape may be used. A thickness of a screen sheet formed of the metal-magnetic-powder-containing resin paste is preferably about 0.27 mm. After the screen printing, defoaming is performed, and then heating is performed at a temperature of 80° C. for 30 minutes, to temporarily cure the resin paste. Subsequently, the UV tape is removed, and the metal-magnetic-powder-containing resin paste is screen-printed on the back surface 2bb of the substrate 2b. Similarly, a thickness of a screen sheet formed of the metal-magnetic-powder-containing resin paste is preferably about 0.27 mm. After the screen printing, heating is performed at a temperature of 160° C. for one hour to fully cure the metal-magnetic-powder-containing resin paste. As a result, the metal-magnetic-powder-containing resin layer 42 is obtained.
With the above processes, the metal-magnetic-powder-containing resin layer 42 is embedded also in the through holes 34a and 34b. As a result, a through hole magnetic body including the through hole magnetic body 42a illustrated in
Finally, a dicer is used to cut the substrates 2a and 2b along the cutting lines. As a result, individual coil components 1 corresponding to respective rectangular areas are obtained. Then, as illustrated in
As described above, according to the manufacturing method of the coil component 1 of the present embodiment, it becomes possible to produce the coil component 1 in which the top surfaces of the innermost and outermost turns of the respective planar spiral conductors 30b and 30c and the top surfaces of the lead-out conductors 31b and 31c are brought into contact and conduction with each other, whereas the top surfaces of the turns of the planar spiral conductor 30b other than the innermost and outermost turns, and turns of the planar spiral conductor 30c other than the innermost and outermost turns are electrically isolated from each other by the insulating resin film 41. Thus, it is possible to obtain a coil component in which a low DC resistance, a high inductance, and a reduction in height are achieved in a balanced manner.
Further, grinding is applied also to the planar spiral conductors 30a and 30d, so that the height of the coil component 1 is correspondingly further reduced.
Formation of the through hole magnetic bodies respectively at the corner portions of the substrates 2a and 2b (substrates 2a and 2b after cutting) and at the portions corresponding to the center portions of the planar spiral conductors 30a and 30b allows an increase in inductance of the coil component as compared with a case where the through hole magnetic bodies are not formed.
Further, the through hole 34a for forming a pangenetic path is formed before formation of the planar spiral conductors 30a and 30b and lead-out conductors 31a and 31b, so that the planar spiral conductors 30a and 30b can be formed so as to protrude in the through hole 34a, as illustrated in
Further, the magnetic path is formed not by the magnetic substrate, but by the metal-magnetic-powder-containing resin layer 42, so that it is possible to obtain a power supply choke coil excellent in DC superimposition characteristics.
As illustrated in
In the manufacturing process of the coil component 1 according to the present embodiment, film formation of the insulating resin after the grinding is applied also to at least one of the back surface 2ab of the substrate 2a and top surface 2bt of the substrate 2b (formation of a third insulating resin layer). As a result, as illustrated in
Further, also in the present embodiment, the grinding is applied also to the planar spiral conductors 30a and 30d, so that the height of the coil component 1 is correspondingly further reduced.
Although the eighth and ninth embodiments of the present invention are described above, the invention is not limited to the embodiments. It is a matter of course that the present invention can be conducted in various embodiments without departing from the scope of the present invention.
For example, in both the eighth and ninth embodiments, the top surfaces of the planar spiral conductors and those of the lead-out conductors are subjected to grinding to one degree or another. However, the grinding is conducted for the purpose of increasing the inductance and reducing the height of the coil component, and if such requirements are not made, the grinding may be omitted.
Further, in the coil component 1 described in the eighth and ninth embodiments, the metal-magnetic-powder-containing resin layer 42 corresponding to the upper and lower cores 15 and 16 described in the first to seventh embodiments has the through hole magnetic body 42a corresponding to the connection portion 15a; however, in place of, or in addition to the through hole magnetic body 42a, a through hole magnetic body corresponding to the connection portion 15b or connection portion 15d may be formed in the metal-magnetic-powder-containing resin layer 42. The coil component 60 illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-236855 | Oct 2010 | JP | national |
| 2011-118361 | May 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/073645 | 10/14/2011 | WO | 00 | 4/17/2013 |
