JP5858630B2 - Inductor-embedded substrate and electric circuit comprising the substrate - Google Patents

Description

  The present invention relates to a substrate with a built-in inductor (a substrate with a built-in inductor). The present invention also relates to an electric circuit comprising a substrate with a built-in inductor. Furthermore, the present invention also relates to a power supply circuit including a substrate with a built-in inductor, in particular, a DC / DC converter (DC-DC converter).

  As is well known, in recent years, high functionality has become prominent in portable communication terminals represented by mobile phones and smartphones. Specifically, in addition to a communication circuit as a mobile phone, a wireless communication circuit corresponding to a wireless LAN, Bluetooth (registered trademark), or the like, sensors such as GPS, magnetism, and gyro, and a small payment function were provided. The mounting of circuits for realizing various functions such as an electronic money terminal circuit is becoming common.

  The above enhancement of functionality is not limited to communication terminals, but various portable electronic devices (for example, personal digital assistants (PDAs), notebook computers, digital media players, Blu-ray discs / DVDs / CDs / MDs) Players, digital cameras, video cameras, etc.) have also been improved in various functions according to their use.

  In the above-described portable communication terminals and various electronic devices (hereinafter sometimes collectively referred to as “portable terminals”), there are of course certain restrictions on the size and shape of the portable terminals. Since the downsizing and low profile of the product are directly linked to the market value of the product, the downsizing and lowing of each circuit for the additional function as described above (hereinafter may be simply referred to as “additional circuit”). The demand for turning is very strong. Further, the demand for such downsizing and low profile is not only for these additional circuits but also for existing circuits (for example, power supply circuits for supplying appropriate power to these additional circuits). ing.

  By the way, many portable terminals as described above use a battery as a power source. On the other hand, the various additional circuits mounted on the mobile terminal are actually required to have various power supply voltages according to their configurations. Accordingly, these portable terminals include a voltage conversion device (for example, a power supply circuit such as a DC-DC converter) for converting the power supply voltage supplied by the battery into a predetermined operating voltage optimum for each additional circuit. It is common. Note that a DC-DC converter typically includes a semiconductor integrated circuit (switching IC) (active element) including a switching element and a control circuit, and passives such as an inductor (coil) and a capacitor for leveling the output voltage. It is configured as a discrete circuit obtained by connecting elements on a printed circuit board or the like on which connection lines are formed (see, for example, FIG. 1).

  As described above, in a mobile terminal, since one battery is shared by a plurality of circuits, it is important from the viewpoint of battery life to suppress deterioration of efficiency in the power supply circuit for each additional circuit. Further, in order to suppress the efficiency deterioration in each power supply circuit (for example, a DC-DC converter), it is particularly important to improve the superposition characteristics of the inductor and to reduce the direct current resistance. In order to improve the superposition characteristics of the inductor, it is effective to use a material having a lower magnetic permeability and wind a large number of conductors. However, this means that the inductor becomes larger. Further, in order to reduce the loss of the inductor, it is effective to increase the thickness of the coil wire constituting the inductor. However, in order to achieve the same inductance, the thicker the coil wire, the larger the outer diameter of the coil wire winding, and the larger the inductor.

  Therefore, in the DC-DC converter for portable terminals, for example, as in the specific example shown in FIG. 2, the switching IC is built in a resin substrate (for example, a PCB substrate), and the efficiency of the DC-DC converter is accordingly increased. Attempts have also been made to achieve good overlay characteristics and low loss in inductors by allowing inductors that have a large impact on degradation to occupy a large area. In the specific example shown in FIG. 2, in addition to the inductor, two general-purpose chip capacitors are mounted. Of these discrete components, the inductor occupies the largest area, and the inductor is the highest in height.

  Therefore, as an attempt to achieve both a reduction in size and height of an inductor and a reduction in resistance, for example, an inductor (coil) is embedded in a multilayer substrate made of resin or the like, and circuit elements other than the inductor are formed on the substrate. It has been proposed to arrange (see, for example, Patent Document 1). Further, for the purpose of further increasing the inductance of the inductor embedded in the substrate, it has been proposed to embed an inductor (coil) in the ferrite substrate (see, for example, Patent Document 2).

JP 7-163146 A JP 2010-238777 A

  As described above, various proposals have been made for downsizing and low-profile inductors. However, due to the recent progress of multi-functionalization of mobile terminals, various circuits (additional circuits accompanying multi-function and existing circuits such as power supply circuits) have been reduced in size and height. The demand is getting stronger. In addition, as described above, in various circuits including a power supply circuit such as a DC-DC converter, the size and height of an inductor that occupies a large area and height and has the greatest influence on the shape are reduced by overlapping the inductors. There is a problem that the efficiency of the DC-DC converter is deteriorated by degrading the characteristics, the DC resistance of the inductor is increased, and the loss in the DC-DC converter is increased.

  Incidentally, it has been recognized that when the current value of the current flowing through the coil increases, the inductance of the coil decreases. A characteristic that causes this problem is referred to as a “DC superposition characteristic”. More specifically, for example, when a current is passed through a coil composed of a conductor embedded in a magnetic material, the magnetic field generated around the coil increases as the current value increases, and the magnetic field is generated when the magnetic field is strong. This is due to the phenomenon that the magnetic permeability of the material decreases (magnetic saturation). This phenomenon is particularly noticeable in ferrite materials, which are magnetic materials widely used in DC-DC converters.

  Note that, as an index for evaluating the DC superimposition characteristics, in the measurement of the inductance while superimposing the DC current, the superimposed current value at which the inductance decreases by a predetermined ratio (for example, 10%, 30%, or 50%) is used. Can be mentioned. In the present specification, the superimposed current value at which the inductance is reduced by 30% is used as an index of the DC superimposed characteristic of the inductor and is referred to as “DC superimposed current”.

  When the phenomenon that the inductance of the coil decreases as the current value increases as described above occurs, for example, the function of smoothing the output voltage required for the coil in the power supply circuit decreases. As a result, the efficiency of the DC-DC converter is degraded due to not achieving the desired inductance. Furthermore, there is an increased possibility that an excessive current flows to the output side due to an output voltage that is not sufficiently smoothed. For example, a switching IC that causes a failure of an additional circuit included in the mobile terminal or constitutes a DC-DC converter. There is a high possibility that a malfunction will occur.

  Therefore, in order to appropriately maintain the efficiency of the DC-DC converter and the smoothing function of the output voltage by the inductor, it is necessary to suppress a decrease in inductance due to the direct current superposition characteristics. It is known that the DC superimposition characteristic is improved by suppressing the increase (concentration) of the magnetic flux density by increasing the shape of the coil or the like because it is generated by the magnetic saturation accompanying the increase of the magnetic flux density as described above. ing. However, this case also conflicts with the demands for miniaturization and low profile required for portable terminals.

  As described above, in order to meet the demands for miniaturization and low profile of various circuits in portable terminals, it is necessary to miniaturize and reduce the height of inductors that occupy the largest area and height in various circuits. The downsizing and low profile of an inductor are in a trade-off relationship with an increase in loss (increase in DC resistance) and a decrease in DC superimposition current value (concentration of magnetic flux density due to DC superimposition characteristics). There is a continuing demand for satisfactory inductors. That is, an object of the present invention is to provide an inductor that has both a low DC resistance and an improved DC superposition characteristic while satisfying the demand for circuit size reduction and height reduction.

The above purpose is
A substrate mainly comprising a magnetic material,
A first coil made of a conductor embedded in the substrate;
A raised portion mainly including a magnetic material disposed on at least one surface of the substrate, and a second coil made of a conductor embedded in the raised portion,
Comprising
The cross-sectional area of the raised portion is smaller than the cross-sectional area of the substrate due to a plane parallel to the one surface of the substrate;
According to a plane perpendicular to the central axis of the coil, that the cross-sectional area of the second coil is smaller than the cross-sectional area of the first coil, and said second coil are connected to electrical to said first coil,
This is achieved by a substrate with a built-in inductor.

  As described above, the inductor-embedded substrate according to the present invention includes the first coil embedded in the substrate including the magnetic material and the second coil embedded in the raised portion including the magnetic material. . Therefore, a larger space can be allocated to the inductor as compared with the case where the coil is embedded only in the substrate as in the above-described prior art or the coil is disposed on the substrate as a discrete component. As a result, as with inductors that have been reduced in size and height in the prior art, the loss increases as the DC resistance of the coil increases, and the DC superimposition characteristics deteriorate as the coil size and height decreases. Is avoided. In addition, in the space on the substrate where the raised portion is not formed and / or the space above the raised portion, circuit elements other than the inductor built in the substrate with built-in inductor according to the present invention (for example, capacitors, various ICs (integrated) Circuit) etc.) and terminals etc. can be provided, so that the entire circuit can be sufficiently reduced in size and height.

It is a circuit diagram which shows the structure of a typical DC-DC converter. It is sectional drawing (a) and the top view (b) which show schematic structure of the DC-DC converter which concerns on a prior art. It is sectional drawing (a) and a top view (b) which show schematic structure of the DC-DC converter to which the board | substrate with a built-in inductor concerning one embodiment of this invention was applied. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on one embodiment as a comparative example. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on another embodiment as a comparative example. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on one embodiment as an Example of this invention. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on another embodiment as an Example of this invention. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on another embodiment as a comparative example. It is a perspective view which shows the external appearance of the board | substrate with a built-in inductor which concerns on another embodiment as a comparative example shown in FIG. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on another embodiment as a comparative example. It is a perspective view which shows schematic structure of the board | substrate with a built-in inductor which concerns on another embodiment as an Example of this invention. It is a graph showing the relationship between the direct current resistance and the superimposed current in various inductor-embedded substrates.

  As described above, an object of the present invention is to provide an inductor having both a low DC resistance and an improved DC superposition characteristic while satisfying the demand for circuit miniaturization and low profile.

  As a result of diligent research to achieve the above object, the present inventor has not only embedded a coil in the substrate as in the prior art, but also arranged a relatively thick (high height) circuit element on the substrate. By providing a raised part in the area where it is not installed, embedding a coil in this raised part, and electrically connecting these coils to form an inductor, the inductor is reduced in size and reduced in height in the prior art. In addition, while avoiding the increase in loss due to the increase in DC resistance of the coil and the deterioration of the DC superposition characteristics due to the reduction in size and height of the coil, the overall size and height of the circuit can be reduced. It came to conceive that it will be achieved.

That is, the first aspect of the present invention is:
A substrate mainly comprising a magnetic material,
A first coil made of a conductor embedded in the substrate;
A raised portion mainly including a magnetic material disposed on at least one surface of the substrate, and a second coil made of a conductor embedded in the raised portion,
Comprising
The cross-sectional area of the raised portion is smaller than the cross-sectional area of the substrate due to a plane parallel to the surface of the substrate;
The cross-sectional area of the second coil is smaller than the cross-sectional area of the first coil due to a plane perpendicular to the central axis of the coil, and the second coil is directly or indirectly electrically connected to the first coil. is being done,
It is a board | substrate with a built-in inductor characterized by these.

  As described above, the substrate included in the inductor-embedded substrate according to the first aspect of the present invention is mainly composed of a magnetic material. The magnetic material used in the substrate is not limited as long as it is a magnetic material that can be used as an inductor core material or the like, for example, but is widely used as an inductor core material (for example, Ni-Cu-Zn ferrite etc.) are desirable. In addition, the size and shape (for example, area, thickness, etc.) of the substrate depend on the application and required characteristics of the circuit to which the inductor-embedded substrate is applied, the size and shape of the first coil embedded in the substrate, etc. , Designed as appropriate.

  Similarly, the raised portion included in the inductor-embedded substrate according to the first aspect of the present invention is mainly composed of a magnetic material. The magnetic material used in the raised portion is not limited as long as it is a magnetic material that can be used as an inductor core material or the like. For example, a ferrite widely used as an inductor core material (for example, Ni-Cu-Zn-based ferrite, etc.) are desirable. In addition, the magnetic material which comprises the board | substrate and the protruding part which are contained in the board | substrate with a built-in inductor which concerns on the 1st aspect of this invention may be the same, or may differ.

  In addition, the size and shape (for example, area, thickness, etc.) of the raised portion on the substrate included in the inductor-embedded substrate according to the first aspect of the present invention are the application and required characteristics of the circuit to which the inductor-embedded substrate is applied, Not only the size and shape of the second coil embedded in the raised portion, but also the size, shape and number of other circuit elements disposed on the substrate included in the inductor-embedded substrate according to the first aspect of the present invention. It is designed according to etc. In other words, the space on the substrate where the raised portion is not formed and / or the space above the raised portion is a circuit element other than the inductor built in the inductor-embedded substrate according to the first aspect of the present invention (for example, a capacitor, Various ICs (integrated circuits, etc.) and terminals are provided. As a result, as described above, the cross-sectional area by the plane parallel to the surface of the substrate of the raised portion on the substrate included in the inductor-embedded substrate according to the first aspect of the present invention is smaller than the cross-sectional area of the substrate.

  In order to increase the inductance, the first coil and the second coil made of the conductor embedded in the substrate and the raised portion included in the substrate with a built-in inductor according to the first aspect of the present invention ( It is desirable to make their cross-sectional areas as large as possible (by a plane perpendicular to the central axis). In other words, the first coil and the second coil have a cross-sectional area as large as possible unless problems such as a decrease in magnetic permeability due to magnetic saturation caused by thinning of the magnetic material around the coil occur. B) It is desirable that it is wound as large as possible. Accordingly, the cross-sectional area of the raised portion parallel to the plane of the substrate is smaller than the cross-sectional area of the substrate. As a result, the cross-sectional area of the second coil due to the plane perpendicular to the central axis of the coil is It is desirable to be smaller than the cross-sectional area of the coil.

  By allocating a larger space to the inductor, compared to the conventional technology, this achieves sufficient inductance while increasing the loss accompanying the increase in the DC resistance of the coil, and reducing the size and height of the coil. The accompanying deterioration of the DC superimposition characteristic is avoided. In addition, a circuit element other than the inductor built in the substrate with a built-in inductor according to the first aspect of the present invention (for example, a capacitor, various ICs (integrated circuits), etc.) is provided in the space on the substrate where the raised portion is not formed. In the electric circuit using the inductor-embedded substrate according to the first aspect of the present invention, further downsizing and lowering the height of the circuit over the prior art can be achieved.

  The inductor according to the first aspect of the present invention can also be configured by configuring an element corresponding to the raised portion and the second coil embedded therein as a discrete component, and disposing the discrete component on the substrate. It can be considered that a configuration similar to that of the built-in substrate can be obtained. However, in such a configuration, an extra space (height) corresponding to the connection point between the discrete component and the board is required, so that the above-mentioned demands for downsizing and low profile are met. Becomes difficult.

  By the way, circuit elements constituting various electric circuits include relatively thick circuit elements (for example, various capacitors) that are relatively thick (height in a direction perpendicular to the circuit board surface), and relatively thin (circuit boards). There are also circuit elements (for example, various ICs) whose height in a direction perpendicular to the surface is small. Therefore, if the design specifications of the inductor (including the first coil and the second coil) built in the inductor built-in substrate (the substrate and the raised portion) according to the first aspect of the present invention are possible, A difference is provided between the thickness (height) of the relatively thick circuit element and the thickness (height) of the raised portion, and a relatively thin circuit element (for example, a switching IC) is formed in the space above the raised portion caused by this difference. Various ICs including the above may be provided. As a result, the entire circuit can be further reduced in size and height.

  As described above, the size and shape of the raised portion are not limited to the use and required characteristics of the circuit to which the inductor-embedded substrate is applied, the size and shape of the second coil embedded in the raised portion, and the like. It is designed as appropriate according to the size, shape, number, etc. of other circuit elements disposed on the substrate included in the inductor-embedded substrate according to the first aspect of the invention. Therefore, for example, a raised portion is provided on the peripheral portion of the substrate included in the inductor-embedded substrate according to the first aspect of the present invention, and a concave portion surrounded by the raised portion is formed in the vicinity of the central portion of the substrate. It is also conceivable to arrange other circuit elements, terminals and the like. However, such a configuration in which a cavity (cavity) is provided in a portion corresponding to the inside of the second coil is not preferable as a raised portion included in the inductor-embedded substrate according to the first aspect of the present invention.

  As described above, the raised portion is provided on the peripheral portion of the substrate included in the inductor-embedded substrate according to the first aspect of the present invention, and the cavity surrounded by the raised portion is formed in the upper portion near the central portion of the substrate. Examples of the reason why the configuration in which other circuit elements are arranged in the cavity are not preferable include the following.

  First, in order to realize a reduction in size and height in an electric circuit using an inductor built-in substrate having the above configuration, circuit elements, terminals, etc. other than the inductor built in the inductor built-in substrate according to the first aspect of the present invention Must be placed in the cavity. However, the cavity is arranged so as to be surrounded by the second coil, and the bottom of the cavity faces the top of the core of the first coil. Therefore, the magnetic flux generated from the first coil and the second coil may adversely affect the circuit elements disposed in the cavity.

  Next, since there is no magnetic material in the cavity portion, the magnetic permeability of the entire inductor-embedded substrate is lowered, so that the inductance of the entire inductor-embedded substrate is also lowered, and a cavity is provided. For this reason, the magnetic material in the vicinity of the second coil must be thinned or the conductive wire of the second coil must be made thin and long. As a result, the magnetic flux tends to concentrate in the vicinity of the second coil (magnetic saturation is reduced). There is an increased risk of increasing the number of locations) and increasing the DC resistance value of the second coil as the conductive wire of the second coil becomes thinner and longer.

  The cavity is assumed to be a cavity (recess) having a size that allows other circuit elements, terminals, and the like to be disposed therein. That is, the above discussion on the disadvantages associated with providing the cavity is, for example, for the purpose of ensuring electrical connection with the conductive wires of the respective coils embedded in the inductor-embedded substrate according to the first aspect of the present invention. For example, it is not excluded to provide a relatively small hole such as a via hole in the raised portion or the substrate of the inductor-embedded substrate according to the first aspect of the invention.

  By the way, the first coil made of a conductor embedded in the substrate and the second coil made of a conductor embedded in the raised portion may be a wound coil or a laminated coil. When these coils are wire-wound coils, for example, the coil formed in advance with a conductor such as metal is electrically connected, and a molding die having a molding space having a shape corresponding to the substrate and the raised portion is used. In the first embodiment of the present invention, the slurry is fixed at a predetermined position, and a slurry of a magnetic material (for example, ferrite) is injected into the mold by, for example, a gel cast method, and the slurry is solidified and fired. Such an inductor-embedded substrate can be obtained.

  On the other hand, when these coils are laminated coils, a thin plate-like green sheet is manufactured from the magnetic material slurry as described above, for example, by a doctor blade method or the like. By stacking and integrating the necessary number of conductor patterns formed on the green sheet by a printing method (for example, screen printing method, etc.), forming the conductor pattern as a coil, and then firing it In addition, the inductor-embedded substrate according to the first aspect of the present invention can be obtained.

  Or, for example, by a printing method such as a screen printing method on a protective substrate such as a magnetic material sheet or a resin film manufactured from a magnetic material slurry using a doctor blade method or a gel cast method. Conductor pattern is provided, and the conductive pattern obtained by injecting a slurry of magnetic material into the part where the conductor pattern is not provided using a gel cast method, etc., and solidifying the slurry is embedded. The inductor-embedded substrate according to the first aspect of the present invention can also be obtained by laminating a required number of sheets of the magnetic material, forming a conductor pattern as a coil, and firing.

  Incidentally, the conductor pattern is formed by, for example, using a conductive paste containing at least one metal selected from gold, silver, copper or the like as a main component and a thermosetting resin precursor, for example, a method such as screen printing. Formed by printing. Moreover, as said thermosetting resin precursor, a phenol resin, a resole resin, a urethane resin, an epoxy resin, a melamine resin etc. can be used, for example. Of these, phenol resins and resol resins are particularly preferable. After the conductor paste is printed, the conductor pattern is obtained by curing the binder contained in the conductor paste.

  The above-described method for manufacturing a substrate with a built-in inductor according to the first aspect of the present invention is merely an example, and the method for manufacturing a substrate with a built-in inductor according to the first aspect of the present invention is limited to these specific methods. It is not a thing.

  As described above, in the inductor-embedded substrate according to the first aspect of the present invention, the first coil made of the conductor embedded in the substrate and the second coil made of the conductor embedded in the raised portion are directly connected. Connected electrically or indirectly. That is, a larger space can be allocated to the inductor as compared with the case where the coil is embedded only in the substrate as in the prior art or the coil is disposed on the substrate as a discrete component. In the case of an inductor having a reduced size and a reduced height, it is possible to avoid an increase in loss due to an increase in the DC resistance of the coil and a deterioration in DC superposition characteristics due to a reduction in the size and the height of the coil.

  Further, in the space on the substrate where the raised portion is not formed and / or the space above the raised portion, circuit elements other than the inductor built in the inductor built-in substrate according to the first aspect of the present invention (for example, a capacitor, Various ICs (integrated circuits, etc.), terminals and the like can be provided. As a result, in the electric circuit to which the substrate with a built-in inductor according to the first aspect of the present invention is applied, downsizing and reduction in height over the conventional technique can be achieved as a whole circuit.

  By the way, in general, the coil is configured such that the spiral structure of the conductor has a cylindrical shape (for example, a cylindrical shape, a rectangular tube shape, or the like). Therefore, in the first coil and the second coil included in the inductor-embedded substrate according to the first aspect of the present invention, the spiral structure of the conductor also has a cylindrical shape (for example, a cylindrical shape, a rectangular tube shape, etc.). Generally, it is configured as follows. That is, in the inductor-embedded substrate according to the first aspect of the present invention, the raised portion in which the second coil having a cylindrical shape (for example, a cylindrical shape, a rectangular tube shape, etc.) is embedded is columnar (for example, In general, it has a cylindrical shape, a prismatic shape, or the like.

  However, the shape of the raised portion in the inductor-embedded substrate according to the present invention is not necessarily columnar (for example, cylindrical, prismatic, etc.). For example, the raised portion in the inductor-embedded substrate according to the present invention depends on the manufacturing reason and the shape of the circuit element arranged adjacent to the raised portion on the surface of the substrate on which the raised portion is not arranged. For example, you may have a cone shape (for example, cone shape, pyramid shape, etc.). As a result, the second coil embedded in the raised portion may also have, for example, a cone shape (for example, a cone shape, a pyramid shape, etc.).

  In addition, as described above, circuit elements (for example, capacitors, various ICs (integrated circuits), etc.) other than the inductor built in the inductor built-in substrate according to the present invention, terminals, and the like are arranged in the space above the raised portion. It can also be set up. In this case, a plurality of circuit elements and terminals having different heights may be provided on the top surface of the raised portion, for example, by providing a step on the top surface of the raised portion. In this way, when the step is provided on the top surface of the raised portion, the second coil has a lower magnetic permeability due to magnetic saturation accompanying thinning of the magnetic material around the coil as described above. Unless a problem arises, it is desirable to wind as much as possible so as to have as large a cross-sectional area as possible.

  That is, when a step is provided on the top surface of the raised portion as described above (that is, when the shape of the top portion of the raised portion is stepped), the shape of the second coil embedded in the raised portion is the height of the raised portion. It is desirable to correspond to the shape of the part. Specifically, the shape of the second coil is configured such that the cross-sectional area of the second coil embedded in the raised portion changes stepwise corresponding to the shape of the top surface of the raised portion. Is desirable.

  Further, for example, in the vicinity of the boundary region between the raised portion and the substrate in the inductor-embedded substrate according to the present invention due to manufacturing reasons, mechanical strength required for the raised portion, or any other reason, for example, a tapered shape A shape that continuously connects the side surface of the raised portion and the surface of the substrate may be formed.

  Corresponding to the above, at least one turn of the conductive material embedded in the region of the substrate and / or the raised portion corresponding to the vicinity of the connection region between the first coil and the second coil embedded in the inductor-embedded substrate according to the present invention. An intermediate coil made of a body may be further arranged. The spiral structure of the conductor of the intermediate coil includes a cross section (by a plane perpendicular to the central axis of the coil) at the end on the second coil side of the spiral structure of the conductor of the first coil, and the conductor structure of the second coil. You may form so that the cross section (by the plane perpendicular | vertical to the central axis of a coil) in the edge part by the side of the 1st coil of a helical structure may be connected continuously.

  When the number of turns of the conductor of the intermediate coil is small, it may be difficult to specify the shape of the spiral structure of the conductor. In such a case, the shape of the spiral structure of the conductor of the intermediate coil does not necessarily have the shape as described above, and the conductor of the intermediate coil is the first coil at the end of the first coil on the second coil side. What is necessary is just to be arrange | positioned in the position corresponding to the shape which connects a cross section and the cross section of the 2nd coil in the edge part by the side of the 1st coil of a 2nd coil continuously.

  Further, the intermediate coil is not only disposed in the vicinity of the connection region between the first coil and the second coil as described above, but, for example, when the top of the raised portion has a stepped shape as described above. The second coil may be provided at a location where the cross-sectional area changes stepwise. As a result, the shape of the top of the second coil embedded in the raised portion having a stepped shape may have a continuous cone shape (for example, a cone shape, a pyramid shape, etc.).

  As described above, in the substrate with a built-in inductor according to the present invention, for example, on the surface of a substrate on which a raised portion is not provided, for manufacturing reasons, the circuit element provided adjacent to the raised portion. Corresponding to the shape and the like, the raised portion can have various shapes, and in response to this, the second coil embedded in the raised portion can also have various shapes. Furthermore, as described above, the intermediate coil is disposed in the region where the cross-sectional area of the coil (including the first coil and the second coil) included in the inductor-embedded substrate according to the present invention changes discontinuously, You may make it the cross-sectional area of a coil change continuously. In addition, since the said intermediate coil can be manufactured by the method similar to the above-mentioned 1st coil and 2nd coil, the detailed description about the material and manufacturing method of an intermediate coil is omitted here.

  As a further measure for increasing the inductance of the whole substrate with built-in inductor, for example, multiplexing of coils included in the substrate with built-in inductor can be mentioned. Coil multiplexing can be performed for both or either of the first and second coils described above. In addition, a coil newly added for coil multiplexing can be arranged inside and / or outside the target coil.

  However, in the raised portion included in the substrate with built-in inductor according to the present invention, there is little room in space, so when attempting to multiplex coils, the magnetic material near the coil is made thinner or the conductor is made thinner. As a result, there is a possibility that the direct current superimposition characteristics of the coil are deteriorated and the loss accompanying the increase of the direct current resistance of the coil is increased. Therefore, it is desirable that the multiplexing of the coil is performed in a substrate included in the inductor-embedded substrate according to the present invention.

That is, the substrate with a built-in inductor according to the second aspect of the present invention is
The substrate with a built-in inductor according to the first aspect of the present invention,
A third coil made of a conductor embedded in the substrate, further comprising a third coil that is directly or indirectly electrically connected to at least one of the first coil and the second coil; And the third coil is formed inside and / or outside the first coil,
It is a board | substrate with a built-in inductor characterized by these.

Since the third coil can be manufactured by the same method as the first coil and the second coil described above, a detailed description of the material and manufacturing method of the third coil is omitted here.
As described above, according to the inductor-embedded substrate according to the second aspect of the present invention, the third coil is formed inside and / or outside of the first coil made of the conductor embedded in the substrate, whereby the inductor The inductance of the entire built-in substrate can be further increased.

  By the way, at both ends in the central axis direction of the coil, the directions of magnetic fluxes generated from the respective conductive wires constituting the coil are easily aligned. Therefore, for example, when the thickness of the magnetic material in the vicinity of both end portions in the central axis direction of the coil is insufficient (thin), the direct current superimposition characteristics due to magnetic saturation are likely to deteriorate at that location.

  In order to avoid such deterioration of the superposition characteristics, it is necessary to suppress magnetic saturation due to concentration of magnetic flux at both ends in the central axis direction of the coil. Such measures include, for example, disposing at least one nonmagnetic layer mainly including a nonmagnetic material in the magnetic material constituting the substrate and / or the raised portion included in the inductor built-in substrate. .

  As described above, when a nonmagnetic layer is disposed on the substrate and / or the raised portion included in the inductor-embedded substrate, the magnetic layers facing each other with the nonmagnetic layer interposed therebetween (consisting mainly of a magnetic material of the substrate and / or the raised portion) The magnetic flux generated from the coil (for example, the first coil, the second coil, etc.) embedded in the portion) is blocked by the nonmagnetic layer. As a result, magnetic saturation due to concentration of magnetic flux at both ends in the central axis direction of the coil as described above is suppressed, and deterioration of the superposition characteristics as described above is avoided.

Therefore, the inductor-embedded substrate according to the third aspect of the present invention is
An inductor-embedded substrate according to either the first aspect or the second aspect of the present invention,
The magnetic material constituting the substrate and / or the raised portion further includes at least one nonmagnetic layer mainly including a nonmagnetic material, and the nonmagnetic layer includes the first coil to the first coil. Being configured to intersect the central axis of at least one of the third coils,
It is a board | substrate with a built-in inductor characterized by these.

The nonmagnetic layer is manufactured by using a nonmagnetic material slurry instead of the magnetic material slurry by the same method as the magnetic material constituting the substrate and / or the raised portion included in the inductor built-in substrate, for example. Can do. The non-magnetic material can withstand the manufacturing process of the substrate with a built-in inductor including the substrate, the raised portion, and various coils, and has a sufficiently low magnetic permeability (preferably about 1.0). The material is not limited to a specific material as long as it has a magnetic permeability), and examples thereof include nonmagnetic ferrite such as Zn-based ferrite and Cu-based ferrite, and glass ceramic. Among these, Cu—Zn-based ferrite which is a solid solution having a positive spinel structure represented as X—Fe ₂ O ₄ (X is Cu, Zn) is preferable.

  In addition, the nonmagnetic layer may include one or a plurality of layers on both or either one of the substrate and the raised portion included in the inductor built-in substrate, depending on the configuration of various coils included in the inductor built-in substrate and the intended use. A layer can be provided. In order to achieve the object of blocking the magnetic flux generated from the coil embedded in the opposing magnetic layer across the nonmagnetic layer as described above, the thickness of the nonmagnetic layer is preferably 5 μm or more. More preferably, it is 10 μm or more.

  Further, the non-magnetic layer blocks the magnetic flux generated from the coil embedded in the opposing magnetic layer with the non-magnetic layer sandwiched therebetween as described above, thereby concentrating the magnetic flux at both ends in the central axis direction of the coil. Arranged for the purpose of magnetic saturation. Therefore, in order to effectively achieve such an object, it is necessary that the nonmagnetic layer is configured to intersect with the central axis of the target coil that is intended to block the magnetic flux.

  As described above, according to the inductor-embedded substrate according to the third aspect of the present invention, the magnetic flux generated from the coil embedded in the opposing magnetic layer with the nonmagnetic layer interposed therebetween is blocked by the nonmagnetic layer. Deterioration of superposition characteristics due to magnetic saturation due to magnetic flux concentration at both ends in the central axis direction of the coil is suppressed.

  As described above, the configuration and superiority of the inductor-embedded substrate according to various embodiments of the present invention have been described. As described above, the object of the present invention is, for example, the miniaturization / reduction of various electric circuits included in portable terminals and the like. An object of the present invention is to provide an inductor having both a low DC resistance and an improved DC superposition characteristic while satisfying the demand for a low profile. Conversely, the substrate with a built-in inductor according to the present invention maintains, for example, low DC resistance and improved DC superposition characteristics, while reducing the size and height of various electric circuits included in mobile terminals, for example. The purpose is to meet the requirements.

Therefore, the fourth aspect of the present invention is
An electric circuit comprising an inductor-embedded substrate according to any one of the first to third aspects of the present invention.

  As described above, the inductor-embedded substrate according to the present invention includes the first coil embedded in the substrate including the magnetic material and the second coil embedded in the raised portion including the magnetic material. . Therefore, a larger space can be allocated to the inductor as compared with the case where the coil is embedded only in the substrate as in the prior art or the coil is disposed as a discrete component on the substrate. As a result, as with inductors that have been reduced in size and height in the prior art, the loss increases as the DC resistance of the coil increases, and the DC superimposition characteristics deteriorate as the coil size and height decreases. Is avoided. In addition to such advantages, a circuit element (for example, a capacitor, etc.) other than the inductor built in the inductor built-in substrate according to the present invention may be included in the space on the substrate where the raised portion is not formed and / or the space above the raised portion. Since various ICs (integrated circuits, etc.) and terminals can be arranged, the entire circuit can be reduced in size and height over the prior art.

  By the way, as described above, the demand for miniaturization and low profile for various electric circuits is particularly strong in portable terminals. Further, in order to realize the recent multi-functionalization, various additional circuits are mounted on the mobile terminal, and various power supply voltages are supplied to these additional circuits according to the respective configurations. There is a need. On the other hand, many portable terminals use a battery as a power source. Therefore, the mobile terminal needs to have a power supply circuit for converting the power supply voltage supplied by the battery into an operating voltage optimum for various additional circuits, and the power supply circuit realizes a function of smoothing the output voltage. An inductor is required as an element to perform. Moreover, in a mobile terminal, since one battery is shared by a plurality of circuits, it is important from the viewpoint of battery life to suppress loss in the power supply circuit. In view of this situation, the inductor-embedded substrate according to the present invention is preferably used as an inductor for a power supply circuit.

That is, the fifth aspect of the present invention is
The electric circuit according to the fourth aspect of the present invention, wherein the electric circuit constitutes a power supply circuit.

  By the way, in the power supply circuit as described above, in order to achieve high efficiency regardless of the current value and to stably realize the function of smoothing the output voltage, as described above, the increase in the value of the current flowing through the inductor It is desirable to use an inductor having good direct current superposition characteristics that is unlikely to cause a decrease in magnetic permeability in a magnetic material due to magnetic saturation caused by the magnetic field. If an inductor with low DC superimposition characteristics is used, the efficiency of the DC-DC converter will deteriorate, the output voltage will not be smoothed sufficiently, an excessive current will flow to the output side of the inductor, and other inductors connected to the output side will There is a risk of failure of circuit elements and other circuits. In particular, for switching ICs that constitute DC / DC converters (DC-DC converters), it is extremely important to maintain high efficiency regardless of current value and to stably perform supply voltage smoothing. . In view of such a situation, the substrate with a built-in inductor according to the present invention is preferably used as an inductor for a DC / DC converter.

That is, the sixth aspect of the present invention is
The electric circuit according to the fifth aspect of the present invention, wherein the power supply circuit constitutes a DC / DC converter.
As described above, the DC / DC converter (DC-DC converter) is one of the applications that can maximize the advantages of the substrate with a built-in inductor according to the present invention.

  As described above, according to the inductor built-in substrate according to the present invention, compared to the case where the coil is embedded only in the substrate as in the prior art or the coil is disposed on the substrate as a discrete component, More space can be allocated to the inductor. As a result, as with inductors that have been reduced in size and height in the prior art, the loss increases as the DC resistance of the coil increases, and the DC superimposition characteristics deteriorate as the coil size and height decreases. Is avoided.

  In addition, in the space on the substrate where the raised portion is not formed and / or the space above the raised portion, circuit elements other than the inductor built in the substrate with built-in inductor according to the present invention (for example, capacitors, various ICs (integrated) Circuit) etc.) and terminals etc. can be provided, so that the entire circuit can be sufficiently reduced in size and height. That is, according to the substrate with a built-in inductor according to the present invention, the object of providing an inductor having both a low DC resistance and an improved DC superimposition characteristic while satisfying the demand for circuit miniaturization and low profile is achieved. Is done.

  Hereinafter, a substrate with a built-in inductor according to some embodiments of the present invention will be described with reference to the accompanying drawings. However, the following description is for illustrative purposes only, and the scope of the present invention should not be construed as being limited to the following description.

1. Various inductor internal configuration table 1 of the substrate shows a structure and characteristics of the various inductor embedded substrate manufactured as examples illustrating the superiority of the present invention. First, the configuration of various inductor-embedded substrates will be described. In addition, all the various samples manufactured as examples are laminated with a necessary number of layers obtained by injecting a magnetic material or a non-magnetic material by a gel casting method on a conductor pattern arranged by a screen printing method. The conductor pattern was formed as a coil and fired.

However, in the various examples and comparative examples described here, the conductor paste was constituted by adding thermosetting phenol resin, butyl carbitol acetate, and melamine resin powder to silver (Ag). The amount of melamine resin powder was adjusted so that the shrinkage difference between the magnetic part (ferrite) and the coil part (conductor part) during firing was as small as possible.
In various examples and comparative examples, the ferrite material of the magnetic layer was Ni—Cu—Zn-based ferrite, and the ferrite material of the non-magnetic layer was Cu—Zn-based ferrite.

  Furthermore, the thicknesses of the magnetic material and nonmagnetic material layers were both 20 μm (however, the thicknesses of the nonmagnetic layers in the samples CVTYW and CVTYN having a cavity structure were 100 μm and 150 μm, respectively). Furthermore, the coils in the various samples had a square columnar spiral structure, and the number of turns was counted as 0.25 per side of the cross section. In the drawings showing the configurations of various samples described below, the nonmagnetic layer is not shown in order to make the structure of the coil embedded in the substrate or the raised portion easier to see.

  A sample indicated by the number “LL310” (hereinafter, simply referred to as “sample LL310”. The same applies to other samples) is a sample as a comparative example. Specifically, unlike the substrate with a built-in inductor according to the present invention, the sample LL310 is provided with only a coil embedded in a substrate made of ferrite as a magnetic material, without a raised portion on the substrate. (See FIG. 4). More specifically, as shown in Table 1, the sample LL310 has outer dimensions of a width of 2.9 mm, a depth of 2.3 mm, and a height (thickness) of 0.4 mm. In this ferrite substrate, a coil having a winding number of 3.25 is formed by a conductor pattern having a width of 220 μm and a height (thickness) of 10 μm. In Sample LL310, as shown in Table 1, one nonmagnetic layer is disposed between the second and third layers from the bottom among the layers including the conductor pattern. Has been.

Sample LL320 is a sample as a comparative example having the same configuration as sample LL310 except that a thicker conductor pattern having a width of 195 μm and a height (thickness) of 20 μm is used. As described above, the sample LL310 and LL 3 20 is sample as a comparative example corresponding to only consist of component substrate portion in the inductor embedded substrate according to the present invention.

  Next, the sample SH410 is a comparative example corresponding to the configuration in which the samples LL310 and LL320 include only the substrate portion of the inductor-embedded substrate according to the present invention, whereas the sample SH410 includes only a raised portion having a smaller planar area than these. It is a comparative example corresponding to a structure. Specifically, unlike the inductor built-in substrate according to the present invention, the sample SH410 includes only a coil embedded in a raised portion made of ferrite as a magnetic material (however, the height (thickness of the raised portion)). ) Is the height (thickness) corresponding to the sum of the height (thickness) of the substrate and the height (thickness) of the raised portion in the inductor-embedded substrate according to the present invention) (see FIG. 5).

  More specifically, as shown in Table 1, the sample SH410 has outer dimensions of 2.3 mm in width, 1.3 mm in depth, and 0.6 mm in height (thickness). A coil having a winding number of 4.25 is formed in the ferrite raised portion by a conductor pattern having a width of 195 μm and a height (thickness) of 10 μm. In sample SH410, as shown in Table 1, among the layers including the conductor pattern, the second layer from the bottom and the third layer, and the fourth layer from the bottom and 5 One non-magnetic layer (that is, a total of two layers) is disposed between the second layer and the second layer.

  Sample SH420 is a sample as a comparative example having the same configuration as sample SH410 except that a thicker conductor pattern having a width of 185 μm and a height (thickness) of 20 μm is used.

  Next, sample SH610 has the same configuration as sample SH410 except that a conductor pattern having a width of 250 μm and a height (thickness) of 10 μm is used, and the number of windings of the conductor pattern is 6.25. It is a sample as a comparative example. Sample SH620 is a sample as a comparative example having the same configuration as sample SH610 except that a thicker conductor pattern having a width of 235 μm and a height (thickness) of 20 μm is used. As described above, the samples SH410, SH420, SH610, and SH620 are comparative examples corresponding to the configuration including only the raised portions in the inductor-embedded substrate according to the present invention.

  On the other hand, sample BC610 is an example corresponding to the inductor-embedded substrate according to one embodiment of the present invention, in which a raised portion is disposed at the center of the substrate. Specifically, the sample BC 610 includes a first coil embedded in a substrate made of ferrite as a magnetic material and a second coil embedded in a raised portion made of ferrite as a magnetic material (FIG. 6). More specifically, as shown in Table 1, the sample BC610 has a width of 2.9 mm in width, a depth of 2.3 mm, and a height (thickness) of 0.4 mm in the center on the substrate. It has an appearance in which raised portions having outer dimensions of 1.3 mm, a depth of 2.3 mm, and a height (thickness) of 0.2 mm are disposed.

  In the ferrite substrate, a first coil having a winding number of 4.25 is formed by a conductor pattern having a width of 325 μm and a height (thickness) of 10 μm. In addition, a second coil having a winding number of 2.25 is formed in the raised portion made of ferrite by a conductor pattern having a width of 325 μm and a height (thickness) of 10 μm. In Sample SH410, as shown in Table 1, among the layers including the conductor pattern, between the first layer and the second layer from the bottom and the fifth layer from the bottom in the substrate. And a sixth layer (corresponding to the bottom layer in the ridge), respectively, and one layer between the second and third layers from the bottom in the ridge (ie, total) 3 layers) of nonmagnetic layers are provided.

  In addition, the sample BC 620 has the same configuration as the sample BC 610 except that a thicker conductor pattern having a width of 300 μm and a height (thickness) of 20 μm is used. The inductor according to another embodiment of the present invention It is a sample as an example corresponding to a built-in substrate. As described above, the samples BC610 and BC620 are examples corresponding to the inductor-embedded substrate according to the present invention.

  Next, in the sample BE610, in the samples BC610 and BC620, the raised portion is arranged at the center portion on the substrate, whereas the raised portion is arranged close to one end on the substrate. It is an Example corresponding to the board | substrate with a built-in inductor which concerns on another embodiment of this invention. Specifically, the sample BE610 includes a first coil embedded in a substrate made of ferrite as a magnetic material, and a raised portion made of ferrite as a magnetic material disposed close to one end on the substrate. The second coil is embedded in (see FIG. 7).

  More specifically, as shown in Table 1, sample BE610 is brought to one end on a substrate having outer dimensions of 2.9 mm width, 2.3 mm depth, and 0.4 mm height (thickness). Thus, it has an appearance in which raised portions having outer dimensions of 1.3 mm in width, 2.3 mm in depth, and 0.2 mm in height (thickness) are disposed. In this ferrite substrate, a first coil having a winding number of 4.25 is formed by a conductor pattern having a width of 336 μm and a height (thickness) of 10 μm. In addition, a second coil having a winding number of 2.25 is formed in the ferrite raised portion by a conductor pattern having a width of 336 μm and a height (thickness) of 10 μm. In Sample BE610, as shown in Table 1, among the layers including the conductor pattern, the first and second layers from the bottom and the fifth layer from the bottom in the substrate. And a sixth layer (corresponding to the bottom layer in the ridge), respectively, and one layer between the second and third layers from the bottom in the ridge (ie, total) 3 layers) of nonmagnetic layers are provided.

  In addition, the sample BE 620 has the same configuration as the sample BC 610 except that a thicker conductor pattern having a width of 300 μm and a height (thickness) of 20 μm is used. The inductor according to another embodiment of the present invention It is a sample as an example corresponding to a built-in substrate. As described above, samples BE610 and BE620 are examples corresponding to the inductor-embedded substrate according to the present invention.

  On the other hand, the sample CVTYW is a sample as a comparative example in which a raised portion is provided on the peripheral portion of the substrate, and a cavity surrounded by the raised portion is formed in the upper portion near the central portion of the substrate. Specifically, the sample CVTYW is embedded in a first coil embedded in a substrate made of ferrite as a magnetic material and a raised portion provided on a peripheral portion of the substrate made of ferrite as a magnetic material. A second coil. In the sample CVTYW, the first coil and the second coil have the same cross-sectional shape, so that the first coil and the second coil form one continuous spiral structure (see FIG. 8).

  More specifically, as shown in Table 1, the sample CVTYW has a width of 2.9 mm, a depth of 2.3 mm, and a height (thickness) due to the substrate and the raised portions provided on the peripheral edge of the substrate. It has an outer dimension of 1.0 mm. In addition, at the upper part in the vicinity of the center of the substrate, the width is 2.2 mm, the depth is 1.85 mm, and the height (depth) is 0, due to the upper surface of the substrate and the inner surface of the raised portion provided on the peripheral edge of the substrate. A cavity ridge having an inner dimension of .6 mm is formed (in FIG. 8, the cavity is not shown for the purpose of making the coil easy to see. For the appearance of the substrate and the ridge, see FIG. 9). reference). The size of the cavity is calculated as a volume necessary to accommodate circuit elements (for example, a capacitor and a switching IC) that constitute a DC-DC converter generally used in a portable terminal.

  As described above, in the sample CVTYW, the first coil in the substrate and the second coil in the raised portion are integrated to form a coil that exhibits one continuous spiral structure. This coil has a width of 100 μm and a height (thickness) of 30 μm for the short side portion, and a coil of 7.25 turns with a conductor pattern of a width of 275 μm and a height (thickness) of 30 μm for the long side portion. It is configured as. In the sample CVTYW, as shown in Table 1, among the layers including the conductor pattern, between the second and third layers from the bottom through the substrate and the raised portions, the four from the bottom One non-magnetic layer (that is, a total of three layers) is disposed between the first layer and the fifth layer, and between the sixth layer and the seventh layer from the bottom.

  Further, the sample CVTYN has a width of 50 μm and a height (thickness) of 30 μm for the short side portion, and a thin conductor pattern having a width of 225 μm and a height (thickness) of 30 μm for the long side portion. A sample as a comparative example having the same configuration as the sample CVTYW except that 25 coils are configured. As described above, the samples CVTYW and CVTYN are comparative examples corresponding to a configuration having a cavity formed by the substrate and the raised portion provided on the peripheral portion of the substrate.

  Next, in the sample DC410, in the samples LL310 and LL320, the coil embedded in the substrate is only the first coil (that is, single), whereas the sample DC410 is located inside the first coil embedded in the substrate. This is a comparative example in which another coil is further formed. In the sample DC 410, unlike the inductor built-in substrate according to the present invention, the raised portion is not disposed on the substrate. Specifically, the sample DC 410 includes a first coil embedded in a substrate made of ferrite as a magnetic material and a third coil embedded inside the first coil (see FIG. 10).

  More specifically, as shown in Table 1, the sample DC 410 has outer dimensions of a width of 2.9 mm, a depth of 2.3 mm, and a height (thickness) of 0.4 mm. In the ferrite substrate, a first coil and a third coil having a winding number of 4.25 are formed by a conductor pattern having a width of 386 μm and a height (thickness) of 10 μm. In Sample DC410, as shown in Table 1, among the layers including the conductor pattern, the third layer from the bottom and the third layer from the bottom in the substrate. Between the first layer and the fourth layer, one non-magnetic layer (that is, two layers in total) is disposed.

  Sample DC420 is a sample as a comparative example having the same configuration as sample DC410 except that a thicker conductor pattern having a width of 359 μm and a height (thickness) of 20 μm is used. As described above, the samples DC410 and DC420 are comparative examples corresponding to the configuration in which the protruding portion is not provided on the substrate and the coils embedded in the substrate are duplicated.

  Next, in the sample DB 610, in the samples DC410 and DC420, the ridge is not disposed on the substrate, whereas the ridge is disposed in the center on the substrate. It is an Example corresponding to the board | substrate with a built-in inductor which concerns on an embodiment. In the substrate of the sample DB 610, similarly to the samples DC410 and DC420, a coil corresponding to the third coil in the second aspect of the present invention is formed inside the first coil. Specifically, the sample DB 610 includes a first coil embedded in a substrate made of ferrite as a magnetic material, a third coil embedded inside the first coil, and a magnet disposed in the central portion on the substrate. A second coil embedded in a raised portion made of ferrite as a material is provided (see FIG. 11).

  More specifically, as shown in Table 1, the sample DB 610 has a width of 2.9 mm in width, a depth of 2.3 mm, and a height (thickness) of 0.4 mm in the center on the substrate. It has an appearance in which raised portions having outer dimensions of 1.3 mm, a depth of 2.3 mm, and a height (thickness) of 0.2 mm are disposed. In this ferrite substrate, a first coil and a third coil having a winding number of 4.25 are formed by a conductor pattern having a width of 323 μm and a height (thickness) of 10 μm. In addition, a second coil having a winding number of 2.25 is formed in the raised portion made of ferrite by a conductor pattern having a width of 323 μm and a height (thickness) of 10 μm. In the sample DB 610, as shown in Table 1, among the layers including the conductor pattern, between the first and second layers from the bottom in the substrate and the fourth layer from the bottom. 1 layer each between the first layer and the fifth layer, and one non-magnetic layer between the second layer and the third layer from the bottom in the ridge (that is, three layers in total) Has been.

  In addition, the sample DB 620 has the same configuration as the sample DB 610 except that a thicker conductor pattern having a width of 311 μm and a height (thickness) of 20 μm is used. The inductor according to another embodiment of the present invention It is a sample as an example corresponding to a built-in substrate. As described above, the samples DB610 and DB620 are examples corresponding to the inductor-embedded substrate according to the present invention.

  Measurement of characteristics of various inductor-embedded substrates having the above-described configuration will be described in detail below. In addition, as shown in Table 1, for all samples of various inductor-embedded substrates, the inductance measured for each sample was about 1 μH with the frequency fixed at 1 MHz by Agilent's LCR meter 4285A. Adjustment was made by a combination of the number of coil turns, the cross-sectional area, and the number of nonmagnetic layers.

2. Measurement of Characteristics of Various Inductor-Incorporated Substrates As shown in Table 1, DC resistance and superimposed current were measured for each of the various inductor-incorporated substrates having the above-described configuration. The measurement method for each measurement item will be described below.

(1) DC resistance As described above, in various circuits used in mobile terminals, it is important from the viewpoint of battery life to reduce the electrical resistance of circuit elements and the like and suppress the loss in the circuit. The “DC resistance” here was measured by a 4-terminal method by connecting a 4-terminal probe to a Keithley multimeter (2000 type).

(2) Superposed current As described above, with the recent increase in functionality, the circuits mounted on mobile terminals are becoming increasingly diverse. For example, the current flowing in a power supply circuit such as a DC-DC converter The value continues to increase. On the other hand, when the current flowing through the coil embedded in the magnetic material increases, the inductance of the coil decreases due to the aforementioned “direct current superposition characteristics”, for example, the efficiency of the DC-DC converter decreases. Or the function which smoothes the output voltage of power supply circuits, such as a DC-DC converter, falls. As a result, there is a high possibility that an excessive current flows to the output side, and for example, there is a high possibility that an additional circuit included in the mobile terminal will be broken. In order to reduce such a problem, an inductor in which a decrease in inductance due to an increase in current value is small is required.

  The inductance and the superimposed current were measured using an Agilent LCR meter 4285A with the frequency fixed at 1 MHz while superimposing the DC current. The superimposed current was obtained as a value when the inductance decreased by 30% from the state where no direct current was flowing.

  As described above, in the present specification, the bias current value at which the inductance is reduced by 30%, which is obtained from the inductance-DC current bias (L-Idc) characteristics, is measured by the DC current superposition inductance measurement. Measured as an index, referred to as “superimposed current”.

3. Characteristic Evaluation of Various Inductor-Incorporated Substrates The characteristics of various inductor-incorporated substrates measured as described above are listed in Table 1 as described above. In order to specify a substrate with a built-in inductor that has a low loss and does not deteriorate the smoothing function of the output voltage even if the current value increases, it can be said that it is desirable that the DC resistance is low and the superimposed current is large. Therefore, FIG. 12 shows a graph showing the relationship between the direct current resistance and the superimposed current in various inductor-embedded substrates listed in Table 1.

  As described above, in order to specify a substrate with a built-in inductor in which the loss is small and the smoothing function of the output voltage does not decrease even when the current value increases, it is desirable that the DC resistance is low and the superimposed current is large. That is, in the graph as shown in FIG. 12 in which the horizontal axis is the DC resistance and the vertical axis is the superimposed current, it can be said that the more the plot is in the upper left of the graph, the more preferable the substrate with built-in inductor.

  In the graph shown in FIG. 12, the various samples of the above-described comparative example are shown as white plots (however, the samples CVTYW and CVTYN of the comparative example having a cavity structure are plotted with x marks). The various samples are shown in black plots. More specifically, the samples LL310 and LL320 (only the substrate) of the comparative example described above are white circle marks, and SH410 and SH420 (only the raised portion and the number of windings of the coil are small) are white triangle marks, SH610. And SH620 (only the raised part and the number of windings of the coil) are white square marks, CVTYW and CVTYN (cavity) are marked with X, and DC410 and DC420 (only the double coil in the substrate) are white. Each of the samples BC610 and BC620 (substrate + raised portion at the center) according to the present invention is a black circle, and BE610 and BE620 (substrate + a raised portion at the end) are black triangles. The marks DB610 and DB620 (double coil in the substrate + protruding part in the center) are indicated by black rhombus marks, respectively.

  First, various samples other than the samples (DC410 and DC420, and DB610 and DB620) in which the double coil is embedded in the substrate are represented by white plots as apparent from the graph shown in FIG. Compared with the various samples of the comparative example, the various samples according to the present invention represented by the black plots achieve higher superimposed currents at lower DC resistance (DC resistance and superimposed current). And a good balance). Even when samples (DC410 and DC420, and DB610 and DB620) in which the double coil is embedded in the substrate are compared with each other, the sample is painted black compared with the sample of the comparative example represented by the white plot. The sample according to the present invention represented by this plot achieves a higher superimposed current at a lower DC resistance (the balance between the DC resistance and the superimposed current is better).

  Specifically, for the samples (LL310 and LL320) in which the coil is embedded only in the substrate and the samples (SH410 and SH420) in which the coil is embedded only in the raised portion, it is desirable that the DC resistance is low, but the superimposed currents are both present. It is as low as around 400 mA. In addition, with respect to the samples (SH610 and SH620) in which the coil having an increased number of turns is embedded only in the raised portion, the superimposed current is improved only to around 500 mA.

  Furthermore, for the samples (CVTYW and CVTYN) in which a ridge is provided on the peripheral edge of the substrate and a cavity surrounded by the ridge is formed near the center of the substrate (CVTYW and CVTYN), the direct current resistance is remarkably high and the superimposed current is remarkably high. The result was low. This is because, as described above, in order to provide the cavity, the conductive wire of the coil has to be made thin and long, so that the DC resistance value is increased and the magnetic material around the cavity has to be thinned. (Second) It is considered that this is because magnetic saturation due to the concentration of magnetic flux is likely to occur near the coil. As described above, in the various inductor-embedded substrates as comparative examples, desired characteristics could not be achieved.

  On the other hand, various samples according to the present invention (BC610 and BC620 () having a first coil embedded in a substrate including a magnetic material and a second coil embedded in a raised portion including a magnetic material. The ridges are arranged at the center), and BE610 and BE620 (the ridges are arranged at the ends), while maintaining almost the same DC resistance as the various samples of the comparative example except for the samples having cavities, around 600 mA. On the other hand, the comparative samples DC410 and DC420 (double coil only in the substrate, no ridge) embedded in the substrate were embedded in the substrate. Due to the effect of duplicating the coil formed, a high superimposed current of about 670 mA to about 770 mA was achieved, whereas it was embedded in the substrate. In the samples DB610 and DB620 according to the present invention, in which the second coil is further embedded in the raised portion in addition to the doubled coil, the samples DC410 and DC420 of the comparative example only in which the coil embedded in the substrate is only duplexed. A superposed current of about 800 to 900 mA, which is even higher than the above, was achieved, and the superposition characteristics of the second coil embedded in the raised portion were also found from a comparison between samples obtained by duplicating the coils embedded in these substrates. It is recognized that the effect on the improvement of is great.

  As is clear from the above results, in the inductor-embedded substrate according to the present invention, like the inductor that has been reduced in size and reduced in height in the prior art, an increase in loss due to an increase in the DC resistance of the coil, It is avoided that the direct current superimposition characteristic is deteriorated due to the downsizing and the low profile. As described above, a circuit element (for example, a capacitor) other than the inductor built in the inductor-embedded substrate according to the present invention is provided in the space on the substrate where the raised portion is not formed and / or the space above the raised portion. , Various ICs (integrated circuits), etc.), terminals, and the like can be provided, so that the entire circuit can be sufficiently reduced in size and height.

  Although several embodiments having specific configurations have been described above for the purpose of illustrating the present invention, the scope of the present invention is not limited to these exemplary embodiments, and It goes without saying that appropriate modifications can be made within the scope of the above and the matters described in the specification.

  DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Raised part, 21 ... Inductor, 22 ... Coil, 23 ... Magnetic flux produced by a coil, 31 ... Capacitor, and 41 ... Switching IC.

Claims (7)

A substrate mainly comprising a magnetic material,
A first coil made of a conductor embedded in the substrate;
A raised portion mainly including a magnetic material disposed on at least one surface of the substrate, and a second coil made of a conductor embedded in the raised portion,
Comprising
The cross-sectional area of the raised portion is smaller than the cross-sectional area of the substrate due to a plane parallel to the one surface of the substrate;
The cross-sectional area of the second coil is smaller than the cross-sectional area of the first coil due to a plane perpendicular to the central axis of the coil; and the second coil is electrically connected to the first coil;
A substrate with a built-in inductor. The inductor-embedded substrate according to claim 1,
A third coil made of a conductor embedded in the substrate, further comprising a third coil electrically connected to at least one of the first coil and the second coil; and A third coil is formed inside or outside the first coil;
A substrate with a built-in inductor. The inductor-embedded substrate according to claim 1 ,
The magnetic material constituting the substrate and / or the raised portion further includes at least one nonmagnetic layer mainly including a nonmagnetic material, and the nonmagnetic layer includes the first coil to the first coil. that is configured to intersect the central axis of one coil also least one of the second coil,
A substrate with a built-in inductor. The inductor-embedded substrate according to claim 2,
The magnetic material constituting the substrate and / or the raised portion further includes at least one nonmagnetic layer mainly including a nonmagnetic material; and
The nonmagnetic layer is configured to intersect a central axis of at least one of the first to third coils;
A substrate with a built-in inductor. An electric circuit comprising the inductor-embedded substrate according to any one of claims 1 to 4 . 6. The electric circuit according to claim 5 , wherein the electric circuit constitutes a power supply circuit. 7. The electric circuit according to claim 6 , wherein the power supply circuit constitutes a DC / DC converter.