JP5786647B2 - Multilayer substrate and DC-DC converter - Google Patents

Description

  The present invention relates to a multilayer substrate having a coil formed therein, and a DC-DC converter including the same.

  In power supply circuits of portable devices and the like, linear regulator type and switching regulator type ultra-small regulator modules are used. The linear regulator module converts all voltage fluctuation components into heat, so that the conversion efficiency of the power supply circuit is low. The switching regulator module generally has inferior noise characteristics compared to the linear regulator system due to switching noise and the like. Therefore, it has been proposed that a switching regulator type DC-DC converter that is small in size and has high voltage conversion efficiency and excellent noise characteristics can be used in a power supply circuit of a portable device or the like.

  In order to reduce the size of a DC-DC converter, a DC-DC converter may be configured on a multilayer substrate in which magnetic materials are laminated (see, for example, Patent Document 1). A conventional DC-DC converter module includes a magnetic substrate, a switching IC, and a capacitor component. An input / output terminal and a ground terminal are formed on the lower surface of the magnetic substrate, a switching IC and a capacitor component are mounted on the upper surface, and a coil is provided inside the substrate. And it becomes the structure by which switching IC etc. are connected to a coil.

Japanese Patent No. 4325747

  When a conventional DC-DC converter module is used as a step-up / step-down converter, the switching IC is connected to the front stage (input side) or the rear stage (output side) of the coil at the time of step-down and step-up and has a different structure. For this reason, the coil terminal that is highly affected by the switching noise generated from the switching IC is different between the step-down and step-up steps. Therefore, when the DC-DC converter is used as a step-up / step-down type, since it is necessary to take measures against noise on both terminals of the coil, the structure of the multilayer inductor of the conventional DC-DC converter module described in Patent Document 1 is used. It cannot be used as it is.

  Accordingly, an object of the present invention is to provide a multilayer substrate that can be used for any of a step-up type, a step-down type, or a step-up / down type converter by taking a noise countermeasure for the step-up / step-down operation, and a DC-DC-converter including the multilayer substrate. There is to do.

  In the present invention, a plurality of magnetic bodies are laminated, and a laminated body having a first surface and a second surface whose normal direction is a lamination direction, and a first terminal and a second terminal provided on the first surface of the laminated body. And a coil formed inside the laminated body with the laminating direction as a winding axis direction and having the first terminal and the second terminal as input / output terminals, the coil being an intermediate part of the laminated body A first coil formed by spirally connecting an annular electrode pattern formed on a plurality of magnetic bodies from a layer to the second surface, and a plurality of magnetic bodies from the first surface to the intermediate layer. A ring-shaped electrode pattern formed in a spiral connection, and a second coil formed in the same winding direction as the first coil, and an end of the first coil on the intermediate layer side The portion is electrically connected to the first terminal, and the end of the second coil on the intermediate layer side Electrically connected to the second terminal, the end portion of the second surface of the first coil, characterized in that conducting the end of the first surface of the second coil.

  In this configuration, since the input / output terminals of the coil are located in the intermediate layer of the multilayer body, the input / output terminals of the coil are separated from the first surface or the second surface of the multilayer body, and are the first coil and the second coil. It will be sandwiched. For this reason, for example, even when the ground electrode pattern is formed on the first surface or the second surface of the multilayer body, noise mixed from either of the two terminals of the coil is hardly transmitted to the ground electrode pattern. As a result, noise wraparound through the ground electrode pattern can be prevented. Further, the noise flowing in from any terminal of the coil has a small waveform amplitude while flowing through the first coil or the second coil from the intermediate layer of the laminate toward the outside (the first surface side or the second surface side). Become. For this reason, since the noise is small when approaching the first surface or the second surface, the propagation of noise to the ground electrode pattern can be suppressed. Furthermore, since the radiated noise can be blocked by the coil windings (electrode patterns) of different layers, the outflow of noise to the outside can be suppressed.

  In the multilayer substrate according to the present invention, it is preferable that a ground electrode layer is formed between the first surface or the second surface of the laminate and the coil.

  In this configuration, when a circuit element is mounted on the first surface or the second surface of the laminate, noise radiated from the circuit element to the coil side is shielded by the ground electrode layer formed between the coil and the coil. Can do.

  In the multilayer substrate according to the present invention, the stacked body has a nonmagnetic layer that sandwiches the plurality of magnetic bodies in the stacking direction as an outermost layer, and the ground electrode layer includes the stacked magnetic body and the nonmagnetic layer. The structure formed in the interface of a magnetic body layer may be sufficient.

  In this configuration, by providing the ground electrode layer as the outermost layer, the ground electrode layer is interposed between the coil formed on the magnetic body and the first surface or the second surface of the multilayer body. Thereby, the noise radiated from the coil is blocked by the ground electrode layer, and the noise can be prevented from being transmitted to the circuit element mounted on the first surface or the second surface of the multilayer body.

  According to the present invention, even if noise flows from any terminal of the coil, the noise can be reduced. For this reason, even if the multilayer substrate is used for any of the step-up type, step-down type or step-up / down type converter, the influence of noise can be suppressed.

1 is a schematic cross-sectional view of a DC-DC converter according to Embodiment 1. FIG. FIG. 4 is a schematic cross-sectional view of another example of the DC-DC converter according to the first embodiment. FIG. 3 is an equivalent circuit diagram of the DC-DC converter according to the first embodiment. The figure which shows the equivalent circuit in case a DC-DC converter carries out step-down operation. The figure which shows the equivalent circuit in case a DC-DC converter carries out pressure | voltage rise operation. FIG. 4 is a schematic cross-sectional view of a DC-DC converter according to a second embodiment.

(Embodiment 1)
The DC-DC converter according to the present invention will be described below. The DC-DC converter described below will be described as a step-up / step-down DC-DC converter module including a multilayer substrate according to the present invention with a built-in coil, and a switching IC and a capacitor mounted on the multilayer substrate.

  FIG. 1 is a schematic cross-sectional view of a DC-DC converter according to the first embodiment. The DC-DC converter 1 includes a multilayer substrate 10. The multilayer substrate 10 has a laminate 11 in which a plurality of magnetic layers are laminated. Each magnetic body layer of the multilayer body 11 is a sheet made of, for example, high permeability ferrite (Ni—Zn—Cu ferrite, Ni—Zn ferrite, or the like). In this laminate 11, a surface on which circuit elements are mounted is a front surface (first surface), and a surface mounted on a circuit board (not shown) is a back surface (second surface). Examples of circuit elements mounted on the surface of the multilayer body 11 include a switching IC 2 and capacitors Cin and Cout.

  The multilayer body 11 has a plurality of component mounting electrodes (first terminal and second terminal) 11A, 11B and the like formed on the surface. A circuit element such as a switching IC 2 is mounted on the component mounting electrodes 11A and 11B. In the multilayer body 11, an input terminal electrode Vin, an output terminal electrode Vout, and a ground terminal electrode Gnd as external connection terminals are formed on the back surface. Each electrode formed on the front and back surfaces of the laminate 11 is made of, for example, Ag. The input terminal electrode Vin and the output terminal electrode Vout formed on the back surface of the multilayer body 11 are connected to the component mounting electrode formed on the front surface by a wiring portion formed on the multilayer body 11 (not shown).

  In the following description, the normal direction of the front and back surfaces of the stacked body 11 is defined as the stacking direction, the surface direction of the stacked body 11 in the stacking direction is defined as the upper side, and the back surface direction is defined as the lower side.

  A coil L having the stacking direction as the winding axis direction is formed on the stacked body 11. The coil L is formed such that the annular electrode pattern formed on the ferrite sheet of the multilayer body 11 is electrically connected to the electrode patterns of different layers through via electrodes penetrating the ferrite sheet. The electrode pattern formed on the ferrite sheet is made of, for example, Ag. The coil L is formed so that the input / output terminals Lt1 and Lt2 are located in a substantially central layer (intermediate layer) of the multilayer body 11. Here, the input / output terminals Lt1 and Lt2 refer to a winding start end and a winding end end of the coil L.

  Hereinafter, the coil L will be described in detail. The coil L includes a first coil L1 formed in a region below the substantially central layer in the stacking direction of the stacked body 11, and a second coil L2 formed in a region above the approximately central layer in the stacking direction of the stacked body 11. It consists of and. The first coil L1 and the second coil L2 are wound in the same direction.

  Via electrodes L11 and L21 along the stacking direction are formed in each magnetic layer of the stacked body 11 from the surface to the substantially central layer. The via electrodes L11 and L21 are electrically connected to the component mounting electrodes 11A and 11B formed on the surface of the multilayer body 11. An end portion of the via electrode L11 extending downward from the surface of the multilayer body 11 is an input / output terminal Lt1, and an end portion of the via electrode L12 is an input / output terminal Lt2. The coil winding formed by being spirally wound downward from the input / output terminal Lt1 is the first coil L1. The coil winding formed by spirally winding upward from the input / output terminal Lt2 is the second coil L2. The winding end of the first coil L1 and the winding end of the second coil L2 are connected by a via electrode L31 formed along the stacking direction. Thereby, the coil L in which the input / output terminals Lt1 and Lt2 are located in the substantially central layer of the multilayer body 11 can be formed. The first coil L1 and the second coil L2 each have approximately half the number of windings of the total number of turns of the coil L.

  The switching IC 2 includes an input terminal, an output terminal (not shown), and a ground terminal GND, switches a voltage input from the input terminal, and outputs the voltage from the output terminal. The input terminal of the switching IC 2 is electrically connected to the input terminal electrode Vin formed on the back surface of the multilayer body 11 via the component mounting electrode, and the output terminal is electrically connected to the output terminal electrode Vout formed on the back surface of the multilayer body 11. doing. The ground terminal GND is electrically connected to the ground terminal electrode Gnd formed on the back surface of the multilayer body 11 within the multilayer body 11.

  The switching IC 2 includes coil connection terminals Lio1 and Lio2. The coil connection terminal Lio1 is electrically connected to the connection via electrode L11 via the component mounting electrode 11A. The coil connection terminal Lio2 is electrically connected to the connection via electrode L21 via the component mounting electrode 11B.

  The capacitor Cin is connected to the input terminal electrode Vin and the ground terminal electrode Gnd formed on the back surface of the multilayer body 11 via the component mounting electrodes. The capacitor Cin removes a noise component of the voltage input from the input terminal electrode Vin. The capacitor Cout is connected to the output terminal electrode Vout and the ground terminal electrode Gnd formed on the back surface of the multilayer body 11. The capacitor Cout smoothes the voltage output from the output terminal of the switching IC 2.

  FIG. 2 is a schematic cross-sectional view of another example of the DC-DC converter according to the first embodiment. The difference from the drawing shown in FIG. 1 is that the laminate 11 has a structure in which a plurality of magnetic layers are laminated and both sides thereof are sandwiched by nonmagnetic layers 12, and the laminate. 11, a ground electrode pattern (ground electrode layer) G is formed on the boundary surface between the magnetic layer and the nonmagnetic layer 12. Each magnetic body layer of the laminate 11 is a sheet made of, for example, high magnetic permeability ferrite (Ni—Zn—Cu ferrite, Ni—Zn ferrite, or the like), and the nonmagnetic body layer 12 has a relative magnetic permeability of 1 to 1. It is a sheet composed of about 10 non-magnetic or low-permeability ferrite (for example, Zn-Cu ferrite). The ground electrode pattern G is formed on the boundary surface between the magnetic body 11 and the nonmagnetic body layer 12 of the stacked multilayer body 11.

  As in FIG. 1, a coil L having a stacking direction as a winding axis direction is formed in the stacked body 11. The coil L is formed in a layer below the ground electrode pattern G. That is, the ground electrode pattern G is interposed between the circuit element such as the switching IC 2 mounted on the surface of the multilayer body 11 and the coil L. The ground electrode pattern G prevents noise radiated from the coil from being transmitted to the circuit element. In addition, by forming the ground electrode pattern G on the boundary surface between the magnetic layer and the nonmagnetic layer, it is possible to prevent the magnetic layer and the nonmagnetic layer from eroding each other when the laminate is fired. The ground terminal GND is electrically connected to the ground electrode pattern G, and is electrically connected to the ground terminal electrode Gnd inside the multilayer body 11.

  FIG. 3 is an equivalent circuit diagram of the DC-DC converter according to the present embodiment.

  A capacitor Cin and an input terminal IN of the switching IC 2 are connected to the input terminal electrode Vin of the DC-DC converter 1. A capacitor Cout and an output terminal OUT of the switching IC 2 are connected to the output terminal electrode Vout. Further, as described in FIG. 1, the capacitors Cin and Cout and the switching IC 2 are connected to the ground electrode pattern G, that is, the ground line.

  The switching IC 2 includes p-type MOS-FETs 21 and 23 and n-type MOS-FETs 22 and 24, and a driver 25 that performs switching control of the FETs 21 to 24. The FET 21 has a source connected to the input terminal IN, a drain connected to the coil connection terminal Lio1, and a gate connected to the driver 25. The FET 22 has a source connected to the ground line, a drain connected to the coil connection terminal Lio1, and a gate connected to the driver 25. The FET 23 has a drain connected to the coil connection terminal Lio2, a source connected to the output terminal OUT, and a gate connected to the driver 25. The FET 24 has a source connected to the ground line, a drain connected to the coil connection terminal Lio2, and a gate connected to the driver 25.

  The coil L is connected to the coil connection terminals Lio1 and Lio2 of the switching IC2. Specifically, the coil connection terminal Lio1 is connected to the input / output terminal Lt1 of the coil L via the via electrode L11. The coil connection terminal Lio2 is connected to the input / output terminal Lt2 of the coil L via the via electrode L21.

  Hereinafter, the step-up / step-down operation of the DC-DC converter 1 according to the present embodiment will be described.

  FIG. 4 is a diagram showing an equivalent circuit when the DC-DC converter 1 performs a step-down operation. In FIG. 4, the FET 23 and the FET 24 are represented by simple switch elements.

  When making the voltage of the output terminal electrode Vout higher than the voltage of the input terminal electrode Vin, the driver 25 always turns on the FET 23 and always turns off the FET 24. The driver 25 turns on the FET 21 and turns off the FET 22 to cause a current to flow through the coil L and excite it, thereby accumulating energy. Thereafter, the driver 25 turns off the FET 21 and turns on the FET 22 to commutate the energy accumulated in the coil L. By repeating this operation, the DC-DC converter 1 performs a step-down operation for outputting a voltage lower than the input voltage from the output terminal electrode Vout.

  FIG. 5 is a diagram showing an equivalent circuit when the DC-DC converter 1 performs a boost operation. In FIG. 5, the FET 21 and the FET 22 are represented by simple switch elements.

  When making the voltage of the output terminal electrode Vout lower than the voltage of the input terminal electrode Vin, the driver 25 always turns on the FET 21 and always turns off the FET 22. The driver 25 turns on the FET 24 and turns off the FET 24 to cause a current to flow through the coil L to excite it, and accumulates energy. Thereafter, the driver 25 turns off the FET 24 and turns on the FET 23 to release the energy accumulated in the coil L. At this time, the energy accumulated in the coil L is added to the input voltage as an induced voltage and smoothed by the capacitor Cout. Thus, the DC-DC converter 1 performs a boosting operation that outputs an output voltage higher than the input voltage.

  In the case of the step-down operation shown in FIG. 4, since the FET 21 and FET 22 are on / off controlled, the coil connection terminal Lio1 side has a larger switching noise than the coil connection terminal Lio2 side. On the other hand, in the step-up operation shown in FIG. 5, since the FET 23 and FET 24 are on / off controlled, the coil connection terminal Lio2 side has a larger switching noise than the coil connection terminal Lio1 side. Therefore, in order to suppress the influence of noise and to perform the step-up / step-down operation of the DC-DC converter 1, it is necessary to take measures against noise at both terminals of the coil connection terminals Lio1 and Lio2.

  In the DC-DC converter 1 according to the present embodiment, the input / output terminals Lt1 and Lt2 connected to the coil connection terminals Lio1 and Lio2 are located in a substantially central layer of the multilayer body 11 and are formed near the surface of the multilayer body 11. Away from the ground electrode pattern G formed. Thereby, the input / output terminal Lt1 or the input / output terminal Lt2 having a large switching noise can be coupled to the ground electrode pattern G, and the transmission of the switching noise to the ground electrode pattern G can be suppressed.

  Further, the switching noise flowing from the coil connection terminals Lio1 and Lio2 to the input / output terminals Lt1 and Lt2 has a reduced waveform amplitude by flowing through the first coil L1 or the second coil. Accordingly, the switching noise that flows in the portion of the coil L that is closest to the ground electrode pattern G is smaller than that of the input / output terminals Lt1 and Lt2 because it is after flowing through the first coil L1 or the second coil. As a result, noise transmitted to the ground electrode pattern G can be reduced.

  Further, the coil L has a structure in which noise radiated from an electrode pattern of a certain layer is shielded by an electrode pattern of a different layer. For this reason, even when noise is mixed from the input / output terminals Lt1 and Lt2, the noise reaching the surface of the multilayer body 11 is reduced. As a result, noise transmitted to the ground electrode pattern G can be reduced.

  As described above, by reducing the noise transmitted to the ground electrode pattern G, it is possible to suppress noise flowing out of the DC-DC converter 1 via the ground electrode pattern G. Further, since the ground electrode pattern G is formed in a layer near the surface of the multilayer body 11, the distance between the circuit element such as the switching IC 2 and the ground electrode pattern G can be shortened. As a result, noise generated by the circuit element is reduced. It can be suppressed by the ground electrode pattern G.

(Embodiment 2)
The present embodiment is different from the first embodiment in that circuit elements such as a switching IC and a capacitor provided in the DC-DC converter are not mounted on the multilayer substrate.

  FIG. 6 is a schematic cross-sectional view of a DC-DC converter according to the second embodiment. The DC-DC converter 5 according to this embodiment includes a multilayer substrate 6. The multilayer substrate 6 includes a laminate 7 in which a plurality of magnetic layers are laminated, and a coil L is formed inside the laminate 7. An input terminal electrode Vin and an output terminal electrode Vout are formed on the back surface of the multilayer body 7. The input terminal electrode Vin and the output terminal electrode Vout are mounted on the circuit board 30. Circuit elements 40 such as switching ICs and capacitors are mounted on the circuit board 30. That is, in the case of this embodiment, the circuit element 40 is not mounted on the surface of the multilayer substrate 6, and the DC-DC converter 5 is not a module in which the multilayer substrate 6 and the circuit element 40 are integrally formed.

  The circuit elements 40 are connected in the same manner as in the first embodiment by the wiring portions 31 formed on the circuit board 30. In addition, a ground electrode pattern G is formed on the circuit board 30 so that noise from the wiring portion 31 is shielded by the ground electrode pattern G and is not radiated from the circuit board 30 to the outside.

  The coil L formed in the laminated body 7 is composed of the first coil L1 and the second coil L2 as in the first embodiment, and the coil 7 starts to be wound on the substantially central layer in the laminating direction of the laminated body 7. An end and a winding end are formed so as to be positioned.

  Even in the DC-DC converter 5 according to the second embodiment formed as described above, the noise transmitted from the coil L to the ground electrode pattern G can be reduced to reduce the ground electrode pattern G as in the first embodiment. Thus, noise flowing out of the DC-DC converter 5 can be suppressed. Further, since the circuit element 40 such as a switching IC is not mounted on the surface of the multilayer body 7, the influence of the noise of the circuit element 40 on the coil L of the multilayer body 7 is slight.

  The specific configuration of the DC-DC converter can be appropriately changed in design, and the actions and effects described in the above-described embodiment are merely a list of the most preferable actions and effects resulting from the present invention. The operations and effects of the present invention are not limited to those described in the above embodiment.

  The multilayer substrate according to the present invention may be used in addition to a step-up / step-down type DC-DC converter, for example, a step-up or step-down DC-DC converter. Further, the multilayer substrate may be used for an element other than the DC-DC converter, or may simply be used as a coil element.

1-DC-DC converter 2-switching IC
10-multilayer substrate 11-laminated bodies 11A, 11B-component mounting electrodes (first terminal, second terminal)
21,23-p-type MOS-FET
22,24-n-type MOS-FET
L-coil L1-first coil L2-second coil G-ground electrode pattern Cin, Cout-capacitor

Claims (4)

A multilayer body in which a plurality of magnetic bodies are stacked and has a first surface and a second surface with the stacking direction as a normal direction;
A first terminal and a second terminal provided on the first surface of the laminate;
A coil formed inside the laminated body with the laminating direction as a winding axis direction, and the first terminal and the second terminal as input / output terminals;
With
The coil is
An annular electrode pattern formed on a plurality of magnetic bodies from the intermediate layer of the laminate to the second surface is formed in a spiral connection, with the end on the intermediate layer side as one end and the second surface side A first coil having the other end as the other end ;
Said annular electrode patterns formed on a plurality of magnetic bodies from the first surface to the intermediate layer is connected to a spiral, and the first coil and the winding direction is formed in the same, the intermediate layer side A second coil having one end as one end and the other end on the first surface side ;
Have
The end on the intermediate layer side which is one end of the first coil is electrically connected to the first terminal,
An end portion on the intermediate layer side which is one end of the second coil is electrically connected to the second terminal,
An end of the second surface that is the other end of the first coil is electrically connected to an end of the first surface that is the other end of the second coil.
Multilayer board.   The multilayer substrate according to claim 1, wherein a ground electrode layer is formed between the first surface or the second surface of the multilayer body and the coil. The laminate is
The outermost layer has a nonmagnetic layer that sandwiches the plurality of magnetic bodies in the stacking direction,
The ground electrode layer is
Formed on the boundary surface of the laminated magnetic body and non-magnetic layer,
The multilayer substrate according to claim 2. A multilayer body in which a plurality of magnetic bodies are stacked and has a first surface and a second surface with the stacking direction as a normal direction;
A first terminal and a second terminal provided on the first surface of the laminate;
A coil formed inside the laminated body with the laminating direction as a winding axis direction, and the first terminal and the second terminal as input / output terminals;
A switching IC and a capacitor provided on the first surface of the laminate and connected to the coil via the first terminal or the second terminal;
With
The coil is
An annular electrode pattern formed on a plurality of magnetic bodies from the intermediate layer of the laminate to the second surface is formed in a spiral connection, with the end on the intermediate layer side as one end and the second surface side A first coil having the other end as the other end ;
Said annular electrode patterns formed on a plurality of magnetic bodies from the first surface to the intermediate layer is connected to a spiral, and the first coil and the winding direction is formed in the same, the intermediate layer side A second coil having one end as one end and the other end on the first surface side ;
Have
The end on the intermediate layer side which is one end of the first coil is electrically connected to the first terminal,
An end portion on the intermediate layer side which is one end of the second coil is electrically connected to the second terminal,
An end of the second surface that is the other end of the first coil is electrically connected to an end of the first surface that is the other end of the second coil.
DC-DC converter.

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