JP2008135430A - High-frequency module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein a high-frequency module cannot be miniaturized when mounting an inductor having a large inductance value. <P>SOLUTION: On one surface of a substrate 2, a high-frequency circuit including a chip inductor 3a is composed, and a metallic shield cover 4 is attached to the substrate 2 while the high-frequency circuit is covered. A choke coil 7, which has an inductance value larger than that of the chip inductor 3a, is formed at a ceiling surface section 4a of at least the shield cover 4, and a connection terminal 8a provided at both the ends of the choke coil 7 is connected to the substrate 2, thus dispensing with space for mounting the choke coil 7 requiring a large inductance value on the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high frequency module on which a large inductor is mounted.

  Hereinafter, a conventional high-frequency module will be described. In a conventional high-frequency module, a plurality of electronic components are mounted on one surface of a substrate to form a circuit. This circuit includes a high frequency circuit for processing a high frequency signal. A metal shield cover is attached to the substrate to cover the entire circuit.

  The electronic component includes an inductor having a large inductance value, and this inductor is also mounted on the substrate. In such a high-frequency module, an inductor having a large inductance value such as 4.7 microhenry is used as the inductor.

As prior art document information related to the invention of this application, for example, Patent Documents 1 and 2 are known.
JP 2001-36341 A JP 2003-347129 A

  However, for example, an inductor having a large inductance value such as 4.7 microhenry has a problem that the size is large and the high-frequency module is enlarged.

  SUMMARY OF THE INVENTION The present invention solves this problem and aims to provide a small high-frequency module.

  In order to achieve this object, a high-frequency module according to the present invention is provided on a substrate, a high-frequency circuit configured on one surface of the substrate, a metal shield cover that covers the high-frequency circuit, and the high-frequency circuit. A first inductor; and a second inductor having an inductance value larger than that of the first inductor, wherein the second inductor is formed at least on a top surface of the shield cover, and the second inductor The connection terminals provided at both ends of the are connected to the substrate. This achieves the intended purpose.

  As described above, according to the present invention, the substrate, the high-frequency circuit configured on one surface of the substrate, the metal shield cover that covers the high-frequency circuit, and the first inductor provided in the high-frequency circuit And a second inductor having an inductance value larger than the inductance value of the first inductor, the second inductor being formed at least on the top surface of the shield cover and provided at both ends of the second inductor. A high-frequency module for connecting the connected terminal to the substrate.

  As a result, an inductor that requires a large inductance value is provided on the shield cover, so that a space for mounting the second inductor on the substrate can be eliminated. Therefore, there is an effect that the high-frequency module can be reduced in size.

(Embodiment 1)
Hereinafter, the present embodiment will be described with reference to the drawings. 1A is a top view of the high-frequency module according to the present embodiment, FIG. 1B is a side view thereof, and FIG. 2 is a cross-sectional view thereof.

  1 to 2, a high-frequency module 1 is a tuner (used as an example of a high-frequency circuit) that receives digital terrestrial broadcasting, and is mainly mounted on a portable device such as a mobile phone.

  This tuner has a high-frequency circuit block and a demodulation circuit block, and these circuit blocks operate with different voltages. On the other hand, the battery voltage of the portable device is about 3.6V. The battery voltage is directly supplied to the power supply terminal of the high-frequency module 1. Therefore, the high frequency module 1 is provided with a power supply circuit for converting a single voltage supplied from the battery into a voltage suitable for each circuit block. In this power supply circuit, the input voltage is dropped from the input voltage of 3.6V to 2.8V and 1.2V and output.

  Here, the RF circuit block operates at 2.8V. Therefore, an LDO regulator is used for conversion from a voltage of 3.6V to a voltage of 2.8V. On the other hand, the demodulating circuit block is driven at a low voltage by the miniaturization of the process for the digital IC, and operates at a voltage of 1.2V. Therefore, a DC-DC converter that has good conversion efficiency and can reduce power consumption of the portable device is used for this conversion.

  Next, the configuration of the high frequency module 1 will be described. A plurality of electronic components 3 are mounted on the upper surface of the substrate 2 to constitute a tuner and a power supply circuit. The electronic component 3 includes a chip inductor 3a that is a relatively small inductor, a chip capacitor, or a semiconductor element. In order to shield at least the tuner, a metallic shield cover 4 is attached to the substrate 2 so as to cover the circuit between the tuner and the DC-DC converter. The shield cover 4 has a top surface portion 4a disposed above the electronic component 3, a vertical side surface portion 4b formed by bending downward from each of two opposing end portions of the top surface portion 4a, and the vertical side surface portion. 4b and a leg 4c extending downward from the tip of 4b. Further, the shield cover 4 has a lateral side surface portion 4d formed by bending from both side ends of the respective longitudinal side surface portions 4b, and leg portions extending downward also at the distal ends of the lateral side surface portions 4d. 4c is provided. In the present embodiment, the lateral side surface portion 4d is formed from both the vertical side surface portions 4b, but this may be formed from either one.

  Here, a notch 5 a is provided on the side surface of the substrate 2. And the leg part 4c of the vertical side part 4b and the horizontal side part 4d is inserted in the notch 5a, and the conductor electrode and the leg part 4c formed in the inner peripheral surface of this notch 5a are connected by the solder 6. FIG. With this configuration, the electronic component 3 is surrounded by the vertical side surface portion 4b and the horizontal side surface portion 4d, and the tuner is shielded.

  Next, the choke coil 7 (used as an example of an inductor) of the DC-DC converter will be described. Although the inductance value of the chip inductor 3a constituting the tuner is small, the choke coil 7 of the DC-DC converter generally needs a large inductance. Therefore, choke coil 7 in the present embodiment winds conductive wire 8 having a heat-resistant insulating coating around top surface portion 4a. At both ends of the conductive wire 8, connection terminals 8 a for connecting to the substrate 2 are formed. This connection terminal 8 a is a region where the insulation coating has been peeled off, and this connection terminal 8 a is inserted into a notch 5 b provided on the side surface of the substrate 2 and connected by solder 6. Since the choke coil 7 is connected on the side surface of the substrate 2 in this way, it is easy to determine whether or not the connection is good. Moreover, since it is not necessary to insert in a hole, productivity can also be made favorable.

  Thus, since the choke coil 7 is formed by being wound around the top surface portion 4a of the shield cover 4 having a large area, a large inductance value can be obtained. In addition, although the white was used for the shield cover 4 in this Embodiment, you may use another material for this. However, the material of the shield cover needs to be capable of shielding high frequency signals and forming a large inductance. Therefore, if a material having a high magnetic permeability such as permalloy (Fe—Ni alloy) or silicon steel plate (Fe—Si alloy) is used instead of the white and white, an inductor having a larger inductance value can be formed. In particular, when a non-ferrous amorphous alloy such as Co—Fe—Mn—Cr—Si—B is used, eddy currents generated by a signal flowing through the inductor can be suppressed, so that signal loss can be reduced. That is, when this inductor is used as the choke coil 7 of the DC-DC converter, a high-efficiency DC-DC converter can be realized, so that the high-frequency module 1 with low power consumption can be realized. If this inductor is used as a filter, a filter with a small signal loss can be obtained.

  With the above configuration, the choke coil 7 is formed on the shield cover 4, so there is no need to dispose the choke coil 7 on the substrate 2. Therefore, the area of the high frequency module 1 can be reduced. Furthermore, since the conducting wire 8 is wound around the top surface portion 4a, the height dimension of the choke coil 7 can be reduced. Therefore, the thin high frequency module 1 can be realized.

  In the present embodiment, the vicinity of the center on the front side of the shield cover 4 is a non-installed portion 9 of the conducting wire 8. That is, when the conducting wire 8 is wound around the top surface portion 4 a, the conducting wire 8 passes through the inside of the shield cover 4 in the region of the non-installed portion 9. As a result, the flat top surface portion 4a is exposed at the central portion of the shield cover 4. Therefore, when the high frequency module 1 is mounted on the mother board, it is possible to mount the high-frequency module 1 by sucking the non-installed portion 9. Thus, since the flat top surface part 4a can be adsorbed, it can be easily mounted with a general-purpose mounting apparatus.

  Further, since the shield cover 4 is formed by press working, burrs are generated at the cut portions. Therefore, a resin insulating sheet is attached to the cut portion 10 in the top surface portion 4a. Thereby, since the insulating sheet is sandwiched between the conductor 8 and the top surface portion 4a, it is difficult for the shield cover 4 and the conductor 8 to be short-circuited by burrs when the shield cover 4 is processed.

  Next, the manufacturing method of the high frequency module 1 is demonstrated. First, the electronic component 3 is mounted on the substrate 2 and connected by soldering or the like. On the other hand, the shield cover 4 is pressed. However, at this time, the vertical side surface portion 4b is not bent. The shield cover 4 is attached to a coil winding facility, and the conductive wire 8 is wound around the top surface portion 4a. Then, when the conducting wire 8 is wound to the vicinity of the center, the non-installed portion 9 of the conducting wire 8 is formed on the surface of the shield cover 4 through the inner surface of the shield cover 4. In addition, the conducting wire 8 is cut | disconnected when the insulation coating is stripped in advance at a predetermined interval and the conductive wire 8 is wound a predetermined number of times. After that, both the vertical side surface parts 4b are bent, and the shield cover 4 in which the choke coil 7 is formed is completed. Thus, by bending the vertical side surface portion 4b later, the conductive wire 8 can be easily wound around the top surface portion 4a.

  The shield cover 4 processed in this way is attached to the substrate 2. At this time, the leg 4c is inserted into the notch 5a of the substrate 2, while the connection terminal 8a is inserted into the notch 5b.

  Thereafter, the leg portion 4c and the notch 5a, and the connection terminal 8a and the notch 5b are respectively connected by the solder 6, and the high frequency module 1 is completed.

  Although the choke coil 7 is provided on the shield cover 4 in the present embodiment, this may be another coil. For example, when a tuner circuit for receiving AM broadcast waves is configured on the substrate 2, the inductance value of the inductor used for the input filter circuit is large because the signal frequency is low. Accordingly, since a large coil is required, such an inductor may be formed on the shield cover 4.

  Furthermore, in the present embodiment, one inductor is formed on the shield cover 4, but a plurality of inductors may be formed. However, even in this case, it is necessary not to wind the conducting wire 8 around the non-installed portion 9.

(Embodiment 2)
Hereinafter, the high frequency module 21 in the present embodiment will be described with reference to the drawings. FIG. 3A is a top view of the high-frequency module in the present embodiment, FIG. 3B is a side view thereof, and FIG. 4 is a side view of the shield cover. 3 to 4, the same reference numerals are used for the same components as those in FIGS. 1 and 2, and the description thereof is simplified.

  The high frequency module 21 in FIGS. 3 and 4 includes a shield cover 22 and a shield cover 23, and the conductive wire 8 is wound around the top surface portion 23 a of the shield cover 23. The vertical side surface portion 23b is bent from both ends of the top surface portion 23a, and a leg portion 23c is provided at the tip of the vertical side surface portion 23b.

  On the other hand, the shield cover 22 has a top surface portion 22a, a side surface portion 22b bent from four ends of the top surface portion 22a, and a leg portion 22c extending from the tip of the side surface portion 22b. Here, a notch 5a is provided on the side surface of the substrate 2, and the leg portion 22c is inserted. Further, the side surface of the substrate 2 has a notch 5c, and a leg portion 22c and a leg portion 23c are inserted into the notch 5c. And both the leg part 22c and the leg part 23c are fixed to the notch 5c with the solder 6. FIG. Thus, since the leg part 22c and the leg part 23c can be simultaneously connected to the solder 6, the high-frequency module 21 with good productivity can be obtained.

  Here, a hole 24 corresponding to the top surface portion 23 a of the shield cover 23 is provided in the top surface portion 22 a of the shield cover 22. In the present embodiment, the height of the shield cover 22 and the height of the shield cover 23 are the same. With the above configuration, the conducting wire 8 is wound around the top surface portion 23a of the shield cover 23. Therefore, the conducting wire 8 can be easily wound even when the vertical side surface portion 22b is bent. Therefore, a high frequency module with good productivity can be obtained. Further, since the hole 24 is blocked by the top surface portion 23a, the high frequency circuit can be shielded.

  In the present embodiment, the heights of the top surface portion 22a and the top surface portion 23a are the same, but the height of the inner peripheral surface of the top surface portion 22a may be made higher than the height of the upper end of the conducting wire 8. In this way, the top surface portion 23a can be made larger than the hole 24, and the gap between the top surface portion 23a and the hole 24 can be reduced. Therefore, the shielding property is further improved.

  Or conversely, the surface of the top surface portion 22a and the height of the upper end of the conductor 8 may be the same height. In this way, tall parts can be arranged under the top surface portion 22a.

  Even in this case, it is necessary to provide the non-installed portion 9 at the center of the shield cover 23.

  With the above configuration, in the high-frequency module 21 according to the present embodiment, the choke coil 7 is formed on the shield cover 23, so that a space for mounting the choke coil 7 on the substrate 2 becomes unnecessary. Therefore, a small high-frequency module 21 can be realized.

(Embodiment 3)
Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 5 is a cross-sectional view of the high-frequency module 31 according to the present embodiment, and FIG. 6 is an enlarged view of a main part viewed from the back side. In FIGS. 5 and 6, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is simplified.

  In the high frequency module 31 in the present embodiment, the choke coil is formed on the inner surface of the shield cover 32. For this purpose, a foldable coil substrate 33 is attached to the inner surface of the shield cover 32 and is bent together with the shield cover 32. The coil substrate 33 has an insulating film bonded to both sides of a flexible substrate. Coil conductors are formed on both sides of the flexible substrate, and inductors are formed by connecting the coil conductors with through holes. Has been. By doing so, the inductor can be formed using the entire area of the inner surface of the shield cover 32, so that an inductor having a large inductance value can be configured.

  Here, the shield cover 32 has a top surface portion 32a, a side surface portion 32b formed by bending from the four end portions of the top surface portion 32a, and a leg portion 32c provided extending from the tip of the side surface portion 32b. And a leg portion 32d. Here, the leg portion 32 c is used to connect the inductor formed on the coil substrate 33 to the circuit on the substrate 2, and the leg portion 32 d is used to connect the shield cover 32 to the ground of the substrate 2.

  First, in the leg portion 32d, the coil substrate 33 is not bonded, and the leg portion 32d is exposed. The leg portion 32d is inserted into a notch 5a provided on the side surface of the substrate, and is connected to a conductor electrode provided on the inner periphery of the notch 5a by a solder 6.

  On the other hand, the leg 32c is provided with an inductor connection terminal 33a formed on the coil substrate 33. For this purpose, the innermost insulating film is not provided on the coil substrate 33 in the leg portion 32c, and the connection terminal 33a is formed on the inner surface of the flexible substrate. Thereby, the connection terminal 33a is exposed in the leg part 32c. Therefore, the leg 32c is inserted into the notch 5b, and the connection terminal 33a and the conductor electrode provided on the inner periphery of the notch 5b are connected by the solder 6.

  Note that the width of the connection terminal 33a is narrower than the width of the leg portion 32c. Further, the width of the conductor electrode of the notch 5b is made substantially equal to the width of the connection terminal 33a. This makes it difficult for the solder 6 to be short-circuited between the connection terminal 33a and the leg portion 32c or between the leg portion 32c and the conductor electrode.

  With the above configuration, a space for placing the inductor on the substrate 2 is not necessary, and thus a small high-frequency module 31 can be realized. Further, since the inductor is formed on a thin film flexible substrate, the thickness of the inductor can be reduced. Therefore, a thin high-frequency module 31 can be realized.

  Further, since there is no need to wind a conducting wire or the like, the productivity is good. Furthermore, since the connection terminal 33a is formed on the leg portion 32c, the connection terminal 33a can be inserted into the notch 5b simultaneously with the mounting of the shield cover 32, so that the high-frequency module 31 with good productivity can be realized.

  In addition, since the inductor and the electronic component 3 are insulated by an insulating film, the gap between the electronic component 3 and the top surface portion 32a can be reduced. Accordingly, a thinner high-frequency module 31 can be realized.

(Embodiment 4)
Hereinafter, the high frequency module 41 in this Embodiment is demonstrated using drawing. FIG. 7 is a cross-sectional view of the high-frequency module according to the present embodiment, FIG. 8A is a top view of a ground terminal used in the high-frequency module, and FIG. 8B is a side view thereof. 7 and 8, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is simplified.

  7 and 8, the ground terminal 43 is formed by extending the top surface portion 43a, a side surface 43b formed by bending the end portion of the top surface portion 43a in four directions, and extending from the tip of the side surface 43b. Leg portions 43c.

  On the other hand, the multilayer substrate 42 is a four-layer substrate, and is approximately the same size as the substrate 2. The uppermost layer (upward in FIG. 7) of the multilayer substrate 42 is a ground layer, and a ground pattern is formed on the entire surface. The two middle layers are layers on which inductors are formed. The lowermost layer is a layer in which a connection land 42a for connecting the ground terminal 43 is formed. The connection land 42a is formed at a position corresponding to the top surface portion 43a of the ground terminal 43, and the connection land 42a and the top surface portion 43a are connected by solder. Here, the connection land 42a is connected to the uppermost ground pattern by a through hole. Thus, a pseudo shield cover is configured by the ground layer of the multilayer substrate 42, the side surface 43b of the ground terminal 43, and the leg portion 43c. And this leg part 43c is inserted in the notch 5a of the board | substrate 2, and the leg part 43c and the notch 5a are connected with the solder 6. FIG.

  Next, the connection between the inductor formed on the multilayer substrate 42 and the substrate 2 will be described. A connection land 42 b connected to the inductor of the multilayer substrate 42 is provided in the lowermost layer of the multilayer substrate 42. The connection land 42b is positioned above the notch 5b, and the connection land 42b and the notch 5b are connected by a signal terminal 44. The signal terminal 44 is formed of a connection portion 44a connected to the connection land 42b by solder and a leg portion 44b formed by bending downward from the connection portion 44a. The leg portion 44 b is inserted into the notch 5 b and connected to the substrate 2 with the solder 6. By doing so, the connection land 42b and the notch 5b are connected, and the inductor of the multilayer board 42 and the circuit on the board 2 are connected.

  An electronic component 45 constituting a DC-DC converter is mounted on the lower surface side of the multilayer substrate 42. Thus, since the multilayer substrate 42 is used as a pseudo cover, the electronic component 45 can be mounted on the multilayer substrate 42. Therefore, a further compact high-frequency module 41 can be realized.

  By doing so, the inductor can be formed using the entire area of the multilayer substrate 42, and thus an inductor having a large inductance value can be configured. In the present embodiment, a glass / epoxy base material is used for the multilayer substrate 42, but other base materials may be used. In particular, if a base material in which ferrite powder is kneaded into the core base material of the inner layer is used, the magnetic permeability can be increased and a larger inductor can be formed.

  Next, the manufacturing method of the high frequency module 41 in this Embodiment is demonstrated. First, the electronic component 3 is mounted on the upper surface of the substrate 2. On the other hand, cream solder is applied to a predetermined position on the lowermost layer of the multilayer substrate 42, and then the electronic component 45 and the ground terminal 43 are mounted. Here, as shown in FIG. 8, the ground terminal 43 and the signal terminal 44 are connected by a connecting portion 46. Therefore, if the ground terminal 43 is mounted on the multilayer substrate 42, the signal terminal 44 can be mounted on the multilayer substrate 42 at the same time, so that the productivity is very good.

  Then, by heating the multilayer substrate 42, the cream solder is melted, and the ground terminal 43 and the signal terminal 44 are connected to the multilayer substrate 42. After that, the ground terminal 43 in a state where the multilayer substrate 42 is connected is mounted on the substrate 2 on which the electronic component 3 is mounted in advance. That is, the leg 43c of the ground terminal 43 and the leg 44b of the signal terminal 44 are inserted into the notch 5b and the notch 5a, respectively. Thereby, since the leg part 44b can be inserted simultaneously with the insertion of the leg part 43c, insertion work is easy and productivity is favorable.

  And after inserting the leg part 43c and the leg part 44b into a notch, the leg part 43c and the leg part 44b and each notch are soldered.

  In this state, the ground terminal 43 and the signal terminal 44 are connected. Therefore, after this soldering, the connecting portion 46 is cut off, and the ground terminal 43 and the signal terminal 44 are separated. For this purpose, the connecting portion 46 is provided with a V-groove. And if the connection part 46 is folded in this V groove 46a, the connection part 46 will be cut away. As a result, the ground terminal 43 and the signal terminal 44 are separated, and the high-frequency module 41 is completed.

  A ground pattern may also be formed on the lowermost layer of the multilayer substrate 42. In this case, since the ground is strengthened, the high-frequency circuit can be shielded more firmly. In addition, since the inductor of the multilayer substrate 42 is sandwiched between the grounds, the signal of the high-frequency circuit can hardly enter the inductor.

  The high-frequency module according to the present invention has an effect that the module can be reduced in size and thickness, and is useful when used for a high-frequency module in which a circuit requiring a large inductor such as a DC-DC converter is incorporated.

(A) Top view of the high frequency module in Embodiment 1 of this invention, (b) Same side view Same as above, sectional view (A) Top view of the high frequency module in Embodiment 2 of this invention, (b) Same side view Side view of shield cover Sectional drawing of the high frequency module in Embodiment 3 Same part, enlarged view from the back Sectional drawing of the high frequency module in Embodiment 4 (A) Same as above, top view of ground terminal, (b) Same as above, side view

Explanation of symbols

2 Substrate 3a Chip inductor 4 Shield cover 4a Top surface 7 Choke coil 8a Connection terminal

Claims (14)

A substrate, a high-frequency circuit formed on one surface of the substrate, a metal shield cover covering the high-frequency circuit, a first inductor provided in the high-frequency circuit, and an inductance value of the first inductor A second inductor having a larger inductance value, wherein the second inductor is formed at least on the top surface of the shield cover, and connection terminals provided at both ends of the second inductor are connected to the substrate. High frequency module. The high frequency module according to claim 1, wherein the second inductor is formed by winding a conductive wire around the top surface portion, and an insulating film is provided between the shield cover and the conductive wire. The high-frequency module according to claim 2, wherein the conductor is a conductive wire with an insulating film having an insulating film formed on the surface in advance. The high frequency module according to claim 2, wherein the shield cover is formed by press working, and an insulator is inserted between the cut end portion of the shield cover and the conductive wire. The high frequency module according to claim 2, wherein a central portion on the front side of the shield cover is a conductor-free portion. 2. The high-frequency module according to claim 1, wherein the side surface of the substrate has a notch and a conductor electrode formed on an inner periphery of the notch, and the connection terminal of the second inductor is connected to the conductor electrode. The shield cover surrounds the entire high-frequency circuit, and includes a first shield cover portion having a hole in the top surface portion thereof, and a second shield cover portion around which a conductive wire is wound, and the hole is the second shield portion. The high frequency module according to claim 2, wherein the second shield case is connected to at least one of the first shield case and the substrate. The first and second shield covers are provided with legs extending from the side surfaces of the first and second shield cases for fixing to the substrate, and the side surfaces of the substrate have a plurality of legs. Notches and conductor electrodes formed on the inner periphery of these notches are provided, the legs of the first and second shield covers are both inserted into the same notch, and the conductor electrodes and the legs are connected to each other. The high-frequency module according to claim 7. The high-frequency module according to claim 1, wherein the second inductor is formed on a foldable flexible substrate, and the flexible substrate is attached to a shield case and is bent together with the shield cover. The flexible substrate is affixed to the inside of the shield cover, and a connection terminal is formed on the inner surface of the leg extending from the side surface of the shield case, and the leg extends to the notch formed on the side surface of the substrate. The high-frequency module according to claim 9, wherein the connection terminal is connected to a conductor electrode formed on the inner periphery of the notch. The high-frequency module according to claim 10, wherein the width of the connection terminal is smaller than the width of the leg, and the width of the conductor electrode and the width of the connection terminal are substantially equal. A multilayer substrate having a ground layer in a layer different from the layer on which the second inductor and the second inductor are formed; and standing up along an outer periphery of the multilayer substrate; A metal ground terminal that connects between the ground and a signal terminal that connects between both ends of the second inductor and the substrate; and a pseudo shield case by the ground layer and the ground terminal The high frequency module according to claim 1, wherein: The high-frequency module according to claim 12, wherein an electronic component connected to the second inductor is mounted on the multilayer substrate. The high-frequency module according to claim 1, wherein a DC-DC converter connected to a high-frequency circuit is formed on the substrate, and the second inductor is a choke coil of the DC-DC converter.

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