Multilayer substrate provided with built-in mover

Abstract

This multilayer substrate (100) provided with a built-in mover comprises: a hollow part (12) provided to a base material (11) formed in multiple layers; a magnet (13) that is a mover accommodated inside the hollow part (12) and formed from a magnetic material; a drive coil (14) provided to the base material (11); strip lines (18, 19) provided to the base material (11); and a shield plate (16) provided to the base material. The thickness of the shield plate (16) is less than the penetration depth of a magnetic field at the frequency of the current flowing through the drive coil (14) in the shield plate (16) and is greater than the penetration depth of radiation at the frequency of a high-frequency signal flowing through the strip lines (18, 19) in the shield plate (16).

Description

Multilayer Substrate with Built-in Movable Element

[0001] The present disclosure relates to a multilayer substrate with a built-in movable element.

[0002] Conventionally, a multilayer substrate with a built-in movable element that houses a movable element in a hollow portion inside the substrate has been provided. Patent Document 1 discloses a technique for suppressing radiation of noise from electronic components using a shield layer.

[0003] International Publication No. 2018 / 159290

[0004] In the above multilayer substrate with a built-in movable element, it is conceivable to move the movable element using a magnetic field generated by energizing a coil. Also, in the above multilayer substrate with a built-in movable element, when using a high-frequency signal, the radiation of the high-frequency signal can be suppressed by providing the shield layer disclosed in Patent Document 1. However, when the shield layer is applied to the above multilayer substrate with a built-in movable element, there is a possibility that the magnetic field generated by energizing the coil may be blocked by the shield layer.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a multilayer substrate with a built-in movable element that can suppress radiation of a high-frequency signal to the outside while allowing a magnetic field generated by energizing a coil to act on the movable element.

[0006] The multilayer substrate with a built-in movable element according to the present disclosure includes a hollow portion provided in a base material formed in multiple layers, a movable element housed inside the hollow portion and formed of a magnetic material, a drive coil provided in the base material, a strip line provided in the base material, and a shield plate provided in the base material. The thickness of the shield plate is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the drive coil in the shield plate, and thicker than the penetration depth of the radiation at the frequency of the high-frequency signal flowing through the strip line in the shield plate.

[0007] According to the present disclosure, it is possible to suppress radiation of a high-frequency signal to the outside while allowing a magnetic field generated by energizing a coil to act on the movable element.

[0008] This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 1. These are transverse cross-sectional views of each layer in the multilayer substrate with a built-in movable element according to Embodiment 1. Figure 2A is a cross-sectional view taken along the line A-A in Figure 1. Figure 2B is a cross-sectional view taken along the line B-B in Figure 1. Figure 2C is a cross-sectional view taken along the line C-C in Figure 1. Figure 2D is a cross-sectional view taken along the line D-D in Figure 1. Figure 2E is a cross-sectional view taken along the line E-E in Figure 1. This is a diagram showing the operation of the multilayer substrate with a built-in movable element according to Embodiment 1. This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 2. This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 3. This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 4. This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 5. This is a cross-sectional view taken along the line F-F in Figure 7. This is a longitudinal cross-sectional view of a multilayer substrate with a built-in movable element according to Embodiment 6.

[0009] To provide a more detailed explanation of this disclosure, the forms for implementing this disclosure will be described below with reference to the attached drawings.

[0010] Embodiment 1. The movable element-embedded multilayer substrate 100 according to Embodiment 1 will be described with reference to Figures 1 to 3.

[0011] First, the configuration of the movable element-embedded multilayer substrate 100 according to Embodiment 1 will be described using Figures 1 and 2. Figure 1 is a longitudinal cross-sectional view of the movable element-embedded multilayer substrate 100 according to Embodiment 1. Figure 2 is a transverse cross-sectional view of each layer in the movable element-embedded multilayer substrate 100 according to Embodiment 1.

[0012] As shown in Figures 1 and 2, the movable element-embedded multilayer substrate 100 according to Embodiment 1 comprises a base material 11, a hollow portion 12, a magnet 13, a drive coil 14, a first ground 15, a shield plate 16, a via 17, a first strip line 18, a second strip line 19, and a second ground 20.

[0013] As shown in Figure 1, the base material 11 has a multilayer structure and a hollow structure. The base material 11 has an upper surface 11a and a lower surface 11b. That is, the upper surface 11a is located on one side or the upper side in the thickness direction of the base material 11 (hereinafter referred to as the base material thickness direction). The lower surface 11b is located on the other side or the lower side in the base material thickness direction. The upper surface 11a and the lower surface 11b are located at opposite positions to each other in the base material thickness direction. The base material 11 may have one surface as the front surface and the other surface as the back surface. The base material 11 is made of, for example, resin or ceramics.

[0014] The hollow portion 12 is provided inside the base material 11. The hollow portion 12 is positioned between the upper surface 11a and the lower surface 11b in the thickness direction of the base material. As shown in Figure 2D, the hollow portion 12 is square when viewed from the upper surface 11a side or the lower surface 11b side of the base material 11. The shape of the hollow portion 12 when viewed from the upper surface 11a side or the lower surface 11b side is not required as long as it is a shape that can accommodate the magnet 13, which will be described later. The hollow portion 12 may be a rectangle, triangle, or circle, for example, in addition to a square. Furthermore, the thickness of the hollow portion 12 is not required as long as it is thick enough for the magnet 13, which will be described later, to move or be movable in the thickness direction of the base material.

[0015] The magnet 13 is a movable element made of a magnetic material. As shown in Figures 1 and 2D, the magnet 13 is embedded in the base material 11 and housed inside the hollow portion 12. Because the magnet 13 is made of a magnetic material, it can move in the thickness direction of the base material inside the hollow portion 12 by an applied magnetic field. In the magnet 13 shown in Figure 1, the upper half of the magnetic pole is the south pole and the lower half of the magnetic pole is the north pole, but these magnetic poles may be positioned in the opposite direction.

[0016] The drive coil 14 generates a magnetic field in a loop shape in the thickness direction of the substrate when energized. The magnet 13 moves in the thickness direction of the substrate due to this magnetic field. As shown in Figure 1, the drive coil 14 is located inside the substrate 11, between the upper surface 11a of the substrate 11 and the hollow portion 12.

[0017] Furthermore, as shown in Figures 1, 2A, and 2B, the drive coil 14 has a first coil section 14a, a second coil section 14b, and a coil connecting via 14c. The first coil section 14a and the second coil section 14b are provided in separate layers. The coil connecting via 14c electrically connects the center end of the first coil section 14a and the center end of the second coil section 14b.

[0018] Specifically, the first coil section 14a is positioned above the second coil section 14b. The first coil section 14a is positioned on the upper surface 11a side of the second coil section 14b. The second coil section 14b is positioned on the hollow section 12 side of the first coil section 14a. The first coil section 14a and the second coil section 14b are positioned opposite each other in the substrate thickness direction. The winding direction of the first coil section 14a and the winding direction of the second coil section 14b are opposite to each other. The coil connection via 14c extends in the substrate thickness direction. One end of the coil connection via 14c is electrically connected to the center end of the first coil section 14a, and the other end of the coil connection via 14c is electrically connected to the center end of the second coil section 14b.

[0019] Therefore, when a voltage is applied to the outer ends of the first coil section 14a and the second coil section 14b of the drive coil 14, current flows through the first coil section 14a, the second coil section 14b, and the coil connecting via 14c. As a result, the drive coil 14 generates a loop-shaped magnetic field in the thickness direction of the substrate. Furthermore, the drive coil 14 can switch the direction of the magnetic field by reversing the direction of the current flowing through the first coil section 14a, the second coil section 14b, and the coil connecting via 14c.

[0020] As shown in Figure 1, the first ground 15 is positioned inside the base material 11 so as to surround the hollow portion 12. The first ground 15 is the ground for the drive coil 14. Note that the first ground 15 does not come into contact with the hollow portion 12.

[0021] The first shielding plate, 16, is a conductive plate and constitutes a cover member for the hollow portion 12. Specifically, as shown in Figures 1 and 2C, the shielding plate 16 is positioned inside the base material 11 to cover the entire upper opening surface (one-sided opening surface) of the hollow portion 12. The shape of the shielding plate 16 can be adjusted as appropriate, as long as it can cover the entire upper opening surface of the hollow portion 12. As will be described in detail later, the shielding plate 16 allows the magnetic field generated by energizing the drive coil 14 to pass through, but prevents the radiation or emission (hereinafter referred to as radiation) of high-frequency signals from passing through. The shielding plate 16, together with the first ground 15, functions as a ground for the drive coil 14.

[0022] Multiple vias 17 are provided inside the substrate 11 so as to surround the hollow portion 12. The vias 17 extend in the direction of the substrate thickness. The vias 17 electrically connect the first ground 15 and the shield plate 16.

[0023] The first strip line 18 and the second strip line 19 are for carrying high-frequency signals. As shown in Figure 1, the first strip line 18 and the second strip line 19 are provided between the hollow portion 12 and the lower surface 11b in the thickness direction of the substrate. The first strip line 18 and the second strip line 19 are positioned at approximately the same location in the thickness direction of the substrate. One end of the first strip line 18 and one end of the second strip line 19 are positioned below the magnet 13.

[0024] In this case, as shown in Figure 2E, one end of each strip faces the other in the lateral direction of the base material 11, and a gap is formed between them. The lateral direction of the base material 11 is the direction perpendicular to the thickness direction of the base material. In the first strip line 18 and the second strip line 19 shown in Figure 1, for example, a high-frequency signal flows from the first strip line 18 to the second strip line 19.

[0025] The second ground 20 is provided on the lower surface 11b of the base material 11. The second ground 20 is the ground for the first strip track 18 and the second strip track 19.

[0026] Therefore, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can move the magnet 13 in the substrate thickness direction inside the hollow portion 12 using a magnetic field generated by passing current through the drive coil 14. As a result, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can change the capacitance between the magnet 13 and the first strip line 18 and the second strip line 19. In this case, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can change the electrical characteristics of the high-frequency signals flowing through the first strip line 18 and the second strip line 19. At this time, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can change the direction and magnitude of the magnetic field by controlling the direction and magnitude of the current flowing through the drive coil 14, thereby adjusting the direction and amount of movement of the magnet 13.

[0027] For example, when moving the magnet 13 from its lower position within the hollow section 12 to its upper position, the multilayer substrate 100 with the built-in movable element supplies current to the drive coil 14 in such a way that the first coil section 14a generates an attractive force toward the magnet 13, and the second coil section 14b generates a repulsive force toward the magnet 13. As a result, the magnet 13 is attracted toward the drive coil 14 by the magnetic field that has passed through the shield plate 16. In other words, the magnet 13 moves upward within the hollow section 12. At this time, the greater the current value, the greater the amount of upward movement of the magnet 13.

[0028] As the magnet 13 moves upward, the distance between the magnet 13 and the strip lines 18 and 19 increases, thus reducing the capacitance between them. As a result, the high-frequency signal flows through the first strip line 18 and the second strip line 19 at a relatively high frequency.

[0029] On the other hand, when moving the magnet 13 from its upper position within the hollow section 12 to its lower position, the multilayer substrate 100 with the built-in movable element supplies current to the drive coil 14 in such a way that the first coil section 14a generates a repulsive force against the magnet 13, and the second coil section 14b generates an attractive force against the magnet 13. As a result, the magnet 13 moves away from the drive coil 14 due to the magnetic field it has passed through the shield plate 16. That is, the magnet 13 moves downward within the hollow section 12. At this time, the greater the current value, the greater the amount the magnet 13 moves downward.

[0030] As the magnet 13 moves downward, the distance between the magnet 13 and the strip lines 18 and 19 decreases, increasing the capacitance between them. As a result, the high-frequency signal flows through the first strip line 18 and the second strip line 19 at a relatively low frequency, even within the high-frequency range.

[0031] Next, the operation of the movable element-embedded multilayer substrate 100 according to Embodiment 1 will be explained with reference to Figure 3. Figure 3 is a diagram showing the operation of the movable element-embedded multilayer substrate 100 according to Embodiment 1. The solid arrows in Figure 3 indicate the direction of flow of high-frequency signals (GHz frequency), and the dashed-dotted arrows in Figure 3 indicate the radiation (GHz frequency) of high-frequency signals from the strip lines 18 and 19. The dotted lines in Figure 3 indicate the direction of generation of a magnetic field (kHz frequency) due to the energization of the drive coil 14.

[0032] As shown in Figure 3, when a high-frequency signal flows through the first strip line 18 and the second strip line 19, there is a risk of radiation of the high-frequency signal from the strip lines 18 and 19. This radiation is likely to leak out from the upper surface 11a of the substrate 11 toward the outside of the substrate, but it is blocked by the shield plate 16. The shield plate 16 also allows the magnetic field generated from the drive coil 14 through which the current flows to pass and reach the magnet 13.

[0033] Therefore, the thickness of the shielding plate 16, which allows the magnetic field generated by energizing the drive coil 14 to pass through but prevents the radiation of high-frequency signals from passing through, is set based on the conductivity and permeability of the shielding plate 16, the frequency of the current flowing through the drive coil 14, and the frequency of the high-frequency signals flowing through the strip lines 18 and 19.

[0034] Specifically, if the conductivity of the shield plate 16 is σ, the permeability of the shield plate 16 is μ, the thickness of the shield plate 16 is D, the frequency of the high-frequency signal flowing through the strip lines 18 and 19 is Fx, and the frequency of the current flowing through the drive coil 14 is Fy, then the thickness D of the shield plate 16 satisfies the following equation (1): 1 / √(π × Fy × μ × σ) >> D > 1 / √(π × Fx × μ × σ) ... (1)

[0035] In other words, the thickness D of the shield plate 16 is such that it is thinner than the penetration depth of the magnetic field at the frequency Fy of the current flowing through the drive coil 14 in the shield plate 16, and thicker than the penetration depth of radiation at the frequency Fx of the high-frequency signals flowing through the strip lines 18 and 19 in the shield plate 16. The penetration depth is the depth to which the frequency attenuates.

[0036] Therefore, the multilayer substrate 100 with a built-in movable element according to Embodiment 1 does not allow high-frequency signal radiation to penetrate the space where the drive coil 14 is located. As a result, the multilayer substrate 100 with a built-in movable element according to Embodiment 1 can apply the magnetic field generated by energizing the drive coil 14 to the magnet 13 while suppressing leakage of radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 is located.

[0037] As described above, the multilayer substrate 100 with a built-in movable element according to Embodiment 1 comprises a hollow portion 12 provided in a multilayer substrate 11, a magnet 13 which is a movable element made of a magnetic material and housed inside the hollow portion 12, a drive coil 14 provided in the substrate 11, strip lines 18 and 19 provided in the substrate 11, and a shield plate 16 provided in the substrate 11. The thickness of the shield plate 16 is such that it is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the drive coil 14 in the shield plate 16, and thicker than the penetration depth of radiation at the frequency of the high-frequency signals flowing through the strip lines 18 and 19 in the shield plate 16. Therefore, the multilayer substrate 100 with a built-in movable element according to Embodiment 1 can suppress the radiation of high-frequency signals to the outside while applying the magnetic field generated by energizing the drive coil 14 to the magnet 13.

[0038] Furthermore, in the movable element-embedded multilayer substrate 100 according to Embodiment 1, the drive coil 14 is arranged on one side of the hollow portion 12 in the substrate thickness direction, the strip lines 18 and 19 are arranged on the other side of the hollow portion 12 in the substrate thickness direction, and the shield plate 16 is arranged on one side of the hollow portion 12 in the substrate thickness direction. Therefore, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can suppress the radiation of high-frequency signals to the outside while applying the magnetic field generated by energizing the drive coil 14 to the magnet 13.

[0039] Furthermore, in the movable element-embedded multilayer substrate 100 according to Embodiment 1, the shield plate 16 is provided so as to close the opening surface on one side in the substrate thickness direction in the hollow portion 12. Therefore, the movable element-embedded multilayer substrate 100 according to Embodiment 1 can suppress leakage of high-frequency signal radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 is arranged.

[0040] Embodiment 2. The movable element-embedded multilayer substrate 200 according to Embodiment 2 will be described with reference to Figure 4. Figure 4 is a longitudinal cross-sectional view of the movable element-embedded multilayer substrate 200 according to Embodiment 2. Components having the same function as those described in the above-described embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0041] The mover-integrated multilayer substrate 200 according to Embodiment 2 shown in FIG. 4 is obtained by changing the installation position of the shield plate 16 with respect to the configuration of the mover-integrated multilayer substrate 100 according to Embodiment 1 shown in FIG. 1. In the mover-integrated multilayer substrate 200 according to Embodiment 2, the thickness of the shield plate 16 is also set to satisfy the above formula (1).

[0042] As shown in FIG. 4, the shield plate 16 is provided on the upper surface 11a of the base material 11. Therefore, the drive coil 14 is disposed between the hollow portion 12 and the shield plate 16 in the thickness direction of the base material. The magnetic field generated by energizing the drive coil 14 loops in the thickness direction of the base material.

[0043] Therefore, the mover-integrated multilayer substrate 200 according to Embodiment 2 can suppress the radiation of high-frequency signals to the outside of the substrate by providing the shield plate 16 on the upper surface 11a of the base material 11. Also, even when the shield plate 16 is provided on the upper surface 11a of the base material 11, the magnetic field generated by energizing the drive coil 14 loops in the thickness direction of the base material, so that it passes through the shield plate 16. Therefore, the magnetic field acts on the magnet 13 without being weakened by the shield plate 16.

[0044] As described above, in the mover-integrated multilayer substrate 200 according to Embodiment 2, the shield plate 16 is provided on the upper surface 11a disposed on one side in the thickness direction of the base material 11. Therefore, the mover-integrated multilayer substrate 200 according to Embodiment 2 can suppress the loss due to the shield plate 16 with respect to the magnetic field generated by energizing the drive coil 14.

[0045] Embodiment 3. The mover-integrated multilayer substrate 300 according to Embodiment 3 will be described with reference to FIG. 5. FIG. 5 is a longitudinal sectional view of the mover-integrated multilayer substrate 300 according to Embodiment 3. For the configurations having the same functions as those described in the above embodiments, the same reference numerals are given and the description thereof is omitted.

[0046] The mover-integrated multilayer substrate 300 according to Embodiment 3 shown in FIG. 5 is obtained by adding a sensor coil 31 of an eddy current displacement sensor to the configuration of the mover-integrated multilayer substrate 100 according to Embodiment 1 shown in FIG. 1.

[0047] The mover-integrated multilayer substrate 300 according to Embodiment 3 has an eddy current displacement sensor (not shown), and the sensor coil 31 of the eddy current displacement sensor is provided on the base material 11. The eddy current displacement sensor measures the distance to the magnet 13 using a high-frequency magnetic field. The eddy current displacement sensor generates a high-frequency magnetic field by passing a high-frequency current through the sensor coil 31. When the magnet 13 approaches within the magnetic field, an eddy current is generated on the surface of the magnet 13, and the impedance of the sensor coil 31 changes. The eddy current displacement sensor measures the distance to the magnet 13 by utilizing the change in the oscillation intensity due to this phenomenon.

[0048] The mover-integrated multilayer substrate 300 according to Embodiment 3 detects the distance to the magnet 13 measured by the eddy current displacement sensor, and based on the detected distance, controls the direction and magnitude of the current flowing through the drive coil 14 to perform position control of the magnet 13.

[0049] As shown in FIG. 5, the sensor coil 31 is disposed above the hollow portion 12, the drive coil 14, and the shield plate 16. The sensor coil 31 has a coil portion 31a, a ground 31b, and a via 31c. The coil portion 31a is disposed above the drive coil 14. The ground 31b is provided on the upper surface 11a of the base material 11. The via 31c extends in the thickness direction of the base material and electrically connects the central end of the coil portion 31a and the ground 31b.

[0050] Therefore, the thickness of the shield plate 16 that allows the magnetic fields generated by energizing the drive coil 14 and the sensor coil 31 to pass through and does not allow the radiation of high-frequency signals to pass through is set based on the conductivity and magnetic permeability of the shield plate 16, the frequency of the current flowing through the sensor coil 31, and the frequency of the high-frequency signals flowing through the strip lines 18 and 19.

[0051] Specifically, if the conductivity of the shield plate 16 is σ, the permeability of the shield plate 16 is μ, the thickness of the shield plate 16 is D, the frequency of the high-frequency signal flowing through the strip lines 18 and 19 is Fx, and the frequency of the current flowing through the sensor coil 31 is Fz, then the thickness D of the shield plate 16 satisfies the following equation (2): 1 / √(π × Fz × μ × σ) >> D > 1 / √(π × Fz × μ × σ) ... (2)

[0052] Here, the sensor coil 31 of the eddy current displacement sensor uses a sine wave with a frequency of several MHz. Therefore, the frequency of the current flowing through the sensor coil 31 (MHz) is higher than the frequency of the current flowing through the drive coil 14 (kHz). Consequently, the penetration depth into the shield plate 16 is shallower for the magnetic field generated by energizing the sensor coil 31 than for the magnetic field generated by energizing the drive coil 14. Therefore, in equation (2) above, only the frequency of the current flowing through the sensor coil 31 is used, out of the frequency of the current flowing through the drive coil 14 and the frequency of the current flowing through the sensor coil 31.

[0053] In other words, the thickness D of the shield plate 16 is such that it is thinner than the penetration depth of the magnetic field at the frequency Fz of the current flowing through the sensor coil 31 in the shield plate 16, and thicker than the penetration depth of the radiation at the frequency Fx of the high-frequency signals flowing through the strip lines 18 and 19 in the shield plate 16.

[0054] Therefore, the multilayer substrate 300 with a built-in movable element according to Embodiment 3 does not allow high-frequency signal radiation to penetrate the space where the drive coil 14 and the sensor coil 31 are located. As a result, the multilayer substrate 300 with a built-in movable element according to Embodiment 3 can apply the magnetic fields generated by energizing the drive coil 14 and the sensor coil 31 to the magnet 13 while suppressing leakage of radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 and the sensor coil 31 are located.

[0055] As described above, the movable element-embedded multilayer substrate 300 according to Embodiment 3 comprises a hollow portion 12 provided on a multilayer substrate 11, a magnet 13 which is a movable element made of a magnetic material and housed inside the hollow portion 12, a drive coil 14 provided on the substrate 11, strip lines 18 and 19 provided on the substrate 11, a shield plate 16 provided on the substrate 11, and a sensor coil 31 for an eddy current type displacement sensor provided on the substrate 11. The thickness of the shield plate 16 is such that it is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the sensor coil 31 in the shield plate 16, and thicker than the penetration depth of radiation at the frequency of the high-frequency signals flowing through the strip lines 18 and 19 in the shield plate 16. Therefore, the movable element-embedded multilayer substrate 300 according to Embodiment 3 can suppress the radiation of high-frequency signals to the outside while applying the magnetic field generated by energizing the drive coil 14 to the magnet 13.

[0056] Furthermore, in the movable element-embedded multilayer substrate 300 according to Embodiment 3, the drive coil 14 is arranged on one side of the hollow portion 12 in the substrate thickness direction, and the strip lines 18 and 19 are arranged on the other side of the hollow portion 12 in the substrate thickness direction. Therefore, the movable element-embedded multilayer substrate 300 according to Embodiment 3 can suppress the radiation of high-frequency signals to the outside while applying the magnetic field generated by energizing the drive coil 14 to the magnet 13.

[0057] Furthermore, in the movable element-embedded multilayer substrate 300 according to Embodiment 3, the shield plate 16 is arranged between the hollow portion 12 and the drive coil 14 in the substrate thickness direction, and the sensor coil 31 is arranged on one side of the drive coil 14 in the substrate thickness direction. Therefore, the movable element-embedded multilayer substrate 300 according to Embodiment 3 can suppress leakage of high-frequency signal radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 and the sensor coil 31 are arranged.

[0058] Embodiment 4. The movable element-embedded multilayer substrate 400 according to Embodiment 4 will be described with reference to Figure 6. Figure 6 is a longitudinal cross-sectional view of the movable element-embedded multilayer substrate 400 according to Embodiment 4. Components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0059] The multilayer substrate 400 with a built-in movable element shown in Figure 6, according to Embodiment 4, has a configuration in which the installation position of the sensor coil 31 is changed compared to the multilayer substrate 300 with a built-in movable element shown in Figure 5, according to Embodiment 3.

[0060] As shown in Figure 6, the movable element-embedded multilayer substrate 400 according to Embodiment 4 is equipped with a shield plate 41 as a second shield plate in place of the second ground 20. The shield plate 41 is a conductive plate. The shield plate 41 is positioned below the first strip line 18 and the second strip line 19 inside the substrate 11. The shield plate 41 allows the magnetic field generated by energizing the sensor coil 31 to pass through, but prevents the radiation of high-frequency signals from passing through. The shield plate 41 functions as a ground for the first strip line 18 and the second strip line 19.

[0061] The sensor coil 31 is positioned below the hollow section 12, the first strip line 18, the second strip line 19, and the shield plate 41. The coil section 31a is positioned below the shield plate 41. The ground 31b is provided on the lower surface 11b of the base material 11. The via 31c extends in the thickness direction of the base material and electrically connects the center end of the coil section 31a to the ground 31b.

[0062] In the movable element-embedded multilayer substrate 400 according to Embodiment 4, the thickness of the shield plate 16 is set to satisfy formula (1) above, and the thickness of the shield plate 41 is set to satisfy formula (2) above.

[0063] Therefore, the multilayer substrate 400 with a built-in movable element according to Embodiment 4 does not allow high-frequency signal radiation to penetrate the space where the drive coil 14 and the sensor coil 31 are located. As a result, the multilayer substrate 400 with a built-in movable element according to Embodiment 4 can apply the magnetic fields generated by energizing the drive coil 14 and the sensor coil 31 to the magnet 13 while suppressing leakage of radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 and the sensor coil 31 are located.

[0064] In the movable element-embedded multilayer substrate 400 according to Embodiment 4, the shield plate 41 is arranged on one side of the strip lines 18 and 19 in the substrate thickness direction, and the sensor coil 31 is arranged on the other side of the shield plate 41 in the substrate thickness direction. Therefore, the movable element-embedded multilayer substrate 400 according to Embodiment 4 can suppress losses due to the shield plate 16 with respect to the magnetic field generated by energizing the drive coil 14, and can suppress losses due to the shield plate 41 with respect to the magnetic field generated by energizing the sensor coil 31.

[0065] Embodiment 5. The movable element-embedded multilayer substrate 500 according to Embodiment 5 will be described with reference to Figures 7 and 8. Figure 7 is a longitudinal cross-sectional view of the movable element-embedded multilayer substrate 500 according to Embodiment 5. Figure 8 is a cross-sectional view taken along the line F-F in Figure 7. Components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0066] The multilayer substrate 500 with a built-in movable element shown in Figure 7, according to Embodiment 5, is equipped with a shield plate 51 instead of the shield plate 16 of the multilayer substrate 100 with a built-in movable element shown in Figure 1, according to Embodiment 1. As described above, the shield plate 16 allows magnetic fields to pass through but prevents the radiation of high-frequency signals by changing its thickness. The shield plate 51 allows magnetic fields generated by energizing the drive coil 14 to pass through but prevents the radiation of high-frequency signals by changing the mesh hole shape.

[0067] As shown in Figure 7, the first shield plate 51 is a conductive plate and constitutes a cover member for the hollow portion 12. Specifically, the shield plate 51 is positioned inside the base material 11 so as to cover the entire upper opening surface (one-sided opening surface) of the hollow portion 12. The shape of the shield plate 51 can be adjusted as appropriate, as long as it can cover the entire upper opening surface of the hollow portion 12. The shield plate 51 functions as a ground for the drive coil 14 together with the first ground 15.

[0068] As shown in Figure 8, the shield plate 51 has a mesh shape. Therefore, the shield plate 51 has multiple openings 51a that run through it in the thickness direction, forming mesh holes. Each opening 51a is filled with the base material 11.

[0069] Here, if λx is the wavelength of the high-frequency signal flowing through the first strip line 18 and the second strip line 19, the longest length of the opening 51a is less than or equal to λx / 2. Therefore, the radiation of the high-frequency signal does not pass through the shield plate 51. Although Figure 8 shows an example where the shape of the opening 51a is square, the shape of the opening 51a may be triangular, circular, rectangular, etc. As shown in Figure 8, when the opening 51a is square, its longest length is the diagonal.

[0070] Therefore, the thickness of the shield plate 51, which allows the magnetic field generated by energizing the drive coil 14 to pass through but prevents the radiation of high-frequency signals from passing through, is set based on the average conductivity and average permeability of the shield plate 51, the frequency of the current flowing through the drive coil 14, and the frequency of the high-frequency signals flowing through the strip lines 18 and 19. The average conductivity and average permeability of the shield plate 51 are calculated using the average volume of the base material 11 filled in each opening 51a.

[0071] Specifically, if the average conductivity of the shield plate 51 is σave, the average permeability of the shield plate 51 is μave, the thickness of the shield plate 51 is D, the frequency of the high-frequency signal flowing through the strip lines 18 and 19 is Fx, and the frequency of the current flowing through the drive coil 14 is Fy, then the thickness D of the shield plate 51 satisfies the following equation (3): 1 / √(π × Fy × μave × σave) >> D > 1 / √(π × Fx × μave × σave) ... (3)

[0072] In other words, the thickness D of the shield plate 51 is such that it is thinner than the penetration depth of the magnetic field at the frequency Fy of the current flowing through the drive coil 14 in the shield plate 51, and thicker than the penetration depth of radiation at the frequency Fx of the high-frequency signals flowing through the strip lines 18 and 19 in the shield plate 51.

[0073] Therefore, the multilayer substrate 500 with a built-in movable element according to Embodiment 5 does not allow the radiation of high-frequency signals to penetrate into the space where the drive coil 14 is located. As a result, the multilayer substrate 500 with a built-in movable element according to Embodiment 5 can apply the magnetic field generated by energizing the drive coil 14 to the magnet 13 while suppressing leakage of radiation to the outside of the substrate and unwanted resonance in the space where the drive coil 14 is located.

[0074] In the movable element-embedded multilayer substrate 500 according to Embodiment 5, the shield plate 51 has a plurality of openings 51a whose longest length is less than or equal to half the wavelength of the high-frequency signal flowing through the strip lines 18 and 19. The penetration depth of the magnetic field and the penetration depth of the radiation are corresponding to the average volume of the substrate 11 filled in the openings 51a. Therefore, even if there are not enough options for the thickness of the shield plate 16, the movable element-embedded multilayer substrate 500 according to Embodiment 5 can suppress the radiation of high-frequency signals to the outside while allowing the magnetic field generated by energizing the drive coil 14 to act on the magnet 13 by using a mesh-shaped shield plate 51.

[0075] Embodiment 6. The movable element-embedded multilayer substrate 600 according to Embodiment 6 will be described with reference to Figure 9. Figure 9 is a longitudinal cross-sectional view of the movable element-embedded multilayer substrate 600 according to Embodiment 6. Components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0076] The multilayer substrate 600 with a built-in movable element according to Embodiment 6 shown in Figure 9 has a configuration in which a conductive layer 61 is added to the multilayer substrate 100 with a built-in movable element according to Embodiment 1 shown in Figure 1.

[0077] As shown in Figure 9, the conductor layer 61 is provided so as to cover all of the outer surfaces of the magnet 13. However, it is sufficient for the conductor layer 61 to cover at least the lower surfaces of the magnet 13 that face the first strip line 18 and the second strip line 19.

[0078] When a magnet 13 with low conductivity is subjected to the magnetic field of a high-frequency signal, losses increase, and the high-frequency signal deteriorates. For this reason, the magnet 13 has a conductive layer 61 on its outer surface to increase its conductivity. However, if the thickness of the conductive layer 61 is too thick, the magnetic field generated by energizing the drive coil 14 may not act on the magnet 13.

[0079] Therefore, the thickness of the conductor layer 61, which allows the magnetic field generated by energizing the drive coil 14 to pass through but prevents the radiation of high-frequency signals from passing through, is set based on the conductivity and permeability of the conductor layer 61, the frequency of the current flowing through the drive coil 14, and the frequency of the high-frequency signals flowing through the strip lines 18 and 19.

[0080] Specifically, if the conductivity of the conductor layer 61 is σm, the permeability of the conductor layer 61 is μm, the thickness of the conductor layer is Dm, the frequency of the high-frequency signal flowing through the strip lines 18 and 19 is Fx, and the frequency of the current flowing through the drive coil 14 is Fy, then the thickness Dm of the conductor layer 61 satisfies the following equation (4): 1 / √(π × Fy × μm × σm) >> D > 1 / √(π × Fx × μm × σm) ... (4)

[0081] In other words, the thickness Dm of the conductor layer 61 is such that it is thinner than the penetration depth of the magnetic field at the frequency Fy of the current flowing through the drive coil 14 in the conductor layer 61, and thicker than the penetration depth of radiation at the frequency Fx of the high-frequency signals flowing through the strip lines 18 and 19 in the conductor layer 61.

[0082] Therefore, the multilayer substrate 600 with a built-in movable element according to Embodiment 6 can apply the magnetic field generated by energizing the drive coil 14 to the magnet 13, and reduce the loss of conductivity due to the radiation of high-frequency signals in the magnet 13.

[0083] As described above, the movable element-embedded multilayer substrate 600 according to Embodiment 5 includes a conductor layer 61 that covers at least the lower surface of the magnet 13 facing the strip lines 18 and 19. The thickness of the conductor layer 61 is such that it is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the drive coil 14, and thicker than the penetration depth of the radiation at the frequency of the high-frequency signal flowing through the strip lines 18 and 19. Therefore, the movable element-embedded multilayer substrate 600 according to Embodiment 5 can apply the magnetic field generated by energizing the drive coil 14 to the magnet 13, while reducing the loss of conductivity due to the radiation of high-frequency signals in the magnet 13.

[0084] Within the scope of this disclosure, it is possible to freely combine the embodiments, modify any component in each embodiment, or omit any component in each embodiment.

[0085] The multilayer substrate with a built-in movable element according to this disclosure is suitable for use in multilayer substrates with built-in movable elements because, by setting the thickness of the shielding plate based on the penetration depth of the magnetic field generated by energizing the drive coil and the penetration depth of the radiation of high-frequency signals flowing through the strip line, it is possible to apply a magnetic field to the movable element while suppressing the radiation of high-frequency signals to the outside.

[0086] 11 Substrate, 11a Top surface, 11b Bottom surface, 12 Hollow section, 13 Magnet, 14 Driving coil, 14a First coil section, 14b Second coil section, 14c Via for coil connection, 15 First ground, 16 Shielding plate, 17 Via, 18 First strip line, 19 Second strip line, 20 Second ground, 31 Sensor coil, 31a Coil section, 31b Ground, 31c Via, 41 Shielding plate, 51 Shielding plate, 51a Opening, 61 Conductor layer, 100, 200, 300, 400, 500, 600 Multilayer substrate with built-in movable element.

Claims

1. A multilayer substrate with a built-in movable element, comprising: a hollow portion provided in a multilayer substrate; a movable element housed inside the hollow portion and made of a magnetic material; a drive coil provided in the substrate; a strip line provided in the substrate; and a shield plate provided in the substrate, wherein the thickness of the shield plate is such that it is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the drive coil in the shield plate, and thicker than the penetration depth of the radiation at the frequency of the high-frequency signal flowing through the strip line in the shield plate.

2. The movable element-embedded multilayer substrate according to claim 1, characterized in that the drive coil is arranged on one side of the hollow portion in the thickness direction of the substrate, the strip line is arranged on the other side of the hollow portion in the thickness direction of the substrate, and the shield plate is arranged on one side of the hollow portion in the thickness direction of the substrate.

3. The movable element-embedded multilayer substrate according to claim 2, characterized in that the shield plate is provided so as to close the opening surface on one side in the thickness direction of the substrate in the hollow portion.

4. The movable element-embedded multilayer substrate according to claim 2, characterized in that the shield plate is provided on a surface of the substrate that is located on one side in the thickness direction.

5. The multilayer substrate with a built-in movable element according to any one of claims 1 to 4, wherein the shield plate has a plurality of openings whose longest length is less than or equal to half the wavelength of the high-frequency signal flowing through the strip line, and the penetration depth of the magnetic field and the penetration depth of the radiation are to a depth corresponding to the average volume of the substrate filled in the openings.

6. A multilayer substrate with a built-in movable element, comprising: a hollow portion provided in a multilayer substrate; a movable element housed inside the hollow portion and made of a magnetic material; a drive coil provided in the substrate; a strip line provided in the substrate; a shield plate provided in the substrate; and a sensor coil for a displacement sensor provided in the substrate, wherein the thickness of the shield plate is such that it is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the sensor coil in the shield plate, and thicker than the penetration depth of radiation at the frequency of the high-frequency signal flowing through the strip line in the shield plate.

7. The movable element-embedded multilayer substrate according to claim 6, characterized in that the drive coil is arranged on one side of the hollow portion in the thickness direction of the substrate, and the strip line is arranged on the other side of the hollow portion in the thickness direction of the substrate.

8. The multilayer substrate with a built-in movable element according to claim 7, characterized in that the shield plate is disposed between the hollow portion and the drive coil in the substrate thickness direction, and the sensor coil is disposed on one side of the drive coil in the substrate thickness direction.

9. The movable element-integrated multilayer substrate according to claim 7, characterized in that the shield plate is arranged on one side of the strip line in the substrate thickness direction, and the sensor coil is arranged on the other side of the shield plate in the substrate thickness direction.

10. A multilayer substrate with a movable element according to any one of claims 1 to 9, comprising a conductor layer covering at least the surface of all outer surfaces of the movable element that faces the strip line, wherein the thickness of the conductor layer is thinner than the penetration depth of the magnetic field at the frequency of the current flowing through the drive coil in the conductor layer, and thicker than the penetration depth of the radiation at the frequency of the high-frequency signal flowing through the strip line in the conductor layer.

Images