JP5509531B2 - Magnetic coupler - Google Patents

Description

  The present invention relates to a magnetic coupler that includes a thin film coil and a magnetoresistive effect element and performs signal transmission between a plurality of electric circuits insulated from each other in a non-contact manner.

  2. Description of the Related Art Conventionally, photocouplers, pulse transformers, and the like are known as devices that transmit signals from one electric circuit to the other in a non-contact manner between a plurality of electric circuits insulated from each other. However, the photocoupler has a remarkable change over time such as deterioration of light emitting diodes (LEDs) and a decrease in current transmission rate, and a large signal transmission delay. On the other hand, since the pulse transformer uses a winding coil, the signal transmission delay is small, but the shape and weight are large, and the operable temperature is low. There are also couplers in which the winding coil of the pulse transformer is replaced with a thin film coil, but the power consumption is large because the efficiency of the coil receiving the magnetic field is poor.

Therefore, magnetic couplers have been developed to solve the above problems (see, for example, Patent Documents 1 to 9). This magnetic coupler detects a change in current flowing through a signal line from one electric circuit system in a non-contact manner as a change in induced magnetic field by a magnetoresistive effect element, and transmits an electric signal to the other electric circuit system. However, it has been attracting attention as having excellent operational reliability with a simple configuration.
Japanese translation of PCT publication No. 2003-526083 JP 2001-94174 A JP 2001-135534 A JP 2001-135535 A JP 2001-135536 A JP 2001-135537 A JP 2001-196250 A JP 2001-93763 A JP 62-40786 A

  As such a magnetic coupler, for example, as disclosed in Patent Document 1, a magnetic magnetoresistive film having a planar shape patterned in a meandering shape has been proposed. By doing so, it is expected that the induction magnetic field from the signal line (or the thin film coil connected thereto) can be efficiently detected and the detection accuracy can be improved.

  However, in a zigzag magnetoresistive film, the magnetization of the magnetization free layer (free layer) is difficult to rotate at the bent portion due to its shape or due to the occurrence of a domain wall. That is, at the bent portion, the magnetization of the magnetization free layer is not easily aligned in the direction along the applied induced magnetic field. Therefore, there is a concern that hysteresis occurs in the magnitude of the magnetization of the magnetization free layer with respect to the applied induced magnetic field, and the detection sensitivity and responsiveness of the induced magnetic field may be impaired.

  The present invention has been made in view of such problems, and an object thereof is to provide a magnetic coupler that operates with higher sensitivity and higher accuracy.

  A magnetic coupler according to the present invention includes a coil and a magnetoresistive effect element that detects an induced magnetic field generated by a current flowing through the coil. The magnetoresistive effect element extends in a band shape and has an edge in its extending direction. A plurality of sub-elements connected to each other at a predetermined distance from each other by a connecting portion. Here, the “predetermined distance from the edge in the extending direction” refers to the length in the extending direction of the portion where the magnetization orientation disorder occurs in the magnetization free layer of the sub-element.

  In the magnetic coupler of the present invention, the plurality of strip-like sub-elements in the magnetoresistive effect element are connected to each other by the connecting portion at a position separated by a predetermined distance from the edge in the extending direction of the magnetoresistive effect element. The sense current flowing through the sub-element does not flow through the end of the sub-element. Therefore, the sense current is not affected by the magnetization orientation disorder of the magnetization free layer at the end of the sub-element, and the occurrence of hysteresis in the relationship between the applied induced magnetic field and the magnetization magnitude of the magnetization free layer is suppressed. Is done.

  In the magnetic coupler of the present invention, it is preferable that the predetermined distance from the edge in the extending direction of the sub element is larger than the width of the sub element. This is because a plurality of sub-elements can be connected to each other by sufficiently avoiding an end portion where the magnetization orientation disorder in the magnetization free layer may occur. The width of the sub element refers to a dimension in a direction perpendicular to the extending direction.

  In the magnetic coupler of the present invention, it is preferable that the edge of the sub element in the extending direction has a curved contour. This is because the magnetization orientation disorder in the magnetization free layer is less likely to occur, and the predetermined distance from the edge in the extending direction of the sub-element can be shortened. That is, the sub-elements can be connected to each other at a position closer to the edge, and an area (effective area) that can be used when detecting the induced magnetic field is expanded.

  In the magnetic coupler of the present invention, it is desirable that the connecting portion that connects the sub elements is made of a nonmagnetic conductor. This is because if the coupling portion is a magnetic body, an error in the sense current may occur due to an induced magnetic field from the coil.

  Further, in the magnetic coupler of the present invention, the plurality of sub-elements have both end faces inclined in the width direction perpendicular to the extending direction of the sub-elements, and the connecting portion extends in the width direction of the sub-elements, and The sub-element may be formed so as to cover the upper surface and both end surfaces. This is because the contact area between the sub-element and the connecting portion increases, the resistance value decreases, and a change in the sense current during operation is likely to appear.

  According to the magnetic coupler of the present invention, a plurality of strip-shaped sub-elements constituting the magnetoresistive effect element are connected to each other at a predetermined distance from the edge in the extending direction, and the plurality of sub-elements are used to Since the induced magnetic field is detected, the sense current can be passed to a region of the plurality of sub-elements in which the magnetization orientation disorder of the magnetization free layer is small. Therefore, for example, it is possible to detect the induced magnetic field from the coil with higher sensitivity and higher accuracy than when a plurality of strip-shaped sub-elements are connected to each other in the portion including the edge.

  According to the magnetic coupler of the present invention, in particular, by setting the predetermined distance from the edge in the extending direction of the sub element to be larger than the width of the sub element, the magnetization free layer at the end of the sub element is It is possible to reliably avoid the influence of the disorder of magnetization orientation. Further, if the contour of the edge in the extending direction of the sub-element is made of a curve, the occurrence of a domain wall is suppressed in the magnetization free layer at the end of the sub-element, and the orientation of magnetization can be enhanced. As a result, an area (effective area) that can be used when detecting the induced magnetic field among the sub-elements can be expanded, and the detection sensitivity can be increased.

  Furthermore, according to the magnetic coupler of the present invention, the plurality of sub-elements are assumed to be inclined at both end surfaces in the width direction perpendicular to the extending direction of the sub-elements, and the connecting portion extends in the width direction of the sub-elements. In addition, by forming the sub-element so as to cover the upper surface and both end faces, the contact resistance between the connecting portion and the sub-element can be reduced, which is advantageous for power saving.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
First, the configuration of the magnetic coupler as the first embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a plan view showing the configuration of the magnetic coupler of the present embodiment. 2A is an enlarged plan view of the main part of the magnetic coupler shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. 2A. FIG. Note that the directions of all arrows of the signal current Im, the induction magnetic field Hm, and the bias magnetic field Hb shown in FIG. 1 indicate relative directions to the magnetoresistive elements 31 to 34 (described later). This magnetic coupler is a device that transmits a signal from an electric circuit to another electric circuit in an electrically non-contact state, and is an effective means for blocking noise while transmitting a necessary signal. .

  As shown in FIGS. 1 and 2, the magnetic coupler of the present embodiment is a thin film that is wound on the first layer L <b> 1 (FIG. 2B) that extends along the XY plane on the substrate 10. The first to fourth magneto-resistive effect (MR) elements 31 to 34 located in a region corresponding to the thin film coil 20 in the coil 20 and the second layer L2 that is an upper layer of the first layer L1. And an intermediate layer 13 positioned between the thin film coil 20 and the first to fourth MR elements 31 to 34 in the thickness direction. Further, the magnetic coupler includes yokes 41 to 44 disposed on the winding center side and the winding outer peripheral side of the thin film coil 20 in the second layer L2. In the first level L1, the gaps between the winding bodies (for example, the linear patterns 21 described later) of the thin film coil 20 are filled with the insulating layer 12, and in the second level L2, the yokes 41 to 44 and the first layer L1 are arranged. The fourth MR elements 31 to 34 are all covered with the insulating layer 14 (FIG. 2B). In FIG. 1 and FIG. 2, illustration of wiring patterns connecting the first to fourth MR elements 31 to 34 is omitted.

The base 10 is a rectangular substrate that supports the entire magnetic coupler, and is made of, for example, ceramics such as glass, silicon (Si), aluminum oxide (Al ₂ O ₃ ), or AlTiC (Al ₂ O ₃ —TiC). ing. For example, an insulating layer 11 containing ceramics such as silicon oxide (SiO ₂ ) or Al ₂ O ₃ may be provided so as to cover the substrate 11.

  The thin film coil 20 includes two terminals 20S and 20E at both ends. For example, when the thin film coil 20 is viewed from the second layer L2 side so as to go from the winding center side terminal 20S to the winding outer peripheral side terminal 20E, It is a thin film conductive layer wound clockwise, and is made of a highly conductive material such as copper (Cu). The region where the thin film coil 20 is formed is classified into a pair of linear regions R21 and a pair of curved regions R22 connecting them. The straight line region R21 is a region that extends linearly along the X-axis direction and is occupied by a plurality of straight line patterns 21 arranged at predetermined intervals in the Y-axis direction. One curve region R22 is a region occupied by a curved curve pattern 22 formed so as to connect one ends of the plurality of linear patterns 21. Here, it is desirable that the plurality of linear patterns 21 have uniform cross-sectional areas in the longitudinal direction (X-axis direction), are the same as each other, and are arranged at equal intervals.

  The first and second MR elements 31 and 32 are arranged at positions corresponding to one linear region R21 in the stacking direction, and the third and fourth MR elements 33 and 34 are the other straight line in the stacking direction. It arrange | positions in the position corresponding to area | region R21 (refer FIG. 1).

  As shown in FIGS. 1 and 2, the first MR element 31 has a plurality of strip-like patterns 311 connected in series between a pair of terminals 31S and 31E. The strip pattern 311 extends in the radial direction (Y-axis direction) of the thin-film coil 20 and is disposed adjacent to each other in the winding direction (X-axis direction) of the thin-film coil 20. That is, the first MR element 31 includes a plurality of strip-like patterns 311 arranged in parallel so that the longitudinal direction is the radial direction of the thin film coil 20 between the terminal 31S and the terminal 31E. It is configured in a zigzag manner. The connecting portion 312 is made of a nonmagnetic highly conductive material such as gold (Au), silver (Ag), or copper (Cu). The second to fourth MR elements 32 to 34 have the same configuration. That is, in the second to fourth MR elements 32 to 34, the band-like patterns 321, 331, and 341 are connected between the pair of terminals 32S and 32E, the pair of terminals 33S and 33E, or the pair of terminals 34S and 34E, respectively. It is configured to be connected in series so as to be connected in a zigzag manner via (not shown). 1 and 2 show the case where each of the first to fourth MR elements 31 to 34 has nine belt-like patterns, the number is not limited thereto.

  The band-like patterns 311, 321, 331, and 341 in the first to fourth MR elements 31 to 34 are all caused by the signal current Im flowing through the thin film coil 20 when a constant sense current (readout current) flows. The resistance value changes according to the induced magnetic field Hm generated. In that case, the change in the resistance value of the belt-like patterns 311 and 321 and the change in the resistance value of the belt-like patterns 331 and 341 are in opposite directions. That is, if the resistance values of the band-shaped patterns 311 and 321 are increased, the resistance values of the band-shaped patterns 331 and 341 are decreased. More specifically, when the signal current Im flows through the thin film coil 20 so as to go from the terminal 20S to the terminal 20E, an induced magnetic field Hm is applied to the first and second MR elements 31 and 32 in the + Y direction. On the other hand, the induced magnetic field Hm is applied to the third and fourth MR elements 33 and 34 in the -Y direction.

  The configuration of the first to fourth MR elements 31 to 34 will be described in more detail with reference to FIGS. 3 (A) and 3 (B). Here, the first MR element 31 will be described as a representative. FIG. 3A is an enlarged plan view showing a main part of the first MR element 31, and FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB shown in FIG. It is. As shown in FIG. 3A, the connecting portion 312 is provided at a position separated from the edge 311T of the strip pattern 311 by a predetermined distance L in the extending direction of the strip pattern 311. Here, the distance L is preferably larger than the width W of the belt-like pattern 311. In the portion of the belt-like pattern 311 that is included between the edge 311T and the position of the predetermined distance L (hereinafter, simply referred to as the edge portion 311Z of the belt-like pattern 311), the magnetization free layer 61 is caused by its shape and the like. The magnetization orientation disorder (described later) is likely to occur. Therefore, by providing the connection portion 312 at a portion other than the end portion of the band-shaped pattern 311 and connecting the plurality of band-shaped patterns 311 to each other, the magnetization orientation disorder of the magnetization free layer 61 during operation is caused to the sense current. The adverse effect is reduced.

  Further, as shown in FIG. 3B, both end surfaces 35 of the belt-like pattern 311 in the width direction (X-axis direction) orthogonal to the extending direction are inclined surfaces. The connecting portion 312 is preferably formed so as to extend in the width direction of the band-shaped pattern 311 and to cover the upper surface 36 and both end surfaces 35 of the band-shaped pattern 311. This is because the contact area between the belt-like pattern 311 and the connecting portion 312 increases, the resistance value decreases, and a change in the sense current during operation tends to appear.

  Next, with reference to FIG. 4, the structure of the strip | belt-shaped patterns 311,321,331,341 is demonstrated in detail. FIG. 3 is an exploded perspective view showing the structure of the band-like patterns 311, 321, 331, 341 in an exploded manner. The band-like patterns 311, 321, 331, 341 all have the same configuration.

  The band-shaped patterns 311, 321, 331, and 341 have a spin valve structure, and the magnetization free layer 61, the intermediate layer 62, the magnetization fixed layer 63, the antiferromagnetic layer 64, and the protective film 65 are, for example, intermediate. The layer 13 is laminated in order from the layer 13 side.

  The magnetization free layer 61 changes the direction of the magnetization J61 according to the magnitude and direction of the induction magnetic field Hm, and is made of a soft magnetic material such as nickel iron alloy (NiFe). The magnetization free layer 61 has an easy axis AE61 parallel to the Y axis. Further, the lower surface of the magnetization free layer 61 (the surface opposite to the intermediate layer 62) may be protected by a protective film (not shown).

  The intermediate layer 62 is made of a nonmagnetic material such as copper (Cu) that does not exhibit specific magnetization, and has an upper surface in contact with the magnetization fixed layer 63 and a lower surface in contact with the magnetization free layer 61. The intermediate layer 62 is preferably made of a nonmagnetic metal having high conductivity such as gold (Au) in addition to copper.

  The magnetization fixed layer 63 is made of a ferromagnetic material such as cobalt (Co) or cobalt iron alloy (CoFe), and has a magnetization J63 fixed in the + Y direction, for example.

  The antiferromagnetic layer 64 is made of an antiferromagnetic material such as platinum manganese alloy (PtMn) or iridium manganese alloy (IrMn). The antiferromagnetic film 65 is in a state in which the spin magnetic moment in the + X direction and the spin magnetic moment in the opposite direction (−X direction) completely cancel each other, and the direction of the magnetization J63 of the magnetization fixed layer 63 is fixed. It works to do.

  The protective film 65 is made of a relatively chemically stable nonmagnetic material such as tantalum (Ta) or hafnium (Hf), and protects the magnetization fixed layer 5364, the antiferromagnetic layer 64, and the like. However, as shown in FIG. 3B, the protective film 65 is removed from the portion covered with the coupling portion 312 so that the antiferromagnetic layer 64 and the coupling portion 312 are in direct contact with each other. It is desirable. This is to reduce the connection resistance between the strip pattern 311 and the connecting portion 312.

  FIG. 4 shows a no-load state in which the induction magnetic field Hm is not applied (that is, a state in which the external magnetic field is zero). In this case, the magnetization J61 of the magnetization free layer 61 is parallel to the easy axis AE61 and is substantially parallel to the magnetization J63 of the magnetization fixed layer 63. In addition, an exchange bias magnetic field Hin (hereinafter simply referred to as “exchange bias magnetic field Hin”) along the direction of the magnetization J63 is generated between the magnetization free layer 61 and the magnetization fixed layer 63, and the intermediate layer 62 is formed. Interact with each other. The intensity of the exchange bias magnetic field Hin changes as the spin of the magnetization free layer 61 rotates according to the mutual distance between the magnetization free layer 61 and the magnetization fixed layer 63 (that is, the thickness of the intermediate layer 62). Therefore, the exchange bias magnetic field Hin can be apparently zero.

  FIG. 4 shows a configuration example in the case where the magnetization free layer 61, the intermediate layer 62, the magnetization fixed layer 63, and the antiferromagnetic layer 64 are laminated in this order from the bottom (from the side of the intermediate layer 13). However, the present invention is not limited to this, and it may be configured in the reverse order.

  In the belt-like patterns 311, 321, 331, and 341 having the above-described structure, the magnetization J61 of the magnetization free layer 61 is rotated by the application of the induction magnetic field Hm, and thereby the relative angle between the magnetization J61 and the magnetization J63 is changed. The relative angle is determined by the magnitude and direction of the induction magnetic field Hm. That is, if the strip-shaped patterns 311, 321, 331, and 341 are given a component of the induced magnetic field Hm that is parallel or anti-parallel to the magnetization J 63 (a component in the + Y direction or the −Y direction), there is no effect shown in FIG. From the load state, the direction of the magnetization J61 is inclined in the + Y direction or the −Y direction, and the resistance values of the band-like patterns 311, 321, 331, and 341 increase or decrease. More specifically, when the induction magnetic field Hm in the + Y direction is applied, the magnetization J61 is tilted in the + Y direction and approaches a state parallel to the magnetization J63, so that the resistance values of the band-like patterns 311 321 331 341 decrease. On the other hand, when the induced magnetic field Hm in the -Y direction is applied, the magnetization J61 is inclined in the -Y direction and approaches a state antiparallel to the magnetization J63, so that the resistance values of the strip patterns 311, 321, 331, and 341 increase.

The intermediate layer 13 is provided, for example, so as to be in contact with both the thin film coil 20 and the first to fourth MR elements 31 to 34, and electrical insulation between the thin film coil 20 and the first to fourth MR elements 31 to 34. Functions as an insulating member. For example, as illustrated in FIG. 5A, the intermediate layer 13 has a stacked structure including a plurality of insulating films 132 separated by a conductive film 131. The conductive film 131 is made of a nonmagnetic conductive material and is thinner than the insulating film 132. As a constituent material of the conductive film 131, a material having a lower conductivity than copper (Cu), gold (Au), silver (Ag), aluminum (Al), or the like (for example, a conductivity of 1 × 10 ⁷ S / m or less). A material having a conductivity of 3 × 10 ⁶ S / m or less, such as titanium (Ti). This is to suppress the eddy current caused by the induction magnetic field Hm from the thin film coil 20 from flowing inside the conductive film 131. Since the eddy current has an effect of preventing the magnetic field application from the thin film coil 20 to the MR element first to fourth MR elements 31 to 34, suppressing the eddy current itself results in the sensitivity of the magnetic coupler as a whole. improves. Specific examples of the constituent material of the conductive film 131 include the above-described titanium (Ti), metals such as chromium (Cr), platinum (Pt), tantalum (Ta), zirconium (Zr), alloys thereof, or LaNiO3. And conductive oxides such as ITO (tin-doped indium oxide). On the other hand, the insulating film 132 is made of a nonmagnetic insulating material such as aluminum oxide (AlOx), zirconium oxide (ZrO ₂ ), aluminum nitride (AlN), silicon nitride (SiN), silicon oxide (SiO ₂ ), or polyimide. . Although aluminum oxide is described as AlOx here, a composition closer to the stoichiometric composition Al ₂ O ₃ is preferable in terms of withstand voltage. When the intermediate layer 13 includes a plurality of conductive films 131, their thicknesses may be different from each other. In addition, the plurality of conductive films 131 may or may not be stacked at equal intervals in the thickness direction. That is, the thicknesses of the plurality of insulating films 132 may be the same or different from each other.

  By having such a laminated structure, the intermediate layer 13 has a higher withstand voltage than a single layer structure made of an insulating material when the thickness is constant. The form of the intermediate layer 13 is not limited to the three-layer structure in which the two insulating films 132 are separated by one conductive film 131. For example, as shown in FIG. A five-layer structure in which the two conductive films 131 are separated may be employed. Alternatively, a larger number of conductive films 131 and insulating films 132 may be alternately stacked. This is because a greater number of conductive films 131 and insulating films 132 are alternately stacked in this manner, thereby further improving the withstand voltage of the intermediate layer 13 as a whole. 5A and 5B respectively show configuration examples of cross sections in which the intermediate layer 13 shown in FIG. 2 is enlarged.

  The yokes 41 to 44 are made of a soft magnetic material having a high magnetic permeability such as permalloy (NiFe), and the first to fourth MR elements 31 to 34 generate an induced magnetic field Hm generated by the signal current Im flowing through the thin film coil 20. It has a function to guide it toward. The yokes 41 and 42 are disposed to face each other so as to sandwich the first and second MR elements 31 and 32 in the radial direction (Y-axis direction) of the thin film coil 20. Similarly, the yokes 43 and 44 are disposed opposite to each other so as to sandwich the first and second MR elements 31 and 32 in the radial direction (Y-axis direction) of the thin film coil 20.

  Here, the yokes 41 to 44 may be provided at positions that overlap the linear region R21 in the stacking direction, or may be provided at positions that do not overlap. However, the yokes 41 and 43 on the winding center side of the thin film coil 20 are provided closer to the center position CL in the Y-axis direction of the linear region R21 than the yokes 42 and 44 on the winding outer periphery side of the thin film coil. Is desirable. That is, regarding the relationship between the yoke 41 and the yoke 42, as shown in FIG. 2B, in the Y-axis direction, the innermost peripheral edge of the thin film coil 20 (the winding in the linear pattern 21 located on the innermost periphery). The center position CL of the winding center side surface position 21T1 and the outermost peripheral edge (side surface position on the winding outer peripheral side in the linear pattern 21 positioned on the outermost outer periphery) 21T2 is the winding outer peripheral yoke 42 of the thin film coil 20. It is desirable that the yoke 41 is closer to the winding center side of the thin film coil 20 than the yoke 41. This is because the intensity distribution of the induction magnetic field Hm extending to the first and second MR elements 31 and 32 is flattened (smallly biased) in the Y-axis direction. The same applies to the relationship between the yoke 43 and the yoke 44. In the above case, in the Y-axis direction, the winding-side yoke 41 may be positioned closer to the winding outer periphery than the side surface position 21T1 of the linear pattern 21 located on the innermost periphery. That is, as shown in FIG. 2B, the side surface position 41T1 on the winding center side of the yoke 41 may be positioned on the outer periphery side of the winding with respect to the side surface position 21T1 of the linear pattern 21 on the innermost periphery. The same applies to the yoke 43. Further, as shown in FIG. 2B, the winding outer periphery side yoke 42 has an end 42T1 on the winding center side that is more winding center than the side surface position 21T2 of the linear pattern 21 located on the outermost periphery. It is desirable to be on the side. The same applies to the yoke 44.

  Furthermore, in the yokes 41 to 44, each easy magnetization axis Me is oriented along the winding direction of the thin film coil 20 (here, the X-axis direction). Thereby, compared with the case where the easy magnetization axis Me is in another direction, the yokes 41 to 44 are easily magnetized by the induced magnetic field Hm from the thin film coil 20, and the induced magnetic field Hm is more efficiently converted into the first to fourth. The MR elements 31 to 34 are guided. In particular, since the yokes 41 to 44 extend such that the longitudinal direction thereof coincides with the winding direction of the thin film coil 20, the direction of the easy magnetization axis Me is stabilized by the shape magnetic anisotropy.

  Further, this magnetic coupler further includes a pair of permanent magnet layers 51 to 54 for applying a bias magnetic field in the direction along each easy magnetization axis Me to the yokes 41 to 44. Thereby, the remanent magnetization is reduced by moving the yokes 41 to 44 in the direction of making a single magnetic domain, and adverse effects due to the magnetic history (hysteresis) of the yokes 41 to 44 themselves are suppressed. The pair of permanent magnet layers 51 to 54 is desirably located on the second level L2 like the yokes 41 to 44, and is covered with the insulating layer 13 together with the yokes 41 to 44 and the first to fourth MR elements 31 to 34. (See FIG. 2B).

  In this magnetic coupler, as shown in FIG. 6, the first to fourth MR elements 31 to 34 are bridge-connected. Specifically, one ends of the first and third MR elements 31, 33 are connected at the first connection point P1, and one ends of the second and fourth MR elements 32, 34 are connected to the second connection point. The other end of the first MR element 31 and the other end of the fourth MR element 34 are connected at the third connection point P3, and the other end of the third MR element 33 is connected to the second MR element. The other end of the element 32 is connected at the fourth connection point P4. FIG. 6 shows a circuit configuration of the magnetic coupler according to the present embodiment.

  Hereinafter, a method for detecting the induced magnetic field Hm formed by the signal current Im will be described with reference to FIG.

In FIG. 6, first, a state where the induction magnetic field Hm is not applied is considered. Here, the resistance values of the first to fourth MR elements 31 to 34 when the read current i0 is passed through the bridge circuit are R1 to R4. Read current i0 from power supply Vcc is split into two, read current i1 and read current i2, at second connection point P2. After that, the read current i1 that has passed through the second MR element 32 and the third MR element 33 and the read current i2 that has passed through the fourth MR element 34 and the first MR element 31 are the first Join at the connection point P1. In this case, the potential difference V between the second connection point P2 and the first connection point P1 is
V = i1 * R2 + i1 * R3 = i2 * R4 + i2 * R1
= I1 * (R2 + R3) = i2 * (R4 + R1) (1)
It can be expressed as.
The potential V3 at the fourth connection point P4 and the potential V4 at the third connection point P3 are respectively
V2 = V−i1 × R2
V4 = V−i2 × R4
It can be expressed. Therefore, the potential difference V0 between the fourth connection point P4 and the third connection point P3 is
V0 = V4-V2
= (V-i2 * R4)-(V-i1 * R2)
= I1 * R2-i2 * R4 (2)
It becomes. Here, from the equations (1) and (2),
V0 = R2 / (R2 + R3) × V−R4 / (R4 + R1) × V
= {R2 / (R2 + R3) -R4 / (R4 + R1)} * V (3)
It becomes. In this bridge circuit, when an induction magnetic field Hm, which is an external magnetic field, is applied, the potential difference V0 between the fourth connection point P4 and the third connection point P3 expressed by the above equation (3) is measured. Thus, the resistance change amount is obtained. Here, when the induction magnetic field Hm is applied, the resistance values R1 to R4 are changed by the change amounts ΔR1 to ΔR4, that is, the resistance values R1 to R4 after the induction magnetic field Hm is applied are R1 = R1 + ΔR1
R2 = R2 + ΔR2
R3 = R3 + ΔR3
R4 = R4 + ΔR4
Assuming that, the potential difference V0 at the time of applying the induction magnetic field Hm is expressed by the following equation (3):
V0 = {(R2 + ΔR2) / (R2 + ΔR2 + R3 + ΔR3) − (R4 + ΔR4) / (R4 + ΔR4 + R1 + ΔR1)} × V (4)
It becomes. In this current sensor, the resistance values R1, R2 of the first and second MR elements 31, 32 and the resistance values R3, R4 of the third and fourth MR elements 33, 34 show changes in opposite directions. Thus, the variation ΔR4 and the variation ΔR1 cancel each other, and the variation ΔR3 and the variation ΔR2 cancel each other. For this reason, when comparing before and after application of the induction magnetic field Hm, there is almost no increase in the denominator in each term of Equation (4). On the other hand, for the numerator of each term, the change amount ΔR2 and the change amount ΔR4 always have opposite signs, so that an increase / decrease appears.

If all of the first to fourth MR elements 31 to 34 have completely the same characteristics, that is, R1 = R2 = R3 = R4 = R and ΔR1 = ΔR2 = −ΔR3 = − When ΔR4 = ΔR, the equation (4) is
V0 = {(R + ΔR) / (2 × R) − (R−ΔR) / (2 × R)} × V
= (ΔR / R) × V
It becomes.

  In this way, if the first to fourth MR elements 31 to 34 that are known with respect to characteristic values such as ΔR / R are used, the magnitude of the induced magnetic field Hm can be detected, and the induced magnetic field Hm. Can be estimated. That is, according to this magnetic coupler, the thin film coil 20 is connected to a certain electric circuit to flow the signal current Im, and the read current i0 is supplied to the bridge circuit composed of the first to fourth MR elements 31 to 34. Thus, the change in the signal current Im appears in the change in the read current i0. Therefore, signal transmission between a plurality of electric circuits insulated from each other can be performed without contact.

  In the magnetic coupler of the present embodiment, the plurality of band-like patterns 311 in the first MR element 31 are connected to each other by the connecting portion 312 at a position away from the edge in the extending direction of the first MR element 31 by a predetermined distance. The sense current i2 flowing through the first MR element 31 does not flow through the end portion 311Z of the strip pattern 311 (see FIG. 3A). Therefore, the sense current i2 is not affected by the disorder of the orientation of the magnetization J61 of the magnetization free layer 61 at the end 311Z of the band-shaped pattern 311, and the magnitude of the applied induced magnetic field Hm and the magnetization J61 of the magnetization free layer 61 The expression of hysteresis in the relationship is suppressed. Similar effects can be obtained for the second to fourth MR elements 32 to 34. As a result, it is possible to detect the induced magnetic field from the coil with higher sensitivity and higher accuracy than when the end portions of the band-like patterns 311, 321, 331, 341 are connected to each other.

  In the present embodiment, in particular, the distance L from the edge 311T in the extending direction of the belt-like pattern 311 is made larger than the width W, so that the magnetization free layer 61 of the end portion 311Z of the belt-like pattern 311 has The influence of the orientation disorder of the magnetization J61 can be reliably avoided.

  Further, both end surfaces 35 in the cross section in the width direction of the plurality of strip-shaped patterns 311 are inclined surfaces, and the connecting portion 312 is formed so as to cover the upper surface 36 and both end surfaces 35 of the strip-shaped pattern 311. The contact resistance with the pattern 311 can be reduced, and power saving can be achieved.

  Further, since the intermediate layer 13 including the plurality of insulating films 132 separated by the conductive film 131 is disposed between the thin film coil 20 and the first to fourth MR elements 31 to 34, the intermediate layer 13 Compared with the case where has a single layer structure, the withstand voltage can be improved. Therefore, even if the thickness of the entire intermediate layer 13 is reduced and the distance between the first to fourth MR elements 31 to 34 and the thin film coil 20 is made closer, it is possible to ensure a dielectric breakdown voltage equal to or higher than the conventional one. . As a result, the overall configuration can be made compact, and the power consumption during driving can be reduced because the induced magnetic field Hm can be accurately detected even when a smaller signal current Im flows through the thin film coil 20. Can also be realized.

  Further, in the magnetic coupler of the present embodiment, the yokes 41 to 44 made of a soft magnetic material are arranged on the winding center side of the thin film coil 20 and the first to fourth MR elements 31 to 34 in the in-plane direction. Since they are arranged on both sides of the outer periphery of the winding, the strength reduction of the induction magnetic field Hm generated from the thin film coil 20 is suppressed, and the induction magnetic field Hm is efficiently applied to the first to fourth MR elements 31 to 34. be able to. Therefore, the induced magnetic field Hm can be accurately detected even with a smaller signal current Im. Therefore, power saving can be achieved as compared with the conventional case. In particular, since the yokes 41 to 44 are arranged on the second level L2 in the same manner as the first to fourth MR elements 31 to 34, the induction magnetic field Hm is smaller than that in the case other than the second level L2. Thus, the first to fourth MR elements 31 to 34 are more efficiently reached.

  In the magnetic coupler of the present embodiment, the thin film coil 20 includes a plurality of linear patterns 21, and the first to fourth MR elements 31 to 34 are provided at positions corresponding to the linear regions R21 occupied by the thin film coils 21 in the stacking direction. Since it did in this way, compared with the case where it provided in the position corresponding to curve area | region R22 which the curve pattern 22 occupies, the stable detection operation is exhibited.

  In the magnetic coupler of the present embodiment, the center position CL between the innermost peripheral edge and the outermost peripheral edge of the thin film coil 20 in the radial direction of the thin film coil 20 is the yoke 42 on the winding outer peripheral side of the thin film coil 20. , 44 is closer to the yokes 41, 43 on the winding center side of the thin film coil 20, so that the induction magnetic field Hm with a small intensity distribution in the radial direction reaches the first to fourth MR elements 31 to 34. become. Therefore, in the strip-like patterns 311, 321, 331, and 341 extending in the radial direction of the thin film coil 20, the magnetization J61 of the magnetization free layer 61 is in a substantially constant direction according to the induction magnetic field Hm over all radial portions. More accurate signal transmission can be performed.

  Further, in the magnetic coupler of the present embodiment, the first to fourth MR elements 31 to 34 are used for the bridge connection, so that the change in the signal current Im flowing through the thin film coil 20 can be made with higher accuracy. Can be detected.

<Modification of the first embodiment>
In the above embodiment, the planar shape of the strip-shaped pattern 311 is rectangular, and the contour of the edge 311T in the extending direction is linear. However, as in the modification of the present embodiment shown in FIG. 7, if the contour of the edge 311T of the strip pattern 311 is curved, the extending direction in the magnetization free layer 61 at the end of the strip pattern 311 Generation of magnetization J61 (having magnetic domains) in a direction different from (Y-axis direction) is suppressed, and the orientation of magnetization J61 as a whole can be enhanced. As a result, compared with the case where the outline of the edge 311T is a straight line, the effective area that can be used when detecting the induced magnetic field Hm in the strip pattern 311 can be expanded, and the detection sensitivity can be increased.

[Second Embodiment]
Next, with reference to FIG. 8 and FIG. 9, the magnetic coupler as 2nd Embodiment in this invention is demonstrated. FIG. 8A shows the planar configuration of the main part (the periphery of the first MR element 31) of the magnetic coupler of the present embodiment, and corresponds to FIG. 2A of the first embodiment. To do. FIG. 8B is a cross-sectional view taken along the line VIIIB-VIIIB in FIG. 8A, and corresponds to FIG. 2B of the first embodiment. .

  In this magnetic coupler, unlike the magnetic coupler of the first embodiment, the band-like patterns 311, 321, 331, 341 included in the first to fourth MR elements 31 to 34 are not in the Y-axis direction but in the X-axis direction. It extends to. In the band-shaped patterns 311, 321, 331, and 341, as shown in FIG. 9, the magnetization J63 of the magnetization fixed layer 63 faces the + Y direction, and the magnetization J61 of the magnetization free layer 61 in the no-load state is in the −X direction. Suitable for FIG. 9 is an exploded perspective view showing the configuration of the belt-like patterns 311, 321, 331, 341 of the present embodiment.

  Also in the magnetic coupler of the present embodiment, the same effects as the first embodiment (effects such as higher sensitivity and higher accuracy) can be obtained. In particular, the presence of the yokes 41 to 44 not only increases the intensity of the induced magnetic field Hm that extends to each of the plurality of strip patterns 311, 321, 331, and 341, but also reduces the bias. , 341, the variation in resistance value is reduced. Therefore, more accurate signal transmission can be performed.

  Although the present invention has been described with reference to some embodiments, the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, an example in which four magnetoresistive elements are provided has been described, but the number is not particularly limited.

  In the above embodiment, the case where the plurality of strip patterns 311, 321, 331, 341 are connected in series is described. However, for example, as shown in FIG. May be.

  In the above-described embodiment, the intermediate layer is disposed so as to completely separate the first layer in which the thin film coil exists and the second layer in which the MR element is located. However, the present invention is not limited to this. It is not a thing. That is, the intermediate layer only needs to extend along the first and second layers so as to occupy at least the overlapping region of the thin film coil and the MR element in the thickness direction. It may be divided and arranged in these areas.

  In the above-described embodiment and the like, for example, as shown in FIG. 2B, the first layer, the intermediate layer, and the second layer are sequentially stacked from the base side. The stacking order is not limited to this. That is, you may make it laminate | stack a 2nd hierarchy from the base | substrate 10 side, an intermediate | middle layer, and the 1st hierarchy L1 in order.

  The magnetic coupler of the present invention enables signal transmission while performing electrical insulation between input and output and noise shielding, and can be used as, for example, a communication signal isolator. Specifically, for example, use as a component that transmits an electrical signal in an electrically insulated state between a primary side and a secondary side in a switching power supply is conceivable. As this signal isolator for communication, a photocoupler and a pulse transformer are conventionally used. However, the magnetic coupler of the present invention has excellent responsiveness (low signal transmission delay), a wide usable temperature range, and a secular change. Since it has advantages such as being small, it can be expected to be used as a substitute for them.

It is a top view showing the structure of the magnetic coupler as 1st Embodiment in this invention. FIG. 2 is an enlarged plan view and cross-sectional view of a main part of the magnetic coupler shown in FIG. 1. FIG. 3 is a plan view and a cross-sectional view illustrating a detailed configuration of the magnetoresistive effect element illustrated in FIG. 2. It is a disassembled perspective view showing the detailed structure of the strip | belt-shaped pattern in the magnetoresistive effect element shown in FIG. FIG. 2 is a cross-sectional view illustrating a detailed configuration of an intermediate layer in the magnetic coupler illustrated in FIG. 1. It is a circuit diagram in the magnetic coupler shown in FIG. It is a conceptual diagram for demonstrating the magnetic domain structure in the strip | belt-shaped pattern as a modification of the magnetoresistive effect element shown in FIG. It is the top view and sectional drawing showing the principal part structure of the magnetic coupler as 2nd Embodiment in this invention. It is a disassembled perspective view showing the structure of the strip | belt-shaped pattern in the magnetic coupler shown in FIG. The top view showing the structure of the magnetoresistive effect element as a modification in the magnetic coupler shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Base | substrate, 11, 12, 14 ... Insulating layer, 13 ... Intermediate | middle layer, 20 ... Thin film coil, 20S, 20E ... Terminal, R21 ... Linear area | region, 21 ... Linear pattern, R22 ... Curve area | region, 22 ... Curve pattern, 31 34 ... First to fourth magnetoresistive effect elements 35 ... End face 36 ... Upper surface 311, 321, 331, 341 ... Strip pattern, 312 ... Connection part 41-44 ... Yoke 51-54 ... Permanent magnet Layer 61, magnetization free layer, 62 intermediate layer, 63 magnetization fixed layer, 64 antiferromagnetic layer, J61, J63 magnetization.

Claims (7)

A coil, a magnetoresistive effect element that detects an induced magnetic field generated by a current flowing through the coil, and a pair of yokes;
The magnetoresistive effect element has a plurality of sub-elements extending in a strip shape and connected to each other by a connecting portion at a predetermined distance from an edge in the extending direction of the magnetoresistive effect element
The plurality of sub-elements are arranged at positions corresponding to the linear regions of the coil in the stacking direction,
One yoke of the pair of yokes arranged in the stacking direction parallel to the linear pattern of the coil on the winding center side of the coil is stacked parallel to the linear pattern of the coil on the winding outer periphery side of the coil It is located in the innermost circumference which is the innermost circumference edge of the coil arranged in the lamination direction in parallel with one yoke of the pair of yokes rather than the other yoke of the pair of yokes arranged in the direction. wound periphery in the linear pattern located on the outermost periphery, which is the outermost edge of the coil disposed on the other yoke and parallel to the stacking direction of the winding center side of the side position location and the pair of yokes in the linear pattern By being provided near the first central position located between the side surface position on the side ,
A second center position located between a side position on the winding center side of one yoke of the pair of yokes and a side position on the winding outer periphery side of the other yoke of the pair of yokes is the first position. A magnetic coupler, wherein the magnetic coupler is located closer to the outer periphery of the coil than the center position of the coil .   The magnetic coupler according to claim 1, wherein the plurality of sub-elements are connected to each other in series or in parallel.   The magnetic coupler according to claim 1, wherein the connecting portion is made of a nonmagnetic conductor. The plurality of sub-elements are inclined at both end faces in the width direction perpendicular to the extending direction of the sub-element,
The connecting portion extends in the width direction of the sub-element, and is formed so as to cover the upper surface and the both end faces of the sub-element. The magnetic coupler according to item 1. 5. The magnetic coupler according to claim 1, wherein a predetermined distance from an end edge in the extending direction of the sub-element is larger than a width of the sub-element.   The magnetic coupler according to claim 1, wherein the sub-element is a stacked body having a spin valve structure.   7. The magnetic coupler according to claim 1, wherein an edge of the sub-element in an extending direction has a curved outline.

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