JP2008275470A - Field probe, field detection apparatus, and method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field probe and a field detection apparatus capable of highly accurately detecting prescribed magnetic fields or near magnetic fields, low-frequency magnetic fields extremely close to the prescribed magnetic fields, with high detection accuracy and provide a field detection method using them. <P>SOLUTION: The magnetic probe 10 is provided with a power terminal 13 electrically connected to a power supply part 21 which supplies power for a field detection circuit 15; a main body part 11 having an output terminal 12 electrically connected to a signal processing part which processes output signals of the field detection circuit 15; and a probe part 14. The probe part 14 has the field detection circuit 15; a positive wiring 17a and a negative wiring 17b of a power wiring; and a positive wiring 16a and a negative wiring 16b of an output wiring. The field detection circuit 15 is a full-bridge circuit comprising magnetoresistive elements 15a-15d of which resistance values vary according to applied magnetic fields. The full-bridge circuits are formed through semiconductor processes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic field probe for detecting a near magnetic field, a magnetic field detection device, and a magnetic field detection method using them, for example, for measuring noise generation distribution and current distribution on a printed circuit board in which an electronic circuit is built.

  Conventionally, as a magnetic field probe and a magnetic field detection apparatus of this type and a magnetic field detection method using them, for example, a technique described in Patent Document 1 is known. In the magnetic field probe described in Patent Document 1, a loop coil layer formed with a loop coil for detecting a near magnetic field generated by a detection target and both sides of the loop layer are formed to shield external electromagnetic noise. The shield layer has a substrate that is sequentially stacked. The shield layer is provided with a window opening so that a near magnetic field (magnetic flux) passes through the loop coil formed in the loop coil layer. With such a structure, for example, a near magnetic field generated from an electronic component or a circuit pattern included in the printed circuit board is detected.

  By the way, when trying to detect a constant (direct current) magnetic field or a low-frequency magnetic field very close to the constant magnetic field using such a magnetic field probe, there are the following problems in principle. That is, in the above magnetic field probe, in the principle that an induced electromotive force is generated by a near magnetic field passing through a loop coil formed in the loop coil layer, and the near magnetic field is detected based on the induced electromotive force, the near magnetic field has a low frequency. Since the induced electromotive force generated in the loop coil is small when it is a magnetic field, it is difficult to detect a near magnetic field with high accuracy. In addition, when the near magnetic field is a constant magnetic field, no induced electromotive force is generated in the loop coil, so that the near magnetic field cannot be detected.

In this regard, for example, the technique described in Patent Document 2 is known. In the technique described in Patent Document 2, the loop coil layer is thinned, and a part of the thin film loop coil is configured by a magnetoresistive element. That is, the magnetoresistive element is connected in series with the thin film loop coil. As a result, when the near magnetic field generated by the electronic component or circuit pattern included in the printed circuit board is a high frequency magnetic field, the near magnetic field is detected by the thin film loop coil. I try to detect it.
JP-A-8-248080 JP 2001-289839 A

  As described above, according to the technique described in the above-mentioned Patent Document 2, the problem in principle that occurs in the technique described in the above-mentioned Patent Document 1 is certainly eliminated. However, since the magnetic field probe described in Patent Document 2 detects a constant magnetic field or a near magnetic field very close to the constant magnetic field using a single magnetoresistive element, the detection accuracy is not so high. It is required to detect such a near magnetic field with higher accuracy, and there is still room for improvement.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic field probe and a magnetic field capable of detecting a fixed magnetic field or a near magnetic field that is a low frequency magnetic field very close to the constant magnetic field with higher detection accuracy. An object of the present invention is to provide a detection apparatus and a magnetic field detection method using them.

  In order to achieve such an object, in the invention described in claim 1, a power supply terminal electrically connected to a power supply unit that supplies power to a magnetic field detection circuit that detects a magnetic field generated by a detection target including an electronic circuit, A main body having an output terminal electrically connected to a signal processing section for processing an output signal of the magnetic field detection circuit; the magnetic field detection circuit; and for electrically connecting the magnetic field detection circuit to the power supply terminal. And a probe section having an output signal line for electrically connecting the magnetic field detection circuit to the output terminal, the magnetic field detection circuit being brought close to the detection target, and the detection target As a magnetic field probe for detecting a generated magnetic field, the magnetic field detection circuit is a bridge circuit including a magnetoresistive element whose resistance value changes in accordance with an applied magnetic field. It was that it is formed through the nest.

  In such a configuration as a magnetic field probe, a magnetic field detection circuit for detecting a near magnetic field is configured by a bridge circuit including a magnetoresistive element. For this reason, it is possible to detect a constant magnetic field or a low-frequency magnetic field with higher detection accuracy as compared with the conventional technique of detecting with a single magnetoresistive element. In the above configuration, since the magnetic field detection circuit is formed through the semiconductor process, the physique is minimal, and the source of the near magnetic field applied to the magnetic field detection circuit exists only in a narrow range. Therefore, a constant magnetic field or a low frequency magnetic field can be detected with high spatial resolution.

  Further, in the configuration according to the first aspect, as in the second aspect, for example, the bridge circuit is formed in a size of about 5 to 10 micrometers square or even in a minimal region. It is desirable. When the magnetic field detection circuit (bridge circuit) having the above configuration is brought close to the detection target, since the physique is very small, substantially the same near magnetic field generated from the detection target is applied to the components of the magnetic field detection circuit including the magnetoresistive element. Will be able to. In addition, since the separation distance between the components of the magnetic field detection circuit is extremely short, not only the proximity magnetic field but also the environment where these components are placed, such as temperature, can be made substantially the same. Become.

  By the way, as a factor which changes the resistance value of a magnetoresistive element, not only the applied magnetic field but the environment where the said magnetoresistive element is placed, for example, temperature is mentioned. Therefore, even if the applied magnetic field is the same, if the temperature of the magnetoresistive element is different, the resistance value is greatly different, and it is difficult to detect the near magnetic field with high accuracy.

  In that respect, in the configuration according to claim 1 or 2, in the invention according to claim 3, for example, the bridge circuit includes two magnetoresistive elements having the same magnetic field dependency and temperature characteristics connected in series. One of the two magnetoresistive elements constituting the half bridge circuit is covered with a magnetic material and is provided with a magnetic shield that is protected from external magnetic noise. The other magnetoresistive element is not magnetically shielded.

  In such a configuration as a magnetic field probe, two magnetoresistive elements constituting the magnetic field detection circuit (half-bridge circuit) are connected in series and have the same temperature characteristics. Therefore, for example, if the near magnetic field does not change and the temperature at which it is placed changes, the two magnetoresistive elements change their resistance values in exactly the same manner, so the midpoint potential of the half bridge does not deviate from the equilibrium state. (Does not change). That is, the temperature characteristic of the magnetoresistive element can be canceled out. However, when the near magnetic field changes, the resistance value of one magnetoresistive element that is not magnetically shielded changes due to the near magnetic field, while the other magnetoresistive element that is magnetically shielded has a resistance value due to the near magnetic field. Does not change. For this reason, the midpoint potential of the half-bridge circuit is deviated from the equilibrium state by the near magnetic field, and the near magnetic field can be detected based on the fluctuation amount from the equilibrium state. Therefore, according to the above configuration, a near magnetic field can be detected with high accuracy and high spatial resolution regardless of the environment (temperature) in which the magnetic field probe is placed.

  In the configuration described in claim 1 or 2, as in the invention described in claim 4, for example, in the bridge circuit, two magnetoresistive elements having the same magnetic field dependency and temperature characteristics are connected in series. The two half-bridge circuits are a full-bridge circuit that is symmetrically connected in parallel, and one of the four magnetoresistive elements constituting the full-bridge circuit is located at a position that defines a balance condition. The magnetoresistive element may be covered with a magnetic material to provide a magnetic shield that is protected from external magnetic noise, and the other set of magnetoresistive elements may not be provided with a magnetic shield.

  With such a configuration as the magnetic field probe, an effect according to the configuration described in claim 3 can be obtained. However, since the herb bridge circuits are symmetrically connected in parallel, the amount of change from the equilibrium state of the midpoint potential of these herb bridge circuits is larger than that of the configuration described in claim 3. Therefore, the near magnetic field can be detected with higher accuracy based on the fluctuation amount of the midpoint potential.

  As such a probe unit, for example, as in the invention described in claim 5, the probe unit has a plate-like substrate, the bridge circuit is configured by an IC package, and the plate-like substrate is provided. It is good also as arrange | positioning at one bottom face. Alternatively, for example, as in the invention described in claim 6, the probe section has a plate-like substrate, and the bridge circuit is formed of a thin film on one bottom surface of the plate-like substrate. It is good. Incidentally, according to the configuration described in claim 5, since a general IC package technology can be used, it is easy to manufacture a magnetic field probe. Further, according to the configuration of the sixth aspect, since the magnetic field detection circuit, and thus the probe part can be further reduced in size, it can be brought closer to the detection target, with higher accuracy and higher spatial resolution. The near magnetic field can be detected.

  By the way, in the magnetic field probe described in Patent Document 2 described in the “Problems” section, a part of the thin film loop coil is constituted by a magnetoresistive element, and current is applied to the magnetoresistive element through the thin film loop coil. Such a wiring to the magnetoresistive element, that is, a thin film loop coil, may function as an electric field antenna when the near magnetic field is a constant magnetic field or a low frequency magnetic field. When the wiring to the magnetoresistive element functions as an electric field antenna, the electric field detected by the electric field antenna becomes electric field noise, which adversely affects the detection accuracy of the near magnetic field. In particular, when adopting a conventional structure in which a loop coil and a magnetoresistive element are integrated, it is difficult to provide an electric field shield for the loop coil in order to maintain the function of detecting a high-frequency magnetic field. It is difficult to eliminate completely.

  In that respect, in the configuration according to any one of the first to sixth aspects, the power supply line and the output signal line are nonmagnetic and conductive, for example, as in the invention according to the seventh aspect. It is desirable that each of the electric field shields including a metal layer made of a metal material having the above is provided and protected from external electric field noise. Alternatively, for example, as in the invention described in claim 8, the power supply line and the output signal line are collectively non-magnetic and include electric field shields including a metal layer made of a conductive metal material. It is desirable to be protected from external electric field noise. As a result, it is possible to suppress the power supply line and the output signal line from functioning as an electric field antenna due to a near magnetic field or an external magnetic field, thereby suppressing the occurrence of electric field noise. Therefore, the near magnetic field can be detected with high accuracy. Particularly, in the configuration according to the eighth aspect, since the electric field shield is collectively applied to the power supply line and the output signal line, the number of steps for manufacturing the magnetic field probe can be reduced.

  Similarly, in the configuration according to claim 7 or 8, as in the invention according to claim 9, for example, the magnetic field detection circuit is a metal layer made of a nonmagnetic material and a conductive metal material. It is desirable that an electric field shield including be provided and be protected from external electric field noise.

  As such an electric field shield, for example, as in the invention according to claim 10, an insulating layer that electrically insulates the power supply line and the output signal line from the metal layer, the metal layer, and an internal It is desirable to be composed of three layers with a protective film for protecting the film. As a result, the power supply line and the output signal line can be reliably insulated from the metal layer functioning as an electric field shield, and the inside can be protected.

  When, for example, an external power supply is used as a power supply unit for driving the magnetic field detection circuit, the voltage generated by the external power supply may slightly fluctuate or external electromagnetic noise may be superimposed. Further, the power supply path functions as an electric field antenna, and electric field noise may occur in the power supply path. The near magnetic field generated by the detection target is very small. If such a slight voltage fluctuation or electromagnetic noise superimposition occurs, the detection accuracy of the near magnetic field may be lowered.

  In this regard, for example, as in the invention described in claim 12, it is particularly desirable to employ a battery mounted on the main body. In the battery, since the drive voltage of the electric field detection circuit is chemically generated, there is almost no slight change in the drive voltage. In addition, since the power supply path can be shortened, it is possible to suppress external electromagnetic noise from being superimposed on the generated drive voltage or function as an electric field antenna to generate electric field noise. However, if there is no such fear, an external power supply outside the magnetic field probe may be employed as in the invention described in claim 11, for example.

  On the other hand, in order to achieve the above object, according to a thirteenth aspect of the present invention, the magnetic field detection circuit includes the magnetic field probe according to any one of the first to eleventh aspects and a power supply terminal included in the magnetic field probe. A power supply unit that supplies power to the magnetic field probe, a signal processing unit that processes an output signal of the magnetic field detection circuit that is output via the output terminal of the magnetic field probe, and the magnetic field probe that is in proximity to the detection target And a scanning unit that scans the detection target with the magnetic field probe. Alternatively, in the invention according to claim 14, the magnetic field probe according to claim 12, and a signal processing unit that processes an output signal of the magnetic field detection circuit output via the output terminal of the magnetic field probe, The holding means for holding the magnetic field probe in the vicinity of the detection target and the scanning means for scanning the detection target with the magnetic field probe are provided. Even with such a configuration as the magnetic field detection device, an effect according to the configuration of the first aspect can be obtained. That is, a near magnetic field that is a constant magnetic field or a low frequency magnetic field very close to the constant magnetic field can be detected with higher detection accuracy and spatial resolution.

  In such a configuration, for example, as in the invention described in claim 15, the holding unit holds the detection target and the magnetic field detection circuit so as to be horizontally opposed to each other, and the scanning unit places the detection target. In addition, if it is an XY stage that is capable of planar movement together with the placed detection target, the magnetic field distribution at a position separated from the detection target by a predetermined distance through the cooperation of the holding means and the XY stage. Can be detected.

  Similarly, for example, as in the invention described in claim 16, the holding unit holds the detection target and the magnetic field detection circuit so as to be horizontally opposed to each other, and the scanning unit places the detection target. In addition, if it is a three-dimensional stage that can move three-dimensionally together with the placed detection target, the three-dimensional magnetic field distribution at a position separated from the detection target is detected through the cooperation of the holding means and the three-dimensional stage. Will be able to.

  For example, as in the invention described in claim 17, the signal processing unit may map the magnetic field intensity generated by the detection target based on the output signal.

  If the magnetic field probe according to any one of claims 1 to 12 or the magnetic field detection device according to any one of claims 13 to 17 is used, the detection target is emitted as in the invention according to claim 18. It becomes possible to detect the DC component of the magnetic field.

  Hereinafter, an embodiment of a magnetic field probe, a magnetic field detection device, and a magnetic field detection method using these according to the present invention will be described with reference to FIGS. As shown in FIGS. 1 to 4 and as described in detail below, in this embodiment, a magnetic field detection circuit is used as a bridge circuit including a magnetoresistive element that changes to a resistance value according to an applied magnetic field. In addition to forming the bridge circuit through a semiconductor process, a near magnetic field, which is a constant magnetic field or a low frequency magnetic field very close to the constant magnetic field, is detected with higher detection accuracy and higher spatial resolution.

  FIG. 1 is a schematic diagram showing an example of a circuit configuration centering on a magnetic field detection circuit constituting the magnetic field probe and the magnetic field detection device. FIG. 2 is a diagram showing an external appearance of the magnetic field probe according to the present embodiment from the perspective direction, and FIG. 3 is a perspective view of the internal structure of the magnetic field probe according to the present embodiment from the perspective direction. First, the configuration and function of the magnetic field probe according to the present embodiment will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the magnetic field probe 10 basically includes a main body 11 formed of a printed circuit board having a substantially square shape in plan view, and a plane long in the vertical direction of FIGS. And a probe portion 14 formed of a printed circuit board having a substantially rectangular (prism) shape.

  Of these, the body portion 11 having a substantially square shape in plan view has a coaxial connector output terminal (hereinafter simply referred to as an output terminal) 12 at its substantially central portion, as shown in FIGS. A DC power supply terminal (hereinafter simply referred to as a power supply terminal) 13 is provided at the periphery. Although not shown in FIGS. 1 to 3, the output terminal 12 includes a plus terminal and a minus terminal. The positive terminal and the negative terminal of the output terminal 12 are coaxial cables 30 (electrically connecting the magnetic field probe 10 (more precisely, a magnetic field detection circuit 15 described later) and a signal processing unit 31 (refer to FIG. 4) described later. It is configured to be connected to the core wire and the shield wire that constitute (see FIG. 4). Similarly, although not shown in FIGS. 1 to 3, the power supply terminal 13 is also composed of a plus terminal and a minus terminal. The positive terminal and the negative terminal of the power terminal 13 are positive wirings of the power cable 20 that connects the magnetic field probe 10 (more precisely, the magnetic field detection circuit 15) and a power supply unit 21 (see FIGS. 1 and 4) described later. And a negative wiring.

  On the other hand, as shown in FIGS. 2 and 3, the probe unit 14 has a magnetic field detection circuit 15 configured as an IC package through a semiconductor process at the end opposite to the power supply terminal 13. The magnetic field detection circuit 15 will be described later with reference to FIG. Further, on the front surface and the back surface of the probe portion 14, a positive wiring 16a and a negative wiring 16b as output wirings for transmitting the output signal of the magnetic field detection circuit 15 are formed of, for example, copper foil (however, FIG. 2). Then, only the plus wiring 16a is shown). Similarly, on the front surface and the back surface of the probe portion 14, a positive wiring 17a and a negative wiring 17b for supplying a DC power to the magnetic field detection circuit 15 are formed of, for example, copper foil (however, in FIG. 2). Only the positive wiring 17a is shown). The positive wiring 16a and the negative wiring 16b of the output wiring are electrically connected to the positive terminal and the negative terminal of the output terminal 12, respectively. Similarly, the positive wiring 17a and the negative wiring 17b of the power supply wiring are electrically connected to the positive terminal and the negative terminal of the power supply terminal 13, respectively. The positive terminal and the negative terminal of the output terminal 12, the positive terminal and the negative terminal of the power terminal 13, the positive wiring 16a and the negative wiring 16b of the output wiring, and the positive wiring 17a and the negative wiring 17b of the power wiring are printed. The substrate is integrally formed.

  Due to the above configuration, a predetermined DC power is supplied from the power supply unit 21 to the magnetic field detection circuit 15 through the following power supply path. That is, the power supply path is “power supply unit 21 (see FIG. 1) → power cable 20 (plus wiring) → power supply terminal 13 (plus terminal) → plus wiring 17a of power supply wiring → magnetic resistance element 15a, magnetoresistance element 15c. → Magnetic resistance element 15d, magnetoresistive element 15b → negative wiring 17b of power supply wiring → power supply terminal 13 (minus terminal) → power supply cable 20 (negative wiring) → power supply path 21 ”. When the DC power is supplied in this way, the magnetic field detection circuit 15 is driven to detect the applied magnetic field.

  When the DC power is supplied in this way and the magnetic field detection circuit 15 is driven, the output signal (the midpoint potential of each half bridge circuit) is sent from the magnetic field detection circuit 15 to the signal processing unit 31 through the following output signal transmission path. Is output. That is, the output signal transmission path is “middle point of magnetoresistive elements 15a and 15d → plus wiring 16a of output wiring → output terminal 12 (plus terminal) → coaxial cable 30 → signal processing unit 31 (see FIG. 4)” and “ The middle point of the magnetoresistive elements 15c and 15b → the negative wiring 16b of the output wiring → the output terminal 12 (minus terminal) → the coaxial cable 30 → the signal processing unit 31 ”. Incidentally, in the signal processing unit 31 to be described later, the applied magnetic field is detected based on the difference in the midpoint potential of each half bridge circuit.

  By the way, the magnetic field probe 10 of the present embodiment is very close to the detection target in order to detect the magnetic field generated by the detection target 100 (see FIG. 3) including the electronic circuit. When the magnetic field probe 10 is close to the detection target 100, the detection target 100 generates not only a magnetic field but also an electric field. Therefore, the power supply path and the output signal transmission path (in particular, the positive wiring 16 a and the negative wiring 16 b of the output wiring and the power wiring) The positive wiring 17a and the negative wiring 17b) may function as an electric field antenna for detecting such an electric field. When functioning as an electric field antenna, electric field noise is superimposed on a DC power supply supplied to the magnetic field detection circuit 15 and an output signal of the magnetic field detection circuit 15, which causes a decrease in detection accuracy of the magnetic field detected by the magnetic field detection circuit 15.

  In that respect, the magnetic field probe 10 of the present embodiment includes an electric field shield 18, and the electric field shield 18 includes, as shown in FIGS. 1 and 2, the positive wiring 16 a and the negative wiring 16 b of the output wiring, and the power supply wiring. The positive wiring 17a, the negative wiring 17b, and the magnetic field detection circuit 15 are also provided so as to cover all at once.

  Specifically, the electric field shield 18 has a three-layer structure in which an insulating layer, a metal layer, and a protective layer are sequentially stacked from the inside. Of these, the insulating layer is made of, for example, epoxy resin, and the positive wiring 16a and the negative wiring 16b of the output wiring, the positive wiring 17a and the negative wiring 17b of the power supply wiring, and a metal layer to be described later are electrically connected. It is provided to ensure electrical insulation so as not to cause a short circuit. Here, the material for forming such an insulating layer is not limited to an epoxy resin as long as it can secure electrical insulation between the wiring and the metal layer and can be easily processed. It is. Note that the insulating layer is set to a thickness that can ensure electrical insulation between the wiring and the metal layer. Further, the metal layer is made of, for example, copper or aluminum as a nonmagnetic material and conductive metal material. As such a forming method, various methods such as applying a powder on the surface of the insulating layer, spraying, or attaching a thin film can be employed. Note that such a metal layer is short-circuited to the housing GND. The protective layer is formed of, for example, acrylic lacquer or the like in order to protect the insulating layer and the metal layer from external impacts.

  As described above, the power supply path and the output signal transmission path are covered with the electric field shield 18 and are protected from the external electric field noise, so that they do not function as an electric field antenna. A near magnetic field can be detected with high accuracy.

  On the other hand, as shown in FIG. 1, the magnetic field detection circuit 15 is a bridge circuit including a magnetoresistive element that changes to a resistance value corresponding to the applied magnetic field. Specifically, the magnetic field detection circuit 15 is a full-bridge circuit composed of four magnetoresistive elements 15a to 15d having the same magnetic field dependency and temperature characteristics. Specifically, in the magnetic field detection circuit 15, a half bridge circuit in which two magnetoresistive elements 15a and 15d are connected in series and a half bridge circuit in which two magnetoresistive elements 15c and 15b are connected in series are parallel. It is connected. Here, among the magnetoresistive elements 15a to 15d, one set of the magnetoresistive elements 15a and 15b located at the position where the equilibrium condition is determined is covered with a magnetic material to be protected from external magnetic noise. And the other set of magnetoresistive elements 15d and 15c are not magnetically shielded (is in a magnetically active state). In this way, the two half bridge circuits are symmetrically connected in parallel. Incidentally, the magnetosensitive axis where the detection circuit of the magnetic field detection circuit 15 is highest is in the plane where the magnetoresistive elements 15a and 15b exist as shown in FIG. 3, and the magnetoresistive elements 15a and 15b The vertical direction.

  When the magnetic field applied to the magnetic field detection circuit 15 configured as described above is a constant (DC) magnetic field or a low frequency magnetic field very close to the constant magnetic field, the resistance values of the magnetically active magnetoresistive elements 15c and 15d are: The value changes according to the magnetic field. On the other hand, since the resistance values of the magnetoresistive elements 15a and 15b to which the magnetic shield is applied are protected from external magnetic noise, they do not change as they are when the constant magnetic field or the like is not applied. Accordingly, the midpoint potential of the half bridge circuit composed of the magnetoresistive elements 15a and 15d and the midpoint potential of the half bridge circuit composed of the magnetoresistive elements 15c and 15b are symmetrically connected in parallel. For this reason, the same width varies in opposite directions (high and low) according to the constant magnetic field and the like. Therefore, in the full bridge circuit, the fluctuation range of the midpoint potential can be amplified twice as compared with the half bridge circuit, so that a constant magnetic field applied to the magnetic field detection circuit 15 can be detected with higher accuracy. Will be able to. However, even with a half-bridge circuit, it is possible to detect a constant magnetic field or the like applied to the magnetic field detection circuit 15 with higher accuracy than in the conventional technique using only one magnetoresistive element.

  However, it is known that the resistance values of the magnetoresistive elements 15a to 15d change depending not only on the applied constant magnetic field or the like but also on the environment in which the magnetoresistive element is placed, for example, temperature. Therefore, when the temperature of the magnetoresistive elements 15a to 15d changes, even if the constant magnetic field applied is the same, the resistance values of the magnetoresistive elements 15a to 15d change, and each half bridge circuit It seems that the midpoint potential fluctuates and erroneous detection of a constant magnetic field applied to the magnetic field detection circuit 15 is caused.

  However, in the magnetic field probe 10, all of the magnetoresistive elements 15a to 15d constituting the magnetic field detection circuit 15 have the same magnetic field dependency and temperature characteristics. Therefore, for example, when the applied magnetic field remains unchanged and the temperature at which it is placed changes, the magnetoresistive elements 15a to 15d change their resistance values in exactly the same manner, and the midpoint potential of each half bridge circuit is It will not fluctuate. In other words, the influence of the temperature at which the magnetic field detection circuit 15 is placed does not appear in the output signal of the magnetic field detection circuit 15. Therefore, the temperature characteristics of the magnetoresistive elements 15a to 15d can be canceled out.

  Further, as described above, the magnetic field detection circuit 15 is configured by an IC package formed through a semiconductor process. Since such a magnetic field detection circuit 15 is small in size, the source of the magnetic field applied to the magnetoresistive elements 15a to 15d exists only in a narrow range. Therefore, a constant magnetic field or a low frequency magnetic field can be detected with high spatial resolution.

  As shown in FIG. 1 and FIG. 2 or as described above, the magnetic field detection circuit 15 is also provided with the electric field shield 18. As a result, the electric field generated by the detection target is shielded by the metal layer that constitutes the electric field shield 18 and flows to the housing GND to which the metal layer is connected, so that it reaches the inside of the magnetic field detection circuit 15. There is no. On the other hand, since the magnetic field generated by the detection target is formed of a non-magnetic material, it passes through the magnetic field detection circuit 15 without being shielded by the metal layer constituting the electric field shield 18. In this way, only the near magnetic field passing through the magnetic field detection circuit 15 can be detected while shielding the electric field noise.

  Next, a magnetic field detection apparatus 1 including the magnetic field probe 10 described above as a component, and a magnetic field detection method for mapping the intensity distribution of a magnetic field generated in the vicinity of a detection target using the magnetic field detection apparatus 1 will be described. This will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of the entire configuration of the magnetic field detection apparatus 1 including the magnetic field probe 10 shown in FIGS. 1 to 3 as a component. In the following description, the overlapping description about the matter demonstrated with reference to previous FIGS. 1-3 is omitted.

  First, as shown in FIG. 4, the magnetic field detection device 1 supplies a DC power supply to the magnetic field detection circuit 15 via the magnetic field probe 10 described with reference to FIGS. 1 to 3, the power supply terminal 13, and the power supply cable 20. And a signal processing unit 31 for processing the output signal of the magnetic field detection circuit 15 output via the output terminal 12 and the coaxial cable 30.

  Here, the signal processing unit 31 includes an isolation amplifier 32, a preamplifier 33, and a spectrum analyzer 34. As described above, the magnetic field detection circuit 15 is configured by a full bridge circuit, and the midpoint potential of the two half bridge circuits constituting the full bridge circuit passes through the output terminal 12 and the coaxial cable 30. Thus, the output signal of the magnetic field detection circuit 15 is input to the isolation amplifier 32. The isolation amplifier 32 calculates the difference between the captured midpoint potentials, amplifies the difference, and outputs it to the preamplifier 33 connected to the subsequent stage. The preamplifier 33 adjusts the input signal so that it can be analyzed by the spectrum analyzer 34 connected at the subsequent stage, and outputs the adjusted signal to the spectrum analyzer 34. Note that the spectrum analyzer 34 is a generally known detection device, and therefore a detailed description thereof is omitted here. As described above, the output signal of the magnetic field detection circuit 15 is processed by the isolation amplifier 32 and the preamplifier 33, whereby a constant magnetic field or a low frequency magnetic field very close to the constant magnetic field is detected through the spectrum analyzer 34. .

  Further, the magnetic field detection device 1 includes a holding unit (not shown). As described above, the magnetic field probe 10 includes the magnetic field detection circuit 15 at the lower end thereof. However, the holding unit has a predetermined distance between the magnetic field detection circuit 15 and the detection target component 100a and the detection target substrate 100b. The magnetic field detection circuit 15 is held so as to be close to each other and horizontally face each other. The holding means holds the magnetic field detection circuit 15 so that the magnetic sensitive axis of the magnetic field detection circuit 15 and a scanning direction described later are parallel to each other.

  Further, the magnetic field detection device 1 includes an XY stage (scanning means) (not shown). The XY stage can place the detection target component 100a and the detection target substrate 100b on the stage, and can move in a plane (horizontal movement) together with the detection target component 100a and the detection target substrate 100b. Accordingly, the XY stage moves in a plane as indicated by an arrow in FIG. 4 as the scanning direction, whereby the strength of the near magnetic field of the detection target component 100a and the detection target substrate 100b can be measured and mapped. It becomes like this.

  Note that the magnetic field probe, the magnetic field detection device, and the magnetic field detection method using these according to the present invention are not limited to those exemplified in the above embodiment, and can be executed as appropriate, for example, as the following form. .

  In the magnetic field detection apparatus 1 of the above-described embodiment, the isolation amplifier 32, the preamplifier 33, and the spectrum analyzer 34 are employed as the components of the signal processing unit 31, and the strength of the near magnetic field is measured and mapped. In addition, for example, a multimeter, an oscilloscope, or the like can be used instead of the spectrum analyzer 34 or in addition to the spectrum analyzer 34.

  In the magnetic field detection apparatus 1 (including the modified example) of the above-described embodiment, an XY stage capable of plane movement is employed as the scanning unit. However, for example, a three-dimensional stage capable of three-dimensional movement is employed. Also good. The strength distribution (map) of the near magnetic field obtained in the above embodiment shows the strength of the near magnetic field when the detection target component 100a and the detection target substrate 100b and the magnetic field detection circuit 15 are close to each other at a constant separation distance (height). Distribution. That is, the intensity distribution (two-dimensional map) of the near magnetic field can be obtained at a constant separation distance (height). However, in such a modified example, the separation distance (height) between the detection target component 100a and the detection target substrate 100b and the magnetic field detection circuit 15 can be variably set, and thus various separation distances (heights). The intensity distribution of the near magnetic field can be obtained. That is, a three-dimensional map of the near magnetic field can be obtained.

  In the magnetic field detection device 1 (including the modification) of the above embodiment, the magnetic field probe 10 is merely held by the holding unit, and the scanning unit performs a planar motion or a three-dimensional motion, so that the intensity distribution of the near magnetic field is obtained. Was obtained. In addition, for example, the scanning unit may simply place the detection target component 100a and the detection target substrate 100b on the stage, and the holding unit may cause the magnetic field probe 10 to move planarly or three-dimensionally. In addition, for example, the scanning unit may cause the detection target component 100a and the detection target substrate 100b to perform a planar motion or a three-dimensional motion, and the holding unit may cause the magnetic field probe 10 to perform a planar motion or a three-dimensional motion. In short, it is only necessary to obtain a near magnetic field intensity distribution such as a two-dimensional map or a three-dimensional map, and means and modes for changing the relative positions of the detection target component 100 a and the detection target substrate 100 b and the magnetic field probe 10. Is optional.

  In the magnetic field detection apparatus 1 (including the modification) of the above embodiment, the intensity distribution of the near magnetic field is obtained in the form of a two-dimensional map or a three-dimensional map, but it is not always necessary to obtain a map. For example, when specifying a location that generates a near magnetic field stronger than a predetermined intensity, a map such as a two-dimensional map or a three-dimensional map is unnecessary.

  In the magnetic field detection apparatus 1 (including the modified example) of the above embodiment, as shown in FIG. 4, the scanning direction of the scanning unit is parallel to the magnetic sensitive axis of the magnetic field detection circuit 15. Not limited to this.

  In the magnetic field detection device 1 (including the modification) of the above embodiment, since the magnetic field probe 10 included in the device is driven by an external power source, the magnetic field detection device 1 has a configuration including a power supply unit. . However, if the magnetic field probe 10 is driven by a battery mounted on the magnetic field probe 10, the magnetic field detection device 1 does not need to include a power supply unit.

  Incidentally, in the magnetic field probe 10 adopting, for example, an external power source as the power supply unit 21 for driving the magnetic field detection circuit 15, the voltage generated by the external power source slightly fluctuates or external electromagnetic noise is superimposed. There is. Further, the power supply path functions as an electric field antenna, and electric field noise may occur in the power supply path. The near magnetic field generated by the detection target component 100a and the detection target substrate 100b is very small. If such a slight voltage fluctuation or superposition of electromagnetic noise occurs, the detection accuracy of the near magnetic field may decrease. Absent. In that respect, in a magnetic field probe that employs, for example, a battery as the power supply unit 21 for driving the magnetic field detection circuit 15, the drive voltage of the electric field detection circuit 15 is chemically generated, and thus the drive voltage also varies slightly. Things are almost gone. In addition, since the power supply path can be shortened, it is possible to suppress external electromagnetic noise from being superimposed on the generated drive voltage or function as an electric field antenna to generate electric field noise.

  In the magnetic field probe 10 (including the modified example) of the above embodiment, the electric field shield 18 employs a three-layer structure in which an insulating layer, a metal layer, and a protective layer are sequentially stacked from the inside. Absent. If the magnetic field probe 10 or the magnetic field detection device 1 is used only in an environment where there is no impact from the outside, a two-layer structure in which the protective layer is omitted may be adopted as the electric field shield. Good.

  In the magnetic field probe 10 (including the modification) of the above-described embodiment, the electric field shield 18 includes the positive wiring 16a and the negative wiring 16b of the output wiring and the positive wiring 17a of the power wiring as shown in FIGS. The negative wiring 17b and the magnetic field detection circuit 15 are also covered so as to be collectively covered, but the present invention is not limited to this. Of these, the magnetic field detection circuit 15 may not be provided with the electric field shield 18. Further, the positive wiring 16a and the negative wiring 16b of the output wiring, and the positive wiring 17a and the negative wiring 17b of the power supply wiring do not need to be collectively provided, and may be provided separately. Of course, the positive wiring 16a and the negative wiring 16b of the output wiring and the positive wiring 17a and the negative wiring 17b of the power supply wiring can achieve the intended purpose even if the electric field shield 18 is not provided.

  In the magnetic field probe 10 (including the modified example) of the above-described embodiment, the magnetic field detection circuit 15 is configured as an IC package through a semiconductor process and disposed at the lower end of the probe unit 14, but is not limited thereto. In addition, for example, a thin film may be formed on one bottom surface of the probe unit 14 through a semiconductor process. Thereby, since further miniaturization of the magnetic field detection circuit 15 and by extension the probe unit 14 can be achieved, it is possible to be closer to the detection target, and it is possible to detect the near magnetic field with higher accuracy and higher spatial resolution. It becomes like this. In addition, when formed in a thin film through a semiconductor process, the size of the magnetic field detection circuit 15 is preferably formed to, for example, “5 to 10 μm square”.

  In the magnetic field probe 10 (including the modification) of the above embodiment, the magnetic field detection circuit 15 is configured as a full bridge circuit including the magnetoresistive elements 15a to 15d. In addition, for example, the magnetic field detection circuit may be configured as either a half bridge circuit including the magnetoresistive elements 15a and 15d or a half bridge circuit including the magnetoresistive elements 15c and 15b. Such a bridge circuit is not limited to a half bridge circuit. In short, if a bridge circuit including a magnetoresistive element that changes to a resistance value corresponding to an applied magnetic field is formed through a semiconductor process, the intended purpose can be achieved.

The schematic diagram which shows an example of the circuit structure about one Embodiment of the magnetic field probe which concerns on this invention. The figure which shows the external appearance from the perspective direction about the magnetic field probe of the embodiment. The figure which looked through the internal structure from the perspective direction about the magnetic field probe of the embodiment. The figure which shows an example of the whole structure of the magnetic field detection apparatus containing the magnetic field probe of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic field detection apparatus, 10 ... Magnetic field probe, 11 ... Main-body part, 12 ... Output terminal, 13 ... Power supply terminal, 14 ... Probe part, 15 ... Magnetic field detection circuit, 16 ... Output signal line, 16a ... Positive wiring, 16b ... Negative wiring, 17 ... Power supply line, 17a ... Plus wiring, 17b ... Minus wiring, 18 ... Electric field shield, 20 ... Power cable, 21 ... DC power supply, 30 ... Coaxial cable, 31 ... Signal processing unit, 32 ... Isolation amplifier 33 ... Preamplifier, 34 ... Spectrum analyzer, 100 ... Detection target, 100a ... Detection target component, 100b ... Detection target substrate.

Claims (18)

Electrically connected to a power supply terminal electrically connected to a power supply unit that supplies power to a magnetic field detection circuit that detects a magnetic field generated by a detection target including an electronic circuit, and a signal processing unit that processes an output signal of the magnetic field detection circuit A main body having an output terminal connected to
Probe section having the magnetic field detection circuit, a power supply line for electrically connecting the magnetic field detection circuit to the power supply terminal, and an output signal line for electrically connecting the magnetic field detection circuit to the output terminal And
A magnetic field probe for detecting a magnetic field generated by the detection target by bringing the magnetic field detection circuit close to the detection target,
The magnetic field detection circuit is a bridge circuit including a magnetoresistive element whose resistance value changes in accordance with an applied magnetic field, and the bridge circuit is formed through a semiconductor process.   2. The magnetic field probe according to claim 1, wherein the bridge circuit is formed in a size of about 5 to 10 μm square, or further in a minimum region. The bridge circuit is a half bridge circuit in which two magnetoresistive elements having the same magnetic field dependency and temperature characteristic are connected in series,
Of the two magnetoresistive elements constituting the half-bridge circuit, one of the magnetoresistive elements is covered with a magnetic material to provide a magnetic shield that is protected from external magnetic noise, and the other magnetoresistive element is The magnetic field probe according to claim 1, wherein a magnetic shield is not provided. The bridge circuit is a full bridge circuit in which two sets of half bridge circuits in which two magnetoresistive elements having the same magnetic field dependency and temperature characteristics are connected in series are connected in parallel symmetrically,
Among the four magnetoresistive elements constituting the full bridge circuit, one set of magnetoresistive elements located at the clearance positions that determine the equilibrium condition is protected from external magnetic noise by being covered with a magnetic material. The magnetic field probe according to claim 1, wherein the other set of magnetoresistive elements is not magnetically shielded. The probe unit has a plate-like substrate,
5. The magnetic field probe according to claim 1, wherein the bridge circuit is configured by an IC package, and is disposed on one bottom surface of the plate-like substrate. The probe unit has a plate-like substrate,
The magnetic field probe according to claim 1, wherein the bridge circuit is formed as a thin film on one bottom surface of the plate-like substrate.   The power supply line and the output signal line are each non-magnetic and are provided with electric field shields each including a metal layer made of a conductive metal material, and are protected from external electric field noise. The magnetic field probe according to claim 1, wherein the magnetic field probe is characterized in that:   The power supply line and the output signal line are non-magnetic and collectively provided with an electric field shield including a metal layer made of a conductive metal material, and are protected from external electric field noise. The magnetic field probe according to any one of claims 1 to 6.   The magnetic field detection circuit is provided with an electric field shield including a metal layer made of a nonmagnetic material and having a conductivity, and is protected from external electric field noise. 9. The magnetic field probe according to 8.   The electric field shield is composed of three layers: an insulating layer that electrically insulates the power supply line and the output signal line from the metal layer, the metal layer, and a protective film that protects the inside. The magnetic field probe according to claim 8 or 9, wherein   The magnetic field probe according to claim 1, wherein the power supply unit is an external power source outside the magnetic field probe.   The magnetic field probe according to claim 1, wherein the power supply unit is a battery mounted on the main body unit. Magnetic field probe according to any one of claims 1 to 11,
A power supply unit that supplies power to the magnetic field detection circuit via a power supply terminal of the magnetic field probe;
A signal processing unit for processing an output signal of the magnetic field detection circuit output via the output terminal of the magnetic field probe;
Holding means for holding the magnetic field probe in a state close to the detection target;
A magnetic field detection apparatus comprising: a scanning unit that scans the detection target with the magnetic field probe. A magnetic field probe according to claim 12;
A signal processing unit for processing an output signal of the magnetic field detection circuit output via the output terminal of the magnetic field probe;
Holding means for holding the magnetic field probe in a state close to the detection target;
A magnetic field detection apparatus comprising: a scanning unit that scans the detection target with the magnetic field probe. The holding means holds the detection target and the magnetic field detection circuit so as to be horizontally opposed to each other,
15. The magnetic field detection apparatus according to claim 13, wherein the scanning unit is an XY stage that mounts the detection target and is capable of planar movement together with the detection target mounted. The holding means holds the detection target and the magnetic field detection circuit so as to be horizontally opposed to each other,
15. The magnetic field detection apparatus according to claim 13, wherein the scanning unit is a three-dimensional stage on which the detection target is placed and capable of three-dimensional movement together with the placed detection target.   The magnetic field detection apparatus according to claim 15 or 16, wherein the signal processing unit maps the magnetic field intensity generated by the detection target based on the output signal.   A magnetic field characterized by detecting a direct current component of a magnetic field generated by the detection target using the magnetic field probe according to any one of claims 1 to 12 or the magnetic field detection device according to any one of claims 13 to 17. Detection method.

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