A high-density layout three-axis wide-band magnetic field sensor and its preparation method

Abstract

The present invention discloses a high-density layout three-axis wide-band magnetic field sensor and a preparation method thereof, belonging to the technical field of magnetic field sensors. A high-density layout three-axis wide-band magnetic field sensor includes three layers of substrates and each is provided with a bridge circuit. The three layers of substrates are Z-axis substrate, Y-axis substrate and X-axis substrate from top to bottom. The horizontal surfaces of the Y-axis substrate and the X-axis substrate are respectively provided with mutually perpendicular magnetic sensitive elements, and the magnetic sensitive element connected to the Z-axis substrate is vertically arranged on the vertical side of the Y-axis substrate. A preparation method is also disclosed, which adopts the above-mentioned high-density layout three-axis wide-band magnetic field sensor and a preparation method thereof, adopts the method of multi-layer stacking, extremely small package welding and high-density layout, reduces the volume of the sensor, realizes high-precision vector magnetic field measurement of a single point in space, and the preparation process is simple and easy to implement, ensuring the verticality of the magnetic sensitive element for detecting the magnetic field in the Z-axis direction.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic field sensors, and in particular to a high-density layout three-axis wide-band magnetic field sensor and a preparation method thereof. Background Art

[0002] A magnetic field sensor is a device that can convert magnetic field changes caused by various changes into electrical signals. With the rapid development of information industry, industrial automation, transportation, power electronics technology, office automation, household appliances, medical instruments, etc. and the popularization of electronic computer applications, a large number of sensors are needed to convert non-electrical parameters that need to be measured and controlled into easy-to-process electrical parameter signals.

[0003] Magnetic field sensors are widely used in various magnetic field measurement fields, such as industry, transportation, consumer electronics, medical and non-destructive testing. In the industrial field, magnetic sensors can be used for accurate measurement of displacement of various metal parts, current measurement of large machinery and instruments, automation control of industrial systems, monitoring of current such as power supplies and inverters, and energy management of distributed power grids. In the field of transportation, magnetic sensors are widely used in systems such as subways, cars, ships, airplanes and high-speed railways. For example, real-time monitoring and control of train position and running speed in subway systems, automatic control and flexible operation of escalators and elevators in subway systems, and security access control systems for subway stations. In automotive systems, magnetic sensors are used to sense the earth's magnetic field to determine the direction and position of the vehicle and provide accurate navigation information for the driver. Similarly, there are magnetic compasses used in navigation, magnetic heading instruments on aircraft, and speed, vibration and position information monitoring in high-speed railways. In the field of consumer electronics, magnetic sensors can be used in various smart wearable devices such as video game controllers, smart watches, smart phones and computers for motion detection and direction positioning. In medicine, magnetic sensors can be used to monitor the current and magnetic field of large equipment such as MRI (Magnetic Resonance Imaging) and CT (Computerized X-ray Tomography), and to monitor biological signals such as brain magnetism and muscle magnetism. In the field of non-destructive testing, magnetic sensors are used for consistency analysis of various conductive materials, such as aircraft skin testing, carbon fiber fracture testing, metal pipeline testing, and metal energy storage device testing.

[0004] In principle, magnetic field sensors only detect magnetic fields coming from a specific direction, so the relationship between the magnetic field source and the location of the sensor and how the object moves directly affects the application performance. However, the need to make products more compact and tightly integrate components makes it difficult to achieve an ideal layout of sensors and magnetic components. This leads to situations where target specifications cannot be achieved. Summary of the invention

[0005] The purpose of the present invention is to provide a high-density layout three-axis wide-band magnetic field sensor and a preparation method thereof to solve the above technical problems.

[0006] To achieve the above-mentioned purpose, the present invention provides a high-density layout three-axis wide-band magnetic field sensor, including three layers of substrates stacked up and down, each of the three layers of substrates is provided with a bridge circuit, and the three layers of substrates are electrically connected, the three layers of substrates are respectively a Z-axis substrate, a Y-axis substrate and an X-axis substrate from top to bottom, and mutually perpendicular magnetic sensitive elements are respectively arranged on the horizontal surfaces of the Y-axis substrate and the X-axis substrate for detecting the magnetic field in the Y-axis direction and the X-axis direction respectively, the Z-axis substrate is connected to a magnetic sensitive element for detecting the magnetic field in the Z-axis direction, and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is vertically arranged on the vertical side of the Y-axis substrate.

[0007] Preferably, the magnetic sensitive element is a magnetic resistor or a coil or a combination thereof.

[0008] Preferably, the magnetic sensitive element is arranged on a bridge arm of the bridge circuit, the two magnetic sensitive elements at the same network connection point have opposite sensitive directions, and the output end of the bridge circuit is connected to an operational discharger.

[0009] Preferably, the vertical distance between the magnetic sensitive element for detecting the Y-axis direction and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is 0.1-0.2 mm;

[0010] The vertical distance between the magnetic sensitive element for detecting the Y-axis direction and the magnetic sensitive element for detecting the X-axis direction is 0.1-0.2 mm.

[0011] Preferably, an impedance matching network is further provided, and the impedance matching network is electrically connected to the outermost substrate.

[0012] A method for preparing a three-axis wide-band magnetic field sensor based on the above-mentioned high-density layout, the specific steps are as follows:

[0013] Step S1: preparing a three-layer substrate;

[0014] Step S2: stacking three layers of substrates and electrically connecting the three layers of substrates using FPC (flexible printed circuit) cables, and setting output terminals on the outermost substrates;

[0015] Step S3: packaging the three-axis wide-band magnetic field sensor.

[0016] Preferably, in step S1, when preparing a substrate for detecting a magnetic field in the Z-axis direction, a different-plane wire bonding process is used to separately set the substrate and the magnetic sensitive element.

[0017] Preferably, in step S2, the horizontal direction includes an X-axis direction and a Y-axis direction.

[0018] One of the substrates for detecting the horizontal direction is arranged at the outermost side, and the other substrate for detecting the horizontal direction is horizontally rotated 90° and then vertically flipped 180° and placed on the outermost substrate. The two substrates detect magnetic fields in the X-axis direction and the Y-axis direction respectively. The substrate for detecting the magnetic field in the Z-axis direction is arranged above the two substrates, and a magnetic sensitive element for detecting the magnetic field in the Z-axis direction is arranged on the vertical side of one of the substrates for detecting the horizontal direction.

[0019] Preferably, the packaged three-axis wide-band magnetic field sensor is connected to an impedance matching network to adjust the amplitude-frequency characteristics of the output.

[0020] Therefore, the present invention adopts the above-mentioned high-density layout three-axis wide-band magnetic field sensor and its preparation method, which has the following beneficial effects:

[0021] (1) By adopting multi-layer stacking, ultra-small package welding and high-density layout, the sensor and surrounding resistors and capacitors are concentrated in one area, reducing the volume of the sensor. By adopting lamination stacking, the sensitive area of ​​the sensor can be concentrated in an area of ​​3mm x3mm x 3 mm, enhancing the single-point magnetic field measurement capability of the sensor.

[0022] (2) The other substrate is only provided with a bridge circuit, and a magnetic sensitive element for detecting the magnetic field in the Z-axis direction is connected in a separate structure. The magnetic sensitive element for detecting the magnetic field in the Z-axis direction is arranged on the vertical side of the substrate of the magnetic field in the Y-axis direction. The preparation process is simple and easy to implement, thereby ensuring the verticality of the magnetic sensitive element for detecting the magnetic field in the Z-axis direction.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a high-density layout three-axis wide-band magnetic field sensor of the present invention;

[0025] Figure 2 It is a schematic diagram of the structure of a substrate for detecting a horizontal magnetic field according to the present invention;

[0026] Figure 3 It is a schematic diagram of the substrate structure for detecting the magnetic field in the Z-axis direction of the present invention;

[0027] Figure 4 This is a schematic diagram of the bridge circuit structure of the present invention;

[0028] Figure 5 It is a frequency response curve diagram within the passband of the present invention.

[0029] Reference numerals

[0030] 1. Substrate; 11. X-axis substrate; 12. Y-axis substrate; 13. Z-axis substrate; 2. Magnetic sensitive element. DETAILED DESCRIPTION

[0031] Example

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0034] Example 1

[0035] like Figure 1 As shown, a high-density layout three-axis wide-band magnetic field sensor includes three layers of substrates 1 stacked up and down, and each of the three layers of substrates 1 is provided with a bridge circuit, such as Figure 4 As shown, in this embodiment, the bridge circuit adopts a Wheatstone full bridge circuit, and the three-layer substrate 1 is electrically connected by FPC wiring, wherein X1-X4 are magnetic sensitive elements. Figure 4In the figure, Vs+ and Vs- are the positive and negative voltage poles of the circuit, GND is the ground terminal, Vs represents the voltage terminal, Ox / Ox+ and - / Ox- are the output positive and output negative poles in the X-axis direction, Oy / Oy+ and - / Oy- are the output positive and output negative poles in the Y-axis direction, and Oz / Oz+ and - / Oz- are the output positive and output negative poles in the Z-axis direction. By adopting multi-layer stacking, extremely small package welding and high-density layout, the sensor and surrounding resistors and capacitors are concentrated in one area, which is likely to reduce the area occupied by the components. The total area depends on the size of the chip used and the area occupied by the pin package. Compared with traditional three-axis sensors, while ensuring that the channels do not crosstalk and the sensitivity is consistent, they are usually placed separately, resulting in low space utilization. This embodiment adopts laminated stacking, so that the sensitive area of ​​the sensor can be concentrated in an area of ​​3mm x 3mm x 3 mm, enhancing the single-point magnetic field measurement capability of the sensor.

[0036] The three-layer substrate 1 includes a Z-axis substrate 13, a Y-axis substrate 12, and an X-axis substrate 11 from top to bottom. Figure 2 As shown, the Y-axis substrate 12 and the X-axis substrate 11 are respectively provided with mutually perpendicular magnetic sensitive elements on their horizontal surfaces for detecting the magnetic field in the Y-axis direction and the X-axis direction, respectively. The Z-axis substrate 13 is connected with a magnetic sensitive element for detecting the magnetic field in the Z-axis direction, and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is vertically arranged on the vertical side of the Y-axis substrate 12. The two Y-axis substrates 12 and the X-axis substrate 11 have the same structure and only need to be horizontally rotated 90°. Figure 3 As shown, the Z-axis substrate 13 is only provided with a bridge circuit, and a magnetic sensitive element 2 for detecting the magnetic field in the Z-axis direction is connected in a separated structure. The magnetic sensitive element 2 for detecting the magnetic field in the Z-axis direction is arranged on the vertical side of the Y-axis substrate 12 of the magnetic field in the Y-axis direction. The vertical spacing between the magnetic sensitive element for detecting the magnetic field in the Y-axis direction and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is 0.1-0.2mm. The vertical spacing between the magnetic sensitive element for detecting the magnetic field in the Y-axis direction and the magnetic sensitive element for detecting the magnetic field in the X-axis direction is 0.1-0.2mm.

[0037] The magnetic sensitive element 2 is a magnetic resistor or a coil or a combination thereof. The coil and the magnetic resistor are located on the bridge arm of the Wheatstone full bridge. Their positions can be changed, such as the coil and the magnetic resistor are located in two bridge arms respectively, or the coil and the magnetic resistor are mixed and located in one bridge arm. By matching the impedance, the output of the Wheatstone full bridge is balanced. When a magnetic field in one direction is introduced, the two sensitive elements at the same network connection point are sensitive in opposite directions. The output of the bridge arm can be configured with an operational amplifier to make the output a single-ended output or a differential output to increase the output bandwidth of the sensor. By combining the magnetic resistor with the coil, the sensor bandwidth is expanded so that the sensor working bandwidth covers DC to hundreds of MHz (frequency unit, megahertz). In the differential mode, the sensor bandwidth mainly depends on the working frequency band of the magnetic sensitive element. In the single-ended output mode, the sensor bandwidth mainly depends on the operational amplifier used, such as the operational amplifier model INA826, the bandwidth is 1MHz; the operational amplifier model AD8421, the bandwidth is 12MHz; the operational amplifier model OPA891, the bandwidth is 180MHz.

[0038] The three-layer substrate 1 is stacked. Since the flatness of the substrate 1 and the magnetic sensitive element 2 is very high, it is easy to place the substrate 1 in parallel during stacking. The magnetic sensitive element 2 for detecting the magnetic field in the Z-axis direction is placed on the vertical side of the Y-axis substrate 12, so that the sensitive direction of the magnetic sensitive element 2 is very easy to be perpendicular to the circuit board, thereby realizing the arrangement of the three-axis sensitive element, which is different from the prior art that two circuit boards are placed orthogonally to realize the perpendicularity of the sensitive direction of the magnetic sensitive element 2. However, the perpendicularity depends on the angle and welding process when the two circuit boards are embedded, and the process is complicated, the precision is low and it is not easy to operate.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that an impedance matching network is further provided, and the impedance matching network is electrically connected to the outermost substrate 1 (X-axis substrate), which is suitable for situations where a flat amplitude-frequency characteristic is required in an application, and the amplitude-frequency characteristic of the sensor can be effectively adjusted by adjusting the gain at different frequencies.

[0041] A method for preparing a three-axis wide-band magnetic field sensor based on the above-mentioned high-density layout, the specific steps are as follows:

[0042] Step S1: preparing a three-layer substrate 1.

[0043] When the Z-axis substrate 13 is prepared, a different-plane wire bonding process is adopted to separate the magnetic sensitive element 2 from the Z-axis substrate 13 .

[0044] Step S2: stack three layers of substrates 1 and use FPC (flexible printed circuit) wiring to electrically connect the three layers of substrates 1, and set the output end on the outermost substrate 1. The horizontal direction includes the X-axis direction and the Y-axis direction, wherein the X-axis substrate 11 is set on the outermost side, and another Y-axis substrate 12 for detecting the horizontal direction is horizontally rotated 90° and then vertically flipped 180° and placed on the X-axis substrate 11. The X-axis substrate 11 and the Y-axis substrate 12 detect the magnetic field in the X-axis direction and the Y-axis direction respectively, and the Z-axis substrate 13 is set above the Y-axis substrate 12, and the magnetic sensitive element 2 for detecting the magnetic field in the Z-axis direction is set on the vertical side of the Y-axis substrate 12.

[0045] Step S3: packaging the three-axis wide-band magnetic field sensor.

[0046] The packaged three-axis wide-band magnetic field sensor is connected to an impedance matching network to adjust the amplitude-frequency characteristics of the output.

[0047] The above sensor is powered by ±5V-±12V, and the single-ended output is formed by internal configuration. The operational amplifier cutoff bandwidth is 1MHz. A Helmholtz coil is used to generate a DC-1MHz wide frequency domain magnetic field of about 40uT. The frequency response test of this sensor is as follows Figure 5 As shown in the figure, the final result is that within the DC-1MHz range, the sensor sensitivity is no less than 20mV / V / uT, and the signal-to-noise ratio within the passband is no less than 20dB.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A high-density layout three-axis wide-band magnetic field sensor, characterized in that: It comprises three layers of substrates stacked up and down, each of which is provided with a bridge circuit, and the three layers of substrates are electrically connected, and the three layers of substrates are Z-axis substrate, Y-axis substrate and X-axis substrate from top to bottom, respectively, and mutually perpendicular magnetic sensitive elements are respectively provided on the horizontal surfaces of the Y-axis substrate and the X-axis substrate for detecting magnetic fields in the Y-axis direction and the X-axis direction, respectively, and the Z-axis substrate is connected with a magnetic sensitive element for detecting magnetic fields in the Z-axis direction, and the magnetic sensitive element for detecting magnetic fields in the Z-axis direction is vertically arranged on the vertical side of the Y-axis substrate; The magnetic sensitive element is arranged on the bridge arm of the bridge circuit. The two magnetic sensitive elements at the same network connection point have opposite sensitive directions. The output end of the bridge circuit is connected with an operational amplifier.

2. The high-density layout three-axis wide-band magnetic field sensor according to claim 1, characterized in that: The magnetic sensitive element is a magnetic resistor or a coil or a combination thereof.

3. The high-density layout three-axis wide-band magnetic field sensor according to claim 1, characterized in that: The vertical distance between the magnetic sensitive element for detecting the magnetic field in the Y-axis direction and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is 0.1-0.2mm; The vertical distance between the magnetic sensitive element for detecting the magnetic field in the Y-axis direction and the magnetic sensitive element for detecting the magnetic field in the X-axis direction is 0.1-0.2 mm.

4. The high-density layout three-axis wide-band magnetic field sensor according to claim 1, characterized in that: An impedance matching network is also provided, and the impedance matching network is electrically connected to the X-axis substrate.

5. A method for preparing a high-density layout three-axis wide-band magnetic field sensor according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: Step S1: preparing a three-layer substrate; Step S2: stacking three layers of substrates and electrically connecting the three layers of substrates with FPC cables, and setting an output terminal on the X-axis substrate; the horizontal direction includes the X-axis direction and the Y-axis direction, the X-axis substrate for detecting the X-axis direction is set on the outermost side, and the other Y-axis substrate for detecting the Y-axis direction is horizontally rotated 90° and then vertically flipped 180° and placed on the X-axis substrate, the X-axis substrate and the Y-axis substrate detect the magnetic field in the X-axis direction and the Y-axis direction respectively, the substrate for detecting the magnetic field in the Z-axis direction is set above the two substrates, and the magnetic sensitive element for detecting the magnetic field in the Z-axis direction is set on the vertical side of the Y-axis substrate; Step S3: packaging the three-axis wide-band magnetic field sensor.

6. The method for preparing a high-density layout three-axis wide-band magnetic field sensor according to claim 5, characterized in that: In step S1, when preparing a substrate for detecting a magnetic field in the Z-axis direction, a different-plane wire bonding process is used to separately set the substrate and the magnetic sensitive element.

7. The method for preparing a high-density layout three-axis wide-band magnetic field sensor according to claim 6, characterized in that: The packaged three-axis wide-band magnetic field sensor is connected to an impedance matching network to adjust the amplitude-frequency characteristics of the output.

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