Optimization method of magnetic field sensor integrating GMR Wheatstone bridge and high-density exciting coil

Abstract

The invention provides an optimization method of a magnetic field sensor integrated with a GMR Wheatstone bridge and a high-density excitation coil, and relates to the technical field of magnetic field sensing, and the optimization method comprises the steps: the optimization design of the GMR Wheatstone bridge: the GMR Wheatstone bridge is composed of four power-type GMR resistors R1-R4, a constant-current driving source is configured, four bridge arms of the GMR Wheatstone bridge serve as four wiring terminals, and the four wiring terminals are connected with the GMR Wheatstone bridge; a wiring end between the R1 and the R2 is connected with a constant current driving source, a wiring end between the R1 and the R4 is a V + output end, and a wiring end between the R2 and the R3 is a V-output end; a multi-layer high-density exciting coil is prepared from an epoxy resin-based composite material, and the number of layers, the number of turns and the wiring direction of the coil are designed according to the magnetic field intensity requirement and different coil driving voltages; and chip scale packaging: respectively integrating GMR resistors on the diagonal lines of the Wheatstone bridge to form a GMR microchip, constructing a bridge module through a high-precision ceramic carrier plate, and embedding the bridge module into the epoxy resin-based composite substrate.

Description

Technical Field

[0001] This invention relates to the field of magnetic field sensing technology, and in particular to an optimization method for a magnetic field sensor that integrates a GMR Wheatstone bridge and a high-density excitation coil. Background Technology

[0002] Magnetic field sensors are widely used in industrial automation, current detection, position sensing, biomedicine, and other fields. With the development of the Internet of Things (IoT), smart grids, and new energy vehicles, the demand for high-sensitivity, low-power, and miniaturized magnetic field sensors is increasing. GMR sensors, based on the spin-correlated scattering effect, have advantages such as high sensitivity (10-20% resistance change rate), wide linear range, and low power consumption, making them suitable for high-precision magnetic field detection.

[0003] In the aerospace field, GMR sensors are mainly used in memory-type load switches, load current monitoring, and motor servo control. However, they face serious shortcomings in terms of high reliability, high integration, and miniaturization, primarily in the following aspects: First, traditional Hall elements lack sufficient sensitivity, while GMR sensors, although possessing high sensitivity, rely on external magnetic field excitation, resulting in large system size and high power consumption. Second, existing excitation coils mostly employ PCB structures with limited turns and require a magnetic core to constrain the magnetic field direction, resulting in a magnetic field strength below 50 Oe, which is insufficient to meet high-precision detection requirements. Furthermore, the separate design of the GMR sensing unit and the excitation coil leads to signal transmission loss, hindering chip-level integration. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes an optimization method for a magnetic field sensor that integrates a GMR Wheatstone bridge and a high-density excitation coil, thereby achieving the goals of high reliability, high integration, and miniaturization of the magnetic field sensor.

[0005] An optimization method for a magnetic field sensor integrating a GMR Wheatstone bridge and a high-density excitation coil includes:

[0006] S1, GMR Wheatstone bridge optimized design

[0007] The GMR Wheatstone bridge consists of four power-type GMR resistors R1-R4, configured with a constant current drive source. The four arms of the GMR Wheatstone bridge serve as four terminals. The terminal between R1 and R2 is connected to the constant current drive source, the terminal between R1 and R4 is the V+ output terminal, and the terminal between R2 and R3 is the V- output terminal.

[0008] S2, Optimized design of high-density excitation coil

[0009] Multilayer high-density excitation coils are fabricated using epoxy resin-based composite materials. The number of coil layers, turns, and routing direction are designed according to different magnetic field strength requirements and coil driving voltages. Different magnetic fields are generated according to different directions of the pulse current flowing through them, so that the GMR Wheatstone bridge outputs different differential voltages.

[0010] S3, chip-level packaging

[0011] A dual-chip C-4 flip-chip integration scheme is adopted: the GMR resistors on the diagonal of the Wheatstone bridge are integrated to form a GMR microchip, and the bridge module is constructed through a high-precision ceramic carrier and embedded in an epoxy resin-based composite substrate.

[0012] Optionally, the method of fabricating multilayer high-density excitation coils using epoxy resin-based composite materials, and designing the number of coil layers, turns, and routing direction according to different magnetic field strength requirements and coil driving voltages, includes:

[0013] Multilayer high-density excitation coils are arranged in the inner layer of an epoxy resin-based composite substrate. Each layer of coils is configured with a preset number of turns. The first layer of coils is arranged in a counterclockwise loop from the inside out. After the outermost loop, the second layer is arranged in a clockwise loop, and so on, until the last layer is completed. The trace width is selected between 20um and 200um depending on the magnitude of the coil current. When the pulse current flows through the high-density excitation coil, a magnetic field perpendicular to the plane of the paper is generated in the rectangular groove in the middle of the epoxy resin-based composite substrate. When the current direction is clockwise, the magnetic field direction is from the inside out; when the current direction is counterclockwise, the magnetic field direction is from the outside in.

[0014] Optionally, the step of integrating the GMR resistors on the diagonal of the Wheatstone bridge to form a GMR microchip, constructing a bridge module using a high-precision ceramic substrate and embedding it into an epoxy resin-based composite substrate includes:

[0015] GMR resistors R1 and R3 form GMR microchip D1, and GMR resistors R2 and R4 form GMR microchip D2. GMR microchips D1 and D2 are soldered onto a high-precision ceramic substrate. The high-precision ceramic substrate has conductive patterns and lead-out pads. D1, D2, and the high-precision ceramic substrate form a module which is placed in a rectangular groove in the middle of an epoxy resin-based composite substrate and fixed. The constant current source excitation and output differential voltage are connected to the epoxy resin-based composite substrate by gold wire bonding. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is the circuit diagram for the GMR Wheatstone bridge.

[0018] Figure 2 This is a schematic diagram showing the routing of eight high-density excitation coils in an epoxy resin-based composite substrate.

[0019] Figure 3 Ansys Maxwell coil simulation model;

[0020] Figure 4 The direction of the magnetic field in the central hole of the coil;

[0021] Figure 5 This is a contour plot of the magnetic field strength across the coil cross-section;

[0022] Figure 6 The magnetic field strength curves at the central axis of the coil under different currents;

[0023] Figure 7 This is a cross-sectional view of a magnetic field sensor chip package that integrates a GMR Wheatstone bridge and a high-density excitation coil. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides an optimization method for a magnetic field sensor integrating a GMR Wheatstone bridge and a high-density excitation coil, characterized by comprising:

[0026] S1, GMR Wheatstone bridge optimized design

[0027] Traditional signal-type GMR resistors are only suitable for detecting weak signals. They have small differential output voltages, poor noise immunity, and lack stability when driven by an external voltage source.

[0028] This embodiment uses a power-type GMR resistor (with a change rate ≥6.0% and a resistance value of 5.0-5.3kΩ) and integrates a 1mA constant current source driver inside the chip, which can output a high signal-to-noise ratio differential signal of ≥150mV. This significantly improves the anti-interference performance of the device in the complex electromagnetic environment of space and provides a stable and reliable magnetic field detection and current monitoring solution for key systems such as satellite power management and motor drive control.

[0029] like Figure 1 As shown, the GMR Wheatstone bridge consists of four power-type GMR resistors R1-R4. The power-type GMR resistors (variance rate ≥ 6.0%, resistance value 5.0-5.3kΩ) have a maximum allowable current of 2mA and are configured with a 1mA constant current drive source. The four arms of the GMR Wheatstone bridge serve as four terminals. The terminal between R1 and R2 is connected to the 1mA constant current drive source, the terminal between R1 and R4 is the V+ output terminal, and the terminal between R2 and R3 is the V- output terminal.

[0030] The arrows on the resistors indicate the direction of resistance change under specific magnetic field directions and intensities: when the magnetic field direction is from the inside out, R1 and R3 have low values ​​(5.0kΩ); when the magnetic field direction is from the outside in, R2 and R4 have high values ​​(5.3kΩ). Based on the above design, the differential voltage is calculated under a 1mA constant current drive as follows:

[0031] (1)

[0032] (2)

[0033] (3)

[0034] Where I is the integrated constant current drive source, with a typical value of 1mA in this embodiment; R1~R4 are the resistance values ​​of the power-type GMR resistors; V ref This is the bias voltage value; a typical value in this embodiment is 2.5V. dif It is a differential voltage.

[0035] Depending on the direction of the magnetic field, the GMR Wheatstone bridge has two operating states:

[0036] In state one, when the magnetic field direction is from inside to outside, due to the giant magnetoresistance effect and the arrangement of the Wheatstone bridge, R1=R3=5.0k, R2=R4=5.3k, and the integrated constant current source I=1mA, substituting into formulas (1), (2), and (3), the difference value V is calculated. dif =150mV.

[0037] In state two, when the magnetic field direction is from the outside to the inside, due to the giant magnetoresistance effect and the arrangement of the Wheatstone bridge, R1=R3=5.3k, R2=R4=5.0k, and the integrated constant current source I=1mA, substituting into formulas (1), (2), and (3), the difference value V is calculated. dif =-150mV.

[0038] Test results show that the optimized GMR Wheatstone bridge can generate an output voltage of ±150mV when the magnetic field direction is reversed, and the output voltage fluctuation does not exceed 1% of the nominal value in a wide temperature range of -55℃ to +150℃.

[0039] S2, Optimized design of high-density excitation coil

[0040] Existing excitation coils mostly use PCB structures, have a limited number of turns, and require a magnetic core to constrain the direction of the magnetic field, resulting in low magnetic field strength, which makes it difficult to meet the requirements of high-precision detection.

[0041] In this embodiment, a multilayer high-density excitation coil is prepared using epoxy resin-based composite material. It is designed to have 4, 6, or 8 layers according to different magnetic field strength requirements and coil driving voltage. By optimizing the interlayer interconnection process, 320 turns of precision winding are achieved in the 8-layer structure. Only 130mA of driving current is required to generate a high-intensity magnetic field of ≥75Oe, which meets the special requirements of spacecraft vacuum environment tolerance and radiation resistance.

[0042] like Figure 2 As shown, eight layers of high-density excitation coils are arranged in the inner layer of an epoxy resin-based composite substrate. The number of turns in each layer is shown in Table 1. The first layer of coils is traced in a counter-clockwise loop from the inside out. After the outermost loop, the second layer is traced clockwise, and so on, completing the trace on the last layer. The trace width is selected between 20µm and 200µm depending on the magnitude of the coil current. When the pulse current flows through the high-density excitation coil, a magnetic field perpendicular to the plane of the paper is generated in the rectangular groove in the middle of the epoxy resin-based composite substrate. When the current direction is clockwise, the magnetic field direction is from the inside out. The differential output value V of the GMR Wheatstone bridge is... dif =150mV, when the current direction is counterclockwise and the magnetic field direction is from outside to inside, the GMR Wheatstone bridge output differential value V dif =-150mV.

[0043] Table 1

[0044] layer Number of turns design 1 43 2 45 3 35 4 36 5 43 6 43 7 43 8 32 Total number of turns 320

[0045] Simulations were performed based on the above design, such as... Figure 3As shown, a coil model is built in Ansys Maxwell. The model is divided into two parts. The upper layer has three coil layers with a total of 123 turns (43+45+35=123). The gap in the middle is the dielectric layer. The lower layer has five coil layers with a total of 197 turns (36+43×3+32=197). The total number of turns is 320 (123+197=320).

[0046] The solver is set to static magnetic field excitation with balloon-like boundary conditions. Excitation currents of 50mA, 80mA, 100mA, and 130mA are used for parametric variable scanning. Vector solutions are then performed on the spatial magnetic field within the coil's central hole to obtain the magnetic field direction within that hole. Figure 4 As shown, the magnetic field direction of the central hole is consistent, pointing from the bottom surface to the top surface, which is consistent with the design.

[0047] The magnetic field strength contour map of the coil cross section is as follows Figure 5 As shown, within the inner diameter of the coil, the magnetic field is stronger the closer it is to the coil in the horizontal direction, the weaker the magnetic field is in the middle, and the weakest magnetic field is at the central axis of the coil. In the vertical direction, the magnetic field is stronger the closer it is to the coil and weaker the further it is from the coil. This is consistent with the design. During implementation, it is ensured that the bridge module is located at the central axis of the coil.

[0048] The magnetic field at the central axis of the coil is solved to obtain the magnetic field strength curves under different currents, such as... Figure 6 As shown, the magnetic field strength exhibits two peaks, located at 0.24 mm and 1.24 mm respectively, corresponding to the positions of the two coil sections in the model. This is because, in the vertical direction, the magnetic field is strongest near the coil and weakens towards the sides; and since the core layer is relatively thick, the coils are distributed on both sides of the core layer, forming two excitation points, thus creating two peaks. The magnetic field distribution between the two peaks is relatively uniform.

[0049] Based on the simulation results, a high-density excitation coil based on epoxy resin-based composite material was prepared, and the formula for calculating the pulse current in the coil is as follows.

[0050] (4)

[0051] Among them, I pulse R is the pulse current in the coil. L R is the resistance of the excitation coil. m For the impedance of the wiring cable, V + This is the excitation voltage of the coil.

[0052] When R L =73.7Ω, R m =0.2Ω, external excitation voltage V + =9.6V, duration 10ms, substituting into formula (4), we get IPULSE =9.6 / (73.7+0.2)=130mA, the magnetic field strength at the central axis of the rectangular groove is approximately 78oe, and the implementation result meets the requirements.

[0053] S3, chip-level packaging

[0054] To address the issue of high magnetic circuit loss in traditional discrete GMR sensors, this embodiment employs a dual-chip C-4 flip-chip integrated solution: the GMR resistors on the diagonal of the Wheatstone bridge are integrated to form a 1.4mm×0.87mm×0.4mm GMR microchip, and the bridge module is constructed using a high-precision ceramic substrate and embedded in an epoxy resin-based composite substrate.

[0055] like Figure 7 As shown, GMR resistors R1 and R3 constitute GMR microchip D1, and GMR resistors R2 and R4 constitute GMR microchip D2. GMR microchips D1 and D2 are soldered onto a high-precision ceramic substrate. The high-precision ceramic substrate has conductive patterns and lead-out pads. D1, D2, and the high-precision ceramic substrate form a module which is placed in a rectangular groove in the middle of an epoxy resin-based composite substrate and fixed. The constant current source excitation and output differential voltage are connected to the epoxy resin-based composite substrate by gold wire bonding.

[0056] By directly embedding a module consisting of D1, D2, and a high-precision ceramic carrier plate into a rectangular groove at the center of a high-density excitation coil, a minimum magnetic path (<2mm) is formed, increasing magnetic field utilization by over 40%. Tests show that under 20kHz alternating magnetic field excitation, this structure can control signal transmission loss to within 3dB. Furthermore, the high reliability of the C-4 package meets MIL-STD-883G military standard requirements, making it particularly suitable for long-term stable operation in spacecraft vibration environments.

[0057] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An optimization method for a magnetic field sensor integrating a GMR Wheatstone bridge and a high-density excitation coil, comprising: S1, GMR Wheatstone bridge optimized design The GMR Wheatstone bridge consists of four power-type GMR resistors R1-R4, configured with a constant current drive source. The four arms of the GMR Wheatstone bridge serve as four terminals. The terminal between R1 and R2 is connected to the constant current drive source, the terminal between R1 and R4 is the V+ output terminal, and the terminal between R2 and R3 is the V- output terminal. S2, Optimized design of high-density excitation coil Multilayer high-density excitation coils are fabricated using epoxy resin-based composite materials. The number of coil layers, turns, and routing direction are designed according to different magnetic field strength requirements and coil driving voltages. Different magnetic fields are generated according to different directions of the pulse current flowing through them, so that the GMR Wheatstone bridge outputs different differential voltages. S3, chip-level packaging A dual-chip C-4 flip-chip integration scheme is adopted: the GMR resistors on the diagonal of the Wheatstone bridge are integrated to form a GMR microchip, and the bridge module is constructed through a high-precision ceramic carrier and embedded in an epoxy resin-based composite substrate.

2. The method for optimizing a magnetic field sensor integrating a GMR Wheatstone bridge and a high-density excitation coil according to claim 1, characterized in that, The method involves fabricating multilayer high-density excitation coils using epoxy resin-based composite materials. The number of coil layers, turns, and routing direction are designed according to different magnetic field strength requirements and coil driving voltages, including: Multilayer high-density excitation coils are arranged in the inner layer of an epoxy resin-based composite substrate. Each layer of coils is configured with a preset number of turns. The first layer of coils is arranged in a counterclockwise loop from the inside out. After the outermost loop, the second layer is arranged in a clockwise loop, and so on, until the last layer is completed. The trace width is selected between 20um and 200um depending on the magnitude of the coil current. When the pulse current flows through the high-density excitation coil, a magnetic field perpendicular to the plane of the paper is generated in the rectangular groove in the middle of the epoxy resin-based composite substrate. When the current direction is clockwise, the magnetic field direction is from the inside out; when the current direction is counterclockwise, the magnetic field direction is from the outside in.

3. The method for optimizing a magnetic field sensor integrating a GMR Wheatstone bridge and a high-density excitation coil as described in claim 1, characterized in that... The method involves integrating the GMR resistors on the diagonal of a Wheatstone bridge to form a GMR microchip, constructing a bridge module using a high-precision ceramic substrate, and embedding it into an epoxy resin-based composite substrate, comprising: GMR resistors R1 and R3 form GMR microchip D1, and GMR resistors R2 and R4 form GMR microchip D2. GMR microchips D1 and D2 are soldered onto a high-precision ceramic substrate. The high-precision ceramic substrate has conductive patterns and lead-out pads. D1, D2, and the high-precision ceramic substrate form a module which is placed in a rectangular groove in the middle of an epoxy resin-based composite substrate and fixed. The constant current source excitation and output differential voltage are connected to the epoxy resin-based composite substrate by gold wire bonding.

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