A contact / non-contact force-magnetic dual-mode sensing sensor based on magnetostrictive film

Abstract

The present invention is a contact / non-contact force-magnetic dual-mode sensing sensor based on a magnetostrictive film. The sensor comprises a sensitive layer, a conversion layer, a conversion circuit and an excitation power supply; the sensitive layer is a magnetostrictive film, the conversion layer is a three-layer flexible graphic circuit, the top layer of the three base layers of the FPC is covered with a copper layer, and the two lower base layers are respectively provided with a pickup coil and an excitation coil; the pickup coil is connected to the conversion circuit, and the excitation coil is connected to the excitation power supply; the copper layer is connected to the ground wire; the sensitive layer is deposited on the top copper coating of the conversion layer. The present invention can directly pick up the magnetization state change in the magnetostrictive film without a mechanical response process, and has the excellent performance of high sensitivity, short response time and recovery time, good compatibility, and full-range perception.

Description

Technical Field

[0001] The present invention applies magnetostrictive film materials to the field of electronic skin. Based on the unique magnetomechanical coupling effect of magnetostrictive film, the bending deflection / magnetic field dual information perception is realized through the change of magnetization state under stress / magnetic field. It can be applied to the joints between humans and bionic robots to obtain real-time hand / limb posture and spatial position information, and realize high-sensitivity, high-resolution contact and non-contact human-computer interaction. Background Art

[0002] Electronic skin is a new type of electronic device that simulates the human skin's sense of external stimuli (pressure, temperature, humidity) through the integration and feedback of electrical signals. It integrates multiple technologies such as new material technology and sensor technology. Among the various sensing functions of electronic skin, tactile perception is the basis for its direct interaction with the external environment. With the rise of intelligent electronics, humanized robots and virtual reality technology, more and more real and virtual objects need to be sensed and manipulated, which requires electronic skin to have both contact and non-contact sensing functions. This can be achieved by adding feedback to magnetic field signals on the basis of tactile interaction [3]. Creating a highly sensitive, simple and reliable stress / magnetic field dual-information sensing flexible sensor array and clarifying the sensing mechanism of the sensor array have important theoretical and practical significance for the expansion of human perception and the development of human-computer interaction technology.

[0003] High-density array flexible sensors (electronic skin) that can accurately sense the size and position of external force / magnetic field require not only new sensitive materials with skin-like properties, but also sensor units and system integration with breakthrough information extraction principles and key performance requirements. However, sensitive materials and sensor arrays that can meet the above requirements are still extremely challenging. The force-magnetic dual-mode sensing technology reported so far can be summarized as using polymer carriers with dispersed magnetic particles as sensitive elements, and causing changes in the microstructure of materials or devices through the movement of magnetic particles under the action of external force or magnetic field, thereby causing changes in response signals such as resistance, capacitance, magnetoresistance, triboelectricity, and displacement reaction voltage to achieve dual information sensing. Related research has greatly promoted the development of force-magnetic dual-mode sensing technology. However, the sensing unit configuration of embedding magnetic material particles into flexible polymer materials as sensitive elements has many problems that need to be solved, such as low flexibility, low magnetic force, large polymer resistance, weak conductivity, slow sensing response, and poor stability. At present, it is difficult to meet the requirements of high performance, miniaturization, scale and flexibility of force-magnetic dual-mode sensing flexible sensor arrays. Therefore, there is an urgent need for a new type of sensor to achieve high flexibility, high reliability and high sensitivity of force and magnetic dual-mode sensing technology. Summary of the invention

[0004] The purpose of the present invention is to propose a contact / non-contact force-magnetic dual-mode sensing sensor based on a magnetostrictive film in view of the shortcomings in the current technology. The sensor is composed of a sensitive layer, a conversion layer, a matching conversion circuit and an excitation power supply. The magnetostrictive film sensitive layer and the coil conversion layer are arranged vertically to form a planar flexible sensing structure, which can sense the change of the magnetization state in the magnetostrictive film under force-magnetic conditions. By connecting the two ends of the excitation coil to the excitation power supply, connecting the two ends of the pickup coil to the conversion circuit, and measuring the signal amplitude at the two ends of the pickup coil under the alternating magnetic field, the force-magnetic physical quantity sensed by the sensitive layer can be converted into an electrical signal, and the electrical signal can be separated into two different positive and negative regions by configuring the direction of the bending force and the magnetic field, so as to realize contact / non-contact dual information perception. The structure of the present invention directly picks up the change of the magnetization state in the magnetostrictive film without a mechanical response process, and has high sensitivity, short response time and recovery time, good compatibility, and excellent performance of full-range perception. Using a structure and a wire to simultaneously realize force-magnetic signal sensing greatly simplifies the design and manufacture of contact / non-contact dual information perception electronic skin.

[0005] The technical solution of the present invention is:

[0006] A contact / non-contact force-magnetic dual-mode sensing sensor based on a magnetostrictive film, the sensor comprising a sensitive layer, a conversion layer, a conversion circuit and an excitation power supply;

[0007] The sensitive layer is a magnetostrictive film made of Fe-Ni, Fe-Co, Fe-Ga or TerFenol; the thickness ranges from 1 to 1000 microns;

[0008] The conversion layer is a three-layer flexible graphic circuit. Among the three base layers of the FPC, the top layer is covered with a copper layer, and the two lower base layers are respectively provided with a pickup coil and an excitation coil;

[0009] The pickup coil is connected to the conversion circuit, the excitation coil is connected to the excitation power supply; the copper layer is connected to the ground wire;

[0010] The sensitive layer is deposited on the top copper clad layer of the conversion layer;

[0011] The three base layers of the FPC are made of polyimide (PI) or polydimethylsiloxane (PDMS) with a thickness of 0.01-0.03 mm. The layers are insulated from each other and only have magnetic field coupling. The copper conductor is 10-20 microns thick.

[0012] The conversion circuit is composed of an AC signal amplitude measurement system and a pre-voltage amplifier; the AC signal amplitude measurement system is a single-coil structure, using a phase-locked amplifier, or a double-coil structure using a digital oscilloscope; or a chip;

[0013] The excitation power supply is a waveform generator.

[0014] The method for preparing the conversion layer comprises the following steps:

[0015] Take four single-sided copper foil base boards, where the base is an insulating material and the conductive layer is copper foil. Drill holes and plate through holes at the center of the four base boards, use optical imaging pattern transfer and etching process methods to print circuits, and print pickup coils, excitation coils, and leads at the center between two layers on three base boards respectively; with the copper foil side of all base boards facing up, attach the fourth base board to the printed three-layer base board, and use insulating materials to thermally bond them into an FPC; the outermost bare copper layer of the FPC is used as the electrodeposition substrate of the sensitive layer, and is grounded during operation;

[0016] The method for preparing the sensitive layer comprises the following steps:

[0017] The PFC with the top layer of copper foil was cleaned and pickled as the cathode, the platinum plate was used as the anode, and the Co-Fe alloy electrodeposition solution was used as the electrolyte. At a temperature of 50°C, the DC power supply was used in constant current mode, and the current density was controlled at 0.35A / cm 2 , the pH of the electrolyte was controlled at 3 by dropping 10% dilute sulfuric acid solution, the electrodeposition time was 40 minutes, and the FPC substrate was taken out, cleaned and dried;

[0018] The electrodeposition solution is composed of iron sulfate, cobalt sulfate, complexing agent, buffer, antioxidant and surface brightener, and uses electrolyzed water as solvent, specifically containing FeSO4·7H2O 0.01~0.1mol / L, CoSO4·7H2O 0.1~0.5mol / L, sodium citrate 0.2~0.5mol / L, boric acid 0.2~0.3mol / L, ascorbic acid 0.5~2g / L, saccharin 1~3g / L, sodium dodecyl sulfate 0.01~0.05g / L;

[0019] The essential features of the present invention are:

[0020] The force-magnetic dual-mode sensor consists of a sensitive layer, a conversion layer, a matching conversion circuit and an excitation power supply. The conversion layer is a three-layer flexible graphic circuit, the top layer is exposed copper, the middle layer is a pickup coil, and the bottom layer is an excitation coil. The sensitive layer is a magnetostrictive film, which is prepared on the top layer of the flexible graphic circuit. The excitation power supply is connected to both ends of the excitation coil to provide an alternating magnetic field for the sensitive layer. Using the nonlinear characteristics of the magnetization curve and according to Faraday's law of electromagnetic induction, the conversion circuit receives the electrical signals at both ends of the pickup coil, which can reflect the magnetization process of the sensitive layer material under the action of external stress field and external magnetic field. The design force / magnetism applied in the normal direction of the magnetostrictive film affects the vector of the magnetization state in the material, so that the electrical signal can be separated into the upper and lower regions of the contact / non-contact signal in the time domain. The electrical signal output by this single structure and wire can sense the contact / non-contact bending force / magnetic field changes in real time without state conversion.

[0021] The beneficial effects of the present invention are specifically embodied as follows:

[0022] 1. Compared with traditional flexible electronic skin, the present invention can only sense single-mode signals, and the measurement range and sensitivity are fixed. The flexible electronic skin in the present invention can detect two sensing modes: force and magnetism. In addition, this flexible electronic skin can adjust the bending force detection range and sensitivity by changing the shear modulus on different thin plate materials, and realize non-contact sensing at different distances by setting a permanent magnet.

[0023] 2. The present invention utilizes mature thin film material preparation and photolithography technology to facilitate large-scale production (due to the simplicity of the FPC process and low cost, the maximum area can reach the meter level; while the current microstructure sensors with polymer carriers that disperse and fill magnetic particles as sensitive elements are produced based on costly silicon-based technology and have an area of ​​only centimeters). The use of a single structure and leads to achieve contact / non-contact sensing greatly reduces the cost of design, production and application.

[0024] 3. No moving mechanism and aging parts, good durability and no maintenance. Can work below 300℃, strong environmental adaptability.

[0025] 4. The structure of the present invention directly picks up the magnetization state change in the magnetostrictive film without mechanical response process, and has high sensitivity, short response time and recovery time, good compatibility, and excellent performance of full-range perception. The maximum sensitivity is 1mV / mm in the deflection range of 0.5mm to 6mm, the maximum sensitivity is 10mV / mm in the permanent magnet distance range of 12mm to 34mm, and the response time is less than 1ms. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of the magnetostrictive force and magnetic dual-mode sensor in the present invention;

[0027] Among them, 1-magnetostrictive electrodeposited Co-Fe thin film sensitive layer, 2-conversion layer, 4-excitation power supply;

[0028] 21-pickup coil middle layer, 22-excitation coil bottom layer; 31-AC signal amplitude measurement system, 32-pre-voltage amplifier;

[0029] Figure 2 It is a structural diagram of the sensitive layer and the conversion layer in the present invention;

[0030] Figure 3 Comparison between the single coil / double coil structure and the output harmonic amplitude of the planar flexible sensor in the present invention;

[0031] Figure 4 It is the electric signal of the double coil structure magnetic sensing in the present invention; wherein, Figure 4 (a) Sensor method: Output electrical signals by loading different deflections upward; Figure 4 (b) The sensor method loads different magnetic fields to output electrical signals;

[0032] Figure 5 Output characteristics of force-magnetic dual-mode sensor loaded with different deflection deformation and magnetic field strength in the range of room temperature to 300℃; Figure 5 (a) The rate of change of output voltage amplitude when the sensor is loaded with different deflections in the normal direction; Figure 5 (b) The rate of change of the output voltage amplitude when the sensor is loaded with different magnetic fields in the normal direction;

[0033] Figure 6 The sensor of the present invention is installed at the joint of the manipulator to realize contact and non-contact interactive output signals and schematic diagram; wherein, Figure 6 (a) is the sensor output signal; Figure 6 (b) Schematic diagram of the dual information perception test platform. DETAILED DESCRIPTION

[0034] The invention is further described in detail below in conjunction with the figures. This embodiment is only a specific description of the invention and is not to be regarded as limiting the scope of protection.

[0035] The structure of the force-magnetic dual-mode sensor for contact / non-contact sensing of the present invention is as follows: Figure 1 As shown, the sensor comprises a sensitive layer 1, a conversion layer 2, a conversion circuit and an excitation power supply 4;

[0036] The sensitive layer is a magnetostrictive film made of Fe-Ni, Fe-Co, Fe-Ga or TerFenol, etc., with a thickness ranging from 1 to 1000 microns;

[0037] The conversion layer 2 is a three-layer flexible graphic circuit, the structure of which is as follows: Figure 2As shown, the three base layers of the FPC are respectively provided with a copper layer, a middle layer pickup coil 21, and a bottom layer excitation coil 22; however, the sequence of the middle layer and the bottom layer is not limited thereto;

[0038] The three base layers of the FPC are made of polyimide (PI) with a thickness of 0.01-0.03 mm; the layers are insulated from each other and only have magnetic field coupling; the copper conductor is 10-20 microns thick.

[0039] The pickup coil 21 is connected to the conversion circuit, the excitation coil 22 is connected to the excitation power supply 4; the copper layer is connected to the ground wire;

[0040] The sensitive layer is deposited on the top copper clad layer of the conversion layer;

[0041] A method for preparing a force-magnetic dual-mode sensor for contact / non-contact sensing comprises the following steps:

[0042] (1) Preparation of FPC:

[0043] Take four single-sided copper foil base boards (the base is a 25-micron polyimide insulation layer and the conductive layer is a 12-micron copper foil) and cut them into 8.5mm*12mm rectangles. Drill holes and plate through holes at the center of the four base boards (for the leads at the center of the planar coil). Print circuits using light imaging pattern transfer and etching process methods. Print the pickup coil 21, the excitation coil 22 and the leads at the center between the two layers on three base boards (the leads are connected to the two coils respectively, and the straight line segment leading out of the planar vortex coil from the center has a wire diameter and a wire spacing of 0.07mm), wherein the wire diameter and the wire spacing are both 0.07mm, and the coils have 15 turns; With the copper foil side of all base boards facing up, attach the fourth base board to the printed three-layer base board, and use polyethylene glue to thermally bond them into an FPC; The outermost layer of the FPC is a bare copper layer 24, which serves as the electrodeposition substrate of the sensitive layer and is grounded during operation;

[0044] (2) A method for preparing a magnetostrictive electrodeposited Co-Fe thin film sensitive layer 1 comprises the following steps:

[0045] The top layer of 5~25 micron copper foil was cleaned and pickled as the cathode, the platinum plate was used as the anode, and the Co-Fe alloy electrodeposition solution was used as the electrolyte. At a temperature of 50°C, the DC power supply was used in constant current mode, and the current density was controlled at 0.35A / cm 2 , the pH of the electrolyte was controlled at 3 by dropping 10% dilute sulfuric acid solution, the electrodeposition time was 40 minutes, the deposition thickness was about 2 microns, the plane size was 8.5mm*12mm, and the FPC substrate was taken out, cleaned and dried;

[0046] The electrodeposition solution is composed of iron sulfate, cobalt sulfate, complexing agent, buffer, antioxidant and surface brightener, and uses electrolyzed water as solvent, specifically containing FeSO4·7H2O 0.01~0.1mol / L, CoSO4·7H2O 0.1~0.5mol / L, sodium citrate 0.2~0.5mol / L, boric acid 0.2~0.3mol / L, ascorbic acid 0.5~2g / L, saccharin 1~3g / L, sodium dodecyl sulfate 0.01~0.05g / L;

[0047] (3) A conversion circuit, which is composed of an AC signal amplitude measurement system 31 and a pre-voltage amplifier 32; the AC signal amplitude measurement system is a single-coil structure using a Zurich Instruments HF2LI lock-in amplifier to measure the second harmonic amplitude, or a dual-coil structure using a digital oscilloscope Tektronix DPO3014 to measure the output alternating voltage amplitude, or a chip TPF111, etc. (specifically, the Zurich Instruments HF2LI lock-in amplifier in this embodiment); 32- the pre-voltage amplifier is a Stanford SR560, which amplifies the received 21- pickup coil output electrical signal by 100 times;

[0048] (4) The excitation power supply is an arbitrary waveform generator Tektronix AWG5202, which provides a sinusoidal alternating current with an amplitude of 5V and a frequency of 1kHz, and is connected to the excitation coil in the conversion layer FPC;

[0049] Example 1: Under the same conditions, a single coil and a double coil structure were used for comparative tests to study the output characteristics of different structures.

[0050] Experimental platform construction: according to Figure 1 , without loading external force and magnetic field, the excitation power supply provides the excitation coil with a sinusoidal alternating current with an amplitude of 5V and a frequency of 1kHz, the output electrical signal of the pickup coil is tested, and the harmonic composition is analyzed.

[0051] Experimental process and results: According to the electromagnetic theorem, the magnetic permeability can reflect the change of the magnetization state in the sensitive layer material. It is an even function of time, and its change is reflected in the amplitude of the even harmonic component of the excitation signal. The collection of odd harmonic components of the excitation signal in the induced electromotive force is generated by the transformer effect and is related to the intensity of the excitation magnetic field. The single coil structure is as follows: Figure 3 As shown in a in the figure, the proportion of each frequency harmonic of the picked-up electrical signal is analyzed without external force and magnetic field, as shown in Figure 3The c in the figure reflects that the second harmonic of the magnetization state of the sensitive layer material accounts for a small proportion, and a phase-locked amplifier is required to measure the amplitude of the second harmonic to reflect the measured force and magnetic information. Since the signal of the single coil structure is small, a pair of mutually reverse excitation coils are designed, and their excitation magnetic fields are opposite. In this way, the equivalent field under the action of the external force magnetic field in the sensitive layer material under the excitation coil area, one of which is added to the excitation magnetic field, and the other is subtracted from the excitation magnetic field. The induction coils are connected in the same direction to eliminate the transformer signal. The double coil structure is as follows: Figure 3 As shown in b in the figure, the proportion of each frequency harmonic of the picked-up electrical signal is analyzed without external force and magnetic field, as shown in Figure 3 The d in the figure reflects that the first harmonic of the magnetization state of the sensitive layer material accounts for a large proportion, and the output signal amplitude can be directly measured to reflect the measured force and magnetic information. Since the double coil structure directly measures the output signal amplitude, it has high sensitivity and is easy to measure. Figure 3 The structure in b is used as a conversion layer in the following embodiments.

[0052] Example 2: Use a universal mechanical testing machine to load different deflection deformations on the sensor using a standard three-point bending test, use a permanent magnet to load the magnetic field at different positions, and test the sensor's magnetic and force dual-mode information output characteristics.

[0053] Experimental platform construction: Use the universal mechanical testing machine DANA DN-W20N and its standard three-point bending test fixture to load 0.5mm to 6mm deflection deformation in both positive and negative directions on the normal direction of the sensor plane; use the permanent magnet Sm2Co 17 (remanent magnetism 0.87T, coercive force 657.39kA / m, length 10mm*width 10mm*height 3mm) with N and S poles pointing to the sensor plane, approaching the sensor from a distance of 34mm to 12mm respectively; measuring the output electrical signal amplitude of the double-coil structure.

[0054] Experimental process and results: Figure 4 As shown, the double coil structure magnetomechanical sensing electrical signal; Figure 4 (a) When the display sensor method loads upward and downward deflections, it can output monotonous and stable electrical signals, and can identify the direction and size of the deflection. The maximum sensitivity is 1mV / mm in the deflection range of 0.5mm to 6mm; Figure 4 (b) shows that when the permanent magnet with its N pole or S pole approaches the sensor at different positions, it can output a monotonically stable electrical signal, identify the direction and magnitude of the magnetic field, and has a maximum sensitivity of 10mV / mm within the range of 12mm to 34mm from the permanent magnet; the response time for the output signal to rise and fall is less than 1ms.

[0055] Example 3: The sensor is loaded with different deflection deformations and magnetic field strengths in a high temperature box to verify the temperature stability of the force-magnetic dual-mode sensor.

[0056] Experimental platform construction: The sensor, deflection and permanent magnet in Example 2 are placed in a high temperature box and connected to a mechanical testing machine through a connecting rod. Within the range of room temperature to 300°C, the sensor plane is loaded with a deflection deformation of 0.5mm to 6mm and a magnetic field strength of 0kA / m to 11kA / m.

[0057] Experimental process and results: Considering the different initial magnetization states of the sensor sensitive layer, the measured signal Characterizes the change of the sensor with external force / magnetic field, where , V0 and V are the initial and real-time voltage amplitudes of the sensor respectively; in the range of room temperature to 300℃, the sensor plane is loaded with a deflection deformation of 0.5mm to 6mm in the normal direction, and the output results are as follows Figure 5 As shown in (a); the sensor plane is loaded with a magnetic field strength of 0kA / m to 11kA / m in the normal direction, and the output result is as follows Figure 5 (b) The sensor has a stable output signal, can work below 300°C, and has strong environmental adaptability.

[0058] At present, flexible dual-mode pressure (contact) and magnetic field (non-contact) sensors (Zhou Q, Ji B, Hu B, et al. Tilted magnetic micropillars enabled dual-mode sensor for tactile / touchless perceptions[J]. Nano Energy, 2020, 78.) can only be used at room temperature, with a magnetic field detection limit of 25mT and a pressure detection limit of 1.2N. The sensor shown in this example can be used in an environment at 300°C, with a magnetic field detection limit of 1.1kA / m (13.75mT) and a deflection detection limit of 0.5mm (stress of 0.02N). It can be used in the joints of humans or collaborative robots in complex environments to collect the position and state information of hands or limbs, and realize contact and non-contact perception. For details, see Example 4.

[0059] Example 4: Sensors are installed at the joints of the manipulator to achieve contact and non-contact interaction, verifying the dual-information perception effect of the force-magnetic dual-mode sensor.

[0060] Experimental platform construction: Three force-magnetic dual-mode sensors are installed at the three finger joints of the Robotiq three-finger manipulator. The target object can be reliably grasped according to the position indicated by the permanent magnet. When the joint is bent, the normal of the sensor plane bends inward, and the N pole of the magnetic mark points to the sensor plane. Considering the different initial magnetization states of the sensitive layers of each sensor, the measurement signal Characterizes the change of the sensor with external force / magnetic field, where , V0 and V are the initial and real-time voltage amplitudes of the sensor respectively; the computer operates the manipulator according to the sensor output signal to achieve contact and non-contact interaction.

[0061] Experimental process and results: Figure 6 As shown in (b), the sensor is installed at the joint of the manipulator, and the target object with a magnetic mark is placed in front of the manipulator. When the manipulator approaches the target object without contact, the influence of the magnetic mark on the sensor gradually decreases; when the manipulator touches the target object (finger A touches the target object first), the bending force on the sensor gradually increases; when the manipulator completely grasps the target object and bends to the extreme position, the sensor output reaches the maximum; when the manipulator leaves the target object, the sensor repeats the opposite process and outputs a signal, such as Figure 6 (a) shown.

[0062] Matters not covered by the present invention are known technologies.

Claims

1. A contact / non-contact force-magnetic dual-mode sensing sensor based on magnetostrictive film, characterized by: The sensor comprises a sensitive layer, a conversion layer, a conversion circuit and an excitation power supply; The sensitive layer is a magnetostrictive film made of Fe-Ni, Fe-Co, Fe-Ga or TerFenol; the thickness ranges from 1 to 1000 microns; The conversion layer is a three-layer flexible graphic circuit. Among the three base layers of the FPC, the top layer is covered with a copper layer, and the two lower base layers are respectively provided with a pickup coil and an excitation coil; The pickup coil is connected to the conversion circuit, the excitation coil is connected to the excitation power supply; the copper layer is connected to the ground wire; The sensitive layer is deposited on the top copper clad layer of the conversion layer; The three base layers of the FPC are made of polyimide or polydimethylsiloxane with a thickness of 0.01-0.03 mm. The layers are insulated from each other, with only magnetic field coupling. The copper conductor is 10-20 microns thick. The conversion circuit is composed of an AC signal amplitude measurement system and a pre-voltage amplifier; the AC signal amplitude measurement system is a single-coil structure, using a phase-locked amplifier, or a double-coil structure, using a digital oscilloscope; or a chip; The excitation power supply is a waveform generator; The method for preparing the conversion layer comprises the following steps: Take four single-sided copper foil base boards, where the base is an insulating material and the conductive layer is copper foil. Drill holes and plate through holes at the center of the four base boards, use optical imaging pattern transfer and etching process methods to print circuits, and print pickup coils, excitation coils, and leads at the center between two layers on three base boards respectively; with the copper foil side of all base boards facing up, attach the fourth base board to the printed three-layer base board, and use insulating materials to thermally bond them into an FPC; the outermost bare copper layer of the FPC is used as the electrodeposition substrate of the sensitive layer, and is grounded during operation; The preparation method of the sensitive layer comprises the following steps: cleaning and pickling the PFC with the top layer of copper foil as the cathode, using the platinum plate as the anode, using the Co-Fe alloy electrodeposition solution as the electrolyte, and using the DC power supply constant current mode output at a temperature of 50°C, and controlling the current density at 0.35A / cm 2 , the pH of the electrolyte was controlled at 3 by dropping 10% dilute sulfuric acid solution, the electrodeposition time was 40 minutes, and the FPC substrate was taken out, cleaned and dried; The electrodeposition solution is composed of iron sulfate, cobalt sulfate, a complexing agent, a buffer, an antioxidant and a surface brightener, and uses electrolyzed water as a solvent. Specifically, it contains 0.01-0.1 mol / L of FeSO4·7H2O, 0.1-0.5 mol / L of CoSO4·7H2O, 0.2-0.5 mol / L of sodium citrate, 0.2-0.3 mol / L of boric acid, 0.5-2 g / L of ascorbic acid, 1-3 g / L of saccharin and 0.01-0.05 g / L of sodium dodecyl sulfate.

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