Manufacturing Method of Fluxgate Sensing Chip and Fluxgate Sensing Chip

Abstract

The present invention provides a manufacturing method of a fluxgate sensing chip and a fluxgate sensing chip, belonging to the technical field of sensing chips. The manufacturing method of the fluxgate sensing chip includes: etching a magnetic core groove, a solenoid coil groove and a through hole on two silicon wafers respectively, and etching an electrode cavity on at least one of the silicon wafers, the positions of the magnetic core grooves and the through holes on the two silicon wafers correspond to each other, the directions of the solenoid coil grooves on the two silicon wafers are opposite, and the electrode cavity communicates with the solenoid coil groove; bonding the two silicon wafers to form a closed magnetic core groove and coil structure; casting the closed coil structure by using a liquid metal casting technology to form a fluxgate coil, and obtaining a processed wafer; dicing the processed wafer to obtain a fluxgate sensing chip. By avoiding the use of electroplating process, the magnetic core structure is not limited, and the magnetic core thickness can be increased by an order of magnitude compared with the electroplating process, improving the detection sensitivity of the fluxgate sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of sensing chips, and particularly to a manufacturing method of a fluxgate sensing chip, a fluxgate sensing chip, and a wire current detection method. Background Art

[0002] A fluxgate sensor is a type of magnetic field sensitive device derived from the transformer effect. It mainly detects a constant changing or low-frequency weak magnetic field based on Faraday's law of electromagnetic induction and the magnetization saturation characteristics of soft magnetic materials.

[0003] Benefiting from the development of micro-nano manufacturing technology, traditional fluxgate sensors are evolving towards chipization, integration, and intelligence, meeting the requirements of more application scenarios. Compared with traditional fluxgate sensors, a fluxgate sensing chip fabricated using micro-nano technology is small in size, light in weight, low in power consumption, and low in noise. Sensing chips produced in the same batch have good consistency and low cost, and the sensing chip and the signal processing circuit are easy to integrate, showing good development prospects.

[0004] For existing micro fluxgate sensors, the processing of their coils and magnetic cores relies on electroplating technology. However, the magnetic cores fabricated using electroplating technology have poor film formation quality, low magnetic permeability, high coercivity, and poor consistency. The thickness of the magnetic core can only reach dozens of micrometers, restricting the detection sensitivity of micro fluxgate sensors. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a manufacturing method of a fluxgate sensing chip, a fluxgate sensing chip, and a wire current detection method. The manufacturing method of the fluxgate sensing chip adopts a liquid metal casting technology. The overall chip manufacturing process is clean and pollution-free, with a high chip yield and good consistency. The cross-sectional area of the coil is large, which can reduce the coil resistance. The distance between adjacent coils is small, which can increase the number of coil turns within a limited space, improving the detection sensitivity of the chip. The magnetic core is fabricated by processing high magnetic permeability strip materials, and the thickness can range from dozens to hundreds of micrometers, increasing the cross-sectional area of the magnetic core and improving the detection sensitivity of the fluxgate sensor.

[0006] To achieve the above purpose, the first aspect of the present application provides a manufacturing method of a fluxgate sensing chip, including:

[0007] Etch core slots, solenoid coil slots, and through holes on two silicon wafers respectively, and etch electrode cavities on at least one of the silicon wafers. The positions of the core slots and through holes on the two silicon wafers correspond to each other, and the directions of the solenoid coil slots on the two silicon wafers are opposite. The electrode cavities communicate with the solenoid coil slots. Among them, on each silicon wafer, the solenoid coil slots at least include multiple induction coil slots and multiple excitation coil slots. The multiple induction coil slots and multiple excitation coil slots respectively span across the core slots, and the through holes are located at both ends of each induction coil slot and each excitation coil slot.

[0008] Deposit an insulating layer on the surfaces of the core slots, solenoid coil slots, and the inner surfaces of the through holes.

[0009] Place the core in the core slot on one of the silicon wafers.

[0010] Bond the two silicon wafers to form a closed core slot and coil structure.

[0011] Use the liquid metal casting technology to cast the closed coil structure to form a fluxgate coil, and obtain a processed wafer.

[0012] Slice the processed wafer to obtain a fluxgate sensing chip.

[0013] In the embodiment of the present application, the solenoid coil slots further include multiple feedback coil slots; each feedback coil slot spans across the core slot, and through holes are provided at both ends of each feedback coil slot.

[0014] In the embodiment of the present application, the electrode cavity includes multiple groups of input electrode cavities and output electrode cavities. The multiple induction coil slots and multiple excitation coil slots respectively correspond to a group of input electrode cavities and output electrode cavities.

[0015] The step of using the liquid metal casting technology to cast the closed coil structure to form a fluxgate coil and obtain a processed wafer includes:

[0016] Inject liquid alloy into any one of the electrode cavities in each group of input electrode cavities and output electrode cavities respectively, so that the liquid alloy flows through the through holes and solenoid coil slots, and finally reaches the other electrode cavity to obtain a fluxgate coil.

[0017] In the embodiment of the present application, the core is a film structure formed by processing a strip, and the thickness of the core is from dozens to hundreds of micrometers.

[0018] In the embodiment of the present application, the core is any one of a racetrack shape, a rectangle, a triangle, and a ring shape.

[0019] In the embodiment of the present application, the liquid alloy is a single metal or an alloy material.

[0020] The second aspect of the present application provides a fluxgate sensing chip, which includes a magnetic core and two silicon wafers;

[0021] Magnetic core grooves, solenoid coil grooves and through holes are etched on the two silicon wafers, and electrode cavities are etched on at least one of the silicon wafers; wherein, the positions of the magnetic core grooves and through holes on the two silicon wafers correspond to each other, the directions of the solenoid coil grooves on the two silicon wafers are opposite, and the electrode cavities communicate with the solenoid coil grooves; on each silicon wafer, the solenoid coil groove at least includes a plurality of induction coil grooves and a plurality of excitation coil grooves, the plurality of induction coil grooves and the plurality of excitation coil grooves respectively span the magnetic core groove, and the through holes are located at both ends of each induction coil groove and each excitation coil groove; an insulating layer is deposited on the surfaces of the magnetic core groove, the solenoid coil groove and the inner surface of the through hole;

[0022] The two silicon wafers are bonded to form a closed magnetic core groove and coil structure, and the closed coil structure is cast by a liquid metal casting technique to form a fluxgate coil, and the magnetic core is located in the closed magnetic core groove.

[0023] In the embodiment of the present application, the fluxgate sensing chip includes at least two sets of excitation coils, one set of induction coils and one set of feedback coils.

[0024] The third aspect of the present application provides a method for detecting wire current. A fluxgate current sensing chip is processed and manufactured by using the manufacturing method of the above-mentioned fluxgate sensing chip for detection, including the following steps:

[0025] The fluxgate current sensing chip is brought close to the wire to be measured, and the magnetic field generated by the wire to be measured is detected by the fluxgate current sensing chip to obtain a current detection result.

[0026] In the embodiment of the present application, there are multiple fluxgate current sensing chips, and the multiple fluxgate current sensing chips are respectively arranged in an array around the wire to be measured.

[0027] In the embodiment of the present application, the step of bringing the fluxgate current sensing chip close to the wire to be measured and detecting the magnetic field generated by the wire to be measured by the fluxgate current sensing chip to obtain a current detection result includes:

[0028] The fluxgate current sensing chip is brought close to the wire to be measured, and the fluxgate current sensing chip performs a patch-type closed-loop detection to detect the magnetic field generated by the wire to be measured to obtain a current detection result.

[0029] In the embodiment of the present application, the patch-type closed-loop detection performed by the fluxgate current sensing chip includes:

[0030] Part of the induction coils in the fluxgate current sensing chip are reused as feedback coils for patch-type closed-loop detection.

[0031] In the embodiment of the present application, the fluxgate current sensing chip includes a feedback coil;

[0032] The patch-type closed-loop detection performed by the fluxgate current sensing chip includes:

[0033] Directly using the feedback coil of the fluxgate current sensing chip for patch-type closed-loop detection.

[0034] Through the above technical solution, a magnetic core groove, a solenoid coil groove, and a through hole are etched on two silicon wafers respectively, and an electrode cavity is etched on at least one of the silicon wafers. The positions of the magnetic core grooves and through holes on the two silicon wafers correspond to each other, and the directions of the solenoid coil grooves on the two silicon wafers are opposite. The electrode cavity communicates with the solenoid coil groove. Among them, on each silicon wafer, the solenoid coil groove includes at least a plurality of induction coil grooves and a plurality of excitation coil grooves. The plurality of induction coil grooves and the plurality of excitation coil grooves respectively straddle the magnetic core groove, and the through holes are located at both ends of each induction coil groove and each excitation coil groove. An insulating layer is deposited on the surfaces of the magnetic core groove, the solenoid coil groove, and the inner surface of the through hole. The magnetic core is placed in the magnetic core groove on one of the silicon wafers. The two silicon wafers are bonded to form a closed magnetic core groove and coil structure. The closed coil structure is cast by using a liquid metal casting technology to form a fluxgate coil, and a processed wafer is obtained. The processed wafer is sliced to obtain a fluxgate sensing chip. The use of liquid metal casting technology for processing can form and mass-produce solenoid coils in one step, with a simple process flow, a short production cycle, high coil size accuracy, and good consistency. The coil structure is flexibly controllable. The magnetic core groove formed by the closed coil can accommodate a magnetic core with a thickness of several hundred micrometers, improving the detection sensitivity of the fluxgate sensor. At the same time, the cross-sectional area of the coil processed by the casting technology is much larger than that of the coil made by the traditional electroplating process, which can effectively reduce the resistance of the coil. The distance between adjacent coils can be controlled to be very small, and the number of coil turns can be increased in a limited space, further improving the detection sensitivity of the chip. Mass processing using MEMS technology avoids the use of electroplating technology. The overall chip manufacturing process is clean and pollution-free, with low mass production cost and high chip yield.

[0035] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent specific implementation part. Brief Description of the Drawings

[0036] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the following specific implementation manners, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0037] Figure 1Schematically shows a flowchart of a method for manufacturing a fluxgate sensing chip according to an embodiment of the present application;

[0038] Figure 2 Schematically shows a schematic diagram of the influence of the magnetic core thickness on the detection sensitivity of the fluxgate sensing chip according to an embodiment of the present application;

[0039] Figure 3 Schematically shows a schematic diagram of the structure of a fluxgate current sensing chip according to an embodiment of the present application;

[0040] Figure 4 Schematically shows a processing flowchart of a fluxgate current sensing chip according to an embodiment of the present application;

[0041] Figure 5 Schematically shows a schematic diagram of the manufacturing process of a fluxgate coil according to an embodiment of the present application;

[0042] Figure 6 Schematically shows a schematic diagram of a chip sensing model according to an embodiment of the present application;

[0043] Figure 7 Schematically shows a schematic diagram of a dual-chip sensing model according to an embodiment of the present application;

[0044] Figure 8 Schematically shows a comparison diagram of the output signals of chips with a magnetic core thickness of 20 microns and 200 microns according to an embodiment of the present application.

[0045] Description of reference numerals

[0046] 1 - magnetic core; 2 - induction coil; 3 - excitation coil; 4 - feedback coil; 6 - first electrode cavity; 7 - second electrode cavity; 8 - through hole; 9 - solenoid coil groove; 10 - liquid alloy; 12 - excitation coil of the current sensing chip; 13 - induction coil of the current sensing chip; 14 - feedback coil of the current sensing chip; 15 - wire to be measured; 16 - magnetic force line; 17 - magnetic field direction. Detailed implementation manners

[0047] The following details the specific implementation manners of the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0048] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of the present application, such descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0049] This embodiment provides a method for manufacturing a fluxgate sensing chip, which is batch processed using MEMS technology. The fluxgate coil is fabricated using liquid metal casting technology, avoiding the use of electroplating technology to fabricate the fluxgate coil and the subsequent slotting to insert the magnetic core 1. The coil structure is flexible and controllable, and the magnetic core slot formed by the closed coil can accommodate a magnetic core 1 with a thickness of several hundred micrometers, thereby improving the detection sensitivity of the chip.

[0050] It should be noted that the above method for manufacturing a fluxgate sensing chip can be used to manufacture any sensing chip that realizes its function through magnetic field detection. For the convenience of explaining the solution, this embodiment mainly takes the fluxgate current sensing chip as an example for illustration.

[0051] Please refer to Figure 4 , this embodiment provides a process for a method for manufacturing a fluxgate sensing chip, which includes steps such as etching a wafer, depositing an insulating layer, placing the magnetic core 1, bonding, casting the coil, and dicing. Specifically, please refer to Figure 1 , the method for manufacturing the fluxgate sensing chip has the following steps:

[0052] Step 210: Etch a magnetic core slot, a solenoid coil slot 9, and a through hole 8 on each of two silicon wafers, and etch an electrode cavity on at least one of the two silicon wafers. The positions of the magnetic core slots and the through holes 8 on the two silicon wafers correspond to each other, and the directions of the solenoid coil slots 9 on the two silicon wafers are opposite. The electrode cavity communicates with the solenoid coil slot 9 or the through hole 8. Among them, on each silicon wafer, the solenoid coil slot 9 includes at least multiple induction coil slots and multiple excitation coil slots. The multiple induction coil slots and the multiple excitation coil slots respectively span the magnetic core slot, and the through hole 8 is located at both ends of each induction coil slot and each excitation coil slot;

[0053] In this embodiment, a mask may be used to etch a magnetic core groove, a solenoid coil groove 9, and a through-hole 8 structure on two silicon wafers (denoted as silicon wafer A and silicon wafer B) respectively. The above-mentioned silicon wafers may be thinned. The magnetic core grooves, the solenoid coil grooves 9, and the through-holes 8 on the two silicon wafers correspond to each other so that a complete magnetic core groove and solenoid coil groove 9 are formed after the two silicon wafers are combined. The solenoid coil groove 9 can be connected through the through-hole 8. An electrode cavity may be etched on one of the silicon wafers, or electrode cavities may be etched on the two silicon wafers respectively. When etching on the two silicon wafers, the electrode cavities on the two silicon wafers correspond to each other. The position of the electrode cavity is generally at the end of the solenoid coil groove 9. If there are four sets of coils, there can be four sets of electrode cavities, which are located at the beginning and end of each set of coils respectively; or there can be only one set, and this set of electrode cavities is at the end of one set of coils left after the multi-group coils are connected in series and parallel. The above-mentioned electrode cavity may be connected to the solenoid coil groove 9 at the end of the coil, or may be connected to the through-hole 8 at the end of each coil. The above-mentioned magnetic core groove is used to place the magnetic core 1, and the solenoid coil groove 9 is used to place the coil.

[0054] Through-holes 8 are provided at both ends of each induction coil groove and each excitation coil groove to connect multiple induction coil grooves on the two silicon wafers and to connect multiple excitation coil grooves. The multiple induction coil grooves are connected to each other through the through-holes 8 at both ends, and the multiple excitation coil grooves are connected to each other through the through-holes 8 at both ends. The above-mentioned electrode cavity may include multiple groups of electrode cavities. Each group of electrode cavities includes an input electrode cavity and an output electrode cavity. The above-mentioned multiple induction coil grooves and multiple excitation coil grooves may respectively include several groups, and these groups of coil grooves are connected. Eventually, each type of coil only includes an input electrode cavity and an output electrode cavity; in some embodiments, these groups of coils are discrete, and eventually these groups of coils share an input electrode cavity and an output electrode cavity.

[0055] In specific use, some of the induction coils 2 of the fluxgate sensing chip can be reused as feedback coils 4, or multiple feedback coils 4 can be designed and added separately. In some embodiments, the solenoid coil groove 9 further includes multiple feedback coil grooves; each feedback coil groove straddles the magnetic core groove, and through-holes 8 are provided at both ends of each feedback coil groove.

[0056] In this embodiment, multiple feedback coil grooves on the two silicon wafers straddle the magnetic core groove, and the through-holes 8 are located at both ends of each feedback coil groove. The above-mentioned induction coil grooves and excitation coil grooves are used to place induction coils 2 and excitation coils 3 respectively, and the feedback coil grooves are used to place feedback coils 4. Among them, the excitation magnetic field generated by the excitation coil 3 magnetically modulates the soft magnetic material magnetic core 1, driving the magnetic core material into the critical saturation state. Utilizing the non-linear change characteristic of the magnetic permeability when the magnetic core 1 is magnetically saturated, high-sensitivity detection of the external magnetic field and the current to be measured is realized. The feedback coil 4 is used to provide a compensation current for zero-flux adjustment to realize patch-type closed-loop detection.

[0057] By providing multiple feedback coil slots for placing the feedback coil 4, when the manufactured fluxgate sensing chip performs closed-loop detection, there is no need for a magnetic ring. The feedback coil 4 is directly integrated on the chip, realizing surface-mounted closed-loop control, reducing the volume of the sensor, and lowering the production cost. Moreover, the feedback coil 4 can be selected according to actual open-loop or closed-loop detection requirements. When feedback coil 4 is not needed for open-loop detection, the feedback coil 4 can be directly used as the induction coil 2; during closed-loop detection, some of the induction coils 2 can also be directly used as the feedback coil 4.

[0058] Step 220: Deposit an insulating layer on the surface of the magnetic core slot, the solenoid coil slot 9, and the inner surface of the through hole 8;

[0059] In this embodiment, this step is mainly to deposit an insulating layer, including depositing an insulating layer on the inner surfaces of the magnetic core slot, the solenoid coil slot 9, and the through hole 8. The insulating layer material can be silicon dioxide, silicon carbide, or polyimide.

[0060] Step 230: Place the magnetic core 1 in the magnetic core slot on one of the silicon wafers;

[0061] In this embodiment, this step is to place the magnetic core 1. The above-mentioned magnetic core 1 can be pre-processed. For example, the processed magnetic core 1 is placed in the magnetic core slot etched on the silicon wafer A to realize the pre-embedded magnetic core 1. The pre-embedded magnetic core 1 usually has better ferromagnetic properties than the electroplated magnetic core 1. The magnetic core 1 is placed in the magnetic core slot in an embedded manner, avoiding later grooving or cutting the magnetic core slot, and at the same time avoiding the influence of later slotting on the magnetic core performance. The magnetic core has a high matching degree with the coil. It should be noted that in specific implementation, the thickness of the above-mentioned magnetic core 1 can be from dozens to hundreds of microns.

[0062] In some embodiments, the magnetic core 1 is a film structure formed by processing a strip.

[0063] In this embodiment, the above-mentioned preparation of the magnetic core 1 can be to manufacture the magnetic core 1 by processing a strip. The processing method can be mechanical cutting of the strip, or die processing after laminating and curing the strip. The magnetic core material can be permalloy, various amorphous or nanocrystalline strips, or a film structure formed by processing the above-mentioned strips, avoiding the use of electroplating processes. The magnetic core 1 is manufactured by processing a high magnetic permeability strip, and the thickness can be from dozens to hundreds of microns, which can significantly increase the cross-sectional area of the magnetic core 1, thereby improving the detection sensitivity of the chip.

[0064] Please refer to Figure 8 , Figure 8The output signals generated by fluxgate sensing chips with the thickness of the magnetic core 1 being 20 μm and 200 μm respectively are compared. The results show that the output voltage (about 200 mV) of the fluxgate sensing chip with the magnetic core 1 thickness of 200 μm is significantly enhanced compared to the output voltage (about 15 mV) of the fluxgate sensing chip with a thickness of 20 μm.

[0065] It should be noted that the shape of the above magnetic core 1 can be structures such as rectangular, triangular, annular, racetrack-shaped, etc. The overall length of the chip does not exceed 12 mm, the overall width of the chip does not exceed 4 mm, the overall height of the chip does not exceed 1 mm, and the cross-sectional area of the coil is 0.006 mm 2 , and the thickness of the magnetic core 1 does not exceed 300 μm.

[0066] In some embodiments, please refer to Figure 3 , the magnetic core 1 is racetrack-shaped, and the racetrack width is 1.2 mm; the overall width of the magnetic core groove is 3.6 mm, the length is 12 mm, and the thickness is 200 μm, the width of the excitation coil groove is 40 μm, the length is 1.5 mm, and the thickness is 150 μm, the width of the induction coil groove is 40 μm, the length is 3.9 mm, and the thickness is 150 μm, and the coil pitch is 25 μm. This makes the magnetic core 1 thicker and the chip more sensitive. The cross-sectional area of the coil wound around the magnetic core 1 is larger, which can effectively reduce the resistance of the coil. The adjacent coil pitch can be controlled very small, and the number of coil turns can be increased in a limited space, thereby improving the detection sensitivity of the chip.

[0067] Step 240: Bond two silicon wafers to form a closed magnetic core groove and coil structure;

[0068] In this embodiment, the above bonding can be carried out by directly bonding silicon-silicon or using a polymer medium low-temperature bonding method to bond silicon wafer A and silicon wafer B to form a closed magnetic core groove and coil structure, specifically to form a closed structure of a three-dimensional solenoid coil wound around the magnetic core. The above coil structure at least includes an induction coil 2 structure and an excitation coil 3 structure. In the case where the solenoid coil groove 9 further includes multiple feedback coil grooves, the above coil structure further includes a feedback coil 4 structure.

[0069] Step 250: Cast the closed coil structure using a liquid metal casting technique to form a fluxgate coil and obtain a processed wafer;

[0070] In this embodiment, the fluxgate coil is realized by casting a liquid alloy 10, and the liquid alloy 10 is a single metal or alloy material, that is, the coil material can be a single metal or alloy material.

[0071] The liquid metal casting method can form solenoid coils in one step and in batches, with a simple process flow, a short production cycle, high coil size accuracy, and good consistency. The coil structure is flexible and controllable, and the magnetic core groove formed by the closed coil can accommodate a magnetic core 1 with a thickness of several hundred micrometers.

[0072] In some embodiments, the electrode cavity includes multiple groups of input electrode cavities and output electrode cavities, and the multiple induction coil grooves and multiple excitation coil grooves respectively correspond to a group of input electrode cavities and output electrode cavities; that is, multiple induction coil grooves correspond to a group of input electrode cavities and output electrode cavities, and multiple excitation coil grooves correspond to another group of input electrode cavities and output electrode cavities.

[0073] The closed coil structure is cast by using the liquid metal casting technology to form a fluxgate coil, and a processed wafer is obtained, including: injecting liquid alloy 10 from any one of the electrode cavities in each group of input electrode cavities and output electrode cavities, so that the liquid alloy 10 flows through the through hole 8 and the solenoid coil groove 9 and finally reaches the other electrode cavity to obtain a fluxgate coil.

[0074] In this embodiment, as Figure 5 shown, when casting, the liquid alloy 10 can be injected into the first electrode cavity 6 by introducing it from the feed channel. The liquid alloy 10 flows through the through hole 8 and the solenoid coil groove 9 and finally reaches the second electrode cavity 7. The flow of the liquid alloy 10 in the solenoid coil groove 9 is like the process of winding the magnetic core 1, with the advantage of one-step forming. Compared with the electroplating process, this production process is simple and pollution-free, and the yield of the prepared coils and through holes 8 is higher and the quality is better.

[0075] When the solenoid coil groove 9 includes multiple induction coil grooves and multiple excitation coil grooves, a closed induction coil 2 structure and a closed excitation coil 3 structure are formed. The closed induction coil 2 structure corresponds to a group of electrode cavities, and the closed excitation coil 3 structure corresponds to a group of electrode cavities. When casting, the liquid alloy 10 is injected from one of the electrode cavities corresponding to the closed induction coil 2 structure, and the liquid alloy 10 flows in the induction coil groove to form the induction coil 2; the excitation coil 3 can be obtained in a corresponding manner. When the solenoid coil groove 9 further includes multiple feedback coil grooves, the feedback coil also corresponds to a group of input electrode cavities and output electrode cavities, and the feedback coil 4 can be obtained in a corresponding manner.

[0076] The excitation coil 3, the induction coil 2 and the feedback coil 4 are all processed by liquid metal casting technology. The liquid metal casting method can form and batch manufacture the solenoid coil in one step. The process flow is simple, the production cycle is short, the coil size is high in precision and consistency. The coil structure is flexible and controllable, and the magnetic core groove formed by the coil closure can accommodate a magnetic core 1 that is several hundred microns thick. The cross-sectional area of ​​the coil processed by casting technology is much larger than the cross-sectional area of ​​the coil produced by traditional electroplating process, which can effectively reduce the resistance of the coil. The distance between adjacent coils can be controlled to be very small, and the number of coil turns can be increased in a limited space, further improving the detection sensitivity of the chip.

[0077] Step 260: Slice the processed wafer to obtain fluxgate sensor chips.

[0078] In this embodiment, the processed wafer is diced to obtain fluxgate current sensor chips processed in batches.

[0079] In the above implementation process, the magnetic core grooves, the solenoid coil grooves 9 and the through holes 8 are etched on the two silicon wafers respectively, and the electrode cavity is etched on at least one of the silicon wafers. The positions of the magnetic core grooves and the through holes 8 on the two silicon wafers correspond to each other, and the directions of the solenoid coil grooves 9 on the two silicon wafers are opposite. The electrode cavity is connected with the solenoid coil grooves 9 or the through holes 8; wherein, on each silicon wafer, the solenoid coil grooves 9 at least include a plurality of induction coil grooves and a plurality of excitation coil grooves, and the plurality of induction coil grooves and the plurality of excitation coil grooves are respectively Across the core slots, the through holes 8 are located at both ends of each induction coil slot and each excitation coil slot; an insulating layer is deposited on the surface of the core slots, the solenoid coil slots 9 and the inner surface of the through holes 8; the magnetic core 1 is placed in the core slot on one of the silicon wafers; the two silicon wafers are bonded to form a closed core slot and coil structure; the closed coil structure is cast using liquid metal casting technology to form a fluxgate coil to obtain a processed wafer; the processed wafer is diced to obtain a fluxgate sensor chip. The magnetic core 1 is placed in the core slot by embedding, without the need to slot or cut the core slot, the core structure is not limited, and the core 1 has a high degree of matching with the coil. The solenoid coil can be formed and mass-produced in one step using liquid metal casting technology. The process is simple, the production cycle is short, and the coil size is highly accurate and consistent. The coil structure is flexible and controllable, and the core slot formed by the coil closure can accommodate a core 1 several hundred microns thick. Please refer to Figure 2, as can be seen from the figure, increasing the thickness of the magnetic core 1 can effectively improve the detection sensitivity of the micro-fluxgate sensor, thus enhancing the detection sensitivity of the fluxgate sensor. Meanwhile, the cross-sectional area of the coil processed by the casting technique is much larger than that of the coil fabricated by the traditional electroplating process, which can effectively reduce the resistance of the coil. The spacing between adjacent coils can be controlled to be very small, enabling an increase in the number of coil turns within a limited space and further improving the detection sensitivity of the chip. The use of MEMS technology for batch processing, avoiding the use of electroplating technology, results in a clean and pollution-free overall chip manufacturing process, low batch production costs, and a high chip yield.

[0080] The entire process flow is simple, with a short production cycle and strong fluidity; the manufacturing process is clean and pollution-free, avoiding the use of electroplating technology for fabricating the fluxgate coil and subsequent grooving for inserting the magnetic core; the cross-sectional area of the cast coil is large, effectively reducing the resistance of the coil; the coil has high dimensional accuracy and good consistency; the structure of the magnetic core is not restricted, and the thickness of the magnetic core can be increased by an order of magnitude compared to the electroplating process, improving the detection sensitivity of the fluxgate sensor.

[0081] Figure 1 It is a schematic flow diagram of the manufacturing method of a fluxgate sensing chip in an embodiment. It should be understood that although Figure 1 the steps in the flowchart are shown in sequence according to the arrows, these steps do not necessarily have to be executed in the order indicated by the arrows. Unless explicitly stated in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in

[0082] This embodiment provides a fluxgate sensing chip, including a magnetic core 1 and two silicon wafers;

[0083] Magnetic core grooves, solenoid coil grooves 9, and through holes 8 are etched on the two silicon wafers, and electrode cavities are etched on at least one of the silicon wafers; among them, the positions of the magnetic core grooves and through holes 8 on the two silicon wafers correspond to each other, the directions of the solenoid coil grooves 9 on the two silicon wafers are opposite, and the electrode cavities communicate with the solenoid coil grooves 9; on each silicon wafer, the solenoid coil grooves 9 at least include multiple induction coil grooves and multiple excitation coil grooves, the multiple induction coil grooves and multiple excitation coil grooves respectively span the magnetic core grooves, and the through holes 8 are located at both ends of each induction coil groove and each excitation coil groove; an insulating layer is deposited on the surfaces of the magnetic core grooves, solenoid coil grooves 9, and the inner surfaces of the through holes 8;

[0084] The two silicon wafers are bonded to form a closed magnetic core groove and a coil structure, and the closed coil structure is cast by a liquid metal casting technique to form a fluxgate coil; the magnetic core 1 is located in the closed magnetic core groove.

[0085] In this embodiment, the above-processed fluxgate sensing chip can be a fluxgate current sensing chip, a fluxgate voltage sensing chip, etc.

[0086] The manufacturing method of the above fluxgate sensing chip can be used to form and mass-produce a solenoid coil in one step. The process flow is simple, the manufacturing cycle is short, the coil size accuracy is high, and the consistency is good. The coil structure is flexible and controllable. The magnetic core groove formed by the closed coil can accommodate a magnetic core 1 with a thickness of several hundred micrometers, improving the detection sensitivity of the fluxgate sensor. At the same time, the cross-sectional area of the coil processed by the casting technique is much larger than that of the coil made by the traditional electroplating process, which can effectively reduce the resistance of the coil. The distance between adjacent coils can be controlled very small, and the number of coil turns can be increased in a limited space, further improving the detection sensitivity of the chip. The chip is mass-produced by the MEMS process, and the overall manufacturing process of the chip is clean and pollution-free, with low mass-production cost and high chip yield. In some embodiments, the feedback coil 4 is directly integrated onto the chip, eliminating the need for a traditional magnetic ring structure, achieving a patch-type closed-loop detection, greatly reducing the volume and cost of the closed-loop fluxgate sensor. And the feedback coil 4 can be selected according to the actual open-loop or closed-loop detection requirements. When the feedback coil 4 is not required for open-loop detection, the feedback coil 4 can be directly used as the induction coil 2; during closed-loop detection, part of the induction coil 2 can also be directly used as the feedback coil 4.

[0087] In some embodiments, the fluxgate sensing chip includes at least two sets of excitation coils 3, one set of induction coils 2, and one set of feedback coils 4.

[0088] In this embodiment, there are at least two sets of excitation coils 3, and the connection method is reverse connection to achieve differential cancellation of the induction signals generated by the transformer effect; there is at least one set of induction coils 2, and the connection method is forward connection to achieve superposition enhancement of the induction signals generated by the magnetic field to be measured; there is at least one set of feedback coils 4, and the connection method is forward connection. The feedback coil 4 is selected according to the actual open-loop or closed-loop detection requirements.

[0089] This embodiment provides a method for detecting wire current. A fluxgate current sensing chip processed by the manufacturing method of the above fluxgate sensing chip is used for detection, including the following steps: bringing the fluxgate current sensing chip close to the wire 15 to be measured, and detecting the magnetic field generated by the wire 15 to be measured by the fluxgate current sensing chip to obtain a current detection result.

[0090] In this embodiment, the fluxgate current sensing chip fabricated by the above-mentioned method for fabricating a fluxgate sensing chip can be applied to the detection of weak currents such as various leakage currents and residual currents, and can also be applied to the detection of large currents such as battery charging and discharging currents. Please refer to Figure 6 , during the above detection, the distance between the wire under test 15 and the fluxgate current sensing chip depends on the magnitude of the current flowing through the wire under test 15. When detecting weak currents, the fluxgate current sensing chip should be as close as possible to the wire under test 15. When detecting large currents, the fluxgate current sensing chip is relatively far from the wire under test 15. By the action of the excitation coil 12 of the current sensing chip, the induction coil 13 of the current sensing chip, and the feedback coil 14 of the current sensing chip for magnetic field detection, the current result can be detected.

[0091] In some embodiments, a plurality of the fluxgate current sensing chips are respectively arranged in an array around the wire under test 15.

[0092] In this embodiment, a plurality of the above-mentioned fluxgate current sensing chips can be arranged in an array around the wire under test 15 to achieve more accurate measurement. For example, when using dual-chip detection, two fluxgate current sensing chips are symmetrically attached to both sides of the current-carrying wire under test, as Figure 7 shown, Figure 7 is a schematic diagram of dual-chip sensing. The magnetic field directions 17 measured by the two fluxgate current sensing chips are opposite, forming magnetic force lines 16. By using a suitable differential algorithm, the noise signals generated by external interference magnetic fields can be effectively eliminated, and the anti-electromagnetic interference ability of the fluxgate current sensor can be improved.

[0093] In the above implementation process, the fluxgate current sensing chip fabricated by the above-mentioned method for fabricating a fluxgate sensing chip can be integrated, improving the application portability and flexibility, having strong anti-interference ability, and broadening the application scenarios.

[0094] In some embodiments, the step of bringing the fluxgate current sensing chip close to the wire under test and detecting the magnetic field generated by the wire under test by the fluxgate current sensing chip to obtain a current detection result includes: bringing the fluxgate current sensing chip close to the wire under test and performing a patch-type closed-loop detection by the fluxgate current sensing chip to detect the magnetic field generated by the wire under test to obtain a current detection result.

[0095] Among them, when the fluxgate current sensing chip does not include a feedback coil, during closed-loop detection, some induction coils can also be directly used as feedback coils, that is, the patch-type closed-loop detection performed by the fluxgate current sensing chip includes: multiplexing some induction coils in the fluxgate current sensing chip as feedback coils for patch-type closed-loop detection.

[0096] Wherein, when the fluxgate current sensing chip includes a feedback coil, the patch-type closed-loop detection performed by the fluxgate current sensing chip includes: directly using the feedback coil of the fluxgate current sensing chip for patch-type closed-loop detection.

[0097] In the above implementation process, when applying the fluxgate current sensing chip for closed-loop detection, there is no need for a magnetic ring. The feedback coil is directly integrated on the fluxgate current sensing chip, eliminating the need for the traditional magnetic ring structure, achieving patch-type closed-loop control, reducing the volume of the sensor, and lowering the production cost.

[0098] It should also be noted that the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, commodity or device including the element.

[0099] The above are only embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A method for manufacturing a fluxgate sensor chip, characterized in that: include: A magnetic core groove, a solenoid coil groove and a through hole are respectively etched on two silicon wafers, and an electrode cavity is etched on at least one of the silicon wafers, the magnetic core grooves and the through hole on the two silicon wafers are located in corresponding positions, the solenoid coil grooves on the two silicon wafers are in opposite directions, and the electrode cavity is connected to the solenoid coil groove; wherein, on each silicon wafer, the solenoid coil grooves at least include a plurality of induction coil grooves and a plurality of excitation coil grooves, the plurality of induction coil grooves and the plurality of excitation coil grooves respectively span the magnetic core grooves, and the through holes are located at both ends of each induction coil groove and each excitation coil groove; Depositing an insulating layer on the surface of the magnetic core slot, the solenoid coil slot and the inner surface of the through hole; The magnetic core is placed in a magnetic core slot on one of the silicon wafers; Bonding two silicon wafers to form a closed magnetic core slot and coil structure; The closed coil structure is casted by liquid metal casting technology to form a fluxgate coil, thereby obtaining a processed wafer; The processed wafer is diced to obtain a fluxgate sensor chip.

2. The method for manufacturing a fluxgate sensor chip according to claim 1, characterized in that: The solenoid coil slot also includes a plurality of feedback coil slots; each feedback coil slot spans across the magnetic core slot, and through holes are provided at both ends of each feedback coil slot.

3. The method for manufacturing a fluxgate sensor chip according to claim 1, characterized in that: The electrode cavity comprises a plurality of groups of input electrode cavities and output electrode cavities, and the plurality of induction coil slots and the plurality of excitation coil slots correspond to a group of input electrode cavities and an output electrode cavity respectively; The method of using liquid metal casting technology to cast the closed coil structure to form a fluxgate coil to obtain a processed wafer includes: Liquid alloy is injected into any electrode cavity of each group of input electrode cavity and output electrode cavity, so that the liquid alloy flows through the through hole and the solenoid coil slot and finally reaches the other electrode cavity to obtain a fluxgate coil.

4. The method for manufacturing a fluxgate sensor chip according to claim 1, characterized in that: The magnetic core is a film structure produced by strip processing, and the thickness of the magnetic core is tens to hundreds of microns.

5. The method for manufacturing a fluxgate sensor chip according to claim 1, characterized in that: The magnetic core is in any one of the structures of racetrack, rectangle, triangle and ring.

6. A fluxgate sensor chip, characterized in that: It includes a magnetic core and two silicon wafers; The two silicon wafers are etched with magnetic core grooves, solenoid coil grooves and through holes, and at least one of the silicon wafers is etched with an electrode cavity; wherein the positions of the magnetic core grooves and the through holes on the two silicon wafers correspond to each other, the directions of the solenoid coil grooves on the two silicon wafers are opposite, and the electrode cavity is connected with the solenoid coil grooves; on each silicon wafer, the solenoid coil grooves at least include a plurality of induction coil grooves and a plurality of excitation coil grooves, the plurality of induction coil grooves and the plurality of excitation coil grooves respectively span the magnetic core grooves, and the through holes are located at both ends of each induction coil groove and each excitation coil groove; an insulating layer is deposited on the surface of the magnetic core groove, the solenoid coil groove and the inner surface of the through hole; The two silicon wafers are bonded to form a closed magnetic core slot and a coil structure, and the closed coil structure is cast by liquid metal casting technology to form a fluxgate coil, and the magnetic core is located in the closed magnetic core slot.

7. The fluxgate sensor chip according to claim 6, characterized in that: The fluxgate sensor chip includes at least two groups of excitation coils, one group of induction coils and one group of feedback coils.

8. A method for detecting current in a conductor, characterized in that: The method for manufacturing a fluxgate current sensor chip according to any one of claims 1 to 5 is used to manufacture a fluxgate current sensor chip for detection, comprising the following steps: The fluxgate current sensor chip is placed close to the conductor to be tested, and the fluxgate current sensor chip detects the magnetic field generated by the conductor to be tested to obtain a current detection result.

9. The wire current detection method according to claim 8, characterized in that: There are multiple fluxgate current sensor chips, and the multiple fluxgate current sensor chips are arrayed around the wire to be measured.

10. The wire current detection method according to claim 8, characterized in that: The method of placing the fluxgate current sensor chip close to the conductor to be tested and detecting the magnetic field generated by the conductor to be tested by the fluxgate current sensor chip to obtain a current detection result includes: The fluxgate current sensor chip is placed close to the conductor to be tested, and the fluxgate current sensor chip performs patch-type closed-loop detection to detect the magnetic field generated by the conductor to be tested to obtain a current detection result.

11. The wire current detection method according to claim 10, characterized in that: The patch-type closed-loop detection performed by the fluxgate current sensor chip includes: Part of the induction coils in the fluxgate current sensor chip are reused as feedback coils for patch-type closed-loop detection.

12. The wire current detection method according to claim 10, characterized in that: The fluxgate current sensor chip includes a feedback coil; The patch-type closed-loop detection performed by the fluxgate current sensor chip includes: The feedback coil of the fluxgate current sensor chip is directly used to perform patch-type closed-loop detection.

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