Z-axis magnetic field sensor with built-in magnetic foil and manufacturing method

Abstract

The invention discloses a Z-axis magnetic field sensor with a built-in magnetic foil and a manufacturing method thereof, and mainly solves the technical problem that the existing Z-axis sensor prepared based on an electroplating process is complex in process. The magnetic resistance detection part is used for detecting an X-direction or Y-direction magnetic field and is arranged on a sensor substrate; the conductive part is arranged on one side of the magnetic resistance detection part and is used for being correspondingly and electrically connected with an external detection circuit; the magnetic shielding layer is correspondingly connected to the other side of the magnetic resistance detection part through a bonding layer; the magnetic resistance detection part and the plastic package part are arranged outside the conductive part; and the magnetic shielding layer is a magnetic foil / belt of which the XY plane area is smaller than the packaging area of the plastic packaging part corresponding to the XY plane. The magnetic foil / belt prepared by a non-electroplating process is used as the shielding layer, so that compared with an existing sensor formed by an electroplating process, the process complexity can be greatly reduced, and the manufacturing efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a Z-axis magnetic field sensor with built-in magnetic foil and a manufacturing method. BACKGROUND

[0002] The Z-axis magnetic field sensor refers to a magnetic sensor for measuring the magnetic field perpendicular to the plane direction, which is mainly divided into Hall effect, magnetoresistive (such as AMR, GMR, TMR) and other types. However, the detection accuracy of the Hall effect magnetic field sensor is limited, and the detection accuracy of the magnetoresistive sensor is higher, but it can only detect the magnetic field in the X and Y directions, and cannot be directly used to detect the magnetic field in the Z direction. Therefore, a magnetic field conversion structure made of soft magnetic material such as NiFe is usually used to convert the Z-direction magnetic field into the magnetic field in the XY plane, and then the magnetic field strength in the X or Y direction is measured to indirectly obtain the magnetic field strength information in the Z direction. Among them, when the magnetic field conversion structure converts the Z-direction magnetic field into the magnetic field in the XY plane, the original magnetic field in the XY plane will cause adverse interference to the measurement of the Z-direction magnetic field, therefore, appropriate means need to be taken to shield the original magnetic field in the XY plane.

[0003] The inventor knows a kind of magnetic sensor using first soft magnetic material to shield XY magnetic field, while using second soft magnetic material to convert Z-direction magnetic field into XY magnetic field, and then using MR element to measure magnetic field. Among them, the first soft magnetic material and the second soft magnetic material are prepared by semiconductor front process and / or back process.

[0004] The inventor found in long-term practice and research that whether using semiconductor front process or back process, there is an electroplating process, and the electroplating process is an electrochemical process of depositing a metal layer on the surface of a substrate, which requires special electroplating tank, electroplating liquid and other production equipment and consumables, and the production process is complex and not easy to operate.

[0005] The information disclosed in this BACKGROUND section is only for the purpose of enhancing the understanding of the background of the present disclosure and should not be considered as admitting or in any form implying that this information constitutes prior art known to those skilled in the art. SUMMARY

[0006] In view of at least one of the above technical problems, the present disclosure provides a Z-axis magnetic field sensor with built-in magnetic foil and a manufacturing method, which mainly solves the technical problem of complex process of the existing Z-axis sensor prepared based on electroplating process.

[0007] According to one aspect of the present disclosure, a Z-axis magnetic field sensor with built-in magnetic foil is provided, which comprises a magnetic field conversion unit for converting a Z-direction magnetic field into an X-direction or Y-direction magnetic field, a magnetoresistance detection unit for detecting the X-direction or Y-direction magnetic field and arranged at a sensor substrate, a conductive unit arranged at one side of the magnetoresistance detection unit for corresponding electrical connection with external detection circuit, a magnetic shielding layer corresponding connected to the other side of the magnetoresistance detection unit through an adhesive layer, and a plastic encapsulation unit encapsulating the magnetic shielding layer, the magnetoresistance detection unit and the conductive unit; the magnetic shielding layer is a magnetic foil / band with an XY plane area smaller than a corresponding XY plane encapsulation area of the plastic encapsulation unit.

[0008] In some embodiments of the present disclosure, the conductive unit comprises a Bump layer, an RDL layer and a Pad layer arranged in sequence from near to far at the corresponding side of the magnetoresistance detection unit.

[0009] In some embodiments of the present disclosure, the minimum distance between the bottom surface of the magnetic shielding layer and the magnetoresistance detection unit is less than 1 / 2 of the thickness of the magnetic shielding layer.

[0010] In some embodiments of the present disclosure, the thickness tolerance of the magnetic foil / band is not greater than ±2 μm.

[0011] In some embodiments of the present disclosure, the magnetic foil / band is an amorphous foil / band or a nanocrystalline foil / band.

[0012] In some embodiments of the present disclosure, the magnetic foil / band is an amorphous foil / band or a nanocrystalline foil / band containing Fe, Si and B elements.

[0013] In some embodiments of the present disclosure, the amorphous foil / band is a high-entropy or medium-entropy amorphous foil / band.

[0014] In some embodiments of the present disclosure, the component composition of the nanocrystalline foil / band comprises Fe, Si, B, P and Cu.

[0015] According to another aspect of the present disclosure, a manufacturing method of the above-mentioned Z-axis magnetic field sensor with built-in magnetic foil is provided, which comprises the following steps: (1) based on a front-end process, a magnetic field conversion unit, a magnetoresistance detection unit, an electroplated shielding unit and a Bump layer are fabricated on the surface of a semiconductor wafer; (2) after back-grinding of the semiconductor wafer based on a back-end process, the wafer is cut to obtain each sensor chip unit; and after positioning and placing each sensor chip unit based on the back-end process, a first plastic encapsulation body is obtained by unified injection molding of each sensor chip unit; (3) the corresponding side of the first plastic encapsulation body is grinded until the Bump layer is exposed; (4) After the RDL layer and the Pad layer are sequentially made above the exposed bump layer, a second plastic package is obtained by re-plastic packaging; (5) The corresponding side of the second plastic package is ground until the Pad layer is exposed; (6) The second plastic package is inverted, and the back of the second plastic package is ground until each sensor substrate is ground to the designed thickness; (7) The magnetic foil / band is bonded above the exposed surface of the sensor substrate; (8) According to the corresponding relationship with each sensor chip, the magnetic foil / band is etched to an area smaller than the cross-sectional area of the corresponding sensor package; (9) The range above the bonding layer is plastic packaged to enclose the magnetic foil / band; (10) After being cut, each Z-axis magnetic field sensor is obtained.

[0016] One or more technical solutions provided in the embodiments of the present application have at least any of the following technical effects or advantages: 1. The technical bias is overcome, and the magnetic foil / band prepared by the non-electroplating process is used as the magnetic shielding layer, which can effectively solve the problem of complex and low efficiency of the traditional electroplating process, and also improve the magnetic shielding ability of the sensor and expand the detection range of the Z-axis magnetic field through the magnetic foil.

[0017] 2. The amorphous or nanocrystalline magnetic foil can be prepared in advance, and the bonding process is simple and convenient, which can effectively improve the production efficiency of the sensor, and also compensate for the PCB thermal expansion and contraction stress conducted by the sensor arranged on the PCB substrate, and improve the structural strength of the sensor. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a perspective view of a Z-axis magnetic field sensor with a built-in magnetic foil according to an embodiment of the present application.

[0019] Figure 2 FIG. 2 is another perspective view of the Z-axis magnetic field sensor with a built-in magnetic foil according to an embodiment of the present application.

[0020] Figure 3 FIG. 3 is a three-view diagram of the Z-axis magnetic field sensor with a built-in magnetic foil according to an embodiment of the present application.

[0021] Figure 4 FIG. 4 is a preparation flowchart of the Z-axis magnetic field sensor with a built-in magnetic foil according to an embodiment of the present application.

[0022] In the above figures, 10 is a magnetic field conversion part, 11 is a magnetic resistance detection part, 21 is a Bump layer, 22 is an RDL layer, 23 is a Pad layer, 3 is a plastic sealing part, 4 is a magnetic shielding layer, and 5 is an adhesive layer. DETAILED DESCRIPTION

[0023] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer", "vertical", "horizontal", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0024] In the following examples, the industrial raw materials involved, unless otherwise specified, are commercially available conventional industrial raw materials; the processing and manufacturing methods involved, unless otherwise specified, are conventional methods.

[0025] In order to better understand the technical solutions of the present application, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0026] The magnetic layer of the existing Z-axis magnetic field sensor is prepared by electroplating process of soft magnetic material. However, the production cycle of electroplating process is long, and it takes several hours to obtain a few tens of microns of magnetic layer, thereby reducing the production efficiency. Moreover, the electroplating process is relatively complex, and special equipment and consumables are needed, which seriously reduces the economic benefit. To solve the above problems, the present example discloses a Z-axis magnetic field sensor with built-in magnetic foil, as shown in Figure 1 In the present example, the Z-axis magnetic field sensor includes a magnetic resistance detection part 11 arranged on a sensor substrate. The sensor substrate can be made of Si, Al2O3, quartz glass, AlTiC, etc., which serves to support the magnetic resistance detection part and other structures. The magnetic resistance detection part 11 includes a Wheatstone bridge (full bridge or half bridge) composed of a plurality of magnetic resistance elements connected in series or parallel. In the present embodiment, the magnetic resistance element is one of TMR, GMR, and AMR. However, the magnetic resistance detection part 11 cannot directly detect the magnetic field in the Z-axis direction. Therefore, in the present example, a magnetic field conversion part 10 is provided to convert the Z-direction magnetic field into an X-direction or Y-direction magnetic field that can be detected by the magnetic resistance element, thereby indirectly detecting the Z-direction magnetic field by the magnetic resistance detection part.

[0027] In addition, in order to realize effective transmission of the electrical signal of the detection information at the magnetic resistance detection part 11 to the outside world, in the present example, a conductive part is arranged on one side of the magnetic resistance detection part 11. Specifically, as shown in Figures 1 to 3, the conductive part is sequentially provided with a bump layer 21, an RDL layer 22 and a pad layer 23 from the side of the magnetoresistance detection part 11 to the side far from the magnetoresistance detection part 11. The bump layer 21 is a metal cylinder plated on the surface of the magnetoresistance detection part to provide an interface for electrical connection between the outside and the magnetoresistance detection part. The number of the metal cylinders is the same as the number of the soldering points of the magnetoresistance detection part, and the metal cylinders are arranged at the positions of the soldering points and electrically connected to the soldering points, so as to transmit the signals sensed by the magnetoresistance detection part to the outside. In addition, the RDL layer 22 is used to realize the electrical connection inside the chip, and the pad layer 23 includes a number of pads matching the number of the metal cylinders in the bump layer 21, which are used to realize the physical connection and current conduction between the corresponding pins of the chip and the external circuit. The RDL layer 22 is arranged between the bump layer 21 and the pad layer 23 to realize the electrical connection between the corresponding metal cylinders and the pads, so as to allow the redistribution of the positions of the pads without being vertically coincident with the metal cylinders, thereby optimizing the structure of the chip and facilitating the connection of the chip. In the embodiment, the bump layer 21, the RDL layer 22 and the pad layer 23 are made of a metal material (such as Cu) with good electrical conductivity. Figure 1 In the example, the Z-axis magnetic field sensor includes four pads, four RDLs and four bumps. In addition, referring to Figure 1 The detection module is further coated with a plastic sealing part 3 to isolate the external environment, prevent the chip from being corroded and the like, ensure the stability and reliability of the chip, and form a stable protective layer after the plastic sealing layer is solidified to isolate different circuit elements and achieve a certain heat conduction effect.

[0028] To avoid the adverse interference of the X-direction and / or Y-direction magnetic field on the detection of the Z-direction magnetic field, the Z-axis magnetic field sensor further includes a shielding module. In the embodiment, the shielding module includes a plated shielding part arranged on the side of the conductive part corresponding to the magnetoresistance detection part. The plated shielding part is made of a plating process and has a magnetic shielding effect on the side. In addition, a magnetic shielding layer 4 is arranged on the side of the magnetoresistance detection part different from the plated shielding part, referring to Figure 3 The magnetic shielding layer 4 is specifically a magnetic foil / belt with an area smaller than the packaging area of the plastic sealing part in the XY plane.

[0029] Specifically, the magnetic shielding layer 4 can be an amorphous foil prepared by a melt quenching method, or a nanocrystalline foil obtained by further crystallization treatment of the amorphous foil, or a silicon steel foil or a permalloy foil prepared by a multi-pass rolling process. In the embodiment, the magnetic shielding layer 4 is an amorphous strip prepared by the melt quenching method with a thickness tolerance of ±2 μm. Since the thickness of the amorphous or nanocrystalline strip is uniform, the magnetic shielding effect is excellent and the performance consistency between different samples is strong, so that a series of problems such as long preparation period, uncontrollable plating layer thickness and large internal stress of the magnetic layer prepared by the existing plating method can be effectively solved.

[0030] Thus, by setting the magnetic foil / belt as the magnetic shielding layer, the external X-direction and / or Y-direction magnetic field can be effectively shielded; at the same time, the rigidity of the sensor can be effectively increased by the rigidity of the magnetic foil / belt, thereby reducing the breakage rate of the sensor and improving the strength of the sensor. In addition, since the PCB substrate has a relatively large area, when the ambient temperature changes, the PCB substrate is easily affected by the temperature and expands and shrinks, and the sensor is fixedly welded on the surface of the PCB substrate, so when the PCB substrate expands and shrinks, the stress is transmitted to the sensor, affecting the structural strength of the sensor. Therefore, by setting the magnetic foil / belt with a certain rigidity, the stress generated due to the thermal expansion and contraction of the PCB substrate can be reasonably compensated.

[0031] In addition, in the present embodiment, the area of the magnetic foil / belt in the XY plane is smaller than the area of the cross section of the XY plane corresponding to the Z-axis magnetic sensor, so that the magnetic shielding effect can be ensured while avoiding corrosion caused by direct exposure of the magnetic foil / belt to the air.

[0032] In addition, in order to realize the connection between the magnetic shielding layer 4 and the chip corresponding to the magnetoresistance detection part, referring to Figure 1 In the present embodiment, an adhesive layer 5 is arranged between the magnetic shielding layer and the magnetoresistance detection part, and in the present embodiment, the adhesive layer 5 is used to realize the adhesion between the chip corresponding to the magnetoresistance detection part and the magnetic shielding layer. The adhesion of the magnetic shielding layer is realized by the adhesive layer, which has the advantages of fast preparation, low cost and simple operation compared with the traditional electroplating process for preparing the magnetic material, and at the same time, the problem of excessive internal stress and breakage caused by the excessive thickness of the electroplating layer can be avoided. In addition, since the adhesive layer is directly adhered to the sensor substrate and the plastic encapsulation part, the adhesion strength of the magnetic shielding layer is ensured.

[0033] In order to ensure the magnetic shielding effect of the magnetic shielding layer, in the present embodiment, the minimum distance between the bottom surface of the magnetic shielding layer, i.e. the magnetic foil / belt, and the magnetoresistance detection part is less than 1 / 2 of the thickness of the magnetic foil / belt. Thus, the maximum distance between the magnetic foil / belt and the magnetoresistance detection part is limited, thereby avoiding the problem of weakening of the magnetic shielding effect caused by excessive distance between the two.

[0034] In the embodiment, the magnetic shielding layer is specifically an amorphous or nanocrystalline foil / tape containing Fe, Si and B, which is relatively easy to prepare and has relatively low cost. In addition, the inventors have found in long-term practice and research that, in order to improve the soft magnetic properties of the amorphous foil / tape, stress relief annealing needs to be performed, but the ordinary amorphous foil / tape will become brittle after the stress relief annealing operation. Therefore, in the embodiment, the amorphous foil is etched into the required shape by etching, thereby eliminating the edge collapse phenomenon in the traditional cutting process. Further, in the embodiment, the amorphous foil / tape is a high-entropy amorphous foil / tape that does not become brittle after stress relief annealing, such as an amorphous foil / tape designed to add not less than 5 elements of Fe, Co, Ni, Si and B. In other embodiments, the amorphous foil / tape is a medium-entropy amorphous foil / tape. In addition, in the embodiment, the nanocrystalline foil contains Fe, Si, B, P and Cu elements, and has the advantages of high saturation magnetic strength, small coercivity and excellent magnetic shielding effect. In order to further improve the soft magnetic properties of the nanocrystalline foil, the magnetic foil / tape is also heat treated by rapid annealing in the embodiment. Specifically, the magnetic foil / tape is heated to a suitable crystallization temperature (the first crystallization peak Tx1 of the magnetic foil is obtained by DSC technology, and the suitable crystallization temperature is generally before Tx1) at a heating rate of 40K / s, and is maintained for a short time (within 5 minutes), so as to promote the nucleation of nanocrystalline and inhibit the growth of nanocrystalline, thereby obtaining a nanocrystalline magnetic foil with fine nanocrystalline grains.

[0035] In addition, the embodiment also discloses a preparation method of the Z-axis magnetic field sensor with the built-in magnetic foil. Figure 4 , and specifically includes the following steps: (1) Based on the front-end process, a magnetic field conversion part, a magnetic resistance detection part, an electroplating shielding part and a Bump layer are prepared on the surface of the semiconductor wafer.

[0036] The front-end process mainly constructs various device structures on the surface of the semiconductor wafer through sputtering, photolithography, etching and other technical steps. In the embodiment, the semiconductor front-end process is used to prepare a plurality of magnetic resistance detection parts on the surface of the semiconductor wafer, as shown in Figure 4 (a) First, the magnetic resistance detection part and the insulating layer for protection are prepared on the wafer surface at the sensor substrate, and then, as shown in Figure 4 (b) The electroplating shielding layer is prepared on the upper surface of the magnetic resistance detection part by using the electroplating process, and finally, as shown in Figure 4 (c) After the electroplating shielding layer is prepared, the Bump layer corresponding to the electrical connection of each magnetic resistance element in the chip is prepared at the chip connection point by using the front-end process, that is, each copper column in the Bump layer.

[0037] (2) After the back surface of the semiconductor wafer is grinded based on the subsequent process, the wafer is cut to obtain each sensor chip unit; and after each sensor chip unit is positioned and placed based on the subsequent process, each sensor chip unit is uniformly injection molded to obtain a first plastic package.

[0038] To avoid the wafer from being broken due to being too thin, the wafer has a certain thickness in the front-end process, and needs to be grinded first after entering the subsequent process until the required wafer thickness is obtained; after the wafer back surface grinding process is completed, the wafer is laminated and cut to obtain each sensor chip unit containing a magnetic resistance detection part and a Bump layer. Then each sensor chip unit is positioned and placed based on the subsequent process, and each sensor chip unit is uniformly injection molded, see Figure 4 (d), and then a first plastic package is obtained.

[0039] (3) To make an RDL layer and ensure effective contact between the RDL layer and the Bump layer, the corresponding side of the Bump layer close to the sensor chip of the first plastic package is grinded, see Figure 4 (e), until the Bump layer is exposed.

[0040] (4) After the RDL layer and the Pad layer are made in sequence above the exposed Bump layer, the second plastic package is obtained by re-molding.

[0041] (5) The corresponding side of the second plastic package close to the Pad layer of the sensor chip is grinded, see Figure 4 (f), until the Pad layer is exposed.

[0042] (6) Since the sensor substrate has a certain thickness, which affects the volume of the sensor chip, therefore, see Figure 4 (g), the second plastic package is inverted, see Figure 4 (h), the back surface of the second plastic package is grinded until the thickness of each sensor chip substrate is reduced to the designed thickness.

[0043] (7) see Figure 4 (i), the magnetic foil / tape is correspondingly attached above the exposed surface of the sensor substrate, and the adhesion of the adhesion layer is correspondingly enhanced by using appropriate heat treatment or UV light irradiation.

[0044] (8) According to the corresponding relationship with each sensor chip, the magnetic foil / tape is etched by a chemical etching method, see Figure 4 (j), so that the area of the magnetic foil / tape is smaller than the cross-sectional area of the corresponding sensor package.

[0045] (9) see Figure 4 (k), the range above the adhesion layer is molded to seal the magnetic foil / tape.

[0046] (10) see Figure 4 (l) and Figure 4 (m), corresponding to each Z-axis magnetic field sensor obtained after cutting.

[0047] While certain preferred embodiments of the application have been described, those skilled in the art will recognize that many modifications and variations of this application are possible. Therefore, it is intended that the appended claims shall cover all such modifications and variations as fall within the true spirit and scope of the invention.

[0048] Obviously, numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore intended that the disclosure be construed as including all such modifications and variations as fall within the scope of the applicant's contribution to the art.

Claims

1. A Z-axis magnetic field sensor with built-in magnetic foil, characterized by, The application relates to a Z-axis magnetic field sensor, which comprises a magnetic field conversion unit for converting a Z-axis magnetic field into an X-axis or Y-axis magnetic field, a magnetic resistance detection unit for detecting the X-axis or Y-axis magnetic field and arranged at a sensor substrate, a conductive unit arranged at one side of the magnetic resistance detection unit and electrically connected to an external detection circuit, a magnetic shielding layer connected to the other side of the magnetic resistance detection unit through an adhesive layer, and a plastic sealing unit covering the magnetic shielding layer, the magnetic resistance detection unit and the conductive unit; the magnetic shielding layer is a magnetic foil / band with an XY plane area smaller than the corresponding XY plane packaging area of the plastic sealing unit.

2. The Z-axis magnetic field sensor of claim 1, wherein, The conductive unit comprises a bump layer, an RDL layer and a pad layer arranged in sequence at the corresponding side of the magnetic resistance detection unit.

3. The Z-axis magnetic field sensor of claim 1, wherein, The minimum distance between the bottom surface of the magnetic shielding layer and the magnetic resistance detection unit is smaller than 1 / 2 of the thickness of the magnetic shielding layer.

4. The Z-axis magnetic field sensor of claim 1, wherein, The thickness tolerance of the magnetic foil / band is not greater than + / - 2 microns.

5. The Z-axis magnetic field sensor of claim 1, wherein, The magnetic foil / band is an amorphous foil / band or a nanocrystalline foil / band.

6. The Z-axis magnetic field sensor of claim 5, wherein, The magnetic foil / band is an amorphous foil / band or a nanocrystalline foil / band containing Fe, Si and B elements.

7. The Z-axis magnetic field sensor of claim 5, wherein, The amorphous foil / band is a high-entropy or medium-entropy amorphous foil / band.

8. The Z-axis magnetic field sensor of claim 7, wherein, The component composition of the nanocrystalline foil / band comprises Fe, Si, B, P and Cu.

9. A method of manufacturing the Z-axis magnetic field sensor with a built-in magnetic foil according to claim 1, characterized by, The application further relates to a manufacturing method of the Z-axis magnetic field sensor. (1) A semiconductor wafer surface is processed based on a previous process to form a magnetic field conversion unit, a magnetic resistance detection unit, a plated shielding unit and a bump layer; (2) After back grinding of the semiconductor wafer based on a subsequent process, the wafer is cut to obtain sensor chip units; The sensor chip units are uniformly injection molded after being positioned and placed based on the subsequent process, and a first plastic sealing body is obtained; (3) The first plastic sealing body is ground on the corresponding side until the bump layer is exposed; (4) An RDL layer and a pad layer are sequentially formed above the exposed bump layer, and a second plastic sealing body is obtained after re-molding; (5) The second plastic sealing body is ground on the corresponding side until the pad layer is exposed; (6) The second plastic sealing body is inverted, and the back surface of the second plastic sealing body is ground until the sensor substrates are ground to the designed thickness; (7) A magnetic foil / band is adhered above the exposed surface of the sensor substrate; (8) According to the corresponding relationship with each sensor chip, the magnetic foil / band is etched to have an area smaller than the packaging cross-sectional area of the sensor; (9) The range above the adhesive layer is molded to seal the magnetic foil / band; (10) Each Z-axis magnetic field sensor is obtained after cutting.

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