A filter, a manufacturing method thereof, and an electronic device

Abstract

The application relates to the technical field of filters, in particular to a filter and a manufacturing method thereof and electronic equipment. The filter comprises a main body and an inner electrode. The main body comprises a first magnetic ferrite layer, a first non-magnetic ferrite layer and a second magnetic ferrite layer which are sequentially stacked. The inner electrode is arranged in the first non-magnetic ferrite layer. The material of the first magnetic ferrite layer, the second magnetic ferrite layer and the first non-magnetic ferrite layer at least contains Ni elements and Zn elements. The molar ratio n(Ni) : n(Zn) of the Ni elements and the Zn elements in the first non-magnetic ferrite layer is r1, the molar ratio n(Ni) : n(Zn) of the Ni elements and the Zn elements in the first magnetic ferrite layer is r2, and the molar ratio n(Ni) : n(Zn) of the Ni elements and the Zn elements in the second magnetic ferrite layer is r3, r1 < r2, and r1 < r3, so that the filter has good co-firing matching, and the reliability of the filter is improved.

Description

Technical Field

[0001] This application relates to the field of filter technology, and in particular to a filter and its manufacturing method, as well as an electronic device. Background Technology

[0002] When the filter body is composed of different material layers, the poor co-firing matching between the different material layers leads to more structural defects such as cracking, deformation, and delamination after sintering, which is not conducive to improving the reliability of the filter. Summary of the Invention

[0003] This application discloses a filter and its manufacturing method, as well as an electronic device, which can reduce structural defects after filter sintering.

[0004] To achieve the above objectives, in a first aspect, embodiments of this application disclose a filter, comprising: The main body comprises a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer stacked sequentially; and An inner electrode is disposed within the first non-magnetic ferrite layer; The materials of the first magnetic ferrite layer, the second magnetic ferrite layer, and the first non-magnetic ferrite layer contain at least Ni and Zn elements; the molar ratio of Ni to Zn in the first non-magnetic ferrite layer is r1, the molar ratio of Ni to Zn in the first magnetic ferrite layer is r2, and the molar ratio of Ni to Zn in the second magnetic ferrite layer is r3, satisfying the following relationship: r1 < r2, and r1 < r3. In a possible implementation of the first aspect, r1 and r2 also satisfy the following relationship: r2 / r1 = 84~286; and / or, r3 / r1 = 84~286.

[0005] In a possible implementation of the first aspect, r1 is 0.007 to 0.0237.

[0006] In a possible implementation of the first aspect, r2 > 1; and / or, The r3>1.

[0007] In one possible implementation of the first aspect, the material of the first magnetic ferrite layer and the second magnetic ferrite layer further includes Bi element, and the molar percentage of Bi element is 0.13 mol% to 0.31 mol%.

[0008] In one possible implementation of the first aspect, the filter further includes a magnetic core column that penetrates the first non-magnetic ferrite layer along its thickness direction. The two ends of the magnetic core column are respectively connected to the first magnetic ferrite layer and the second magnetic ferrite layer to form a magnetic core, and the inner electrode is wound around the central axis of the magnetic core column.

[0009] In a possible implementation of the first aspect, the longitudinal cross-sectional shape of the magnetic core post is trapezoidal or square; and / or, The magnetic core, the first magnetic ferrite layer, and the second magnetic ferrite layer are made of the same material.

[0010] In a possible implementation of the first aspect, the inner electrode is a planar spiral coil, and there are multiple planar spiral coils, which are spaced apart along the thickness direction of the first non-magnetic ferrite layer. The plurality of planar spiral coils are divided into at least two groups, each group of planar spiral coils includes a plurality of planar spiral coils connected in series, and the planar spiral coils in the same group are symmetrically distributed.

[0011] In a possible implementation of the first aspect, along the thickness direction of the first non-magnetic ferrite layer, the distance D1 between the first magnetic ferrite layer and the nearest inner electrode is 28 μm ≤ D1 ≤ 50 μm; and / or, Along the thickness direction of the first non-magnetic ferrite layer, the distance between the second magnetic ferrite layer and the nearest inner electrode is D2, where 28 μm ≤ D2 ≤ 50 μm.

[0012] In a possible implementation of the first aspect, the subject further includes: A second non-magnetic ferrite layer is disposed on the side of the first magnetic ferrite layer opposite to the first non-magnetic ferrite layer; and The third non-magnetic ferrite layer is disposed on the side of the second magnetic ferrite layer opposite to the first non-magnetic ferrite layer.

[0013] In one possible implementation of the first aspect, the first non-magnetic ferrite layer, the second non-magnetic ferrite layer, and the third non-magnetic ferrite layer are made of the same material.

[0014] In a possible implementation of the first aspect, the subject further includes: A first transition layer is disposed between the first magnetic ferrite layer and the first non-magnetic ferrite layer; and A second transition layer is disposed between the second magnetic ferrite layer and the first non-magnetic ferrite layer. The first transition layer and the second transition layer are both made of non-magnetic ferrite.

[0015] In one possible implementation of the first aspect, the main body has a symmetrical structure, and the axis of symmetry of the main body is the centerline of the main body along the thickness direction of the first non-magnetic ferrite layer.

[0016] Secondly, embodiments of this application disclose a method for manufacturing a filter, comprising the following steps: Fabrication of magnetic ferrite tapes; Fabrication of nonmagnetic ferrite raw tapes; Fabrication of internal electrodes: The internal electrodes are fabricated on a portion of the non-magnetic ferrite green tapes to obtain internal electrode green tapes; Fabrication of the main body: The non-magnetic ferrite green tape, the magnetic ferrite green tape, and the inner electrode green tape are stacked in a preset order to obtain a main body semi-finished product; the main body semi-finished product is sintered to obtain the main body; wherein, the main body includes a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer stacked in sequence, the inner electrode is disposed in the first non-magnetic ferrite layer, and the materials of the first magnetic ferrite layer, the second magnetic ferrite layer, and the first non-magnetic ferrite layer contain at least Ni and Zn elements; the molar ratio of Ni to Zn in the first non-magnetic ferrite layer, n(Ni):n(Zn), is r1; the molar ratio of Ni to Zn in the first magnetic ferrite layer, n(Ni):n(Zn), is r2; the molar ratio of Ni to Zn in the second magnetic ferrite layer, n(Ni):n(Zn), is r3, satisfying the following relationship: r1 < r2, and r1 < r3.

[0017] In a possible implementation of the second aspect, the step of fabricating the nonmagnetic ferrite strip includes the following sub-steps: Preparation of the nonmagnetic ferrite material: The raw materials for the nonmagnetic ferrite material are weighed according to the following molar percentages: 35.04 mol%~44.97 mol% zinc oxide, 0.32 mol%~0.83 mol% nickel oxide, 7.66 mol%~9.42 mol% copper oxide, and 47.05 mol%~54.71 mol% ferric oxide; the raw materials for the nonmagnetic ferrite material are mixed with grinding balls and water, and then ground to obtain a first powder with a particle size of 0.5 μm~1 μm; the first powder is dried and then pre-fired at a temperature of 800℃~850℃ for 1 hour~2 hours; the pre-fired first powder is mixed with grinding balls and water and ground to a particle size of 0.2 μm~0.6 μm, and then dried to obtain the nonmagnetic ferrite material; Preparation of nonmagnetic ferrite slurry: The nonmagnetic ferrite material is mixed with an ion dispersant, an organic solvent and a resin, and then stirred to obtain the nonmagnetic ferrite slurry; The non-magnetic ferrite tape is produced by casting: the non-magnetic ferrite slurry is used to make the non-magnetic ferrite tape.

[0018] In a possible implementation of the second aspect, the step of fabricating the magnetic ferrite strip includes the following sub-steps: Preparation of magnetic ferrite material: The raw materials for the magnetic ferrite material are weighed according to the following molar percentages: 10 mol%~38 mol% zinc oxide, 5 mol%~15 mol% copper oxide, 30 mol%~50 mol% ferric oxide, with the balance being nickel oxide; the raw materials for the magnetic ferrite material are mixed with grinding balls and water, and then ground to obtain a second powder with a particle size of 0.5 μm~1 μm; the second powder is dried and then pre-calcined at a temperature of 800℃~850℃ for 1 hour~2 hours; after pre-calcination, bismuth trioxide is added to the second powder, mixed with grinding balls and water, and ground to a particle size of 0.2 μm~0.6 μm, and then dried to obtain the magnetic ferrite material; the molar amount of bismuth trioxide is 0.15%~0.35% based on the total molar amount of zinc oxide, nickel oxide, copper oxide and ferric oxide being 100%; Preparation of magnetic ferrite slurry: The magnetic ferrite material is mixed with an ion dispersant, an organic solvent and a resin, and then stirred to obtain the magnetic ferrite slurry; Casting process for producing the magnetic ferrite green tape: The magnetic ferrite slurry is cast into the magnetic ferrite green tape using a casting method.

[0019] In a possible implementation of the second aspect, prior to the step of creating the main body, the manufacturing method further includes the following steps: Fabrication of magnetic core column: Stack the inner electrode strips of each layer to obtain the inner electrode strip block, make holes in the inner electrode strip block to obtain magnetic core column holes, and fill the magnetic core column holes with magnetic ferrite material to obtain the magnetic core column. And / or, The steps for creating the main body include: The main semi-finished product was sintered in an air atmosphere at a temperature of 900±20℃ for 2h±5min, and then cooled to room temperature.

[0020] Thirdly, embodiments of this application disclose an electronic device, including: The filter as described in the first aspect; or, The filter is prepared by the method described in the second aspect.

[0021] Compared with the prior art, the beneficial effects of this application are: This application controls the molar ratio of Ni and Zn elements in the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer, so that the filter has both good magnetic properties and filtering performance, and can reduce structural defects after the main body is sintered.

[0022] Specifically, in this application, the main body includes a first magnetic ferrite layer, a first non-magnetic ferrite layer and a second magnetic ferrite layer stacked sequentially. The internal electrode is disposed in the first non-magnetic ferrite layer. The non-magnetic ferrite material has a low dielectric constant and a small distributed capacitance, which is beneficial to improving the differential mode cutoff frequency of the filter and maintaining high impedance in a wider frequency band, thereby improving the filtering performance of the filter.

[0023] Based on this, the first magnetic ferrite layer and the second magnetic ferrite layer stacked on both sides of the first non-magnetic ferrite layer are beneficial to improving the permeability. Since impedance and permeability are positively correlated, this is beneficial to improving the impedance of the filter.

[0024] Furthermore, the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer are all ferrite layers, and the co-firing compatibility among multiple ferrite layers is relatively good.

[0025] Furthermore, the inventors discovered that the molar ratio of Ni to Zn elements in the materials of the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer has a significant impact on co-firing compatibility. When r1 < r2 and r1 < r3, that is, when the molar ratio of Ni to Zn elements in the first non-magnetic ferrite layer is smaller than that in the first and second magnetic ferrite layers, the difference in thermal expansion coefficients and sintering shrinkage rates between the first non-magnetic ferrite layer, the first magnetic ferrite layer, and the second magnetic ferrite layer is smaller, resulting in a more matched sintering shrinkage curve. This leads to good co-firing compatibility among the layers of the main body, which helps reduce structural defects after sintering, improves the mechanical strength of the main body, and thus enhances the structural integrity and reliability of the filter. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1This is a schematic diagram of the filter structure disclosed in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the filter (which also includes a magnetic core column) disclosed in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of the filter disclosed in the embodiments of this application (the main body also includes a second non-magnetic ferrite layer and a third non-magnetic ferrite layer); Figure 4 This is a schematic diagram of the structure of the filter disclosed in the embodiments of this application (the main body also includes a first transition layer and a second transition layer); Figure 5 for Figure 4 Exploded view; Figure 6 This is a schematic diagram of the filter structure for Comparative Example 1; Figure 7 This is a schematic diagram of the filter structure for Comparative Example 2; Figure 8 This is a schematic diagram of the filter structure in Comparative Example 3.

[0028] Explanation of reference numerals in the attached figures: 1. Filter; 10. Main body; 11a. First magnetic ferrite layer; 12a. First non-magnetic ferrite layer; 11b. Second magnetic ferrite layer; 12b. Second non-magnetic ferrite layer; 12c. Third non-magnetic ferrite layer; 12d. First transition layer; 12e. Second transition layer; 13a. First ceramic insulating layer; 13b. Second ceramic insulating layer; 13c. Third ceramic insulating layer; 20. Internal electrode; 21. Lead-out terminal; 22. Connection terminal; 30. Magnetic core post; Z. Thickness direction of the first non-magnetic ferrite layer. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In this application, the terms "upper," "lower," "inner," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0031] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0032] Furthermore, the term "setup" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection via an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0034] In addition, some terms are explained as follows: Multilayer chip common-mode filters: These are filters that employ a multilayer stacked structure, such as filters with magnetic ferrite layers, non-magnetic ferrite layers, and internal electrodes. Multilayer chip common-mode filters are electronic components used to suppress common-mode interference, achieving effective filtering of common-mode signals.

[0035] Co-firing compatibility: In the co-firing process of multilayer materials, the ability of different material layers (such as magnetic ferrite layers and non-magnetic ferrite layers) to coordinate and be consistent in characteristics such as thermal expansion coefficient and sintering shrinkage rate during the sintering process, so as to avoid structural defects such as cracking, deformation and delamination.

[0036] RDC: Direct Current Resistance, the unit of which is ohms (Ω).

[0037] Zc: Common-mode impedance, in ohms (Ω).

[0038] Scc21: Derived from the "scattering parameter (S parameter)", it specifically refers to the "transmission coefficient of common-mode signal": the first "c" = common-mode, the second "c" = common-mode input; "21" = signal transmission from port 1 (input) to port 2 (output); in essence, it is the S parameter expression of "common-mode gain (A_c)", the smaller the value, the weaker the common-mode interference transmission.

[0039] Currently, mobile devices such as smartphones and tablets that involve signal transmission generally use differential circuits for signal transmission, and their signals exist in differential mode. However, noise that affects signal transmission and integrity generally appears in common mode. Therefore, introducing a common-mode filter into the differential circuit is the key to effectively suppressing common-mode noise and preserving differential-mode signals.

[0040] As electronic devices rapidly evolve towards miniaturization, higher frequency, and greater integration, the requirements for electromagnetic compatibility (EMC) of their internal circuits are becoming increasingly stringent. Common-mode interference, a common type of electromagnetic interference in electronic devices, can lead to signal transmission distortion, degraded device performance, and even device malfunctions. Therefore, common-mode filters have become an indispensable key component in electronic circuits.

[0041] Common-mode filters are widely used in consumer electronics devices due to their advantages such as small size, low parasitic parameters, and stable filtering performance. A common-mode filter consists of a main body and internal electrodes disposed within the main body. The performance of the main body has a significant impact on the product's filtering performance, mechanical strength, and reliability.

[0042] When the main body can be made of a single material, the filtering performance of the filter is not ideal. Filters using non-magnetic ferrite main bodies suffer from low common-mode impedance due to the low permeability of non-magnetic ferrite, resulting in limited common-mode signal suppression. Filters using magnetic ferrite main bodies, on the other hand, suffer from a lower differential-mode cutoff frequency and increased attenuation of useful signals.

[0043] Based on the above problems, the inventors discovered that when the main body uses different material layers: a magnetic ferrite layer superimposed with a non-magnetic ceramic layer, the filter has advantages such as high differential mode cutoff frequency and strong common mode signal suppression capability.

[0044] However, due to the significant difference in thermal expansion coefficients and sintering shrinkage rates between the non-magnetic ceramic layer and the magnetic ferrite layer, the co-firing compatibility between the multilayer materials is poor during the co-firing process.

[0045] This poor co-firing matching can easily lead to a series of structural problems, such as microcracks, delamination, and internal electrode misalignment inside the product. These defects not only reduce the mechanical strength and reliability of the common-mode filter, but also cause instability in its magnetic properties and filtering performance, such as decreased permeability, increased insertion loss, and reduced common-mode rejection ratio.

[0046] Further research revealed that non-magnetic ferrites and magnetic ferrites exhibit better co-firing compatibility and superior product morphology. However, due to the influence of the material elemental composition, the co-firing system of non-magnetic ferrites and magnetic ferrites still suffers from co-firing defects.

[0047] Based on the above analysis, this application controls the molar ratio of Ni and Zn elements in the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer, so that the filter can improve the differential mode cutoff frequency while also having good co-firing matching, thereby improving the reliability of the filter.

[0048] The technical solution of the present invention will now be described in conjunction with the embodiments and accompanying drawings.

[0049] like Figure 1 As shown, this application discloses a filter 1. Exemplarily, the filter 1 can be a stacked chip common-mode filter.

[0050] The filter 1 includes a main body 10 and an inner electrode 20. The main body 10 includes a first magnetic ferrite layer 11a, a first non-magnetic ferrite layer 12a, and a second magnetic ferrite layer 11b stacked sequentially. The inner electrode 20 is disposed within the first non-magnetic ferrite layer 12a.

[0051] The materials of the first magnetic ferrite layer 11a, the second magnetic ferrite layer 11b, and the first non-magnetic ferrite layer 12a contain at least Ni and Zn elements. The molar ratio of Ni to Zn in the first non-magnetic ferrite layer 12a is r1, the molar ratio of Ni to Zn in the first magnetic ferrite layer 11a is r2, and the molar ratio of Ni to Zn in the second magnetic ferrite layer 11b is r3, satisfying the following relationship: r1 < r2 and r1 < r3. It should be noted that r2 and r3 can be either equal or unequal.

[0052] This application controls the molar ratio of Ni and Zn elements in the first magnetic ferrite layer 11a, the first non-magnetic ferrite layer 12a, and the second magnetic ferrite layer 11b, so that the filter 1 has both good magnetic properties and filtering performance, and can reduce structural defects after the main body is sintered.

[0053] Specifically, in this application, the main body 10 includes a first magnetic ferrite layer 11a, a first non-magnetic ferrite layer 12a, and a second magnetic ferrite layer 11b stacked sequentially. The inner electrode 20 is disposed within the first non-magnetic ferrite layer 12a. The non-magnetic ferrite material has a low dielectric constant and a small distributed capacitance, which helps to improve the differential mode cutoff frequency of the filter 1, maintain high impedance over a wider frequency band, and thus improve the filtering performance of the filter 1.

[0054] Based on this, the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b stacked on both sides of the first non-magnetic ferrite layer 12a are beneficial to improving the permeability, thereby improving the impedance of the filter 1.

[0055] Furthermore, the first magnetic ferrite layer 11a, the first non-magnetic ferrite layer 12a, and the second magnetic ferrite layer 11b are all ferrite layers, and the co-firing compatibility among the multiple ferrite layers is relatively good.

[0056] Furthermore, the inventors discovered that the molar ratio of Ni to Zn elements in the materials of the first magnetic ferrite layer 11a, the first non-magnetic ferrite layer 12a, and the second magnetic ferrite layer 11b has a significant impact on co-firing compatibility. When r1 < r2 and r1 < r3, that is, when the molar ratio of Ni to Zn elements in the first non-magnetic ferrite layer 12a is smaller than that in the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, the difference in thermal expansion coefficients and sintering shrinkage rates between the first non-magnetic ferrite layer 12a, the first magnetic ferrite layer 11a, and the second magnetic ferrite layer 11b is smaller, resulting in a more matched sintering shrinkage curve. This leads to good co-firing compatibility among the layers of the main body 10, which helps reduce structural defects after sintering, improves the mechanical strength of the main body 10, and thus enhances the structural integrity and reliability of the filter 1.

[0057] Furthermore, when the molar ratio of Ni to Zn in the first non-magnetic ferrite layer 12a is less than that in the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, the sintering temperature of the first non-magnetic ferrite layer 12a is lower. This helps to avoid melting problems during the sintering of the inner electrode 20 and the first non-magnetic ferrite layer 12a, achieving the goal of simultaneous densification of the inner electrode 20 and the first non-magnetic ferrite layer 12a. A lower n(Ni):n(Zn) ratio also results in higher insulation reliability of the first non-magnetic ferrite layer 12a, which is beneficial for the insulation protection of the inner electrode 20.

[0058] Furthermore, r1 and r2 also satisfy the following relationship: r2 / r1 = 84~286, for example, 84, 90, 100, 120, 140, 160, 180, 200, 240, 260, 280 or 286. When r2 / r1 satisfies the above ratio range, the sintering shrinkage curves of the first non-magnetic ferrite layer 12a and the first magnetic ferrite layer 11a are further matched, resulting in better co-firing matching between the layers of the main body 10. This is beneficial for further reducing structural defects after sintering of the main body 10 and further improving the mechanical strength of the main body 10, thereby improving the structural integrity and reliability of the filter 1.

[0059] Optionally, r1 and r3 also satisfy the following relationship: r3 / r1 = 84~286, for example, 84, 90, 100, 120, 140, 160, 180, 200, 240, 260, 280 or 286. When r2 / r1 satisfies the above ratio range, the sintering shrinkage curves of the first non-magnetic ferrite layer 12a and the second magnetic ferrite layer 11b are further matched, resulting in better co-firing matching between the layers of the main body 10. This is beneficial for further reducing structural defects after sintering of the main body 10 and further improving the mechanical strength of the main body 10, thereby improving the structural integrity and reliability of the filter 1.

[0060] Optionally, r1 can be 0.007 to 0.0237, for example, 0.007, 0.008, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.022, or 0.0237.

[0061] The inventors discovered that when the molar ratio r1 of Ni and Zn elements in the first non-magnetic ferrite layer 12a is greater than or equal to 0.007, the sintering shrinkage curve of the first non-magnetic ferrite layer 12a is more closely matched with that of the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b. This results in good co-firing matching between the layers of the main body 10, which helps to reduce structural defects after sintering of the main body 10, improves the mechanical strength of the main body 10, and thus enhances the reliability of the stacked common-mode filter 1.

[0062] Furthermore, r1≤0.0237, so that the relative permeability of the non-magnetic ferrite material is still within a suitable range, which is beneficial to improve the differential mode cutoff frequency of the product, maintain high impedance in a wider frequency band, and thus improve the filtering performance of the stacked common mode filter 1.

[0063] Optionally, r2>1 can be 1.1~3, 1.5~2.5, or 1.9~2.1, specifically 1.1, 1.5, 2, 2.5, or 3, or 1.1~3, 1.5~2.5, or 1.9~2.1. In this case, the permeability of the first magnetic ferrite layer 11a is sufficiently high, thereby giving the filter a sufficiently high impedance.

[0064] Optionally, r3>1, which can be 1.1~3, 1.5~2.5, or 1.9~2.1, specifically 1.1, 1.5, 2, 2.5, or 3, or 1.1~3, 1.5~2.5, or 1.9~2.1. In this case, the permeability of the second magnetic ferrite layer 11b is sufficiently high, thereby giving the filter a sufficiently high impedance.

[0065] In some embodiments, the material of the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b further includes Bi (bismuth) element, and the molar percentage of Bi element is 0.13 mol% to 0.31 mol%.

[0066] Using Bi as a sintering aid, this application controls the molar percentage of Bi to be ≥0.13 mol%, making the magnetic ferrite material easier to sinter and resulting in a denser structure for the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, thereby reducing the risk of metal element migration in the inner electrode 20. The inventors discovered that Bi volatilization causes a shift in the material composition of the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, leading to magnetic instability. When the molar percentage of Bi is ≤0.31 mol%, the shift in material composition caused by Bi volatilization can be effectively avoided, suppressing metal element migration in the inner electrode 20. This improves the stability of the magnetic properties of the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, thereby increasing the common-mode rejection ratio, reducing insertion loss, and optimizing filtering performance.

[0067] In some embodiments, such as Figure 2 As shown, the filter 1 also includes a magnetic core post 30. Along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer, the magnetic core post 30 penetrates the first non-magnetic ferrite layer 12a. The two ends of the magnetic core post 30 are connected to the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, respectively, to form a magnetic core. An inner electrode 20 is wound around the central axis of the magnetic core post 30. For example, the inner electrode 20 is a planar helical coil wound around the central axis of the magnetic core post 30.

[0068] In this embodiment, the magnetic core column 30 provides a magnetic coupling channel, enabling effective magnetic coupling between the planar helical coils and suppressing common-mode signals. The I-shaped structure composed of the magnetic core column 30, the first magnetic ferrite layer 11a, and the second magnetic ferrite layer 11b can optimize the magnetic field distribution, reduce leakage flux, and improve permeability and common-mode rejection ratio.

[0069] Optionally, such as Figure 2 As shown in (A), the longitudinal cross-sectional shape of the magnetic core post 30 is square. Figure 2 As shown in (B), the longitudinal cross-sectional shape of the magnetic core post 30 is trapezoidal. Both square and trapezoidal magnetic core posts 30 are beneficial for reducing magnetic leakage.

[0070] Optionally, the magnetic core 30, the first magnetic ferrite layer 11a, and the second magnetic ferrite layer 11b can be made of the same material. In this way, the magnetic core 30, the first magnetic ferrite layer 11a, and the second magnetic ferrite layer 11b can be manufactured using magnetic ferrite tape of the same material, thereby reducing the manufacturing difficulty of the main body 10 and improving production efficiency.

[0071] Of course, the materials of the magnetic core column 30, the first magnetic ferrite layer 11a, and the second magnetic ferrite layer 11b can also be different.

[0072] In some embodiments, such as Figure 3 As shown, the main body 10 also includes a second non-magnetic ferrite layer 12b and a third non-magnetic ferrite layer 12c. The second non-magnetic ferrite layer 12b is disposed on the side of the first magnetic ferrite layer 11a opposite to the first non-magnetic ferrite layer 12a. The third non-magnetic ferrite layer 12c is disposed on the side of the second magnetic ferrite layer 11b opposite to the first non-magnetic ferrite layer 12a.

[0073] The second non-magnetic ferrite layer 12b and the third non-magnetic ferrite layer 12c can act as protective layers, which can isolate moisture and impurities in the external environment, prevent the first magnetic ferrite layer 11a, the second magnetic ferrite layer 11b and the inner electrode 20 from corrosion, and at the same time provide good insulation performance to avoid interlayer leakage.

[0074] Optionally, the first non-magnetic ferrite layer 12a, the second non-magnetic ferrite layer 12b, and the third non-magnetic ferrite layer 12c are made of the same material.

[0075] In this way, the first non-magnetic ferrite layer 12a, the second non-magnetic ferrite layer 12b, and the third non-magnetic ferrite layer 12c can be made of non-magnetic ferrite raw tape of the same material, thereby reducing the manufacturing difficulty of the main body 10 and improving production efficiency.

[0076] Of course, the materials of the first non-magnetic ferrite layer 12a, the second non-magnetic ferrite layer 12b, and the third non-magnetic ferrite layer 12c can also be different.

[0077] It should be noted that, as Figure 3 As shown in (A), the main body 10 may not have a magnetic core post. Figure 3 As shown in (B), the main body 10 may also have a magnetic core post 30.

[0078] Furthermore, such as Figure 4 As shown, the main body 10 also includes a first transition layer 12d and a second transition layer 12e. The first transition layer 12d is disposed between the first magnetic ferrite layer 11a and the first non-magnetic ferrite layer 12a. The second transition layer 12e is disposed between the second magnetic ferrite layer 11b and the first non-magnetic ferrite layer 12a. Both the first transition layer 12d and the second transition layer 12e are made of non-magnetic ferrite.

[0079] The first transition layer 12d and the second transition layer 12e can serve as interface materials for the first non-magnetic ferrite layer 12a, avoiding direct contact between the inner electrode 20 and the first magnetic ferrite layer 11a or the second magnetic ferrite layer 11b, which helps to improve the reliability of the filter 1.

[0080] Optionally, the main body 10 has a symmetrical structure, with the axis of symmetry of the main body 10 being the centerline along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer. The symmetrical structure of the main body 10 helps to balance the stress of each layer of the main body 10, thereby improving the reliability of the product.

[0081] In some embodiments, such as Figure 5 As shown, the inner electrode 20 is a planar helical coil, and there are multiple planar helical coils arranged at intervals along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer. A planar helical coil refers to a coil wound on a plane. The filter 1 using planar helical coils is suitable for high-frequency scenarios and balances miniaturization and performance stability.

[0082] Furthermore, the multiple planar helical coils are divided into at least two groups, each group comprising multiple planar helical coils connected in series, and the planar helical coils within the same group are symmetrically distributed. The symmetrical distribution can be, for example, mirror symmetry or rotational symmetry.

[0083] Optionally, there can be two or three groups of planar helical coils. The number of planar helical coils in each group can be two or three, and this application embodiment does not limit this.

[0084] For example, such as Figure 5 As shown, there are four inner electrodes 20, which are spaced apart along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer. Each inner electrode 20 has a lead-out end 21 and a connection end 22, and each lead-out end 21 is exposed on the main body 10. Counting from top to bottom along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer, the four inner electrodes 20 are sequentially the first inner electrode 20, the second inner electrode 20, the third inner electrode 20, and the fourth inner electrode 20. The connection end 22 of the first inner electrode 20 is connected to the connection end 22 of the third inner electrode 20 to form one group of inner electrodes 20, and the connection end 22 of the second inner electrode 20 is connected to the connection end 22 of the fourth inner electrode 20 to form another group of inner electrodes 20.

[0085] It should be noted that the internal electrodes of this application are not limited to the connection method and order described above. Alternatively, the first internal electrode may be connected to the fourth internal electrode, and the second internal electrode may be connected to the third internal electrode. Or, the first internal electrode may be connected to the second internal electrode, and the third internal electrode may be connected to the fourth internal electrode.

[0086] Optionally, the inner electrode 20 may be made of silver. Silver has low electrical resistance and is easy to fabricate by printing silver paste.

[0087] Refer to the return Figure 4 Along the thickness direction Z0-Z1 of the first non-magnetic ferrite layer, the distance between the first magnetic ferrite layer 11a and the nearest inner electrode 20 is D1, where 28 μm ≤ D1 ≤ 50 μm. D1 can be, for example, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 45 μm, 49 μm, or 50 μm.

[0088] Optionally, the distance between the second magnetic ferrite layer 11b and the nearest inner electrode 20 is D2, where 28 μm ≤ D2 ≤ 50 μm. D2 is, for example, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 45 μm, 49 μm, or 50 μm.

[0089] It should be noted that D1 can be the same as D2, or D1 can be different from D2.

[0090] This application controls the spacing between the first magnetic ferrite layer 11a, the second magnetic ferrite layer 11b and the nearest inner electrode 20, so that the inner electrode 20 is sufficiently far away from the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, thereby reducing the risk of mutual migration between the inner electrode 20 and the magnetic ferrite material, and thus reducing the short circuit risk of the device and improving the reliability of the filter 1.

[0091] Furthermore, the inner electrode 20 is not too far from the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b, so as to prevent the first non-magnetic ferrite layer 12a from being too thick and occupying too much height. This helps the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b to maintain a suitable thickness, thereby increasing the inductance and common-mode impedance of the filter 1 and thus improving the filtering capability of the filter 1.

[0092] It should be noted that the distance D between the first magnetic ferrite layer 11a and the nearest inner electrode 20, and the distance D between the second magnetic ferrite layer 11b and the nearest inner electrode 20, can be the same or different.

[0093] This application discloses a method for manufacturing a filter, including the following steps: Fabrication of magnetic ferrite tapes; Fabrication of nonmagnetic ferrite raw tapes; Fabrication of internal electrodes: Internal electrodes are fabricated on a portion of non-magnetic ferrite strips to obtain internal electrode strips. Fabrication of the main body: Non-magnetic ferrite green tape, magnetic ferrite green tape, and inner electrode green tape are stacked in a predetermined order to obtain the main body semi-finished product; the main body semi-finished product is sintered to obtain the main body; wherein, the main body includes a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer stacked in sequence, the inner electrode is set in the first non-magnetic ferrite layer, and the materials of the first magnetic ferrite layer, the second magnetic ferrite layer, and the first non-magnetic ferrite layer contain at least Ni and Zn elements; the molar ratio of Ni to Zn elements in the first non-magnetic ferrite layer, n(Ni):n(Zn) is r1, the molar ratio of Ni to Zn elements in the first magnetic ferrite layer, n(Ni):n(Zn) is r2, and the molar ratio of Ni to Zn elements in the second magnetic ferrite layer, n(Ni):n(Zn) is r3, satisfying the following relationship: r1 < r2, and r1 < r3.

[0094] In the manufacturing method of this application, the main body is obtained by co-firing a non-magnetic ferrite green tape, a magnetic ferrite green tape, and an inner electrode green tape. The non-magnetic ferrite green tape, the magnetic ferrite green tape, and the inner electrode green tape are all made of ferrite materials and have good co-firing compatibility.

[0095] Furthermore, the inventors discovered that the molar ratio of Ni to Zn in the materials of the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer has a significant impact on co-firing compatibility. Moreover, when the molar ratio of Ni to Zn in the first non-magnetic ferrite layer is less than that in the first and second magnetic ferrite layers, the differences in thermal expansion coefficients and sintering shrinkage rates between the first non-magnetic ferrite layer, the first magnetic ferrite layer, and the second magnetic ferrite layer are smaller, resulting in a more matched sintering shrinkage curve. This leads to better co-firing compatibility among the layers of the main body, which helps reduce structural defects after sintering, improves the mechanical strength of the main body, and ultimately enhances the structural integrity and reliability of the filter.

[0096] In some embodiments, the step of fabricating a nonmagnetic ferrite strip includes the following sub-steps: Preparation of nonmagnetic ferrite material: The raw materials for nonmagnetic ferrite material are weighed according to the following molar percentages: 35.04 mol%~44.97 mol% zinc oxide (ZnO), 0.32 mol%~0.83 mol% nickel oxide (NiO), 7.66 mol%~9.42 mol% copper oxide (CuO), and 47.05 mol%~54.71 mol% ferric oxide (Fe2O3); the raw materials for nonmagnetic ferrite material are mixed with grinding balls and water, and then ground to obtain a first powder with a particle size of 0.5 μm~1 μm; the first powder is dried and then pre-fired at a temperature of 800℃~850℃ for 1 hour~2 hours; the pre-fired first powder is mixed with grinding balls and water and ground to a particle size of 0.2 μm~0.6 μm, and then dried to obtain the nonmagnetic ferrite material; Preparation of nonmagnetic ferrite slurry: After mixing nonmagnetic ferrite material with ion dispersant, organic solvent and resin, the mixture is stirred to obtain the nonmagnetic ferrite slurry; The tape casting process uses non-magnetic ferrite raw tape: the tape casting method uses non-magnetic ferrite slurry to make non-magnetic ferrite raw tape.

[0097] In this embodiment, the fabrication method controls the molar percentages of zinc oxide and nickel oxide in the non-magnetic ferrite material to maintain the molar ratio r1 of Ni and Zn elements within the range of 0.007 to 0.0237. This results in a better match between the sintering shrinkage curve of the first non-magnetic ferrite layer and the first and second magnetic ferrite layers, leading to good co-firing compatibility among the main body layers. Furthermore, the relative permeability of the non-magnetic ferrite material remains within a suitable range, which is beneficial for increasing the differential-mode cutoff frequency of the product, maintaining high impedance over a wider frequency band, and thus improving the filtering performance of the multilayer common-mode filter.

[0098] In some embodiments, the step of fabricating a magnetic ferrite strip includes the following sub-steps: Preparation of magnetic ferrite material: The raw materials for magnetic ferrite material are weighed according to the following molar percentages: 10 mol%~38 mol% zinc oxide, 5 mol%~15 mol% copper oxide, 30 mol%~50 mol% ferric oxide, with the balance being nickel oxide. The raw materials are mixed with grinding balls and water, and then ground to obtain a second powder with a particle size of 0.5 μm~1 μm. The second powder is dried and then pre-calcined at 800℃~850℃ for 1 hour~2 hours. After pre-calcination, bismuth trioxide is added to the second powder, mixed with grinding balls and water, and ground to a particle size of 0.2 μm~0.6 μm. The powder is then dried to obtain the magnetic ferrite material. Based on the total molar amount of zinc oxide, nickel oxide, copper oxide, and ferric oxide being 100%, the molar amount of bismuth trioxide is 0.15%~0.35%. Preparation of magnetic ferrite slurry: The magnetic ferrite material is mixed with an ion dispersant, an organic solvent and a resin and stirred to obtain the magnetic ferrite slurry; Casting process for producing magnetic ferrite green tape: The magnetic ferrite slurry is cast into a magnetic ferrite green tape using the casting method.

[0099] In this embodiment, the fabrication method controls the molar percentages of zinc oxide and nickel oxide in the magnetic ferrite material to achieve a relatively higher molar ratio of Ni to Zn. This results in a better match between the sintering shrinkage curves of the magnetic ferrite green tape and the non-magnetic ferrite green tape, leading to good co-firing compatibility between the layers of the main body. This helps reduce structural defects after sintering, improves the mechanical strength of the main body, and ultimately enhances the structural integrity and reliability of the filter.

[0100] In some embodiments, prior to the step of creating the main body, the manufacturing method further includes the following steps: Fabrication of magnetic core pillars: Stacking inner electrode strips of each layer to obtain inner electrode strip blocks, making holes in the inner electrode strip blocks to obtain magnetic core pillar holes, and filling the magnetic core pillar holes with magnetic ferrite material to obtain magnetic core pillars.

[0101] This application involves filling the holes of a magnetic core pillar with magnetic ferrite material, which is then sintered to transform the magnetic ferrite material into a magnetic core pillar. The I-shaped structure composed of the magnetic core pillar, the first magnetic ferrite layer, and the second magnetic ferrite layer optimizes the magnetic field distribution, reduces magnetic leakage, and improves permeability and common-mode rejection ratio.

[0102] In some embodiments, the step of creating the main body includes: The main semi-finished product was sintered in an air atmosphere at a temperature of 900±20℃ for 2h±5min. After sintering, it was cooled to room temperature.

[0103] The manufacturing method of this application achieves high-quality co-firing molding of the filter by controlling the sintering temperature and holding time.

[0104] This application discloses an electronic device, including: The filter in any of the above embodiments; or, The filter is manufactured by the method described in any of the above embodiments.

[0105] For example, the electronic device is a mobile phone, tablet, or computer.

[0106] The technical solution of this application will be further described below with reference to embodiments and comparative examples.

[0107] Examples 1-1 to 1-17 A method for manufacturing a filter includes the following steps: S1. Fabrication of non-magnetic ferrite ribbon, including the following sub-steps: S11. Preparation of non-magnetic ferrite material: Weigh the raw materials for non-magnetic ferrite material, including: zinc oxide (ZnO), nickel oxide (NiO), copper oxide (CuO), and ferric oxide (Fe2O3). Mix the raw materials of non-magnetic ferrite material with grinding balls and water, and grind to obtain a first powder with a particle size of 0.5 μm to 1 μm; dry the first powder and pre-calcine it at a temperature of 850℃ for 2 hours; mix the pre-calcineed first powder with grinding balls and water and grind it to a particle size of 0.3 μm, then dry it to obtain the non-magnetic ferrite material. S12. Preparation of non-magnetic ferrite slurry: Non-magnetic ferrite material is mixed with an ionic dispersant, an organic solvent, and a resin, and then stirred in a planetary ball mill for 8 hours to obtain a non-magnetic ferrite slurry. The ratio of m (non-magnetic ferrite material):m (non-ionic dispersant):m (organic solvent):m (resin) is 70:3:20:7. The ionic dispersant is VXW 6208. S13. Casting process using non-magnetic ferrite raw tape: The casting method is used to make non-magnetic ferrite slurry into non-magnetic ferrite raw tape.

[0108] S2. Fabrication of magnetic ferrite live tape, including the following sub-steps: S21. Preparation of magnetic ferrite material: Weigh the raw materials for magnetic ferrite material, including zinc oxide, nickel oxide, copper oxide, and ferric oxide; mix the raw materials with grinding balls and water, and grind to obtain a second powder with a particle size of 0.5 μm to 1 μm; dry the second powder and pre-calcine it at a temperature of 850℃ for 2 hours; add bismuth trioxide to the pre-calcineed second powder, mix with grinding balls and water, and grind to a particle size of 0.3 μm; dry the powder after grinding to obtain the magnetic ferrite material. S22. Preparation of magnetic ferrite slurry: The magnetic ferrite material is mixed with an ionic dispersant, an organic solvent, and a resin, and then stirred in a planetary ball mill for 8 hours to obtain the magnetic ferrite slurry. Wherein, m (magnetic ferrite material):m (nonionic dispersant):m (organic solvent):m (resin) = 60:3:30:7; S23. Casting for making magnetic ferrite raw tape: The magnetic ferrite slurry is cast into a magnetic ferrite raw tape using the casting method.

[0109] S3. Fabrication of internal electrodes: Internal electrodes are fabricated on a portion of the non-magnetic ferrite strips to obtain internal electrode strips.

[0110] S4. Fabrication of magnetic core pillars: Stack the inner electrode strips of each layer to obtain an inner electrode strip block, make holes in the inner electrode strip block to obtain magnetic core pillar holes, and fill the magnetic core pillar holes with magnetic ferrite material to obtain a magnetic core pillar.

[0111] S5. Making the main body: The non-magnetic ferrite strip, magnetic ferrite strip, and internal electrode strip block are stacked in a preset order, and then cut after hot pressing to obtain the main body semi-finished product.

[0112] The main semi-finished product was sintered in air at a temperature of 900±20℃ for 2h±5min. After sintering, it was cooled to room temperature to obtain the filter. The filter dimensions are: length 0.85 mm × width 0.65 mm × height 0.4 mm.

[0113] The main body comprises a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer, which are stacked sequentially. The thickness of the first non-magnetic ferrite layer is 178 micrometers, and the thickness of both the first and second magnetic ferrite layers is 30 micrometers.

[0114] The main body also includes a second non-magnetic ferrite layer and a third non-magnetic ferrite layer. The second non-magnetic ferrite layer is disposed on the side of the first magnetic ferrite layer opposite to the first non-magnetic ferrite layer. The third non-magnetic ferrite layer is disposed on the side of the second magnetic ferrite layer opposite to the first non-magnetic ferrite layer. The thickness of both the second and third non-magnetic ferrite layers is 81 micrometers.

[0115] Example 2 The only difference between this embodiment and Embodiment 1-1 is that: Step S4 is not performed, that is, the magnetic core column is not made.

[0116] In step S5, the non-magnetic ferrite strip, the magnetic ferrite strip, and the internal electrode strip are stacked in a preset order to obtain the main semi-finished product.

[0117] Comparative Example 1 The only difference between this comparative example and Example 1-1 is that steps S2 and S4 are not performed.

[0118] In step S5, the non-magnetic ferrite strip and the inner electrode strip block are stacked in a preset order to obtain the main semi-finished product. (Refer to...) Figure 6 The main body 10 is a non-magnetic ferrite body, and the inner electrode 20 is disposed in the non-magnetic ferrite body.

[0119] Comparative Example 2 The only difference between this comparative example and Example 1-1 is that steps S1 and S4 are not performed.

[0120] In step S3, an inner electrode is fabricated on a portion of the magnetic ferrite strip to obtain an inner electrode strip.

[0121] In step S5, the magnetic ferrite strip and the inner electrode strip block are stacked in a preset order to obtain the main semi-finished product. (Refer to...) Figure 7 The main body 10 is a magnetic ferrite body, and the internal electrode is set in the magnetic ferrite body.

[0122] Comparative Example 3 The method for fabricating this comparative filter includes the following steps: S1. Preparation of ceramic materials: Weigh the following raw materials according to the following molar percentages: SiO2∶B2O3∶ZrO2∶Al2O3 = 89.63 %∶2.22 %∶5.84 %∶2.31 %; Mix SiO2, B2O3, and Al2O3 evenly using a three-dimensional mixer and then melt them at a melting temperature of 1350℃ for 4 hours. After water quenching, a high borosilicate glass body is obtained; the high borosilicate glass body is ball-milled for 8 hours to obtain high borosilicate glass powder with a D50 of 1.8 μm; mix the high borosilicate glass powder and ZrO2 powder with a D50 of 1.0 μm evenly to obtain the ceramic material.

[0123] S2. Preparation of ceramic slurry.

[0124] Weigh the following materials according to the following mass percentages: Ceramic material: silane coupling agent KH550 (dispersant): organic solvent: PVB resin (binder) = 100:3:105:23; The prepared ceramic material is mixed with silane coupling agent KH550 and organic solvent, stirred in a planetary ball mill for 4 hours, then PVB resin is added, and the mixture is stirred in a planetary ball mill for another 11 hours to obtain ceramic slurry.

[0125] S3. Preparation of ceramic raw tape: Take the above ceramic slurry and prepare ceramic raw tape by casting method.

[0126] S4. Fabrication of internal electrodes: Internal electrodes are fabricated on ceramic green tape using photolithography to obtain internal electrode ceramic green tape.

[0127] S5. Making the main body: The inner electrode ceramic green tape and the magnetic ferrite green tape obtained in step S2 of Example 1-1 are stacked in a preset order, hot-pressed and then cut to obtain the main body semi-finished product.

[0128] The main semi-finished product is sintered in air at a temperature of 900℃ for 2 hours, and then cooled to room temperature in the furnace to obtain the filter.

[0129] The filter dimensions are: 0.85 mm (length) × 0.65 mm (width) × 0.4 mm (height). (Refer to...) Figure 8 The main body 10 includes a first ceramic insulating layer 13a, a first magnetic ferrite layer 11a, a second ceramic insulating layer 13b, a second magnetic ferrite layer 11b, and a third ceramic insulating layer 13c, which are stacked sequentially. An internal electrode 20 is disposed in the second ceramic insulating layer 13b. The thickness of the first ceramic insulating layer 13a and the third ceramic insulating layer 13c is 41 micrometers, the thickness of the first magnetic ferrite layer 11a and the second magnetic ferrite layer 11b is 70 micrometers, and the thickness of the second ceramic insulating layer 13b is 178 micrometers.

[0130] Performance testing: The filters of each embodiment and each comparative example were subjected to performance tests. The specific test methods are described below.

[0131] Sintering cracking and delamination ratio test: Under a 30X microscope, count the number of products with appearance defects (delamination / cracking), sampling size: 800 pieces.

[0132] Electrical performance testing: The common-mode impedance Zc / Ω (@100MHz) and S-parameters of the filter were tested using an E5071C network analyzer.

[0133] Reliability testing: Humidity 85% RH, temperature 85 ± 2°C, voltage 5V, load time 1000 h, sampling size 2000 Pcs (pieces). The IR (Impulse Response) of the filter before and after the experiment was tested using a high-resistance meter. If the rate of change is >60%, it indicates product failure under load; if the failure rate is >0.2%, the reliability is deemed unacceptable.

[0134] Permeability test: Take 1 kg of non-magnetic ferrite powder, add 10% PVA solution and grind evenly. After granulation, dry at 120℃ for 5 min to 10 min, sieve through 120 mesh, add 0.2% zinc stearate and mix evenly. After pressing into a disc, heat the disc to 1080℃ in air at a heating rate of 3℃ / min and hold for 2 hours. After cooling, use an Agilent 4284A or equivalent LCR device to test the L value of the disc (test frequency 10 kHz, test voltage 5 mV). After the test, calculate the initial permeability μi based on the inductance L value at 1MHz.

[0135] Interface delamination test: Use a metallographic microscope at 100-1000x magnification to observe whether there is interface delamination between the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer. If interface delamination is present, the test result is recorded as "yes"; if there is no interface delamination, the test result is recorded as "no".

[0136] The following analysis, in conjunction with Tables 1 and 2, examines Examples 1-1, Example 2, and Comparative Examples 1 to 3.

[0137] Table 1 shows the differences between Examples 1-1, Example 2, and Comparative Examples 1 to 3. Table 2 shows the test results of Examples 1-1, Example 2, and Comparative Examples 1 to 3.

[0138] Table 1: Differences between Examples 1-1, Example 2, and Comparative Examples 1 to 3

[0139] Table 2: Test results of Examples 1-1, 2 and Comparative Examples 1 to 3

[0140] It should be noted that in Table 2, OK means qualified and NG means unqualified.

[0141] The impact of the main material on filter performance: As shown in Tables 1 and 2, the main body of Comparative Example 1 is made of non-magnetic ferrite material. Due to the low permeability of non-magnetic ferrite, there is a problem of low common-mode impedance, with a common-mode impedance Zc@100MHz of only 35.67.

[0142] The main body of Comparative Example 2 is made of non-magnetic ferrite material, which results in a smaller differential mode cutoff frequency and greater attenuation of useful signals, failing to meet product performance requirements.

[0143] Comparative Example 3 adopted a co-fired structure of ceramic and magnetic ferrite materials. The thermal expansion coefficients of ceramic and magnetic ferrite materials differ greatly, and the co-firing compatibility of the two materials is poor, resulting in a large proportion of sintering cracks and delamination, thus failing the reliability test.

[0144] Compared to Comparative Examples 1 to 3, Examples 1-1 and 2 employ a co-fired structure of non-magnetic ferrite and magnetic ferrite. The internal electrode is disposed within the first non-magnetic ferrite layer, which helps to increase the differential-mode cutoff frequency of the filter, maintain high impedance over a wider frequency band, and thus improve the filter's filtering performance. Furthermore, the first and second magnetic ferrite layers stacked on either side of the first non-magnetic ferrite layer help to increase permeability, thereby improving the common-mode impedance of the filter. Moreover, since the first magnetic ferrite layer, the first non-magnetic ferrite layer, and the second magnetic ferrite layer are all ferrite layers, the co-firing matching among multiple ferrite layers is relatively good, which helps to reduce the proportion of sintering cracking and delamination, and improves product reliability.

[0145] The test results of Examples 1-1 to 1-17 are analyzed below with reference to Tables 3 and 4.

[0146] Table 3 shows the differences between Examples 1-1 to 1-17, and Table 4 shows the test results of Examples 1-1 to 1-17.

[0147] Table 3: Differences between Examples 1-1 to 1-17

[0148] More specifically, in Table 3, when the ferrite material is non-magnetic, it refers to a non-magnetic ferrite material. When the ferrite material is magnetic, it refers to a magnetic ferrite material. n(Ni):n(Zn) refers to the molar ratio of nickel and zinc. D refers to the distance between the first magnetic ferrite layer and the nearest inner electrode, and the distance between the second magnetic ferrite layer and the nearest inner electrode, along the thickness direction of the first non-magnetic ferrite layer. It should be noted that in Examples 1-1 to 1-17, the distance between the first magnetic ferrite layer and the nearest inner electrode, and the distance between the second magnetic ferrite layer and the nearest inner electrode, are equal along the thickness direction of the first non-magnetic ferrite layer. The amount of Bi2O3 refers to the percentage of the added Bi2O3 calculated based on the total molar amount of zinc oxide (ZnO), nickel oxide (NiO), copper oxide (CuO), and ferric oxide (Fe2O3) in the magnetic ferrite material being 100%.

[0149] Table 4: Test Results of Examples 1-1 to 1-17

[0150] It should be noted that in Table 4, OK means qualified and NG means unqualified. The technical solution of this application will be further explained below with reference to Tables 3 and 4.

[0151] The effect of the molar ratio of Ni to Zn on improving co-firing compatibility: In Examples 1-1 to 1-17, the molar ratio of Ni to Zn in the first non-magnetic ferrite layer is smaller than that in the first and second magnetic ferrite layers. The difference in thermal expansion coefficient and sintering shrinkage rate between the first non-magnetic ferrite layer, the first magnetic ferrite layer, and the second magnetic ferrite layer is small, and the sintering shrinkage curves are more matched. This results in good co-firing matching between the first non-magnetic ferrite layer, the first magnetic ferrite layer, and the second magnetic ferrite layer, and the resulting filter product has no interface delamination phenomenon.

[0152] The effect of the molar ratio of Ni to Zn in nonmagnetic ferrite materials, n(Ni):n(Zn), on filter performance: As shown in Tables 3 and 4, in Examples 1-1 to 1-5, as the ratio of n(Ni):n(Zn) of the nonmagnetic ferrite material increases, the relative permeability increases and the magnetic reluctance decreases, resulting in a decrease in the differential mode cutoff frequency of the common-mode filter and a greater attenuation of the useful signal.

[0153] In Examples 1-10, because the n(Ni):n(Zn) ratio of the non-magnetic ferrite material increases to 0.0363, the relative permeability of the non-magnetic ferrite material increases to 13.76, and the differential mode cutoff frequency of the product decreases to 2.15 GHz, the differential mode signal attenuation shifts to lower frequencies, weakening the filtering performance of the filter.

[0154] In Examples 1-11, because the n(Ni):n(Zn) ratio of the non-magnetic ferrite material decreases to 0.0035, the nickel content in the non-magnetic ferrite material is low, the matching of the sintering shrinkage curves of the non-magnetic ferrite material and the magnetic ferrite material decreases, which in turn leads to a decrease in the reliability of the filter product.

[0155] The effect of Bi content in magnetic ferrite materials on filter performance: In Examples 1-1 to 10, 0.15% to 0.35% bismuth oxide was added to make the magnetic ferrite material easier to sinter, and to make the structure of the first magnetic ferrite layer and the second magnetic ferrite layer more compact. This reduces the risk of migration of metal elements contained in the inner electrode, inhibits the migration of metal elements in the inner electrode, and helps to improve the stability of the magnetic properties of the first magnetic ferrite layer and the second magnetic ferrite layer, thereby enabling the product to pass the reliability test.

[0156] In Examples 1-12, due to the low amount of bismuth oxide in the magnetic ferrite material, the magnetic ferrite material could not be sintered, resulting in a non-dense structure and increasing the risk of silver migration in the internal electrode, which in turn caused the product to fail the reliability test.

[0157] In Examples 1-13, due to the excessive amount of bismuth oxide in the magnetic ferrite material, the magnetic ferrite material was overburned, resulting in severe porosity defects. After the product was subjected to damp heat load, the interlayer silver migration was severe, and it could not pass the reliability test.

[0158] The effect of the spacing between the first magnetic ferrite layer, the second magnetic ferrite layer, and the nearest internal electrode on filter performance: In Examples 1-1 to 1-10, the distance between the inner electrode and the first magnetic ferrite layer and the second magnetic ferrite layer satisfies 28 μm ≤ D ≤ 50 μm, so that the inner electrode is sufficiently far away from the first magnetic ferrite layer and the second magnetic ferrite layer, reducing the risk of mutual migration between the inner electrode and the magnetic ferrite material, and thus passing the reliability test.

[0159] In Examples 1-14, the distance between the inner electrode and the first and second magnetic ferrite layers is too small, which increases the risk of silver migration in the inner electrode, increases the risk of short circuit in the device, and consequently causes the product to fail the reliability test, thus reducing the product reliability.

[0160] In Examples 1-15, the distance between the internal electrode and the first and second magnetic ferrite layers is too large, resulting in an excessively thick first non-magnetic ferrite layer. To meet certain product size requirements, the thickness of the first and second magnetic ferrite layers needs to be reduced. As a result, the effective magnetic circuit area is reduced, and the impedance of the device (Zc@100MHz) drops to 51.74Ω, thereby reducing the device's filtering capability.

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A filter, characterized in that, include: The main body comprises a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer stacked sequentially; and An inner electrode is disposed within the first non-magnetic ferrite layer; The materials of the first magnetic ferrite layer, the second magnetic ferrite layer, and the first non-magnetic ferrite layer contain at least Ni and Zn elements; the molar ratio of Ni to Zn in the first non-magnetic ferrite layer is r1, the molar ratio of Ni to Zn in the first magnetic ferrite layer is r2, and the molar ratio of Ni to Zn in the second magnetic ferrite layer is r3, satisfying the following relationship: r1 < r2, and r1 < r3.

2. The filter according to claim 1, characterized in that, The r1 and the r2 also satisfy the following relationship: r2 / r1 = 84~286; and / or, The r1 and r3 also satisfy the following relationship: r3 / r1 = 84~286.

3. The filter according to claim 1, characterized in that, The value of r1 is 0.007~0.0237.

4. The filter according to claim 1, characterized in that, The r2>1; and / or, The r3>1.

5. The filter according to claim 1, characterized in that, The material of the first magnetic ferrite layer and the second magnetic ferrite layer further includes Bi element, and the molar percentage of Bi element is 0.13 mol% to 0.31 mol%.

6. The filter according to any one of claims 1 to 4, characterized in that, The filter further includes a magnetic core column that penetrates the first non-magnetic ferrite layer along its thickness direction. The two ends of the magnetic core column are respectively connected to the first magnetic ferrite layer and the second magnetic ferrite layer to form a magnetic core. The inner electrode is wound around the central axis of the magnetic core column.

7. The filter according to claim 6, characterized in that, The longitudinal cross-sectional shape of the magnetic core column is trapezoidal or square; and / or, The magnetic core, the first magnetic ferrite layer, and the second magnetic ferrite layer are made of the same material.

8. The filter according to any one of claims 1 to 4, characterized in that, The inner electrode is a planar spiral coil, and there are multiple planar spiral coils, which are spaced apart along the thickness direction of the first non-magnetic ferrite layer. The plurality of planar spiral coils are divided into at least two groups, each group of planar spiral coils includes a plurality of planar spiral coils connected in series, and the planar spiral coils in the same group are symmetrically distributed.

9. The filter according to any one of claims 1 to 4, characterized in that, Along the thickness direction of the first non-magnetic ferrite layer, the distance D1 between the first magnetic ferrite layer and the nearest inner electrode is 28 μm ≤ D1 ≤ 50 μm; and / or, Along the thickness direction of the first non-magnetic ferrite layer, the distance between the second magnetic ferrite layer and the nearest inner electrode is D2, where 28 μm ≤ D2 ≤ 50 μm.

10. The filter according to any one of claims 1 to 4, characterized in that, The subject also includes: A second non-magnetic ferrite layer is disposed on the side of the first magnetic ferrite layer opposite to the first non-magnetic ferrite layer; and The third non-magnetic ferrite layer is disposed on the side of the second magnetic ferrite layer opposite to the first non-magnetic ferrite layer.

11. The filter according to claim 10, characterized in that, The first non-magnetic ferrite layer, the second non-magnetic ferrite layer, and the third non-magnetic ferrite layer are made of the same material.

12. The filter according to claim 10, characterized in that, The subject also includes: A first transition layer is disposed between the first magnetic ferrite layer and the first non-magnetic ferrite layer; and A second transition layer is disposed between the second magnetic ferrite layer and the first non-magnetic ferrite layer. The first transition layer and the second transition layer are both made of non-magnetic ferrite.

13. The filter according to any one of claims 1 to 4, characterized in that, The main body has a symmetrical structure, and the axis of symmetry of the main body is the center line of the main body along the thickness direction of the first non-magnetic ferrite layer.

14. A method for manufacturing a filter, characterized in that, Includes the following steps: Fabrication of magnetic ferrite tapes; Fabrication of nonmagnetic ferrite raw tapes; Fabrication of internal electrodes: The internal electrodes are fabricated on a portion of the non-magnetic ferrite green tapes to obtain internal electrode green tapes; Fabrication of the main body: The non-magnetic ferrite green tape, the magnetic ferrite green tape, and the inner electrode green tape are stacked in a preset order to obtain a main body semi-finished product; the main body semi-finished product is sintered to obtain the main body; wherein, the main body includes a first magnetic ferrite layer, a first non-magnetic ferrite layer, and a second magnetic ferrite layer stacked in sequence, the inner electrode is disposed in the first non-magnetic ferrite layer, and the materials of the first magnetic ferrite layer, the second magnetic ferrite layer, and the first non-magnetic ferrite layer contain at least Ni and Zn elements; the molar ratio of Ni to Zn in the first non-magnetic ferrite layer, n(Ni):n(Zn), is r1; the molar ratio of Ni to Zn in the first magnetic ferrite layer, n(Ni):n(Zn), is r2; the molar ratio of Ni to Zn in the second magnetic ferrite layer, n(Ni):n(Zn), is r3, satisfying the following relationship: r1 < r2, and r1 < r3.

15. The manufacturing method according to claim 14, characterized in that, The steps for fabricating nonmagnetic ferrite strips include the following sub-steps: Preparation of the nonmagnetic ferrite material: The raw materials for the nonmagnetic ferrite material are weighed according to the following molar percentages: 35.04 mol%~44.97 mol% zinc oxide, 0.32 mol%~0.83 mol% nickel oxide, 7.66 mol%~9.42 mol% copper oxide, and 47.05 mol%~54.71 mol% ferric oxide; the raw materials for the nonmagnetic ferrite material are mixed with grinding balls and water, and then ground to obtain a first powder with a particle size of 0.5 μm~1 μm; the first powder is dried and then pre-fired at a temperature of 800℃~850℃ for 1 hour~2 hours; the pre-fired first powder is mixed with grinding balls and water and ground to a particle size of 0.2 μm~0.6 μm, and then dried to obtain the nonmagnetic ferrite material; Preparation of nonmagnetic ferrite slurry: The nonmagnetic ferrite material is mixed with an ion dispersant, an organic solvent and a resin, and then stirred to obtain the nonmagnetic ferrite slurry; The non-magnetic ferrite tape is produced by casting: the non-magnetic ferrite slurry is used to make the non-magnetic ferrite tape.

16. The manufacturing method according to claim 14, characterized in that, The steps for fabricating the magnetic ferrite strip include the following sub-steps: Preparation of magnetic ferrite material: The raw materials for the magnetic ferrite material are weighed according to the following molar percentages: 10 mol%~38 mol% zinc oxide, 5 mol%~15 mol% copper oxide, 30 mol%~50 mol% ferric oxide, with the balance being nickel oxide; the raw materials for the magnetic ferrite material are mixed with grinding balls and water, and then ground to obtain a second powder with a particle size of 0.5 μm~1 μm; the second powder is dried and then pre-calcined at a temperature of 800℃~850℃ for 1 hour~2 hours; after pre-calcination, bismuth trioxide is added to the second powder, mixed with grinding balls and water, and ground to a particle size of 0.2 μm~0.6 μm, and then dried to obtain the magnetic ferrite material; the molar amount of bismuth trioxide is 0.15%~0.35% based on the total molar amount of zinc oxide, nickel oxide, copper oxide and ferric oxide being 100%; Preparation of magnetic ferrite slurry: The magnetic ferrite material is mixed with an ion dispersant, an organic solvent and a resin, and then stirred to obtain the magnetic ferrite slurry; Casting process for producing the magnetic ferrite green tape: The magnetic ferrite slurry is cast into the magnetic ferrite green tape using a casting method.

17. The manufacturing method according to any one of claims 14 to 16, characterized in that, Before the step of making the main body, the manufacturing method further includes the following steps: Fabrication of magnetic core column: Stack the inner electrode strips of each layer to obtain the inner electrode strip block, make holes in the inner electrode strip block to obtain magnetic core column holes, and fill the magnetic core column holes with magnetic ferrite material to obtain the magnetic core column. And / or, The steps for creating the main body include: The main semi-finished product was sintered in an air atmosphere at a temperature of 900±20℃ for 2h±5min, and then cooled to room temperature.

18. An electronic device, characterized in that, include: The filter as described in any one of claims 1 to 13; or, The filter is manufactured by the method described in any one of claims 14 to 17.

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