A magnetic filling paste, its preparation method and application

Abstract

The present invention provides a magnetic filling slurry and its preparation method and application. The raw materials of the magnetic filling slurry include, by weight, 95-99 parts of soft magnetic alloy powder, 1-5 parts of ferrite powder, 10-20 parts of binding liquid, 3-6 parts of a first composite solvent, 0.3-0.6 parts of a dispersant, and 0.3-0.6 parts of a first plasticizer; the binding liquid includes a binding agent, a second composite solvent, and a second plasticizer in a mass ratio of (3-4):(4-5):(3-1). The magnetic filling slurry provided by the present invention, by introducing ferrite powder as an insulating coating agent, makes the soft magnetic alloy powder have a higher magnetic permeability; by regulating the ratio of each component in the binding liquid and the composite solvent system, the magnetic filling slurry has good printability and thixotropy, and can meet the performance requirements as a screen printing filling slurry.

Description

Technical Field

[0001] The present invention relates to the technical field of power inductors, and in particular to a magnetic filling slurry and a preparation method and application thereof. Background Art

[0002] Power inductors, as one of the basic components of electronic circuits, are widely used in electronic circuit products. With the trend toward miniaturization and integration of electronics, miniaturized multilayer inductors capable of meeting high current and high power requirements require a high electrode line aspect ratio. The trench filling process allows for thicker electrodes and prevents electrode collapse during lamination, thus achieving an optimal aspect ratio.

[0003] CN 108623288A discloses a beryllium oxide ceramic tape-casting slurry and its production method. The beryllium oxide ceramic tape-casting slurry is composed of 50%-70% powder and 30%-50% organic solvent by weight. After pre-ball milling and double ball milling, the resulting slurry has good tape-casting performance.

[0004] CN 104446518A provides a water-based tape-casting slurry for NFC magnetic cores. The slurry includes ferrite powder, a dispersant, a binder, a plasticizer, and deionized water. Based on the total mass of the slurry, the ferrite content is 60-75wt%, the dispersant content is 0.3-1wt%, the binder content is 4-10wt%, the plasticizer content is 3-6wt%, and the remainder is deionized water. The binder is a mixture of polyvinyl alcohol and polyacrylic acid. The slurries provided by the above two inventions have relatively low solid content and low viscosity, making them only suitable for tape-casting and not suitable for screen printing.

[0005] CN 101354948A discloses a method for manufacturing a chip inductor, including screen printing, casting, binder removal, and sintering steps. In the screen printing step, the wire groove of the screen printing frame is 0.5-0.85 times the width, and a photosensitive latex column is provided at one end of the wire groove. The screen printing frame is placed on a base casting die sheet, and a wire conductor slurry is printed on the wire groove of the frame to form an internal electrode. Then, a dielectric slurry is printed on the entire surface of the screen printing frame to form a dielectric die sheet, and through holes are formed at the photosensitive latex columns. The screen printing frame is repeatedly placed, and the wire conductor slurry and dielectric slurry are printed to form the magnetic body of the laminated inductor. The wire conductor slurry in this invention has a low solid content and is prone to agglomeration and sedimentation.

[0006] In view of the shortcomings of the existing technology, there is an urgent need to provide a magnetic filling slurry with good stability, thixotropy and viscosity that is suitable for screen printing process. Summary of the Invention

[0007] The purpose of the present invention is to provide a magnetic filling slurry and its preparation method and application. By introducing ferrite as an insulating coating agent to ensure the high magnetic permeability of soft magnetic alloy powder, and at the same time, by combining a suitable binder and a composite solvent and adjusting a reasonable ratio, the prepared magnetic filling slurry has good printability and magnetic permeability, and can be used for screen printing to prepare high-current laminated power inductors.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a magnetic filling slurry, wherein the raw materials of the magnetic filling slurry include, by weight: 95-99 parts of soft magnetic alloy powder, 1-5 parts of ferrite powder, 10-20 parts of a binder, 3-6 parts of a first composite solvent, 0.3-0.6 parts of a dispersant, and 0.3-0.6 parts of a first plasticizer;

[0010] The bonding liquid includes a bonding agent, a second composite solvent, and a second plasticizer in a mass ratio of (3-4):(4-5):(3-1).

[0011] The weight proportion of the soft magnetic alloy powder is 95-99 parts, for example, 95 parts, 96 parts, 97 parts, 98 parts or 99 parts, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0012] The weight portion of the ferrite powder is 1-5 parts, for example, 1 part, 2 parts, 3 parts, 4 parts or 5 parts, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0013] The weight portion of the adhesive is 10-20 parts, for example, 10 parts, 12 parts, 15 parts, 18 parts or 20 parts, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0014] The weight proportion of the first composite solvent is 3-6 parts, for example, 3 parts, 3.5 parts, 4 parts, 5 parts or 6 parts, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0015] The weight portion of the dispersant is 0.3-0.6 parts, for example, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts or 0.6 parts, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0016] The weight portion of the first plasticizer is 0.3-0.6 parts, for example, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts or 0.6 parts, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0017] The mass ratio of the binder, the second composite solvent and the second plasticizer is (3-4):(4-5):(3-1), for example, it can be 3:4:3, 3.2:4.3:2.5, 3.5:4.5:2, 3.8:4.7:1.5 or 4:5:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0018] The magnetic filling slurry provided by the present invention has a high solid content. The introduction of ferrite powder as an insulating coating agent can make the soft magnetic alloy powder have a high magnetic permeability. At the same time, the insulating coating agent has the characteristic of high resistivity, which ensures the magnetic dilution effect of the insulating coating agent on the soft magnetic alloy powder. By regulating the ratio of each component in the adhesive liquid system, the slurry has good printability, is not easy to dry and block the screen during the printing process, and is not easy to flow and spread after printing. It is easy to dry and can meet the performance requirements of screen printing filling slurry.

[0019] Preferably, the soft magnetic alloy powder includes FeSiCr alloy powder and / or FeSiAl alloy powder.

[0020] Preferably, the particle size range of the soft magnetic alloy powder is 4-20 μm, for example, it can be 4 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0021] Preferably, the ferrite powder includes any one of NiZn ferrite powder, MnZn ferrite powder, NiCuZn ferrite powder or Sr3Co2 ferrite powder, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of NiZn ferrite powder and MnZn ferrite powder, a combination of NiCuZn ferrite powder and Sr3Co2 ferrite powder, a combination of NiZn ferrite powder, MnZn ferrite powder and NiCuZn ferrite powder, a combination of MnZn ferrite powder, NiCuZn ferrite powder and Sr3Co2 ferrite powder, or a combination of NiZn ferrite powder, MnZn ferrite powder, NiCuZn ferrite powder and Sr3Co2 ferrite powder.

[0022] Preferably, the median particle size D50 of the ferrite powder is less than 1 μm, for example, it can be 1 μm, 0.8 μm, 0.5 μm, 0.3 μm or 0.1 μm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0023] Preferably, the binder comprises a thermoplastic resin.

[0024] Preferably, the thermoplastic resin includes polyvinyl butyral and / or polymethyl methacrylate.

[0025] Preferably, the number average molecular weight of the thermoplastic resin is 60,000-220,000, for example, 60,000, 80,000, 100,000, 120,000, 150,000, 180,000, 200,000 or 220,000, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0026] Preferably, the glass transition temperature of the thermoplastic resin is ≤80°C, for example, it can be 80°C, 79°C, 78°C, 77°C, 76°C or 75°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0027] Preferably, the first composite solvent and the second composite solvent independently comprise a first solvent and a second solvent in a mass ratio of 1:(1.5-3), for example, 1:1.5, 1:2, 1:2.5 or 1:3, but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0028] Preferably, the first solvent comprises terpineol.

[0029] Preferably, the second solvent includes an aromatic solvent and / or an alcohol solvent.

[0030] The composite solvent provided by the present invention can effectively adjust the volatility of the slurry. The first solvent has a high boiling point and evaporates slowly. When blended with the second solvent with a low boiling point, the printed slurry can be easily dried and solidified, thereby improving the printing effect.

[0031] Preferably, the aromatic solvent comprises xylene and / or toluene.

[0032] Preferably, the alcohol solvent includes any one or a combination of at least two of n-propanol, isopropanol or ethanol. Typical but non-limiting combinations include a combination of n-propanol and isopropanol, a combination of isopropanol and ethanol, a combination of n-propanol and ethanol, or a combination of n-propanol, isopropanol and ethanol.

[0033] Preferably, the dispersant comprises any one or a combination of at least two of castor oil, industrial fish oil or triolein. Typical but non-limiting combinations include a combination of castor oil and industrial fish oil, a combination of industrial fish oil and triolein, a combination of castor oil and triolein, or a combination of castor oil, industrial fish oil and triolein.

[0034] Preferably, the first plasticizer and the second plasticizer independently include any one of dioctyl phthalate, dibutyl phthalate or a polyether compound having at least two hydroxyl functional groups, or a combination of at least two of them. Typical but non-limiting combinations include a combination of dioctyl phthalate and dibutyl phthalate, a combination of dibutyl phthalate and a polyether compound having at least two hydroxyl functional groups, a combination of dioctyl phthalate and a polyether compound having at least two hydroxyl functional groups, or a combination of dioctyl phthalate, dibutyl phthalate and a polyether compound having at least two hydroxyl functional groups.

[0035] In a second aspect, the present invention provides a method for preparing the magnetic filling slurry as described in the first aspect, the preparation method comprising the following steps:

[0036] (1) uniformly mixing the soft magnetic alloy powder, the ferrite powder, the first composite solvent, and the dispersant by ball milling according to the formula to obtain a dispersed slurry;

[0037] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) according to the formula amount to obtain a mixture;

[0038] (3) The mixture obtained in step (2) is filtered and vacuum degassed in sequence to obtain the magnetic filling slurry.

[0039] The preparation method of the magnetic filling slurry provided by the present invention adopts segmented ball milling to ensure that the soft magnetic alloy powder and the ferrite powder are fully wetted and evenly dispersed in the slurry, thereby effectively improving the fusion effect of each component in the magnetic filling slurry and the stability of the slurry.

[0040] Preferably, the rotation speed of the ball milling mixing in step (1) is 120-200 rpm, for example, it can be 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0041] Preferably, the ball milling mixing time in step (1) is 2-8 hours, for example, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0042] Preferably, during the ball milling mixing in step (1), ball milling media are added, and the ball milling media include zirconium balls.

[0043] Preferably, the mass ratio of the balls to the materials during the ball milling mixing in step (1) is (1-2):1, for example, it can be 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0044] Preferably, the preparation steps of the bonding liquid in step (2) are: fully mixing the second solvent and the bonding agent according to the formula amount, then adding the first solvent and the second plasticizer according to the formula amount, and mixing by ball milling to obtain the bonding liquid.

[0045] The “fully mixed” refers to slowly adding the binder to the second solvent and continuously stirring until the binder is dispersed and swelled.

[0046] The present invention prepares the binder into a binder liquid and then performs ball milling, rather than directly using the binder for ball milling. This is because the binder is in a solid state under normal conditions, and only by first using a solvent to fully dissolve it can the binder and powder be effectively mixed evenly and the slurry be prevented from agglomerating.

[0047] Preferably, the rotation speed of the ball milling is 120-200 rpm, for example, 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0048] Preferably, the ball milling mixing time is 2-8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0049] Preferably, the rotation speed of the ball milling mixing in step (2) is 120-200 rpm, for example, it can be 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0050] Preferably, the ball milling mixing time in step (2) is 18-24 hours, for example, it can be 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0051] Preferably, the filtering method in step (3) is screen filtration.

[0052] Preferably, the vacuum degassing time in step (3) is 10-15 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0053] The vacuum degassing can improve the gas content in the filtered magnetic filling slurry, thereby improving the quality of the obtained product.

[0054] Preferably, the vacuum degree of the vacuum degassing in step (3) is -0.08-0.09 MPa, for example, it can be -0.08 MPa, -0.082 MPa, -0.085 MPa, -0.088 MPa or -0.09 MPa, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0055] As a preferred technical solution of the preparation method described in the second aspect of the present invention, the preparation method comprises the following steps:

[0056] (1) uniformly mixing the soft magnetic alloy powder, ferrite powder, the first composite solvent, and the dispersant by ball milling at a speed of 120-200 rpm for 2-8 hours to obtain a dispersed slurry;

[0057] The mass ratio of the balls and materials during the ball milling is (1-2):1;

[0058] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 120-200 rpm according to the formula amount for 18-24 hours to obtain a mixture;

[0059] The preparation steps of the bonding liquid are as follows: fully mixing the second solvent and the bonding agent according to the formula amount, then adding the first solvent and the second plasticizer according to the formula amount, and ball milling and mixing at a speed of 120-200 rpm for 2-8 hours to obtain the bonding liquid;

[0060] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.08-0.09 MPa for 10-15 minutes to obtain the magnetic filling slurry.

[0061] In a third aspect, the present invention provides an application of the magnetic filling slurry as described in the first aspect, wherein the magnetic filling slurry is applied to the preparation of a high current laminated power inductor.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The magnetic filling slurry provided by the present invention introduces ferrite powder as an insulating coating agent, so that the soft magnetic alloy powder has high magnetic permeability. At the same time, the insulating coating agent has the characteristic of high resistivity, ensuring the magnetic dilution effect of the insulating coating agent on the soft magnetic alloy powder. By regulating the ratio of each component in the adhesive liquid system and introducing a composite solvent, the magnetic filling slurry has good printability and thixotropy. The viscosity at 10 r / min can reach 280 Pa·s, the thixotropy coefficient is 1.82, the printing process is not easy to dry out and block the screen, the slurry is not easy to flow and spread after printing, and is easy to dry, which can meet the performance requirements of screen printing filling slurry. The present invention adopts a segmented ball milling method, which can significantly improve the stability and uniformity of the magnetic filling slurry, and is not easy to agglomerate and settle after long-term storage. DETAILED DESCRIPTION

[0064] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0065] Example 1

[0066] This embodiment provides a magnetic filling slurry. The raw materials of the magnetic filling slurry include, in parts by weight: 97 parts of FeSiCr alloy powder, 3 parts of NiZn ferrite powder, 15 parts of a binder, 4 parts of a first composite solvent, 0.4 parts of castor oil, and 0.4 parts of a first plasticizer; the binder is polyvinyl butyral, a second composite solvent, and a second plasticizer in a mass ratio of 3.5:4.5:2; the first composite solvent and the second composite solvent are both terpineol and ethanol in a mass ratio of 1:2; the first plasticizer and the second plasticizer are both dioctyl phthalate; the median particle size D50 of the FeSiCr alloy powder is 12 μm, and the median particle size D50 of the NiZn ferrite powder is 0.7 μm.

[0067] The magnetic filling slurry is obtained by the following preparation method, which comprises the following steps:

[0068] (1) uniformly mixing FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, and castor oil according to the formula amount by ball milling at a rotation speed of 160 rpm for 5 hours to obtain a dispersed slurry;

[0069] The ball-to-material mass ratio during ball milling is 1.5:1;

[0070] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 160 rpm according to the formula amount for 21 hours to obtain a mixture;

[0071] The adhesive solution is prepared by fully mixing ethanol and polyvinyl butyral according to the formula amount, then adding terpineol and a second plasticizer according to the formula amount, and ball milling at a speed of 160 rpm for 5 hours to obtain the adhesive solution;

[0072] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.085 MPa for 12 minutes to obtain the magnetic filling slurry.

[0073] Example 2

[0074] This embodiment provides a magnetic filling slurry. The raw materials of the magnetic filling slurry include, in parts by weight: 96 parts of FeSiCr alloy powder, 4 parts of NiZn ferrite powder, 12 parts of a binder, 3.5 parts of a first composite solvent, 0.35 parts of castor oil, and 0.35 parts of a first plasticizer; the binder is polyvinyl butyral, a second composite solvent, and a second plasticizer in a mass ratio of 3.5:4.5:2; the first composite solvent and the second composite solvent are both terpineol and ethanol in a mass ratio of 1:2; the first plasticizer and the second plasticizer are both dioctyl phthalate; the median particle size D50 of the FeSiCr alloy powder is 11 μm, and the median particle size D50 of the NiZn ferrite powder is 0.6 μm.

[0075] The magnetic filling slurry is obtained by the following preparation method, which comprises the following steps:

[0076] (1) uniformly mixing FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, and castor oil according to the formula amount by ball milling at a rotation speed of 140 rpm for 6.5 hours to obtain a dispersed slurry;

[0077] The ball-to-material mass ratio during ball milling is 1.2:1;

[0078] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 140 rpm according to the formula amount for 22 hours to obtain a mixture;

[0079] The adhesive solution is prepared by fully mixing ethanol and polyvinyl butyral according to the formula amount, then adding terpineol and a second plasticizer according to the formula amount, and ball milling at a speed of 140 rpm for 6.5 hours to obtain the adhesive solution;

[0080] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.082 MPa for 11 minutes to obtain the magnetic filling slurry.

[0081] Example 3

[0082] This embodiment provides a magnetic filling slurry. The raw materials of the magnetic filling slurry include, in parts by weight: 98 parts of FeSiCr alloy powder, 2 parts of NiZn ferrite powder, 18 parts of a binder, 5 parts of a first composite solvent, 0.5 parts of castor oil, and 0.5 parts of a first plasticizer; the binder is polyvinyl butyral, a second composite solvent, and a second plasticizer in a mass ratio of 3.5:4.5:2; the first composite solvent and the second composite solvent are both terpineol and ethanol in a mass ratio of 1:2.5; the first plasticizer and the second plasticizer are both dioctyl phthalate; the median particle size D50 of the FeSiCr alloy powder is 13 μm, and the median particle size D50 of the NiZn ferrite powder is 0.8 μm.

[0083] The magnetic filling slurry is obtained by the following preparation method, which comprises the following steps:

[0084] (1) uniformly mixing FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, and castor oil according to the formula amount by ball milling at a rotation speed of 180 rpm for 3.5 hours to obtain a dispersed slurry;

[0085] The ball-to-material mass ratio during ball milling is 1.8:1;

[0086] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 180 rpm according to the formula amount for 20 hours to obtain a mixture;

[0087] The adhesive solution is prepared by fully mixing ethanol and polyvinyl butyral according to the formula amount, then adding terpineol and a second plasticizer according to the formula amount, and ball milling at a speed of 180 rpm for 3.5 hours to obtain the adhesive solution;

[0088] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.088 MPa for 13 minutes to obtain the magnetic filling slurry.

[0089] Example 4

[0090] This embodiment provides a magnetic filling slurry. The raw materials of the magnetic filling slurry include, in parts by weight: 95 parts of FeSiCr alloy powder, 5 parts of NiZn ferrite powder, 10 parts of a binder, 3 parts of a first composite solvent, 0.3 parts of castor oil, and 0.3 parts of a first plasticizer; the binder is polyvinyl butyral, a second composite solvent, and a second plasticizer in a mass ratio of 3.5:4.5:2; the first composite solvent and the second composite solvent are both terpineol and ethanol in a mass ratio of 1:1.5; the first plasticizer and the second plasticizer are both dioctyl phthalate; the median particle size D50 of the FeSiCr alloy powder is 10 μm, and the median particle size D50 of the NiZn ferrite powder is 0.5 μm.

[0091] The magnetic filling slurry is obtained by the following preparation method, which comprises the following steps:

[0092] (1) uniformly mixing FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, and castor oil according to the formula amount by ball milling at a speed of 120 rpm for 8 hours to obtain a dispersed slurry;

[0093] The ball-to-material mass ratio during ball milling is 1:1;

[0094] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 120 rpm according to the formula amount for 24 hours to obtain a mixture;

[0095] The adhesive solution is prepared by fully mixing ethanol and polyvinyl butyral according to the formula amount, then adding terpineol and a second plasticizer according to the formula amount, and ball milling at a rotation speed of 120 rpm for 8 hours to obtain the adhesive solution;

[0096] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.08 MPa for 10 minutes to obtain the magnetic filling slurry.

[0097] Example 5

[0098] This embodiment provides a magnetic filling slurry. The raw materials of the magnetic filling slurry include, in parts by weight: 99 parts of FeSiCr alloy powder, 1 part of NiZn ferrite powder, 20 parts of a binder, 6 parts of a first composite solvent, 0.6 parts of castor oil, and 0.6 parts of a first plasticizer; the binder is polyvinyl butyral, a second composite solvent, and a second plasticizer in a mass ratio of 3.5:4.5:2; the first composite solvent and the second composite solvent are both terpineol and ethanol in a mass ratio of 1:3; the first plasticizer and the second plasticizer are both dioctyl phthalate; the median particle size D50 of the FeSiCr alloy powder is 14 μm, and the median particle size D50 of the NiZn ferrite powder is 1 μm.

[0099] The magnetic filling slurry is obtained by the following preparation method, which comprises the following steps:

[0100] (1) uniformly mixing FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, and castor oil according to the formula amount by ball milling at a speed of 200 rpm for 2 hours to obtain a dispersed slurry;

[0101] The ball-to-material mass ratio during ball milling is 2:1;

[0102] (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a speed of 200 rpm according to the formula amount for 18 hours to obtain a mixture;

[0103] The adhesive solution is prepared by fully mixing ethanol and polyvinyl butyral according to the formula amount, then adding terpineol and a second plasticizer according to the formula amount, and ball milling at a speed of 200 rpm for 2 hours to obtain the adhesive solution;

[0104] (3) The mixture obtained in step (2) was filtered through a sieve and vacuum degassed at -0.09 MPa for 15 minutes to obtain the magnetic filling slurry.

[0105] Example 6

[0106] This embodiment provides a magnetic filling slurry, which is different from Example 1 in that, except that the binder is adjusted to a mass ratio of 3:4:3 for polyvinyl butyral, a second composite solvent, and a second plasticizer, the rest is the same as Example 1.

[0107] Example 7

[0108] This embodiment provides a magnetic filling slurry, which is different from Example 1 in that, except that the binder is adjusted to a mass ratio of 4:5:1 for polyvinyl butyral, a second composite solvent, and a second plasticizer, the rest is the same as Example 1.

[0109] Example 8

[0110] This embodiment provides a magnetic filling slurry, which is different from Example 1 in that, except that the first composite solvent and the second composite solvent are both adjusted to a mass ratio of 1:1 between terpineol and ethanol, the rest are the same as Example 1.

[0111] Example 9

[0112] This embodiment provides a magnetic filling slurry, which is different from Example 1 in that, except that the first composite solvent and the second composite solvent are both adjusted to a mass ratio of terpineol to ethanol of 1:4, the rest are the same as Example 1.

[0113] Comparative Example 1

[0114] This comparative example provides a magnetic filling slurry, which is different from Example 1 in that, except that the FeSiCr alloy powder is adjusted to 90 parts and the NiZn ferrite powder is adjusted to 10 parts, the rest is the same as Example 1.

[0115] Comparative Example 2

[0116] This comparative example provides a magnetic filling slurry, which is different from Example 1 in that, except that the NiZn ferrite powder is replaced by silicon dioxide nanopowder in equal parts, the rest is the same as Example 1.

[0117] Comparative Example 3

[0118] This comparative example provides a magnetic filling slurry, which differs from Example 1 in that the raw materials of the magnetic filling slurry do not include NiZn ferrite powder, and the rest are the same as Example 1.

[0119] Comparative Example 4

[0120] This comparative example provides a magnetic filling slurry, which is different from Example 1 in that, except that the binder is adjusted to a mass ratio of 2:6:2 for polyvinyl butyral, the second composite solvent, and the second plasticizer, the rest are the same as Example 1.

[0121] Comparative Example 5

[0122] This comparative example provides a magnetic filling slurry, which is different from Example 1 in that, except that the first composite solvent and the second composite solvent in the raw materials of the magnetic filling slurry are replaced by a single solvent ethanol in equal parts, the rest is the same as Example 1.

[0123] Comparative Example 6

[0124] This comparative example provides a magnetic filling slurry, which differs from Example 1 in that steps (1) and (2) in the preparation method of the magnetic filling slurry are adjusted to: FeSiCr alloy powder, NiZn ferrite powder, a first composite solvent, castor oil, a binder, and a first plasticizer are uniformly ball-milled and mixed at a rotation speed of 160 rpm for 26 hours according to the formula amount, and the rest are the same as Example 1.

[0125] Comparative Example 7

[0126] This comparative example provides a magnetic filling slurry, which differs from Example 1 in that the raw materials of the magnetic filling slurry include: 97 parts of FeSiCr alloy powder, 3 parts of NiZn ferrite powder, 5.25 parts of binder, 10.75 parts of composite solvent, 0.4 parts of castor oil, and 3.4 parts of plasticizer. In the preparation method of the magnetic filling slurry, the binder is directly used without preparing it into a binding liquid. The first composite solvent is adaptively adjusted to a composite solvent, and the first plasticizer is adjusted to a plasticizer. The rest is the same as in Example 1.

[0127] Performance Testing

[0128] Viscosity: The magnetic filling slurries provided in Examples 1-9 and Comparative Examples 1-7 were subjected to viscosity testing using a Brookfield CV2T viscometer in a 25±1°C constant temperature bath with a 14# rotor. The viscosity values measured at 10 r / min are shown in Table 1.

[0129] Thixotropy: The magnetic filling slurries provided in Examples 1-9 and Comparative Examples 1-7 were subjected to a thixotropy test. The viscosity of the magnetic filling slurries was measured at 1 r / min and 5 r / min using a 14# rotor. The thixotropy index was calculated as shown in Table 1: thixotropy index K = η1 / η2 (η1 is the viscosity value at 1 r / min, η2 is the viscosity value at 5 r / min);

[0130] Printability: The magnetic filler pastes provided in Examples 1-9 and Comparative Examples 1-7 were printed and dried, and the printing effect and the drying effect at 70°C for 5 minutes were evaluated. The printing results were classified as "OK" or "NG" according to the printing conditions, as shown in Table 1.

[0131] Magnetic permeability: After printing and drying, the magnetic filling pastes provided in Examples 1-9 and Comparative Examples 1-7 were punched into magnetic rings and sintered side by side with glue. The magnetic permeability μ' was tested using an Agilent 4991a impedance analyzer and a 16454A fixture. The results are shown in Table 1.

[0132] Table 1

[0133]

[0134]

[0135] As can be seen from Table 1, by comparing Example 1 with Examples 2-5, it can be seen that the raw materials of the magnetic filling slurry are appropriately proportioned, and the prepared magnetic filling slurry has excellent printability, is not prone to dryness and blocking the screen during the printing process, and is not prone to flow and spread after printing and is easy to dry, thus meeting various performance requirements of the printing filling slurry.

[0136] Comparison of Example 1 with Example 6, Example 7, and Comparative Example 4 shows that the ratio of the components in the binder has a certain influence on the printability of the magnetic filling slurry. For example, if the ratio of the composite solvent in the binder is too high, the slurry will flow severely after printing and cannot be used. Comparison of Example 1 with Example 8 and Example 9 shows that if the ratio of the first solvent to the second solvent in the composite solvent exceeds the appropriate range, the magnetic filling slurry prepared will easily dry out and clog the screen, making it impossible to complete the subsequent process flow.

[0137] By comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that the proportion of ferrite powder in the magnetic filling slurry is too large, and the measured magnetic permeability is significantly reduced; when silica nanopowder is used instead of ferrite powder, the measured magnetic permeability is still reduced; by comparing Example 1 with Comparative Example 3, it can be seen that the magnetic filling slurry without adding ferrite powder loses the function of the insulating coating agent, and the thixotropy and magnetic permeability are reduced; by comparing Example 1 with Comparative Example 5, it can be seen that a single solvent is used to prepare the magnetic filling slurry, the solvent is extremely volatile, and the slurry is easy to agglomerate and block the network during the printing process; by comparing Example 1 with Comparative Example 6, it can be seen that ball milling the raw materials of the magnetic filling slurry together cannot ensure that the soft magnetic alloy powder and the ferrite powder are fully wetted, and cannot be evenly dispersed in the slurry, resulting in poor printability of the product; by comparing Example 1 with Comparative Example 7, it can be seen that directly using a binder for ball milling, the powder in the raw materials cannot be evenly dispersed, and the components are not fully fused, resulting in a significant decrease in the printability of the slurry.

[0138] In summary, the magnetic filling slurry provided by the present invention introduces ferrite powder as an insulating coating agent, so that the soft magnetic alloy powder has a higher magnetic permeability, and the insulating coating agent has the characteristic of high resistivity, thereby ensuring the magnetic dilution effect of the insulating coating agent on the soft magnetic alloy powder; by regulating the ratio of each component in the adhesive liquid system and introducing a composite solvent, the magnetic filling slurry has good printability and thixotropy, the viscosity at 10r / min can reach 280Pa·s, the thixotropy coefficient is 1.82, the printing process is not easy to dry out and block the screen, the slurry is not easy to flow and spread after printing, and is easy to dry, which can meet the performance requirements of screen printing filling slurry; the present invention adopts a segmented ball milling method, which can significantly improve the stability and uniformity of the magnetic filling slurry, and it is not easy to clump and settle after being placed for a long time.

[0139] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A magnetic filling slurry, characterized in that: The raw materials of the magnetic filling slurry include, by weight: 95-99 parts of soft magnetic alloy powder; 1-5 parts of ferrite powder; 10-20 parts of adhesive liquid; 3-6 parts of the first composite solvent; Dispersant 0.3-0.6 parts; 0.3-0.6 parts of the first plasticizer; The bonding liquid includes a bonding agent, a second composite solvent, and a second plasticizer in a mass ratio of (3-4):(4-5):(3-1); The first composite solvent and the second composite solvent independently include a first solvent and a second solvent in a mass ratio of 1:(1.5-3); the first solvent includes terpineol; the second solvent includes an aromatic solvent and / or an alcohol solvent; the alcohol solvent includes any one of n-propanol, isopropanol or ethanol, or a combination of at least two of them.

2. The magnetic filling slurry according to claim 1, characterized in that The soft magnetic alloy powder includes FeSiCr alloy powder and / or FeSiAl alloy powder.

3. The magnetic filling slurry according to claim 1, characterized in that The particle size of the soft magnetic alloy powder is in the range of 4-20 μm.

4. The magnetic filling slurry according to claim 1, characterized in that The ferrite powder includes any one of NiZn ferrite powder, MnZn ferrite powder, NiCuZn ferrite powder or Sr3Co2 ferrite powder, or a combination of at least two of them.

5. The magnetic filling slurry according to claim 1, characterized in that The median particle size D50 of the ferrite powder is less than 1 μm.

6. The magnetic filling slurry according to claim 1, characterized in that The binder includes a thermoplastic resin.

7. The magnetic filling slurry according to claim 6, characterized in that The thermoplastic resin includes polyvinyl butyral and / or polymethyl methacrylate.

8. The magnetic filling slurry according to claim 6, characterized in that The number average molecular weight of the thermoplastic resin is 60,000-220,000.

9. The magnetic filling slurry according to claim 1, characterized in that The aromatic solvent includes xylene and / or toluene.

10. The magnetic filling slurry according to claim 1, characterized in that The dispersant includes any one of castor oil, industrial fish oil or triolein or a combination of at least two thereof.

11. The magnetic filling slurry according to claim 1, characterized in that The first plasticizer and the second plasticizer independently include any one of dioctyl phthalate, dibutyl phthalate, or a polyether compound with at least two hydroxyl functional groups, or a combination of at least two of them.

12. A method for preparing the magnetic filling slurry according to any one of claims 1 to 11, characterized in that: The preparation method comprises the following steps: (1) uniformly mixing the soft magnetic alloy powder, the ferrite powder, the first composite solvent and the dispersant by ball milling according to the formula to obtain a dispersed slurry; (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) according to the formula to obtain a mixture; (3) The mixture obtained in step (2) is filtered and vacuum degassed in sequence to obtain the magnetic filling slurry.

13. The preparation method according to claim 12, characterized in that The rotation speed of the ball milling mixing in step (1) is 120-200 rpm.

14. The preparation method according to claim 12, characterized in that The ball milling mixing time in step (1) is 2-8 hours.

15. The preparation method according to claim 12, characterized in that During the ball milling mixing in step (1), ball milling media is added, and the ball milling media includes zirconium balls.

16. The preparation method according to claim 12, characterized in that The mass ratio of the balls and materials during the ball milling mixing in step (1) is (1-2):

1.

17. The preparation method according to claim 12, characterized in that The preparation steps of the bonding liquid in step (2) are as follows: the second solvent and the bonding agent are fully mixed according to the formula amount, and then the first solvent and the second plasticizer are added according to the formula amount, and the bonding liquid is obtained by ball milling.

18. The preparation method according to claim 17, characterized in that: The rotation speed of the ball milling mixing is 120-200 rpm.

19. The preparation method according to claim 17, characterized in that The ball milling mixing time is 2-8 hours.

20. The preparation method according to claim 12, characterized in that The rotation speed of the ball milling mixing in step (2) is 120-200 rpm.

21. The preparation method according to claim 12, characterized in that The ball milling mixing time in step (2) is 18-24 hours.

22. The preparation method according to claim 12, characterized in that The filtration method in step (3) is screen filtration.

23. The preparation method according to claim 12, characterized in that The vacuum degassing time in step (3) is 10-15 minutes.

24. The preparation method according to claim 12, characterized in that The vacuum degree of the vacuum degassing in step (3) is -0.08-0.09 MPa.

25. The preparation method according to claim 12, characterized in that The preparation method comprises the following steps: (1) uniformly mixing the soft magnetic alloy powder, ferrite powder, the first composite solvent and the dispersant by ball milling at a speed of 120-200 rpm for 2-8 hours according to the formula to obtain a dispersed slurry; The mass ratio of the balls and materials during the ball milling is (1-2):1; (2) ball milling the binder, the first plasticizer, and the dispersed slurry obtained in step (1) at a rotation speed of 120-200 rpm according to the formula amount for 18-24 hours to obtain a mixture; The preparation steps of the bonding liquid are as follows: fully mixing the second solvent and the bonding agent according to the formula amount, then adding the first solvent and the second plasticizer according to the formula amount, and ball milling and mixing at a speed of 120-200 rpm for 2-8 hours to obtain the bonding liquid; (3) The mixture obtained in step (2) is filtered through a sieve and vacuum degassed at -0.08-0.09 MPa for 10-15 minutes to obtain the magnetic filling slurry.

26. A use of the magnetic filling slurry according to any one of claims 1 to 11, characterized in that: The magnetic filling slurry is used for preparing high-current laminated power inductors.

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