Ferrite material and method for producing the same

Abstract

The application discloses a kind of ferrite material and preparation method thereof, belong to inductance material field.The ferrite material includes main component and additive;The additive includes the following mass percentage component: Bi2O360%-80%, MoO3 10%-30%, SiO2 5%-20%.Bi2O3, MoO3, SiO2 of specific mass percentage content are used as additive and NiCuZn compound in the application, improve the magnetic permeability and thermal conductivity of inductor device product, guarantee the working life of device.

Description

Technical Field

[0001] This invention relates to the field of inductor materials, specifically to a ferrite material and its preparation method. Background Technology

[0002] Multilayer chip inductors, as the mainstream type of chip inductor, are commonly used in surface-mount digital circuits. Therefore, many researchers are constantly improving their electrical performance. NiCuZn soft magnetic ferrite, as a fundamental electronic functional material for chip inductors, has the advantages of good thermal shock resistance, high reliability, and long service life. The sintering temperature of NiCuZn ferrite materials prepared by traditional ceramic processes is generally above 1000℃. In order to be compatible with low-temperature co-fired ceramic technology, it is necessary to add a certain amount of low-melting-point trace element additives that can aid sintering, and reduce the overall sintering temperature of the product through liquid-phase sintering.

[0003] CN115028443A discloses a multilayer ferrite inductor material, which obtains a multilayer ferrite inductor material with good stability and low solderability by adding a specific amount of glass powder B containing SiO2, Al2O3, B2O3, NaCO3, BaCO3, and CaCO3 to NiCuZn ferrite material; however, this prior art does not improve the thermal conductivity and service life of ferrite materials.

[0004] To address the problems existing in the aforementioned ferrite materials, developing a ferrite material with high electrical stability and long service life is currently the focus of research. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a ferrite material with high electrical stability and long service life, as well as a method for its preparation.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A ferrite material comprising a main component and additives; the additives comprising the following components in mass percentage: Bi₂O₃ 60%-80%, MoO₃ 10%-30%, SiO₂ 5%-20%.

[0008] This invention uses Bi2O3, MoO3, and SiO2 as additives. The change in the magnet phase structure of the additive system is caused by the liquid phase sintering mechanism. The additives melt into a glassy state first during the sintering process, which can significantly reduce the crystal structure binding energy of the ferrite material, thereby promoting the nucleation rate of the powder during sintering, enhancing the densification of the magnet, and making the crystal phase structure of the magnet highly uniform. This allows the NiCuZn ferrite material to achieve a high volume density at a lower temperature, which is beneficial to improving the functional properties of the ferrite magnet.

[0009] The inventors discovered that the mass percentage of Bi2O3, MoO3, and SiO2 in the additive has a significant impact on the phase structure of the ferrite material. When the mass percentage of Bi2O3, MoO3, and SiO2 is within the above-mentioned range, it can be guaranteed that the final inductor device product has high thermal conductivity, long service life, and stable electrical performance.

[0010] The inventors also discovered that Bi2O3, MoO3, and SiO2 are indispensable components of this invention. If MoO3 is lacking, the final sintered ferrite magnet grains in the additive system will have a small grain size, an increased number of grain boundaries, poor heat dissipation (i.e., low thermal conductivity), affecting the product's lifespan and increasing the rate of change of the product's impedance Z-performance value after reflow soldering. If SiO2 is lacking, the final sintered ferrite magnet grains in the additive system will have an excessively large grain size, an increase in multi-domain grains, and a slight decrease in the product's magnetic permeability, deviating from the reasonable range. Furthermore, the rate of change of the product's impedance Z-performance value after reflow soldering will increase. If Bi2O3 is lacking, the ferrite sintering will be insufficient, resulting in a significant decrease in magnetic permeability, deviating from the reasonable range. Low crystallinity will also worsen heat dissipation, reducing the magnet's thermal conductivity and causing heat accumulation during use, thus affecting the product's lifespan.

[0011] When the three additives mentioned above are used together, they can synergistically improve the electromagnetic physical properties of the product, resulting in inductor devices with high thermal conductivity, long service life, and stable electrical performance.

[0012] As a preferred embodiment of the ferrite material of the present invention, the additive includes the following components in mass percentage: Bi2O3 60%-70%, MoO3 10%-25%, SiO2 5%-15%. The inventors have found through a large number of experiments that when the components in the additive are within the above-mentioned preferred mass percentage range, the final product can be guaranteed to have higher thermal conductivity, longer service life and more stable electrical performance.

[0013] As a preferred embodiment of the ferrite material of the present invention, the mass percentage of additives in the ferrite material is 1%-3%. The inventors have found that excessive mass percentage of additives will increase the non-magnetic structural phase, reduce the magnetic permeability of the magnet, and cause a significant decrease in the permeability of the material. This will result in a significant decrease in the grain size of the sample magnet, with the grain diameter ranging from 0.5 to 2 μm. The increased number of grains, grain boundaries, and grain boundary thickness will hinder heat transfer and significantly reduce the thermal conductivity. This will cause the product's impedance Z-performance value and service life performance to fail to meet the standards. On the other hand, when too little additives are added, the average grain size of the ferrite magnet in the additive system will be too large, with the grain diameter mostly ranging from 5 to 15 μm. There will be fewer single-domain grains and more multi-domain grains. The appearance of crystal defects such as pores and bubbles on the grains will increase the instability of the magnet structure. The magnetic permeability of the magnet will be too high and deviate from the reasonable range. The product performance value will show a large change rate of impedance value after reflow soldering.

[0014] As a preferred embodiment of the ferrite material of the present invention, the main components include the following components in molar percentage: Fe2O3 40%-50%, ZnO 25%-35%, NiO 10%-20%, CuO 5%-10%.

[0015] In a second aspect, the present invention provides a method for preparing the ferrite material described in the first aspect, the method comprising the following steps:

[0016] Preparation of the main component: Mix and pre-calcine the raw materials in the main component to obtain the main component;

[0017] Preparation of additives: Mix and grind the raw materials in the additive to obtain the additive;

[0018] Preparation of ferrite material: The main components and additives are mixed, ground, dried, granulated, and then pressed and sintered to obtain the ferrite material.

[0019] In a preferred embodiment of the preparation method of the ferrite material of the present invention, the sintering temperature is 910-930℃, the temperature rise rate is 2.5-2.8℃ / min, the sintering time is 8-10h, and the holding time is 2-4h.

[0020] Through extensive experiments, the inventors discovered that sintering temperature and sintering time have a significant impact on the performance of ferrite materials. If the sintering temperature is too low, it will affect the nucleation rate and degree of crystallization, resulting in low magnetic permeability. If the sintering temperature is too high, it will cause the grains to be overburned, resulting in poor uniformity of crystal size and excessively high magnetic permeability. If the sintering time is too long, it will cause abnormal grain growth and change the uniformity of grains. If the sintering time is too short, it will not be able to sinter sufficiently.

[0021] In a preferred embodiment of the preparation method of the ferrite material of the present invention, the pressing step is as follows: the granulated mixture is placed in a mold and pressed into a magnetic ring or magnetic sheet under a pressure of 295-305 MPa. The magnetic ring has an outer diameter of 22.5 mm, an inner diameter of 11.5 mm, and a height of 4.5-5.5 mm; the magnetic sheet has a diameter of 24 mm.

[0022] In a preferred embodiment of the preparation method of the ferrite material of the present invention, the main components are mixed by ball milling and sand milling.

[0023] In a preferred embodiment of the preparation method of the ferrite material of the present invention, the pre-firing temperature of the main component is 830-850℃ and the pre-firing time is 3-4h.

[0024] In a preferred embodiment of the preparation method of the ferrite material of the present invention, the main component and additives are mixed and ground to a particle size of 0.8-1.2 μm.

[0025] The present invention also provides a multilayer chip inductor, wherein the multilayer chip inductor is made of the ferrite material described in the first aspect.

[0026] In a preferred embodiment of the multilayer chip inductor of the present invention, the multilayer chip inductor further includes a casting agent carrier.

[0027] As a more preferred embodiment of the multilayer chip inductor of the present invention, the casting agent carrier includes a resin binder, a dispersant, anhydrous ethanol and n-propyl acetate.

[0028] As the most preferred embodiment of the multilayer chip inductor of the present invention, the mass percentage of each component based on ferrite material is as follows: resin binder 40%-50%, dispersant 1%-10%, anhydrous ethanol 5%-10%, and n-propyl acetate 30%-40%.

[0029] Preferably, the resin adhesive is a phenolic epoxy resin, which has good adhesion to metal oxide substrates and excellent mechanical properties. The dispersant is a polyacrylic acid polymer, which is a surfactant with both lipophilic and hydrophilic properties. It can rapidly wet the surface of solid particles and raise the energy barrier between solid particles to a sufficiently high level.

[0030] In a preferred embodiment of the multilayer chip inductor of the present invention, the multilayer chip inductor is fabricated by the following method:

[0031] Ferrite material and casting agent carrier are mixed into a slurry, which is then cast, printed, isostatically pressed, cut and sintered to obtain the multilayer chip inductor device.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention provides a ferrite material that uses Bi2O3, MoO3, and SiO2 in specific mass percentages as additives to composite with NiCuZn, thereby improving the magnetic permeability and thermal conductivity of inductor products and ensuring the working life of the devices. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the magnetic ring (left) and magnetic sheet (right) after being pressed from the ferrite material of this invention. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the methods or operations used in the embodiments are conventional methods or operations in the art.

[0036] Examples 1-5 and Comparative Examples 1-5

[0037] Examples 1-5 and Comparative Examples 1-5 are ferrite materials of the present invention. The composition and weight percentage of the ferrite materials of Examples 1-5 and Comparative Examples 1-5 are shown in Tables 1 and 2.

[0038] The preparation methods of the ferrite materials described in Examples 1-5 and Comparative Examples 1-5 include the following steps:

[0039] Preparation of the main component: Mix and pre-calcine the raw materials in the main component to obtain the main component;

[0040] Preparation of additives: Mix and grind the raw materials in the additive to obtain the additive;

[0041] Preparation of ferrite material: The main components and additives are mixed, ground, dried, granulated, and then pressed and sintered to obtain the ferrite material.

[0042] The sintering temperature is 910-930℃, the temperature rise rate is 2.5-2.8℃ / min, the sintering time is 8-10h, and the holding time is 2-4h.

[0043] The fabrication methods of the multilayer chip inductor devices described in Examples 1-5 and Comparative Examples 1-5 are as follows:

[0044] The above-mentioned ferrite material and casting agent carrier are mixed into a slurry, and then cast, printed, isostatically pressed, cut and sintered to obtain the multilayer chip inductor device.

[0045] Table 1

[0046]

[0047] Table 2

[0048]

[0049]

[0050] Performance testing

[0051] 1. The magnetic rings and magnetic sheets of Examples 1-5 and Comparative Examples 1-5 were tested for magnetic permeability at 25°C using an E4991B impedance analyzer. The magnetic sheets were tested for thermal conductivity using a thermal conductivity measuring device. The thermal conductivity was measured using the YHO023-1801Z method with a modified transient plane heat source thermal conductivity meter. The results are shown in Table 3 below.

[0052] 2. The multilayer chip inductors of Examples 1-5 and Comparative Examples 1-5 were powered on at rated current for 1200 hours to determine their service life; the electrical performance change rate before and after reflow soldering was tested in a 260℃ reflow oven; the results are shown in Table 4 below.

[0053] Table 3

[0054]

[0055]

[0056] Table 4

[0057]

[0058]

[0059] As can be seen from Tables 3 and 4, when the technical solution of the present invention is adopted, the ferrite material obtained has an initial magnetic permeability of 110±5 and a thermal conductivity of ≥5.1W / (m·k) at 25℃; when a multilayer chip inductor is made, the device can effectively work for ≥1200h, and the change rate of electrical performance before and after reflow soldering at 260℃ is ≤10%.

[0060] Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the weight percentage of each component in the additive has a significant impact on the magnetic permeability and thermal conductivity of the ferrite material, the working life of the multilayer chip inductor, and the rate of change of electrical performance before and after reflow soldering. The final product in Example 1 can comprehensively demonstrate higher thermal conductivity, longer working life, and more stable electrical performance.

[0061] Comparing Example 1 and Comparative Examples 3-5, it can be seen that Bi2O3, MoO3, and SiO2 are all indispensable in this invention. If MoO3 is missing, the final ferrite magnet grains in the additive system will have a small grain size, an increased number of grain boundaries, poor heat dissipation (i.e., low thermal conductivity), affecting the service life and increasing the rate of change of the product's impedance Z-performance value after reflow soldering. If SiO2 is missing, the final ferrite magnet grains in the additive system will have an excessively large grain size, an increased number of multi-domain grains, and a decrease in the product's magnetic permeability. If the reduction is small, it deviates from the reasonable range, and the impedance Z-performance value of the product will change more rapidly after reflow soldering; if Bi2O3 is lacking, the ferrite sintering will be insufficient, the permeability will be greatly reduced and deviate from the reasonable range, the degree of crystallization will be low and the heat dissipation effect will be poor, that is, the thermal conductivity of the magnet will be reduced, causing the product to accumulate heat during use and affecting the working life. Example 1 is the combination of the above additive system, which can synergistically improve the electromagnetic physical characteristics of the product and obtain an inductor device product with high thermal conductivity, long working life and stable electrical performance.

[0062] Comparing Examples 1, 3, and 4, it can be seen that the mass percentage of additives also affects the performance of the final ferrite material and multilayer chip inductor. In Example 4, an excessive mass percentage of additives increases the non-magnetic structural phase, reducing the magnetic permeability of the magnet and causing a significant decrease in the permeability of the material. This results in a significant reduction in the size of the sample magnet grains, with the grain diameter ranging from 0.5 to 2 μm. The increased number of grains, grain boundaries, and grain boundary thickness hinder heat transfer, significantly reducing thermal conductivity. This leads to substandard impedance Z-performance and insufficient service life performance of the product. In Example 3, when too little additive is added, the average grain size of the ferrite magnet in the additive system is too large, with the grain diameter mostly ranging from 5 to 15 μm. There are fewer single-domain grains and more multi-domain grains. The presence of crystal defects such as pores and bubbles on the grains increases the instability of the magnet structure. The permeability of the magnet is too high, deviating from the reasonable range, and the product performance will show a large change in impedance value after reflow soldering.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A ferrite material, characterized in that, The ferrite material includes a main component and additives; The additive is composed of the following components in mass percentage: Bi2O3 60%-70%, MoO3 10%-25%, SiO2 5%-15%; The additive in the ferrite material has a mass percentage content of 1%-3%; The main components include the following components in molar percentage: Fe2O3 40%-50%, ZnO 25%-35%, NiO 10%-20%, CuO 5%-10%.

2. The method for preparing the ferrite material as described in claim 1, characterized in that, The method for preparing the ferrite material includes the following steps: Preparation of the main component: Mix and pre-calcine the raw materials in the main component to obtain the main component; Preparation of additives: Mix and grind the raw materials in the additive to obtain the additive; Preparation of ferrite material: The main components and additives are mixed, ground, dried, granulated, and then pressed and sintered to obtain the ferrite material.

3. The method for preparing the ferrite material as described in claim 2, characterized in that, The sintering temperature is 910-930℃, the temperature rise rate is 2.5-2.8℃ / min, the sintering time is 8-10h, and the holding time is 2-4h.

4. The method for preparing the ferrite material as described in claim 2, characterized in that, The pre-firing temperature of the main component is 830-850℃, and the pre-firing time is 3-4h.

5. A multilayer chip inductor, characterized in that, The multilayer chip inductor is made using the ferrite material described in claim 1.

6. The multilayer chip inductor as described in claim 5, characterized in that, The multilayer chip inductor is fabricated using the following method: Ferrite material and casting agent carrier are mixed into a slurry, which is then cast, printed, isostatically pressed, cut and sintered to obtain the multilayer chip inductor device.

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