Low-pressure molding of high-permeability, low-loss SMC materials and their preparation and application

Abstract

This invention discloses a low-pressure molded, high-permeability, low-loss SMC material, its preparation, and its application. Anhydrous ethanol is used as the dispersion medium to ultrasonically disperse carbonyl iron powder and nano-silica powder to prepare the SMC material. This improves the compatibility of iron-silicon-chromium, carbonyl iron powder, and epoxy resin, enhances the flexibility and impact resistance of the inductor material, and improves the magnetic properties of the SMC material. In this invention, the nano-silica is added through direct mixing and dispersion, without coating it on the surface of the magnetic powder, which greatly simplifies the manufacturing process and reduces costs. High-resistivity insulating nano-silica is used to form an inorganic / organic composite insulating system with epoxy resin, distributed between the iron-silicon-chromium and carbonyl iron powder particles, reducing contact between soft magnetic powder particles and lowering eddy current losses.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic composite materials, specifically relating to low-pressure molded SMC materials with high permeability and low loss, as well as their preparation and application. Background Technology

[0002] With the rapid development of the electronic information technology and communications industries, the market demand for electronic components and their performance requirements are constantly increasing. Electronic components are increasingly trending towards high frequency, integration, and miniaturization. As one of the three major passive electronic components, inductors were initially mainly structured with EI-shaped, U-shaped, and toroidal magnetic cores with thickly wound coils. New integrated inductors, with their miniaturization, low noise, and integration characteristics, have rapidly captured a significant share of the electronics market. As a core component of inductors, a soft magnetic material (SMC) material with high frequency, low power loss, stable permeability, and high saturation magnetic induction is needed.

[0003] In the selection of raw materials for integrated molded inductors, the powder material is required to have excellent DC superposition characteristics, high saturation magnetization, strong insulation and withstand voltage performance, and high temperature stability. Simultaneously, the product must possess good mechanical properties and corrosion resistance. Furthermore, production costs and ease of large-scale production must also be considered. Currently, most work on integrated inductor iron powder cores involves molding iron-silicon soft magnetic powders under high molding pressure (generally 500–1000 MPa) and heat treatment temperatures. The coil is prone to deformation under high pressure, and with further increases in operating frequency, eddy current losses within the iron core intensify, significantly limiting its application at high frequencies.

[0004] Carbonyl iron powder possesses excellent DC superposition characteristics, high saturation magnetization, high purity, fine particle size, and high sphericity. Nano-silica, as a high-resistivity ceramic material, exhibits high insulation resistivity at room temperature. Therefore, it is used to prepare a SiO2 coating layer on the surface of magnetic powder, which can both improve the resistivity of the magnetic powder core and effectively reduce the loss of magnetic properties. However, this process increases the difficulty and cost of coating, and the coating layer is also prone to peeling off under high molding pressure, thus reducing product stability.

[0005] To improve the above defects, this invention uses an epoxy resin binder system as the adhesive layer and insulating layer, and disperses nano-silica between iron-silicon-chromium and carbonyl iron powder using an epoxy resin binder as a carrier, thereby obtaining a high-density, high-permeability, and low-loss SMC inductor material under low molding pressure. Summary of the Invention

[0006] The first objective of this invention is to address the shortcomings of existing technologies by providing a method for preparing SMC materials with high magnetic permeability and low loss through low-pressure molding. This method utilizes an ultrasonic machine and a crusher to achieve uniform distribution of soft magnetic powder, nano-silica, and epoxy binder. While simplifying the process, it effectively improves the filling rate of magnetic powder, not only improving the bonding of soft magnetic powder but also reducing loss and increasing density and magnetic permeability.

[0007] The method of the present invention includes the following steps:

[0008] Step (1): Add nano-silica and carbonyl iron powder to anhydrous ethanol, mix evenly by ultrasonication, and dry to obtain a composite powder in which carbonyl iron powder and nano-silica are uniformly dispersed; the mass ratio of nano-silica to carbonyl iron powder is (0.002~0.015):1.

[0009] Preferably, the ultrasonic dispersion time is 0.5–2 h, and the drying temperature is 55–70 °C;

[0010] Step (2): Mix the composite powder obtained in step (1) with epoxy resin binder and pre-mix to obtain a composite system of carbonyl iron powder-nano silica uniformly dispersed with epoxy resin binder; the mass ratio of the composite powder to the epoxy resin binder is (4.65~5.78):1.

[0011] Preferably, the premixing temperature is 105–115℃ and the mixing time is 2–5 min.

[0012] Step (3): Add iron-silicon-chromium powder to the composite system obtained in step (2) and knead to obtain the low-pressure molded high-density, high-permeability, and low-loss SMC material.

[0013] Preferably, the mixing temperature is 115–125℃ and the mixing time is 1–3 min.

[0014] A second objective of this invention is to provide a low-pressure molded SMC material with high permeability and low loss prepared by the above method; the SMC material comprises the following components in parts by weight:

[0015]

[0016] The soft magnetic powder is 300 mesh iron-silicon-chromium, the carbonyl iron powder has a particle size of 2500 mesh, and the nano-silica has a median diameter of 50 nm.

[0017] The third objective of this invention is to provide the application of the aforementioned low-pressure molded, high-permeability, low-loss SMC material in the fabrication of electronic components.

[0018] A fourth objective of this invention is to provide an inductor comprising the aforementioned low-pressure molded SMC material with high permeability and low loss.

[0019] The beneficial effects of this invention are:

[0020] This invention uses anhydrous ethanol as a dispersion medium to ultrasonically disperse carbonyl iron powder and nano-silica powder to prepare SMC materials. This improves the compatibility of iron-silicon-chromium / carbonyl iron powder with epoxy resin, enhances the flexibility and impact resistance of the inductor material, and improves the magnetic properties of the SMC material. In this invention, the nano-silica is added through direct mixing and dispersion, without coating it on the surface of the magnetic powder, which greatly simplifies the manufacturing process and reduces costs. High-resistivity insulating nano-silica is used to form an inorganic / organic composite insulating system with epoxy resin, distributed between the iron-silicon-chromium and carbonyl iron powder particles, reducing contact between soft magnetic powder particles and lowering eddy current losses.

[0021] Due to its large specific surface area, nano-silica, when combined with epoxy resin, has a lubricating and dispersing effect on small carbonyl iron powder, improving its distribution. The small carbonyl iron powder and nano-silica are uniformly dispersed among the larger iron-silicon-chromium magnetic powders. Combined with low-pressure molding processes, this reduces the stress on the molded magnet, thereby lowering hysteresis loss and reducing overall loss.

[0022] Because the magnetic powder is more uniformly dispersed, high molding density and high magnetic permeability can be obtained under low molding pressure. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0024] Example 1

[0025] 0.16g of nano-silica and 73.6g of carbonyl iron powder were added to anhydrous ethanol and mixed in an ultrasonic machine for 0.5h. The mixture was then dried in a drying oven at 60℃ for 10h to obtain a composite powder in which carbonyl iron powder and nano-silica were uniformly dispersed. Then, 15.84g of epoxy resin binder was weighed, and the carbonyl iron powder, nano-silica composite powder, and epoxy resin binder were poured into a mixer for mixing at 105℃ for 5min. Then, 110.4g of iron-silicon-chromium powder was added and mixing continued for 3min at 115℃. Finally, the mixture was crushed in a crusher to obtain the low-pressure molded, high-density, high-permeability, low-loss SMC material.

[0026] The magnetic properties of the obtained SMC material were tested: the obtained SMC material was pressed into a magnetic ring (outer diameter 12.75mm × inner diameter 7.60mm × height 3.7mm) at 175℃ and 40MPa, and the density of the magnetic ring was obtained by Archimedes' displacement method; its inductance was tested by LCR meter and the effective permeability was calculated; the loss at different frequencies was tested by BH AC tester at 10mT and 20mT respectively.

[0027] Example 2

[0028] 0.48 g of nano-silica and 73.6 g of carbonyl iron powder were added to anhydrous ethanol and mixed in an ultrasonic machine for 2 hours. The mixture was then dried in a drying oven at 60°C for 10 hours to obtain a composite powder in which carbonyl iron powder and nano-silica were uniformly dispersed. Then, 15.52 g of epoxy resin binder was weighed, and the carbonyl iron powder, nano-silica composite powder, and epoxy resin binder were poured into a Banbury mixer for mixing at 115°C for 2 minutes. Then, 110.4 g of iron-silicon-chromium powder was added and mixing continued for 1 minute at 125°C. Finally, the mixture was crushed in a crusher to obtain the low-pressure molded, high-density, high-permeability, low-loss SMC material.

[0029] The obtained SMC was pressed into a magnetic ring according to the method in Example 1, and the density, permeability and magnetic loss of the magnetic ring were tested.

[0030] Example 3

[0031] 1.12g of nano-silica and 73.6g of carbonyl iron powder were added to anhydrous ethanol and mixed in an ultrasonic machine for 2 hours. The mixture was then dried in a drying oven at 60℃ for 10 hours to obtain a composite powder in which carbonyl iron powder and nano-silica were uniformly dispersed. Then, 14.88g of epoxy resin binder was weighed, and the carbonyl iron powder, nano-silica composite powder, and epoxy resin binder were poured into a Banbury mixer for mixing at 115℃ for 2 minutes. Then, 110.4g of iron-silicon-chromium powder was added and mixing continued for 1 minute at 125℃. Finally, the mixture was crushed in a crusher to obtain the low-pressure molded, high-density, high-permeability, low-loss SMC material.

[0032] The obtained SMC was pressed into a magnetic ring according to the method in Example 1, and the density, permeability and magnetic loss of the magnetic ring were tested.

[0033] Example 4

[0034] 0.98g of nano-silica and 74.4g of carbonyl iron powder were added to anhydrous ethanol and mixed in an ultrasonic machine for 0.5h. The mixture was then dried in a drying oven at 60℃ for 10h to obtain a composite powder in which carbonyl iron powder and nano-silica were uniformly dispersed. Then, 13.02g of epoxy resin binder was weighed, and the carbonyl iron powder, nano-silica composite powder, and epoxy resin binder were poured into a Banbury mixer for mixing at 105℃ for 2min. Then, 111.6g of iron-silicon-chromium powder was added and mixing continued for 1min at 115℃. Finally, the mixture was crushed in a crusher to obtain the low-pressure molded, high-density, high-permeability, low-loss SMC material.

[0035] The obtained SMC was pressed into a magnetic ring according to the method in Example 1, and the density, permeability and magnetic loss of the magnetic ring were tested.

[0036] Comparative Example 1

[0037] 15.84 g of epoxy resin binder and 73.6 g of carbonyl iron powder were weighed and mixed together in an internal mixer at 105°C for 5 minutes. Then, 110.4 g of iron-silicon-chromium powder was added and the mixture was mixed for another 3 minutes at 115°C. Finally, the mixture was crushed in a crusher to obtain a soft magnetic composite material of iron-silicon-chromium and carbonyl iron powder for magnetic property testing. The prepared soft magnetic composite material of iron-silicon-chromium and carbonyl iron powder was pressed into a magnetic ring (outer diameter 12.75 mm × inner diameter 7.60 mm × height 3.7 mm) at 175°C and 40 MPa. The density, permeability and magnetic loss of the magnetic ring were tested according to the method in Example 1.

[0038] The results obtained from the above embodiments and comparative examples are shown in Table 1.

[0039] Table 1 shows the magnetic ring performance obtained from each embodiment and comparative example.

[0040]

[0041] As can be seen from the above embodiments, when nano-silicon oxide is added, under the process adopted in this application, using conventional iron-silicon-chromium and carbonyl iron powder composite magnetic powder, the effective permeability of the obtained magnetic ring exceeds 27 at a relatively low molding pressure, and the magnetic loss is as low as 400 KW / m at a relatively high frequency of 2000 kHz. 3 (10mT) and 2500KW / m 3 (20mT) around.

Claims

1. A method for preparing a low-pressure molded SMC material with high permeability and low loss, characterized in that, The preparation method includes the following steps: Step (1): Add nano-silica and carbonyl iron powder to anhydrous ethanol, mix evenly by ultrasonication, and dry to obtain a composite powder in which carbonyl iron powder and nano-silica are uniformly dispersed; the mass ratio of nano-silica to carbonyl iron powder is (0.002~0.015):

1. Step (2): The composite powder obtained in step (1) is mixed with epoxy resin binder and pre-mixed to obtain a composite system of carbonyl iron powder-nano silica uniformly dispersed with epoxy resin binder; the mass ratio of the composite powder to the epoxy resin binder is (4.65~5.78):

1. Step (3): Add iron-silicon-chromium powder to the composite system obtained in step (2) and knead to obtain the low-pressure molded high-density, high-permeability, and low-loss SMC material; wherein, the nano-silica is directly kneaded and dispersed between the iron-silicon-chromium powder and carbonyl iron powder particles through an epoxy resin binder carrier, forming an inorganic / organic composite insulation system with the epoxy resin. The SMC material was pressed into shape at 175°C and 40MPa pressure.

2. The preparation method according to claim 1, characterized in that, The ultrasound time in step (1) is 0.5 to 2 hours.

3. The preparation method according to claim 1, characterized in that, The drying temperature in step (1) is 55-70℃.

4. The preparation method according to claim 1, characterized in that, The premixing temperature in step (2) is 105-115℃.

5. The preparation method according to claim 1, characterized in that, The premixing time in step (2) is 2 to 5 minutes.

6. The preparation method according to claim 1, characterized in that, The mixing temperature in step (3) is 115-125℃.

7. The preparation method according to claim 1, characterized in that, The mixing time in step (3) is 1 to 3 minutes.

8. A low-pressure molded SMC material with high magnetic permeability and low loss, characterized in that, The SMC material is prepared by the method described in any one of claims 1-7; the components in the SMC material comprise the following parts by weight: 55.2–55.8 parts of iron-silicon-chromium powder Carbonyl iron powder 36.8–37.2 parts 6.44–7.93 parts epoxy resin adhesive 0.07 to 0.56 parts of nano-silica.

9. The application of the low-pressure molded, high-permeability, low-loss SMC material of claim 8 in the fabrication of electronic components.

10. An inductor, characterized in that, Including the low-pressure molded, high-permeability, low-loss SMC material as described in claim 8.

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