A method for preparing an inductor

Abstract

The present invention relates to the technical field of inductors, and it relates to a preparation method of an inductor. The I-Core and O-Core are respectively prepared by a composite material. In the preparation process, a cold press is used for cold pressing and forming, and the pressure during cold pressing is 1.5 - 2 Ton; after the copper wire is wound into a coil by a winding machine, the two ends of the coil are bent into pins. The U-Core is prepared by a composite material. In the preparation process, a cold press is used for cold pressing and forming, and the pressure during cold pressing is 5.5 - 6 Ton. The coil, I-Core, and O-Core are sequentially placed into the U-Core to form a blank, and finally the blank is sent to a hot press for hot pressing and forming.

Description

Technical Field

[0001] The present invention relates to the technical field of inductors, and more specifically, it relates to a method for manufacturing an inductor. Background Art

[0002] As one of the three passive electronic basic components in the circuit board of electronic products, inductors are widely used in fields such as communication, industrial equipment, automobiles, new energy, and the Internet of Things. With the rapid change of the market and the large-scale construction of related industries such as the Internet of Things and smart cities, the market scale of inductors has developed rapidly. To meet the above application requirements, the development trend of inductors presents characteristics such as miniaturization, high performance, and high power. However, there are some technical problems in the manufacturing process of existing integrated inductors.

[0003] For example, Patent Document CN116313347B describes a method for manufacturing an inductor using a composite material of carbonyl iron powder and amorphous powder. However, in this method, the cold-pressed T-Core has insufficient strength, resulting in product breakage during winding. To solve this problem, baking is required after cold pressing in the process, but this leads to a reduction in the hot pressing compression amount and the characteristics of the inductor cannot be fully exerted. During the winding process, limited by the strength of the T-Core, the tension and hot air cannot be adjusted too much, resulting in poor bonding of the coil self-adhesive layer and there is a quality risk. During the hot pressing forming process, since large-tonnage equipment is required, the copper wire after winding is easily deformed, further affecting the product quality. During the hot pressing powder filling process, the powder filling on the side wall is uneven, resulting in large fluctuations in the inductor value and unable to ensure the consistency of the product.

[0004] Another patent document CN117153548A describes a method for manufacturing an integrated inductor product, which uses precision mechanical equipment for coil manufacturing and lead wire cutting, and the precise implantation and forming of T-CORE and U-CORE. Although the production efficiency and consistency are improved, there are still some deficiencies. During the cold pressing forming process, the problems of insufficient strength of T-Core and U-Core and uneven powder filling still exist. In addition, the complex mechanical equipment and multi-step processes in this method increase the production cost and process difficulty.

[0005] Therefore, there is a need for a new set of inductor manufacturing processes to avoid the many deficiencies of the existing technology. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for manufacturing an inductor, which enables the I-Core and O-Core not to require baking treatment after cold pressing, avoids the problem of reduction in the hot pressing compression amount caused by baking, and improves the strength and stability of the inductor.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing an inductor, comprising the following steps:

[0009] S1. Prepare I-Core and O-Core respectively through a composite material. In this preparation process, cold pressing is used by a cold press, and the pressure during cold pressing is 1.5 - 2 Ton;

[0010] S2. Manufacture the coil. After winding the copper wire into a coil by a winding machine, bend the two ends of the coil into pins;

[0011] S3. Prepare U-Core through a composite material. In this preparation process, cold pressing is used by a cold press, and the pressure during cold pressing is 5.5 - 6 Ton;

[0012] S4. Assembly. Put the coil, I-Core and O-Core into U-Core in sequence to form a blank, and finally send the blank to a hot press for hot pressing and forming.

[0013] The present invention is further set as: The composite material comprises the following components:

[0014] 40% - 60% of iron-silicon-boron series amorphous powder

[0015] 40% - 60% of carbonyl iron powder

[0016] 2% - 4% of epoxy resin adhesive

[0017] 0.1% - 0.3% of coupling agent.

[0018] The present invention is further set as: The specific steps for preparing I-Core and O-Core with the composite material are as follows:

[0019] S11. Weigh the required components according to the following ratio: 45% of iron-silicon-boron series amorphous powder, 45% of carbonyl iron powder, 2.5% of epoxy resin adhesive, 0.2% of coupling agent. Mix the iron-silicon-boron series amorphous powder and carbonyl iron powder evenly according to the ratio, then add the epoxy resin adhesive and coupling agent to the mixed powder, and mix in a mixer at low speed for 30 minutes;

[0020] S12. Granulate the mixture through an extrusion granulator, control the granulation temperature at 60 - 80 °C, and control the particle size between 100 - 200 microns;

[0021] S13. Dry the granulated particles at 80 - 100 °C for 2 - 4 hours to remove excess moisture and solvents, and ensure the fluidity and uniformity of the particles;

[0022] S14. Fill the particles into a cold pressing mold, set the pressure of the cold press to 1.5 - 2 Ton, start the cold press for pressing, the cold pressing time is 5 - 15 seconds, demold after the I-Core and O-Core are compacted and formed in the mold, and collect the I-Core and O-Core.

[0023] The present invention is further configured as follows: The specific steps for preparing the U-Core from the composite material are as follows:

[0024] S31. Weigh the required components in the following proportions: 50% of iron-silicon-boron series amorphous powder, 50% of carbonyl iron powder, 3% of epoxy resin adhesive, and 0.25% of coupling agent. Mix the iron-silicon-boron series amorphous powder and carbonyl iron powder evenly according to the proportion, then add the epoxy resin adhesive and coupling agent to the mixed powder, and mix in a mixer at low speed for 45 minutes;

[0025] S32. Granulate the mixture through an extrusion granulator, control the granulation temperature at 60 - 80 °C, and control the particle size between 100 - 150 microns;

[0026] S33. Dry the granulated particles at 80 - 90 °C for 3 - 4 hours to remove excess moisture and solvents, ensuring the fluidity and uniformity of the particles;

[0027] S34. Fill the particles into a cold pressing mold, set the pressure of the cold press to 5.5 - 6 Ton, start the cold press for pressing, the cold pressing time is 20 - 35 seconds, ensure that the particles are evenly distributed and compacted into a U-Core, and the U-Core formed in the cold pressing mold does not need to be demolded and waits for assembly.

[0028] The present invention is further configured as follows: The specific steps for the assembly are as follows:

[0029] S41. Place the pre-wound coil into the cold-pressed U-Core, ensuring that the coil is in the correct position and the pins of the coil are outside the slots of the U-Core;

[0030] S42. Place the I-Core into the U-Core along the center of the coil, making it in close contact with the coil, ensuring that the I-Core is centered and aligned with the coil;

[0031] S43. Cover the O-Core on the U-Core to form a complete blank, ensuring that all components of the O-Core, U-Core, and I-Core fit tightly together, avoiding any looseness or misalignment;

[0032] S44. Send the assembled blank to a hot press for hot pressing to form an inductor.

[0033] The present invention is further configured as follows: The steps for the hot pressing are as follows:

[0034] S441. When the blank is placed in the hot press, set the preheating temperature to 60 - 100 °C and the time to 40 - 60 seconds to eliminate internal stress and improve the plasticity of the material.

[0035] S442. When starting hot pressing, the hot pressing temperature is 180 - 200 °C, the pressure is 11 - 13 Ton, and the hot pressing time is 80 - 100 seconds.

[0036] The present invention is further configured as follows: in step S14, the cold pressing pressure of the cold press is controlled at 2 Ton and the cold pressing time is 10 seconds.

[0037] In step S34, the cold pressing pressure of the cold press is controlled at 6 Ton and the cold pressing time is 30 seconds.

[0038] In step S442, the hot pressing pressure of the hot press is controlled at 13 Ton and the hot pressing time is 90 seconds.

[0039] The present invention is further configured as follows: for the iron-silicon-boron series amorphous powder, its elemental composition is as follows:

[0040] Si 2.86 - 3.86%

[0041] B 2.78 - 3.38%

[0042] C 0.25 - 0.75%

[0043] O < 5000 PPM

[0044] The balance is Fe.

[0045] The present invention is further configured as follows: the sizes and shapes of the I-Core and O-Core are set according to the inductance value requirements of the inductor.

[0046] The present invention is further configured as follows: the formed inductor needs to be baked, then roll-sprayed with insulating paint and the subsequent paint stripping is carried out, after which electroplating is performed, and finally the inductor is tested. The qualified inductors are packaged.

[0047] Comparing with the deficiencies of the prior art, the beneficial effects of the present invention are as follows:

[0048] By optimizing the material ratio and cold pressing process, the present invention enables the I-Core and O-Core not to require baking treatment after cold pressing, thus avoiding the problem of reduced hot pressing compression due to baking, improving the strength and stability of the inductor, and also improving the preparation efficiency by eliminating the cold pressing and baking process.

[0049] During hot pressing, instead of filling powder, the I-Core and O-Core are extruded and formed inside the U-Core, making the inductance value uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the assembly process of the present invention. Detailed implementation manners

[0051] Refer to Figure 1 to further illustrate the embodiments of the present invention.

[0052] In the following content, the preparation of I-Core or O-Core or U-Core can be carried out synchronously with the coil production to improve production efficiency.

[0053] Coil production: Use a winding machine to wind copper wire into a coil, and bend both ends of the coil into pins.

[0054] Among them: The sizes and shapes of I-Core and O-Core are set to be square, cross-shaped, elliptical or circular according to the inductor inductance value requirements. There is a groove with a depth on the end face of U-Core, and this groove is used to accommodate the coil, I-Core and O-Core. Embodiment 1:

[0055] Preparation of I-Core and O-Core:

[0056] Select the raw material ratio: 45% of iron-silicon-boron series amorphous powder, 45% of carbonyl iron powder, 2.5% of epoxy resin adhesive, 0.2% of coupling agent. Among them, the components of the iron-silicon-boron series amorphous powder are: Si: 3.5%, B: 3.0%, C: 0.5%, O: <5000 PPM, and the rest is Fe.

[0057] Weigh the raw materials according to the ratio. Now mix the iron-silicon-boron series amorphous and carbonyl iron powder evenly in a mixer, and then put the epoxy resin adhesive and coupling agent into the mixer, and mix at low speed for 30 minutes. Granulate the mixed mixture through an extrusion granulator at 70°C, with the particle size of 150 microns. Dry the granulated particles at 90°C for 3 hours. Finally, cold press the particles in a cold press mold at a pressure of 2 Ton for 10 seconds to obtain I-Core and O-Core and demold them.

[0058] Preparation of U-Core:

[0059] Select the raw material ratio: 50% of iron-silicon-boron series amorphous powder, 50% of carbonyl iron powder, 3% of epoxy resin adhesive, 0.25% of coupling agent. Among them, the components of the iron-silicon-boron series amorphous powder are: Si: 3.0%, B: 3.3%, C: 0.4%, O: <5000 PPM, and the rest is Fe.

[0060] The raw materials are weighed according to the ratio. The iron silicon boron series amorphous and carbonyl iron powders are first mixed evenly in a mixer, and then the epoxy resin adhesive and coupling agent are added into the mixer. The mixture is mixed at a low speed for 45 minutes to obtain a mixture. The mixture is then put into a granulator and granulated by an extrusion granulator at 75°C. The particle size is 120 microns. After the granulated particles are dried at 85°C for 4 hours, the powder is sent to a cold pressing mold and cold pressed at a pressure of 6 Ton for 30 seconds to obtain U-Core without demolding.

[0061] Assembly and thermoforming:

[0062] Place the I-Core into the U-Core along the center of the coil to make it in close contact with the coil, ensure that the I-Core is centered and aligned with the coil, then cover the O-Core on the U-Core and contact the end face of the I-Core to form a complete blank, ensure that the various components of the O-Core, U-Core and I-Core fit closely to avoid any looseness or misalignment; send the assembled blank to the hot press for hot pressing and preheating before hot pressing. The preheating temperature is 80°C and the time is 50 seconds. The working conditions during hot pressing are as follows: the hot pressing temperature is 190°C, the pressure is 13 Ton, and the hot pressing time is 90 seconds. Finally, the formed inductor is obtained, and then the inductor is sent to the inductor for baking. After baking, the insulating paint is sprayed and the subsequent paint stripping is carried out, followed by electroplating. Finally, the inductor is tested, and the qualified inductors are packaged. Embodiment 2:

[0063] Preparation of I-Core and O-Core:

[0064] The raw material ratio is selected as follows: 50% amorphous powder of FeSiB series, 50% carbonyl iron powder, 3% epoxy resin adhesive, and 0.25% coupling agent, wherein the components of amorphous powder of FeSiB series are: Si: 3.86%, B: 2.78%, C: 0.75%, O: <5000 PPM, and the rest is Fe. The raw materials are weighed according to the ratio, and the amorphous powder of FeSiB series and carbonyl iron powder are mixed evenly in a mixer, and then epoxy resin adhesive and coupling agent are added, and the mixture is mixed at a low speed for 30 minutes to obtain a mixture, and the mixed mixture is granulated in a granulator at 70°C, and the particle size is 150 microns. The granulated particles are dried at 90°C for 3 hours, and finally the powder is sent to a cold pressing mold to be cold pressed at a pressure of 1.5Ton, and the cold pressing time is 15 seconds to obtain I-Core and O-Core and demold.

[0065] Preparation of U-Core:

[0066] Select raw material ratio: 45% iron-silicon-boron series amorphous powder, 45% carbonyl iron powder, 2.5% epoxy resin adhesive, 0.2% coupling agent. The composition of the iron-silicon-boron series amorphous powder: Si: 2.86%, B: 3.38%, C: 0.25%, O: <5000 PPM, and the rest is Fe. Weigh the raw materials according to the ratio. After mixing the iron-silicon-boron series amorphous and carbonyl iron powders evenly in a mixer, add the epoxy resin adhesive and coupling agent, and mix at low speed for 45 minutes. Granulate the mixture through an extrusion granulator at 75°C, with the particle size of 120 microns. The granulated particles are dried at 85°C for 4 hours. Finally, the particles are cold-pressed into shape in a cold pressing mold under a pressure of 5.5 Ton, and the cold pressing time is 20 seconds to obtain the U-Core without demolding.

[0067] Assembly and hot pressing: Place the coil inside the U-Core, and put the I-Core into the U-Core along the center of the coil so that it is in close contact with the coil, ensuring that the I-Core is centered and aligned with the coil; Cover the O-Core on the U-Core to form a complete blank, ensuring that all components of the O-Core, U-Core, and I-Core fit tightly together to avoid any looseness or misalignment.

[0068] Send the assembled blank to a hot press for hot pressing. Preheat it before hot pressing, with the preheating temperature of 70°C and the time of 40 seconds; The working conditions during hot pressing are that the hot pressing temperature is 185°C, the pressure is 12 Ton, and the hot pressing time is 85 seconds. Finally, the formed inductor is obtained, and then the inductor is sent for baking. After baking, roll spray insulating paint and subsequent paint stripping are carried out, and then electroplating is carried out. Finally, the inductor is tested, and the qualified inductors are packaged. Example 3:

[0069] Preparation of I-Core and O-Core:

[0070] Select raw material ratio: 40% iron-silicon-boron series amorphous powder, 60% carbonyl iron powder, 4% epoxy resin adhesive, 0.3% coupling agent. The composition of the iron-silicon-boron series amorphous powder: Si: 3.5%, B: 3.0%, C: 0.5%, O: <5000 PPM, and the rest is Fe. Weigh the raw materials according to the ratio. After mixing the iron-silicon-boron series amorphous and carbonyl iron powders evenly in a mixer, add the epoxy resin adhesive and coupling agent, and mix at low speed for 30 minutes to obtain a mixture. Granulate the mixed mixture in a granulator at 70°C, with the particle size of 150 microns. The granulated particles are dried at 90°C for 3 hours. Finally, send the powder to a cold pressing mold to be cold-pressed into shape under a pressure of 2 Ton, and the cold pressing time is 10 seconds to obtain the I-Core and O-Core and demold them.

[0071] Preparation of U-Core:

[0072] Select raw material ratios: 55% iron-silicon-boron series amorphous powder, 45% carbonyl iron powder, 2% epoxy resin adhesive, 0.1% coupling agent. The composition of the iron-silicon-boron series amorphous powder is as follows: Si: 3.0%, B: 2.78%, C: 0.25%, O: <5000 PPM, and the rest is Fe. Weigh the raw materials according to the ratios. After mixing the iron-silicon-boron series amorphous and carbonyl iron powders evenly in a mixer, add the epoxy resin adhesive and coupling agent, and mix at low speed for 45 minutes. Granulate the mixture through an extrusion granulator at 75°C, with the particle size being 120 microns. The granulated particles are dried at 85°C for 4 hours. Finally, the powder is sent to a cold pressing mold and cold pressed into shape under a pressure of 6 Ton for 35 seconds to obtain a U-Core without demolding.

[0073] Assembly and hot pressing: Place the coil inside the U-Core, and insert the I-Core along the center of the coil into the U-Core to make it in close contact with the coil, ensuring that the I-Core is centered and aligned with the coil; cover the O-Core on the U-Core to form a complete blank, ensuring that all components of the O-Core, U-Core, and I-Core fit tightly together to avoid any looseness or misalignment.

[0074] Send the assembled blank to a hot press for hot pressing. Preheat it before hot pressing, with the preheating temperature being 80°C and the time being 45 seconds; during hot pressing, the working conditions are as follows: the hot pressing temperature is 190°C, the pressure is 13 Ton, and the hot pressing time is 95 seconds. Finally, the formed inductor is obtained, and then the inductor is sent for baking. After baking, roll spray insulating paint and perform subsequent paint stripping, and then perform electroplating. Finally, test the inductor, and package the qualified inductors.

[0075] Comparative Example 1:

[0076] On the basis of the steps in Example 1, an additional baking step for the I-Core and 0-Core is added, with the baking temperature being 120°C and the baking time being 1 hour.

[0077] Comparative Example 2:

[0078] On the basis of the steps in Example 1, an additional baking step for the I-Core and 0-Core is added, with the baking temperature being 130°C and the baking time being 1.5 hours.

[0079] Comparative Example 3:

[0080] On the basis of the steps in Example 1, an additional baking step for the I-Core and 0-Core is added, with the baking temperature being 140°C and the baking time being 2 hours.

[0081] Carry out relevant performance tests on the inductors of Examples 1-3 and Comparative Examples 1-3 for reference.

[0082] The method for detecting the performance of an inductor is as follows:

[0083] Inductance value: Connect the inductor to the test port of an LCR meter, set the test frequency (usually 100 kHz), record the displayed inductance value, and repeat the test 3 times and take the average. The measurement accuracy requirement for the inductance value is ±0.1 μH.

[0084] Resistance: Connect the inductor to the test port of a micro-ohmmeter, set the test current (usually 1 A), record the displayed resistance value, and repeat the test 3 times and take the average. The measurement accuracy requirement for the resistance is ±0.1 mΩ.

[0085] Q value: Connect the inductor to the test port of a Q-value tester, set the test frequency (usually 100 kHz), record the displayed Q value, and repeat the test 3 times and take the average. The higher the Q value, the better the performance of the inductor.

[0086] Current-carrying capacity: Connect the inductor in series between a DC power supply and an ammeter, gradually increase the current until the inductor reaches the limit temperature rise, and record the current value at this time. The current-carrying capacity indicates the maximum current that the inductor can withstand without exceeding the specified temperature rise.

[0087] Dimensional stability: Use a microscope to measure the initial dimensions of the inductor after production, place the inductor under specified environmental conditions (such as high temperature, high humidity, etc.) for an aging test (for example, 1000 hours), and measure the dimensional change of the inductor again. The dimensional stability indicates the dimensional change of the inductor during use, and the smaller the change, the better.

[0088] Mechanical strength:

[0089] Place the inductor on the test platform of a material testing machine, gradually increase the pressure until the inductor undergoes structural damage, and record the pressure value at this time. The mechanical strength indicates the anti-mechanical shock ability of the inductor, and the larger the value, the better.

[0090] In summary: In Examples 1-3 without the baking process flow, the inductor is significantly superior to Comparative Examples 1-3 in terms of inductance value stability, resistance, Q value, current-carrying capacity, dimensional stability, mechanical strength, and surface insulation resistance, etc.

[0091] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an inductor, characterized in that: It includes the following steps: S1. Prepare I-Core and O-Core respectively with composite materials. In this preparation process, cold pressing is used by a cold press, and the pressure during cold pressing is 1.5 - 2 Ton; S2. Make the coil. After winding the copper wire into a coil by a winding machine, bend the two ends of the coil into pins; S3. Prepare U-Core with composite materials. In this preparation process, cold pressing is used by a cold press, and the pressure during cold pressing is 5.5 - 6 Ton; S4. Assembly. Put the coil, I-Core and O-Core into U-Core in sequence to form a blank, and finally send the blank to a hot press for hot pressing; The specific steps for preparing I-Core and O-Core with composite materials are as follows: S11. Weigh the required components in the following proportions: 45% of iron-silicon-boron series amorphous powder, 45% of carbonyl iron powder, 2.5% of epoxy resin adhesive, 0.2% of coupling agent. Mix the iron-silicon-boron series amorphous powder and carbonyl iron powder evenly according to the proportion, then add the epoxy resin adhesive and coupling agent to the mixed powder, and mix in a mixer at low speed for 30 minutes; S12. Granulate the mixture through an extrusion granulator, control the granulation temperature at 60 - 80 °C, and control the particle size between 100 - 200 microns; S13. Dry the granulated particles at 80 - 100 °C for 2 - 4 hours to remove excess moisture and solvents, and ensure the fluidity and uniformity of the particles; S14. Fill the particles into a cold pressing mold, set the pressure of the cold press at 1.5 - 2 Ton, start the cold press for pressing, the cold pressing time is 5 - 15 seconds, demold after compacting and forming I-Core and O-Core in the mold, and collect I-Core and O-Core; The specific steps for preparing U-Core with composite materials are as follows: S31. Weigh the required components in the following proportions: 50% of iron-silicon-boron series amorphous powder, 50% of carbonyl iron powder, 3% of epoxy resin adhesive, 0.25% of coupling agent. Mix the iron-silicon-boron series amorphous powder and carbonyl iron powder evenly according to the proportion, then add the epoxy resin adhesive and coupling agent to the mixed powder, and mix in a mixer at low speed for 45 minutes; S32. Granulate the mixture through an extrusion granulator, control the granulation temperature at 60 - 80 °C, and control the particle size between 100 - 150 microns; S33. Dry the granulated particles at 80 - 90 °C for 3 - 4 hours to remove excess moisture and solvents, and ensure the fluidity and uniformity of the particles; S34. Fill the particles into a cold pressing mold, set the pressure of the cold press at 5.5 - 6 Ton, start the cold press for pressing, the cold pressing time is 20 - 35 seconds, ensure that the particles are evenly distributed and compacted into U-Core, and the U-Core formed in the cold pressing mold does not need to be demolded and waits for assembly; The specific steps for assembly are as follows: S41. Place the pre-wound coil into the cold-pressed U-Core, ensure that the position of the coil is accurate and the pins of the coil are outside the slots of the U-Core; S42. Place the I-Core along the center of the coil into the U-Core, making it in close contact with the coil, ensuring that the I-Core is centered and aligned with the coil; S43. Cover the U-Core with the O-Core to form a complete blank, ensuring that all components of the O-Core, U-Core, and I-Core fit tightly together to avoid any looseness or misalignment; S44. Send the assembled blank to a hot press for hot pressing into an inductor. The steps of the hot pressing are as follows: S441. When the blank is placed in the hot press, set the preheating temperature to 60 - 100 °C and the time to 40 - 60 seconds to eliminate internal stress and improve the plasticity of the material; S442. When starting the hot pressing, the hot pressing temperature is 180 - 200 °C, the pressure is 11 - 13 Ton, and the hot pressing time is 80 - 100 seconds.

2. The manufacturing method of an inductor according to claim 1, characterized in that: The In step S14, the cold pressing pressure of the cold press is controlled at 2 Ton and the cold pressing time is 10 seconds; In step S34, the cold pressing pressure of the cold press is controlled at 6 Ton and the cold pressing time is 30 seconds; In step S442, the hot pressing pressure of the hot press is controlled at 13 Ton and the hot pressing time is 90 seconds.

3. The method for preparing an inductor according to claim 1, wherein: For the iron-silicon-boron series amorphous powder, its elemental composition is as follows: Si 2.86~3.86% B 2 .78~3 .38% C 0 .25~0 .75% O < 5000 PPM The rest is Fe.

4. The preparation method of an inductor according to claim 2, wherein: The sizes and shapes of the I-Core and O-Core are set according to the inductance value requirements of the inductor.

5. The manufacturing method of an inductor according to claim 3, characterized in that: The formed inductor needs to be baked, then roll-sprayed with insulating paint and the subsequent paint stripping is carried out, followed by electroplating, and finally the inductor is tested. The qualified inductors after testing are packaged.

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