Method for manufacturing a molded magnetic device and molded magnetic device

Abstract

The present disclosure provides a preparation method of a molded magnetic device and the molded magnetic device. The preparation method of the molded magnetic device comprises the following steps: mixing a binder and a magnetic material powder to prepare a magnetic composite material; and placing the magnetic composite material in a mold for compression molding to prepare a magnetic device, wherein the temperature of the mold is controlled to be 60-120 DEG C during the compression molding, so that the binder in the part of the magnetic composite material contacting the surface of the mold is solidified. It is found through experiments that, compared with the cold pressing process in the prior art, the strength of the molded magnetic device prepared by the above embodiment is obviously improved, and the proportion of sample cracking in large-scale sample preparation is obviously reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inductance, and in particular to a preparation method of a molded magnetic device and the molded magnetic device. BACKGROUND

[0002] The integrally formed inductance is mainly composed of a magnetic material, a binder and a metal coil. In the preparation process, the binder and the magnetic material powder are usually mixed to prepare a magnetic composite material, the metal coil winding is embedded in the magnetic composite material powder, and then the powder metallurgy is used for compression molding, and then the binder is solidified by heating to bond the magnetic material powder. In addition to being able to bond the magnetic material powder, the binder also has the functions of blocking the transmission of eddy current between the powders and reducing the loss. The integrally formed inductance is widely welcomed in the electronic industry due to its excellent magnetic shielding structure, excellent magnetic properties, small size and other advantages.

[0003] At present, the integrally formed inductance is usually prepared by cold pressing or hot pressing. The hot pressing method usually needs to go through the processes of preheating and pressure maintaining, which is time-consuming. The cold pressing directly uses a servo press to compress and form the magnetic composite material at room temperature, and then the servo press demolds to eject the formed magnetic device from the mold cavity. Compared with hot pressing, cold pressing has the advantage of high compression molding efficiency. However, in the cold pressing process, when the magnetic device is ejected from the mold cavity, there is always a part of the magnetic device that is cracked. According to further research, the cracking condition is related to the size of the coil and the coil column of the inductance. The thicker the coil and the larger the size of the coil column, the higher the risk of cracking of the inductance.

[0004] In order to reduce the cracking of the sample in the cold pressing process, the common practice in the industry is to reduce the number of coils or to reduce the size of the coil column, but this often also sacrifices the performance of the inductance. In addition, there is also a way to add more lubricant to the magnetic material powder or to improve the smoothness of the surface of the mold cavity. However, these improvement methods either sacrifice the performance of the inductance or bring additional material consumption or mold cost. Although it can reduce the cracking of the inductance sample to some extent, it usually cannot effectively reduce the manufacturing cost. SUMMARY

[0005] Therefore, in order to improve the cracking problem of the molded magnetic device in the molding process without significantly increasing the manufacturing cost, it is necessary to provide a preparation method of a molded magnetic device, and correspondingly, to provide a molded magnetic device.

[0006] One embodiment of the present disclosure provides a preparation method of a molded magnetic device, which comprises the following steps:

[0007] mixing the binder and the magnetic material powder to prepare a magnetic composite material;

[0008] The magnetic composite material is placed in a mold for compression molding to prepare a magnetic device, and the temperature of the mold is controlled to be 60-120°C during the compression molding, so that the binder in the part of the magnetic composite material contacting the surface of the mold is solidified.

[0009] In one embodiment, the temperature of the mold is controlled to be 100-120°C during the compression molding.

[0010] In one embodiment, the time for which the mold compresses the magnetic composite material is controlled to be within 5 seconds during the compression molding.

[0011] In one embodiment, the binder comprises one or more of an epoxy resin binder, a phenolic resin binder, a cyanate ester binder, and a silicone resin binder.

[0012] In one embodiment, the magnetic material powder comprises one or more of carbonyl iron powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, and iron-silicon powder.

[0013] In one embodiment, the mass of the binder in the magnetic composite material is 6-10% of the mass of the magnetic material powder.

[0014] In one embodiment, the process of mixing the binder and the magnetic material powder comprises mixing the binder and the magnetic material powder dispersed in a dispersant, and the mass of the dispersant is 10-15% of the mass of the magnetic material powder.

[0015] In one embodiment, after the binder and the magnetic material powder are mixed, the process further comprises a step of drying the formed mixture, and in the step of drying the formed mixture, the temperature of drying is controlled to be below 50°C, and the time of drying is controlled to be below 60 minutes.

[0016] In one embodiment, the molded magnetic device is an integrally molded inductor, and during the compression molding, the coil and the magnetic composite material are placed in the mold together, and the applied pressure is controlled to be 0.5-3T.

[0017] Yet another embodiment of the present disclosure further provides a molded magnetic device prepared according to the preparation method of the molded magnetic device of any of the above embodiments.

[0018] In the method for manufacturing the molded magnetic device provided in the above embodiments, the binder and the magnetic material powder are first mixed to prepare a magnetic composite material, and in the process of pressing the magnetic composite material, the temperature of the mold is controlled to be 60-120°C, so that the binder in the part of the magnetic composite material contacting the surface of the mold is solidified. Since the mold is properly heated in the process of pressing the magnetic composite material, the binder in the part contacting the surface of the mold is solidified and cross-linked, the bonding strength between the powders is improved, the stress on the prepared magnetic device when demolding is resisted, and the problem of cracking of the molded magnetic device in appearance when the sample is prepared is improved. It is found through experiments that, compared with the cold pressing process in the prior art, the strength of the molded magnetic device prepared according to the above embodiments is obviously improved, and the proportion of cracking of the sample when the sample is prepared on a large scale is obviously reduced.

[0019] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application clearer and can be implemented according to the content of the description, the preferred embodiments of the present application are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The photo of the magnetic ring pressed for Comparative Example 2. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present application, the present application will be described more fully below. The preferred embodiments of the present application are given below. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0024] One embodiment of the present disclosure provides a method for preparing a molded magnetic device, comprising the steps of:

[0025] mixing the binder and the magnetic material powder to prepare a magnetic composite material;

[0026] molding the magnetic composite material in a mold to prepare the magnetic device, and controlling the temperature of the mold to be 60-120°C during the molding process to solidify the binder in the part of the magnetic composite material that contacts the surface of the mold.

[0027] It can be understood that the binder in the molded magnetic device is a thermosetting binder material, i.e., a material that can undergo cross-linking reaction and solidification between molecules after being heated. In the cold-pressing method of the conventional technology, the magnetic material powder and the binder are usually mixed and placed in a mold first, and then the binder is solidified after the molding to enhance the strength of the finally prepared device.

[0028] It can be understood that in this embodiment, by controlling the temperature of the mold to be 60-120°C during the molding process, only the part of the binder that contacts the inner surface of the mold is heated. Therefore, only a small amount of binder on the surface of the sample is cross-linked and solidified, which mainly improves the strength of the sample on the surface to improve the problem of cracking of the sample. The binder inside the sample is basically not affected, and the internal mechanical strength of the sample is not significantly enhanced, so the other steps of the conventional cold-pressing method still apply without the need for changes.

[0029] In the method for preparing a molded magnetic device provided in the above embodiment, the binder and the magnetic material powder are first mixed to prepare a magnetic composite material, and the temperature of the mold is controlled to be 60-120°C during the molding of the magnetic composite material to solidify the binder in the part of the magnetic composite material that contacts the surface of the mold. Since the mold is appropriately heated during the molding of the magnetic composite material, the part of the binder that contacts the surface of the mold undergoes solidification and cross-linking reaction, which can improve the bonding strength between the powders, resist the stress of the prepared magnetic device during demolding, and improve the problem of cracking of the molded magnetic device in the appearance of the sample. It is found through experiments that, compared with the cold-pressing process in the conventional technology, the proportion of the cracking of the molded magnetic device prepared by the above embodiment has also been significantly reduced.

[0030] In the conventional technology, cold pressing and hot pressing are included. Cold pressing is usually performed at room temperature (25°C), while hot pressing is performed at a temperature above 140°C. In the hot pressing preparation process, the purpose of heating to a temperature above 140°C is mainly to soften the high polymer binder at high temperature, improve its fluidity, make it more easily formed by pressing, and reduce the forming pressure. In actual production, the purpose of using cold pressing process is mainly to obtain higher preparation efficiency, and the purpose of using hot pressing process is to reduce the pressure of sample forming. Cold pressing and hot pressing are two distinct technical routes, and their specific implementation methods also have obvious differences. When solving the problem of cracking of the integrally formed inductor in cold pressing, the common method of the person skilled in the art is to reduce the number of coils or to reduce the coil column, or to reduce the friction between the mold and the inductor.

[0031] The inventors of the present disclosure take a different approach and propose to appropriately increase the mold temperature in the cold pressing process, so that only the binder in contact with the surface of the magnetic device of the mold is cured, so as to improve the surface strength of the magnetic device without affecting the cold pressing forming efficiency and significantly increasing the preparation cost, thereby improving the cracking problem of the sample during cold pressing of the magnetic device.

[0032] In some specific examples of this embodiment, the temperature of the mold is controlled to be 100-120°C during the pressing forming. It is found through experiments that when the temperature of the mold is controlled to be 100-120°C during the pressing forming, the strength of the magnetic device will be greatly improved, and the cracking rate of the sample will be greatly reduced. When the temperature of the mold is further increased, the binder in the sample will be softened due to high temperature, which is prone to glue overflow and mold sticking, and if a longer pressure holding time is not used to make it set, the surface strength of the sample will be significantly reduced.

[0033] In some specific examples of this embodiment, since the temperature is controlled within the above more appropriate range, curing only occurs on the surface layer of the sample, and basically does not bring additional effects to the inside of the sample, therefore, it is still not necessary to prolong the time of pressing the magnetic composite material, so that the magnetic device still has a high preparation efficiency. For example, the time of pressing the magnetic composite material by the mold is maintained within 5s during the pressing forming. Alternatively, the time of pressing the magnetic composite material by the mold can be maintained within 4s. Further alternatively, the time of pressing the magnetic composite material by the mold can be maintained within 3s.

[0034] In some specific examples of this embodiment, the material of the binder can include one or more of an epoxy resin binder, a phenolic resin binder, a cyanate ester binder, and a silicone resin binder.

[0035] In some specific examples of the embodiment, the magnetic material powder can be selected from soft magnetic material powders. The soft magnetic material powders can include one or more of carbonyl iron powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, and iron-silicon powder.

[0036] In some specific examples of the embodiment, the mass of the binder in the magnetic composite material is 6% to 10% of the mass of the magnetic material powder. The mass of the binder in the magnetic composite material is slightly higher than the mass ratio in the prior art, which is to make a little more binder on the surface of the sample to facilitate the heat curing and enhance the surface strength of the sample during the molding process.

[0037] In some specific examples of the embodiment, the process of mixing the binder and the magnetic material powder includes mixing the binder and the magnetic material powder dispersed in a dispersant, and the mass of the dispersant is 10% to 15% of the mass of the magnetic material powder.

[0038] In some specific examples of the embodiment, after mixing the binder and the magnetic material powder, the process further includes a step of drying the formed mixture, and in the step of drying the formed mixture, the temperature of drying is controlled to be below 50°C, and the time of drying is controlled to be below 60 min. It can be understood that the main purpose of drying is to remove the dispersant, and the binder should be avoided from curing as much as possible during the removal of the dispersant, otherwise it can affect the subsequent molding process.

[0039] In some specific examples of the embodiment, the molded magnetic device can be an integrally formed inductor, and in the process of press forming, the coil and the magnetic composite material can be placed in the mold together, and the applied pressure is controlled to be 0.5 to 3T to press form the coil and the magnetic composite material. Optionally, the coil is embedded in the magnetic composite material.

[0040] It can be understood that after the magnetic composite material is press formed in the mold, the process can further include a step of heating the magnetic device to completely cure the binder therein. For example, the magnetic device can be placed in an oven and heated at an environment above 100°C for more than 1h to completely cure the binder.

[0041] Still another embodiment of the present application provides a molded magnetic device prepared according to the preparation method of the molded magnetic device of the above-mentioned embodiment.

[0042] In order to facilitate the understanding of the advantages and implementation modes of the above-mentioned preparation method of the integrally formed inductor, the present disclosure also provides the following examples and comparative examples. Through the performance comparison of the examples and comparative examples, the advantages of the preparation method of the integrally formed inductor of the present disclosure will also be more obvious.

[0043] The materials used in each of the examples and comparative examples can be obtained by purchase from the market, and the materials of the same name and the same process used in each of the examples and comparative examples are exactly the same, unless otherwise specified.

[0044] The magnetic material powder used in the following examples and comparative examples is iron-silicon-chromium powder, specifically Fe 92 Si 3.5 Cr 4.5 with a D50 particle size of 10 μm. The binder used is an epoxy resin binder. The dispersing agent used is acetone.

[0045] Example 1

[0046] 8 parts by mass of an epoxy resin binder and 12 parts by mass of acetone were taken in a container, and stirred uniformly to dissolve the epoxy resin binder in the acetone. 100 parts by mass of the magnetic material powder was added to the prepared epoxy resin acetone solution, and mixed and stirred to form a paste. The obtained paste was put into an extrusion granulator to perform extrusion granulation, and the obtained material was sieved to obtain a raw material meeting the requirements.

[0047] The selected raw material was baked in an oven at 50°C for 60 min to remove the acetone in the raw material, and a magnetic composite material including the binder and the magnetic material powder was obtained.

[0048] The magnetic composite material was placed in a mold for preparing a magnetic ring, and was compression molded at a molding pressure of 5 MPa, to be prepared for strength testing. The magnetic ring had an inner diameter of 8 mm and an outer diameter of 14 mm, and the mold temperature was controlled at 60°C during the molding process, and the compression time was 5 s.

[0049] The magnetic composite material and a coil were placed in a mold for preparing an integrally molded inductor, and an integrally molded inductor of model type 0630-100 was prepared to be prepared for cracking condition testing. The molding pressure was 2T, and the inductor had a size of 6 mm x 6 mm x 3 mm, the coil had an outer diameter of 4.8 max, and a thickness of 2.5 max, and the inductance value was 10 μH. The mold temperature was controlled at 60°C during the molding process, and the compression time was 3 s.

[0050] Example 2

[0051] 8 parts by mass of an epoxy resin binder and 12 parts by mass of acetone were taken in a container, and stirred uniformly to dissolve the epoxy resin binder in the acetone. 100 parts by mass of the magnetic material powder was added to the prepared epoxy resin acetone solution, and mixed and stirred to form a paste. The obtained paste was put into an extrusion granulator to perform extrusion granulation, and the obtained material was sieved to obtain a raw material meeting the requirements.

[0052] The selected raw material was baked in an oven at 50°C for 60 min to remove the acetone in the raw material, and a magnetic composite material including the binder and the magnetic material powder was obtained.

[0053] The magnetic composite material was placed in a mold for preparing a magnetic ring and was compression molded at a molding pressure of 5 MPa, in preparation for strength testing. The magnetic ring had an inner diameter of 8 mm and an outer diameter of 14 mm. The mold temperature was controlled at 80°C during the molding process, and the compression time was 5 s.

[0054] The magnetic composite material and the coil were placed in a mold for preparing an integrally molded inductor, and an integrally molded inductor of model 0630-100 was prepared in preparation for cracking condition testing. The molding pressure was 2 T. The inductor had dimensions of 6 mm x 6 mm x 3 mm, the coil had an outer diameter of 4.8 max, the coil thickness was 2.5 max, and the inductance value was 10 μH. The mold temperature was controlled at 80°C during the molding process, and the compression time was 4 s.

[0055] Example 3

[0056] 8 parts by mass of an epoxy resin binder and 12 parts by mass of acetone were taken in a container, and were stirred uniformly to dissolve the epoxy resin binder in the acetone. 100 parts by mass of a magnetic material powder were added to the prepared epoxy resin-acetone solution, and were mixed and stirred to form a paste. The obtained paste was fed into an extrusion granulator to perform extrusion granulation, and the desired raw material was selected by sieving.

[0057] The selected raw material was baked in an oven at 50°C for 60 min to remove the acetone from the raw material, and a magnetic composite material including a binder and a magnetic material powder was obtained.

[0058] The magnetic composite material was placed in a mold for preparing a magnetic ring and was compression molded at a molding pressure of 5 MPa, in preparation for strength testing. The magnetic ring had an inner diameter of 8 mm and an outer diameter of 14 mm. The mold temperature was controlled at 100°C during the molding process, and the compression time was 5 s.

[0059] The magnetic composite material and the coil were placed in a mold for preparing an integrally molded inductor, and an integrally molded inductor of model 0630-100 was prepared in preparation for cracking condition testing. The molding pressure was 2 T. The inductor had dimensions of 6 mm x 6 mm x 3 mm, the coil had an outer diameter of 4.8 max, the coil thickness was 2.5 max, and the inductance value was 10 μH. The mold temperature was controlled at 100°C during the molding process, and the compression time was 4 s.

[0060] Example 4

[0061] 8 parts by mass of an epoxy resin binder and 12 parts by mass of acetone were taken in a container, and were stirred uniformly to dissolve the epoxy resin binder in the acetone. 100 parts by mass of a magnetic material powder were added to the prepared epoxy resin-acetone solution, and were mixed and stirred to form a paste. The obtained paste was fed into an extrusion granulator to perform extrusion granulation, and the desired raw material was selected by sieving.

[0062] The selected raw material was baked in an oven at 50°C for 60 min to remove the acetone in the raw material, obtaining a magnetic composite material including a binder and a magnetic material powder.

[0063] The magnetic composite material was placed in a mold for preparing a magnetic ring and was compression molded at a molding pressure of 5 MPa, to be prepared for strength testing. The magnetic ring had an inner diameter of 8 mm and an outer diameter of 14 mm. The mold temperature was controlled at 120°C during the molding process, and the compression time was 5 s.

[0064] The magnetic composite material and a coil were placed in a mold for preparing an integrally molded inductor, to be prepared for cracking condition testing. The integrally molded inductor was of a model 0630-100. The molding pressure was 2T. The inductor had a size of 6 mm x 6 mm x 3 mm. The coil had an outer diameter of 4.8 max and a thickness of 2.5 max. The inductance value was 10 μH. The mold temperature was controlled at 120°C during the molding process, and the compression time was 5 s.

[0065] Comparative Example 1

[0066] 8 parts by mass of an epoxy resin binder and 12 parts by mass of acetone were taken in a container and stirred to dissolve the epoxy resin binder in the acetone. 100 parts by mass of a magnetic material powder was added to the prepared epoxy resin acetone solution, and mixed and stirred to form a paste. The obtained paste was fed into an extrusion granulator and sieved to obtain a raw material meeting the requirements.

[0067] The selected raw material was baked in an oven at 60°C for 60 min to remove the acetone in the raw material, obtaining a magnetic composite material including a binder and a magnetic material powder.

[0068] The magnetic composite material was placed in a mold for preparing a magnetic ring and was compression molded at a molding pressure of 5 MPa, to be prepared for strength testing. The magnetic ring had an inner diameter of 8 mm and an outer diameter of 14 mm. The mold temperature was controlled at 25°C during the molding process, and the compression time was 5 s.

[0069] The magnetic composite material and a coil were placed in a mold for preparing an integrally molded inductor, to be prepared for cracking condition testing. The integrally molded inductor was of a model 0630-100. The molding pressure was 2T. The inductor had a size of 6 mm x 6 mm x 3 mm. The coil had an outer diameter of 4.8 max and a thickness of 2.5 max. The inductance value was 10 μH. The mold temperature was controlled at 25°C during the molding process, and the compression time was 5 s.

[0070] Comparative Example 2

[0071] Take 8 parts by mass of epoxy resin binder and 12 parts by mass of acetone in a container, stir uniformly, so that the epoxy resin binder is dissolved in acetone. Take 100 parts by mass of magnetic material powder and add to the prepared epoxy resin acetone solution, mix and stir to form a paste. The obtained paste is put into an extrusion granulator for extrusion granulation, and the required raw materials are selected by sieving.

[0072] The selected raw materials are baked in an oven at 60°C for 60 min to remove acetone from the raw materials, obtaining a magnetic composite material including a binder and a magnetic material powder.

[0073] The magnetic composite material is placed in a mold for preparing a magnetic ring and is compression molded with a molding pressure of 5 MPa, ready for strength testing. The inner diameter of the magnetic ring is 8 mm, and the outer diameter is 14 mm. The mold temperature is controlled at 140°C during molding, and the compression time is 5 s.

[0074] The magnetic composite material and the coil are placed in a mold for preparing an integrally molded inductor, and an integrally molded inductor of model 0630-100 is prepared, ready for cracking condition testing. The molding pressure is 2T, the inductor size is 6mm x 6mm x 3mm, the coil outer diameter is 4.8max, the coil thickness is 2.5max, the inductance value is 10μH, the mold temperature is controlled at 140°C during molding, and the compression time is 5 s.

[0075] Among them, the preparation methods of Examples 1-4 and Comparative Example 1 can prepare magnetic rings and integrally molded inductors that are completely molded and meet the quality requirements. However, the preparation method of Comparative Example 2 has a shorter compression time, and the prepared magnetic ring has the problem of not being molded after the glue melts, and the surface of the compression molded magnetic ring has obvious defects, which can be seen in Figure 1 .

[0076] Test 1: Take 3 magnetic rings prepared in each example and comparative example, test the strength of the magnetic ring, the results can be seen in Table 1.

[0077] Test 2: In the manner of each example and comparative example, 5 integrally molded inductors are prepared, the inductance range is tested; and 2000 integrally molded inductors are prepared, the cracking proportion is tested, the results can be seen in Table 2.

[0078] Table 1: Strength of magnetic ring in each example and comparative example

[0079] Magnetic ring 1 strength / MPa Magnetic ring 2 strength / MPa Magnetic ring 3 strength / MPa Example 1 10.5 11.3 11.9 Example 2 15.7 17.8 17.4 Example 3 19.4 19.7 20.3 Example 4 20.5 20.2 19.7 Comparative Example 1 6.2 6.3 7.1

[0080] Table 2: Strength of magnetic ring in each example and comparative example

[0081] Inductance (μH) Cracking ratio Example 1 9.0～10.4 1.2％ Example 2 9.2～10.9 0.9％ Example 3 9.5～11.2 0.3％ Example 4 9.5～11.5 0.3％ Comparative Example 1 Inductance (μH) Cracking ratio 8.7～10.1 3.7％

[0082] According to Table 1, the average strength of the magnetic ring of Comparative Example 1, which is cold-pressed at room temperature, is about 6.5 MPa, while the average strength of the magnetic ring of Example 1, which is pressed at a higher temperature, is about 11.2 MPa, the average strength of the magnetic ring of Example 2 is about 17.0 MPa, the average strength of the magnetic ring of Example 3 is 19.8 MPa, and the average strength of the magnetic ring of Example 4 is about 20.1 MPa, indicating that the strength of the magnetic device can indeed be significantly improved by appropriately increasing the temperature during pressing. Meanwhile, the other pressing conditions are not changed, indicating that the preparation method of the molded magnetic device of the present application indeed enables the strength of the magnetic device to be improved without substantially changing the traditional cold-pressing process.

[0083] In order to more intuitively understand the improvement effect of the preparation method of the molded magnetic device of the present application on the cracking problem, please refer to Table 2. In Comparative Example 1, 3.7% (i.e. 74) of the integrally formed inductors cracked, while in Example 1, only 24 inductors cracked, in Example 2, 18 inductors cracked, and in Examples 3 and 4, only 6 inductors cracked. The number of cracked inductors in Examples 3 and 4 is only 8.1% of that in Comparative Example 1 and 33% of that in Example 2, which is undoubtedly a very significant effect. In addition, the inductance in Table 2 also indicates that the preparation methods of Examples 1 to 4 not only did not cause the inductance of the inductor to decrease, but also slightly improved the inductance. This indicates that the preparation method of the molded magnetic device of the present application, when preparing integrally formed inductors, does not need to change the traditional pressing process and does not need to consume other materials, and can significantly improve the cracking problem of the inductor without significantly increasing the manufacturing cost.

[0084] Please note that the above examples are for illustrative purposes only and do not mean to limit the present application.

[0085] It should be understood that, unless otherwise explicitly stated herein, the execution of the steps of the method does not have strict order limitations, and the steps can be executed in other orders. Moreover, at least a part of the steps of the method can include multiple sub-steps or multiple stages, which do not necessarily be executed at the same time, but can be executed at different times, and the execution order of the sub-steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least a part of other steps or sub-steps or stages of other steps.

[0086] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0087] Any technical features in the above embodiments can be combined, and for the sake of brevity, not all possible combinations are described, however, any combination of the technical features is considered to be within the scope of the present specification.

Claims

1. A method of fabricating a molded magnetic device, comprising: The molded magnetic device is an integrally formed inductor, comprising the following steps: ​ mixing a binder and a magnetic material powder to prepare a magnetic composite material, wherein the magnetic material powder is selected from a soft magnetic material powder, and the mass of the binder is 6%-10% of the mass of the magnetic material powder in the magnetic composite material; molding the magnetic composite material in a mold to prepare a magnetic device, wherein during the molding, a coil is placed in the mold together with the magnetic composite material, the applied pressure is controlled to be 0.5-3T, the temperature of the mold is controlled to be 60-120℃, the time for which the mold presses the magnetic composite material is controlled to be within 5s, and the binder in the part of the magnetic composite material that contacts the surface of the mold is solidified; after the molding of the magnetic composite material in the mold, the molded magnetic device is heated to completely solidify the binder therein.

2. The method of claim 1, wherein the magnetic device is a magnetic memory device. During the molding, the temperature of the mold is controlled to be 100-120℃.

3. The method of claim 1, wherein the magnetic device is a magnetic memory device. The binder comprises one or more of an epoxy resin binder, a phenolic resin binder, a cyanate ester binder and a silicone resin binder.

4. The method of claim 1, wherein the magnetic device is a magnetic memory device. The magnetic material powder comprises one or more of carbonyl iron powder, iron-silicon-chromium powder, iron-silicon-aluminum powder and iron-silicon powder.

5. The method of claim 1 to 4, wherein The process of mixing the binder and the magnetic material powder comprises dispersing the binder and the magnetic material powder in a dispersant, and the mass of the dispersant is 10%-15% of the mass of the magnetic material powder.

6. The method of claim 1 to 4, wherein After the mixing of the binder and the magnetic material powder, the process further comprises a step of drying the formed mixture, wherein the drying temperature is controlled to be below 50℃, and the drying time is controlled to be below 60min.

7. A molded magnetic device, characterized by, The molded magnetic device is prepared by the preparation method according to any one of claims 1-6.

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