A method for preparing a differential mode inductor

Abstract

The present invention relates to a preparation method of a differential mode inductor, which comprises the following steps: subjecting a nanocrystalline alloy strip to constant tension heat treatment; winding the strip after constant tension heat treatment to form a magnetic core; immersing the magnetic core as a whole in a curing agent of a vacuum impregnator for curing; performing insulation spraying on the dried magnetic core; winding a conductor coil on the magnetic core after insulation spraying to form a winding magnetic core; connecting the two ends of the conductor coil to respective corresponding pin connectors; then connecting the pins to a bottom plate and fixing the winding magnetic core to form a differential mode inductor. The present invention adopts a method of not opening an air gap to avoid a reduction in inductance or leakage magnetic flux, and the process is simpler and the cost is lower. The constant tension heat treatment method can significantly reduce the magnetic permeability of the magnetic core, so that the differential mode inductor has a stronger anti-saturation ability, and further improves the comprehensive performance of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of inductor preparation, and in particular to a method for preparing a differential mode inductor. Background Art

[0002] Inductance components are extremely important components in the current electronics industry. In daily life, common inductance components such as power electronic switches, power supplies, digital circuits, etc. not only generate square wave harmonic interference during use, but also generate motor load interference and power grid interference. These interferences are all differential mode interference caused by differential mode inductance. At present, the effective measure to suppress these interferences is to use differential mode capacitors and differential mode filter inductors to form a low-pass filter. Traditional differential mode inductors are generally made of magnetic materials such as amorphous alloys (FG type), ferrites, iron-nickel alloys, and thin silicon steel. The magnetic permeability of these materials ranges from 10 to 600, the saturation magnetic induction intensity is 0.7-0.8T and the loss is low, but this type of inductance is difficult to achieve a higher dynamic inductance and cannot meet the requirements of suppressing differential mode interference, that is, the inductance has weak DC bias resistance, and amorphous inductors with large dynamic inductance are prone to vibration noise, which will cause the inductor to be unstable when working, and eventually cause increased magnetic loss, affecting the quality factor of the inductor.

[0003] With the rapid development of electronic technology, current power electronic devices are developing in the direction of miniaturization, energy saving and high frequency, and the requirements for processes and materials are getting higher and higher. In order to meet this development demand, it is required that the differential mode inductor allow more and more DC current to pass through at a wider operating frequency. However, the DC component in the differential mode inductor often causes a significant decrease in the inductance value, that is, the anti-saturation ability is poor, making the differential mode inductor unable to work normally. If its anti-magnetic saturation ability is to be improved, the DC bias resistance of the differential mode inductor must be improved. The traditional method is to open an air gap in the magnetic core magnetic circuit (such as patent CN111584226A), but this kind of process is complicated and can only improve the DC superposition characteristics to a certain extent. For differential mode inductors with a large DC current component, this method cannot be adopted, because the air gap in the magnetic core magnetic circuit cannot be opened unlimitedly, otherwise, the inductance will be very low and the leakage magnetic field will be large, which will not only affect the use of the inductor but also cause certain electromagnetic interference to the surrounding electronic components.

[0004] Therefore, further improvements are needed to address the deficiencies in the soft magnetic materials and preparation processes currently used in differential mode inductors. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a method for preparing a differential mode inductor, which can prepare a differential mode inductor with strong anti-saturation ability and strong anti-DC bias ability, and the preparation process is simple. The technical solution adopted by the present invention is as follows:

[0006] A method for preparing a differential mode inductor comprises the following steps:

[0007] Step S1, heat treating the nanocrystalline alloy strip formed by roller shearing, and applying a constant tension along a specific direction of the nanocrystalline alloy strip during the heat treatment process;

[0008] Step S2, winding the strip after constant tension heat treatment to form a magnetic core of predetermined specifications and dimensions;

[0009] Step S3, loading the prepared curing agent into a vacuum impregnation machine, then immersing the entire magnetic core into the curing agent of the vacuum impregnation machine for curing, and drying the cured magnetic core;

[0010] Step S4, performing insulation spraying on the dried magnetic core;

[0011] Step S5, winding the conductor coil on the magnetic core after the insulation spraying to form a winding magnetic core;

[0012] Step S6, making a pin at each end of the conductor coil on the winding magnetic core;

[0013] Step S7, fixing the pins and the winding core on a bottom plate to form a differential mode inductor.

[0014] Furthermore, the saturation magnetic induction intensity of the nanocrystalline alloy strip is above 1.4T.

[0015] Furthermore, in step S1, a constant tension is applied along the length direction of the strip, and the magnitude of the constant tension is 10MPa-100Mpa.

[0016] Furthermore, in step S1, the temperature of the heat treatment is 480°C-600°C.

[0017] Furthermore, the heat treatment holding time is 5s-100s.

[0018] Furthermore, in step S3, the curing agent is one of epoxy resin, organic silicone adhesive, acrylate AB glue, and polyester resin.

[0019] Furthermore, in step S4, the sprayed material is one of epoxy resin, phenolic resin, polyester resin, polyimide resin, and silicone resin.

[0020] Furthermore, in step S3, the baking temperature of the drying treatment is 120°C-200°C, and the heat preservation time of the drying treatment is 1h-6h.

[0021] Furthermore, in step S3, the height of the curing agent covering the magnetic core is above 30 mm.

[0022] Furthermore, in step S3, after the entire magnetic core is immersed in the curing agent of the vacuum impregnation machine, vacuum is drawn and pressurized to maintain curing.

[0023] The beneficial technical effects of the present invention are:

[0024] (1) The present invention uses nanocrystalline soft magnetic materials with high saturation magnetic induction intensity to prepare differential mode inductors, so that the differential mode inductors have excellent characteristics of high frequency, low loss and DC bias resistance, which is conducive to the development of high power and miniaturization.

[0025] (2) The differential mode inductor of the present invention is prepared by a method without an air gap, which can avoid the phenomenon of reduced inductance or magnetic leakage caused by opening an air gap, and simplify the process and reduce the cost. In addition, the constant tension heat treatment method can significantly reduce the magnetic permeability of the magnetic core, so that the differential mode inductor has a stronger anti-saturation ability, further improving the overall performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flowchart of the steps of the method for preparing the differential mode inductor. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0030] See also Figure 1 The present invention provides a method for preparing a differential mode inductor, comprising the following steps.

[0031] Step S1, heat treating the nanocrystalline alloy strip formed by roller shearing, and applying a constant tension along a specific direction of the nanocrystalline alloy strip during the heat treatment process.

[0032] In step S1, a constant tension heat treatment process is performed. According to the performance requirements of the differential mode inductor, a nanocrystalline alloy strip with high saturation magnetic induction intensity that has been roller sheared and inspected and passed the test is selected, and the nanocrystalline alloy strip is placed in a heat treatment furnace, heat treated at a suitable temperature, and a constant tension is applied along a specific direction of the strip during the heat treatment process, and cooled to room temperature after the heat treatment. The high saturation magnetic induction intensity Bs of the selected nanocrystalline alloy strip is above 1.4T; the heat treatment temperature is 480℃-600℃, the holding time is 5s-100s, and the constant tension is 10MPa-100MPa. Preferably, a constant tension is applied along the length direction of the strip. Specifically, the roller-sheared nanocrystalline alloy strip has a predetermined width.

[0033] Step S2, winding the strip after constant tension heat treatment to form a magnetic core of predetermined specifications and dimensions.

[0034] Step S2 is a winding process, in which the nanocrystalline alloy strip after the heat treatment in step S1 is wound into a shape according to the size requirements of the differential mode inductor to obtain a magnetic core.

[0035] Step S3, loading the prepared curing agent into a vacuum impregnation machine, then immersing the entire magnetic core into the curing agent of the vacuum impregnation machine for curing, and drying the cured magnetic core.

[0036] Step S3 is the curing process of the magnetic core: the prepared curing agent is loaded into the vacuum impregnation machine, and then the magnetic core obtained in step S2 is immersed in the curing agent in the vacuum impregnation machine as a whole, and the curing agent covers the magnetic core to a height of at least 30 mm, and then vacuum, pressurize and maintain the pressure for a period of time, so that the magnetic core is fully in contact with the curing agent, and then the magnetic core is taken out and dried. Preferably, the impregnation time is 5min-20min, and preferably, the baking temperature is 120℃-200℃, and the heat preservation is 1h-6h. The curing agent is one of epoxy resin, organic silicone adhesive, acrylate AB glue, and polyester resin. For example, as a preferred embodiment, the curing agent can be selected from epoxy resin, the impregnation time is 5min-20min, and the epoxy resin has only a small volume shrinkage during curing, so as to avoid deformation of the magnetic core after curing. The magnetic core coated with epoxy resin on the surface is placed in an oven for heating and temperature rise, so that the epoxy resin on the surface of each layer of the strip undergoes a curing reaction, wherein the baking temperature is 120℃-200℃, and the heat preservation is 1h-6h.

[0037] Step S4, performing insulation spraying on the dried magnetic core.

[0038] Step S4 is a spraying process, in which the magnetic core cured and dried in step S3 is subjected to insulation spraying. The material selected for spraying is one of epoxy resin, phenolic resin, polyester resin, polyimide resin, and silicone resin. After spraying, baking treatment is performed at a predetermined temperature. Preferably, a layer of epoxy resin protective material is sprayed and coated on the surface of the baked magnetic core, and then baked at 160°C for 1h to solidify the resin on the surface and obtain a certain strength, and finally a nanocrystalline magnetic core is obtained. Using the spraying process instead of the protective box assembly reduces the volume of the magnetic core and also reduces the consumption of wire.

[0039] Step S5, winding the conductor coil on the magnetic core after the insulation spraying to form a winding magnetic core;

[0040] Step S5 is the coil winding process. According to the performance parameters of the differential mode inductor, a conductor coil with a specific number of turns is wound on the magnetic core with a smooth surface and qualified spray thickness sprayed in step S4 to form a winding magnetic core; further, the winding magnetic core is formed by winding an enameled wire on the nanocrystalline magnetic core, and the paint coating of the enameled wire needs to be stripped at both ends to expose the copper wire therein.

[0041] Step S6, making a pin at each end of the conductor coil on the winding magnetic core.

[0042] Step S6 is a pin connection process, in which the two ends of the conductor coil on the winding core in step S5 are respectively connected to the joints of the two pins to realize electrode lead-out.

[0043] Step S7, fixing the pins and the winding core on a bottom plate to form a differential mode inductor.

[0044] Step S7 is the base plate installation process: according to the use requirements of the inductor, the base plate is connected to the pins, and the pin spacing and the winding core are fixed, and finally a differential mode inductor is obtained.

[0045] Example 1

[0046] As a preferred embodiment of the present invention, the differential mode inductor preparation method of the present invention is used to prepare a differential mode inductor with a size of 12.0 mm×6.0 mm×5 mm.

[0047] In this embodiment, a Fe-Si-B-Nb-Cu nanocrystalline alloy strip with a Bs of 1.4T or more and a width of 5mm is selected, and the specific steps are as follows:

[0048] Step S1, constant tension heat treatment: according to the differential mode inductance performance requirements, select a roller-cut nanocrystalline alloy strip with a width of 5 mm and a high saturation magnetic induction intensity that has passed the inspection, and place the nanocrystalline alloy strip in a heat treatment furnace at a heat treatment temperature of 550°C for 30 seconds, and apply a constant tension of 50 MPa along a specific direction of the strip, and cool to room temperature after heat treatment.

[0049] Step S2, winding: according to the differential mode inductor size requirements, the nanocrystalline alloy strip after the heat treatment in step S1 is wound into a shape to obtain a magnetic core.

[0050] Step S3, curing of the magnetic core: put the prepared curing agent into the vacuum impregnation machine, and then immerse the magnetic core obtained in step S2 into the curing agent in the vacuum impregnation machine as a whole, the curing agent covers the magnetic core by 40mm, and then evacuate, pressurize and maintain the pressure for a period of time, so that the magnetic core and the curing agent are fully in contact, then take out the magnetic core and dry it; wherein the curing agent is epoxy resin, and the impregnation is 10min. The epoxy resin has only a small volume shrinkage during curing, so as to avoid deformation of the magnetic core after curing. The magnetic core coated with epoxy resin is placed in an oven for heating and temperature rise, so that the epoxy resin on the surface of each layer of the strip undergoes a curing reaction, wherein the baking temperature is 160℃, and the temperature is kept for 3h.

[0051] Step S4, spraying: Insulation spraying is performed on the magnetic core cured and dried in step S3; specifically, a layer of epoxy resin protective material is sprayed on the surface of the baked magnetic core, and then baked at 160°C for 1 hour to solidify the resin on the surface and obtain a certain strength, and finally a nanocrystalline magnetic core is obtained. Using the spraying process instead of the protective box assembly reduces the volume of the magnetic core and also reduces the consumption of wire.

[0052] Step S5, coil winding: 50 turns of enameled wire with a wire diameter of 0.3 mm are wound on the magnetic core with a smooth surface and qualified spray thickness sprayed in step S4 to make a winding magnetic core; further, the winding magnetic core is made of an enameled wire wound on the nanocrystalline magnetic core, and the paint coating of the enameled wire needs to be stripped at both ends to expose the copper wire therein.

[0053] Step S6, pin connection: connect the two ends of the conductor coil on the winding core in step S5 to the connectors of the two pins respectively to realize electrode lead-out;

[0054] Step S7, base plate installation: according to the use requirements of the inductor, the base plate is connected to the pins, and the pin spacing and the winding core are fixed, and finally a differential mode inductor is obtained.

[0055] The inductance L is 152μH under the conditions of 1V and 1KHz tested by an impedance analyzer; the DC resistance R dc is 180mΩ; saturation current I sat is 1.1A.

[0056] Comparative Example 1

[0057] The same Fe-Si-B-Nb-Cu nanocrystalline alloy strip with a Bs of 1.4T or more and a width of 5mm as in Example 1 was selected to prepare a differential mode inductor with a size of 12.0mm×6.0mm×5mm. The specific steps are as follows:

[0058] Step S1, constant tension heat treatment: according to the differential mode inductance performance requirements, a nanocrystalline alloy strip with a width of 5 mm and high saturation magnetic induction intensity that has passed the inspection and has been cut by a roller is selected, and the nanocrystalline alloy strip is placed in a heat treatment furnace at a heat treatment temperature of 550° C. for 30 seconds, and a constant tension of 50 MPa is applied along a specific direction of the strip, and the strip is cooled to room temperature after the heat treatment;

[0059] Step S2, winding: according to the differential mode inductor size requirements, the nanocrystalline alloy strip after the heat treatment in step S1 is wound into a shape to obtain a magnetic core;

[0060] Step S3, curing of the magnetic core: put the prepared curing agent into the vacuum impregnation machine, and then immerse the magnetic core obtained in step S2 into the curing agent in the vacuum impregnation machine as a whole, the curing agent covers the magnetic core by 40mm, and then evacuate, pressurize and maintain the pressure for a period of time, so that the magnetic core and the curing agent are fully in contact, then take out the magnetic core and dry it; wherein the curing agent is epoxy resin, and the impregnation is 10min. The epoxy resin has only a small volume shrinkage during curing, so as to avoid deformation of the magnetic core after curing. The magnetic core coated with epoxy resin is placed in an oven for heating and temperature rise, so that the epoxy resin on the surface of each layer of the strip undergoes a curing reaction, wherein the baking temperature is 160℃, and the temperature is kept for 3h.

[0061] Step S4, air gap cutting: according to product application and performance, the cured magnetic core is cut into air gap openings with a spacing of 2 mm, and an insulating plate matching the air gap opening is placed into the air gap opening.

[0062] Step S5, spraying: Insulation spraying is performed on the magnetic core cured and dried in step S3; specifically, a layer of epoxy resin protective material is sprayed on the surface of the baked magnetic core, and then baked at 160°C for 1 hour to solidify the resin on the surface and obtain a certain strength, and finally a nanocrystalline magnetic core is obtained. Using the spraying process instead of the protective box assembly reduces the volume of the magnetic core and also reduces the consumption of wire.

[0063] Step S6, coil winding: 50 turns of enameled wire with a wire diameter of 0.3 mm are wound on the magnetic core with a smooth surface and qualified spray thickness sprayed in step S4 to make a winding magnetic core; further, the winding magnetic core is made of an enameled wire wound on the nanocrystalline magnetic core, and the paint coating of the enameled wire needs to be stripped at both ends to expose the copper wire therein.

[0064] Step S7, pin connection: connect the two ends of the conductor coil on the winding core in step S5 to the connectors of the two pins respectively to realize electrode lead-out;

[0065] Step S8, base plate installation: according to the use requirements of the inductor, the base plate is connected to the pins, and the pin spacing and the winding core are fixed, and finally a differential mode inductor is obtained.

[0066] The impedance analyzer was used to test the inductance L at 1V, 1KHz to be 125μH; the DC resistance R dc 230mΩ; saturation current I sat It is 0.65A.

[0067] Comparative Example 2

[0068] The same Fe-Si-B-Nb-Cu nanocrystalline alloy strip with a Bs of 1.4T or more and a width of 5mm as in Example 1 was selected to prepare a differential mode inductor with a size of 12.0mm×6.0mm×5mm. It is a conventional heat treatment method not to apply tensile stress during heat treatment. The remaining preparation methods, steps, and process parameters are the same as those in Comparative Example 1 to obtain a differential mode inductor. The same performance test conditions as in Example 1 were used, and the obtained performance parameters are shown in Table 1.

[0069] Comparative Example 3

[0070] The same Fe-Si-B-Nb-Cu nanocrystalline alloy strip with a Bs of 1.4T or more and a width of 5mm as in Example 1 was selected to prepare a differential mode inductor with a size of 12.0mm×6.0mm×5mm, without cutting the air gap, and the remaining preparation methods, steps, and process parameters were the same as those in Comparative Example 1 to obtain a differential mode inductor. The same performance test conditions as in Example 1 were used, and the obtained performance parameters are shown in Table 1.

[0071] Comparative Examples 4-6

[0072] Comparative Examples 4-6 respectively selected Fe-Si-B amorphous alloy strips, Fe-Si-Ni strips and Fe-Si-Al strips with Bs of less than 1.4T and a width of 5mm, which were different from those in Example 1, to prepare differential mode inductors with a size of 12.0mm×6.0mm×5mm. The remaining preparation methods, steps and process parameters were the same as those in Comparative Example 1 to obtain differential mode inductors. The same performance test conditions as in Example 1 were used, and the performance parameters obtained were shown in Table 2.

[0073] Table 1 Performance parameters of differential mode inductors made from the same strips under different conditions in Example 1 and Comparative Examples 1-3

[0074]

[0075] Table 1 shows the inductance L (μH) and DC resistance R of the differential mode inductors made of the same strip material in Example 1 and Comparative Examples 1-3 using different preparation processes. dc (mΩ), saturation current I sat (A).

[0076] It can be seen from Table 1 that nanocrystalline ribbons are used to prepare magnetic cores in Example 1 and Comparative Examples 1-3. By comparison, the magnetic cores wound with nanocrystalline ribbons after constant tension heat treatment have large inductance, lower DC resistance, and higher saturation current, so that the differential mode inductor finally prepared has stronger anti-saturation ability and larger conduction margin, which is conducive to the development of miniaturization, high frequency, and high power.

[0077] Table 2 Performance parameters of differential mode inductors made of different strips under the same conditions in Example 1 and Comparative Examples 4-6

[0078]

[0079] Table 2 shows the magnetic permeability and DC resistance R of the differential mode inductors made of different strips in Example 1 and Comparative Examples 4-6 using the same preparation process. dc (mΩ), saturation current I sat (A).

[0080] It can be seen from Table 2 that the differential mode inductance permeability and DC resistance R dc (mΩ), saturation current I sat (A) are superior to the performance of differential mode inductors made of other amorphous strips.

[0081] In summary:

[0082] The present invention selects nanocrystalline soft magnetic materials with high saturation magnetic induction intensity to prepare differential mode inductors, so that the differential mode inductors have excellent characteristics of high frequency, low loss and DC bias resistance, which is conducive to the development of high power and miniaturization.

[0083] The differential mode inductor of the present invention is prepared by a method without opening an air gap, which can avoid the phenomenon of reduced inductance or magnetic leakage caused by opening an air gap, and simplify the process and reduce the cost. In addition, the constant tension heat treatment method can significantly reduce the magnetic permeability of the magnetic core, so that the differential mode inductor has a stronger anti-saturation ability, further improving the comprehensive performance of the device.

[0084] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a differential mode inductor, characterized in that: The steps include: Step S1, heat treating the nanocrystalline alloy strip formed by roller shearing, and applying a constant tension along a specific direction of the nanocrystalline alloy strip during the heat treatment process. In step S1, the constant tension is applied along the length direction of the strip, and the magnitude of the constant tension is 10MPa-100Mpa; Step S2, winding the strip after constant tension heat treatment to form a magnetic core of predetermined specifications and dimensions; Step S3, loading the prepared curing agent into a vacuum impregnation machine, then immersing the entire magnetic core into the curing agent of the vacuum impregnation machine for curing, and drying the cured magnetic core; Step S4, performing insulation spraying on the dried magnetic core; Step S5, winding the conductor coil on the magnetic core after insulation spraying to form a winding magnetic core; Step S6, making a pin at each end of the conductor coil on the winding magnetic core; Step S7, fixing the pins and the winding core on a bottom plate to form the differential mode inductor.

2. The method for preparing a differential mode inductor according to claim 1, characterized in that: The saturation magnetic induction intensity of the nanocrystalline alloy strip is above 1.4T.

3. The method for preparing a differential mode inductor according to claim 1, characterized in that: In the step S1, the temperature of the heat treatment is 480°C-600°C.

4. The method for preparing a differential mode inductor according to claim 3, characterized in that: The heat treatment holding time is 5s-100s.

5. The method for preparing a differential mode inductor according to claim 1, characterized in that: In step S3, the curing agent is one of epoxy resin, organic silicone adhesive, acrylate AB glue, and polyester resin.

6. The method for preparing a differential mode inductor according to claim 1, characterized in that: In the step S4, the sprayed material is one of epoxy resin, phenolic resin, polyester resin, polyimide resin and silicone resin.

7. The method for preparing a differential mode inductor according to claim 1, characterized in that: In the step S3, the baking temperature of the drying treatment is 120° C.-200° C., and the heat preservation time of the drying treatment is 1 h-6 h.

8. The method for preparing a differential mode inductor according to claim 1, characterized in that: In the step S3, the height of the curing agent covering the magnetic core is above 30 mm.

9. The method for preparing a differential mode inductor according to claim 1, characterized in that: In the step S3, after the entire magnetic core is immersed in the curing agent of the vacuum impregnation machine, vacuum is drawn and pressure is applied to maintain the curing.

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