Integrally-formed inductor and preparation method thereof

Abstract

The invention relates to an integrally-formed inductor and a preparation method thereof.The preparation method of the integrally-formed inductor comprises the following steps that a cylindrical iron core is attracted to a base to serve as a mold for winding, winding is conducted, and the height of a coil is made to be larger than the height of the iron core by 0.6 mm or above; after winding is completed, magnetic sealing glue is dropped from the top, so that the magnetic sealing glue permeates into a coil area from the top of the iron core, and then the magnetic sealing glue is shaped and solidified through hot air; placing the shaped and cured iron core and coil in the center of a square mold cavity; filling magnetic powder is poured into the mold cavity from the four corners of the square mold cavity; pressing by adopting an up-and-down simultaneous pressurizing mode, and then demolding to obtain a first green body; taking out the green body, cutting off the lead end, bending the lead end exposed out of the green body, and baking to obtain an integrally formed inductor; according to the method, the internal and external densities of the inductor are uniform, so that the saturation current of the inductor is effectively improved, and the direct-current resistance of the inductor is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of inductors, and more specifically, to an integrally formed inductor and a preparation method thereof. Background Art

[0002] The most widely used one-piece molded inductor is one-piece molded and pressed in a mold using round wire as the electrode. The process is as follows: first, wind the enameled copper wire with a circular interface on the cylindrical mold bracket to the required number of turns; weld the two ends of the wound wire weight to the lead wire frame; put the lead frame with the coil welded into the mold with the coil centered; mix the atomized alloy powder, carbonyl iron powder, or amorphous powder with the thermosetting epoxy resin, stir and knead them evenly, use a reciprocating granulator to screen and granulate through 40-80 mesh, bake at 50-80℃ for 2h, and set aside; pour the powder into the mold, press it with a hydraulic press at 400-1000MPa, and demold it by holding the pressure for 10-60s; take out the demolded blank, cut off the lead end, and bend the lead end exposed to the blank; bake it again at 110-130℃ for 1-2h to completely cure the resin, and it is done.

[0003] However, during the pressing process, the presence of the coil will change the pressure distribution in the entire mold cavity. The pressure in the central part surrounded by the coil is lower than that in other parts, which leads to a loose central area. The larger the number of coils, the more obvious this phenomenon is. The loose central area will cause the material magnetic permeability to be low, and more coils are required to obtain the same inductance, resulting in excessive DC resistance. In addition, the air inside will have a greater probability of bulging and cracking during baking. Summary of the invention

[0004] Based on the above-mentioned technical problems existing in the prior art, the present invention provides a method for preparing a molded inductor, which can effectively solve the problem that the center of the traditional one-piece molded inductor is not dense, resulting in low magnetic permeability and thus excessive DC resistance, and the problem of bulging and cracking caused by the baking process due to uneven density inside and outside the blank.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing an integrally formed inductor comprises the following steps:

[0007] S1. Adsorb the cylindrical iron core on the base as a winding mold, and perform winding so that the height of the coil is greater than the height of the iron core by more than 0.6 mm;

[0008] S2. After the winding is completed, magnetic sealing glue is dripped from the top to make the magnetic sealing glue penetrate into the coil area from the top of the core, and then hot air is used to shape and solidify it;

[0009] S3, placing the shaped and cured iron core and coil in the center of the square mold cavity;

[0010] S4, pouring the filling magnetic powder into the mold cavity from the four corners of the square mold cavity;

[0011] S5, pressing by applying pressure from both top and bottom simultaneously, and then demolding to obtain a first green body;

[0012] S6, taking out the green body, cutting off the lead ends, bending the lead ends exposed from the green body, and baking to obtain an integrally formed inductor.

[0013] In some embodiments, in step S2, the hot air temperature is 80-110°C.

[0014] In some embodiments, in step S5, the pressing pressure is 40-60 MPa, and the holding time is 10-60 s.

[0015] In some embodiments, in step S6, the baking temperature is 110-130° C., and the baking time is 1-2 h.

[0016] In some embodiments, the method for preparing the core comprises the following steps:

[0017] At least two of amorphous powder, iron-silicon-chromium, iron-nickel alloy powder, and carbonyl iron powder that have been coated with SiO2 insulation are mixed in proportion, polyethylene glycol, a first epoxy resin, and BSi glass powder are added, and after being fully mixed, granulated, and then dried; then added into a mold, pressed into a cylindrical shape, and demolded to obtain a second green body; the second green body is sintered in a nitrogen atmosphere to obtain the iron core;

[0018] The amount of polyethylene glycol is 1.5-3.0wt% of the powder mass; the first epoxy resin is 0.5-1.0wt% of the powder mass; the softening temperature of BSi glass powder is lower than 700°C, and the amount of BSi glass powder is 1.5-2.0wt% of the powder mass. Polyethylene glycol plays a major bonding role and is easy to decompose; epoxy resin is used to further enhance the bonding effect; and the role of BSi glass powder is to accelerate the exhaust stroke grain boundary bonding phase during sintering, and control the grain growth, so as to avoid the use of high pressure molding.

[0019] In some embodiments, the sintering temperature of the second green body is 750-900° C., and the sintering time is 1-3 hours.

[0020] In some embodiments, the preparation of the magnetic sealing adhesive comprises the following steps:

[0021] The iron-nickel powder with D50=3-5μm that has been phosphated or SiO2-insulated, the second epoxy resin and pineneol are mixed and then ball-milled; wherein the ball-to-material mass ratio is 3-5:1, and during the ball-milling process, the viscosity is controlled at 2000-3000cps; the mass of the second epoxy resin is 12.0-16.0wt% of the mass of the nickel-iron powder, and the mass of the pineneol is 10.0-15.0wt% of the mass of the nickel-iron powder.

[0022] In some embodiments, the preparation of the filled magnetic powder comprises the following steps:

[0023] Mixing and kneading the iron-silicon-chromium alloy powder with D50=5-7μm and SiO2 insulation coating with the third epoxy resin, adding a curing accelerator, granulating through a 100-120 mesh sieve, removing fine particles under a 200 mesh sieve, and drying to obtain the filled magnetic powder;

[0024] The third epoxy resin is a thermosetting epoxy resin, and the amount used is 6.0-9.0wt% of the mass of the iron-silicon-chromium alloy powder; the amount of the curing accelerator is 1.0wt%-1.5wt% of the third epoxy resin. The use of finer filling magnetic powder and a larger proportion of resin can reduce the pressing pressure while ensuring the strength of the product, thereby reducing the scratches on the electrode and reducing the probability of short circuit.

[0025] The present invention also provides an inductor obtained by the preparation method of any of the above embodiments.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention firstly uses a cylindrical iron core as a mold for winding, and then shapes the two by magnetic sealing glue and places them in the center of a square mold, and then adds filling magnetic powder through the four corners of the mold and presses them, so that the internal and external densities of the blank are more uniform.

[0028] The present invention directly places the formed iron core in the coil. Due to the high magnetic permeability of the iron core, for products with the same inductance, fewer turns are required, and the DC resistance of the product can be reduced by 20-50%. The filling magnetic powder is first added around the iron core, so that the density inside and outside the pressed blank is more uniform, and the probability of bulging and cracking during sintering is reduced to less than 1 / 10 of the prior art. In addition, the method of the present invention uses less pressure in the process of pressing the filling powder, greatly reducing the probability of the powder scratching the electrode, thereby reducing the probability of short circuit, and reducing the probability of damage to the electrode to less than 1 / 10 of the prior art.

[0029] The inductor obtained by the method of the present invention has fewer turns of the coil under the condition of the same inductance value and size, and has a higher saturation current and lower direct current resistance, showing excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the one-piece molded inductor obtained in Examples 1-3 and Comparative Examples 1-9;

[0031] Figure 2 Another schematic diagram of the structure of the integrally formed inductor obtained in Example 1-3 and Comparative Example 1-9;

[0032] Figure 3 for Figure 2 The view in the AA direction;

[0033] Among them, 1-sintered magnetic core, 2-copper wire, 3-magnetic sealing glue, 4-filled magnetic powder, 5-lead-out terminal electrode. DETAILED DESCRIPTION

[0034] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] Example 1

[0037] Preparation of iron core: Mix amorphous powder with D50=20-26μm SiO2 insulation coating, iron silicon chromium powder with D50=9-12μm SiO2 insulation coating, and iron nickel powder with D50=4-6μm SiO2 insulation coating in a mass ratio of 4:4:2 to obtain a mixed powder; add polyethylene glycol, epoxy resin, and BSi glass powder with a softening temperature below 700°C, stir and knead thoroughly, and granulate through a 40-80 mesh sieve with a reciprocating granulator, remove 200 The target fine particles are baked at a temperature of 50°C for 1 hour; then added into a mold, maintained at a pressure of 50MPa for 50 seconds, pressed into a cylindrical shape, demolded to obtain a green body; the green body is placed in an atmosphere furnace under a nitrogen atmosphere, heated to 800°C for sintering for 2 hours, and naturally cooled to room temperature to obtain an iron core; wherein polyethylene glycol is 2.0wt% of the mass of the mixed powder, epoxy resin is 1.0wt% of the mass of the mixed powder, and BSi glass powder is 2.0wt% of the mass of the mixed powder;

[0038] Preparation of magnetic sealant: Mix phosphating iron-nickel powder with D50=3-5μm, epoxy resin and pinene alcohol, and use a roller mill for ball milling for 6h to obtain magnetic sealant; wherein the amount of epoxy resin is 15wt% of the mass of the iron-nickel powder, and the amount of pinene alcohol is 12wt% of the mass of the iron-nickel powder; the mass ratio of the grinding medium balls to the iron-nickel powder in the roller mill is 5:1, and the viscosity of the mixed material is controlled to be 2000-3000cps during the ball milling process;

[0039] Preparation of filling magnetic powder: fully mix and stir iron-silicon-chromium alloy powder with D50=5-7μm 800 mesh sieve that has been coated with SiO2 insulation and knead with thermosetting epoxy resin, add 2-methylimidazole, granulate with a reciprocating granulator through a 100-120 mesh sieve, remove fine particles of 200 mesh, bake at 60°C for 2h to obtain filling magnetic powder; wherein the mass of thermosetting epoxy resin is 7.0wt% of the mass of alloy powder, and the amount of 2-methylimidazole is 1.0wt% of the thermosetting epoxy resin;

[0040] A method for preparing an integrally formed inductor comprises the following steps:

[0041] S1. The cylindrical iron core prepared in this embodiment is adsorbed on the base as a winding mold, and the copper wire is used for winding. After the height of the coil is greater than the height of the iron core by 1.0 mm, one end of the copper wire is wound along the outside of the coil to form a double-layer coil, and both ends of the copper wire are led out to form lead-out electrodes;

[0042] S2. After the winding is completed, the magnetic sealing glue prepared in this embodiment is dripped from the top to make the magnetic sealing glue penetrate into the coil area from the top of the core, and then the magnetic sealing glue is quickly shaped and cured with hot air at 100°C;

[0043] S3, placing the shaped and cured iron core and coil in the center of the square mold cavity;

[0044] S4, pouring the filling magnetic powder prepared in this embodiment into the mold cavity from the four corners of the square mold cavity;

[0045] S5, pressing by applying pressure from top to bottom at the same time, the pressure is 60MPa, the pressure is maintained for 50s, and then demolding is performed to obtain a green body;

[0046] S6, taking out the blank, cutting off the lead ends, bending the lead ends exposed from the blank, and baking at 120° C. for 2 hours to completely solidify the resin, thereby obtaining an integrally formed inductor, the structure of which is as follows: Figure 1-Figure 3 As shown, in the obtained inductor, the copper wire 2 is wound on the side of the sintered iron core 1 to form a double-layer coil, both ends of the copper wire 2 are led out at one end of the sintered iron core 1 to form a lead-out terminal electrode 5, the magnetic sealing glue 3 penetrates into the gap between the sintered iron core 1 and the coil formed by the copper wire 2 and the gap between the coils, and the filling magnetic powder 4 is wrapped around the outside of the coil and the sintered iron core 1.

[0047] Comparative Example 1

[0048] Preparation of iron core powder: Mix D50=20-26μmSiO2 insulation coated amorphous powder, D50=9-12μmSiO2 insulation coated iron silicon chromium powder, D50=4-6μmSiO2 insulation coated iron nickel powder in a mass ratio of 4:4:2 to obtain a mixed powder; add polyethylene glycol, epoxy resin, and BSi glass powder with a softening temperature below 700°C, mix and stir to knead evenly, use a reciprocating granulator to sieve through a 40-80 mesh sieve to remove fine particles of 200 mesh, and bake at a temperature of 50°C for 1h; wherein polyethylene glycol accounts for 2.0wt% of the mass of the mixed powder, epoxy resin accounts for 1.0wt% of the mass of the mixed powder, and BSi glass powder accounts for 2.0wt% of the mass of the mixed powder;

[0049] Preparation of magnetic sealing glue: the same as in Example 1;

[0050] Preparation of filling powder: the same as in Example 1;

[0051] The method for preparing an integrally formed inductor comprises the following steps:

[0052] S1. Winding the enameled copper wire with a circular cross section on a cylindrical mold support for the required number of turns;

[0053] S2. Weld the two ends of the wound coil to the lead-out wire frame;

[0054] S3, placing the lead frame with the coil welded thereon into the mold cavity, with the coil centered;

[0055] S5. Place the coil in the center of the square mold cavity, then pour the powder into the coil, and then drip the magnetic sealant from the top to make the magnetic sealant penetrate into the inside from the top of the coil; then pour the filling magnetic powder through the four corners of the square mold cavity, press with a hydraulic press, pressurize at 600MPa, hold the pressure for 50s, and then demold to obtain a green body;

[0056] S6, taking out the blank, cutting off the lead ends, and bending the lead ends exposed from the blank;

[0057] S7. Bake again at 120°C for 2h to completely cure the resin. Finished.

[0058] Comparative Example 2

[0059] The composition and preparation method of the iron core, the filling and preparation method of the magnetic powder, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 1, except that after the winding is completed, no magnetic sealing glue is added, and the iron core and the coil are directly placed in the center of the square mold cavity.

[0060] Comparative Example 3

[0061] The composition and preparation method of the iron core, the filling magnetic powder and preparation method, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 1, except that in step S4, the filling magnetic powder is added by the traditional center injection method.

[0062] Example 2

[0063] The difference between this embodiment and embodiment 1 is that, in the process of preparing the iron core, the powder used is a mixture of amorphous powder with D50=13-17μm, coarse carbonyl powder with D50=7-9μm, and fine carbonyl powder with D50=2-4μm in the ratio of 2:4:4; the preparation method and process conditions are the same as those in embodiment 1.

[0064] Comparative Example 4

[0065] The composition of the iron core powder in this comparative example is the same as that in Example 2, and the preparation method and process conditions are the same as those in Comparative Example 1.

[0066] Comparative Example 5

[0067] The composition and preparation method of the iron core, the filling and preparation method of the magnetic powder, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 2, except that after the winding is completed, no magnetic sealing glue is added, and the iron core and the coil are directly placed in the center of the square mold cavity.

[0068] Comparative Example 6

[0069] The composition and preparation method of the iron core, the filling magnetic powder and the preparation method, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 2, except that in step S4, the filling magnetic powder is added by the traditional center injection method. Example 3

[0070] The difference between this embodiment and embodiment 1 is that, in the process of preparing the iron core, the powder used is a mixture of amorphous powder with D50=13-17μm, iron silicon chromium powder with D50=9-12μm, and fine iron silicon chromium powder with D50=3-5μm in the ratio of 2:4:4; the preparation method and process conditions are the same as those in embodiment 1.

[0071] Comparative Example 7

[0072] The composition of the iron core powder in this comparative example is the same as that in Example 3, and the preparation method and process conditions are the same as those in Comparative Example 1.

[0073] Comparative Example 8

[0074] The composition and preparation method of the iron core, the filling and preparation method of the magnetic powder, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 3, except that after the winding is completed, no magnetic sealing glue is added, and the iron core and the coil are directly placed in the center of the square mold cavity.

[0075] Comparative Example 9

[0076] The composition and preparation method of the iron core, the filling magnetic powder and preparation method, and the preparation method of the integrally formed inductor in this comparative example are the same as those in Example 3, except that in step S4, the filling magnetic powder is added by the traditional center injection method.

[0077] The one-piece molded inductors obtained in Examples 1-3 and Comparative Examples 1-9 were subjected to performance tests, and the test results are shown in Table 1.

[0078] Table 1 Performance test results of the inductors obtained in Examples 1-3 and Comparative Examples 1-3

[0079]

[0080] In summary, under the premise of the same size and inductance value, the inductor obtained by the method of the present invention has a higher saturation current and a lower resistance, and the number of coil turns is lower and the amount of Cu used is less.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing an integrally formed inductor, characterized in that: The following steps are involved: S1. Adsorb the cylindrical iron core on the base as a winding mold, and perform winding so that the height of the coil is greater than the height of the iron core by more than 0.6 mm; S2. After the winding is completed, magnetic sealing glue is dripped from the top to make the magnetic sealing glue penetrate into the coil area from the top of the core, and then hot air is used to shape and solidify it; S3, placing the shaped and cured iron core and coil in the center of the square mold cavity; S4, pouring the filling magnetic powder into the mold cavity from the four corners of the square mold cavity; S5, pressing by applying pressure from both top and bottom simultaneously, and then demolding to obtain a first green body; S6, taking out the green body, cutting off the lead ends, bending the lead ends exposed from the green body, and baking to obtain an integrally formed inductor.

2. The method for preparing an integrally formed inductor according to claim 1, characterized in that: In step S2, the hot air temperature is 80-110°C.

3. The method for preparing an integrally formed inductor according to claim 1, characterized in that: In step S5, the pressing pressure is 40-60 MPa, and the holding time is 10-60 s.

4. The method for preparing an integrally formed inductor according to claim 1, characterized in that: In step S6, the baking temperature is 110-130° C. and the baking time is 1-2 hours.

5. The method for preparing an integrally formed inductor according to claim 1, characterized in that: The method for preparing the iron core comprises the following steps: At least two of amorphous powder, iron-silicon-chromium, iron-nickel alloy powder, and carbonyl iron powder that have been coated with SiO2 insulation are mixed in proportion, polyethylene glycol, a first epoxy resin, and BSi glass powder are added, and after being fully mixed, granulated, and then dried; then added into a mold, pressed into a cylindrical shape, and demolded to obtain a second green body; the second green body is sintered in a nitrogen atmosphere to obtain the iron core; The amount of polyethylene glycol is 1.5-3.0wt% of the powder mass; the first epoxy resin is 0.5-1.0wt% of the powder mass; the softening temperature of BSi glass powder is lower than 700°C, and the amount is 1.5-2.0wt% of the powder mass.

6. The method for preparing an integrally formed inductor according to claim 5, characterized in that: The sintering temperature of the second green body is 750-900° C., and the sintering time is 1-3 hours.

7. The method for preparing an integrally formed inductor according to claim 1, characterized in that: The preparation of the magnetic sealing glue comprises the following steps: The iron-nickel powder with D50=3-5μm that has been phosphated or SiO2-insulated, the second epoxy resin and pineneol are mixed and then ball-milled; wherein the ball-to-material mass ratio is 3-5:1, and during the ball-milling process, the viscosity is controlled at 2000-3000cps; the mass of the second epoxy resin is 12.0-16.0wt% of the mass of the nickel-iron powder, and the mass of the pineneol is 10.0-15.0wt% of the mass of the nickel-iron powder.

8. The method for preparing an integrally formed inductor according to claim 1, characterized in that: The preparation of the filled magnetic powder comprises the following steps: Mixing and kneading the iron-silicon-chromium alloy powder with D50=5-7μm and SiO2 insulation coating with the third epoxy resin, adding a curing accelerator, granulating through a 100-120 mesh sieve, removing fine particles under a 200 mesh sieve, and drying to obtain the filled magnetic powder; Wherein, the third epoxy resin is a thermosetting epoxy resin, and the dosage thereof is 6.0-9.0wt% of the mass of the iron-silicon-chromium alloy powder; the dosage of the curing accelerator is 1.0wt%-1.5wt% of the third epoxy resin.

9. The one-piece molded inductor according to any one of claims 1 to 8.

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