CN112582134A - Preparation method of high-reliability molded inductor and molded inductor thereof - Google Patents
Preparation method of high-reliability molded inductor and molded inductor thereof Download PDFInfo
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- CN112582134A CN112582134A CN201910937368.3A CN201910937368A CN112582134A CN 112582134 A CN112582134 A CN 112582134A CN 201910937368 A CN201910937368 A CN 201910937368A CN 112582134 A CN112582134 A CN 112582134A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/24—Magnetic cores
- H01F27/255—Magnetic cores made from particles
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/02—Casings
- H01F27/022—Encapsulation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/2823—Wires
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/005—Impregnating or encapsulating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
Abstract
The invention provides a preparation method of a high-reliability molded inductor and the inductor. The die-pressing inductor prepared by the method solves the problem of short circuit of the die-pressing inductor by improving the deformation of the die-pressing inductor coil winding and the damage effect of metal powder on the coil winding. The specific method comprises (1) reducing coil deformation by 50% or more by filling prefabricated iron core in the center of coil winding, (2) reducing coil deformation by 10% or more by increasing the loose packed density of granulated powder to 2.2g/cm3 or more, and (3) coating magnetic powder glue with thickness of 3um or more on the outer edge of coil windingEssentially the effect of the metal powder on the breakage of the coil during the die-pressing process is eliminated, (4) the plastic deformation strength σ of the soft-magnetic metal powder0.2The ratio of the molding pressure to the molding pressure of the molded inductor must be 0.33 or more and less than 0.80. The invention has the innovation that the short circuit problem of the molded inductor in the use process is solved in principle, and particularly, the molded inductor resists direct-current voltage to reach>And (5) =1000V/cm or more.
Description
Technical Field
The invention relates to a preparation method of a high-reliability molded inductor and the molded inductor, belonging to the field of electronic components.
Background
With the gradual development and mutual fusion of network technology, computer technology, communication technology and artificial intelligence technology, people begin to enter the fourth industrial revolution era; the era is mainly characterized in that close connection and information interaction are established between people and people, between objects and between people and objects, so that new life styles such as smart phones, smart homes, smart cities and the like appear, and along with the gradual breakthrough of related bottleneck technologies, intelligent transportation (including internet automobiles, intelligent parking and the like), AI robots, even the early and late AI robots, the society, agriculture and industry, and related internet of things can appear. The complex connections depend on the information transmission, communication and processing of a hardware system, can be an information transmitting end, an information receiving end and a cloud end, and the key of the intelligent hardware is a chip and related components.
The molded inductor is widely used in various intelligent hardware systems, such as smart phones, smart televisions, smart home appliances, tablet computers, notebook computers, various communication terminals and servers, as one of the main passive components around the chip, and the main functions of the molded inductor include conversion, storage and filtering of electromagnetic signals and energy. The molded inductor is composed of a coil winding and an iron core, wherein the coil is preset in a mold, and the empty space inside and around the coil winding is filled with metal soft magnetic powder and is molded by pressing, so that the molded inductor has excellent EMI interference resistance and a completely closed magnetic structure.
In various electronic and power electronic devices, the devices are generally required to have good insulation and EMI (electromagnetic interference) resistance while having functionality, so that the molded inductor made of metal powder requires first surface insulation treatment of the powder, including passivation and granulation, and in addition, the copper wire used for the coil winding must have an insulation layer on the surface (commonly called enameled wire). With the popularization and application of electric vehicles, internet of things, cloud servers, intelligent technologies and new semiconductor materials, the requirements on the stability of devices are higher and higher, and the use frequency is higher and higher, so that some reliability problems occur, for example, the insulation resistance > =100M Ώ/cm in the long-term use process of molded inductors required by automobile electronics, and the voltage withstanding grade is improved from the current 50V to 300V or even higher.
However, the molding process of molding the inductor is just a process of damaging the coil winding, and the coil winding is pressed by powder to have defects of overall deformation, deformation of the cross section of the copper wire, scratch and the like. Resulting in the attenuation of the initial withstand voltage of the coil from 1000V or more to 300V or less.
The invention provides a preparation method of a high-reliability molded inductor and the molded inductor, the deformation of the cross section of the molded inductor coil prepared by the method is reduced by 50% or more, and the direct-current voltage resistance between a molded inductor terminal and an iron core is > 1000V/cm or more. The invention improves the deformation of the molded inductance coil winding and the damage of the metal powder to the coil winding, so that the molded inductance prepared by the method fundamentally solves the short circuit problem of the molded inductance. The specific method comprises the steps of (1) reducing the coil deformation by 50% or more by filling the prefabricated iron core in the center of a coil winding, (2) reducing the coil deformation by 10% or more by increasing the loose packing density of granulated powder to 2.2g/cm3 or more, (3) essentially eliminating the damage of metal powder to the coil in the die pressing process by coating magnetic powder glue on the outer edge of the coil winding, and (4) ensuring that the ratio of the plastic deformation strength of the soft magnetic metal powder to the forming pressure of the die pressing inductance is more than or equal to 0.33 and less than 0.80 so as to reduce the deformation of the metal powder as much as possible while increasing the density, thereby reducing the relative displacement distance between the powder and the coil in the close contact process in the die pressing process. The innovation of the invention is that the damage factor of the coil short circuit is considered comprehensively from the mechanism and is combined with the comprehensive construction of the preparation process of the molded inductor, thereby solving the short circuit problem of the molded inductor in the using process from the principle and essence.
Disclosure of Invention
The invention provides a preparation method of a high-reliability molded inductor and the molded inductor. The die pressing inductor prepared by the method fundamentally solves the problem of short circuit of the die pressing inductor by improving the deformation of the die pressing inductor coil winding and the damage effect of metal powder on the coil winding. The method mainly comprises the steps of (1) reducing the coil deformation by 50% or more by filling a prefabricated iron core in the center of a coil winding, (2) reducing the coil deformation by 10% or more by increasing the loose packing density of granulated powder to 2.2g/cm3 or more, (3) essentially eliminating the damage of metal powder to the coil in the die pressing process by coating magnetic powder glue on the outer edge of the coil winding, and (4) ensuring that the ratio of the plastic deformation strength of soft magnetic metal powder to the forming pressure of die pressing inductance is more than or equal to 0.33 and less than 0.80 so as to reduce the deformation of the metal powder as much as possible while increasing the density, thereby reducing the relative displacement distance between the powder and the coil in the close contact process in the die pressing process. The innovation of the invention is that the damage factor of the coil short circuit is considered in a comprehensive mode in combination with the preparation process of the molded inductor in the mechanism, the short circuit problem of the molded inductor in the use process is solved in principle and essentially, and the specific invention content is as follows:
the soft magnetic metal material suitable for the invention can be one or more than one mixed powder of atomized iron powder, carbonyl iron powder, reduced iron powder, iron-silicon soft magnetic series powder, iron-silicon-chromium soft magnetic series powder, permalloy soft magnetic alloy powder and amorphous soft magnetic metal powder. And selecting materials and then carrying out insulation coating treatment on the materials.
First, the surface of the metal soft magnetic powder is modified so as to form an insulating thin film on the surface, the main component of the thin film may be one or more of phosphate, silicate, borate, chromate, permanganate, nitrate, aluminate, and the like, and the treatment method may be a chemical conversion method or a physical coating method depending on whether or not the insulating layer and the surface of the metal powder are chemically reacted. The insulating layer is a covalent bond or an ionic bond compound, so the insulating layer has good insulating property and heat-resistant property so as to meet the requirements of heat aging resistance and voltage breakdown resistance in the use process of the molded inductor, and the thickness of the insulating layer film prepared by the method is less than or equal to 50 nanometers.
Next, the soft magnetic metal powder having the insulating layer and the polymer binder resin are granulated. The resin must be uniformly mixed with the insulated soft magnetic metal powder by means of a corresponding diluent under the condition of sufficient fluidity, then the resin is made into a granulated powder with a certain agglomerated particle size by a granulation method, and the diluent in a binder is completely removed, so that the prepared granulated powder has fluidity and a certain bulk density, and the binder accounts for 2.0-4.0% by weight of the soft magnetic metal powder. The adhesive body may be one or more of epoxy resin, phenolic resin, silicone resin, and the like, and one or more of modified products of the above resins. The granulation method may be one of extrusion granulation, disc granulation, spray granulation, and the like. The granulated powder of the present invention has a bulk density of 2.2g/cm3 or more.
And secondly, manufacturing the coil winding. The winding coil is one of round, square and rectangular, and the material is pure copper; in addition, an iron core center post matched with the coil in shape is placed in the center of the coil, the height of the iron core center post is more than or equal to the height of the coil winding and less than or equal to 80% of the height of the corresponding molding inductance, the compression fracture strength of the iron core is more than or equal to 10MPa, the deformation is 0.1% -1.0%, the iron core material can be granulated powder related to the step one, and can also be a magnetic powder core prepared from metal powder related to the step one, such as an iron-silicon magnetic powder core, an amorphous magnetic powder core, an iron-silicon-aluminum magnetic powder core and the like; in addition, when the iron core is prepared by adopting the granulating powder related to the step one, the molding pressure is between 400 and 1500MPa, the higher the pressure is, the higher the magnetic conductivity is, and the higher the strength and the density are, and the iron core can be cured as required after molding;
thirdly, at the coilCoating magnetic powder glue on the layer of enameled wire at the outermost edge of the winding, wherein the magnetic powder glue is generally formed by mixing flowable resin and magnetic powder and is commercially available; the coating thickness is 3.0-15.0um, and the volume average particle size D50 of the soft magnetic powder in the magnetic powder adhesive is 1.0-5.0um, the magnetic powder adhesive has relative initial permeability u0And between 5.0 and 12.0, the high polymer material in the magnetic powder glue is thermosetting resin and is in a flowable liquid state at normal temperature.
Fourthly, finally, molding the soft magnetic metal granulated powder and the coil winding with the center post in a molding machine and a corresponding mold, wherein the molding process comprises the following steps: (1) the method comprises the steps of (1) feeding powder into a mold cavity for the first time by using a material shoe, (2) placing a coil winding into the mold cavity, enabling the coil to be uniform in distance from the mold wall by fixing positions of two ends of an electrode of the coil, closing the mold to form a mold cavity, (3) filling a certain amount of granulated powder into the mold cavity again, compacting the granulated powder by using a pneumatic valve to ensure that the coil is completely embedded by the granulated powder, (4) starting pressing, simultaneously molding the granulated powder and the coil winding into a mold pressing inductance by using a punch to apply pressure, wherein the coil winding is arranged inside the mold cavity, an iron core is formed by compacting the granulated powder outside the mold cavity, the molding pressure is generally between 250 and 650MPa, preferably the molding pressure is generally between 300 and 600MPa, the pressure holding time is between 0.5 and 5.0 seconds, particularly, the ratio of the plastic deformation strength of the soft magnetic metal powder to the molding pressure of the mold pressing inductance must be greater than or equal to 0.33 and, and ensuring that the ratio of the apparent density of the granulated powder to the density of the iron core after die pressing is more than or equal to 1.0/2.8, preferably more than or equal to 1.0/2.5, demoulding, opening the die cavity, then releasing the punch and ejecting the product out of the lower punch.
And fifthly, curing the molded inductor. And (3) putting the pressed molded inductor into a drying oven for binder curing treatment at 80-200 ℃, keeping the temperature for 10-300 minutes in atmosphere or protective atmosphere, so as to ensure that the binder is not oxidized while being cured completely.
Drawings
Fig. 1 is a schematic diagram of the structure of a coil winding of the present invention.
Fig. 2 is a schematic diagram of a molded inductive product of the invention.
Example 1
Embodiment 1 describes a method for preparing a high-reliability molded inductor and an inductor thereof:
1. prefabricated center pillar iron core
Firstly, placing iron core soft magnetic metal granulation powder into a mould for forming, wherein the forming pressure is 600MPa, and the shapes of the iron core soft magnetic metal granulation powder are respectively a center-pillar-free shape, a cylindrical shape, a square shape and an oval shape; the granulated powder raw powder is Fe with D50=10um92Cr4.5Si3.5The water atomized metal powder of (2) is passivated and insulated to be coated to be made into moldable granulated powder, and the magnetic conductivity of the iron core is 30.
2. Manufacture of coil winding
The center column iron core is arranged in the center of the winding and is symmetrical up and down, and the center column is ensured not to fall off under the action of no external force.
3. Protection of the outer edge of a coil winding
Example 1 no coating of magnetic flux was performed.
4. Manufacture of granulated powder for die-pressing inductor
According to the epoxy resin and the curing agent thereof: the mass ratio of the iron-based metal powder is 0.03: 1, preparing materials, namely diluting epoxy resin and a curing agent thereof into a resin mixed solution with the concentration of 25% by using a diluent, then adding the soft magnetic metal powder subjected to the two surface treatments into the mixed solution for mechanical stirring, uniformly mixing, then partially volatilizing the diluent in an air exhaust mode for granulation, drying and removing the granulated powder containing part of the diluent at the temperature of between 60 and 80 ℃ to obtain completely dried soft magnetic metal granulated powder, and performing size stabilization and screening treatment as required to obtain the granulated powder with the apparent density of 2.2.
5. Inductance compression molding forming
And pressing the die pressing inductor in a die, wherein the sample adopts an initial inductance value of 10uH, an external dimension of 6.6mm 3mm, and a die pressing pressure of 500MPa, firstly, powder is filled for the first time, then, the coil provided with the prefabricated iron core is placed into a die cavity, then, powder is filled for the second time, then, the die cavity is closed, the die pressing molding is started, the molded product is demoulded, and then, the binder is cured for 90 minutes at 160 ℃ to obtain the usable die pressing inductor.
And then testing the direct current withstand voltage of the product, the deformation of the coil sectional area and the basic magnetic property of the product.
The following table shows the test results: when the central column is round, square or elliptical, the deformation of the coil is obviously reduced and the voltage resistance is obviously improved.
Example 2
Embodiment 2 describes a method for manufacturing a high-reliability molded inductor and an inductor thereof:
1. prefabricated center pillar iron core
Firstly, placing iron core soft magnetic metal granulation powder into a mould for forming, wherein the forming pressure is 600MPa, and the shapes of the iron core soft magnetic metal granulation powder and the iron core soft magnetic metal granulation powder are respectively cylindrical; the granulated powder raw powder is Fe with D50=10um92Cr4.5Si3.5The water atomized metal powder of (2) is passivated and insulated to be coated to be made into moldable granulated powder, and the magnetic conductivity of the iron core is 30.
2. Manufacture of coil winding
The center column iron core is arranged in the center of the winding and is symmetrical up and down, and the center column is ensured not to fall off under the action of no external force.
3. Protection of the outer edge of a coil winding
The outside of coil winding is whole to be coated with magnetic powder glue, and this protective layer thickness is 1um, 2um, 3um, 5um, 10um respectively, later will coat the coil that has magnetic powder glue and toast 60 minutes with 80 ℃ in the drying cabinet.
4. Manufacture of granulated powder for die-pressing inductor
According to the epoxy resin and the curing agent thereof: the mass ratio of the iron-based metal powder is 0.03: 1, preparing materials, namely diluting epoxy resin and a curing agent thereof into a resin mixed solution with the concentration of 25% by using a diluent, then adding the soft magnetic metal powder subjected to the two surface treatments into the mixed solution for mechanical stirring, uniformly mixing, then partially volatilizing the diluent in an air exhaust mode for granulation, drying and removing the granulated powder containing part of the diluent at the temperature of between 60 and 80 ℃ to obtain completely dried soft magnetic metal granulated powder, and performing size stabilization and screening treatment as required to obtain the granulated powder with the apparent density of 2.2.
5. Inductance compression molding forming
And pressing the die pressing inductor in a die, wherein the sample adopts an initial inductance value of 10uH, an external dimension of 6.6mm 3mm, and a die pressing pressure of 500MPa, firstly, powder is filled for the first time, then, the coil provided with the prefabricated iron core is placed into a die cavity, then, powder is filled for the second time, then, the die cavity is closed, the die pressing molding is started, the molded product is demoulded, and then, the binder is cured for 90 minutes at 160 ℃ to obtain the usable die pressing inductor.
And then testing the direct current withstand voltage of the product, the deformation of the coil sectional area and the basic magnetic property of the product.
The following table shows the test results: along with the increase of the thickness of the coil coating layer, the direct-current withstand voltage is not obviously changed after being increased, the inductance value is in a continuous reduction trend, and the deformation of the coil is not obviously changed basically.
Example 3
Embodiment 3 describes a method for manufacturing a high-reliability molded inductor and an inductor thereof:
1. prefabricated center pillar iron core
Firstly, placing iron core soft magnetic metal granulation powder into a mould for forming, wherein the forming pressure is 600MPa, and the shapes of the iron core soft magnetic metal granulation powder and the iron core soft magnetic metal granulation powder are respectively cylindrical; the granulated powder raw powder is Fe with D50=10um92Cr4.5Si3.5The water atomized metal powder of (2) is passivated and insulated to be coated to be made into moldable granulated powder, and the magnetic conductivity of the iron core is 30.
2. Manufacture of coil winding
The center column iron core is arranged in the center of the winding and is symmetrical up and down, and the center column is ensured not to fall off under the action of no external force.
3. Protection of the outer edge of a coil winding
The outside of the coil winding was entirely coated with magnetic flux of 3um in thickness, and then the coil coated with magnetic flux was baked in a drying oven at 80 ℃ for 60 minutes.
4. Manufacture of granulated powder for die-pressing inductor
According to the epoxy resin and the curing agent thereof: the mass ratio of the iron-based metal powder is 0.03: 1, preparing materials, namely diluting epoxy resin and a curing agent thereof into a resin mixed solution with the concentration of 25% by using a diluent, then adding the soft magnetic metal powder subjected to the two surface treatments into the mixed solution for mechanical stirring, uniformly mixing, then partially volatilizing and granulating the diluent in an air exhaust mode, drying and removing the granulated powder containing part of the diluent at the temperature of between 60 and 80 ℃ to obtain completely dried soft magnetic metal granulated powder, carrying out size stabilization and screening treatment, and screening to obtain powder with the granularity of-60 to 180 meshes, wherein the loose packing densities of the obtained granulated powder are respectively 2.2, 2.3 and 2.4.
5. Inductance compression molding forming
And pressing the die pressing inductor in a die, wherein the sample adopts an initial inductance value of 10uH, an external dimension of 6.6mm 3mm, and a die pressing pressure of 500MPa, firstly, powder is filled for the first time, then, the coil provided with the prefabricated iron core is placed into a die cavity, then, powder is filled for the second time, then, the die cavity is closed, the die pressing molding is started, the molded product is demoulded, and then, the binder is cured for 90 minutes at 160 ℃ to obtain the usable die pressing inductor.
And then testing the direct current withstand voltage of the product, the deformation of the coil sectional area and the basic magnetic property of the product.
The following table shows the test results: as the bulk density of the granulated powder is increased, the direct-current withstand voltage, the inductance and the direct-current bias characteristic are not obviously changed, and only the deformation inductance of the coil section is in a continuous reduction trend.
Example 4
Embodiment 4 describes a method for manufacturing a high-reliability molded inductor and an inductor thereof:
1. prefabricated center pillar iron core
Firstly, placing iron core soft magnetic metal granulation powder into a mould for forming, wherein the forming pressure is 600MPa, and the shapes of the iron core soft magnetic metal granulation powder and the iron core soft magnetic metal granulation powder are respectively cylindrical; the raw powder of the granulated powder is carbonyl iron metal powder with D50=5um, and is made into moldable granulated powder after passivation and insulation coating, and the magnetic permeability of the iron core is 28.
2. Manufacture of coil winding
The center column iron core is arranged in the center of the winding and is symmetrical up and down, and the center column is ensured not to fall off under the action of no external force.
3. Protection of the outer edge of a coil winding
The outside of the coil winding was entirely coated with magnetic flux of 3um in thickness, and then the coil coated with magnetic flux was baked in a drying oven at 80 ℃ for 60 minutes.
4. Manufacture of granulated powder for die-pressing inductor
According to the epoxy resin and the curing agent thereof: the mass ratio of the iron-based metal powder is 0.03: 1, preparing materials, namely diluting epoxy resin and a curing agent thereof into a resin mixed solution with the concentration of 25% by using a diluent, then adding the soft magnetic metal powder subjected to the two surface treatments into the mixed solution for mechanical stirring, uniformly mixing, then partially volatilizing and granulating the diluent by using an air exhaust mode, drying and removing the granulated powder containing part of the diluent at the temperature of between 60 and 80 ℃, thus obtaining completely dried soft magnetic metal granulated powder, and carrying out particle finishing and screening treatment, wherein the apparent density of the obtained granulated powder is 2.2 respectively.
5. Inductance compression molding forming
And pressing the die pressing inductor in a die, wherein the sample adopts an initial inductance value of 10uH, the external dimension of 6.6mm 3mm, and the die pressing pressure is 400MPa and 500MPa respectively, firstly, performing primary powder filling, then placing the coil provided with the prefabricated iron core into a die cavity, then performing secondary powder filling, closing the die cavity, starting press forming, demolding the formed product, and then treating at 160 ℃ for 90 minutes to solidify the binder and obtain the usable die pressing inductor.
And then testing the direct current withstand voltage of the product, the deformation of the coil sectional area and the basic magnetic property of the product.
The following table shows the test results: the yield strength of the pure iron is about 200MPa, the direct-current withstand voltage and the inductance value are not obviously changed along with the increase of the pressing pressure, the direct-current bias characteristic is obviously improved, and the deformation inductance value of the coil section is in a continuous reduction trend.
Example 5
Embodiment 5 describes a method for preparing a high-reliability molded inductor and an inductor thereof:
1. prefabricated center pillar iron core
Firstly, placing iron core soft magnetic metal granulation powder into a mould for forming, wherein the forming pressure is 600MPa, and the shapes of the iron core soft magnetic metal granulation powder and the iron core soft magnetic metal granulation powder are respectively cylindrical; the raw powder of the granulated powder is carbonyl iron metal powder with D50=5um, and is made into moldable granulated powder after passivation and insulation coating, and the magnetic permeability of the iron core is 28.
2. Manufacture of coil winding
The center column iron core is arranged in the center of the winding and is symmetrical up and down, and the center column is ensured not to fall off under the action of no external force.
3. Protection of the outer edge of a coil winding
The outside of the coil winding was entirely coated with magnetic flux of 3um in thickness, and then the coil coated with magnetic flux was baked in a drying oven at 80 ℃ for 60 minutes.
4. Manufacture of granulated powder for die-pressing inductor
According to the epoxy resin and the curing agent thereof: the mass ratio of the iron-based metal powder is 0.03: 1, preparing materials, namely diluting epoxy resin and a curing agent thereof into a resin mixed solution with the concentration of 25% by using a diluent, then adding the soft magnetic metal powder subjected to the two surface treatments into the mixed solution for mechanical stirring, uniformly mixing, then partially volatilizing and granulating the diluent by using an air exhaust mode, drying and removing the granulated powder containing part of the diluent at the temperature of between 60 and 80 ℃, thus obtaining completely dried soft magnetic metal granulated powder, and carrying out particle finishing and screening treatment, wherein the apparent density of the obtained granulated powder is 2.2 respectively.
5. Inductance compression molding forming
And pressing the molded inductor in a mold, wherein the mold is heated to 150 ℃, the sample adopts an initial inductance value of 10uH, an external dimension of 6.6mm 3mm and a molding pressure of 250MPa, the first powder filling is carried out, then the coil provided with the prefabricated iron core is placed into a cavity, then the second powder filling is carried out, then the cavity is closed, the compression molding is started, the molded product is demoulded, and then the treatment at 160 ℃ is carried out for 90 minutes to solidify the binder and obtain the usable molded inductor.
And then testing the direct current withstand voltage of the product, the deformation of the coil sectional area and the basic magnetic property of the product.
The following table shows the test results: the yield strength of pure iron is about 200MPa, the direct-current withstand voltage is obviously improved along with the increase of the pressing pressure, the direct-current bias characteristic is obviously improved, and the deformation inductance value of the coil section is in a continuous reduction trend.
Claims (7)
1. A preparation method of a high-reliability molded inductor and the inductor thereof are characterized in that: (1) the invention adopts granulated powder composed of soft magnetic metal powder and high molecular binder as the iron core base material, the ratio of the loose packed density of the granulated powder to the density of the iron core after mould pressing is more than or equal to 1/2.8, and the loose packed density of the granulated powder is more than or equal to 2.2g/cm3(2) copper coil winding as the conductive material for generating magnetic field, the copper coil winding center is preset with one of the cylindrical, T-shaped and I-shaped iron core, and the iron core main material is iron-based soft magnetic metal powder, the compression fracture strength of the iron core is more than or equal to 10MPa, the deformation is between 0.1% -1.0%, the outer edge of the coil winding is coated with a layer of magnetic powder glue which is enough to fill the gully between the copper wires, and the film thickness between the magnetic powder glue and the outer edge of the coil is more than or equal to 3.0um, (3) then the granulated powder and the coil winding are molded into molding inductance in a mold, and the soft magnetic powder and the coil winding are molded into molding inductancePlastic deformation strength sigma of magnetic metal powder0.2The ratio of the molding pressure to the molding pressure of the molded inductor is required to be more than or equal to 0.33 and less than 0.80, the molding pressure is less than or equal to 600MPa, and (4) the deformation of the cross section of the molded inductor coil prepared by the method is reduced by 50 percent or more, and the direct-current voltage resistance between a molded inductor terminal and an iron core is up to the direct-current voltage resistance>And (5) =1000V/cm or more.
2. The method for preparing high-reliability molded inductor and the inductor thereof as claimed in claim 1, wherein the method comprises the following steps: the iron core base material for the molded inductor can be carbonyl iron powder, reduced iron powder, atomized iron powder and atomized Fe(100-x-y)SixCryPowder (x =3.5-6.5, y = 0.0-6.5), iron-based amorphous soft magnetic powder, iron-based amorphous nanocrystalline powder, Sandust powder, HighFlux powder, or a mixture of more than one of them, and the volume average particle size D50 is 5.0-15.0 um.
3. The method for preparing high-reliability molded inductor and the inductor thereof as claimed in claim 1, wherein the method comprises the following steps: the high molecular material for granulation can be epoxy resin series, phenolic resin series, silicon resin series and other resins and related modified substances thereof, the addition amount of the binder is 2.0-4.0% of the weight of the metal powder, and related diluents, coupling agents, toughening agents, defoaming agents and leveling agents can be added to assist in forming granulated powder and improve corresponding characteristics, and the particle size range of the granulated powder is-50 meshes to +300 meshes.
4. The method for preparing high-reliability molded inductor and the inductor thereof as claimed in claim 1, wherein the method comprises the following steps: the ratio of the apparent density of the granulated powder to the density of the iron core after molding is 1.0/2.8 or more, and the apparent density of the granulated powder is 2.2g/cm or more3Preferably, the ratio of the apparent density of the granulated powder to the density of the iron core after molding is 1.0/2.5 or more.
5. The method for preparing a high-reliability molded inductor according to claim 1,the method is characterized in that: the iron core preset at the center of the copper coil winding is one of a cylindrical iron core, a T-shaped iron core and an I-shaped iron core, the preset iron core height is less than or equal to 80% of the total height of the molded inductor, the diameter of the preset iron core is 97.6-99.6% of the inner diameter of the coil, and the soft magnetic material for the preset iron core can be carbonyl iron powder, reduced iron powder, atomized iron powder and atomized Fe(100-x-y)SixCryPowder (x =3.5-6.5, y = 0.0-6.5), iron-based amorphous soft magnetic powder, iron-based amorphous nanocrystalline powder, Sandust powder, and HighFlux powder, and the pre-arranged iron core has a density of 5.5-7.0g/cm3The compression fracture strength of the preset iron core is more than or equal to 10MPa, and the deformation is between 0.1 and 1.0 percent.
6. The method for preparing high-reliability molded inductor and the inductor thereof as claimed in claim 1, wherein the method comprises the following steps: the outer edge of the coil winding is coated with a layer of magnetic powder glue which is enough to fill and level up the gullies between the copper wires, the thickness of a film between the magnetic powder glue and the outer edge of the coil is more than or equal to 3.0um, in addition, the volume average particle size D50 of the soft magnetic powder in the magnetic powder glue is between 1.0 and 5.0um, and the relative initial permeability u of the magnetic powder glue is0And between 5.0 and 12.0, the high polymer material in the magnetic powder glue is thermosetting resin and is in a flowable liquid state at normal temperature.
7. The method for preparing high-reliability molded inductor and the inductor thereof as claimed in claim 1, wherein the method comprises the following steps: the molding inductor is formed by granulating powder and coil winding in a mold, and generally comprises powder pressing processes of coil arrangement, mold assembly, powder feeding, pressing, demolding and the like, wherein the plastic deformation strength sigma of the soft magnetic metal powder0.2The ratio of the molding pressure to the molding pressure of the molding inductor must be 0.33 or more and less than 0.80, preferably 0.40 or more and less than 0.80, and the molding pressure must be 600MPa or less.
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