Thermosetting packaging integrated inductor and manufacturing method thereof

Abstract

The invention discloses a thermosetting packaging integrated inductor and a manufacturing method thereof, and belongs to the technical field of inductors.The inductor comprises a low-conductivity anti-eddy-current magnetic core, an inductance coil and a heat conduction type thermosetting polymer packaging material, and the heat conduction type thermosetting polymer packaging material integrally packages the low-conductivity anti-eddy-current magnetic core and the inductance coil; the heat conduction type thermosetting polymer packaging material has electrical insulation performance and heat conduction performance, and the low-conductivity eddy-current-resistant magnetic core is formed by pressing high-permeability mixed crystal phase alloy powder wrapped with a silicon dioxide film. The thickness of the silica film is controlled to be 50 [mu] m or less and 20 [mu] m or more. By adopting the heat conduction type thermosetting polymer packaging material, the heat conductivity of the inductor is effectively improved, compared with a traditional inductor, the heat conductivity coefficient is improved by 40% or above, the magnetic core loss is reduced by 30% or above, the heat influence of the inductor on surrounding elements in the working process is reduced, and the heat stability of a whole circuit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inductors, and more particularly to a thermosetting encapsulated integrated inductor and a manufacturing method thereof. Background Art

[0002] An inductor is an electronic component that works based on the principle of electromagnetic induction. It can convert electrical energy into magnetic energy and store it. When an alternating current passes through the inductor, the magnetic field generated by the current changes. According to Faraday's law of electromagnetic induction, this change in the magnetic field will generate a reverse electromotive force in the coil, thereby hindering the change in current. Conversely, when the current decreases, the inductor will generate an electromotive force in the direction of increasing current, hindering the decrease in current. This property of the inductor makes the current change in the circuit smoother, can weaken the sharp change in current at the moment of switching, and plays functions such as signal screening, noise filtering, current stabilization, and suppression of electromagnetic wave interference.

[0003] The integrated inductors in the prior art have the following defects: First, the traditional alloy magnetic powder core material has a low resistivity, large eddy currents at high frequencies, and serious heating. Second, the encapsulation material of the integrated inductor usually uses modified epoxy resin, which has a low thermal conductivity and poor heat conduction performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a thermosetting encapsulated integrated inductor and a manufacturing method thereof. Under the barrier of the silicon dioxide film, the generated induced current is prevented from forming eddy currents in the magnetic core, greatly reducing the heat energy generated by the magnetic core and greatly reducing the eddy current loss at high frequencies.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: A thermosetting encapsulated integrated inductor includes a low-conductance eddy current magnetic core, an inductor coil, and a thermally conductive thermosetting polymer encapsulation material. The thermally conductive thermosetting polymer encapsulation material integrally encapsulates the low-conductance eddy current magnetic core and the inductor coil. The thermally conductive thermosetting polymer encapsulation material has electrical insulation performance and heat conduction performance. The low-conductance eddy current magnetic core is made of high-permeability mixed crystal phase alloy powder wrapped with a silicon dioxide film, and has the characteristics of low thermal conductivity and high insulation impedance. The film thickness of the silicon dioxide film is controlled to be less than 50 μm and more than 20 μm.

[0006] Further, the high-permeability mixed crystal phase alloy powder is represented by the composition formula FeaNibCocPdCue, where 70 ≤ a ≤ 80 at%, 10 ≤ b ≤ 20 at%, 1 ≤ c ≤ 3 at%, 6 ≤ d ≤ 8 at%, 0.4 ≤ e ≤ 0.6 at% and a + b + c + d + e = 100 at%. The high-permeability mixed crystal phase alloy powder is composed of 82 - 88% amorphous phase and 12 - 18% crystalline phase by volume.

[0007] Furthermore, the thermally conductive thermosetting polymer encapsulation material is composed of polyimide resin, alumina micropowder, and boron nitride micropowder. The mass percentage content of polyimide resin is 80 - 90%, the mass percentage content of alumina micropowder is 6 - 12%, and the mass percentage content of boron nitride micropowder is 4 - 8%.

[0008] Furthermore, the preparation method of the low - conductivity eddy - current - resistant magnetic core is as follows: Step 1. Weigh each component in the composition formula FeaNibCocPdCue according to the ratio of 70 ≤ a ≤ 80 at%, 10 ≤ b ≤ 20 at%, 1 ≤ c ≤ 3 at%, 6 ≤ d ≤ 8 at%, 0.4 ≤ e ≤ 0.6 at% and a + b + c + d + e = 100 at%, mix them evenly, and without adding a binder, press them into a block. After the first heat treatment, perform a grinding process to obtain a high - permeability crystalline alloy powder; Step 2. Coat a silica film on the surface of the high - permeability crystalline alloy powder: The specific steps for coating the silica film are as follows: Disperse the high - permeability crystalline alloy powder in an ethanol - aqueous solution, add a catalyst and continuously stir, disperse by ultrasonic wave for 10 - 20 min, then use a peristaltic pump to drop - add tetraethyl orthosilicate. The dropping speed of tetraethyl orthosilicate is 20 - 30 rpm. After continuously stirring and ultrasonicating until the dropping is completed, keep ultrasonicating for 6 - 8 min and then turn off the ultrasonic wave. Continuously stir to make it react for 7 - 9 h, and after drying, obtain the high - permeability crystalline alloy powder coated with a silica film; Step 3. Place the high - permeability crystalline alloy powder into a low - conductivity eddy - current - resistant magnetic core forming mold, and without adding a binder, press it into a magnetic core blank; Step 4. Perform the second heat treatment and annealing treatment: Perform the second heat treatment on the magnetic core blank in an inert gas environment, and then perform the annealing treatment to obtain a low - conductivity eddy - current - resistant magnetic core.

[0009] Furthermore, in the above - mentioned Step 1, the temperature of the first heat treatment is 420 - 440 °C.

[0010] Furthermore, in the above - mentioned Step 2, the catalyst is ammonia water or tetramethylammonium hydroxide.

[0011] Furthermore, in the above - mentioned Step 3, the pressure used for pressing is 2.1 - 2.3 GPa.

[0012] Furthermore, in the above - mentioned Step 4, the temperature of the second heat treatment is 580 - 600 °C, the temperature of the annealing treatment is 280 - 300 °C, and the annealing time is 1.5 - 2 hours.

[0013] A manufacturing method of a thermosetting encapsulation integrated inductor includes the following steps: S1. According to the mass percentage content of 80-90%, 6-12%, and 4-8%, polyimide resin particles, aluminum oxide powder and boron nitride powder are weighed in sequence and mixed thoroughly to obtain a thermally conductive thermosetting polymer encapsulation material; S2. heating and melting the thermally conductive thermosetting polymer encapsulation material; S3. The prepared low-impedance eddy current magnetic core is a columnar structure, and slots are provided at both ends of the low-impedance eddy current magnetic core of the columnar structure. A layer of heat-conductive thermosetting polymer packaging material is coated on the ends of the two copper electrode sheets and then inserted into the slots at both ends of the low-impedance eddy current magnetic core. The wound inductor coil is placed and inserted on the low-impedance eddy current magnetic core and adjusted to a predetermined position. The two leads of the inductor coil are respectively welded to the two copper electrode sheets, and the low-impedance eddy current magnetic core and the inductor coil are placed together in the lower mold of the plastic packaging mold. The copper electrode sheets extend from both ends of the plastic packaging mold. The two ends of the low-impedance eddy current magnetic core are supported by the copper electrode sheets. A predetermined gap is retained between the low-impedance eddy current magnetic core and the inner wall of the plastic packaging mold. The upper mold and the lower mold in the plastic packaging mold are tightly buckled together; S4. The plastic mold is evacuated, and the heated and melted thermal conductive thermosetting polymer encapsulation material is filled into the mold cavity of the plastic mold, the filling encapsulation pressure is 8-10MPa, and the temperature is 260 - 400 ℃; S5. After the filling and packaging is completed, a curing treatment is performed with a curing temperature of 130-180°C and a curing time of 1.5-2 hours, so that the thermally conductive thermosetting polymer packaging material is completely cured and tightly combined with the low-impedance eddy current core and the inductor coil to form an integrally molded packaged inductor.

[0014] Furthermore, the vacuum degree of the plastic encapsulation mold is maintained in the range of 0.9-1 MPa.

[0015] The beneficial effects of the present invention are: The thermosetting packaged integrated inductor of the present application greatly reduces eddy current losses under high frequencies: the inductor core adopts a low-conductivity eddy current core with low thermal conductivity characteristics and high insulation impedance characteristics. Under the barrier of the silicon dioxide film, the generated induced current is prevented from forming eddy currents in the core, which greatly reduces the heat energy generated by the core and greatly reduces the eddy current losses under high frequencies.

[0016] The thermosetting encapsulated integrated inductor of the present application has better electrical insulation and thermal conductivity: by adopting thermally conductive thermosetting polymer encapsulation materials, the thermal conductivity of the inductor is effectively improved. Compared with traditional inductors, the thermal conductivity coefficient is increased by more than 40%, and the core loss is reduced by more than 30%, which reduces the thermal impact of the inductor on surrounding components during operation and improves the thermal stability of the entire circuit.

[0017] The manufacturing process of the thermosetting encapsulated integrated inductor of the present application is simplified and the cost is reduced: by casting encapsulation, the production processes and the number of components are greatly reduced, the production efficiency is improved, and the production cost is reduced. Compared with the traditional inductor manufacturing process, the production efficiency is increased by more than 30%, and the cost is reduced by more than 10%. Description of the Drawings

[0018] The present invention will be further described with reference to the accompanying drawings. However, the embodiments in the drawings do not constitute any limitation to the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the following drawings: Figure 1 It is a schematic structural diagram of the thermosetting encapsulated integrated inductor of the present invention.

[0019] In the figure: 1, low-permeability eddy current magnetic core; 2, inductor coil; 3, thermally conductive thermosetting polymer encapsulation material; 4, copper electrode sheet; 5, slot; 6, lead wire. Detailed Embodiments

[0020] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper surface", "lower surface", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "forward rotation", "reverse rotation", "axial direction", "radial direction", "circumferential direction", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0022] As Figure 1 shown, a thermosetting encapsulated integrated inductor includes a low-permeability eddy current magnetic core 1, an inductor coil 2, and a thermally conductive thermosetting polymer encapsulation material 3. The ends of two copper electrode sheets 4 are coated with a layer of thermally conductive thermosetting polymer encapsulation material and then inserted into the slots 5 at both ends of the low-permeability eddy current magnetic core 1. The two lead wires 6 of the inductor coil 2 are respectively welded to the two copper electrode sheets 4, and the thermally conductive thermosetting polymer encapsulation material 3 integrally encapsulates the low-permeability eddy current magnetic core 1 and the inductor coil 2.

[0023] The low-permeance eddy-current magnetic core 1 is made of high-permeability mixed-crystalline-phase alloy powder wrapped with a silica film, and has the characteristics of low thermal conductivity and high insulation impedance. The high-permeability mixed-crystalline-phase alloy powder is represented by the composition formula FeaNibCocPdCue, where 70≤a≤80at%, 10≤b≤20at%, 1≤c≤3at%, 6≤d≤8at%, 0.4≤e≤0.6at% and a + b + c + d + e = 100at%. The high-permeability mixed-crystalline-phase alloy powder is composed of 82 - 88% amorphous phase and 12 - 18% crystalline phase by volume. The film thickness of the silica film is controlled below 50μm and above 20μm. The film thickness of the silica film will have a certain impact on the permeability. Therefore, the film thickness of the silica film should be controlled below 50μm. In order to ensure the characteristics of high insulation impedance and reduce the eddy-current loss of the magnetic core, the film thickness of the silica film should be adjusted above 20μm.

[0024] A silica film is wrapped on the surface of the high-permeability mixed-crystalline-phase alloy powder. The silica film has good electrical insulation, which can prevent the induced current from forming eddy currents in the magnetic core, greatly reducing the heat energy generated by the magnetic core and greatly reducing the eddy-current loss at high frequencies. However, due to the low permeability of the silica film, it is necessary to improve the material of the magnetic core 1 to maximize the permeability and increase the magnetic flux. In the Fe-based material, increasing the content of Ni can increase the permeability. However, increasing the content of Ni element will increase the manufacturing cost. Therefore, the high-permeability mixed-crystalline-phase alloy powder in the low-permeance eddy-current magnetic core 1 of this application adopts the above composition formula FeaNibCocPdCue. Among them, in order to improve the permeability of the magnetic core as much as possible, the content of Ni element is adjusted above 10at%. In order to reduce the cost, the content of Ni element is adjusted below 20at%, and an appropriate amount of Co element is added at the same time.

[0025] The P element is a necessary element for the formation of the amorphous phase. The high-permeability mixed-crystalline-phase alloy powder with 82 - 88% amorphous phase has a very high permeability. In this embodiment, the P element is added to the magnetic core material, and the proportion of the P element is adjusted within the range of 6≤d≤8at%. Specifically, when the proportion of the P element is greater than 6at%, it can significantly reduce the viscosity of the alloy molten metal when manufacturing magnetic powder, so as to improve the magnetic properties of the powder-compressed magnetic core, and it becomes easier to manufacture spherical magnetic powder. In particular, the melting point of the P element is 44.1℃. The low-melting-point P element can improve the ability to generate the amorphous state, and it becomes easier to manufacture Fe-based crystalline alloy powder. In order to obtain the required saturation magnetic flux density Bs in the Fe-based nanocrystalline alloy powder, the proportion of P is adjusted below 8at%. When the proportion of the P element is 7at% under the condition that the proportions of other elements in the low-permeance eddy-current magnetic core 1 remain unchanged, it has excellent saturation magnetic flux density Bs and excellent magnetic properties.

[0026] In the present embodiment, the Cu element is added to the magnetic core material, and preferably the proportion of the Cu element is adjusted to be above 0.4at% and below 0.6at%. Within this proportion range, the effect of refining the crystals in the Fe-based crystalline alloy powder can be obtained, and the amorphous forming ability can be improved. As a result, the degradation of the magnetic properties of the Fe-based crystalline alloy powder caused by the previous precipitates can be suppressed. Specifically, in order to prevent the coarsening of nanocrystals in the Fe-based crystalline alloy powder, thereby causing core loss, the proportion of Cu should be set to be above 0.4at%, and in order to improve the ability to generate amorphous forms, the crystalline phase in the high permeability mixed crystal phase alloy powder is controlled to be below 18%, and the proportion of Cu is adjusted to be below 0.6at%. In addition, in order to increase the amount of crystal precipitation and increase the saturation magnetic flux density Bs of the Fe-based crystalline alloy powder, the proportion of Cu is preferably 0.5at%.

[0027] After adopting the above-mentioned high permeability mixed crystal phase alloy powder, the present application maximizes the permeability while controlling the manufacturing cost to compensate for the influence of the silicon dioxide film on the magnetic flux of the magnetic core, thereby ensuring the required permeability of the magnetic core while suppressing the eddy current loss and heat generation of the magnetic core.

[0028] The packaging of the present application uses a heat-conducting thermosetting polymer packaging material, which has electrical insulation and thermal conductivity. The heat-conducting thermosetting polymer packaging material is a mixture of polyimide resin, aluminum oxide micropowder and boron nitride micropowder, wherein the mass percentage of the polyimide resin is 80-90%, the mass percentage of the aluminum oxide micropowder is 6-12%, and the mass percentage of the boron nitride micropowder is 4-8%. Aluminum oxide micropowder and boron nitride micropowder can not only improve the insulation performance of the packaging material, but also greatly improve the thermal conductivity of the packaging material, so that the inductor can work normally and stably under high-frequency conditions.

[0029] Example 1 A method for manufacturing a thermosetting packaged integrated inductor comprises the following steps: S1. Weigh polyimide resin particles, aluminum oxide powder and boron nitride powder in order according to the mass percentage contents of 80%, 12% and 8%, and mix them thoroughly to obtain a thermally conductive thermosetting polymer packaging material.

[0030] S2. Heat and melt the heat-conductive thermosetting polymer packaging material.

[0031] S3. The prepared low-inductance eddy-current magnetic core is in a columnar structure, with slots provided at both ends of the columnar low-inductance eddy-current magnetic core. Coat the ends of two copper electrode plates with a heat-conductive thermosetting polymer encapsulation material and then insert them into the slots at both ends of the low-inductance eddy-current magnetic core. Place the wound inductor coil on and intersperse it with the low-inductance eddy-current magnetic core and adjust it to a predetermined position. Weld the two leads of the inductor coil to the two copper electrode plates respectively. Place the low-inductance eddy-current magnetic core and the inductor coil together in the lower mold of the plastic encapsulation mold. The copper electrode plates extend from both ends of the plastic encapsulation mold. The two ends of the low-inductance eddy-current magnetic core are supported by the copper electrode plates. A predetermined gap is reserved between the low-inductance eddy-current magnetic core and the inner wall of the plastic encapsulation mold. Close the upper mold and the lower mold in the plastic encapsulation mold tightly together.

[0032] The preparation method of the low-inductance eddy-current magnetic core is as follows: Step 1. Weigh each component in the composition formula FeaNibCocPdCue according to the ratio of 70at%, 20at%, 1.6at%, 8at%, 0.4at% and mix them evenly. Without adding a binder, press them into a block and conduct the first heat treatment, and then conduct a grinding treatment to obtain a high-permeability crystalline alloy powder; the temperature of the first heat treatment is 420 °C.

[0033] Step 2. Coating a silica film on the surface of the high-permeability crystalline alloy powder: The specific steps of the silica film coating are as follows: Disperse the high-permeability crystalline alloy powder in an ethanol aqueous solution, add a catalyst and stir continuously, ultrasonically disperse for 10 min, then dropwise add tetraethyl orthosilicate with a peristaltic pump. The dropping speed of tetraethyl orthosilicate is 20 rpm. Keep stirring and ultrasonically treating until the dropping is completed, then keep ultrasonically treating for 6 min and then turn off the ultrasonic treatment, and keep stirring to make it react for 7 h. After drying, obtain the high-permeability crystalline alloy powder coated with a silica film; the catalyst is ammonia water or tetramethylammonium hydroxide. The film thickness of the silica film is 50 μm.

[0034] Step 3. Place the high-permeability crystalline alloy powder into the low-inductance eddy-current magnetic core forming mold, and press it into a magnetic core blank without adding a binder; the pressure used for pressing is 2.1 GPa.

[0035] Step 4. Conduct the second heat treatment and annealing treatment: Conduct the second heat treatment on the magnetic core blank in an inert gas environment, and then conduct an annealing treatment to obtain a low-inductance eddy-current magnetic core; the temperature of the second heat treatment is 580 °C, the temperature of the annealing treatment is 280 °C, and the annealing time is 1.5 hours.

[0036] S4. Evacuate the plastic encapsulation mold, keep the vacuum degree of the plastic encapsulation mold within the range of 0.9 MPa, and fill the cavity of the plastic encapsulation mold with the heat-conductive thermosetting polymer encapsulation material after heating and melting. The filling and encapsulation pressure is 8 MPa, and the temperature is 260 °C; S5. After the filling and packaging is completed, a curing treatment is performed with a curing temperature of 130°C and a curing time of 1.5 hours, so that the thermally conductive thermosetting polymer packaging material is completely cured and tightly combined with the low-impedance eddy current core and the inductor coil to form an integrally molded packaged inductor.

[0037] Example 2 A method for manufacturing a thermosetting packaged integrated inductor comprises the following steps: S1. Weigh polyimide resin particles, aluminum oxide powder and boron nitride powder in order according to the mass percentage content of 85%, 9% and 6%, and mix them thoroughly to obtain a thermally conductive thermosetting polymer packaging material.

[0038] S2. Heat and melt the heat-conductive thermosetting polymer packaging material.

[0039] S3. The prepared low-impedance eddy-current magnetic core is a columnar structure with slots at both ends of the columnar low-impedance eddy-current magnetic core. A layer of thermally conductive thermosetting polymer packaging material is coated on the ends of the two copper electrode sheets and then inserted into the slots at both ends of the low-impedance eddy-current magnetic core. The wound inductor coil is placed and inserted on the low-impedance eddy-current magnetic core and adjusted to a predetermined position. The two leads of the inductor coil are respectively welded to the two copper electrode sheets. The low-impedance eddy-current magnetic core and the inductor coil are placed together in the lower mold of the plastic molding mold. The copper electrode sheets extend from both ends of the plastic molding mold. The two ends of the low-impedance eddy-current magnetic core are supported by the copper electrode sheets. A predetermined gap is retained between the low-impedance eddy-current magnetic core and the inner wall of the plastic molding mold. The upper mold and the lower mold in the plastic molding mold are tightly buckled together.

[0040] The preparation method of the low-impedance eddy-current magnetic core is as follows: Step 1. Weigh and mix the components in the composition formula FeaNibCocPdCue in a ratio of 80at%, 10at%, 3at%, 6.4at%, and 0.6at%, and press them into blocks without adding a binder, perform a first heat treatment, and then grind them to obtain a high permeability crystalline alloy powder; the temperature of the first heat treatment is 440°C.

[0041] Step 2. Wrapping a silicon dioxide film on the surface of the high permeability crystalline alloy powder: The specific steps of the silicon dioxide film coating are as follows: disperse the high permeability crystalline alloy powder in an ethanol aqueous solution, add a catalyst and continue to stir, disperse by ultrasound for 20 minutes, then drop tetraethyl orthosilicate with a peristaltic pump, the speed of dropping tetraethyl orthosilicate is 30rpm, continue to stir and ultrasound until the addition is completed, keep ultrasound for 8 minutes and then turn off the ultrasound, continue to stir to react for 9 hours, and dry to obtain a high permeability crystalline alloy powder wrapped with a silicon dioxide film; the catalyst is ammonia water or tetramethylammonium hydroxide. The film thickness of the silicon dioxide film is 20μm.

[0042] Step 3. Place the high magnetic permeability crystalline alloy powder into a low-conductivity eddy current magnetic core forming mold, and press it into a magnetic core blank without adding an adhesive; the pressing pressure is 2.3 GPa.

[0043] Step 4. Perform a second heat treatment and annealing treatment: perform a second heat treatment on the core blank in an inert gas environment, and then perform annealing treatment to obtain a low-impedance eddy current core; the temperature of the second heat treatment is 600°C, the temperature of the annealing treatment is 300°C, and the annealing time is 2 hours.

[0044] S4. The plastic mold is evacuated, the vacuum degree of the plastic mold is maintained within the range of 1MPa, and the heat-conductive thermosetting polymer encapsulation material after heating and melting is filled into the cavity of the plastic mold, the filling packaging pressure is 10MPa, and the temperature is 400°C; S5. After the filling and packaging is completed, a curing treatment is performed with a curing temperature of 180°C and a curing time of 2 hours, so that the thermally conductive thermosetting polymer packaging material is completely cured and tightly combined with the low-conductivity eddy current core and the inductor coil to form an integrally molded packaged inductor.

[0045] Example 3 A method for manufacturing a thermosetting packaged integrated inductor comprises the following steps: S1. Weigh polyimide resin particles, aluminum oxide powder and boron nitride powder in order according to the mass percentage content of 90%, 6% and 4%, and mix them thoroughly to obtain a thermally conductive thermosetting polymer packaging material.

[0046] S2. Heat and melt the heat-conductive thermosetting polymer packaging material.

[0047] S3. The prepared low-impedance eddy-current magnetic core is a columnar structure with slots at both ends of the columnar low-impedance eddy-current magnetic core. A layer of thermally conductive thermosetting polymer packaging material is coated on the ends of the two copper electrode sheets and then inserted into the slots at both ends of the low-impedance eddy-current magnetic core. The wound inductor coil is placed and inserted on the low-impedance eddy-current magnetic core and adjusted to a predetermined position. The two leads of the inductor coil are respectively welded to the two copper electrode sheets. The low-impedance eddy-current magnetic core and the inductor coil are placed together in the lower mold of the plastic molding mold. The copper electrode sheets extend from both ends of the plastic molding mold. The two ends of the low-impedance eddy-current magnetic core are supported by the copper electrode sheets. A predetermined gap is retained between the low-impedance eddy-current magnetic core and the inner wall of the plastic molding mold. The upper mold and the lower mold in the plastic molding mold are tightly buckled together.

[0048] The preparation method of the low-impedance eddy-current magnetic core is as follows: Step 1. Weigh each component in the composition formula FeaNibCocPdCue according to the ratio of 75 at%, 15 at%, 2.5 at%, 7 at%, and 0.5 at%, mix them evenly, and without adding a binder, press them into blocks. After the first heat treatment, perform a grinding process to obtain a high-permeability crystalline alloy powder; the temperature of the first heat treatment is 430 °C.

[0049] Step 2. Coating the surface of the high-permeability crystalline alloy powder with a silica film: The specific steps for coating the silica film are as follows: Disperse the high-permeability crystalline alloy powder in an ethanol aqueous solution, add a catalyst and continuously stir, disperse by ultrasonic for 15 min, then use a peristaltic pump to dropwise add tetraethyl orthosilicate at a dropping rate of 25 rpm. After continuously stirring and ultrasonic until the dropping is completed, keep ultrasonic for 7 min and then turn off the ultrasonic, and continuously stir to make it react for 8 h. After drying, obtain the high-permeability crystalline alloy powder coated with a silica film; the catalyst is ammonia water or tetramethylammonium hydroxide. The film thickness of the silica film is 35 μm.

[0050] Step 3. Place the high-permeability crystalline alloy powder into a low-leakage eddy current magnetic core forming mold, and without adding a binder, press it into a magnetic core blank; the pressure used for pressing is 2.2 GPa.

[0051] Step 4. Perform the second heat treatment and annealing treatment: Perform the second heat treatment on the magnetic core blank in an inert gas environment, and then perform an annealing treatment to obtain a low-leakage eddy current magnetic core; the temperature of the second heat treatment is 590 °C, the temperature of the annealing treatment is 290 °C, and the annealing time is 1.75 hours.

[0052] S4. Evacuate the plastic packaging mold, keep the vacuum degree of the plastic packaging mold within the range of 0.95 MPa, and fill the cavity of the plastic packaging mold with the heat-conductive thermosetting polymer packaging material after heating and melting. The filling and packaging pressure is 9 MPa, and the temperature is 330 °C; S5. After the filling and packaging are completed, perform a curing treatment. The curing temperature is 155 °C, and the curing time is 1.75 hours, so that the heat-conductive thermosetting polymer packaging material is completely cured and tightly combined with the low-leakage eddy current magnetic core and the inductor coil to form an integrally molded packaged inductor.

[0053] Experimental detection Perform the following experimental detections on the above 3 embodiments respectively: 1. The core loss P of the low-leakage eddy current magnetic core X Test: Use an IWATSU-SY-8218 type hysteresis loop tester to test the core loss P X (f = 1 MHz, B = 10 mT).

[0054] 2. Measurement of the permeability μ of the low-impedance eddy current magnetic core: The initial permeability μ (1 MHz) of the low-impedance eddy current magnetic core was measured using an inductance precision analyzer.

[0055] The core loss P of the low-impedance eddy current magnetic cores prepared in Examples 1-3 X was tested, and the measurement results are shown in Table 1: Table 1 Measurement results of the core loss PX of the low-impedance eddy current magnetic cores in three examples Low-impedance eddy current magnetic core Example 1 Example 2 Example 3 Average <![CDATA[Core loss P X (mW / cm 3 )]]> 8 7 9 8 As can be seen from Table 1, the low-impedance eddy current magnetic core is made by improving the high-permeability crystalline alloy powder material and wrapping a silica film on its surface. Under the action of the silica film, the average value of the low-impedance eddy current magnetic cores prepared in the three examples reached 8 mW / cm 3 , compared with the magnetic cores of commonly used inductors on the existing market, the core loss P X was greatly reduced, and the core loss was reduced by more than 30%.

[0056] The permeability μ of the low-impedance eddy current magnetic cores prepared in Examples 1-3 was tested, and the measurement results are shown in Table 2: Table 2 Measurement results of the permeability μ of the low-impedance eddy current magnetic cores in three examples Low-impedance eddy current magnetic core Example 1 Example 2 Example 3 Average Magnetic permeability μ 56 67 63 62 As can be seen from Table 2, the low-impedance eddy current magnetic core has a silica film wrapped on the surface of the high-permeability crystalline alloy powder material. By controlling the thickness of the silica film, the influence of the silica film on the permeability is greatly reduced. By improving the high-permeability crystalline alloy powder material to maximize the permeability, under the influence of the silica film, the average value of the permeability μ of the magnetic core can still reach 62, which is basically the same as the permeability of 60 of the magnetic cores of commonly used inductors on the existing market.

[0057] In addition, the thermal conductivity of the thermosetting encapsulation integrated inductor thermally conductive thermosetting polymer encapsulation material was also tested: When testing the thermal conductivity of the thermally conductive thermosetting polymer encapsulation material, the Guarded Heat Flow Meter Method (GHFM) was used in this application. Principle: Based on the heat flow meter method, a thermal protection furnace is equipped around to ensure that the heat flow in the test area is as uniform as possible and prevent heat from escaping along the edges. Advantages: Suitable for samples with relatively high thermal conductivity, reducing the influence of lateral heat loss. Scope of application: Samples with a thermal conductivity between 0.1 W / (m·K) and 40 W / (m·K). The existing technology uses modified epoxy resin for the encapsulation of inductors. Compared with the modified epoxy resin, the thermal conductivity of the thermally conductive thermosetting polymer encapsulation material in this application has increased by more than 40%.

[0058] In addition, without contradiction to each other, those skilled in the art may combine and combine different embodiments or examples described in this specification, as well as the features of different embodiments or examples. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A thermosetting package integrated inductor, characterized in that: It comprises a low-conductivity eddy-current magnetic core, an inductor coil and a thermally conductive thermosetting polymer packaging material. The thermally conductive thermosetting polymer packaging material integrally packages the low-conductivity eddy-current magnetic core and the inductor coil. The thermally conductive thermosetting polymer packaging material has electrical insulation and thermal conductivity. The low-conductivity eddy-current magnetic core is formed by pressing a high-permeability mixed crystal phase alloy powder wrapped with a silicon dioxide film, and has low thermal conductivity characteristics and high insulation impedance characteristics. The thickness of the silicon dioxide film is controlled to be below 50 μm and above 20 μm.

2. The thermosetting package integrated inductor according to claim 1, characterized in that: The high magnetic permeability mixed crystal phase alloy powder is represented by a composition formula of FeaNibCocPdCue, wherein 70≤a≤80at%, 10≤b≤20at%, 1≤c≤3at%, 6≤d≤8at%, 0.4≤e≤0.6at% and a+b+c+d+e=100at%, and the high magnetic permeability mixed crystal phase alloy powder is composed of an amorphous phase with a volume ratio of 82-88% and a crystalline phase of 12-18%.

3. The thermosetting package integrated inductor according to claim 2, characterized in that: The thermal conductive thermosetting polymer packaging material is a mixture of polyimide resin, aluminum oxide micropowder and boron nitride micropowder, wherein the mass percentage of the polyimide resin is 80-90%, the mass percentage of the aluminum oxide micropowder is 6-12%, and the mass percentage of the boron nitride micropowder is 4-8%.

4. The thermosetting package integrated inductor according to claim 3, characterized in that: The preparation method of the low-impedance eddy-current magnetic core is as follows: Step 1. According to the ratio of 70≤a≤80at%, 10≤b≤20at%, 1≤c≤3at%, 6≤d≤8at%, 0.4≤e≤0.6at% and a+b+c+d+e=100at%, the components in the composition formula FeaNibCocPdCue are weighed and mixed evenly, and without adding a binder, the components are pressed into blocks, subjected to the first heat treatment, and then ground to obtain a high permeability crystalline alloy powder; Step 2. Wrapping a silicon dioxide film on the surface of the high permeability crystalline alloy powder: The specific steps of the silicon dioxide film coating are as follows: disperse the high permeability crystalline alloy powder in an ethanol aqueous solution, add a catalyst and continue stirring, disperse it by ultrasonication for 10 to 20 minutes, then drop tetraethyl orthosilicate with a peristaltic pump, the speed of dropping tetraethyl orthosilicate is 20 to 30 rpm, continue stirring and ultrasonication until the addition is completed, then keep ultrasonication for 6 to 8 minutes and then turn off the ultrasound, continue stirring to react for 7 to 9 hours, and obtain a high permeability crystalline alloy powder wrapped with a silicon dioxide film after drying; Step 3: placing the high magnetic permeability crystalline alloy powder into a low-conductivity eddy current magnetic core forming mold, and pressing it into a magnetic core blank without adding a binder; Step 4. Perform a second heat treatment and annealing treatment: Perform a second heat treatment on the core blank in an inert gas environment, and then perform annealing treatment to obtain a low-impedance eddy current core.

5. The thermosetting package integrated inductor according to claim 4, characterized in that: In the step 1, the temperature of the first heat treatment is 420-440°C.

6. The thermosetting package integrated inductor according to claim 5, characterized in that: In the step 2, the catalyst is aqueous ammonia or tetramethylammonium hydroxide.

7. The thermosetting packaged integrated inductor according to claim 6, characterized in that: In step 3, the pressing pressure is 2.1-2.3 GPa.

8. The thermosetting packaged integrated inductor according to claim 7, characterized in that: In step 4, the temperature of the second heat treatment is 580-600° C., the temperature of the annealing treatment is 280-300° C., and the annealing time is 1.5-2 hours.

9. A method for preparing the thermosetting packaged integrated inductor according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. According to the mass percentage content of 80-90%, 6-12%, and 4-8%, polyimide resin particles, aluminum oxide powder and boron nitride powder are weighed in sequence and mixed thoroughly to obtain a thermally conductive thermosetting polymer encapsulation material; S2. heating and melting the thermally conductive thermosetting polymer encapsulation material; S3. The prepared low-impedance eddy current magnetic core is a columnar structure, and slots are provided at both ends of the low-impedance eddy current magnetic core of the columnar structure. A layer of heat-conductive thermosetting polymer packaging material is coated on the ends of the two copper electrode sheets and then inserted into the slots at both ends of the low-impedance eddy current magnetic core. The wound inductor coil is placed and inserted on the low-impedance eddy current magnetic core and adjusted to a predetermined position. The two leads of the inductor coil are respectively welded to the two copper electrode sheets, and the low-impedance eddy current magnetic core and the inductor coil are placed together in the lower mold of the plastic packaging mold. The copper electrode sheets extend from both ends of the plastic packaging mold. The two ends of the low-impedance eddy current magnetic core are supported by the copper electrode sheets. A predetermined gap is retained between the low-impedance eddy current magnetic core and the inner wall of the plastic packaging mold. The upper mold and the lower mold in the plastic packaging mold are tightly buckled together; S4. The plastic mold is evacuated, and the heated and melted thermal conductive thermosetting polymer encapsulation material is filled into the mold cavity of the plastic mold, the filling encapsulation pressure is 8-10MPa, and the temperature is 260 - 400 ℃; S5. After the filling and packaging is completed, a curing treatment is performed with a curing temperature of 130-180°C and a curing time of 1.5-2 hours, so that the thermally conductive thermosetting polymer packaging material is completely cured and tightly combined with the low-impedance eddy current core and the inductor coil to form an integrally molded packaged inductor.

10. The method for preparing a thermosetting packaged integrated inductor according to claim 9, characterized in that: The vacuum degree of the plastic packaging mold is maintained in the range of 0.9-1 MPa.

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