A method for fabricating an inductor

Abstract

This invention discloses a method for manufacturing an inductor, comprising the following steps: pressing a magnetic material coated with insulating resin into a magnetic core and a base; winding a coil on the surface of the magnetic core to form a coil core assembly; detachably fixing several coil core assemblies to a fixture; transferring the fixture to the base and bringing the coil core assemblies into contact with the base; applying pressure to the fixture toward the base to embed at least half of the coil core assembly into the base to form an assembly, while simultaneously separating the coil core assembly from the fixture and removing the fixture; filling the side of the base where the coil core assembly is embedded with magnetic powder coated with insulating resin to flatten the side, and then processing it to obtain a magnetic sheet; cutting the magnetic sheet into several inductor substrates; coating the inductor substrates with an outer coating layer; removing part of the outer coating layer from the sides; and fabricating electrode terminals on the side where the coating layer has been removed to obtain the finished inductor.

Description

Technical Field

[0001] This invention relates to the field of inductor fabrication, and particularly to a method for fabricating an inductor. Background Technology

[0002] Electronic products such as mobile phones, tablets, and smart wearable devices continue to develop towards miniaturization and thinness, while their functions are becoming increasingly rich, which also puts forward higher requirements for electronic components. As one of the most important passive components in electronic circuits, inductors need to have the characteristics of small size, low DC resistance, high current, and low loss in order to meet market demands.

[0003] Chinese patent CN108735429A discloses a coil component (inductor) in which a coil conductor is embedded in a magnetic part containing metal particles and resin material. A groove is provided at the bottom of the magnetic part, and the coil conductor is led out. This structure allows for a smaller coil component. The magnetic part includes a blade, a magnetic frustum disposed on the blade, and a groove disposed on the bottom surface of the blade. This is also the current mainstream high-performance miniature inductor structure. Its specific manufacturing method is as follows: the magnetic part is formed by pressing and further heat-treated to improve its strength; the coil conductor is directly wound onto the magnetic part; and then magnetic material powder is added and pressed to obtain the inductor substrate. The main drawbacks of this method are as follows: First, since the coil conductor is directly wound on the magnetic part, the magnetic part needs to have high strength and must undergo heat treatment. However, after heat treatment, the resin in the magnetic part has been cured, making it difficult to bond with the magnetic material powder added in the second pressing. This can easily lead to delamination and the formation of air gaps, reducing the inductance of the finished product. Second, the blades of the magnetic part are clamped during winding. When manufacturing small-sized inductors such as 2016 and 1608, even after heat treatment, the blades are prone to breakage.

[0004] To address the aforementioned issues, Chinese Patent CN105355409A discloses a method for manufacturing surface-mount inductors. This method involves creating a base with a boss and first winding a hollow coil, then fitting it onto the boss on the base. This overcomes the difficulties of winding and the tendency for the blades to break. Further optimization involves pressing the entire coil and then cutting it into the inductor substrate. However, this method also has some drawbacks: First, to ensure the hollow coil can fit smoothly onto the boss, the inner diameter of the coil must be larger than the size of the boss. After the coil is fitted, there is room for movement in all directions, increasing the risk of cutting the coil during cutting. Second, the bosses of micro-sized inductors are small, making the pressing of the base difficult. Third, during the pressing process, the boss bears significant pressure. When manufacturing micro-sized inductors such as 2016 and 1608, the boss is too small, and the junction between the boss and the base is a stress concentration point, making it prone to breakage. This creates an air gap inside the inductor, reducing its inductance.

[0005] When inductors are used in switching power supply circuits, reducing hysteresis and eddy current losses in high-frequency applications is a key research topic in order to improve power conversion efficiency. Iron-based amorphous powder and iron-based nanocrystalline powder are widely used in inductor manufacturing due to their low-loss characteristics. However, these two types of powders have high hardness and are not easily deformed under pressure, resulting in poor pressing performance. Therefore, magnetic cores made from iron-based amorphous powder and iron-based nanocrystalline powder generally have low strength. Both of these technical solutions place high demands on the strength of the magnetic core, further increasing the manufacturing difficulty. Therefore, a new technical solution is urgently needed to overcome the difficulties encountered by existing technologies. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention discloses a method for fabricating an inductor.

[0007] A method for fabricating an inductor includes the following steps:

[0008] Step 1: Press the magnetic material coated with insulating resin into a magnetic core and a base, with the density of the pressed magnetic core being greater than that of the base. Wrap a coil around the surface of the magnetic core to form a coil-core assembly with two connecting legs.

[0009] Step 2: Detachably fix several coil core assemblies onto the fixture, then transfer the fixture with the coil core assemblies to the base, and make the coil core assemblies and the base come into contact;

[0010] Step 3: Apply pressure to the fixture toward the base so that at least half of the coil core assembly is embedded in the base, while separating the coil core assembly from the fixture and removing the fixture, so that the coil core assembly and the base form an assembly.

[0011] Step 4: Fill the side of the coil core assembly embedded on the base with magnetic powder coated with insulating resin to make the side flat. Then, the assembly filled with magnetic powder is cold-pressed, hot-pressed and heat-treated to obtain a magnetic sheet.

[0012] Step 5: According to the orientation of the coil core assembly, cut the magnetic sheet into several inductor substrates. Take the two sides corresponding to the two connecting feet on the inductor substrate as the first terminal surface and the second terminal surface, respectively. Take the side of the inductor substrate that is perpendicular to the first terminal surface and the second terminal surface as the third terminal surface.

[0013] Step 6: Apply an outer coating layer to the outer surface of the inductor substrate, and then remove the outer coating layer from the first terminal face, the second terminal face, and the third terminal face;

[0014] Step 7: Two electrode terminals are fabricated on the side of the inductor substrate where the coating has been removed. Each electrode terminal is electrically connected to a corresponding connection pin to obtain the finished inductor.

[0015] Specifically, if the density of the base is equal to or greater than that of the magnetic core, it will be difficult for the coil core assembly to be embedded in the base. Even if it is embedded in the base, the coil core assembly and the base will undergo large deformation. Therefore, the density of the pressed base should be lower than that of the magnetic core.

[0016] Several coil core assemblies are first fixed on a fixture, and then pressure is applied to the fixture so that the several coil core assemblies fixed on the fixture can be simultaneously embedded into the base. This not only significantly improves the efficiency of embedding the coil core assemblies into the base, but also improves the consistency of embedding the coil core assemblies into the base.

[0017] In addition, when removing the outer coating on the first terminal face, the second terminal face, and the third terminal face, laser removal or grinding can be used; electrode terminals are made by brushing on electrical paste and / or plating electrical paste.

[0018] Preferably, the magnetic material is one or more of the following: carbonyl iron powder, iron-based amorphous powder, iron-based nanocrystalline powder, iron-silicon powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, and iron-nickel powder. More preferably, the magnetic material is iron-based amorphous powder, iron-based nanocrystalline powder, or a mixture of both with other soft magnetic powders.

[0019] Preferably, the fixture is provided with a plurality of positioning slots for fixing the coil core assembly, and the plurality of positioning slots are arranged in an orderly manner at certain intervals.

[0020] Specifically, after fixing the coil core assembly onto the fixture, pressure is applied to the fixture as a whole to embed the coil core assembly into the base. Since the positioning slots are arranged in an orderly manner on the positioning plate, the coil core assembly remains orderly on the base after being embedded into it.

[0021] Preferably, the fixture includes a positioning plate with a plurality of positioning slots and a vacuuming device connected to each positioning slot.

[0022] When fixing the coil core assembly, first place the coil core assembly in the positioning groove, then start the vacuum pump to evacuate the positioning groove and fix the coil core assembly on the positioning plate; after the coil core assembly is embedded in the base, turn off the vacuum pump and then separate the positioning plate from the coil core assembly.

[0023] Specifically, this fixing method not only effectively fixes the coil core assembly, but also effectively prevents the positioning groove from being worn, thus effectively extending the service life of the positioning plate.

[0024] Preferably, the positioning plate is provided with a reset device for resetting the fixture after the coil core assembly is embedded into the base.

[0025] Specifically, after the coil core assembly is embedded into the base, the vacuum device is turned off and the pressure applied to the fixture is stopped. Under the action of the reset device, the fixture moves away from the base, which helps the fixture separate from the coil core assembly. Then the fixture is removed.

[0026] Preferably, the coil is wound on the magnetic core using an outer-outer winding method, and after winding, both connecting legs of the coil are located on the two outermost opposite sides of the magnetic core.

[0027] Specifically, the angle between the line connecting the two connecting feet and the central axis of the magnetic core is 30-180°.

[0028] Preferably, the coating is applied to the outer surface of the inductor substrate using a hot roller coating, dip coating, or spray coating method.

[0029] Preferably, the magnetic sheet is cut into the inductor substrate by physical cutting with a grinding wheel.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] The inductor's base has a simple shape and low manufacturing cost, while avoiding problems such as delamination and blade breakage in existing manufacturing methods. This advantage is particularly pronounced when manufacturing micro-sized inductors. By directly pressing the coil core assembly into a base with appropriate density, precise coil positioning is achieved, and the risk of boss breakage during subsequent pressing is avoided, resulting in more stable inductor performance. The coil does not rely on boss positioning; after transfer, it is directly embedded into the base, eliminating positioning inaccuracies caused by gaps and ensuring a high yield rate during cutting. Furthermore, the technical solution provided in this application addresses the problem of insufficient core strength in iron-based amorphous powder and iron-based nanocrystalline powder, enabling the application of these two powders in inductor manufacturing, which can significantly reduce losses. Attached Figure Description

[0032] Figure 1 A flowchart of the inductor fabrication method provided by the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the coil core assembly provided by the present invention;

[0034] Figure 3 A schematic diagram of the positioning plate structure of the fixture provided by the present invention;

[0035] Figure 4 This is a schematic diagram of the structure of the assembly provided by the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of the magnetic sheet provided by the present invention;

[0037] Figure 6 A schematic diagram of the cutting of the magnetic sheet provided by the present invention;

[0038] Figure 7 This is a schematic diagram of the structure of the inductor substrate provided by the present invention;

[0039] Figure 8 This is a schematic diagram of the structure of the inductor product provided by the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] A method for fabricating an inductor, such as Figure 1 As shown, it includes the following steps:

[0042] Step 1: Press the magnetic material coated with insulating resin into a magnetic core 11 and a base 20, and the density of the pressed magnetic core 11 is greater than that of the base 20.

[0043] If the density of the base 20 is equal to or greater than that of the magnetic core 11, it will be difficult for the coil core assembly 13 to be embedded in the base 20, and the base 20 will be unable to position the coil core assembly 13. Even if it is embedded in the base 20, the coil core assembly 13 and the base 20 will undergo large deformation. Therefore, the density of the pressed base 20 should be lower than that of the magnetic core 11.

[0044] like Figure 2 As shown, a coil core assembly 13 with two connecting legs is formed by winding a coil 12 on the surface of the magnetic core 11;

[0045] When the coil 12 is wound on the magnetic core 11, it adopts an outer-outer winding method. After the winding is completed, the two connecting feet 14 of the coil 12 are located on the two outermost opposite sides of the magnetic core 11. After the winding is completed, the angle between the line connecting the two connecting feet 14 and the central axis of the magnetic core 11 is 30-180°.

[0046] The magnetic material is one or more of the following: carbonyl iron powder, iron-based amorphous powder, iron-based nanocrystalline powder, iron-silicon powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, and iron-nickel powder. More preferably, the magnetic material is iron-based amorphous powder, iron-based nanocrystalline powder, or a mixture of both with other soft magnetic powders.

[0047] Step 2: Detachably fix several coil core assembly parts 13 onto the fixture 30, then transfer the fixture 30 with the coil core assembly parts 13 onto the base 20, and make the coil core assembly parts 13 and the base 20 come into contact.

[0048] The fixture 30 is provided with a plurality of positioning slots 32 for fixing the coil core assembly 13, and the plurality of positioning slots 32 are arranged in an orderly manner at certain intervals.

[0049] The positioning slots 32 are usually arranged in an array. After the coil core assembly 13 is fixed on the fixture 30, pressure is applied to the fixture 30 as a whole to make the coil core assembly 13 embed into the base 20. Since the positioning slots 32 are arranged in an array on the positioning plate 31, after the coil core assembly 13 is embedded into the base 20, the coil core assembly 13 is still arranged in an array on the base 20.

[0050] like Figure 3 As shown, the fixture 30 includes a positioning plate 31 with a plurality of positioning slots 32, and a vacuuming device connected to each positioning slot 32.

[0051] When fixing the coil core assembly 13, first place the coil core assembly 13 in the positioning groove 32, then start the vacuum pump to vacuum the positioning groove 32 to fix the coil core assembly 13 on the positioning plate 31; the coil core assembly 13 is embedded in the base 20, and after the vacuum pump is turned off, the positioning plate 31 is separated from the coil core assembly 13.

[0052] This fixing method not only effectively fixes the coil core assembly 13, but also effectively prevents the positioning groove 32 from being worn, and effectively extends the service life of the positioning plate 31.

[0053] The positioning plate 31 is provided with a reset device that resets the fixture 30 after the coil core assembly 13 is embedded into the base 20.

[0054] After the coil core assembly 13 is embedded into the base 20, the vacuum device is turned off and the pressure applied to the fixture 30 is stopped. Under the action of the reset device, the fixture 30 moves away from the base 20, which helps the fixture 30 to separate from the coil core assembly 13. Then the fixture 30 is removed.

[0055] Step 3: Apply pressure to the fixture 30 toward the base 20, causing at least half of the coil core assembly 13 to embed into the base 20, while simultaneously separating the coil core assembly 13 from the fixture 30 and removing the fixture 30, as shown. Figure 4 As shown, the coil core assembly 13 and the base 20 form an assembly 41;

[0056] Several coil core assemblies 13 are first fixed on the fixture 30, and then pressure is applied to the fixture 30 so that the several coil core assemblies 13 fixed on the fixture 30 can be simultaneously embedded in the base 20. This not only significantly improves the efficiency of the coil core assemblies 13 being embedded in the base 20, but also improves the consistency of the coil core assemblies 13 being embedded in the base 20.

[0057] Furthermore, the volume of the coil core assembly 13 embedded in the base 20 is 50% to 100% of its own volume;

[0058] Step 4: Fill the side of the coil core assembly 13 embedded in the base 20 with magnetic powder coated with insulating resin to flatten the side. Then, perform cold pressing, hot pressing, and heat treatment on the assembly 41 filled with magnetic powder to obtain the desired result. Figure 5 The magnetic sheet 42 shown;

[0059] Step 5, as follows Figure 6 As shown, based on the orientation of the coil core assembly 13, the magnetic sheet 42 is cut into several pieces using a grinding wheel for physical cutting. Figure 7 The inductor base 50 shown has two sides corresponding to the two connecting pins 14 on it, which are respectively used as the first terminal surface 51 and the second terminal surface 52. The side of the inductor base 50 that is perpendicular to the first terminal surface 51 and the second terminal surface 52 is used as the third terminal surface 53.

[0060] Step 6: Apply an outer coating layer to the outer surface of the inductor substrate 50 by hot roller coating, dip coating, or spray coating, and then remove the outer coating layer of the first terminal surface 51, the second terminal surface 52, and the third terminal surface 53 by laser removal or grinding removal.

[0061] Step 7: Two electrode terminals 61 are fabricated on the side of the inductor substrate 50 where the coating has been removed by brushing on electrical paste and / or plating with electrical paste. Each electrode terminal 61 is electrically connected to a corresponding connecting pin 14, resulting in the following... Figure 8 The inductor product shown is 60.

[0062] To further illustrate the advantages of successfully applying iron-based amorphous powder and iron-based nanocrystalline powder in the technical solution of this invention, the following treatment groups were set up with different magnetic materials as variables, and inductor products were manufactured for performance testing.

[0063] The composition of the magnetic material powder in each treatment group is shown in Table 1:

[0064] Table 1

[0065]

[0066] Taking the 1412065-R47 specification as an example, the inductance, DC resistance, saturation current, and conversion efficiency of the inductor were tested. The conversion efficiency test method was to install each group of inductors on the same step-down module circuit and test them under the same frequency and input voltage conditions. The test results of each group are shown in Table 2.

[0067] Table 2

[0068]

[0069] Therefore, it can be seen that, with other performance remaining unchanged, the conversion efficiency of treatment group 1 is better than that of the control group. Continuing to increase the proportion of iron-based amorphous powder in the raw materials will decrease the saturation current, but the conversion efficiency will continue to improve, showing a clear advantage in circuits that require high conversion efficiency.

[0070] The base 20 of the inductor finished product 60 manufactured according to the method provided in this embodiment has a simple shape and low manufacturing cost. At the same time, it avoids the problems of delamination and blade breakage in existing manufacturing methods, and has more obvious advantages when manufacturing micro-sized inductors. By directly pressing the coil core assembly 13 into the base 20 with appropriate density, the precise positioning of the coil 12 is achieved, and the risk of the boss breaking during subsequent pressing is avoided, resulting in more stable performance of the inductor finished product 60. The coil 12 does not rely on the boss for positioning and is directly embedded into the base 20 after transfer. There is no positioning inaccuracy caused by the fit gap, which can ensure the pass rate of cutting. The technical solution provided in this embodiment can solve the problem of insufficient strength of the magnetic core 11 made of iron-based amorphous powder and iron-based nanocrystalline powder, and realize the application of the above two powders in inductor manufacturing, which can significantly reduce losses.

Claims

1. A method of fabricating an inductor, characterized by, The method comprises the following steps: Step 1, pressing the magnetic material coated with insulating resin into a magnetic core and a base, and the density of the pressed magnetic core is greater than that of the base, winding a coil on the surface of the magnetic core to form a coil magnetic core combination part with two connecting pins, Step 2, detachably fixing a plurality of coil magnetic core combination parts on a jig, and then transferring the jig with the coil magnetic core combination parts to the base and making the coil magnetic core combination parts contact the base; Step 3, giving the jig a pressure towards the base, so that at least half of the coil magnetic core combination part is embedded into the base, and then separating the coil magnetic core combination part from the jig, moving away the jig, and forming an assembly of the coil magnetic core combination part and the base; Step 4, filling the magnetic powder coated with insulating resin on the side of the base where the coil magnetic core combination part is embedded, filling the side flat, and then performing cold pressing, hot pressing and heat treatment on the assembly filled with the magnetic powder to obtain a magnetic sheet; Step 5, cutting the magnetic sheet into a plurality of inductor substrates according to the orientation of the coil magnetic core combination part, taking two sides of the inductor substrate corresponding to the two connecting pins as a first terminal surface and a second terminal surface respectively, and taking the side of the inductor substrate perpendicular to the first terminal surface and the second terminal surface as a third terminal surface; Step 6, coating an outer coating layer on the outer surface of the inductor substrate, and then removing the outer coating layer of the first terminal surface, the second terminal surface and the third terminal surface; Step 7, manufacturing two electrode terminals on the side of the inductor substrate where the coating layer is removed, each electrode terminal being in electrical communication with a corresponding connecting pin, and obtaining an inductor finished product.

2. The method of claim 1, wherein the method further comprises: The magnetic material is a mixture of one or more of carbonyl iron powder, iron-based amorphous powder, iron-based nanocrystalline powder, iron-silicon powder, iron-silicon-chromium powder, iron-silicon-aluminum powder, and iron-nickel powder.

3. The method of claim 2, wherein the step of forming the magnetic core comprises forming the magnetic core by sintering a powder of a magnetic material. The magnetic material is iron-based amorphous powder, iron-based nanocrystalline powder, or a mixture of the two and other soft magnetic powders.

4. The method of claim 1, wherein the method further comprises: The jig is provided with a plurality of positioning grooves for fixing the coil magnetic core combination part, and the plurality of positioning grooves are arranged in order at a certain interval.

5. The method of claim 4, wherein the step of forming the magnetic core comprises forming the magnetic core by sintering a powder of the magnetic material. The jig comprises a positioning plate provided with a plurality of positioning grooves, and a vacuum pumping device connected with each positioning groove; When fixing the coil magnetic core combination part, first place the coil magnetic core combination part in the positioning groove, and then start the vacuum pumping device to fix the coil magnetic core combination part on the positioning plate; after embedding the coil magnetic core combination part into the base, turn off the vacuum pumping device, and then separate the positioning plate from the coil magnetic core combination part.

6. The method of claim 5, wherein the step of forming the magnetic core comprises forming the magnetic core by sintering a powder of the magnetic material. The positioning plate is provided with a reset device for resetting the jig after embedding the coil magnetic core combination part into the base.

7. The method of claim 1, wherein the method further comprises: When winding the coil on the magnetic core, the outer outer winding method is adopted, and after winding, the two connecting pins of the coil are located at the two outermost sides of the magnetic core.

8. The method of claim 1, wherein the method further comprises: The coating layer is coated on the outer surface of the inductor substrate by hot rolling coating or dipping coating or spraying.

9. The method of claim 1, wherein the method further comprises: The magnetic sheet is cut into inductor substrates by physical cutting with a grinding wheel.

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