KR102385618B1 - Power inductor - Google Patents

Abstract

In an embodiment of the present invention, a laminate having a first surface and a second surface opposite to it, and having a via hole disposed in the center thereof, at least one circuit pattern included in the laminate to be adjacent to the via hole, and insertion and coupling into the via hole and a coil wound around a magnetic core, the coil bridge comprising a coil assembly connected to the circuit pattern and an external terminal disposed on a side surface of the stack to be connected to the circuit pattern, at least one of the via hole or the magnetic core The shape of one cross-section makes it possible to provide a multilayer power inductor having a structure of a single closed curve having a major axis and a minor axis.

Description

Stacked Power Inductor

Embodiments of the present invention relate to a multilayer power inductor capable of securing structural stability and having high DC superposition characteristics and high frequency characteristics.

In general, portable devices use direct current (DC) power supplied from a secondary battery to obtain operating power of various voltages required for an internal circuit, and use a power circuit such as a DC-DC converter. In this case, the DC-DC converter is also required to be implemented in a compact size in accordance with the lightweight, thin and compact portable devices.

As the switching frequency of the DC-DC converter increases, it can be used at high frequencies and the characteristics of excellent DC superposition characteristics (DC bias characteristics) for large currents are continuously increasing.

With the increase in the usage of portable DC-DC converters, the need for large currents increases, and the mounting area is insufficient due to the increase in the use of inductors, so the demand for small size inductors continues.

In the conventionally disclosed multilayer inductor, a magnetic film containing an Fe-Si-Cr alloy or Fe-Si-Al alloy powder is manufactured, a coil magnetic core is vertically arranged therein, and then a magnetic film is formed on the upper and lower parts of the coil magnetic core. laminated curing to manufacture a panel.

After the manufactured panel is vertically routed so that the coil bridge is exposed, the internal coil and copper plating terminal are connected through chemical copper and electrolytic copper processes. Thereafter, the inductor is manufactured by plating the copper plating surface with tin through a barrel process.

However, in the case of the existing process, when the coil magnetic core is inserted into the magnetic sheet, it is difficult to align the coil magnetic core in a certain shape, and there is a possibility that the coil magnetic core may be misaligned in the process of laminating the magnetic film on the upper and lower parts. In addition, in order to minimize the movement of the magnetic core of the coil, an increase in material cost may occur due to a process such as adding an adhesive sheet to the lower portion and addition of auxiliary materials. In addition, surface oxidation of the magnetic sheet that occurs in the electroplating process can cause a decrease in copper plating adhesion, which can cause product reliability and characteristics deterioration due to lower adhesion between the chip and the copper plating layer. When chemical concentration and foreign substances are generated, protrusions may occur on the copper plating surface, resulting in poor appearance or changes in the adhesion strength of the copper plating layer.

In addition, when the area of the coil attached to the copper plating surface is calculated as the cross-sectional area of the coil, when using a copper wire with a small outer diameter, there may be a problem in that the copper plating adhesion must be strengthened due to the outer diameter of the small copper wire. A large amount of wastewater may be generated, which may result in environmental pollution or the need for large-scale wastewater treatment facilities.

In addition, since the shape of the magnetic core and the hole are manufactured to be the same, the position is shifted due to a minute tolerance within the via hole of the magnetic core, which acts as a factor impairing structural reliability.

Embodiments of the present invention have been devised to solve the above problems, and by implementing the shape of the cross section of the magnetic core inserted into the via hole or the via hole of the laminate in an oval shape, structural stability is secured without affecting the magnetization performance. It makes it possible to provide a stacked power inductor that can do this.

Furthermore, it is possible to provide a power inductor capable of realizing the same material as the laminate into which the coil magnetic core is inserted and the material of the coil magnetic core, thereby reducing manufacturing cost and realizing a high frequency of use and a large amount of capture current.

As a means for solving the above problems, in an embodiment of the present invention, at least a laminate having a first surface and a second surface opposite to it and a via hole disposed in the center, and at least included in the laminate so as to be adjacent to the via hole one or more circuit patterns, a coil inserted and coupled to the via hole, and wound around a magnetic core, a coil assembly having a coil bridge connected to the circuit pattern, and an external terminal disposed on a side surface of the stack to be connected to the circuit pattern and a cross-sectional shape of at least one of the via hole and the magnetic core can provide a multilayer power inductor having a structure of a single closed curve having a major axis and a minor axis.

According to an embodiment of the present invention, it is possible to provide a multilayer power inductor capable of securing structural stability without affecting magnetization performance by implementing the shape of the cross section of the magnetic core inserted into the via hole or the via hole of the laminate in an oval shape. there is an effect

In addition, while realizing an oval-shaped magnetic core or an elliptical via-hole structure, the same material as the laminated body into which the coil magnetic core is inserted and the coil magnetic core material are implemented to reduce manufacturing costs, and at the same time provide a high frequency of use and large-capacity capture current. There is an effect that can implement.

In addition, it is possible to stably align the magnetic core of the coil without a separate member and form a high-reliability product terminal. There is also an effect of securing structural stability by preventing the coil magnetic core from being twisted by an external impact when the lower magnetic sheet is laminated.

Furthermore, it is possible to provide a multilayer power inductor capable of realizing stable product characteristics by increasing a contact area between an external terminal electrically connected to the coil bridge and a circuit pattern.

In addition, according to an embodiment of the present invention, it is possible to reduce the process cost due to the simplification of the process by excluding the copper plating process, to minimize product defects due to lowering of adhesion that may occur in the copper plating process, and to treat wastewater by minimizing the generation of wastewater. The advantage of reducing additional costs is realized.

According to an embodiment of the present invention, by using a conductive paste (Ag, Cu, Ni paste, etc.) for the external terminal connected to the circuit pattern, the copper plating process can be excluded, so surface oxidation and adhesion decrease that may occur in the copper plating process , surface protrusion, and wastewater problems can be solved, and the reliability of DC resistance can be increased by increasing the contact area between circuit patterns and external terminals.

1 is a perspective view showing an external appearance of a multilayer power inductor according to an embodiment of the present invention, FIG. 2A is a cross-sectional view (Y-Y′) of the multilayer power inductor according to FIG. 1 , and FIGS. 2B to 2D are main parts of FIG. 2A It is a conceptual diagram to explain the structure of In addition, FIG. 3A is a longitudinal cross-sectional view (X-X′) of the multilayer power inductor according to FIG. 1 , and FIGS. 3B and 3C are conceptual views illustrating an embodiment of the magnetic core and the laminate applied to FIG. 1 .
4 to 6 are views illustrating a manufacturing process of a multilayer power inductor according to an embodiment of the present invention, respectively.

Hereinafter, the configuration and operation according to the present invention will be described in detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, the same components are given the same reference, regardless of the reference numerals, and redundant description thereof will be omitted. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

1 is a perspective view showing the exterior of a multilayer power inductor according to an embodiment of the present invention, FIG. 2A is a cross-sectional view (Y-Y′) of the multilayer power inductor according to FIG. 1 , and FIGS. 2B to 2D are main parts of FIG. 2A It is a conceptual diagram to explain the structure of In addition, FIG. 3A is a longitudinal cross-sectional view (X-X′) of the multilayer power inductor according to FIG. 1 , and FIGS. 3B and 3C are conceptual views illustrating an embodiment of the magnetic core and the laminate applied to FIG. 1 .

1 to 3C, the multilayer power inductor according to an embodiment of the present invention includes a stacked body 110 having a first surface and a second surface opposite thereto, and having a via hole H disposed in the center thereof; At least one circuit pattern 120 included in the laminate so as to be adjacent to the via hole H, and a coil 132 inserted and coupled to the via hole H and wound around a magnetic core 121, and a coil bridge ( 133) may include a coil assembly 130 connected to the circuit pattern, and an external terminal 180 disposed on a side surface of the stack to be connected to the circuit pattern 120 .

In particular, in this case, the shape of the cross section of at least one of the via hole and the magnetic core may be implemented to have a structure of a single closed curve having a major axis and a minor axis. In an embodiment of the present invention, the 'major axis' means the length of a line segment implementing the longest diameter at the center of the cross section, and the 'short axis' is defined as the length of the line segment implementing the shortest diameter at the center of the cross section. And, the 'center' is defined as the center of gravity of the cross section.

Specifically, the cross section of at least one of the via hole and the magnetic core may be implemented to have different structures, or may be implemented to have an elliptical structure of the same shape. In this case, when the coil assembly 130 is mounted inside the via hole H in a structure in which the coil assembly 130 is interpolated, the shape of the cross section of the via hole H and the coil assembly 130 is the same as the circular shape as the use time elapses. A phenomenon in which the assembly moves finely within the via hole occurs, and structural stability is not secured, resulting in a short circuit between the circuit pattern and the coil bridge. When these are implemented in different structures, or when they are all implemented in an elliptical structure of the same shape, it is possible to solve the problem by minimizing the movement of the magnetic core.

Furthermore, as will be described later, this way, in the manufacturing process of a multilayer power inductor according to an embodiment of the present invention, a structure generated while manufacturing a multilayer body and processing a via hole is realized as a magnetic core, thereby reducing material costs. Of course, by implementing high inductance by improving magnetization characteristics, it is possible to realize a high frequency of use and a large amount of capture current.

Referring to FIG. 2A , in the internal structure of the multilayer power inductor according to an embodiment of the present invention, the magnetic core is implemented in a cylindrical structure, the cross-sectional shape is implemented as an elliptical structure, and a coil is wound on the surface of the elliptical magnetic core. After that, it is inserted into the laminate 130 . In this case, the cross-sectional shape of the via hole H may also be implemented in an elliptical shape. In this structure, when the coil bridge 132 is joined to the circuit pattern, the magnetic core and the via hole are implemented in an elliptical structure, and the contact portion between the inner surface of the via hole H and the surface of the coil outside of the magnetic core becomes close, Due to the elliptical shape, the self-rotation of the magnetic core is prevented and structural stability can be secured.

2B is a conceptual view of the shape of the main portion of FIG. 2A. In this embodiment, the shape of the cross-section of the magnetic core 131 is implemented to have an elliptical shape, and the shape of the via hole H is also implemented to have an oval shape. do. In this case, considering the length a2 of the major axis and the length a1 of the minor axis of the cross section of the via hole H, as shown in (b) of FIG. 2B, the length of the minor axis of the cross section of the magnetic core shown in (c) (b1), the length a1 of the minor axis of the cross section of the via hole H can be formed to be larger than the length b1 of the minor axis of the cross section of the magnetic core between the length b2 of the major axis of the cross section of the magnetic core. In particular, the ratio of the length of the minor axis of the cross section of the via hole to the length of the minor axis of the cross section of the magnetic core is 1: 0.8 to 0.9. If the range of the ratio is smaller than the ratio of 0.8, it is difficult to exert a stable fixing force even after winding the coil and the magnetic susceptibility is decreased. In particular, in the shape shown in FIG. 2A , the outer peripheral surface of the coil wound on the outer surface of the magnetic core and the inner surface of the via hole H can contact at least two or more places (the end point of the short axis or the end point of the long axis), so a very stable fixing force will be able to perform

FIG. 2C is an embodiment implemented in a different structure from FIG. 2B. The difference is that the shape of the cross-section of the via hole H has an elliptical shape, and the shape of the magnetic core can be implemented to have a circular shape. Also in this case, the ratio of the minor axis length (a1) of the cross section of the via hole to the minor axis length (b1) of the cross section of the magnetic core is 1: 0.8 to 0.9.

2D shows an example in which the structure of the via hole is implemented in a circular shape, but the shape of the cross-section of the magnetic core is implemented in an oval shape. In this case, the end point of the long axis of the elliptical shape of the cross section of the magnetic core comes into contact with at least two places on the inner surface of the via hole H, and a stable fixing force can be exerted. Also in this case, the ratio of the minor axis length (a1) of the cross section of the via hole to the minor axis length (b1) of the cross section of the magnetic core is 1: 0.8 to 0.9.

3A is a longitudinal cross-sectional view of a multilayer power inductor according to an embodiment of the present invention to which the arrangement structure of magnetic cores and via holes as described above with reference to FIGS. 2A to 2D is applied. In this embodiment, the embodiment to which the structure of FIG. 2A is applied will be described as an example.

Referring to FIG. 3A , the multilayer power inductor according to an embodiment of the present invention includes a stacked body 110 having a first surface and a second surface opposite thereto, a via hole H is disposed in the center thereof, and the via hole ( At least one circuit pattern 120 included in the laminate so as to be adjacent to H), a coil 132 inserted and coupled to the via hole H, and wound around a magnetic core 121 , and a coil bridge 133 is provided. The coil assembly 130 connected to the circuit pattern may be configured to include an external terminal 180 disposed on a side surface of the stack to be connected to the circuit pattern 120 . In particular, the shape of the cross section of the via hole H is implemented in an elliptical shape, and the shape of the magnetic core can also be implemented in an oval shape.

The laminate 110 has a first surface A and a second surface B opposite thereto, and a via hole 111 is formed in the center thereof. When referring to the drawings, the first surface (A) may be the upper surface of the laminate, and the second surface (B) may be the lower surface. The laminate 110 may be manufactured by stacking a plurality of magnetic sheets filled with soft magnetic metal powder. That is, the magnetic sheet is formed in the form of a sheet by filling a soft magnetic metal powder in a polymer binder.

In particular, the laminate 110 according to the embodiment of the present invention may be implemented as a structure in which magnetic sheets are laminated in multiple layers, as shown in FIG. 3B , and an oval via hole is formed through mechanical processing (drill, punching machine). to be able to be processed. Thereafter, a cylindrical structure having an elliptical cross-section is used as a magnetic core, a coil is wound on the outer surface of the magnetic core, and the coil is inserted into the via hole to be mounted.

Alternatively, as another embodiment, the magnetic core 131 may utilize a by-product itself generated in the process of forming the via hole H. That is, as shown in (a) of Figure 3b, to implement a structure in which the unit magnetic sheets (110a, 110b, 110c, 110d) are stacked in multiple layers, and to have a constant diameter (d1) (b) As shown, when the via hole (H) is processed through the punching process, the magnetic sheet laminate at the position of the via hole is separated to form a cylindrical structure by-product, which can be used as the magnetic core 131 in the embodiment of the present invention. . In this case, the via hole (H) can be processed to have a wider diameter (d2) through secondary punching using a drill, milling, or punching machine after being primarily implemented with a constant diameter (d1). . This is to facilitate insertion of the coil after being wound around the outer circumferential surface of the magnetic core and then being inserted into the via hole.

For example, using an elliptical cylindrical structure punched out by using a punching machine having an elliptical cross-sectional shape as a magnetic core, and processing the hole drilled by punching primarily, the via hole can be machined in a range having a longer major axis and minor axis. there is.

Therefore, the magnetic core 131 according to the embodiment of the present invention is made of the same material, and the order and material of the stacking are also implemented in the same manner as in the arrangement of the original stack. That is, the magnetic core has a stacking structure made of the same material and in the same stacking order as that of the stacked body. This arrangement can ensure the uniformity of the magnetic path according to the magnetization generated by the application of power later, thereby increasing the efficiency of the inductance.

3C is a conceptual diagram for implementing a structure of a laminate and a magnetic core according to another embodiment of the present invention. The difference from FIG. 3b is that the arrangement of the soft magnetic metal powder of the magnetic sheet for implementing the laminate is implemented differently.

That is, the soft magnetic metal powder included in the outer magnetic sheets 110a and 110d disposed at the outermost among the plurality of magnetic sheets to be stacked has anisotropy, and the inner magnetic sheet 110b disposed inside the stacked plurality of magnetic sheets. , 110c), the soft magnetic metal powder is implemented to have isotropy. This is, when considering the magnetic path (P) generated when power is applied to the inductor, the path passing through the outer surface of the soft magnetic metal powder 11 ), and the isotropic soft magnetic metal powder 12 is disposed inside the magnetic path proceeding up and down to reduce the resistance of the magnetic path. That is, in the case of disposing the anisotropic metal powder therein, the longitudinal direction of the metal powder and the magnetic path are vertically arranged, so that the efficiency of the inductance decreases. This is because the effect of increasing the inductance is realized when the longitudinal direction of the anisotropic alloy powder and the magnetic path are implemented in parallel.

In addition, even in this structure, the magnetic core 131 has the shape of FIG. 2A having an elliptical cross-section, and furthermore, the cross-sectional shape of the via hole can also be implemented in an elliptical shape.

In addition, when the magnetic core 131 is manufactured in the same manner as in FIG. 3B or 3C, the configuration at the position of the via hole is applied so that the magnetic core has the same material and stacking order as the material of the stack. , the magnetic core 131 also has a structure in which anisotropic soft magnetic metal powder is disposed on the outer shell portion and isotropic soft magnetic metal powder is disposed on the inside. This also realizes the same arrangement structure as that of the laminate even when it is inserted into the laminate after winding the coil, thereby increasing the efficiency of improving magnetic flux.

The soft magnetic metal powder used in the above-described embodiment may be anisotropic or isotropic powder of spherical and amorphous shapes. In addition, as a material of the soft magnetic metal powder, molybdenum permalloy (Mopermalloy), sandust (Fe-Si-Al alloy), iron-silicon alloy (Fe-Si alloy), iron-silicon-chromium alloy (Fe-Si-Cr alloy) ), amorphous metal, nanocrystal grains, amorphous powder, etc. may be used.

In addition, the polymer binder is an acrylic, epoxy applied as an organic polymer matrix material.

It is possible to apply a resin composed of one or more different types selected from watch, ester, urethane, phenol, butyral, vinyl, epoxy acrylate, amine, and vinyl materials.

In addition, referring to FIG. 3A , at least one circuit pattern 120 is formed on the first surface A of the laminate 110 to be adjacent to the via hole. In one embodiment, a pair of circuit patterns are formed to be symmetrical with each other with a via hole interposed therebetween. The circuit pattern 120 may be formed by selectively etching the copper foil coated on the first surface A of the laminate 110 by a physical or chemical method to correspond to the design shape. The thickness of the copper foil used at this time is preferably 17 to 35㎛.

If the thickness of the copper foil is less than 15㎛, the copper wire enters too much into the circuit pattern due to the pressure applied to the resistance welding tip, so that the adhesion cannot be sufficiently secured. ), thickness deviation may occur when the first magnetic sheet 140 is laminated on the upper side. A welding part 121 to which a coil bridge may be resistance-welded may be provided in the circuit pattern 120 . The welding part 121 may be formed by melting the coating of the copper foil layer by performing primary resistance welding of the copper foil with a current of 200 to 300A.

The coil assembly 130 is inserted and coupled to the via hole 111 of the stacked body 110 , and as described above, a magnetic core 131 having the same material and configuration as that of the stacked body, and the magnetic core 131 . It includes a conductive coil 132 wound along the outer peripheral surface. The magnetic core 131 may be implemented in a cylindrical structure having an elliptical cross-section so that the coil 132 can be easily wound, and accordingly, the coil may be wound along an elliptical surface on the outer circumferential surface of the core.

The magnetic core may be made of the same material as the laminate as described above, and the core 131 is Mo-permalloy, permalloy, Fe-Si-Al alloy, Fe-Si alloy, Fe-Si like the magnetic sheet. A composite prepared by alloy, Fe-Si-Cr alloy, silicon steel sheet, ferrite, amorphous metal, nanocrystal grains, amorphous powder and a polymer binder may be used. The polymer binder is one selected from acrylic, epoxy, ester, urethane, phenolic, butyral, vinyl, epoxy acrylate, amine, and vinyl-based materials or two or more different types applied as an organic polymer matrix material. A resin composed of At the end of the coil 132 , a coil bridge 133 may be formed to protrude in the circuit pattern direction to be connected to the circuit pattern 120 .

In addition, the power inductor according to an embodiment of the present invention includes a first magnetic sheet 140 and a second magnetic sheet that are respectively pressurized on the first side (A) and the second side (B) of the laminate; ( 150) may be further included. Each magnetic sheet is preferably filled with soft magnetic metal powder like the above-described laminate 110 .

The external terminal 180 is formed on both sides of the laminate 110 and the first magnetic sheet and the second magnetic sheet, and is physically and electrically connected to the circuit pattern 120 . The external terminal 180 includes a conductive paste, and the conductive paste may include any one of Ag, Cu, and Ni, and the conductive paste may have any one of a flake shape, a spherical shape, and an amorphous powder. The volume resistance of the conductive paste is preferably 20 μΩ·cm or less. For example, when the volume resistance of the conductive paste exceeds 20 μΩ·cm, the resistance of the power inductor product itself may increase.

Nickel and tin may be plated on the surface of the conductive paste if necessary, and parts other than the external terminals are preferably insulated by coating an epoxy resin insulator.

Meanwhile, according to an embodiment, the first and second protective layers 160 and 170 are respectively formed on the surfaces of the first and second magnetic sheets 140 and 150 to prevent foreign substances from being adsorbed to the magnetic sheet. These can be further stacked. In this case, the first and second protective layers 160 and 170 may be prepared while being attached to the surface of each magnetic sheet when the first and second magnetic sheets are manufactured. First and second extension portions 181 and 182 may be further formed on the edge portions of the first and second protective layers to be connected to external terminals.

4 to 6 are views illustrating a manufacturing process of a multilayer power inductor according to an embodiment of the present invention, respectively.

First, referring to FIG. 4 , looking at the manufacturing process of a multilayer power inductor according to an embodiment of the present invention, first, forming a laminate by stacking a plurality of magnetic metal sheets filled with soft magnetic metal powder (S10) , forming a circuit pattern on the first surface of the laminate (S20), forming a via hole in the center of the laminate, implementing the structure from the via hole forming process as a magnetic core, and expanding the via hole to a certain width (S30) ), inserting and assembling the coil assembly into the via hole and connecting the coil bridge of the coil assembly to the circuit pattern (S40), cutting to expose the circuit pattern (S50), the first side of the laminate and the second opposite to it It can be manufactured through a step (S60) of pressing and laminating the first and second magnetic sheets on each surface, and a step (S70) of forming external terminals on the side surfaces of the laminate and the first and second magnetic sheets.

In the step of forming the laminate (S10), a magnetic sheet is manufactured by casting an epoxy resin in which the soft magnetic metal powder is dispersed in the form of a tape, and a plurality of magnetic sheets in the form of a tape are laminated in multiple stages to correspond to a set thickness. Implement a laminate. In this case, when the configuration of the laminate is implemented as in the embodiment of FIG. 3c, the soft magnetic metal powder is divided into anisotropy and isotropy, an anisotropic soft magnetic metal powder is formed in the outermost layer, and isotropic soft magnetic metal is formed in the inner layer to form a powder.

In this case, the unit magnetic sheets constituting the laminate are Mo-permalloy, Fe-Si-Alalloy, Fe-Si alloy, and Fe-Si alloy. Si-Cr alloy), amorphous metal, nanocrystalline grains, and at least one soft magnetic powder of an amorphous powder, a solvent, a binder, a curing agent, a coupling agent, performing a curing accelerator ball mill (ball mill) mixing to form a magnetic slurry, The magnetic slurry may be manufactured by performing casting using a doctor blade method and drying the magnetic slurry to produce a magnetic sheet in a tape shape.

In the step of forming the circuit pattern ( S20 ), a copper foil is coated on the first surface of the laminate, and the copper foil is physically or chemically etched according to a design shape to form a circuit pattern.

Furthermore, in the step of forming the via hole ( S30 ), a via hole is physically formed in the vertical direction in the center of the laminate by using a punching machine. The shape of the via hole may be implemented as a structure in which a cross section is implemented in an elliptical shape as described above. In addition, the magnetic core may also be manufactured to have an elliptical cross-section having a major axis and a minor axis shorter than the lengths of the major axis and the minor axis of the via hole.

Of course, in this case, as described above, the by-product structure at the position of the via hole generated when the via hole is punched can be used as a magnetic core, and in order to provide an insertion space for the coil assembly later, a secondary punching machine is used for the via hole. It is possible to widen the diameter of the or use a drill to increase the diameter.

In the coil assembly step (S40), the coil assembly is inserted and assembled into the via hole of the laminate. The coil assembly may be manufactured by filling the soft magnetic metal powder to form a core, and winding the coil around an outer circumferential surface of the core so that the coil bridge is exposed to the outside.

The step of connecting the coil bridge of the coil assembly to the circuit pattern is to resistance welding the coil bridge to the circuit pattern, melting the copper foil layer by first resistance welding with a current of 200 to 300 A, a current of 500 to 600 A and fixing the coil bridge to the circuit pattern by secondary resistance welding with a furnace.

In the cutting step S50, the laminate is cut so that the circuit patterns disposed on both sides of the via hole become one set. At this time, the side surface of the circuit pattern is exposed to the outside so that it can be in contact with the external terminal.

The step of press-stacking the first and second magnetic sheets (s60) may further include forming first and second protective layers on the surfaces of the first and second magnetic sheets, respectively.

In the step of forming the external terminal ( S70 ), the external terminal is formed by applying a conductive paste to the side surfaces of the laminate and the magnetic sheet so as to be electrically connected to the circuit pattern exposed to the outside. The external terminal and the circuit pattern can secure a sufficient contact area with each other. In addition, this step of forming the external terminal (S70) may further include forming a first extension part and a second extension part on a part of the upper surface of the first protective film and a part of the lower surface of the second protective film to be connected to the external terminal, respectively. can The first extension part and the second extension part may be formed integrally with the same material as the external terminal.

Hereinafter, an example of a manufacturing process of a power inductor according to an embodiment of the present invention will be introduced with reference to FIGS. 5 and 6 based on the process described with reference to FIG. 4 .

[Example]

1) Preparation of a laminate

Soft magnetic powder made of metal (e.g., sandust, silicon steel, iron powder, etc.) is mixed with solvent (ethanol (EtOH), MEK, toluene), binder, hardener, coupling agent, and hardening accelerator, and the ball mill Mixing is performed to prepare a magnetic slush.

The binder is a thermosetting resin and an epoxy resin is applied. A small amount of cresol novolac or halogen-free epoxy can be added to the binder for physical properties such as heat resistance and strength of the magnetic metal sheet. To increase the flexibility of the sheet, rubber-based, polyurethane, and modified rubber One or more of the epoxies may be added in a predetermined amount.

As a curing accelerator, 2-methylamidazole or dicyandiamide can be applied, and as a curing agent, diaminodiphenyl methone, 3.3 diamino diphenyl sulfone ( 3.3 Diamino Diphenyl sulfone) in consideration of the curing reaction, an appropriate curing agent is selected, an equivalent ratio is added, and a coupling agent is added to improve bonding properties.

After adding an appropriate amount of magnetic metal powder, binder, epoxy resin, curing agent, coupling agent, and curing accelerator to the Ball Mill, toluene/MEK(Methyl Ethyl Ketone)/EtOH(Ethanol) 1:1: After adding a solvent of an appropriate level for easy casting to the solution mixed with 1, mix and disperse for a sufficient time to prepare a magnetic slurry.

Then, after vacuum defoaming the magnetic slurry in a defoaming tank for about 2 hours, casting is performed to a desired thickness using the Doctor Blade method, and the solvent is dried at about 110° C. Thus, a B-Stage state epoxy (Epoxy) metal magnetic sheet is produced by tape casting (S110). In this case, temperature control is important during casting, and a sheet having an appropriate strength can be realized by controlling an appropriate amount of the curing accelerator.

In order to apply the cast magnetic sheet to the lamination process, a slitting process is performed to have a preset line width, and a metal magnetic sheet is manufactured by cutting by a set length using a cutting device. A plurality of cast magnetic sheets are laminated to a set thickness using a laminator (refer to FIG. 3b ). In this case, the magnetic sheet disposed on the outer shell may include anisotropic soft magnetic metal powder, and the magnetic sheet stacked inside may include a structure including isotropic soft magnetic metal powder (see FIG. 3c ).

At this time, the upper surface of the magnetic sheet disposed on the uppermost layer among the unit magnetic sheets of the laminate is coated with a copper foil having a thickness of 17 to 30 μm so that it can be processed into a circuit pattern. The copper foil is chemically etched to form a circuit pattern of a set shape.

A via hole is formed in the center of the laminate in which a plurality of magnetic sheets are stacked using a punching machine. In this case, the shape of the via hole has a cylindrical structure, so that the cross section can be implemented as an elliptical structure. In addition, the cylindrical structure with an elliptical cross-section from which the via hole is formed can be used as a magnetic core later, and then the via hole is processed to have a wider diameter than the initially implemented via hole by working again with a drilling machine or a punching machine. Of course, if this process is implemented to have a double-structured punching blade depending on the shape of the punching machine, the magnetic core structure and the via hole expansion may be simultaneously implemented in one punching process. In this case, the via hole may be formed between the circuit pattern and the adjacent circuit pattern.

Next, the coil assembly is inserted into the via hole of the laminate and assembled, and the circuit pattern and the coil bridge are fixed by resistance welding. When resistance welding a coil magnetic core to a circuit pattern, first weld it with a current of 200~300A to melt the copper foil properly, then increase the current to 500~600A again to fix the coil bridge on the circuit pattern ( 6).

When resistance welding circuit patterns and coil bridges, if the primary current is less than 200A, it is not effective to remove the copper foil. This may cause a problem in which the DCR resistance rises. The initial DCR resistance of the coil wound around the magnetic core is 200~300mW. When the adhesion with the circuit pattern is secured, the DCR resistance between the circuit patterns to which the coil is attached is maintained at the level of 200~300mW. up to 700 mW. Therefore, the amount of current applied primarily is most preferably between 200 and 300A.

In addition, when the secondary current exceeds 700A, it is effective to secure the adhesion between the coil bridge and the circuit pattern, but the heat generated by the high current affects the polymer resin between the magnetic sheets, which can deteriorate the polymer resin. . When the high-pressure process is applied after lamination of the first and second magnetic sheets, the deterioration of the polymer resin causes energization due to contact between the powders, which may affect the frequency drop at high frequency, which is the final inductor characteristic. Therefore, when the secondary current is applied, the preferred amount of current is 500 ~ 600A. In addition, it is possible to reduce welding defects by performing additional welding using a laser after resistance welding.

The size of the tip used for resistance welding is preferably between 1.5 and 2.0 mm. For example, if the size of the tip is too small (1.2mm x 1.2mm), the adhesion between the circuit pattern and the coil bridge is low, and the insertion may be wrong during lamination of the first magnetic sheet, and if the size of the tip is too large (2.5mm) x 2.5mm) There may be a problem in that resistance welding is performed on the coil bridge mounted on a circuit pattern other than the set circuit pattern. In addition, it is preferable to maximize the attachment area by performing resistance welding at the angle of the tip perpendicular to the circuit pattern.

Then, an individual inductor panel is manufactured by performing a process of cutting using a cutter (C) so that the circuit pattern is exposed to the outside (refer to FIG. 6).

After the cutting process is performed on the inductor panel, water, abrasive balls, and abrasive accelerator are added in an appropriate amount, and then a ball mill is performed to remove some rust from the edges and surface and to make the surface roughness uniform. The polished product is immersed in EtOH to remove foreign substances in the ultrasonic cleaner, and then wash and dry for a sufficient time.

Thereafter, the first magnetic sheet and the second magnetic sheet coated with the first protective film and the second protective film, respectively, are disposed on the upper and lower sides of the laminate and the coil assembly, and heating conditions of 130°C ± 20°C using a hot press Under the pressure of 0.4ton ~ 2ton laminate hardening.

Next, the side surface of the laminate, the upper surface of the first protective film, and the lower surface of the second protective film are coated with Ag, Cu, or Ni paste to perform a termination process to form external terminals. In the case of the termination process, it is ok to apply Ag or Cu paste, which has a relatively low viscosity and excellent adhesion, and has no relation to conductivity, so cheap Ag or Cu paste.

After the external terminals are formed, the power inductor is manufactured by thermally curing the coil within about 200°C for about 1 hour in a nitrogen curing furnace to prevent oxidation.

As described above, in one embodiment, external terminals are formed on both sides of the first and second magnetic sheets and the laminate. The external terminal can be used as an external electrode of the power inductor because the coil bridge positioned inside the stack is physically and electrically connected to the resistance-welded circuit pattern.

In the detailed description of the present invention as described above, specific embodiments have been described. However, various modifications are possible without departing from the scope of the present invention. The technical spirit of the present invention should not be limited to the above-described embodiments of the present invention, and should be defined by the claims as well as the claims and equivalents.

100: power inductor 110: laminate
111: via hole 120: circuit pattern
121: welding 130: coil assembly
131: magnetic core (core) 132: coil

Claims (11)

a laminate having a first surface and a second surface opposite to the first surface and having a via hole disposed in the center thereof;
at least one circuit pattern included in the laminate to be adjacent to the via hole;
a coil assembly inserted and coupled to the via hole, the coil assembly including a coil wound around a magnetic core, and a coil bridge connected to the circuit pattern;
and an external terminal disposed on a side surface of the laminate to be connected to the circuit pattern; and
The shape of the cross section of at least one of the via hole and the magnetic core is formed to have a structure of a single closed curve having a major axis and a minor axis,
The ratio of the length of the minor axis of the cross section of the via hole to the length of the minor axis of the cross section of the magnetic core is 1: 0.8 to 0.9,
Stacked Power Inductor.
The method according to claim 1,
A multilayer power inductor having an elliptical cross-section of at least one of the via hole and the magnetic core.
The method according to claim 1,
A multilayer power inductor having an elliptical cross section between the via hole and the magnetic core.
The method according to claim 1,
The via hole has an elliptical cross-section,
A multilayer power inductor having a circular cross-section of the magnetic core.
The method according to claim 1,
The cross section of the via hole is circular,
A multilayer power inductor having an elliptical cross-section of the magnetic core.
The method according to claim 1,
A multilayer power inductor having at least two areas in which an outer surface of the coil on an outer peripheral surface of the magnetic core and a portion of an inner surface of the via hole contact each other.
delete The method according to claim 1,
A multilayer power inductor in which the multilayer body and the magnetic core are made of the same material.
9. The method of claim 8,
The laminate is
It has a structure in which a plurality of magnetic sheets filled with soft magnetic metal powder are stacked,
The magnetic core is a multilayer power inductor having a stacking structure made of the same material and in the same stacking order as that of the multilayer body.
10. The method of claim 9,
The laminate is
The soft magnetic metal powder included in the outer magnetic sheet disposed on the outermost layer among the plurality of magnetic sheets to be laminated has anisotropy,
A multilayer power inductor having isotropy in the soft magnetic metal powder included in the inner magnetic sheet disposed inside the plurality of stacked magnetic sheets.
The method according to claim 1,
first and second magnetic sheets respectively pressurized to the first and second surfaces of the laminate;
The multilayer power inductor further comprising a first passivation film and a second passivation film disposed on surfaces of the first and second magnetic sheets, respectively.

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