Surface mount inductive coil element for mounting on a printed circuit board

Abstract

To provide a surface mount inductive coil element that is not easily broken and that passes a drop test. The coil element of the invention includes a monolithic core 1 having three mutually orthogonal winding guide structures and a plurality of connecting conductors 2 attached to the core 1. Each of the guide structures is formed around one of three orthogonal axes X, Y, and Z to arrange the three orthogonal conductive coils around the core 1. The connections IF2 connect each of the coils to conductive paths of the PCB and are embedded within the core 1, the core 1 being made of an injection moldable polymer body, the polymer body containing 70w%-85w% powdered magnetic charge, thereby providing magnetic inductance, ensuring electrical insulation between the connecting conductors 2, and providing thermal conductivity of 4W / mK or more.

Description

Technical Field

[0001] The present invention relates to inductive coil elements, and more particularly to inductive coil elements (also referred to as "inductive elements") designed to be mounted on a printed circuit board (PCB). In many cases, these components incorporate a mechanical interface (also referred to as a "conductor") for connection to the PCB. This mechanical interface is typically effected by means of PTH (Pin Through Hole) or SMT (Surface Mount Technology) pins / pads for low currents (e.g., currents used in the electronics industry).

Background Art

[0002] Generally, these inductive coil elements are composed of three elements. That is, a magnetic core, a base or bobbin that holds this magnetic core, and a coil or winding wound around the periphery of this magnetic core.

[0003] The materials of these three elements have various electrical (conductive) and magnetic (permeable) properties. The base or bobbin is made of a polymer material based on plastic technology (e.g., phenols, polyamides), has high insulation, can have pins / pads (PTH, SMT) mounted thereon, and the winding can be soldered and fixed. The base or bobbin thus has a structural function (the function of supporting and housing the magnetic core and the winding) and a functional function (the necessary electrical insulation function). On the other hand, the magnetic core is usually made of a metal-based material, an amorphous alloy or a crystalline alloy of this metal-based material, a metal oxide or a sintered (formed) powder or a consolidated powder of an alloy. These materials usually have a predetermined conductivity, but this increases eddy current and causes losses. Therefore, it is necessary to insulate the magnetic core from the winding and the printed circuit board. This is done by means of a plastic base or bobbin.

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

[0005] One of the inductive coil elements is, for example, a low-frequency winding antenna for RFID. This is used in a keyless entry system to guard against the risk of losing the key or the key becoming inoperable due to impact. That is, the inductive coil implemented in the key needs to withstand the impact during a fall.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide an inductive coil element (hereinafter also referred to as an "inductive element") that satisfies the following requirements. 1. Passing the industry-standard drop test. 2. Not requiring a base or bobbin for holding a magnetic core that can be mounted by SMT or PTH. 3. Having a low manufacturing cost of the inductive coil. 4. Not impairing predetermined requirements (inductance, Q factor, DC resistance, sensitivity).

[0007] The standard structure of the inductive coil element includes a non-conductive base or bobbin (usually made of a plastic material). The base or bobbin houses a magnetic core, and a coil / winding is wound around this magnetic core. This is disclosed, for example, in Patent Documents 1 to 4.

[0008] Furthermore, Patent Document 5 discloses a core assembly for a three-axis antenna. This core assembly includes a first core member having a main body around which an X-axis coil and a Y-axis coil are wound, a second core member having a main body around which the X-axis coil and the Y-axis coil are wound, and a bobbin having an annular portion. This annular portion disposes the first core member from one side and houses a part of the main body of the second core member from the other side. As a result, the main bodies of the first core member and the second core member are at least partially adjacent to each other.

[0009] Patent Document 6 discloses an inductive miniature element, first and second guide elements, and a coil plate. The inductive small element has a winding made of a ferrite material. This winding is realized as a flat and multi-sided component. Three windings are disposed on the winding element. As a result, the axes of the windings extend in three spatial directions orthogonal to each other. The first and second guide elements and the coil plate are non-conductive (made of a polymer material) and made of a non-ferromagnetic material. The winding element and the coil plate are disposed together, interconnected, adhered, and fixed by connecting means.

[0010] In order to prevent the core from separating from the base or the bobbin during an accident impact (where the wire may tear or break), in this field, a two-component structural adhesive (epoxy-based) is used alone or in combination with epoxy transfer injection molding. However, the manufacturing process of this inductive coil element is expensive and time-consuming. This is because the machines used are expensive. For example, an example of such a machine is an assembly machine having a heating oven or an epoxy injection molding machine having a precise and complex mold.

[0011] Furthermore, in many cases, a sheet made of impact-absorbing foam material is used to mitigate the impact during a drop test and prevent damage or disassembly of the components.

[0012] Patent Document 7 of the present applicant discloses a monolithic core configured to be connected to a printed circuit board (PCB). This connection is made through pin-through holes or surface-mounted pins / pads, and the core is further metallized. The monolithic core has a configuration that provides a path for winding the coil of the inductor and is extremely expensive, but there is a risk of core breakage and ferrite vulnerability. Furthermore, the conductivity of the core has limitations in solving the miniaturization of metallized ferrite, Fe oxide, and Ni oxide (which have low magnetic permeability but high electrical resistance).

[0013] In other words, these solutions / means must protect the components / elements from impact and avoid an increase in manufacturing costs.

[0014] Patent Document 8 discloses a soft magnetic substrate of a wireless power transmission device. This soft magnetic substrate has a side surface configured to accommodate a transmission coil. A groove adapted to the shape of this transmission coil is formed on the side surface. This side surface accommodates the first, second, and third transmission coils. The second transmission coil is arranged in parallel with the first transmission coil, and the third transmission coil is arranged on the first and second transmission coils. The groove has a wall. This wall surrounds at least a part of the outer periphery of each of the first, second, and third transmission coils. This soft magnetic substrate is integrally formed by injection molding the following synthetic components. The alloy components are *At least one of Fe-Si-Al alloy powder or flakes and Fe-Si-Cr alloy powder or flakes is 83-87 w%, *It contains 13-17 w% of at least one of polyvinyl (PolyVinyl)-based resin, polyethylene (PolyEthylene)-based resin, and polypropylene (PolyproPylene)-based resin. Patent Document 8, unlike the present invention, does not disclose or suggest an inductive element specially designed for surface mounting by utilizing the insulation characteristics of the substrate. This is clear from FIG. 6 of the same document and the related description.

[0015] Therefore, it is necessary to provide an inductive coil element that is inexpensive and difficult to break. Furthermore, even without a foam material, a shock absorber, a chip adhesive, etc., it is necessary to provide an inductive coil element that passes the drop test and can prevent the occurrence of an impact that damages the core when dropped, especially when mounted on a key or a mobile device.

[0016] In view of the above, an object of the present invention is to provide a new inductive element that passes the drop test, is flexible, difficult to break, has a simple manufacturing process, and can reduce the number of components from three to two. In addition, solution methods / means combining various technologies can also be implemented.

Means for Solving the Problems

[0017] To this end, the present invention comprises integrating a core element and a base element or a bobbin into a single monolithic core by injection molding. Thereby, an element for accommodating a connection conductor is provided. This element is ferromagnetic, has a stable structure, is insulating, has sufficient flexibility, can absorb impact energy, and is difficult to break.

[0018] The inductive coil of the present invention is an element for mounting on a printed circuit board. As is conventionally known, it has at least one winding groove and a plurality of connection conductors. The groove arranges the inductive coil around the monolithic core. The connection conductor is attached to the monolithic core and connects the conductive coil to the conductive path of the circuit board.

[0019] Characteristically, the monolithic magnetic core (also referred to as "monolithic core") is made of an injection moudable polymer body. This polymer body Magnetic body contains 70w%-85w% of (magnetic charge), provides an appropriate magnetic inductance, and ensures insulation between connection conductors. This connection conductor is included in the monolithic core and has a heat conductivity of 4 W / mK or more. The magnetic material is in powder form Magnetic body and contains.

[0020] In one embodiment, the inductive coiled element of the present invention includes a monolithic core included in (embedded in) an injection-molded polymer body. This monolithic core provides an appropriate magnetic inductance and is made of an injection-molded polymer body. This polymer body Magnetic body contains 70 w% to 85 w% (maximum value). This maximum value (upper limit) is selected so as to ensure insulation between the connecting conductors of the monolithic core. Magnetic body contains a magnetic material that is entirely or partly in powder form (micro-particles or nano-particles).

[0021] In one embodiment, this polymer body is formed from a PBM material, in particular a PBM material in the form of micro-particles or nano-particles (i.e., in powder form) having an appropriate initial magnetic permeability of an appropriate size. The PBM material is a polymer of PBT, PA66, LCP, Peek, polyimide, and includes a plus dispersant and a flame retardant additive. This polymer body contains 70 w% or more of ferrite or iron powder, micro-particles or nano-particles of a powdered ferromagnetic alloy. A novel core having a bobbin or base is obtained in the entire volume that the core occupied in the prior art.

[0022] The effective magnetic permeability of a core made of PBM is lower than that of a sintered core of the same material embedded in the standard structure of the inductive coiled element. The present invention solves the problems of the prior art Magnetic body by incorporating the volume of the base or bobbin in addition to the standard core volume into an injection-molded polymer body containing

[0023] thereby increasing the total volume of the magnetic core. Thus, sufficient magnetic permeability for the inductive coiled element and the sensitivity of the final product can be achieved.

[0024] To date, in the prior art, as the core, BPM materials have been considered technically unable to compete with conventional sintered materials. The reason for this is that the loss of density, fragment size, and particle size within the matrix will significantly limit or reduce the main variable targeted (i.e., magnetic permeability).

[0025] Magnetic body It is not clear that more than 80w% of this can also be obtained with PBM materials, and that PBM materials do not exhibit percolation phenomena.

[0026] The present invention utilizes the progress of polymer materials, extraction technology, and nanotechnology to enable vertical integration in the manufacturing process of cores and bases or bobbins, and also improves costs.

[0027] An example of these technologies is the availability of planetary zirconium ball milling and the increased availability of new mixtures (including materials with variable rheology performance that can be injection molded at high temperatures and pressures) using conventional plastic injection molding machines.

[0028] In addition, PBM integral components, unlike the above-described solutions based on monolithic cores, in addition to solving the above-mentioned drawbacks, when the core and base are injection molded, new shapes that cannot be obtained in the conventional manufacturing process of ferrite cores or sintered cores can be obtained. The conventional manufacturing process is a process of compressing and sintering in a furnace at a temperature of 1000°C or higher.

[0029] In one embodiment, all of the magnetic materials contained in the polymer body constituting the magnetic core are in powder form Magnetic body is.

[0030] As another configuration, Magnetic body includes a powdered magnetic material embedded in the polymer body and a solid sintered core made of a magnetic material. The solid sintered core is a non-powder core.

[0031] The solid sintered core has no protrusions and is between a flat element and a polyhedral element.

[0032] The sintered core occupies 15 w% (weight %) or 15 v% (volume %) or less of the entire monolithic core. In either case, Magnetic body is ferromagnetic particles of at least one of micro or nano size. In this case, the ferromagnetic particles of micro or nano size are either ferrite particles, iron powder or ferromagnetic alloy.

[0033] In one embodiment, within the polymer body Magnetic body The maximum ratio is 75 w%. The polymer body is made of a PBM material containing a dispersed additive or flame retardant material.

[0034] According to a particular embodiment, the monolithic inductive element of the present invention includes at least three winding grooves. These are part of a winding guide structure. Each winding groove is arranged around the monolithic core surrounding one of the X-axis, Y-axis, and Z-axis, which are three orthogonal axes. This enables three orthogonal conductive coils to be arranged around the monolithic inductive element.

[0035] In one embodiment, two of the three orthogonal winding guide structures are two orthogonal grooves respectively surrounding the monolithic core.

[0036] In one embodiment, the shape of the monolithic inductive element can be generated by a mold composed of two parts. That is, due to the shape of this monolithic core, when the two-part mold is opened, the core generated therefrom is taken out and the monolithic core is formed. For this purpose, it is preferable that the shape of the monolithic core has no grooves or recesses on its peripheral surface.

[0037] In other embodiments, the magnetic permeability of the inductive element can be further improved by a hybrid method. In the hybrid method, an inexpensive core of a simple shape (e.g., cube, sphere, tetrahedron, disc, cylinder) is placed in a mold. Then, a shape overmolded or over-injection molded by PBM is formed, which can provide the above functions. By the hybrid method, sensitivity and magnetic permeability are increased, cost is reduced, and resistance that can pass the drop test is obtained.

[0038] According to the present invention, the core can be incorporated into a recycling-oriented society, which is achieved by creating PBM pellets for injection molding from waste ferrite and other recycled cores.

[0039] Therefore, the present invention does not require the implementation of a ferrite sintering process. As a result, it can be changed from an old process that uses waste, is dirty, energy-intensive, and generates CO 2 to a new process of clean injection molding.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0041] The inductive element shown in FIG. 1 includes a heat-conductive monolithic magnetic body. This magnetic body is made of an injection-moldable polymer body containing a magnetic material. The Magnetic body content in the polymer body is between 70 w% and 85 w% (maximum value). This provides an appropriate magnetic inductance and ensures electrical insulation between the connection conductors 2 partially embedded in the monolithic core 1. The magnetic body includes a powdered magnetic body.

[0042] The shape of the magnetic core 1 is the standard shape of a plastic bobbin. That is, it provides orthogonal channels. These channels are arranged in the normal way around the windings of the inductive coil element.

[0043] The embodiment of FIG. 2 is generally similar to that of FIG. 1. FIG. 2 shows that a solid sintered core 3 made of a magnetic material is Magnetic body embedded in the polymer body as part of it. In this embodiment, the solid sintered core 3 is an inexpensive thin ferrite plate embedded in the mold. As a result, this ferrite plate is integrated with Magnetic body in a completely injectable polymer body.

[0044] In FIG. 3, the solid sintered core 3 is a ferrite cube. This cube is placed in the polymer body together with the magnetic body constituting the hybrid magnetic core. In this embodiment, the magnetic core is a corner protrusion dispersedly arranged in eight spaces defined between three orthogonal axes. The thickness of the solid sintered core 3 is between 0.5 mm and 1.5 mm.

[0045] The above description relates to an embodiment of the present invention. Those skilled in this technical field can conceive various modifications of the present invention, all of which are included in the technical scope of the present invention. The numbers in parentheses described after the components of the claims correspond to the component numbers in the drawings and are attached for the easy understanding of the invention and should not be used for limiting the interpretation of the invention (Article 4, Paragraph 24 of the Implementing Regulations of the Patent Law and "Remarks" 14(b) of Form 29-2). Also, even if the same number is used, the component names in the specification and the claims are not necessarily the same. This is for the reasons described above. "At least one or more", "and / or" are not limited to one of them. For example, "at least one of A, B, and C" may include not only "A", "B", "C" alone but also a plurality of them such as "A, B or B, C or further A, B, C". "At least one of A, B, and C" may be not only A, B, and C alone but also a combination of A and B or a combination of A, B, and C. "A, B and / or C" may include not only A, B, and C alone but also two of A and B or all of A, B, and C. In this specification, "including A" and "having A" may include things other than A. Unless otherwise specified, the number of devices or means may be singular or plural.

Explanation of Reference Signs

[0046] 1: Monolithic Core 2: Connection Conductor (Connection Interface) 3: Solid Sintered Core

Claims

1. In a surface-mounted inductive coil element for a printed circuit board, the surface-mounted inductive coil element includes a monolithic core (1), the monolithic core (1) has * three winding guide configurations orthogonal to each other, and * a plurality of connection conductors (2) attached to the monolithic core (1), each of the winding guide configurations is formed around one of three orthogonal axes, namely the X-axis, Y-axis, and Z-axis, and three mutually orthogonal conductive coils are arranged around the monolithic core (1), the connection conductors (2) connect each of the three conductive coils to the conductive paths of the printed circuit board and are at least partially embedded in the monolithic core (1), the monolithic core (1) is made of an injection-moldable polymer body, and the polymer body contains 70 w% - 85 w% of a powdered magnetic material, thereby providing magnetic inductance, ensuring electrical insulation between the connection conductors (2), and providing a heat transfer property of 4 W / mK or more. A surface-mounted inductive coil element for a printed circuit board, characterized by the above.

2. The magnetic material in the polymer body is a powdered magnetic material. The surface-mounted inductive coil element according to Claim 1, characterized by the above.

3. The magnetic material includes a powdered magnetic material and a solid sintered core (3) made of a magnetic material in the polymer body, and a hybrid magnetic core is formed. The surface-mounted inductive coil element according to Claim 1, characterized by the above.

4. The solid sintered core (3) has no protrusions and is between a flat element and a polyhedral element. The surface-mounted inductive coil element according to Claim 3, characterized by the above.

5. The solid sintered core (3) is 15 w% or less or 15 v% or less of the entire monolithic core (1). The surface-mounted inductive coil element according to Claim 3, characterized by the above.

6. The thickness of the solid sintered core (3) is between 0.5 mm and 1.5 mm. The surface-mounted inductive coil element according to Claim 4, characterized by the above.

7. The content ratio of the magnetic material in the polymer body is between 75 w% and 85 w%. The surface-mounted inductive coil element according to any one of Claims 1 - 3, characterized by the above.

8. The polymer body is made of a PBM material, and the PBM material includes a dispersant additive or a flame-retardant material. The surface-mounted inductive coil element according to any one of Claims 1 - 6, characterized by the above.

9. ​ The magnetic body is one or both of micro ferromagnetic particles and nano ferromagnetic particles The surface mount inductive coil element according to any one of claims 1 to 6, characterized in that.

10. The micro ferromagnetic particles or nano ferromagnetic particles include any or all of ferrite particles, iron powder, or ferromagnetic alloys The surface mount inductive coil element according to claim 9, characterized in that.

11. The monolithic core (1) has a shape that can be manufactured by casting with two molds The surface mount inductive coil element according to any one of claims 1 to 6, characterized in that.

12. The connection conductor (2) is a metal conductive element at least partially embedded in the polymer body The surface mount inductive coil element according to any one of claims 1 to 6, characterized in that.

13. The metal conductive element is a pin or pad for mounting The surface mount inductive coil element according to claim 12, characterized in that.

14. Two of the three winding guide configurations are two orthogonal grooves each surrounding the monolithic core (1) The surface mount inductive coil element according to any one of claims 1 to 6, characterized in that.

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