KR20070032259A - Ultra-thin flexible inductor - Google Patents

Abstract

Known SMT parts usually have a thickness of about 1 mm and are not flexible. The coils of the inductor according to the invention are preferably realized in the substrate since they use kappa layers already present in the substrate. Thus, thin film layers of high permeability material are deposited on top and bottom of the substrate. These layers are built to form the magnetic core of the inductor. Advantageously, the inductor can be provided with a very small drying height.

Description

INDUCTOR AND INDUCTOR MANUFACTURING METHOD {ULTRA-THIN FLEXIBLE INDUCTOR}

The present invention relates to inductors and methods of manufacturing inductors.

In many of today's electrical devices such as mobile communication devices, a voltage different from that provided by a battery or the like is required. In order to convert the voltage efficiently, an inductor is required. Today, surface mount (SMT) inductors are used. These are provided by various manufacturers. Such typical SMT inductors include thin drums of sintered ferrite. The diameter of the core can be approximately 4.3 mm and the height of the core can be approximately 1 mm. The coil is formed by thin copper wire wound between the top and bottom of the core. Such SMT inductors are usually provided with plastic fixtures with contacts for mounting the device on a printed circuit board (PCB).

Such SMT inductors are not only complicated and expensive to manufacture, since plastic fixtures usually need to be provided and their cores need to be specially shaped to have large aspect ratio gaps to accommodate lead windings. In addition, due to the addition of plastic fixtures, the dry height of the SMT inductor is in the 1mm range, which is too large for space-sensitive applications such as mobile phones.

It is an object of the present invention to provide an inductor having a reduced thickness.

According to a preferred embodiment of the present invention, the above-described object is an inductor as set forth in claim 1 comprising a substrate having a first side and a second side, one coil embedded in the substrate and one core. Can be achieved by The core includes a first soft magnetic metal film and a second soft magnetic metal film disposed on the first side and the second side of the substrate, respectively, the coil being at least partially covered by the first metal film and the second metal film. do.

In other words, according to this embodiment of the present invention, two thin film metal layers are provided on the sides of the substrate including the coil. Thus, advantageously, an ultra thin inductor with integral coils can be provided. Moreover, according to this embodiment of the present invention, this inductor is simple in design and can be manufactured at reduced cost. It is not necessary to provide a drum core having a special shape. This makes the inductor according to the invention suitable for mass production. Advantageously, this inductor is very reliable because the magnetic core consists of a metal film provided on the substrate. Reliability can be increased because no soldered connection between the inductor and the substrate is required.

According to another embodiment of the invention as described in claim 2, the coil is a kappa layer built on the substrate. According to this embodiment of the present invention, a substrate already containing a kappa layer such as a PCB can be used. Thus, the coil can be formed during the same processing step while other circuit structures in the PCB are formed. Thus, this coil is "for free" when providing other circuit structures, since the kappa material must be provided in any case within this substrate and the manufacturing process to build these kappa layers is required in any case. .

Moreover, since this coil includes a kappa layer built up in the substrate, a complicated coil layout can be obtained by wet chemical etching or the like. Such complex coil layouts may be necessary, for example, to manufacture transformers or intermediate connections. Due to this, circuit typologies may be possible, whereby compiled into a complex coil is used instead of two or more simple inductors. This may advantageously reduce the number of components and further reduce the size of the circuit comprising such components.

According to another embodiment of the invention as described in claim 3, the metal films are laminated to the first and second sides of the substrate. Due to the metal film being laminated to the substrate, an inductor is provided, which is an integral part of the substrate or PCB. Due to the lamination of the metal film to the substrate, the inductor can be improved in reliability. In addition, due to the lamination, no soldering interconnect is needed, which further improves reliability and further reduces manufacturing costs.

According to another embodiment of the invention described in claim 4, the metal films consist of high permeability metals such as μ-metals, amorphous metals and nanocrystalline metals. Since these high permeability metal films are ten times higher than typical ceramic ferrites, and the saturation magnetic flux density can be used with a permeability of 10,000 or more, which is about five times higher than typical ceramic ferrites, the magnetic core, i. Inductors can be provided.

According to another embodiment of the invention described in claim 5, the core plates, i.e. the metal films, are in close proximity together so that the distance between them is an air gap in the magnetic path that occurs in the core while the inductor is operating. Can be regarded as. Therefore, according to this embodiment of the present invention, a thin substrate having a thickness of preferably 1.2 mm or less or 1 mm or less is applied.

According to another embodiment of the invention described in claim 6, the substrate is a flexible substrate. Because of this, and because the metal films do not break like sintered ferrite or the like, refractive and flexible inductors can be provided. Moreover, the thin thickness of the magnetic core adds to the flexibility of the inductor, in accordance with this embodiment of the present invention.

According to another embodiment of the invention described in claim 7, slits are provided in the metal films. Advantageously, these slits are arranged such that eddy currents occurring in the metal films while the inductor is operating are minimized or prevented. According to one feature of this embodiment of the invention, the slits are arranged as perpendicular to the possible eddy current flow direction. Since the eddy current used usually flows substantially perpendicular to the magnetic field, according to another feature of this embodiment of the present invention the slits are arranged substantially horizontally in the direction of the magnetic flux occurring in the inductor during operation. Because of this, the possible eddy currents are minimal, while the slits only give a very small impact on the magnetic flux. In the case where a circular inductor is provided, according to another feature of this embodiment of the present invention, since the magnetic flux is radially oriented in the circular inductor, the slits are disposed in the radial direction.

According to another embodiment of the invention as described in claim 8, the number of slits increases radially outward of the magnetic core, ie outward of the circular metal films. Advantageously, these slits are very narrow.

According to another embodiment of the invention as described in claim 9, further slits are provided in the metal films perpendicular to the direction of the magnetic flux that occurs in the core during the operation of the inductor. Advantageously, these slits can lower the magnetic flux and inductance of the inductor. This may be advantageous in applications where the inductor should not be saturated.

According to another embodiment of the invention as described in claim 10, a multilayer inductor is provided over a plurality of film metals, each stacked on each other. Advantageously, this is allowed in inductors with higher magnetic flux in the core. Advantageously, such multilayer inductors according to this embodiment of the present invention can be manufactured at low cost.

According to another embodiment of the invention as described in claim 11, the widths of the slits provided in the metal films vary in different layers of metal films stacked on each other. According to one feature of this embodiment of the invention, the inner layers are provided with larger slits than the outer layers, which can advantageously allow uniform distribution in the core.

According to another embodiment of the present invention as described in claim 12, a method of manufacturing an inductor is provided wherein first and second metal films are laminated to sides of a substrate comprising a coil embedded in the substrate. do. Advantageously, according to this embodiment of the present invention, a very simple manufacturing method for producing an ultra thin inductor is provided. Claims 13 and 14 provide an embodiment of yet another method according to an embodiment of the invention as described in claim 12.

As an aspect of an embodiment of the present invention, it can be seen that an inductor is provided that includes a substrate having a buried coil and metal films disposed on both sides of the substrate forming a core of the inductor. According to one feature, the coil of inductors may be made by kappa tracks of the substrate, which may be a PCB or flex foil. Thus, the core may consist of thin, high permeability metal films that can be built and stacked into a substrate. Advantageously, this can reduce the dry height of the inductor while not expanding the footprint area compared to known methods. Moreover, the use of manufacturing such inductors can be reduced.

The foregoing and other features of the invention will be apparent from and elucidated with reference to the embodiments described below.

Embodiments of the present invention are described as follows with reference to the following drawings.

1 shows a cross-sectional view of an inductor according to a first embodiment of the present invention.

2 illustrates an embodiment of a coil layout that may be used in the inductor of FIG.

3 shows another embodiment of a coil layout that may be used in the inductor of FIG. 1.

4 is a top view of an embodiment of a magnetic core layer, illustrating a metal film with radial slit and bottom coil in an upper kappa layer in accordance with an embodiment of the present invention.

5 shows a cross-sectional view of different fabrication states of a second embodiment of an inductor according to the invention.

6 shows a cross-sectional view of the manufacturing states of the third embodiment of the inductor according to the invention.

7 shows a sectional view of a fourth embodiment of an inductor according to the invention.

8 shows a sectional view of a fifth embodiment of an inductor according to the invention.

9 illustrates a flexible foil with a coil according to an embodiment of the present invention that may be used as an example in the inductors of FIGS. 1, 5, 6, 7 and 8.

FIG. 10 shows a circular metal film that can be used for the core of the inductor shown in FIGS. 1, 5, 6, 7 and 8.

11 illustrates the flexible foil with the coil of FIG. 9 and the flex inductor of FIG. 10 disposed on a flexible substrate in accordance with one embodiment of the present invention.

1 shows a cross-sectional view of a first embodiment of an inductor according to the invention comprising a substrate 2 having a first side and a second side. Coils 6 and 8 are provided in this substrate 2. These coils 6 and 8 are embedded in the substrate 2 and are integrated with the substrate 2. The core of this inductor 2 is formed by soft magnetic metal films disposed on the first and second sides of the substrate 2 so that the coils 6, 8 are at least partially covered by the metal films 4. The soft magnetic metal films 4 disposed on the substrate 2 are circular. The thickness of the metal films 4 can be very thin, for example in the range of 25 μm to 100 μm. However, it is also possible to use metal films having a thickness in the range of 50 μm to 150 μm or 15 μm to 75 μm. These metal films may be made of a high permeability metal material having a permeability of 10,000 or more. Such permeability is ten times higher than that of a typical ceramic ferrite. Moreover, according to one feature of this embodiment of the present invention, the flux saturation of this material is nearly five times higher than for ferrite. Advantageously, this allows the magnetic core, ie the metal films 4, to be made much thinner than the magnetic core made of sintered ferrite. According to one feature of this embodiment of the invention, these metal films 4 are made of a material selected from the group consisting of μ-metals, nanocrystalline metals and amorphous metals. All three materials can be obtained from the Vakuumschmelze in Hanau, the Federal Republic of Germany. Amorphous metals, for example VitroVac, can be used, which can also be obtained from Vakuumschmelze, Hanau, Federal Republic of Germany.

Advantageously, μ-metal is the best known type. It only has moderate hysteresis losses. VitroVac has much lower hysteresis losses and nanocrystalline metals have the lowest hysteresis losses of any of the materials described above and thus can be a material of choice in the preferred embodiment of the present invention. From Vakuumschmelze, these materials can be obtained as metal films with thicknesses ranging from 25 μm to 50 μm and up to several hundred μm.

Advantageously, since the coils are embedded in the substrate 2 and are themselves used as part of the component, i.e., the inductor, the total building height 14 of the inductor can be significantly reduced compared to conventional SMT components. . For example, the total dry height 14 can be achieved in millimeters or less. Even lower drying heights of 200 μm or less are feasible.

According to one aspect of this embodiment of the invention, the inductor shown in FIG. 1 has the same length and width as, for example, a conventional 10 μH SMT inductor. Therefore, the integrated inductor according to this embodiment of the present invention can be used immediately in place of the SMT inductor in the same area. As described above, since the thickness of the core films 4 can be lowered to 0.025 mm, the total thickness can be reduced to 200 mu m or less.

Furthermore, as can be seen in Fig. 1, two inductors 6 and 8 are provided, which can preferably be realized as kappa layers.

Coil layouts that can be used as the coils 6, 8 are shown in FIGS. 2 and 3 and described next.

Reference numeral 10 in FIG. 1 denotes a kappa track that can be used for interconnection.

The metal films 4 laminated to the thickness of the substrate 2 and thus to the sides of the substrate 2 can be regarded as the air gap in the magnetic path where the distance between the metal films is generated in the magnetic path during operation of the inductor. It can be chosen to be sufficient. Thus, preferably, a thin substrate 2 is used, for example a flex foil, so that this inductor does not have too large an "air gap", ie between too large metal films 4. Do not have a distance of.

According to one feature of this embodiment of the invention, the substrate 2 is a flexible substrate, such as a refractive foil, and because the metal films 4 are used and are not sintered ferrite as is known, they are flexible and flexible. Inductors can be provided. This flexibility is further improved because the thickness of the magnetic core, ie the metal films 4, becomes very thin. Advantageously, therefore, a flexible inductor according to one aspect of this embodiment of the present invention may be used in variable electronics such as bendable lamps for apparel, medical electronics, flexible displays or vehicles. Moreover, refractive foil inductors with integrated coils and flexible magnetic cores can be particularly advantageous for mobile phone display circuits.

Reference numeral 12 in FIG. 1 denotes slits in the upper metal film 4. According to one feature of this embodiment of the invention, such slits 12 are provided in both metal films 4 which form the core of the inductor. However, it is possible to provide these slits 12 only on one metal film 4 of the inductor.

The slits 12 are provided to overcome the potential disadvantage of high permeability metal films 4, in which the material of these films is highly conductive. This causes the induction of large eddy currents in the films 4. This eddy current can cause unnecessary losses and can also degrade the inductor's inductive characteristics.

According to one feature of this embodiment of the invention, the flow of such eddy current is prevented or reduced by introducing the slits 12 in the metal magnetic core, ie in the metal films 4.

The slits 12 may be disposed perpendicular to the direction of the eddy current flow that occurs while the inductor is in operation, or may be arranged to prevent a decrease in the eddy current flow. The reduced eddy current flows perpendicular to the magnetic field in the inductor during operation. Therefore, the slits 12 may preferably be arranged in a direction substantially parallel to the direction of the magnetic flux. Due to this, the eddy current can be minimized while the slits 12 only give a very limited impact on the magnetic flux that occurs in the core during the operation of the inductor. In the circular inductor as shown in Fig. 1, the magnetic flux in the core is oriented radially. For this reason, as shown in FIG. 1, it is arrange | positioned in a radial direction.

The width of the slits should be as small as technically possible. To estimate, the widths of the remaining core segments must be smaller than the penetration depth because high frequency currents tend to flow on the surface or edge of the conductor. Since the implementation of the smallest width is also limited due to technical constraints, a layer as shown in Fig. 1 is preferred, where the number of slits goes out of the magnetic core, ie out of the magnetic films 4. Increase radially

As described above, the metal films 4 may be laminated to the substrate 2, such as a refractive foil. This can be done in the same way as the stacking of kappa layers 2, such as a refractive foil. In order to improve the adhesion of the metal films to the surface of the refractive foil, the metal film is for example deposited on the substrate 2 by silicidation on each surface.

Apart from the aforementioned applications of these inductors, such inductors can be a power converter as one preferred application since such inductors are preferably used for low frequency applications such as 10 MHz or less.

2 and 3 show a top view of a coil layout according to one embodiment of the invention when used for the coils 6, 8 (ie, kappa layers 6, 8) of the inductor shown in FIG. 1. Illustrated. As can be seen in FIGS. 2 and 3, the coils are helical. Comparing the winding directions of Figs. 2 and 3, according to one feature of this embodiment of the present invention, the winding directions of both layers are opposite to each other. In FIG. 2, the winding direction is clockwise while in FIG. 3, the winding direction is counterclockwise.

The coil layout shown in FIGS. 2 and 3 can be used to form a 10 μH inductor realized with two kappa layers in a standard to have an 80 μm track width and an 80 μm track distance. As shown in Fig. 1, two helices shown in Figs. These are interconnected with each other by vias between the contact devices 16 and 18. Such a coil layout can be particularly advantageous for use in, for example, mobile phone display circuits. Contact devices 16 and 18 lying outside of the spiral may be used for further interconnection, such as the two kappa tracks 10 of FIG.

Coil layouts can be realized in kappa layers by, for example, wet chemical etching, photography processes, and suitable fabrication processes, thereby obtaining complex coil layouts such as transformers. Moreover, as shown in Figs. 2 and 3, intermediate connections can be realized by a bias or the like. This allows a circuit arrangement where only one component with a complex coil is used in place of two or more simple inductors, which is advantageous for reducing the number and size of components in the circuit.

4 shows a top view of a circular metal film 20 comprising a slit 22 and a lower coil 24 that is a helical coil. The film 20 is disposed on the substrate 26 and the coil 24 is embedded in the substrate 26.

As can be seen in FIG. 4, slits are arranged which extend radially outward of the membrane metal 20. Moreover, the number of slits increases radially outward of the magnetic core, membrane metal 20 so that the slits 20 have different lengths.

The slits 20 are disposed perpendicular to the direction of the eddy current occurring during the operation of the inductor. Since the induced eddy current flows perpendicular to the magnetic field, the slits 22 are preferably in the direction of the magnetic flux oriented radially in the circular inductor with the circular metal film 20, as shown in FIG. It should be positioned substantially perpendicular to.

5 shows a cross-sectional view of different fabrication states of a second embodiment of an inductor according to the invention.

The top fabrication state shown in FIG. 5 shows a refractive foil with a substrate 28, a so-called kappa coil 30. The second state shows two high permeability metal films 32 stacked in a foil with kappa coil. Reference numeral 34 in FIG. 5 denotes an adhesive and insulating material sandwiched between the refractive foil 28 having the kappa coils 30 and the high permeability metal film 32, respectively.

5 shows a final inductor according to the second embodiment of the present invention, in which a high permeability metal film 32 is constructed to form the magnetic core 36 constructed.

The refractive foil with kappa coil 30 shown in the first state of FIG. 5 can be manufactured in a known manner. For example, by stacking kappa tracks, a kappa coil 30 is formed towards the refractive foil. However, kappa coils can also be formed by a photography process and etching.

A high permeability metal, such as μ-metal, nanocrystalline metal or amorphous metal, can then be laminated to either side of the refractive foil 20 with kappa coils 30 to form a second manufacturing state. . Preferably, as shown in FIG. 4, the lamination allows the adhesive and / or insulating material to be sandwiched between the high permeability metal film 32 and the kappa coils 30.

In order to build a high permeability metal film to form the built magnetic core 36, wet chemical etching can be performed, which is suitable for high volume manufacturing. With the new metal, wet etching such as a kappa layer can be performed. In particular, the same photographic process and the same solvent can be used.

Instead of wet chemical etching, a high permeability metal film 32 can be constructed by cutting. Building the high permeability metal film 32 to form the built magnetic core 36 involves forming slits.

6 shows a cross-sectional view of a manufacturing state of a third embodiment of an inductor according to the present invention. In FIG. 6, the same reference numerals are used to indicate the same or corresponding components in FIG.

As can be seen from FIG. 6, the first manufacturing state shown in FIG. 6 is obtained by laminating the high permeability metal films 40 added in FIG. 6 to the final manufacturing state shown in FIG. 5 by the adhesive material and the laminating material 38. Except as noted above, it corresponds to the final manufacturing state shown in FIG. Thus, in the second manufacturing state shown in FIG. 6, additional high permeability metal films 40 were built by wet chemical etching or the like to form the built core 42. As can be seen from this second fabrication state, the inductor is provided with two-layer cores 36 and 42.

Further cores 44 constructed by adding another additional high permeability metal film and building this additional high permeability metal film are added to the inductor to provide multilayer cores.

Such multilayer cores are particularly advantageous for applications where conductors are required to have higher magnetic flux in the core. The high magnetic flux in the core simply increases the thickness of the magnetic core due to the skin effect of the magnetic flux as the flow only occurs off the surface of the core layers and the inside of the core is out of the field and thus not used. It may not be realized by itself. In accordance with this surface effect, the use of several thinly stacked insulating layers of high permeability films will significantly increase the magnetic flux in the core.

As can be seen from FIGS. 5 and 6, fabricating such multilayer inductors is a simpler one layer, as shown in the final fabrication state shown in FIG. 5 except that further removal and construction steps must be performed. Similar to manufacturing an inductor.

As an alternative to the manufacturing method proposed by FIG. 6, all layers can be etched in one step. However, an insulating adhesive must be provided between the layers that can be constructed with the same etching solvent used to etch the high permeability metal film layers.

7 shows a cross-sectional view of an inductor according to a fourth embodiment of the invention. As can be seen from FIG. 7, the coil layers 52 are disposed on a substrate 50 in which the high permeability metal film layers 54 constructed are stacked to form the magnetic core of the inductor. As can be seen from the cross-sectional view of FIG. 7, the core, ie the high permeability metal film layers 54 constructed, are provided in the slits 56. According to one feature of this embodiment of the invention, this slit 56 is perpendicular to the direction of magnetic flux occurring within the core. Preferably, these slits 56 lower the magnetic flux and inductance of the inductor according to this embodiment of the present invention. This may be advantageous in any coil layout where it is necessary to ensure that the inductor is not saturated.

8 shows a sectional view of a fifth embodiment of an inductor according to the invention. As can be seen from FIG. 8, this inductor is a multilayer inductor comprising three core layers 58 on each side of the two coil layers 60 provided on the substrate 62. As can be seen from FIG. 8, the slits 64 are provided in the core layers 58.

In some cases the magnetic flux may be concentrated in the innermost core layer 58, ie core layers 58 proximate the coil layers 60. This may occur because these layers 58 may have a shielding effect on the outer layers. This may occur especially when the insulator provided between the core layers 58 is too thick.

According to one feature of this embodiment of the invention, slits 64 perpendicular to the flux direction are formed in the core layers 58. As a result, the magnetic flux can flow to other, more outer layers to improve flux distribution over the layers. Advantageously, homogeneous flux distribution can be achieved. To further improve homogeneity, the widths of the slits can be varied in different core layers 58. In particular, the width of the slits in the inner layers 58 may be larger than the slit width of the slits 64 in the outer layers 58.

9 and 10 show samples of an inductor coil (FIG. 9) and a built flexible core (FIG. 10). The refractive foil with the kappa coil shown in FIG. 9 was made according to standard refractive foil procedures. This core (FIG. 10) was made of a 25 μm VitroVac high permeability metal foil by laser cutting. These core films were manually attached to the flux foil using a tesafilm adhesive tape.

FIG. 11 shows a view of a flux foil substrate comprising helical coils and a build core stacked thereon. As can be seen from Fig. 11, the flexibility of the inductor according to the present invention is very substantial.

Claims (14)

In the inductor, One substrate having a first side and a second side, One coil, and Contains one core, The coil is embedded in the substrate, The core includes a first metal film disposed on a first side of the substrate and a second metal film disposed on a second side of the substrate, wherein the coil is at least partially at least part of the first metal film and the second metal film. Covered by And the first and second metal films are soft magnetic bodies. The method of claim 1, And the coil is a kappa layer built in the substrate. The method of claim 1, The first and second metal films are high permeability metal films, And the first and second metal films are laminated to the first and second sides of the substrate. The method of claim 1, And the first and second metal films are made of at least one material selected from the group consisting of μ-metals, amorphous metals and nanocrystalline metals. The method of claim 1, And the thickness of the substrate and thus the distance between the first and second metal films is of a specification such that the distance can be regarded as an air gap in the magnetic path of the core. The method of claim 1, And the substrate is flexible. The method of claim 1, The first and second metal films are first slits, And the first slits are disposed substantially perpendicular to the eddy current flow occurring in the first and second metal films during operation of the inductor to reduce eddy current flow. The method of claim 7, wherein The kappa structures of the coil have the form of spirals, The first and second metal films are circular, And the number of said first slits in said first and second metal films increases radially. The method of claim 1, The first and second metal films have second slits, And the second slits are perpendicular to the direction of magnetic flux generated in the first and second metal films during operation of the inductor. The method of claim 1, A plurality of first and second metal films are disposed, The plurality of first metal films are stacked in a vertical direction, The plurality of second metal films are stacked in the vertical direction. The method of claim 10, Third slits are provided in the plurality of first and second metal films, The third slits are perpendicular to the direction of magnetic flux generated in the plurality of first and second metal films during operation of the inductor, Those disposed inside of the first and second metal films have third slits having a first width and those disposed outside of the first and second metal films have slits having a second width, The first width is greater than the second width. In the inductor manufacturing method, Providing a substrate having a first side and a second side, the coil being embedded in the substrate, and Stacking a first metal film on the first side of the substrate and a second metal film on the second side of the substrate so that the coil is at least partially covered by the first metal film and the second metal film Forming a core of And the first and second metal films are soft magnetic bodies. The method of claim 12, Constructing kappa layers to form the coil in the substrate. The method of claim 12, Providing first slits in the first and second metal films, And the first slits are formed by wet chemical etching or laser cutting.

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