JP2013149824A - Manufacturing method of ferrite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a convenient ferrite sheet flexible in a direction other than vertical and lateral directions; for example, in an oblique direction, by firing a ferrite sheet plane even when a thin and flexible ferrite sheet is reliably divided into small pieces.SOLUTION: The manufacturing method of a ferrite sheet 1 comprises the steps of: forming plural holes 4 on at least one face of the ferrite sheet 1; firing the ferrite sheet 1; applying a protection sheet on at least one surface of the ferrite sheet 1; and dividing the ferrite sheet 1 using the plural holes 4.

Description

  The present invention relates to a method for manufacturing a ferrite sheet used for an antenna module such as an RFID or a non-contact charging module.

  Conventionally, a very thin magnetic sheet has been attached to the outer surface of the electronic component in order to block electromagnetic waves from the electronic component. This type of magnetic sheet has flexibility by being divided into a large number of small pieces having a specific width (for example, Patent Document 1).

  In (Patent Document 1), a ferrite sheet in which linear grooves intersecting vertically and horizontally are formed on the surface side is sandwiched between a covering sheet and a double-sided adhesive sheet, and the ferrite sheet is bent to break all the grooves. A sheet is formed.

JP 2009-182062 A

  However, in the method for manufacturing a ferrite sheet described in (Patent Document 1), since flexibility is provided only in the longitudinal direction and the lateral direction in which the grooves are formed, flexibility in other directions, for example, an oblique direction may be provided. It was difficult.

  Furthermore, the ferrite sheet is currently required to be thin. For example, in a ferrite sheet having a thickness of about 300 μm, it is particularly difficult to form a groove. That is, if the groove depth is as small as possible, the groove cannot be favorably broken. If the groove is made as deep as possible, the ferrite sheet is divided by the groove before firing, and the ferrite sheet cannot be fired in a flat shape. That is, since the ferrite sheet is thin, the range of allowable groove depth is narrow, and small variations in groove depth are not allowed. As a result, the entire groove could not be broken (divided) satisfactorily due to small variations in the groove depth.

  In view of the above problems, the present invention can be provided with flexibility in a direction other than the vertical and horizontal directions, for example, in an oblique direction, to manufacture a user-friendly ferrite sheet, and to reliably divide the thinned ferrite sheet into small pieces And even if it is a case where a softness | flexibility is provided, it aims at baking and manufacturing a ferrite sheet in planar shape.

  In order to achieve the above object, a method for producing a ferrite sheet according to the present invention is a method for producing a ferrite sheet, comprising: forming a plurality of holes in at least one surface of the ferrite sheet; A step of firing, a step of attaching a protective sheet to at least one surface of the ferrite sheet, and a step of dividing the ferrite sheet using the plurality of holes.

  According to the present invention, flexibility in a direction other than the vertical and horizontal directions, for example, an oblique direction can be provided, and a user-friendly ferrite sheet can be manufactured. Further, even when the thinned ferrite sheet is surely divided into small pieces and provided with flexibility, it can be fired into a flat shape.

The figure which shows the ferrite sheet in this Embodiment Schematic diagram showing a ferrite sheet in the present embodiment The principal part enlarged view of the ferrite sheet before dividing | segmenting into the small piece in this Embodiment The principal part enlarged view of the ferrite sheet after being divided | segmented into the small piece in this Embodiment Cross-sectional enlarged view of the hole in the present embodiment Manufacturing process flow chart of ferrite sheet in the present embodiment The figure which shows the formation method of the several hole part in this Embodiment Configuration diagram of antenna device in the present embodiment

  Invention of Claim 1 is a manufacturing method which manufactures a ferrite sheet, Comprising: The process of forming a some hole in at least one surface of a ferrite sheet, The process of baking the said ferrite sheet, The said ferrite sheet A method for manufacturing a ferrite sheet, comprising: a step of attaching a protective sheet to at least one surface; and a step of dividing the ferrite sheet using the plurality of holes, wherein the ferrite sheet is not in a vertical or horizontal direction. Thus, for example, a ferrite sheet that is easy to use can be manufactured. Further, even when the thinned ferrite sheet is surely divided into small pieces and provided with flexibility, it can be fired into a flat shape.

  According to a second aspect of the present invention, in the ferrite sheet, the ferrite sheet is divided at least between the plurality of hole portions and at least the hole portions closest to each other. According to the method for manufacturing a ferrite sheet, it is possible to manufacture a ferrite sheet that reliably and easily has flexibility in a direction other than the vertical and horizontal directions, for example, an oblique direction, according to the pattern and regularity of the hole.

  The invention according to claim 3 is the method for manufacturing a ferrite sheet according to claim 1 or 2, wherein the plurality of holes are arranged in a lattice pattern. Even when the ferrite sheet is regularly and surely divided into small pieces to provide flexibility, it can be fired in a flat shape.

  According to a fourth aspect of the present invention, in the ferrite sheet according to any one of the first to third aspects, the plurality of hole portions have a tapered shape in which the area of the upper surface portion is larger than the area of the bottom surface portion. In this manufacturing method, a more flat ferrite sheet can be formed. That is, it is difficult for irregularities to be formed on the ferrite sheet.

(Embodiment)
Hereinafter, a ferrite sheet and an antenna device using the same according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a ferrite sheet in the present embodiment, and is a photograph of the surface of the ferrite sheet 1. FIG. 2 is a schematic diagram showing a ferrite sheet in the present embodiment. FIG. 2A is a diagram illustrating the surface of the ferrite sheet, and FIG. 2B is a diagram illustrating a cross section of the ferrite sheet.

  The ferrite sheet 1 includes a magnetic body 2, a protective member 3 provided on at least one surface of the magnetic body 2, and a plurality of holes 4 provided on at least one surface of the magnetic body 2. It is divided using a plurality of holes 4. That is, for example, the plurality of holes 4 are divided at least between the holes 4 closest to each other.

  The magnetic body 2 is a sheet-like ferrite sintered body, and examples of the ferrite include Mn—Zn ferrite, Ni—Zn ferrite, and Mg—Zn ferrite. The magnetic body 2 is in the form of a sheet and has a thickness of 50 to 1000 μm, particularly 50 to 300 μm in the present embodiment. In the present embodiment, it is 100 μm. Moreover, the process of forming the hole part 4 of this Embodiment is applicable also to the following materials (magnetic sheet). That is, it may be a magnetic material such as amorphous metal, permalloy, electromagnetic steel, silicon iron, Fe—Al alloy, or Sendust alloy. Further, a magnetic material may be contained in the sheet-like resin material.

  The protection member 3 has flexibility and is made of plastic such as PET (polyethylene terephthalate). The magnetic body 2 divided into small pieces is maintained in a sheet shape so that the small pieces of the magnetic body 2 are not spilled or damaged, or the shape of the magnetic body 2 is not changed. The upper and lower surfaces of the ferrite sheet 1 may be bonded with the protective member 3, and at least one surface is protected. Moreover, it is preferable that the protection member 3 is insulating. Further, for example, an adhesive, an adhesive sheet, or the like for adhering an FPC having an antenna pattern and the sheet-like magnetic body 2 may be used.

  A plurality of holes 4 are formed in at least one of the upper and lower surfaces of the ferrite sheet 1. The hole 4 may be a through hole, but is preferably a recess having a bottom. The hole 4 will be described in detail later.

  FIG. 3 is an enlarged view of a main part of the ferrite sheet before being divided into small pieces in the present embodiment. FIG. 4 is an enlarged view of a main part of the ferrite sheet after being divided into small pieces in the present embodiment. FIG. 5 is an enlarged cross-sectional view of the hole 4 in the present embodiment. 3 and 4, (a) is a schematic diagram, and (b) is a photograph thereof.

In these drawings, the plurality of holes 4 have the following configuration.
-The shortest distance between each hole part 4 is 1 mm, and should just be about 0.5-3 mm. However, it changes also with the thickness of the sheet-like magnetic body 2, and is not restricted to this. In the present embodiment, four hole portions 4 are adjacent to one hole portion 4 at the shortest distance, and the ferrite sheet 1 having flexibility from any direction is formed by being three or more. be able to. That is, by being closest to the plurality of hole portions 4 (especially three or more), the flexibility in one direction is stronger than the flexibility in the other direction, thereby preventing the directionality of the flexibility. it can.
The plurality of holes 4 are arranged in a rhombus lattice. The shape of the array is not limited as long as it has a constant interval between the plurality of holes 4. However, it is preferable that it is uniform over the entire surface of the ferrite sheet 1 (sheet surface of the magnetic body 2). Moreover, it is preferable that it is the arrangement | sequence provided with fixed regularity like a triangular pattern, a polygonal pattern, a geometric pattern, or a grid | lattice form. Thereby, the dividing line 5 can be formed uniformly.
The hole 4 has a tapered shape in which the area of the opening is larger than the area of the bottom as shown in FIG. The opening 41 has a substantially rectangular shape of 0.35 × 0.2 mm, and the bottom surface 42 of the hole 4 has a substantially rectangular shape of 0.21 × 0.1 mm. (In FIG. 5, m1: m2 = 0.2: 0.1) Further, the area of the opening of the hole 4 is preferably 3 to 4 times the area of the bottom of the hole 4, and 2-5 It may be about double. Thereby, a flatter ferrite sheet 1 can be formed. That is, if the area of the opening and the area of the bottom surface are the same, the periphery of the hole 4 is likely to rise when the hole 4 is formed, and it is difficult to form it flat.
The depth d2 of the hole 4 is about 10% (about 10 μm) of the thickness d1 (about 100 μm) of the ferrite sheet 1. 5-30% is preferable. If the depth of the hole 4 is too shallow, it is difficult to divide using the hole 4. If the depth of the hole 4 is too deep, the periphery of the hole 4 rises when the hole 4 is formed, and it becomes difficult to form the ferrite sheet 1 flat. However, if the magnetic body 2 at the opening of the hole 4 can be removed, there is no problem even if the hole exceeds 30%.
-The shape of the bottom surface of the hole 4 is preferably a rectangle, a rhombus, or a polygon. The shape of the hole 4 is the same as the shape of the protrusion of the roller (see FIG. 7A) that forms the hole 4, for example. A method for manufacturing the ferrite sheet 1 will be described later. When the shape of the bottom surface of the hole part 4 has a corner, it becomes easy to divide using the corner.
-The area occupation rate of the opening part of the hole part 4 with respect to the area of the upper and lower surfaces of the ferrite sheet 1 is 27%, and should just be about 20 to 40%. Moreover, the area occupation rate of the bottom face of the hole part 4 with respect to the area of the upper and lower surfaces of the ferrite sheet 1 is 8%, and should just be about 5 to 15%.
-The shape of the opening part of the hole part 4 and the shape of a bottom face part are substantially the same (substantially rectangular), and an area is different (similarity). It is preferable that the center of the opening and the bottom overlap. Thereby, since the dividing line 5 easily passes through the hole portion 4, the dividing line 5 is also formed uniformly or regularly by arranging the hole portions 4 uniformly or regularly.

  The ferrite sheet 1 is divided into small pieces using such holes 4. The dividing line 5 (slit) is not necessarily straight, but may be bent or curved. Further, the dividing lines 5 are not necessarily parallel or orthogonal to each other, and may intersect at random. As shown in FIGS. 1 and 2, when the ferrite sheet 1 has a rectangular shape, the straight line connecting the nearest holes 4 intersects the outer side (four sides) of the ferrite sheet 1.

  Next, the manufacturing method of the ferrite sheet 1 is demonstrated.

  FIG. 6 is a manufacturing process flow chart of the ferrite sheet in the present embodiment.

As raw materials, for example, iron oxide Fe ₂ O ₃ , nickel oxide NiO, zinc oxide ZnO, and copper oxide CuO are mixed for a predetermined time. The slurry of the mixture is dried at a temperature of 110 to 130 ° C., then pulverized, calcined at a temperature of 800 to 910 ° C. and pulverized to prepare a main component powder.

The obtained ferrite magnetic material of the present invention has an average particle diameter of 0.5 to 1.6 μm according to the particle size distribution measurement by the laser diffraction scattering method. Moreover, according to the specific surface area measurement of BET by a nitrogen gas adsorption method, it has a value of 3 to 7 m ² / g.

  A polyvinyl butyral resin, a phthalate ester plasticizer, and an organic solvent are blended with 100 parts by weight of the manufactured ferrite magnetic material, and then mixed with a dedicated mill to prepare a slurry. The viscosity of the prepared slurry is 1500 to 2500 Pa · sec at 20 ° C., and has an appropriate viscosity for sheet molding.

  Next, a slurry made of a ferrite magnetic material is formed on a PET film to produce a green sheet having a thickness of 50 to 350 μm.

  Next, a plurality of holes 4 are formed in this green sheet.

  FIG. 7 is a diagram showing a method for forming a plurality of holes 4 in the present embodiment.

  As shown in FIG. 7A, the roller 10 in which the plurality of convex portions 11 are regularly arranged is rotated while being pressed on the green sheet 12 as shown in FIG. 7B. As a result, the plurality of convex portions 11 enter the green sheet 12, and the plurality of hole portions 4 are formed on the green sheet 12.

  Next, in the cutting step, the green sheet 12 is cut into a predetermined shape. In other words, the green sheet 12 is used for a non-contact charging module, or has a predetermined shape and thickness by punching and cutting using a dedicated mold designed to fit the shape of the RFID or NFC communication spiral antenna. A molded body is produced.

  Next, the compact having a predetermined shape is filled with a sheath, and then degreased and fired to prepare a fired ferrite body. The ferrite fired body has a thickness of 30 to 300 μm. The degreasing conditions are 200 to 600 ° C. Next, it is fired at a maximum temperature of 1000 ° C. (preferably 800 to 1200 ° C.) in a main firing furnace to produce a ferrite fired body.

  Next, a protective member (protective tape) is attached to the upper and lower surfaces of the sheet-like ferrite fired body. Thereafter, pressing is performed from at least one surface of the protective member, and the ferrite sheet 1 is divided using the hole 4. The pressing may be performed from either of the upper and lower surfaces of the ferrite sheet 1. When a straight groove is formed and divided, it must be pressed from a surface side different from the surface on which the groove is formed so as to be folded inward at the groove portion. However, in the present embodiment where the plurality of hole portions 4 are used for division, the ferrite sheet 1 is similarly formed from the surface side where the hole portions 4 are formed or from the other surface side. Can be divided. Moreover, the hole part 4 may be formed in both the upper and lower surfaces of the ferrite sheet 1, or may be only one side.

  In addition, the division using the hole 4 does not necessarily mean that the dividing line 5 passes through the hole 4 as shown in FIG. However, since the magnetic body 2 is thinner than the other portions in the hole 4 by utilizing the fact that the hole 4 is regular to some extent, the magnetic body 2 is surrounded by the hole 4 and the hole 4. Fragile. As a result, a dividing line enters mainly so as to connect between the closest hole portions 4. Accordingly, since the magnetic body 2 is divided between the plurality of hole portions 4 that are arranged with a certain regularity, it is divided with a substantially constant regularity. As a result, there is no great variation in the size of the small pieces depending on the location of the magnetic body 2. Note that the dividing line 5 may also enter a place other than between the closest holes 4. Thus, since the magnetic body 2 can be regularly divided | segmented only by forming and pressing the hole part 4, the ferrite sheet 1 provided with a softness | flexibility can be obtained very easily. That is, in order to form and divide the grooves as in the conventional example, the linear grooves must be formed at constant intervals and at constant depths. However, if the hole 4 has a variation in depth, it is easy to divide and may be formed deeper than the groove. Furthermore, unlike the groove, the hole 4 can be formed like a stamp, so that the formation is very easy. Further, the groove itself has flexibility direction, but the hole portion 4 itself has flexibility according to the direction in which the ferrite sheet 1 is bent because the hole portion 4 itself does not have flexibility direction. be able to.

  Further, in the case of the hole 4, if the depth of the hole 4 is 5% or more of the thickness of the magnetic body 2, the magnetic body 2 is formed in a flat sheet shape even if the hole 4 is deeply formed. Can do. That is, since the holes 4 are spaced apart from each other, the green sheet 12 is not separated when the holes 4 are formed even if the holes 4 are through holes. Therefore, the depth of the hole 4 may be 30% or more as long as the portion of the magnetic body 2 where the hole 4 is formed can be sufficiently removed.

  Further, since the ferrite sheet 1 uses the plurality of hole portions 4 and the dividing lines 5 enter between the hole portions 4, the dividing lines 5 can be inserted in all directions. As a result, flexibility can be provided not only in the vertical and horizontal directions but also in all directions such as oblique directions.

  Next, the configuration and shape of the antenna device including the ferrite sheet 1 will be described.

FIG. 8 is a configuration diagram of the antenna device according to the present embodiment.

  As for the antenna 6, a loop antenna is formed in a spiral shape. The spiral structure may be a spiral shape having an opening at the center, and the shape may be circular, substantially rectangular, or polygonal. By adopting a spiral structure, a sufficient magnetic field can be obtained to enable communication between the wireless communication medium and the wireless communication medium processing device due to generation of inductive power and mutual inductance. The substrate provided with the antenna 6 can be formed of polyimide, PET, glass epoxy substrate, or the like.

  Furthermore, the material of the antenna can be appropriately selected from conductive metal wire materials such as gold, silver, copper, aluminum, nickel, metal plate materials, metal foil materials, metal cylinder materials, etc. It can be formed by wire, metal foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing.

  In addition, the sheet-like magnetic body 2 whose upper and lower surfaces are both coated with the protective member 3 has very excellent flexibility, and can be easily punched and formed by punching or the like. It also has a feature that a simple shape can be formed at a low cost and can be molded in large quantities.

  The protective member 3 may be a resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat resistant resin, a synthetic rubber, a double-sided tape, an adhesive layer, or a film. The selection may be made in consideration of not only flexibility with respect to bending and bending of each component constituting the apparatus but also weather resistance such as heat resistance and moisture resistance.

  The terminal connection portion 7 is formed outside the antenna 6 and is connected to both ends of the antenna 6. The terminal connection portion 7 may be formed on a substrate provided with the antenna 6, and the terminal connection portion 7 is connected to a connector on a circuit board of a mobile terminal such as a mobile phone. The chip capacitor 8 is mounted on the substrate in the vicinity of the terminal connection portion 7 that is the end of the antenna 6 that is a loop antenna, and the resonance point of the resonance frequency of the antenna device is changed by changing the capacitance value of the chip capacitor 8. Can be changed. In addition, when this antenna device is mounted on a small terminal such as a mobile phone, a necessary part of the mobile terminal can be obtained by applying a double-sided tape, an adhesive, an adhesive layer, or a resin to the substrate on which the antenna 6 is formed. Paste to.

  Moreover, the ferrite sheet 1 in this Embodiment may be used for the module of the non-contact (contactless) charging system of portable terminals, such as a mobile telephone, a digital camera, a notebook PC, and an electronic device, for example. Since the non-contact charging module is charged using an electromagnetic induction phenomenon, the non-contact charging module includes a coil and a ferrite sheet 1 that improves the power transmission efficiency of the coil. The ferrite sheet 1 used for the non-contact charging module is relatively thick and is generally 300 μm to 1 mm. Flexibility in all directions is also demanded for the ferrite sheet 1 provided in the non-contact power receiving module. By providing the ferrite sheet 1 of the present embodiment, flexibility in all directions can be obtained. Further, it can be easily reduced in thickness.

  According to the present invention, since it is possible to manufacture a ferrite sheet that can easily and easily have flexibility in all directions, a mobile terminal equipped with a non-contact charging module, particularly a mobile phone, a portable audio, and a personal computer. It is useful for various electronic devices such as digital cameras and video cameras.

DESCRIPTION OF SYMBOLS 1 Ferrite sheet 2 Magnetic body 3 Protection member 4 Hole part 5 Dividing line 6 Antenna 7 Terminal connection part 8 Chip capacitor 10 Roller 11 Convex part 12 Green sheet

Claims (4)

A manufacturing method for manufacturing a ferrite sheet, the step of forming a plurality of holes in at least one surface of the ferrite sheet, the step of firing the ferrite sheet, and a protective sheet attached to at least one surface of the ferrite sheet A method of manufacturing a ferrite sheet, comprising: a step; and a step of dividing the ferrite sheet using the plurality of holes. 2. The method for manufacturing a ferrite sheet according to claim 1, wherein the ferrite sheet is divided at least between a plurality of hole portions and at least a hole portion closest to each other. The method for manufacturing a ferrite sheet according to claim 1, wherein the plurality of holes are arranged in a lattice shape. The method for manufacturing a ferrite sheet according to any one of claims 1 to 3, wherein each of the plurality of holes has a tapered shape in which an area of an upper surface portion is larger than an area of a bottom surface portion.