JP2009111197A - Molded ferrite sheet, sintered ferrite substrate, and antenna module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: when piling up and sintering several or several tens of molded ferrite sheets for obtaining sintered ferrite substrates consisting of Mg-Zn-Cu-based spinel ferrite, zirconia or alumina powder is applied to the surfaces of the molded ferrite sheets and the powder is removed after sintering in order to prevent sticking of the sintered ferrite substrates, it is however especially difficult to remove the powder on the surface of the thin-layer sintered ferrite substrate, and the powder remaining unremoved becomes the cause of foreign matter mix-in in precision electronic components or the like. <P>SOLUTION: The molded ferrite sheet having a thickness of 30 μm to 430 μm and characterized in that center line average surface roughness (Ra) is 10 nm to 800 nm and the maximum height (Rmax) is 3 μm to 10 μm in the surface roughness of at least one surface, and that the area occupancy rate of a cross-sectional area cut in a horizontal direction at the depth of 50% of the maximum height is 10 to 80%, is sintered, the molded ferrite sheet without requiring a release process is laminated and sintered, and thus, the clean thin-layer sintered ferrite substrate is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ferrite molded sheet used in the manufacture of a thin single layer soft magnetic sintered ferrite substrate, a thin single layer soft magnetic sintered ferrite substrate, and a non-contact IC using RFID (Radio Frequency Identification) technology. The present invention relates to an antenna module used for a tag or the like.

  When obtaining a sintered ferrite substrate, a molded sheet of ferrite powder or a molded sheet obtained by mixing ferrite powder with resin is fired. At that time, the sintered ferrite substrate adheres to the molded sheets and the firing base. If the fixed sintered ferrite substrate is peeled off, the sintered ferrite substrate will be damaged. To prevent sticking, release powder such as zirconia powder or alumina powder is applied to the surface of the ferrite molded sheet or firing base before firing. A method of removing the release powder after firing is common. Such an operation is extremely complicated, and it is difficult to completely remove the release powder. When used for electronic precision parts, it may cause contamination of foreign objects in the equipment.

  For example, Patent Document 1 is “related to a ferrite sheet for preventing ferrite core deformation used when firing a ferrite molded body”, and the prior art states that “this ferrite shrinks during firing, but deformation during this shrinkage”. In order to prevent this, alumina powder was used as a spread powder on the setter ". The method using the ferrite sheet for preventing deformation of the ferrite core has poor productivity, and it is necessary to prepare the ferrite sheet itself separately, which cannot be used in terms of cost. In the method of using the floor powder, when the floor powder is aggregated or the like, the sintered ferrite substrate is corrugated or cracked more frequently when the ferrite molded sheet is thin due to catching during firing.

  In Patent Document 2, a 2 mm square square ferrite piece is laid on a sheet base material and bonded and fixed, and another sheet base material and an antenna pattern are stacked on the upper portion to integrate an antenna integrated magnetic sheet. Have gained. However, it is difficult to arrange the ferrite solid pieces uniformly and efficiently on the sheet base material, which is not practical.

  Conventionally, when an antenna module used for a non-contact IC tag or the like using RFID technology is applied in the vicinity of metal, magnetic flux is converted into metal as an eddy current and communication cannot be performed. As a countermeasure, a method in which a conductive loop coil is formed in a spiral shape in a plane and a soft magnetic sheet is laminated in parallel with the coil has been widely adopted. The demand for density packaging is increasing. There is a strong demand for an antenna module that is capable of performing stable communication even when mounted in the vicinity of a metal and having a thinner antenna module stack.

  Patent Document 3 discloses an invention in which a loop coil and a magnetic sheet laminate are formed as an antenna module. With the above configuration, a capacitor is inserted in parallel before equipment mounting and adjusted to a desired frequency such as 13.56 MHz. However, when mounted on an electronic device and installed near a metal, the resonance frequency of the antenna may change, and there are many practical problems. Patent Document 4 discloses an antenna module having a configuration in which a metal shield plate is mounted in advance. In the antenna module, the thickness of the magnetic member laminated with the ferrite sheet is set to about 0.5 mm, the surface is covered with PET or PPS, and a metal shield plate is attached to the non-communication surface. Such a structure is difficult to reduce in thickness and cannot cope with recent downsizing of electronic devices.

JP-A-2-305416 JP 2006-174223 A Japanese Patent No. 3728320 JP 2005-340759 A

  The present invention does not use a release powder such as zirconia powder or alumina powder in order to obtain a clean thin layer sintered ferrite substrate, and the sintered ferrite substrate does not adhere to the sintered ferrite substrates or to the firing base. It is an object to obtain a ferrite molded sheet. Another object of the present invention is to obtain a clean sintered ferrite substrate that does not contaminate electronic devices with the remaining release powder.

  As an antenna used in the vicinity of a metal member, a magnetic sheet or the like that has been previously mounted and frequency-adjusted is used. However, if it is installed near a metal member, the resonance frequency of the antenna changes. Therefore, it is necessary to adjust the frequency after mounting the electronic device. Therefore, the present invention eliminates such a troublesome work, and it is an object of the present invention to obtain a thin antenna module in which the frequency adjusted by mounting a magnetic member in advance is almost unchanged even when the frequency is mounted in the vicinity of a metal member of any electronic device. And

  Another object of the present invention is to eliminate instability of antenna characteristics due to a gap that is easily formed between a magnetic member and a metal shield plate in an antenna used in the vicinity of a metal member.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention is a ferrite molded sheet made of Mg-Zn-Cu-based spinel ferrite having a thickness of 30 μm to 430 μm, and the center line average roughness of the surface roughness of at least one surface of the ferrite molded sheet is 170 to 800 nm, the maximum height is 3 μm to 10 μm, and the area occupation ratio of the fractured surface cut in the horizontal direction at 50% depth of the maximum height in an area of 100 μm square is 10 to 80% There is a ferrite molded sheet characterized in that (Invention 1).

  Further, the present invention is the ferrite molded sheet according to the first invention, wherein the surface of the ferrite molded sheet is roughened by sandblasting (the second invention).

  Further, the present invention is the ferrite molded sheet according to the first aspect of the present invention, wherein the ferrite molded sheet surface is press-molded with a die or calender roll having a surface processed into irregularities (the present invention 3).

  The present invention is also characterized in that when a ferrite-dispersed coating is applied and dried to obtain a molded sheet, it is obtained by coating a plastic film that has been sandblasted and transferring surface irregularities. This is a ferrite molded sheet (Invention 4).

  Further, the present invention provides the ferrite according to the present invention 1, wherein the ferrite powder is applied and dried to obtain a molded sheet, and the ferrite powder having an average particle size of 0.1 to 10 μm is adjusted to adjust the particle size to provide irregularities on the surface. This is a molded sheet (Invention 5).

  The present invention also relates to a sintered ferrite substrate made of Mg—Zn—Cu-based spinel ferrite having a thickness of 25 μm to 360 μm, and the center line average roughness of the surface roughness of at least one surface of the sintered ferrite substrate. The area occupancy of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is 5 to 70, and the maximum height is 2 to 9 μm. % Of the sintered ferrite substrate (Invention 6).

Further, the present invention is a sintered ferrite substrate having a thickness of 25 μm to 360 μm, and the center line average roughness of the surface roughness of at least one surface of the sintered ferrite substrate is 150 nm to 700 nm, The area occupancy of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 2 μm to 9 μm in a 100 μm square area is 5 to 70%, and the sintered density is 4. It is a sintered ferrite substrate characterized by being 4 to 5.0 g / cm ³ (Invention 7).

  Further, the present invention is the sintered ferrite substrate according to the present invention 6 or 7, wherein the real part μr ′ of permeability at 13.56 MHz is 80 or more and the imaginary part μr ″ of permeability is 100 or less. There is (Invention 8).

  In addition, the present invention is the sintered ferrite substrate according to any one of the present inventions 6 to 8, wherein a conductive layer is provided on one side of the sintered ferrite substrate (Invention 9).

  The present invention is the sintered ferrite substrate according to any one of the present inventions 6 to 9, wherein a groove is provided on at least one surface of the sintered ferrite substrate (Invention 10).

  Further, the present invention provides the sintered ferrite according to any one of the present inventions 6 to 10, wherein an adhesive film is attached to at least one surface of the sintered ferrite substrate, and a crack is provided in the sintered ferrite substrate. This is a substrate (Invention 11).

  According to the present invention, in the conductive loop antenna module used in the wireless communication medium and the wireless communication medium processing device, the conductive loop antenna is provided on one side of the magnetic member, and the surface opposite to the surface of the magnetic member provided with the antenna is provided. A loop antenna module provided with a conductive layer, wherein the magnetic member is a sintered ferrite substrate according to any one of the present inventions 8 to 11 (present invention 12).

  Further, the present invention is the antenna module according to the present invention 12, wherein the conductive layer has a thickness of 50 μm or less and a surface electrical resistance of 3Ω / □ or less (the present invention 13). ).

  The present invention is the antenna module according to the twelfth or thirteenth aspect of the present invention, wherein the conductive layer is provided by applying an acrylic or epoxy conductive paint (the present invention 14).

  In addition, the present invention is the antenna module according to the present invention 12 or 13, wherein the conductive layer is provided by printing and laminating with a silver paste on a ferrite molded sheet and integrally firing (Invention 15).

  According to the present invention, it is possible to obtain a clean thin sintered ferrite substrate that does not adhere to a zirconia powder or an alumina powder without being subjected to a mold release treatment. It is possible to provide a sintered ferrite substrate that does not have any.

  According to the present invention, the sintered ferrite substrate having a thickness of 25 to 360 μm has a real part μr ′ of permeability at 13.56 MHz of 80 or more and an imaginary part μr ″ of permeability of 100 or less. Thus, a magnetic member suitable for the antenna module can be obtained, which greatly contributes to the thinning of the antenna module.

  According to the present invention, in the antenna module used in the vicinity of the metal member, the thin conductive layer is formed on the sintered ferrite substrate, which is a magnetic member, by painting or printing lamination. Therefore, the thickness of the antenna module can be reduced to about 100 to 580 μm. In addition, according to the present invention, since the resonance is adjusted in a state where the conductive loop coil, the magnetic member (soft magnetic layer), and the conductive layer are integrally laminated, there is very little change in the antenna characteristics after the device is mounted. No complicated adjustment is necessary later.

  According to the present invention, in the antenna module used in the vicinity of the metal member, since there is no air gap between the magnetic member and the conductive layer, the antenna characteristics are extremely stable.

  According to the present invention, the magnetic member can be made flexible by attaching an adhesive film on at least one side to a sintered ferrite substrate used as a magnetic member, and by making a crack that causes the substrate to bend. It is easy to minimize the change in the characteristics of the antenna module due to the cracking of the magnetic member.

  First, the ferrite molded sheet according to the present invention will be described.

  As for the surface roughness of the ferrite molded sheet according to the present invention, the center line average roughness (Ra) is 170 to 800 nm, and the maximum height (Rmax) is 3.0 to 10 μm. Preferably, the center line average roughness (Ra) is 180 to 700 nm and the maximum height (Rmax) is 4 to 8 μm.

  In the surface roughness of the ferrite molded sheet according to the present invention, when the center line average roughness (Ra) is less than 170 nm or the maximum height (Rmax) is less than 3.0 μm, the sheet adheres during firing. On the other hand, when the center line average roughness (Ra) exceeds 800 nm or the maximum height (Rmax) exceeds 10 μm, the contact area of the molded sheet becomes large and it becomes difficult to release the sheet. In addition, the sintered ferrite substrate obtained by firing loses its smoothness and becomes easy to crack, and voids are likely to enter the boundary with the insulating film and conductive layer, reducing the cross-sectional area of the sintered body and decreasing the magnetic permeability. As a result, the antenna characteristics deteriorate.

  In the present invention, it cannot be shown only by the values of the centerline average roughness (Ra) and the maximum height (Rmax), and it is necessary to control the frequency of surface irregularities. In the bearing analysis of the 100 μm square image for which the surface roughness was obtained, the area occupation ratio of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height is 10 to 80%, preferably 15 to 75%. . If it is this range, the sintered ferrite board | substrate of this invention can be baked, without adhering between ferrite molded sheets, without using the release powder made into the objective of this invention.

  In the case of a thin plate having a thickness of 200 μm or less in the sintered ferrite substrate after firing, this is a particularly serious problem. In addition, when the area occupancy of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is less than 10% or more than 80%, the sheets are fixed during sintering and overlapped. It becomes difficult to separate the ferrite substrate.

The ferrite powder used in the ferrite molded sheet according to the present invention is spinel ferrite powder, Fe ₂ O ₃ is 40 to 50 mol%, MgO is 15 to 35 mol%, ZnO is 5 to 25 mol%, and CuO is 0 to 20 mol%. The composition is mol%. After the oxide powder raw material is uniformly mixed, it can be obtained by firing at 750 ° C. to 950 ° C. for 2 hours and pulverizing the fired product. Ferrite powder having a cumulative 50% volume particle diameter of 0.5 to 1.0 μm is preferred.

  Next, a method for producing a ferrite molded sheet according to the present invention will be described.

  Although the method for obtaining the ferrite molded sheet according to the present invention is not particularly limited, sandblasting widely used in metal polishing or the like is used for the method of roughening the surface of the ferrite molded sheet of the present invention. Can do. That is, a ferrite molded sheet having a roughened surface is obtained by spraying a solution obtained by dispersing glass, alumina, or the like as an abrasive in an aqueous solution onto a ferrite molded sheet and washing it with water.

Further, as another method for obtaining the ferrite molded sheet according to the present invention, a calender roll or a surface-processed mold in which ferrite powder is melt-mixed with a thermoplastic resin and / or a thermoplastic elastomer to perform surface processing (uneven polishing). There is a method of roughening by forming into a sheet by press molding.
As the thermoplastic resin, polyethylene (PE), polypropylene (PP), polyvinyl butyral (PVB), or the like can be used. Further, styrene / ethylene / butylene-based or olefin-based resins can be used as the thermoplastic elastomer. If necessary, two or more kinds of thermoplastic resins and / or thermoplastic elastomers may be mixed and used. It is preferable to use low density polyethylene (LDPE), polyvinyl butyral (PVB), etc. from the viewpoint of thermal decomposability during firing.
The composition is preferably 70 to 120 parts by weight of thermoplastic resin with respect to 1000 parts by weight of ferrite powder subjected to a coupling treatment of 10 to 50 parts by weight to 1000 parts by weight of ferrite powder. A more preferable composition range is 70 to 110 parts by weight of the thermoplastic resin with respect to 1000 parts by weight of the coupling agent-treated ferrite.
The mixture of the ferrite and the thermoplastic resin is kneaded at 120 to 140 ° C. for 20 to 60 minutes with a pressure kneader or the like, and then molded using a press die whose surface is uneven.

  As another method for obtaining the ferrite molded sheet according to the present invention, there is a method of applying a ferrite-dispersed paint to a plastic film. The blend composition of the ferrite dispersion paint is 70 to 120 parts by weight of polyvinyl alcohol resin, 15 to 25 parts by weight of butyl butyl phthalate as a plasticizer, and 400 to 600 parts of solvent for 1000 parts by weight of Mg—Zn—Cu ferrite powder. Parts by weight. As the solvent, glycol ether, MEK, toluene, methanol, ethanol, n-butanol and the like can be used. Considering the dispersibility of the ferrite powder, workability of mixing, drying property, etc., the preferable composition range for the coating is 80 to 110 parts by weight of polybutyral resin and 18 to 22 butyl butylphthalate with respect to 1000 parts by weight of ferrite. The parts by weight and the solvent are 450 to 550 parts by weight.

  Although it does not specifically limit as a manufacturing method of a coating material, It is good to use a ball mill. When the solvent and ferrite are first filled and mixed, and then the resin and plasticizer are added and mixed, a uniform coating can be obtained. It is important that the obtained paint is sufficiently degassed with a vacuum container in order to prevent cracks in the coating film during coating and drying.

  The method for applying the ferrite dispersion paint is not particularly limited, but a roll coater or a doctor blade can be used. A doctor blade may be used from the viewpoint of film thickness accuracy and paint stability. It can apply | coat to a plastic film by a doctor blade to desired thickness, and it is made to dry for 30 to 60 minutes at 80-130 degreeC, and a ferrite molded sheet can be obtained.

  Although it does not specifically limit to the plastic film for application | coating of a ferrite dispersion paint, What carried out the sandblasting process of various films, such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), a polyimide, can be used. A polyethylene terephthalate (PET) film is preferred from the viewpoint of processability of the film surface and thermal stability when coating and drying. By using a sandblasted plastic film, the unevenness of the plastic film can be transferred to a ferrite molded sheet, and a molded sheet having a desired surface roughness can be obtained.

  Yet another method for obtaining the ferrite molded sheet of the present invention is a method of adjusting the surface roughness of the ferrite molded sheet according to the particle size of the ferrite powder. In the method of applying the ferrite-dispersed coating to a plastic film, as ferrite powder, ferrite having a cumulative 50% volume particle diameter of 3 to 10 μm is added to 100 parts by weight of a ferrite powder having a cumulative 50% volume particle diameter of 0.1 to 1.0 μm. By using a powder mixed with 5 to 40 parts by weight, the ferrite molded sheet having the surface roughness of the present invention can be obtained even if a normal plastic film without sandblasting is used. Considering the surface roughness of the sheet, 10 to 40 parts by weight of powder having a cumulative 50% volume particle diameter of 3 to 7 μm may be mixed with 100 parts by weight of powder having a cumulative 50% volume particle diameter of 0.3 to 0.7 μm. Is preferred.

  In the present invention, the ferrite molded sheet is fired to obtain a sintered ferrite substrate.

  The sintered ferrite substrate according to the present invention is fired by stacking about 5 to 20 ferrite molded sheets of the present invention on an alumina plate having a porosity of 30%. In the firing conditions, it is important to provide a process for removing resin components and growing ferrite particles using an electric furnace or the like. Resin removal is performed at 150 ° C. to 550 ° C. for 5 to 80 hours, and ferrite particles are grown at 850 ° C. to 1200 ° C. for 1 to 5 hours.

  In order to prevent heat deformation and cracking of the sheet, it is better to maintain the constant temperature after removing the resin component from room temperature at a temperature of about 10 to 20 ° C./hour. After that, it is preferable that the temperature is raised at 30 to 60 ° C./hour, then kept at a constant temperature and sufficiently sintered to grow ferrite particles and then gradually cooled. In addition, what is necessary is just to select optimal conditions for the holding temperature and time of each process according to the number of the ferrite forming sheets to process.

  Next, the sintered ferrite substrate according to the present invention will be described.

In the surface roughness of the sintered ferrite substrate according to the present invention, the center line average roughness (Ra) is 150 to 700 nm, and the maximum height (Rmax) is 2.0 to 9.0 μm. Preferably, the center line average roughness (Ra) is 160 to 600 nm, and the maximum height (Rmax) is 3.0 to 8.0 μm.
Further, the area occupation ratio of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is 5 to 70%, preferably 10 to 60%. More preferably, it is 10 to 50%.
By firing the ferrite molded sheet, the center line average roughness (Ra) can be 150 nm or more and the maximum height (Rmax) can be 2.0 μm or more. When the surface roughness of the sintered ferrite substrate exceeds the center line average roughness (Ra) of 700 nm or the maximum height (Rmax) exceeds 9.0 μm, the smoothness is lost, and the insulating ferrite film In addition, voids and the like are likely to enter the interface with the conductive layer, resulting in poor antenna characteristics. Further, the sintered cross-sectional area is reduced and the magnetic permeability is reduced. For example, it becomes a big problem in the case of a thin plate having a thickness of 200 μm or less in the sintered ferrite substrate after firing.
Moreover, by firing the ferrite molded sheet, the area occupation ratio of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is in the range of 5 to 70%.

The sintered density of the sintered ferrite substrate according to the present invention is 4.6 to 5.0 g / cm ³ . When the sintered density of the sintered ferrite substrate is less than 4.4 g / cm ³ , the sintering is insufficient, so that the sintered ferrite substrate is easily broken and the real part μr ′ of the magnetic permeability is lowered. Moreover, it is not necessary to sinter until it exceeds 5.0 g / cm < ³ >. Preferably, it is 4.5 to 4.9 g / cm ³ .

  The sintered ferrite substrate according to the present invention can be used by providing an adhesive film on at least one surface and then cracking the substrate to impart flexibility to the laminate. At that time, when cracks occur, the magnetic permeability decreases, but the magnetic permeability changes depending on the state of cracks. For this reason, preferably, a regular groove is provided in the substrate and a crack is easily generated from the groove portion, thereby providing flexibility and stabilizing the magnetic characteristics after the crack has occurred.

As the groove provided in the sintered ferrite substrate according to the present invention, a V-shaped groove having a tip angle of 25 to 45 degrees can be provided on one side of the molded sheet by an embossing roll or a metal blade.
The gap between the grooves is 1 to 5 mm at the bottom of the groove. If it is less than 1 mm, the magnetic permeability decreases when the sintered ferrite substrate is broken along the groove, and the processing becomes difficult. If it exceeds 5 mm, the flexibility of the sintered ferrite substrate is lowered. A more preferable interval between the grooves is 2 to 4 mm.
The depth of the groove is 0.4 to 0.7 as a ratio to the thickness of the molded sheet (groove depth / sheet thickness). If the groove depth / sheet thickness ratio is less than 0.4, cracks may not occur along the grooves, resulting in uneven cracks and unstable magnetic permeability. If the groove depth / sheet thickness ratio exceeds 0.7, the firing process may crack along the grooves. A more preferable range of the groove depth is a groove depth / sheet thickness ratio of 0.4 to 0.6.
Further, the pattern of grooves drawn on the sheet surface may be any of a regular triangle, a lattice shape, or a polygonal shape. When the sintered ferrite substrate is divided along the groove, it is important that the broken pieces are as uniform as possible, and the permeability does not change as much as possible even if the substrate is bent.

  Since the sintered ferrite substrate according to the present invention is thin and easy to break, a crack is made after sticking an adhesive protective film on at least one side, the real part μr ′ of permeability at 13.56 MHz is 80 or more, and the imaginary part μr of permeability is μr ” Is maintained at 100 or less, it has been found that moderate flexibility is imparted to the sintered ferrite substrate and that it is particularly excellent as a thin-layer sintered ferrite substrate of 25 to 360 μm for the loop antenna module.

  When the real part μr ′ of the magnetic permeability of the sintered ferrite substrate according to the present invention is less than 80, the coil inductance of the antenna module is lowered and the communication distance is shortened. When the imaginary part μr ″ of the permeability exceeds 150, the loss increases, the antenna Q decreases, and the communication distance is shortened. Preferably, the real part μr ′ of the permeability is 85 or more and the imaginary part μr ″ is 90 or less. is there.

  Next, an antenna module according to the present invention will be described.

The antenna module according to the present invention is obtained by providing a conductive loop antenna on one side of a sintered ferrite substrate that is a magnetic member, and providing a conductive layer on the surface opposite to the surface of the magnetic member provided with the antenna. The conductive loop antenna is formed by forming a spiral conductive loop having a thickness of 20 to 30 μm on one surface of an insulating film such as a polyimide film or pet film having a thickness of 20 to 60 μm.
In the present invention, a conductive layer obtained by applying and drying a conductive paint is provided on one side of a ferrite sintered substrate having a thickness of 25 to 360 μm, or a silver paste is printed and laminated before firing the ferrite molded sheet and then integrally fired to form a conductive layer. The provided sintered ferrite substrate can be used. The thickness of the conductive layer is preferably 5 to 50 μm. When the surface opposite to the conductive layer surface of the conductive loop antenna and the sintered ferrite substrate is bonded with a double-sided adhesive tape having a thickness of 20 to 60 μm, and the same adhesive tape is also applied to the conductive layer surface, the total thickness is 110 as shown in FIG. An antenna module of ˜620 μm is obtained.

  The insulating film is not particularly limited, but may have a surface electric resistance of 5 MΩ / □ or more, and preferably 10 MΩ / □ or more in order to prevent a minute leakage current.

  As the conductive paint, a conductive paint obtained by dispersing copper and silver powder as a conductive filler in an organic solvent such as butyl acetate and toluene and an acrylic resin or an epoxy resin can be used.

  A conductive paint may be applied to one side of the sintered ferrite substrate and dried and solidified in an air atmosphere at room temperature to 100 ° C. for 30 minutes to 3 hours to provide a 20 to 50 μm conductive layer. The surface electrical resistance of the conductive layer is preferably 3Ω / □ or less. The surface electrical resistance is 1Ω / □ or less in order to reduce the characteristic change as an antenna by constructing near the metal. Moreover, in order to make lamination | stacking thickness thin, 20-30 micrometers is preferable.

  The sintered ferrite substrate with a conductive layer can also be obtained by an integral firing method by applying a conductive paste by the green sheet method. An insulating protective film may be laminated so that the conductive layer is not exposed inside the electronic device. A capacitor, which is a known method, is inserted in parallel with the loop so as to resonate the obtained antenna module at a desired frequency, and the resonance frequency is adjusted to 13.56 MHz.

  As described above, the conductive loop antenna, the adhesive layer, the ferrite sintered substrate, and the conductive layer are in close contact and integrated, and the capacitor is introduced in parallel to the loop circuit to adjust the resonance frequency to 13.56 MHz. Even if construction is performed in the vicinity of a metal member of an electronic device, a change in antenna characteristics is extremely small and stable communication can be ensured.

  The measuring method of each measured value shown in an Example is described.

[Surface Roughness] The surface roughness (centerline average roughness Ra, maximum height Rmax) of the ferrite molded sheet and the sintered ferrite substrate is 100 μm square using an atomic force microscope AFM (Digital Scope NanoScope III). It was obtained by measuring the area of.
In addition, in order to represent the uneven shape of the surface, it was quantified with the Bearing analysis software of the same apparatus. By determining the area occupancy ratio of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height (Rmax) from the image obtained by determining the surface roughness, the uneven shape states were compared. That is, when the area occupancy is 10 to 80% in the case of a ferrite molded sheet, sticking after firing can be prevented. When the sintered ferrite substrate after firing was measured, the area occupation ratio in the case of the sintered ferrite substrate that did not adhere was 5 to 70%. In addition, the measurement of the surface roughness of the sintered ferrite board | substrate with intense fixation of a comparative example was performed about the location which has not adhered from the cracked board | substrate.

[Cumulative 50% Volume Particle Diameter] The average particle diameter of the ferrite powder was measured by a wet method using a Microtrac MT3300 manufactured by Nikkiso Co., Ltd. An ultrasonic homogenizer (model: 300W) is added with 5 g of ferrite powder to 100 ml of an aqueous solution containing 0.2% of hetametaphosphoric acid as a dispersant and 0.05% of a nonionic surfactant (manufactured by Triton X-100 Dow Chemical) as a surfactant. , Manufactured by Nikkiso Co., Ltd.) for 300 seconds, measurement time 30 seconds, measurement range 0.021 to 1408 μm, solvent refractive index 1.33, particle refractive index 2.94, and particle shape is non-spherical. It was measured.

[Sheet Thickness] The thickness of the sheet was determined by measuring the four corners of the molded sheet cut to an outer dimension of 80 mm square using a Digimatic Indicator ID-S112 manufactured by Mitutoyo Corporation, and obtaining an average value.

[Sintering Density] The sintering density of the sintered ferrite substrate was calculated from the volume and weight obtained from the outer diameter of the sample.

[Permeability] The permeability is measured by cutting a sintered ferrite substrate into a ring shape having an outer diameter of φ14 mm and an inner diameter of φ8 mm, and measuring the thickness of the ring to obtain a test piece. A value of 13.56 MHz was measured using an impedance analyzer E4991A (manufactured by Agilent Technologies) and a jig (16454A) attached to the test station.

[Resonance Frequency and Resonance] As for the resonance characteristics of the antenna module, the resonance characteristics of the conductive loop antenna having the configuration described in FIG. 1 were measured. The method measures the frequency characteristics of the impedance of the feed line of the multilayer antenna module shown in FIG. 1, adjusts the capacitance by connecting a capacitor in parallel to the feed line, and the resonance frequency is 13.56 MHz. In this state, the resonance factor Q was measured using an impedance analyzer E4991A (manufactured by Agilent Technologies). In Examples 7 to 9 and Comparative Examples 5 to 7, the resonance frequency and the resonance factor Q when the antenna module and the iron plate were laminated were measured under the conditions set when the iron plate was not laminated for comparison.

[Surface Electric Resistance] The surface electric resistance of the conductive layer was measured by a four-probe method (based on JISK7149) using a low resistivity meter Loresta-GP (MCP-T600 type, manufactured by Mitsubishi Chemical Corporation).

[Example 1]
Mg-Zn-Cu ferrite powder which had been adjusted to 50% cumulative volume particle diameter 0.7 [mu] m _{(composition, Fe 2 O 3: 48.5Mol%} , MgO: 27.0Mol%, ZnO: 14.5Mol%, CuO: 10. 1000 parts by weight of ferrite powder surface-treated with 1000 parts by weight of 0 mol%, baking conditions: 850 ° C. 180 minutes) and 10 parts by weight of titanate coupling agent (KR-TTS manufactured by Ajinomoto Co., Inc.) and thermoplastic elastomer (Tosoh Corporation) LUMITAC 22-1) 50 parts by weight, 100 parts by weight of polyethylene having a density of 0.9 g / cm ³ and 20 parts by weight of stearic acid were kneaded in a pressure kneader at 130 ° C. for 40 minutes. The obtained ferrite resin composition kneaded product was heated at a temperature of 160 ° C. and a pressure of 100 kg / cm ² using an iron plate sandblasted to have a center line average roughness (Ra) of 450 nm and a maximum height (Rmax) of 8 μm. A press-molding time of 3 minutes was used to produce a ferrite molded sheet having a thickness of 74 μm and a size of 100 mm square.
Ten obtained ferrite molded sheets were stacked. As a firing base, an alumina setter (manufactured by Kikusui Chemical Co., Ltd.) was sandwiched between top and bottom, degreased at 500 ° C. for 10 hours, and fired at 940 ° C. for 2 hours. When the sintered product was peeled off after cooling, it was easily peeled off without damaging the plate.
The obtained sintered ferrite substrate had a thickness of 60 μm and an outer size of 80 mm square. A test piece having an outer diameter of φ14 mm and an inner diameter of φ8 mm was cut out from the sintered plate, and the frequency was 13.56 MHz using an impedance analyzer E4991A (manufactured by Agilent Technologies) and a jig (16454A) attached to the test station. As for the magnetic permeability, a sintered ferrite substrate having a magnetic property with no adhesion and an excellent magnetic property of μr ′ of 161 and μr ″ of 48 was obtained.

The surface roughness of the obtained ferrite molded sheet was cut in the horizontal direction at a center line average roughness (Ra) of 380 nm, a maximum height (Rmax) of 4.8 μm, and a 100 μm square area at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 38%.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 366 nm, the maximum height (Rmax) is 4.1 μm, and the area of 100 μm square is horizontal at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 31%.

[Example 2]
The same Mg-Zn-Cu ferrite 100 parts by weight as in Example 1, 2 parts by weight of butylphthalyl butyl glycolate, 12 parts by weight of polyvinyl alcohol resin (S-REC B BM-1 manufactured by Sekisui Chemical Co., Ltd.) and n-butanol as a solvent 4: 60 parts by weight of a solvent mixed with toluene 6 was mixed, dissolved, and dispersed by a ball mill to obtain a ferrite-dispersed paint. After degassing the ferrite-dispersed paint with an oil rotary vacuum pump, one side of the PET film was sandblasted to a centerline average roughness (Ra) of 530 nm and a maximum height (Rmax) of 5.6 μm (Panac Industrial Co., Ltd.) Applied to a certain thickness with a doctor blade and dried with hot air at 100 ° C. for 30 minutes to obtain a ferrite molded sheet having a thickness of 210 μm.
The obtained ferrite molded sheet was cut to a size of 100 mm square, peeled off from the PET film, and the obtained sheet was fired under the same conditions as in Example 1.
As a result of evaluating the characteristics of the obtained sintered ferrite substrate, the thickness was 174 μm, the outer dimension was 80 mm square, and the permeability at 13.56 MHz was μr ′ of 158 and μr ″ of 33, and there was no sticking and peeling It was easy.

The surface roughness of the ferrite molded sheet obtained was cut in the horizontal direction at a center line average roughness (Ra) of 450 nm, a maximum height (Rmax) of 5.1 μm, and a 100 μm square area at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 40%.
The center line average roughness (Ra) and the maximum height (Rmax) of the surface opposite to the surface in contact with the PET film are 50% of the maximum height in areas of 131 nm, 1.8 μm, and 100 μm square, respectively. The area occupancy of the fractured surface cut in the horizontal direction was 97%, and it was found that the surface roughness could be intentionally controlled by the PET film used.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 338 nm, the maximum height (Rmax) is 3.6 μm, and the area of 100 μm square is horizontal at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 21%.

[Example 3]
Mg-Zn-Cu ferrite powder having a cumulative 50% volume particle diameter of 6 μm (composition, Fe ₂ O ₃ : 48.5 mol%, MgO: 27.0 mol%, ZnO: 14.5 mol%, CuO: 10.0 mol%, firing) Condition: 1000 ° C. for 180 minutes), 300 parts by weight, and the same 50% cumulative volume as in Example 1 and 700 parts by weight of Mg—Zn—Cu ferrite having a volume particle diameter of 0.7 μm are mixed. A ferrite resin composition kneaded material was obtained. The obtained kneaded product was press-molded using an iron plate processed to have a center line average roughness (Ra) of 120 nm and a maximum roughness of 2 μm, at a temperature of 160 ° C., a pressure of 100 kg / cm ² , and a pressing time of 3 minutes. Thus, a ferrite molded sheet having a thickness of 188 μm and an outer dimension of 100 mm was produced.
Evaluation of the sintered ferrite substrate which processed the obtained sheet on the same conditions as Example 1 was performed. As a result, the magnetic permeability at a thickness of 157 μm and 13.56 MHz was 144 for μr ′ and 21 for μr ″, and there was no sticking and peeling was easy.

The surface roughness of the obtained ferrite molded sheet is a mixture of coarse ferrite particles. The center line average roughness (Ra) is 361 nm, the maximum height (Rmax) is 6.2 μm, and the maximum height is 100 μm square. The area occupancy of the fractured surface cut in the horizontal direction at a depth of 50% was 67%.
Further, the surface roughness of the sintered ferrite substrate is 305 nm at the centerline average roughness (Ra), 4.0 μm at the maximum height (Rmax), and 50 μm of the maximum height in the 100 μm square area in the horizontal direction. The area occupation ratio of the cut fracture surface was 49%.

[Example 4]
A sintered ferrite substrate was obtained in the same manner as in Example 2 except that the conditions were such that a ferrite molded sheet having a thickness of 43 μm was obtained at the time of application with a doctor blade.
As a result of evaluating the characteristics of the obtained sintered ferrite substrate, the permeability at 37 μm, 13.56 MHz was 156 for μr ′ and 31 for μr ″, and there was no sticking and peeling was easy.

The surface roughness of the ferrite molded sheet obtained was cut in the horizontal direction at a center line average roughness (Ra) of 345 nm, maximum height (Rmax) of 4.0 μm, and 100 μm square at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 23%.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 289 nm, the maximum height (Rmax) is 3.1 μm, and the area is 100 μm square and the horizontal height is 50% of the maximum height. The area occupation ratio of the cut fracture surface was 12%.

[Example 5]
A sintered ferrite substrate was obtained in the same manner as in Example 2 except that the conditions were such that a 377 μm-thick ferrite molded sheet was obtained at the time of application with a doctor blade.
As a result of evaluating the characteristics of the obtained sintered ferrite substrate, the magnetic permeability at 326 μm, 13.56 MHz was 167 for μr ′ and 50 for μr ″, and there was no sticking and peeling was easy.

The surface roughness of the ferrite molded sheet obtained was cut in the horizontal direction at a center line average roughness (Ra) of 634 nm, a maximum height (Rmax) of 7.8 μm, and a 100 μm square area at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 66%.
The surface roughness of the sintered ferrite substrate is 593 nm at the center line average roughness (Ra), 7.8 μm at the maximum height (Rmax), and 100% square in the horizontal direction at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 39%.

[Comparative Example 1]
A ferrite resin composition kneaded material was prepared in the same manner as in Example 1, except that the composition was sandwiched and formed using an iron plate processed to have a center line average roughness (Ra) of 120 nm and a maximum roughness of 2 μm. Sintered ferrite substrates were produced under similar conditions. As a result, the adhesion was so strong that it was difficult to peel off, and it was partially peeled off, but the plate was cracked, and no 80 mm square sintered ferrite substrate could be produced. The permeability of the sintered ferrite substrate at 13.56 MHz was 160 for μr ′ and 48 for μr ″.

The surface roughness of the obtained ferrite molded sheet is 98 nm in the center line average roughness (Ra), 0.9 μm in the maximum height (Rmax), and cut in the horizontal direction at a depth of 50% of the maximum height in the 100 μm square area. The area occupation ratio of the fractured surface was 5%.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 81 nm, the maximum height (Rmax) is 0.8 μm, and 100 μm square in the horizontal direction at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 1%.

[Comparative Example 2]
A ferrite dispersion paint was prepared in the same manner as in Example 2. The obtained paint is applied to a non-sandblasted PET film (centerline average roughness (Ra) 17 nm, maximum height (Rmax) 0.3 μm, thickness 50 μm) with a doctor blade to a certain thickness. And dried with hot air at 100 ° C. for 30 minutes to obtain a ferrite molded sheet having a thickness of 217 μm.
The sheet was peeled from the PET film and 10 sheets were stacked and subjected to the same firing treatment as in Example 1, and the obtained sintered ferrite substrate was evaluated. The thickness was 177 μm, and the adhesion was severe and could not be peeled.

The surface roughness of the ferrite molded sheet obtained was cut in the horizontal direction at a center line average roughness (Ra) of 78 nm, a maximum height (Rmax) of 1.8 μm, and a 100 μm square area at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 87%.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 54 nm, the maximum height (Rmax) is 1.3 μm, and the area of 100 μm square is horizontal at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 0.2%.

[Comparative Example 3]
A sheet was produced in the same manner as in Comparative Example 2, and then the zirconia powder having an average particle diameter of 5 μm (made by Daiichi Rare Element Chemical Industries, Ltd. After applying 50 mg by brushing, the same firing treatment as in Comparative Example 2 was performed, and the obtained sintered ferrite substrate was evaluated.
The magnetic permeability of the obtained sintered ferrite substrate at 13.56 MHz was μr ′ of 157 and μr ″ of 31. However, a site where the zirconia powder was fixed to the surface of the sintered ferrite substrate was observed, and this was brushed. During the removal, four of the 10 plates were broken, and the application and removal of the powder was very complicated, and the zirconia powder could not be completely removed.

[Comparative Example 4]
A sintered ferrite substrate was obtained in the same manner as in Example 1 except that an iron plate sandblasted to a center line average roughness (Ra) of 1200 nm and a maximum height (Rmax) of 14 μm was used. There was no sticking and it was possible to peel off without damaging the plate.
The permeability of the obtained sintered ferrite substrate at 13.56 MHz was unsatisfactory in terms of magnetic properties such that μr ′ was 78 and μr ″ was 1. This resulted in an excessively large surface roughness, resulting in sintering. The permeability decreased because the voids increased in the cross section of the ferrite substrate.

[Comparative Example 5]
A ferrite dispersion paint was prepared in the same manner as in Example 2. The obtained paint was applied to a PET film (U4-50 manufactured by Teijin DuPont Films Ltd.) having a center line average roughness (Ra) of 252 nm and a maximum height (Rmax) of 3.3 μm. And then dried at 100 ° C. for 30 minutes to obtain a ferrite molded sheet having a thickness of 198 μm.
The sheet was peeled from the PET film and 10 sheets were stacked and subjected to the same firing treatment as in Example 1, and the obtained sintered ferrite substrate was evaluated.
The obtained sintered ferrite substrate had a thickness of 169 μm, and was firmly fixed and could not be peeled off.
The surface roughness of the ferrite molded sheet obtained was cut in the horizontal direction at a center line average roughness (Ra) of 246 nm, a maximum height (Rmax) of 2.6 μm, and a 100 μm square area at a depth of 50% of the maximum height. The area occupation ratio of the fractured surface was 97%.
Further, the surface roughness of the sintered ferrite substrate is such that the center line average roughness (Ra) is 201 nm, the maximum height (Rmax) is 2.1 μm, and the area is 100 μm square in a horizontal direction at a depth of 50% of the maximum height. The area occupation ratio of the cut fracture surface was 96%.

  That is, it can be seen from this result that not only the surface roughness but also the control of the area occupancy ratio of the fracture surface is important for obtaining the effect of the present invention.

[Example 6]
A double-sided adhesive tape (product name: 467MP, manufactured by Sumitomo 3M) with a thickness of 50 μm is attached to the uneven surface of the sintered ferrite substrate obtained in Example 1, and a laminate comprising a sintered ferrite substrate layer of 60 μm and an adhesive layer of 50 μm. Was made.
In order to give this laminate a flexibility, it is placed on a urethane sheet having a thickness of 10 mm and an expansion ratio of about 10 times, and a roll line pressure is about 1 kg / cm using a rubber roller having an outer diameter of about 50 mm and a width of about 15 cm. The laminate was pressed vertically and horizontally to crack the entire sintered ferrite substrate.
Subsequently, the outer diameter was punched into 14 mmφ and the inner diameter was 8 mmφ, and the magnetic permeability was measured. As for the magnetic permeability, μr ′ was 121 and μr ″ was 10 at 13.56 MHz.

  Moreover, after winding the said laminated body around the iron rod of an external diameter of 30 mm (phi), the test piece similar to the above was cut out and the magnetic permeability was measured. As a result, μr ′ was 120, μr ″ was almost unchanged from 10, the flexibility was good, and the magnetic permeability μr ′ was 80 or more.

[Example 7]
A planar antenna was prepared by providing a 7-turn spiral conductive loop on a 25 μm PET film. The loop shape was a rectangle 45 mm long and 75 mm wide.
In addition, using the Mg—Zn—Cu ferrite used in Example 1, a ferrite molded sheet having a thickness of 185 μm was produced in the same manner as in Example 2, and a V-shaped cutting edge of 30 ° Thomson was formed on the surface of the molded sheet. V-grooves with a depth of about 90 μm were provided by a blade with a grid having a spacing of 2 mm. The obtained grooved ferrite molded sheet was cut into 100 mm square, peeled off from the PET film, and the obtained sheet was fired under the same conditions as in Example 1.
The obtained sintered ferrite substrate had a thickness of 143 μm and an outer size of 80 mm square. Apply a conductive paint (trade name Doutite XE-9000, manufactured by Fujikura Kasei Co., Ltd.) in which silver and copper powder are dispersed in a polyester resin to the non-grooved surface of the sintered ferrite substrate and dry at 50 ° C. for 30 minutes. A 30 μm conductive layer was provided. The surface electrical resistance of the conductive layer was 0.2Ω / □.
After affixing to this conductive surface on a double-sided adhesive tape (product name 467MP, manufactured by Sumitomo 3M Limited), the ferrite sintered substrate was split and given flexibility in the same manner as in Example 6. At that time, the ferrite pieces were 2 mm square and had a substantially uniform shape. This sheet had a magnetic permeability μr ′ of 119 and μr ″ of 9.0.

  Use a double-sided adhesive tape (product name: 467MP, manufactured by Sumitomo 3M Co., Ltd.) with a thickness of 50 μm so that there are no gaps between the conductive loop antenna and the surface of the sintered ferrite substrate where the conductive layer is not provided. An antenna module was produced. Since this module has a resonance frequency of 15.5 MHz and a Q of 67, it is adjusted by changing the capacitor capacity so that the resonance frequency is 13.5 to 13.6 MHz by connecting a capacitor in parallel to the loop antenna. did. After frequency adjustment, no change in Q was observed. Resonance characteristics were measured by bringing the conductive layer surface of the antenna module into close contact with a 1 mm thick iron plate. As a result, no change in resonance characteristics was observed regardless of whether or not an iron plate was attached.

[Example 8]
In the antenna module manufactured by the same method as in Example 7, the conductive layer of the sintered ferrite substrate was coated with nickel / acrylic conductive paint (trade name Doutite FN-101), dried at 50 ° C. for 30 minutes, and the coating film The same evaluation as in Example 7 was performed except that the surface electric resistance of 10 μm thickness was 2Ω / □. As a result, the resonance characteristics were a resonance frequency of 13.6 MHz and a Q of 63, and almost no change was recognized regardless of whether or not an iron plate was attached.

[Example 9]
Antenna module in the same manner as in Example 7 except that a sintered ferrite substrate provided with a 10 μm conductive layer obtained by integrally firing a conductive silver paste obtained by printing and laminating a conductive layer of a sintered ferrite substrate on a green sheet at 900 ° C. Was made. Evaluation similar to Example 7 was performed about the obtained antenna module. The surface electrical resistance of the conductive layer was 0.1Ω / □, the resonance characteristics were a resonance frequency of 13.55 MHz and Q was 63, and almost no change was observed regardless of whether or not an iron plate was attached.

[Comparative Example 6]
An antenna module was configured in the same manner as in Example 7 except that the conductive layer was not provided on the sintered ferrite substrate. The resonance frequency when the iron plate was not laminated was 13.5 MHz, and Q was 66. When a resonance characteristic was measured by laminating an iron plate having a thickness of 1 mm in the same manner as in Example 4, the resonance frequency became 15.8 MHz and shifted to the 2.3 MHz high frequency side. Although Q was 66 and the degree of resonance did not change, the frequency was shifted, and therefore the resonance was not resonated at 13.56 MHz.

[Comparative Example 7]
The configuration was the same as that of Comparative Example 6, and the same evaluation as in Comparative Example 6 was performed except that the thickness of the sintered ferrite substrate was 300 μm. When the iron plates were laminated, the resonance frequency was 13.9 MHz, and although the frequency change was smaller than that of Comparative Example 6, the communication strength was lowered.

[Comparative Example 8]
An antenna having the same configuration as in Example 7 except that the thickness of the conductive layer provided on the sintered ferrite substrate in the antenna module manufactured by the same method as in Example 7 is 5 μm and the surface electric resistance is 5Ω / □. The resonance characteristics of the module were evaluated. As a result, when the iron plates were laminated, the resonance frequency changed to 15.0 MHz and the communication strength at 13.56 MHz also decreased.

  The ferrite molded sheet according to the present invention can be easily provided with an appropriate surface roughness on at least one side, and has a ferrite molded sheet that does not adhere even when fired in a stacked state or when a release powder is not used or sintered. It is obtained industrially.

  The sintered ferrite substrate according to the present invention achieves high magnetic permeability even with a relatively thin thickness, and is manufactured by stacking and firing without using a release powder such as zirconia or alumina. In this case, there is no powder contamination and it is suitable as a magnetic core for antenna modules for high-density mounting in RFID (Radio Frequency Identification), which has been rapidly spreading in recent years.

  An antenna module in which a conductive layer of 20 to 50 μm is adhered and laminated on one side of a sintered ferrite substrate according to the present invention and integrated with a conductive loop antenna is applied to an electronic device in the vicinity of metal in RFID (Radio Frequency Identification) communication. However, there is almost no change in the characteristics, and the thickness of the module can be reduced, so that it can cope with high-density mounting of electronic devices.

It is the schematic of the structure cross section of an antenna module. 2 is an image of the surface shape of a ferrite molded sheet of Example 2. It is the data and the data of an area occupation rate by the Bearing analysis of the ferrite molded sheet of Example 2. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown. 3 is a surface shape image of a sintered ferrite substrate of Example 2. It is the data and the data of an area occupation rate by the Bearing analysis of the sintered ferrite board | substrate of Example 2. FIG. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown. 6 is a surface shape image of a ferrite molded sheet of Comparative Example 2. It is the data by the Bearing analysis of the ferrite molded sheet of the comparative example 2, and the data of an area occupation rate. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown. 3 is a surface shape image of a sintered ferrite substrate of Comparative Example 2. It is the data and the data of an area occupation rate by the Bearing analysis of the sintered ferrite board | substrate of the comparative example 2. FIG. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown. 10 is a surface shape image of a ferrite molded sheet of Comparative Example 5. It is the data by the Bearing analysis of the ferrite molded sheet of the comparative example 5, and the data of an area occupation rate. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown. 10 is a surface shape image of a sintered ferrite substrate of Comparative Example 5. It is the data by the Bearing analysis of the sintered ferrite board | substrate of the comparative example 5, and the data of an area occupation rate. In the figure, a fracture surface image cut in the horizontal direction at a depth of 50% of the maximum height, a histogram of individual heights, and a graph of the area occupancy are shown.

Explanation of symbols

1: Sintered ferrite substrate (25 to 360 μm)
2: Insulating film (20-60 μm)
3: Conductive layer (20-50 μm)
4: Double-sided adhesive tape (20-40 μm)
5: Conductive loop (20-30 μm)
6: Separator

Claims (15)

A ferrite molded sheet made of Mg—Zn—Cu spinel ferrite having a thickness of 30 μm to 430 μm, wherein the center line average roughness is 170 nm to 800 nm in the surface roughness of at least one surface of the ferrite molded sheet. The maximum height is 3 μm to 10 μm, and the area occupation ratio of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is 10 to 80%. Ferrite molded sheet. 2. The ferrite molded sheet according to claim 1, wherein the surface of the ferrite molded sheet is roughened by sandblasting. 2. The ferrite molded sheet according to claim 1, wherein the surface of the ferrite molded sheet is pressure-molded with a mold or calender roll having a surface processed into irregularities. 2. The ferrite molded sheet according to claim 1, which is obtained by coating a sandblasted plastic film when transferring a ferrite dispersion paint and drying to obtain a molded sheet, and transferring surface irregularities. 2. The ferrite molded sheet according to claim 1, wherein when a ferrite dispersed paint is applied and dried to obtain a molded sheet, the particle size of the ferrite powder having an average particle diameter of 0.1 to 10 μm is adjusted to provide irregularities on the surface. A sintered ferrite substrate made of Mg—Zn—Cu-based spinel ferrite having a thickness of 25 μm to 360 μm, wherein the center line average roughness is 150 nm to 700 nm in the surface roughness of at least one surface of the sintered ferrite substrate. The maximum height is 2 μm to 9 μm, and the area occupation rate of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is 5 to 70%. A sintered ferrite substrate. A sintered ferrite substrate having a thickness of 25 μm to 360 μm, wherein the center line average roughness of the surface roughness of at least one surface of the sintered ferrite substrate is 150 nm to 700 nm, and the maximum height is 2 μm to 9 μm. And the area occupancy of the fractured surface cut in the horizontal direction at a depth of 50% of the maximum height in an area of 100 μm square is 5 to 70%, and the sintered density is 4.4 to 5.0 g / A sintered ferrite substrate characterized by being cm ³ . 8. The sintered ferrite substrate according to claim 6, wherein a real part μr ′ of permeability at 13.56 MHz is 80 or more and an imaginary part μr ″ of permeability is 100 or less. The sintered ferrite substrate according to any one of claims 6 to 8, wherein a conductive layer is provided on one surface of the sintered ferrite substrate. The sintered ferrite substrate according to any one of claims 6 to 9, wherein a groove is provided on at least one surface of the sintered ferrite substrate. The sintered ferrite substrate according to any one of claims 6 to 10, wherein an adhesive film is attached to at least one surface of the sintered ferrite substrate, and a crack is provided in the sintered ferrite substrate. In a conductive loop antenna module used in a wireless communication medium and a wireless communication medium processing apparatus, a loop in which a conductive loop antenna is provided on one side of a magnetic member and a conductive layer is provided on a surface opposite to the surface of the magnetic member provided with the antenna It is an antenna module, Comprising: A magnetic member is the sintered ferrite board | substrate in any one of Claims 8 thru | or 11, The antenna module characterized by the above-mentioned. 13. The antenna module according to claim 12, wherein the conductive layer has a thickness of 50 μm or less and a surface electrical resistance of 3Ω / □ or less. The antenna module according to claim 12 or 13, wherein the conductive layer is provided by applying an acrylic or epoxy-based conductive paint. 14. The antenna module according to claim 12, wherein the conductive layer is provided by printing and laminating with a silver paste on a ferrite molded sheet and integrally firing the conductive layer.