JP2009094405A - Magnet paste and thick film magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thick film magnet which can be formed to have a fine pattern shape while exhibiting a desired magnetic characteristic. <P>SOLUTION: A magnet paste is obtained by mixing at least SmFeN-based magnet particles, an adhesive and a solvent. The magnet particles are set to have a composition proportion not smaller than 67 wt.% and not larger than 97 wt.%. The magnet paste is printed by screen printing into a predetermined pattern on a polyimide substrate and is then thermoset to form a thick film magnet. For example, as shown in Fig.2, the pattern is formed to have a line width of about 100 μm and a thickness of about 150 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnet paste and a thick film magnet.

  Rare earth permanent magnets are used in a wide range of fields such as motors, mobile phones and computer electronic components. The magnetic materials generally used for the rare earth permanent magnets are samarium (Sm) and neodymium (Nd), and the magnet products using them are samarium cobalt magnet (SmCo) and neodymium. There are iron and boron magnets (NdFeB).

  The manufacturing method for manufacturing these rare earth-based permanent magnets varies depending on the thickness of the magnet, and in the range of a thick film having a thickness of about 1 μm to several hundred μm, which is the object of the present invention, the PLD method (Pulsed Laser Deposition) method) and AD method (Aerosol Depsition method) are used. The PLD method is a kind of PVD (physical vapor deposition) method. Fragments (ions, clusters, molecules, atoms) emitted by intermittently irradiating a target in a vacuum chamber with a pulsed laser and ablating the target Is a technique for forming a film by arriving at and depositing on the substrate disposed opposite to the target. The AD method is a technique for forming a film on the substrate surface by mixing fine particles of submicron size with a gas, making it into an aerosol form, and spraying it toward the substrate through a nozzle.

In Patent Document 1, NdFeB and SmCo are mixed with polyurethane and a phenoxy resin which is a kind of epoxy resin to form a paste, and the paste-like material is formed on a substrate by screen printing or the like. A technique for producing a thick film magnet by using curing is disclosed.
Japanese Patent Laid-Open No. 2003-197409

  The PLD method and AD method are not practical because the apparatus configuration becomes large and it takes a long time to form a magnetic material on the substrate to a desired thickness. Further, in the technique disclosed in Patent Document 1, a thick-film rare earth permanent magnet can be easily produced as compared with the PLD method or the like, but NdFeB or SmCo as a material may have a large average particle size. It was difficult to print and form a thick film with a fine pattern shape. When a thick-film rare earth permanent magnet is prepared based on a paste obtained by mixing NdFeB or SmCo with a reduced average particle size with phenoxy resin or the like, practical magnetic properties are obtained. Can't get.

  This invention solves the subject mentioned above, The objective is to provide the magnet paste and thick film magnet which can comprise a fine pattern shape, exhibiting a desired magnetic characteristic.

  In order to achieve the above-described object, the magnet paste according to the present invention is (1) a magnet paste configured by mixing at least an SmFeN-based magnet powder, an adhesive, and a solvent, The composition ratio was 67 wt% or more and 97 wt% or less.

  (2) Another solution of the magnet paste according to the present invention is a magnet paste configured by mixing at least an SmFeN-based magnet powder, an adhesive and a solvent, and the composition ratio of the magnet powder is 67 wt% or more and 90 wt% or less.

  Since the SmFeN-based magnet powder has a small particle size, smoothness is good and a fine pattern can be formed even if a mask (screen) having a fine opening diameter is used when it is made into a paste. The procedure for mixing the magnet powder, adhesive, and solvent is arbitrary, and all materials may be mixed together, or any combination may be mixed first, followed by other materials. You may make it make it.

  When the composition ratio of the magnet powder is less than 67 wt%, practical magnetic characteristics as a magnet cannot be obtained. Here, practical magnetic characteristics include, for example, a residual magnetic flux density (Br) of 1.3 kG or more, a coercive force (Hc) of 1.8 kOe or more, and a maximum energy product (BH) max (the first on the BH curve). The maximum value of the product of B and H in the second quadrant is 0.3 MG · Oe or more. Of course, it is not limited to this value. On the other hand, if the composition ratio of the magnet powder exceeds 97.5 wt%, the strength after curing becomes weak and impractical. Therefore, the range shown in the above (1) was adopted.

  In consideration of printing a pattern with a line width of 1 mm or less, if the magnet powder exceeds 90 wt%, the viscosity necessary for passing through the printing screen or metal mask is insufficient. Therefore, the range shown in (2) above was adopted.

  (3) The magnet powder may have an average particle size of 5 μm or less and a maximum particle size of 10 μm or less. When the average particle diameter is larger than 5 μm or the maximum particle diameter is larger than 10 μm, it is difficult to make the film thickness after printing 10 μm or less, and the flatness of the film-formed surface after printing also deteriorates. Therefore, it is preferable to set the particle size within the above range. Of course, when the required film thickness is larger than 10 μm, it is not hindered to exceed the above-mentioned particle size range defined in terms of film thickness.

  (4) An epoxy resin can be used for the adhesive. A resin can be used as the adhesive. As the resin in this case, for example, polyesters, acrylics, vinyl chlorides, vinyl acetates, urethanes, epoxies, phenol polymers, and other mixtures can be used. Since the epoxy resin has a strong adhesive strength, it is preferable to use an epoxy resin from the viewpoint of the strength of the finally produced thick film magnet. Of course, in (1) to (3) other inventions, other resins may be used, and adhesives other than resins may be used.

  (5) A thick film magnet according to the present invention is formed on a substrate by a printing method using the magnet paste according to any one of (1) to (4) above, and a film thickness after curing is 10 μm or more. It was formed so as to be 500 μm or less. In order to make it harden | cure, it can carry out by mixing an appropriate hardening | curing agent. This curing agent may be mixed with the magnet paste according to any one of (1) to (4), or may be mixed with other materials when producing the magnet paste. As a curing agent when an epoxy resin is used as an adhesive, a general curing agent for epoxy resin may be used. Since it only needs to be finally cured, it is not always necessary to positively mix the curing agent, and a curing method other than the curing agent can be employed.

  (6) Various materials can be used for the substrate, for example, a flexible substrate. For example, polyimide or the like can be used as the flexible substrate. In this way, a magnet strong against bending is formed.

  (7) The line width of the pattern printed on the substrate may be in the range of 30 μm or more and 5 mm or less. Due to the limit of the opening diameter of the screen, it is difficult to form a line width of less than 30 μm by printing. Also, due to the recent demand for downsizing, a line width exceeding 5 mm is not practical. Therefore, the above range is preferable.

  (8) On the premise of the invention of any one of the above (5) to (7), the thick film magnet is provided with anisotropy by being cured in a magnetic field. When a film (magnet paste) printed on a substrate in a predetermined pattern is cured in a magnetic field, the film is cured while maintaining an oriented state in the direction of the magnetic field, thereby forming an anisotropic magnet.

  In the present invention, a fine thick film magnet can be formed in a short time by printing a paste using SmFeN-based magnet powder.

  Hereinafter, preferred embodiments of the present invention will be described. The magnet paste of this embodiment is a mixture of SmFeN-based magnet powder, an epoxy resin as an adhesive, and a curing agent for epoxy resin, and the magnet powder is dispersed in the resin composition. A solvent is added to the paste to form a paste. At this time, the composition ratio of the SmFeN-based magnet powder is 67 wt% or more and 97.5 wt% or less.

  By performing screen printing using this magnet paste, a thick-film rare earth permanent magnet having a desired pattern shape is formed on the substrate. Therefore, the above-mentioned solvent is added to adjust the viscosity of the magnet paste during printing, and the type and amount of the solvent are set according to the target viscosity.

  Screen printing is performed using a metal mask having an opening width of 5 mm or less and a plate thickness of 500 μm or less. Preferably, a printing mask having an opening width of 100 μm or less is used. By using a metal mask, a thick film pattern can be formed by one printing. Furthermore, since the SmFeN-based magnet powder has a small particle size (for example, a maximum particle size of 10 μm or less and an average particle size of 5 μm), a fine pattern shape can be formed on the substrate. In addition, when a desired film thickness cannot be obtained by one printing process, a printing process may be performed a plurality of times. Instead of a metal mask, a mesh used for normal screen printing can also be used. . However, when a mesh is used, since the film thickness formed in one printing process is thin, it is necessary to perform printing a plurality of times. When the printing process is performed multiple times, printing is performed so as to be superimposed on the film formed by one printing process. At that time, after the previously printed film is cured, the next film is printed. Alternatively, they may be cured together before being cured.

  In addition, when the printed film is set in a predetermined magnetic field while it is cured, it is oriented in the direction of the magnetic field and becomes an anisotropic magnet. Of course, it may be cured without being placed in a magnetic field.

  In the above embodiment, an epoxy resin is used as an adhesive, but other resins may be used. In the above embodiment, the SmFeN-based magnet powder has a maximum particle size of 10 μm or less and an average particle size of 5 μm. . Various patterns can be formed for the permanent magnet pattern formed by screen printing. By setting the opening width of the mask (metal mask / mesh) as appropriate, the line width can be as fine as 30 μm to 5 mm. In addition, the film thickness can be as thick as 10 to 500 μm.

  Various substrates can be used as the substrate to be printed. And when a polyimide substrate is used, since flexibility is favorable, it becomes a thick film permanent magnet strong also to a bending, and an application increases.

  A commercially available epoxy resin and a commercially available curing agent (for epoxy resin) were mixed at a weight ratio of 9: 1 to obtain a resin composition. The obtained resin composition and SmFeN powder were mixed at a weight ratio of 2: 8 by a disperser and then kneaded by a three-roll mill to obtain a thick film magnet composition. The SmFeN powder used here has an average particle size of 5 μm and a maximum particle size of 10 μm. To this thick film magnet composition, an organic solvent (terpineol) was added to adjust the viscosity to obtain a printing paste (magnet paste).

  Using this magnet paste for printing, printing was performed on the polyimide substrate with a predetermined pattern and film thickness by screen printing. The metal mask used for screen printing has a plate thickness of 200 μm. Thereafter, the printed thick film was cured by leaving it at a temperature of 200 ° C. for 30 minutes.

  When the cured pattern was confirmed with a digital microscope (microscope), as shown in FIG. 1, a strip-like pattern having a line width d of about 100 μm was arranged in parallel at equal intervals. When the thickness of the surface of a part (pattern for three pieces) shown in FIG. 1 is measured, it becomes as shown in FIG. 2, and the thickness of each printed belt-like pattern portion is a thick film of about 150 μm. It was confirmed that

Further, the magnetic properties of the thick film magnet thus produced are as shown in the following table. As is clear from this table, it was confirmed that practically sufficient magnetic performance was obtained even in a minute shape having a diameter of 1 mm or less.

  Except for changing the mixing ratio of the resin composition and SmFeN powder in Example 1 as appropriate (the SmFeN powder content is 65 wt% to 95 wt%), the thickness of the predetermined pattern on the polyimide substrate is the same as in Example 1. A membrane magnet was produced. After the thick film was cured, pre-magnetization was performed on the printed thick film at 30 kOe.

  Each of the obtained thick film magnets was measured for magnetic properties using a vibrating sample magnetometer, and the results were as shown in FIGS. It was confirmed that when the content of the SmFeN powder is about 67 wt%, the magnetic properties of the ferrite magnet having practical magnetic properties equal to or higher than the residual magnetization (1.3 kG) can be obtained.

  Instead of the metal mask used in Example 1 for screen printing, a mesh type (mesh # 325) was used, and a thick film magnet was produced in the same manner. Although illustration of specific experimental results is omitted, the same magnetic characteristics as described above were obtained. Further, when a mesh type screen was used, it was confirmed that a thick film magnet having a minimum size of 30 μm × 30 μm and a maximum thickness of 20 μm could be produced by one printing. And when the film thickness beyond that is required, printing may be performed a plurality of times.

A magnet paste was printed on the polyimide substrate by the same procedure as in Example 1. Then, the printed thick film was cured in a magnetic field. Specifically, as shown in FIG. 5, a substrate 3 on which a magnet paste is printed is placed on a plate-like permanent magnet 1. On the permanent magnet 1, another permanent magnet 4 is arranged via a spacer 2. By making the magnetic poles of the opposing surfaces of the permanent magnets 1 and 4 different, a magnetic field perpendicular to the substrate 3 is generated. As the permanent magnets 1 and 4 for orientation, for example, SmCo magnets can be used. When cured in this state, a thick film magnet oriented in a predetermined direction is produced. Table 2 shows magnetic properties of isotropic (orientation magnetic field: 0 kG) and anisotropy (orientation magnetic field: 1.2 kG). As is apparent from this table, it was confirmed that the orientation effect was obtained in the thick film magnet in which 90 wt% of the same SmFeN powder was mixed. In the illustrated example, the substrate 3 is sandwiched between the two permanent magnets from both sides, but the permanent magnets may be installed only on one side.

  Next, in order to investigate the influence of the magnetic field on the orientation in the magnetic field, curing was performed in the magnetic field using magnetic materials having different surface magnet densities. Specifically, the orientation magnetic field was changed to 0 kG, 1.2 kG, and 2.3 kG, and the others were the same as those in Example 4.

  As a result, the surface state was as shown in FIG. In the case of 2.3 kG exceeding 1.2 kG, it can be confirmed that the line width is reduced and the film thickness is increased, and the pattern shape is broken. This is presumably because the magnetic field of the magnetic field at the time of orientation was strong, and a magnetic brush in which magnetic powders continued in a needle shape along the magnetic field was generated. Therefore, it was confirmed that the target line width and film thickness could not be produced when magnetized at 2.3 kG. In other words, it should be 1.2 kG or less.

It is a figure which shows an example of a pattern shape. It is a figure which shows a surface state. It is a figure which shows a magnetic characteristic. It is a figure which shows a magnetic characteristic. It is a figure explaining the orientation in a magnetic field. It is a figure which shows a surface state.

Claims (9)

A magnet paste composed by mixing at least SmFeN-based magnet powder, an adhesive and a solvent,
The magnet paste whose composition ratio of the said magnet powder is 67 wt% or more and 97 wt% or less. A magnet paste composed by mixing at least SmFeN-based magnet powder, an adhesive and a solvent,
The magnet paste whose composition ratio of the said magnet powder is 67 wt% or more and 90 wt% or less.   3. The magnet paste according to claim 1, wherein the magnet powder has an average particle size of 5 μm or less and a maximum particle size of 10 μm or less.   The magnet paste according to any one of claims 1 to 3, wherein the adhesive is an epoxy resin.   The magnet paste according to any one of claims 1 to 4, wherein the magnet paste is formed on a substrate by a printing method, and the film thickness after curing is from 10 μm to 500 μm. Thick film magnet.   The thick film magnet according to claim 5, wherein the substrate is a flexible substrate.   The thick film magnet according to claim 5 or 6, wherein a line width of a pattern printed on the substrate is in a range of 30 µm or more and 5 mm or less.   The thick film magnet according to any one of claims 5 to 7, wherein anisotropy is provided by curing in a magnetic field.   The thick film magnet according to claim 8, wherein a line width of a pattern printed on the substrate is in a range of 30 μm or more and 1 mm or less.

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