JPH05234739A - Paint and layered inductor using the same - Google Patents

Abstract

PURPOSE:To provide a layered inductor using paint having high powder filling rate, excellent processability, and no necessity of adding plasticizer. CONSTITUTION:Organic binder required for ferrite paint for constituting a ferrite layered body 11 and organic binder required for conductive paint for constituting a conductor 12 are mixed with nitrocellulose resin modified by at least one type of -COOalpha (where alpha is H, K or Na) and -SO3beta (where beta is K or Na) and polyetherpolyurethane resin having a glass transition temperature of 40 deg.C or lower, the conductor 12 is disposed in the body 11 to constitute a layered body 100 of a basic construction of a layered inductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a basic structure of a laminated body obtained by laminating and sintering a magnetic layer such as a surface mounting inductor element or an impedance element and a coil conductor layer. For a laminated inductor and a laminated inductor using the same.

[0002]

2. Description of the Related Art In recent years, with the rapid miniaturization and weight reduction of electronic devices, there is a tendency for electronic circuits and electronic parts constituting them to be further miniaturized. Therefore, for inductors such as inductor elements and impedance elements, which occupy important positions in circuit construction, chip-type elements having a layered structure capable of surface mounting are becoming mainstream. Laminated inductors that are usually used by mounting them on a printed wiring board, etc. are composed of a magnetic layer formed by coating a magnetic film formed from soft magnetic ferrite fine powder and a binder, conductive fine powder and a binder. It is obtained by alternately laminating a conductor layer formed by coating a conductor film generated from (1) to form a laminate, and then sintering the laminate.

By the way, factors affecting the performance of such a laminated inductor include physical properties of ferrite fine powder and conductive fine powder which are main raw materials, and are indispensable for forming a coating film of these fine powders. The physical properties of the binder may be mentioned.
The physical properties required for this binder should be extremely important, and the main factors are that it has mechanical strength that can sufficiently correspond to the manufacturing process and that it can impart appropriate flexibility. It has various properties such as the ability to impart pressure-bonding properties during lamination and the ability to completely perform the debinding process performed as a pre-sintering treatment at low temperatures.

Examples of binders satisfying these requirements include non-aqueous binders, that is, nitrocellulose, ethyl cellulose, polyvinyl butyral, etc. in a system using an organic solvent as a dispersion medium. Furthermore, in order to give flexibility,
In addition to this, various plasticizers are commonly used in combination.

[0005]

However, it has been found that the binder used in the conventional laminated inductor has various drawbacks in making the inductor smaller and higher in performance. For example, firstly, in order to further reduce the size while ensuring the same performance, it is necessary to improve the powder filling rate of the magnetic layer and the conductive layer. There is a problem in that the dispersibility of the powder is poor when the coating film is laminated for each layer represented by the powder and the silver-palladium mixed powder, and therefore it is not possible to expect a high powder filling rate.

Secondly, conventional binders generally have a high glass transition temperature, so that they are poor in flexibility and require the addition of a plasticizer. Therefore, in order to improve the filling rate of the coating film, there remains a problem of how to reduce the added amount.

The present invention has been made in view of the above circumstances, and its technical problem is to provide a coating material which has a high powder filling rate and is excellent in processability and handling, and which does not require addition of a plasticizer. It is to provide a used laminated inductor.

[0008]

According to the present invention, there is provided a ferrite coating material comprising a soft magnetic ferrite powder for forming a ferrite coating film of a laminated inductor and an organic binder as raw materials and an organic solvent as a dispersion medium. The organic binder is a nitrocellulose resin modified with at least one of -COOα (where α is H, K, or Na) and -SO ₃ β (where β is K or Na), and a glass transition. A ferrite coating material containing a polyether polyurethane resin having a temperature of 40 ° C. or lower is obtained.

Further, according to the present invention, there is provided a conductive coating material comprising a metal powder for forming a conductive coating film of a laminated inductor and an organic binder as raw materials and an organic solvent as a dispersion medium. The agent is -COOα (where α is H, K,
Or Na), and -SO ₃ β (where β is K or Na).
A conductive coating material containing a nitrocellulose resin modified with at least one of the above and a polyether polyurethane resin having a glass transition temperature of 40 ° C. or lower can be obtained.

Further, according to the present invention, a ferrite coating film containing a soft magnetic ferrite powder and an organic binder, and a conductive coating film containing a metal powder and an organic binder interposed in the ferrite coating film are provided. In the laminated inductor having the above, the organic binder of at least one of the ferrite coating film and the conductive coating film is -COOα (where α is H, K, or N).
a), and -SO ₃ β (where β is K or Na), a laminated inductor made of a mixture of a nitrocellulose resin modified with at least one kind and a polyether polyurethane resin having a glass transition temperature of 40 ° C or lower. can get.

[0011]

The present invention improves the organic binder used in the conventional laminated inductor to provide a small-sized and high-performance laminated inductor. This organic binder has the functions described below.

First, a --COOα (where α is H, K, or Na) group introduced as a side chain of a nitrocellulose resin which is a binder component, or --SO ₃ β (where β is K.
Alternatively, since the Na) group is sufficiently oriented to the surface of the ferrite fine powder having a hydrophilic surface or the conductive metal fine powder represented by silver-palladium, excellent powder dispersion characteristics can be obtained. This means that the packing density of the ferrite coating film and the conductive coating film is improved.

Secondly, another binder component, polyether polyurethane resin, has a glass transition temperature of 40.degree.
Because of the following, when this polyether polyurethane resin is used as a mixture with a nitrocellulose resin, the flexibility of the coating film can be obtained in a practically sufficient degree. This allows
Appropriate coating film flexibility and pressure-bonding property can be obtained, and it becomes unnecessary to exclude and add a plasticizer which causes a reduction in coating film density. That is, the packing density is improved between the coating films.

Thirdly, since all binder components have ether bond sites in the molecular chain, they are easily subjected to oxidative decomposition at a relatively low temperature, and therefore the debinding process proceeds rapidly. To do.

Due to the first to third actions as described above, the powder filling density of the magnetic coating film and the conductive coating film, which are indispensable elements for downsizing of the laminated inductor, can be improved, and excellent processing is achieved. Handleability is obtained.

[0016]

EXAMPLES The paint of the present invention and the laminated inductor using the same will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a laminated body 100 forming a basic structure of a laminated inductor according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the appearance of the laminated body 100. There is something. The laminated body 100 (and the laminated inductor) is generally configured to be connected,
Here, for simplification, in addition to showing a single component, a part of the conductor 12 is emphasized.

As shown in the figure, the laminated body 100 includes a ferrite laminated body 11 obtained by laminating a ferrite coating film obtained by forming and drying a ferrite coating material containing ferrite powder and an organic binder as main components, and a metal. A conductor coating comprising a fine conductor powder and an organic binder as a main component, and a conductor coating obtained by laminating and drying the conductor coating. The conductor coating is formed on the ferrite coating. The layers are alternately laminated, and the conductors 12 are provided in several layers in the ferrite laminate 11.

The laminated inductor is such a laminated body 1
00 is dried and integrally sintered, and thereafter, as shown in FIG. 3, film-shaped electrode terminals 31A and 31B are provided on the end surface of the laminated body 100.

Further, the organic binder required for the ferrite coating material forming the ferrite laminate 11 of the laminated inductor of the present invention is -COOα (where α is H, K or Na), and -SO ₃ β (however, β is a mixture of a nitrocellulose resin modified with at least one of K and Na) and a polyether polyurethane resin having a glass transition temperature of 40 ° C. or lower. In addition, the organic binder required for the conductive paint forming the conductor 12 of the laminated inductor is also -COO.
α (where α is H, K, or Na), and -SO ₃ β
(However, β is K or Na) A mixture of a nitrocellulose resin modified with at least one kind and a polyether polyurethane resin having a glass transition temperature of 40 ° C. or lower.

Of these, the binder component nitrocellulose resin has an average degree of polymerization of 20 to 110 and a nitrogen content of 10.
It is in the range of 7 to 12.2% and has as a side chain-
The concentration of the COO α (where α is H, K, or Na) group is set within the range of 0.01 to 0.75 mmol / g, and the concentration of —SO ₃ β (where β is K or Na) group is adjusted. It is desirable to set it in the range of 0.005 to 0.30 mmol / g. If these concentration ranges fall below the respective lower limit concentrations, the improvement of the packing density of the powder will be impaired, and even if the respective upper limit concentrations are exceeded, gelation of the coating material will occur, so exceeding the concentration range is preferable. Absent. -COOα introduced as a side chain of nitrocellulose resin (however, α
Is H, K, or Na) group, or -SO ₃ β (where β is K or Na) group is the surface of ferrite fine powder having a hydrophilic surface or conductive fine powder represented by silver-palladium. Is sufficiently oriented, it is possible to obtain excellent powder dispersion characteristics. Thereby, the packing density of the coating film is improved.

On the other hand, the polyether polyurethane resin used as the organic binder may be a polyether polyurethane having an ether bond site in the main chain and has a glass transition temperature of 40 ° C. or lower. If a polyether polyurethane resin having a glass transition temperature of higher than 40 ° C. is used, it is difficult to impart flexibility without adding a plasticizer, so this temperature condition is also important.
That is, when the polyether polyurethane resin, which is another binder component, has a glass transition temperature of 40 ° C. or lower, when this polyether polyurethane resin is mixed with a nitrocellulose resin, the coating film is practically sufficient. Flexibility can be obtained. As a result, appropriate coating film flexibility and pressure-bonding property can be obtained, and it becomes unnecessary to exclude and add a plasticizer that causes a reduction in coating film density. That is, as a result, the packing density between the coating films is improved.

Further, the mixing ratio of the nitrocellulose resin and the polyether polyurethane resin which form the organic binder is preferably within the range of 1: 9 to 7: 3. Here, if the mixing ratio of the nitrocellulose resin is too low,
Even if the improvement of the dispersibility of the soft magnetic ferrite fine powder or the metallic fine powder is impaired and the mixing ratio of the polyether polyurethane resin is too small, the flexibility of the coating film is not sufficiently imparted, which is not preferable. By the way, since all binder components have an ether bond site in the molecular chain, they are easily subjected to oxidative decomposition at a relatively low temperature, and the debinding process proceeds rapidly. The powder packing density of the magnetic coating film and the conductive coating film, which are indispensable factors for improvement, can be improved, and excellent processability can be obtained such that the laminating step can be performed quickly.

The physical properties of the laminated inductor of the present invention containing such an organic binder component will be described below together with those of the comparative example. However, by making the first to fourth examples applicable to the laminated inductor of the present invention and not applying the first to fourth comparative examples to the laminated inductor of the present invention, To compare and contrast. However, each of the multilayer inductors was prepared by including a ferrite coating film or a conductor coating film having a different coating composition, and in Tables 1 to 8 described below, the ferrite coating film and the conductor coating film are unique. In addition to showing various compositions and blending amounts, various properties of the coating film are evaluated before and after the binder removal treatment.

The laminated inductor as the first embodiment contains a ferrite coating film containing an organic binder. The ferrite coating composition is made into a coating material by a pressure kneader and a sand grinder, dried by a doctor blade method, and dried. Is formed to have a thickness of 70 μm. Table 1
Is the gloss measurement by a gloss meter and the flexibility test by the bending test for the film of the ferrite coating composition. Shows.

[0026]

[Table 1]

The laminated inductor as the second embodiment has a silver-palladium conductor coating film containing an organic binder. The conductor coating composition is made into a coating material by a pressure kneader and a sand grinder, and the silk screen printing method is used. By 0.3
An electrode pattern of mm × 2 mm is created, dried, and formed into a film having a thickness of 10 μm. The pattern accuracy of this film formation is observed by a microscope.
Furthermore, after drying by the doctor blade method using the same paint, the film was formed into a silver-palladium paint composition having a thickness of 10 μm. The results of determining the binder removal completion temperature by a balance method after the binder test and the binder removal treatment are shown.

[0028]

[Table 2]

The laminated inductor as the third embodiment is formed in the same manner as the ferrite coating composition included in the laminated inductor of the first embodiment except that the ferrite coating composition is changed to the composition shown in Table 3. It was done. That is,
Table 3 shows the results of the evaluation and the preparation for the film formation of the ferrite coating composition.

[0030]

[Table 3]

The laminated inductor as the fourth embodiment has the silver-palladium conductive material provided in the laminated inductor of the second embodiment except that the silver-palladium conductor coating composition is changed to the composition shown in Table 4. The film is formed in the same manner as the body coating composition. That is, Table 4 shows the results of preparation and evaluation for the film formation of the silver-palladium coating composition.

[0032]

[Table 4]

On the other hand, the laminated inductor as the first comparative example has the same ferrite coating composition as that of the laminated inductor of the first embodiment except that the ferrite coating composition is changed to the composition shown in Table 5. The film was formed, and Table 5 shows the results of preparation and evaluation for the film formation of the ferrite coating composition.

[0034]

[Table 5]

The laminated inductor as the second comparative example has the silver-palladium conductive material provided in the laminated inductor of the second embodiment except that the silver-palladium conductor coating composition is changed to the composition shown in Table 6. A film was formed in the same manner as the body coating composition, and Table 6 shows the results of preparation and evaluation for the film formation of the silver-palladium coating composition.

[0036]

[Table 6]

The laminated inductor as the third comparative example was formed into a film in the same manner as the ferrite coating composition included in the laminated inductor of the first embodiment, except that the ferrite coating composition was changed to the composition shown in Table 7. Table 7 shows the results of preparation and evaluation for film formation of the ferrite coating composition.

[0038]

[Table 7]

The multilayer inductor as the fourth comparative example has the silver-palladium conductive material provided in the multilayer inductor of the second embodiment except that the silver-palladium conductor coating composition is changed to the composition shown in Table 8. The film was formed in the same manner as the body coating composition, and Table 8 shows the results of preparation and evaluation for the film formation of the silver-palladium coating composition.

[0040]

[Table 8]

The physical properties of the laminated inductors having the respective coating films formed by the coating compositions according to the first to fourth examples and the first to fourth comparative examples as components are described below. Table 9 shows the evaluation results.

[0042]

[Table 9]

In Table 9, the glossiness is an index of the degree of dispersibility of the ferrite powder or the conductor powder, and the larger the value, the better the dispersion state. Flexibility is a measure of the flexibility of the ferrite or conductor layer. If this flexibility is insufficient in the ferrite layer or the conductor layer, cracks may occur during sheet formation, or crimping defects may occur when the sheets are multilayered, resulting in lower workability and product defects. It is not preferable because it causes inconvenience such as generation. Further, the debinding temperature is preferably as low as possible in order to prevent delamination due to volume expansion or contraction due to the redox phenomenon of the conductor powder that occurs during sintering of the conductor layer. The lower the direct current resistance value of the conductor layer is, the more preferable. Therefore, if the direct current resistance value is reduced, it is possible to expect the electric conductor layer to be stabilized in addition to the thinning of the conductor layer. Furthermore, the pattern accuracy is the flexibility of the shape of the conductor layer,
It is a measure of thinning and miniaturization, and is an essential element for downsizing and high performance of multilayer inductors. This pattern accuracy strongly depends on the dispersed state of the conductive paint.

As can be seen from Table 9, if the dispersibility of the ferrite powder or the conductor powder is improved as in the laminated inductors of the first to fourth embodiments, it will be very significant in manufacturing the laminated inductor. is there. Specifically, in the ferrite layer, the ferrite powder filling rate can be improved, and also in the conductor layer, the conductor powder filling rate can be improved, so that the homogenization of the mixed powder is promoted. It As a result, the formation of a film under high temperature and high humidity is very stable, and it becomes possible to sufficiently suppress the occurrence of troubles such as conductor damage and disconnection. Therefore, the laminated inductor according to each of the embodiments is extremely effective for miniaturization and high reliability.

Next, laminated inductors of the fifth embodiment and the fifth comparative example are prepared by using the coating compositions of the above-mentioned first to fourth embodiments and the first to fourth comparative examples, respectively. They were created and their characteristics were compared.

The laminated inductor of the fifth embodiment is shown in Table 1.
Using the ferrite coating material (related to the first embodiment) having the composition shown in Table 1 and the conductor coating material (related to the second embodiment) having the composition shown in Table 2 at a temperature of 930 ° C., integrally sintering, In addition to having the basic structure shown in FIG. 3, the magnetic permeability of the ferrite layer is set to μ, and as shown in Table 10, the inductance characteristics are satisfied.

[0047]

[Table 10]

On the other hand, in the laminated inductor of the fifth comparative example, the ferrite coating material having the composition shown in Table 7 (related to the third comparative example) and the conductive coating material having the composition shown in Table 8 (the fourth comparative example) were used. Regarding the above), a laminated inductor is produced in the same manner as in the fifth embodiment except that and are used. Also in this case, the magnetic permeability of the ferrite layer is set to μ so as to satisfy the inductance characteristics as shown in Table 10.

Table 11 shows the results of comparison between the laminated inductor of the fifth embodiment and the laminated inductor of the fifth comparative example in terms of magnetism and volume ratio.

[0050]

[Table 11]

According to Table 11, the laminated inductor of the fifth embodiment can be significantly downsized as compared with the fifth comparative example of the same performance prepared by the conventional method. I understand. That is, first, the inductance L of the inductor element is proportional to the magnetic permeability μ of the ferrite layer and the magnetic path cross-sectional area S, respectively. Therefore, if the magnetic permeability μ increases under the condition that the inductance L is constant, the cross-sectional area S that is the volume element of the element can be reduced. Second
In addition, the film thickness of the conductor layer is inversely proportional to the DC resistance value under the condition that the DC resistance value of the conductor layer is constant. Therefore, if the DC resistance value of the conductor layer is reduced, the film thickness of the conductor layer, which is a volume element of the element, can be reduced. As described above, the multilayer inductor according to the fifth embodiment can be made smaller and have higher performance than the conventional one.

In each of the above embodiments, the screen printing method or the doctor blade method was used for forming the ferrite coating film for the ferrite layer or the conductive coating film for the conductor layer. A forming method such as an extrusion forming method or an injection forming method may be adopted.

[0053]

As described above, according to the laminated inductor of the present invention, it is smaller and higher in performance than the conventional one, and
In addition, it is possible to provide a laminated inductor that can achieve high reliability. In particular, since the organic binder used in the laminated inductor is improved, it is possible to improve the powder filling density of the magnetic coating film and the conductive coating film, which are indispensable factors for downsizing the laminated inductor. It is possible to eliminate the need for a plasticizer that causes a reduction in coating film density. This allows
Since it is possible to improve the workability by imparting appropriate coating film flexibility and pressure-bonding property, it is possible to give great convenience to the manufacturing process of the small laminated inductor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a laminated body forming a basic structure of a laminated inductor which is an embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of the laminate shown in FIG.

FIG. 3 is a perspective view showing an appearance of a laminated inductor of the present invention.

[Explanation of symbols]

 11 ferrite laminated body 12 conductor 100 laminated body

Claims (3)

[Claims] 1. A ferrite coating material comprising a soft magnetic ferrite powder for forming a ferrite coating film of a laminated inductor and an organic binder as a raw material and containing an organic solvent as a dispersion medium, wherein the organic binder is --COOα. (However, α is H, K, or Na), and -SO ₃ β (where β is K or Na) modified nitrocellulose resin, and a polyether polyurethane having a glass transition temperature of 40 ° C. or lower. A ferrite coating material containing a resin. 2. A conductive coating material comprising metal powder for forming a conductive coating film of a laminated inductor and an organic binder as raw materials and an organic solvent as a dispersion medium, wherein the organic binder is --COOα. (However, α is H, K, or Na), and -SO ₃ β (where β is K or Na) modified nitrocellulose resin, and a polyether polyurethane having a glass transition temperature of 40 ° C. or lower. A conductive paint comprising a resin. 3. A laminated inductor having a ferrite coating film containing soft magnetic ferrite powder and an organic binder, and a conductive coating film containing metal powder and an organic binder interposed in the ferrite coating film. Then, the organic binder of at least one of the ferrite coating film and the conductive coating film is -COOα (where α is H, K, or Na), and -SO ₃ β (where β is K or Na). 2. A laminated inductor, comprising: a nitrocellulose resin modified with at least one of the above) and a polyether polyurethane resin having a glass transition temperature of 40 ° C. or lower.