JP3203492B2 - Paint and multilayer inductor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated structure obtained by laminating and sintering a magnetic layer such as a surface mount inductor element and an impedance element and a conductor layer for a coil. And a multilayer inductor using the same.

[0002]

2. Description of the Related Art In recent years, with the rapid miniaturization and weight reduction of electronic equipment, electronic circuits and electronic components constituting the electronic equipment have been tending to be further miniaturized. Therefore, for the inductor such as the inductor element and the impedance element which occupy an important position in the circuit construction, a chip type element having a laminated structure capable of surface mounting is becoming mainstream. A laminated inductor usually used in a form mounted on a printed wiring board or the like is composed of a magnetic layer in which a soft magnetic ferrite fine powder and a magnetic film formed from a binder are coated and laminated, a conductive fine powder and a binder. A laminate is formed by alternately laminating a conductor film formed by laminating a conductor film and a conductor layer obtained by laminating a film, and then sintering the laminate.

The factors that affect the performance of such a laminated inductor include the 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. Physical properties of the binder.
The physical properties required of this binder are extremely important, and the main factors are that it has sufficient mechanical strength to cope with the manufacturing process, and that it can provide appropriate flexibility. Various characteristics such as being capable of imparting pressure bonding property during lamination and being capable of completely performing a debinding agent treatment performed as a pretreatment for sintering at a low temperature are given.

[0004] Binders satisfying these requirements include nitrocellulose, ethylcellulose, polyvinyl butyral and the like in non-aqueous systems, that is, in systems using an organic solvent as a dispersion medium. Furthermore, in order to provide flexibility,
In addition, various plasticizers are generally used in combination.

[0005]

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

Second, conventional binders generally have a high glass transition temperature, and therefore have poor flexibility, and require the addition of a plasticizer. Therefore, there is a problem of how to reduce the amount of the coating film in improving the filling rate of the coating film.

The present invention has been made in view of such circumstances, and a technical problem thereof is to provide a paint having a high powder filling rate, excellent workability, and requiring no addition of a plasticizer. It is to provide a laminated inductor used.

[0008]

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

Further, according to the present invention, there is provided a conductive paint comprising a metal powder and an organic binder as a raw material for forming a conductive coating film of a multilayer inductor 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 paint 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 containing a soft magnetic ferrite powder and an organic binder and a conductive coating containing a metal powder and an organic binder interposed in the ferrite coating are provided. Wherein 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 a laminated inductor made of a mixture of a nitrocellulose resin modified with at least one of —SO ₃ β (where β is K or Na) and a polyether polyurethane resin having a glass transition temperature of 40 ° C. or less. can get.

[0011]

According to the present invention, a small and high-performance multilayer inductor can be provided by improving the organic binder used in the conventional multilayer inductor. This organic binder has the function described below.

First, a -COOα (where α is H, K, or Na) group introduced as a side chain of a nitrocellulose resin as a binder component, or —SO ₃ β (where β is K
Alternatively, since the Na) group sufficiently directs the surface of a ferrite fine powder having a hydrophilic surface or a 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 or the conductive coating is improved.

Second, the polyether polyurethane resin, which is another binder component, has a glass transition temperature of 40 ° C.
Because of the following, when this polyether polyurethane resin is mixed with a nitrocellulose resin and used, sufficient coating flexibility can be obtained for practical use. This allows
A proper coating film flexibility and pressure-bonding property can be obtained, and a plasticizer which causes a reduction in the coating film density is excluded, and it is not necessary to add a plasticizer. That is, the packing density is improved between the coating films.

Third, since all the binder components have an ether bond site in the molecular chain, they are easily oxidatively decomposed at a relatively low temperature, so that the debinding agent treatment proceeds rapidly. I do.

[0015] By the first to third functions, the powder filling density of the magnetic coating film and the conductive coating film, which are indispensable elements for miniaturization of the multilayer inductor, can be improved, and excellent processing can be achieved. Handleability is obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coating of the present invention and the multilayer 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 which is 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. Note that the multilayer body 100 (and the multilayer inductor) is generally connected and configured,
Here, for the sake of simplicity, a single component is shown, and a part of the conductor 12 is emphasized.

As shown in the figure, a laminate 100 includes a ferrite laminate 11 obtained by laminating a ferrite coating film obtained by forming and drying a ferrite paint containing a ferrite powder and an organic binder as main components, A conductive paint obtained by laminating and drying a conductive paint containing a fine powder and an organic binder as main components, and a conductive paint film obtained by drying. The conductors 12 are laminated alternately and the conductors 12 are interposed in several layers in the ferrite laminate 11.

The multilayer inductor has such a laminate 1
After drying and integrally sintering 00, as shown in FIG. 3, the laminated body 100 is provided with electrode terminals 31A and 31B in the form of films on the end face.

Further, the organic binder required for the ferrite paint forming the ferrite laminate 11 of the multilayer inductor of the present invention is -COOα (where α is H, K, or Na), and -SO ₃ β (where, 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 multilayer inductor is also -COO.
α (where α is H, K, or Na), and —SO ₃ β
(Where β is K or Na) a mixture of 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.

Among them, the nitrocellulose resin as a binder component has an average degree of polymerization of 20 to 110 and a nitrogen content of 10.
In the range of 7 to 12.2%, having as a side chain;
The concentration of the COOα (where α is H, K, or Na) group is within the range of 0.01 to 0.75 mmol / g, and the concentration of the —SO ₃ β (where β is K or Na) group is It is desirable to be within 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 each exceeds the upper limit concentration, gelling of the paint will occur, so exceeding the concentration range is preferable. Absent. -COOα introduced as a side chain of the nitrocellulose resin (however, α
Is an H, K, or Na) group or —SO ₃ β (where β is K or Na) group is a surface of a ferrite fine powder having a hydrophilic surface or a conductive fine powder represented by silver-palladium. , And excellent powder dispersion characteristics can be obtained. Thereby, the packing density of the coating film is improved.

On the other hand, the polyether polyurethane resin used for the organic binder may be a polyether polyurethane having an ether bond site in the main chain and having a glass transition temperature of 40 ° C. or lower. When a resin having a glass transition temperature of more than 40 ° C. is used as the polyether polyurethane resin, it is impossible to provide flexibility without adding a plasticizer, and therefore, this temperature condition is also important.
That is, when the polyether polyurethane resin as another binder component has a glass transition temperature of 40 ° C. or less, when this polyether polyurethane resin is used in combination with a nitrocellulose resin, the coating film becomes sufficiently practical. Flexibility can be obtained. As a result, appropriate coating film flexibility and press-fitting property can be obtained, and a plasticizer that causes a reduction in the coating film density is excluded, so that it is not necessary to add a plasticizer. 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 for forming the organic binder is preferably in the range of 1: 9 to 7: 3. Here, if the mixing ratio of the nitrocellulose resin is too small,
It is not preferable that the dispersibility of the soft magnetic ferrite fine powder or the metallic fine powder is impaired, and that if the mixing ratio of the polyether polyurethane resin is too small, the coating film cannot be sufficiently imparted with flexibility. By the way, since all the binder components have an ether bond site in the molecular chain, they are easily oxidized and decomposed at a relatively low temperature, and the debinding process proceeds quickly. The powder filling density of the magnetic coating film and the conductive coating film, which are indispensable elements, is improved, and excellent workability such as rapid lamination process can be obtained.

In the following, the physical properties of the multilayer inductor of the present invention containing such an organic binder component will be described together with those of a comparative example. However, the first to fourth embodiments are applicable to the multilayer inductor of the present invention, and the first to fourth comparative examples are not applicable to the multilayer inductor of the present invention. Are compared. However, each of the laminated inductors was prepared with a ferrite coating and a conductor coating having different paint compositions, and in Tables 1 to 8 described below, the specific characteristics of the ferrite coating and the conductor coating are respectively shown. In addition to the above, the composition and the amount of the composition should be shown, and the various properties of the coating film should be evaluated before and after the binder removal treatment.

The laminated inductor according to the first embodiment has a ferrite coating film containing an organic binder. The ferrite coating composition is made into a paint by a pressure kneader and a sand grinder, dried by a doctor blade method, and dried. Was formed to have a thickness of 70 μm. Table 1
After performing a gloss measurement with a gloss meter and a flexibility test by a bending test for the film formation of the ferrite paint composition, the debinding completion temperature was determined by a ripening method after the debinding treatment. Is shown.

[0026]

[Table 1]

The laminated inductor according to the second embodiment has a silver-palladium conductive film containing an organic binder. The conductive paint composition is made into a paint by a pressure kneader and a sand grinder. By 0.3
An electrode pattern of mm × 2 mm is formed and dried, and a film is formed to a thickness of 10 μm. The pattern accuracy of this film formation is observed with a microscope.
After drying by the doctor blade method using the same paint, a glossiness measurement using a gloss meter and a bending test can be performed on a silver-palladium paint composition formed to a thickness of 10 μm. The figure shows the results obtained by performing a flexibility test and then performing a debindering process to determine a debindering completion temperature by a ripening method.

[0028]

[Table 2]

The multilayer inductor according to the third embodiment is formed in the same manner as the ferrite coating composition of the multilayer inductor according to 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 preparation and evaluation for the film formation of the ferrite paint composition.

[0030]

[Table 3]

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

[0032]

[Table 4]

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

[0034]

[Table 5]

The laminated inductor according to the second comparative example is the same as the laminated inductor of the second embodiment except that the silver-palladium conductive paint composition is changed to the composition shown in Table 6. The film was formed in the same manner as the body paint composition, and Table 6 shows the results of preparation and evaluation of the film formed with the silver-palladium paint composition.

[0036]

[Table 6]

A laminated inductor as a third comparative example was formed in the same manner as the ferrite coating composition provided 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 the preparation and evaluation for the film formation of the ferrite paint composition.

[0038]

[Table 7]

The multilayer inductor according to the fourth comparative example is similar to the silver-palladium conductive coating provided in the multilayer inductor according to the second embodiment except that the composition of the silver-palladium conductive paint is changed to the composition shown in Table 8. The film was formed in the same manner as the body paint composition. Table 8 shows the results of the preparation and evaluation of the film formed with the silver-palladium paint composition.

[0040]

[Table 8]

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

[0042]

[Table 9]

In Table 9, the gloss indicates an index of the degree of dispersibility of the ferrite powder or the conductive powder, and the larger the value, the better the dispersion state. Flexibility is a measure of the flexibility of a ferrite or conductor layer. If the flexibility is insufficient in the ferrite layer or the conductor layer, cracks may occur during sheet formation or poor crimping may occur when multiplying the sheet, resulting in reduced workability and poor product quality. It is not preferable because it causes inconvenience such as generation. Further, the debinding completion temperature is preferably as low as possible in order to prevent delamination accompanying volume expansion or contraction caused by the oxidation-reduction phenomenon of the conductive powder generated during sintering of the conductive layer. It is preferable that the DC resistance value of the conductor layer is also lower. If the DC resistance value is reduced, it is possible to expect the stabilization of the electric conductivity in addition to the thinning of the conductor layer. Furthermore, the pattern accuracy is determined by the flexibility of the conductor layer,
This is a measure of thinning and miniaturization, and is an indispensable factor for miniaturization and high performance of multilayer inductors. This pattern accuracy strongly depends on the dispersion state of the conductive paint.

As can be seen from Table 9, if the dispersibility of the ferrite powder or the conductive powder is improved as in the laminated inductors of the first to fourth embodiments, it is extremely significant in the production of the laminated inductor. is there. Specifically, in the ferrite layer, the filling factor of the ferrite powder can be improved, and also in the conductor layer, the filling ratio of the conductor powder can be improved, so that the uniformity of the mixed powder is promoted. You. As a result, the formation of a film under high temperature and high humidity is very stable, so that occurrence of troubles such as conductor damage and disconnection can be sufficiently suppressed. Therefore, the multilayer inductor according to each embodiment is extremely effective for miniaturization and high reliability.

Next, using the respective paint compositions of the first to fourth embodiments and the first to fourth comparative examples, the laminated inductors of the fifth embodiment and the fifth comparative example are respectively formed. They were created and their characteristics were compared.

The laminated inductor according to the fifth embodiment is shown in Table 1.
And sintering at a temperature of 930 ° C. using a ferrite paint (related to the first embodiment) having the composition shown in Table 2 and a conductor paint (related to the second embodiment) having the composition shown in Table 2. In addition to the basic configuration shown in FIG. 3, the magnetic permeability of the ferrite layer was set to μ, and the inductance characteristics were satisfied as shown in Table 10.

[0047]

[Table 10]

On the other hand, the laminated inductor according to the fifth comparative example is composed of a ferrite paint having the composition shown in Table 7 (related to the third comparative example) and a conductor paint having the composition shown in Table 8 (the fourth comparative example). A laminated inductor was produced in the same manner as in the fifth embodiment, except that the above-mentioned) was used. Here, the magnetic permeability of the ferrite layer is set to μ, and the inductance characteristics are satisfied as shown in Table 10.

Table 11 shows the results of comparing the multilayer inductor of the fifth embodiment with the multilayer 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 achieve a significant reduction in size as compared with the fifth comparative example of the same performance produced 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 fixed, the cross-sectional area S, which is a volume element of the element, can be reduced. Second
In addition, the 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 thickness of the conductor layer, which is a volume element of the element, can be reduced. Thus, the multilayer inductor according to the fifth embodiment can be smaller and have higher performance than the conventional one.

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

[0053]

As described above, according to the multilayer inductor of the present invention, the size and the performance are smaller than those of the conventional inductor.
Moreover, it is possible to provide a multilayer inductor with high reliability. In particular, since the organic binder used in the multilayer inductor has been improved, the powder filling density of the magnetic coating film and the conductive coating film, which are indispensable elements for miniaturization of the multilayer inductor, has been improved. It is possible to eliminate the need for a plasticizer that causes a reduction in the coating film density. This allows
Since the processability can be improved by imparting appropriate coating film flexibility and crimpability, a great deal of convenience can be given to the manufacturing process of the small multilayer inductor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a laminated body constituting a basic configuration of a laminated inductor according to 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 the appearance of the multilayer inductor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Ferrite laminated body 12 Conductor 100 laminated body

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-34326 (JP, A) JP-A-64-79929 (JP, A)

Claims (3)

(57) [Claims] 1. A ferrite paint comprising a soft magnetic ferrite powder for forming a ferrite coating film of a multilayer 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 nitrocellulose resin modified with at least one of —SO ₃ β (β is K or Na), and polyether polyurethane having a glass transition temperature of 40 ° C. or less. A ferrite paint characterized by containing a resin. 2. A conductive paint comprising a metal powder and an organic binder for forming a conductive coating film of a multilayer inductor 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 nitrocellulose resin modified with at least one of —SO ₃ β (β is K or Na), and polyether polyurethane having a glass transition temperature of 40 ° C. or less. A conductive paint containing a resin. 3. A laminated inductor having a ferrite coating containing a soft magnetic ferrite powder and an organic binder, and a conductive coating containing a metal powder and an organic binder interposed in the ferrite coating. there are, at least one of the organic binder of the ferrite coatings and the conductive coating, -COOarufa (where, alpha is H, K, or Na), and -SO ₃ beta (where, beta is K or Na A) 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.