JP2007063060A - Coating material for ceramic green sheet and its manufacturing method, ceramic green sheet, and electronic component provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating material for a ceramic green sheet by which the ceramic green sheet low in density and also excellent in dispersibility of ceramic powders can surely be obtained. <P>SOLUTION: The coating material for the ceramic green sheet contains ceramic powder, a binder resin, a good solvent for the binder resin and a poor solvent for the binder resin. The coating material for the ceramic green sheet has 90-600 Pa s viscosity in 0.1 sec<SP>-1</SP>shear rate and 320-1,400 Pa s viscosity in 0.01 sec<SP>-1</SP>shear rate, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating material for a ceramic green sheet and a method for producing the same, a ceramic green sheet, and an electronic component including the same.

  Inductors, capacitors, thermistors, varistors, and the like are known as laminated electronic components in which ceramic layers and conductor layers are alternately laminated. In these multilayer electronic components, the conductor layer is conventionally formed by a printing method such as screen printing, so the thickness of the conductor layer is generally smaller than the thickness of the ceramic layer. there were.

  In recent years, with the miniaturization of electronic devices, further miniaturization is required for electronic components mounted on them. However, in spite of this trend toward miniaturization, electronic components can be used in a variety of environments. Durability is unlikely to occur even when a large current flows. Is required.

  In order to cope with a large current, the thickness of the conductor layer may be increased. In this case, in order to maintain the size of the entire electronic component, the ceramic layer has a thickness corresponding to the increase in the thickness of the conductor layer. Thinning is required. That is, in an electronic component that can handle a large current, the conductor layer is thicker and the ceramic layer is often thinner than in the past.

  Here, the multilayer electronic component as described above has a conductive paste layer printed on a ceramic green sheet containing ceramic powder, a binder, or the like so as to form a predetermined pattern, and a plurality of these are stacked and pressed. In many cases, the resultant laminate is fired.

  However, when an electronic component is manufactured by such a method, if an attempt is made to form a thick conductor layer and a thin ceramic layer as described above, the thick conductive paste layer is strongly applied to the thin ceramic green sheet during pressing. Since it bites in, the ceramic green sheet after pressing is greatly deformed, and thus tends to have a large stress. If it becomes like this, in manufacture of an electronic component, it will become easy to generate | occur | produce a crack and a delamination between a conductor layer and a ceramic layer resulting from the stress of the ceramic green sheet mentioned above at the time of baking of a laminated body or after baking. For this reason, an electronic component having a thick conductor layer and a thin ceramic layer in order to reduce the size while supporting a large current may cause a short circuit between the conductor layers due to the above-described cracks and delamination. In many cases, the characteristics are insufficient.

  As a method of reducing such inconvenience, there is a method of reducing the ratio of the ceramic powder in the ceramic green sheet, that is, a method of reducing the density of the ceramic green sheet. If it carries out like this, it will become possible to deform | transform flexibly with respect to the penetration of the electrically conductive paste layer in the case of manufacture of an electronic component, and it will become difficult to generate | occur | produce the above stress.

As a method of reducing the density of the ceramic green sheet, as a coating material for forming the ceramic green sheet, an inorganic powder, a binder solution composed of a mutually compatible binder, a dispersion medium and a plasticizer, and a compatibility with the binder However, there is known a method using a slurry composition for a green sheet containing a compatible additive in the binder solution (see Patent Document 1).
JP 2004-168642 A

  By the way, when reducing the density of the ceramic green sheet as described above, the ceramic powder needs to be uniformly dispersed in the sheet in order to obtain a homogeneous ceramic layer. This is because if the ceramic powder is unevenly distributed in the ceramic green sheet, defects such as poor insulation may occur locally in the obtained ceramic layer. In this regard, the slurry composition for a green sheet having the composition described in Patent Document 1 may have insufficient dispersibility depending on the type of ceramic powder and binder used. In addition, it has been difficult to stably obtain a highly dispersed ceramic green sheet.

  Therefore, the present invention has been made in view of such circumstances, and provides a coating for a ceramic green sheet that can reliably obtain a ceramic green sheet having a low density and excellent dispersibility of ceramic powder. Objective. Another object of the present invention is to provide a method for producing such a ceramic green sheet, a ceramic green sheet obtained thereby, and an electronic component comprising a ceramic layer formed from the ceramic green sheet.

To achieve the above object, a ceramic green sheet slurry of the present invention, a ceramic powder, a binder resin, wherein the good solvent of the binder resin, and a poor solvent for the binder resin, shear rate of 0.1 sec ^- The viscosity at ¹ is 90 to 600 Pa · s, and the viscosity at a shear rate of 0.01 sec ⁻¹ is 320 to 1400 Pa · s.

  Here, the good solvent for the binder resin is a solvent that can dissolve the binder resin well, and the poor solvent for the binder resin is a solvent that hardly dissolves the binder resin or does not dissolve it at all. Whether the solvent is a good solvent or a poor solvent for the binder resin can be determined, for example, based on the following solubility parameter (SP value). That is, it can be determined that a solvent having an SP value such that the absolute value of the difference from the SP value of the binder resin is 1.35 or less is “a good solvent for the binder resin”. On the other hand, a solvent having an SP value such that the absolute value of the difference from the SP value of the binder resin exceeds 1.35 can be determined as a “poor solvent for the binder resin”. In addition, as a good solvent, what has the absolute value of the difference of SP value with binder resin being 0.5 or less is more preferable.

  The coating material for a ceramic green sheet of the present invention includes a poor solvent that hardly dissolves the binder resin in addition to a good solvent that can dissolve the binder resin satisfactorily. When producing a ceramic green sheet using such a coating material for ceramic green sheet, the poor resin dispersed in the paint is better than the good solvent while the binder resin and the ceramic powder are mixed well by the good solvent. By being vaporized later, a large number of fine holes are formed in the sheet. As a result, a low-density ceramic green sheet can be obtained.

In addition, the ceramic green sheet paint of the present invention has a viscosity of 90 to 600 Pa · s at a shear rate of 0.1 second ⁻¹ and a viscosity of 320 to 1400 Pa · s at a shear rate of 0.01 second ⁻¹ . . Usually, the viscosity of the liquid material is adjusted at a shear rate of about 10 to 100 seconds ^−1, but when the present inventors have conducted a detailed study, the range of the shear rate that is significantly lower than the normal range as described above. It was found that the dispersibility of the ceramic powder in the obtained green sheet becomes extremely good by defining the viscosity of the coating material for ceramic green sheet.

  Therefore, according to the ceramic green sheet coating composition of the present invention having the above-described configuration, a ceramic green sheet having excellent dispersibility as well as the above-described characteristics of low density can be reliably obtained. The ceramic green sheet thus obtained is less likely to have stress caused by the biting of the conductor layer even when a conductor layer thicker than the sheet is formed during the manufacture of the electronic component. It becomes.

A method for producing a ceramic green sheet paint according to the present invention is a method for producing the ceramic green sheet paint according to the present invention. The ceramic powder, the binder resin, and the binder resin good solvent And mixing the poor solvent of the binder resin so that the viscosity at a shear rate of 0.1 sec- ¹ is 90 to 600 Pa · s and the viscosity at a shear rate of 0.01 sec- ¹ is 320 to 1400 Pa · s. It is characterized by including. According to the ceramic green sheet paint thus obtained, a ceramic green sheet having a low density and a high dispersion can be obtained as described above.

  In the method for producing a coating material for a ceramic green sheet of the present invention, it is preferable to adjust the viscosity at the specific shear rate by changing the blending amount of the ceramic powder and / or the blending amount of the good solvent. Thereby, since a compounding ratio can be adjusted on the basis of the weight of a ceramic powder, the viscosity adjustment in a desired shear rate becomes easy and workability | operativity becomes favorable.

  The present invention also provides a ceramic green sheet obtained using the ceramic green sheet of the present invention. Since such a ceramic green sheet is obtained from the above-mentioned paint for ceramic green sheets of the present invention, it has a low density and excellent dispersibility of the ceramic powder. Even if it is formed, it becomes extremely difficult to generate stress.

Furthermore, the electronic component of the present invention preferably includes a ceramic layer formed from the ceramic green sheet of the present invention, and includes a conductor layer and a ceramic layer, and the ceramic layer is the ceramic green sheet of the present invention. The conductor layer thickness T ₁ (μm) and the ceramic layer thickness T ₂ (μm) satisfy T ₁ / T ₂ ≧ 1.0.

  Since the electronic component having the above-described structure includes the ceramic layer formed from the ceramic green sheet of the present invention, the conductor layer is provided with a conductor layer that is the same as or thicker than the ceramic layer. The stress of the ceramic layer due to the bite is greatly reduced. As a result, the electronic component of the present invention has very few cracks and delamination between the conductor layer and the ceramic layer.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the coating material for ceramic green sheets which can obtain a low density and highly dispersed ceramic green sheet reliably. In addition, it is possible to provide a method for producing such a ceramic green sheet, a ceramic green sheet obtained thereby, and an electronic component including a ceramic layer formed from the ceramic green sheet.

  Preferred embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  First, the configuration of a multilayer inductor that is an example of a multilayer electronic component will be described with reference to FIGS. FIG. 1 is a perspective view showing a multilayer inductor according to the present embodiment. FIG. 2 is a diagram for explaining a cross-sectional configuration of the multilayer inductor according to the present embodiment. FIG. 3 is an exploded perspective view of the multilayer body included in the multilayer inductor according to the present embodiment. The multilayer inductor 1 is obtained by applying a ceramic green sheet formed from a ceramic green sheet paint according to a preferred embodiment described later.

  As shown in FIG. 1, the multilayer inductor 1 includes a substantially rectangular parallelepiped inductor element 10 and a pair of terminal electrodes (external electrodes) 11 and 12 formed on both side surfaces of the inductor element 10 in the longitudinal direction. With. The bottom surface of the inductor body 10 is a surface facing the external substrate when the multilayer inductor 1 is mounted on the external substrate (not shown).

  As shown in FIGS. 2 and 3, the inductor element body 10 is configured by laminating a plurality (12 in this embodiment) of ceramic layers A1 to A12, and a conductor pattern (conductor layer) B1 therein. To B10, through-hole electrodes C1 to C9, and a coil L including lead-out portions B1a and B10a. The actual multilayer inductor 1 is integrated to such an extent that the boundaries between the ceramic layers A1 to A12 cannot be visually recognized. As will be described later, the ceramic layers A1 to A12 are made of a fired product of a ceramic green sheet and function as an insulator.

  The ceramic layers A1 to A12 are insulators having electrical insulation, and are made of a fired product of a ceramic green sheet as described later. The ceramic layers A1 to A12 are mainly composed of ferrite (for example, Ni—Cu—Zn based ferrite, Ni—Cu—Zn—Mg based ferrite, Cu—Zn based ferrite, or Ni—Cu based ferrite). The ceramic layers A1 to A12 have a thickness of about 60 μm, for example.

  The conductor pattern B1 corresponds to approximately 5/8 turns of the coil L, and is formed in a substantially C shape on the ceramic layer A2. A lead-out portion B1a is integrally formed at one end of the conductor pattern B1. The lead-out part B1a of the conductor pattern B1 is drawn out to the edge of the ceramic layer A2, and its end is exposed on the end face of the ceramic layer A2. As a result, the lead-out part B1a is electrically connected to the terminal electrode 11. The other end of the conductor pattern B1 is electrically connected to a through-hole electrode C1 formed through the ceramic layer A2 in the thickness direction. For this reason, the conductor pattern B1 is electrically connected to one end of the adjacent conductor pattern B2 through the through-hole electrode C1 in a stacked state.

  The conductor patterns B2 to B9 correspond to approximately 3/4 turns of the coil L, and the conductor patterns B2, B4, B6, and B8 are substantially U-shaped on the ceramic layers A3, A5, A7, and A9, respectively. The conductor patterns B3, B5, B7, and B9 are formed in a substantially C shape on the ceramic layers A4, A6, A8, and A10. One end of each conductor pattern B2 to B9 includes a region electrically connected to each through-hole electrode C1 to C8 in a stacked state. The other ends of the conductor patterns B2 to B9 are electrically connected to the through-hole electrodes C2 to C9 formed through the ceramic layers A3 to A10 in the thickness direction, respectively. For this reason, each conductor pattern B2-B9 is electrically connected with the end of each conductor pattern B3-B10 which adjoins through each through-hole electrode C2-C9 in the laminated state.

  The conductor pattern B10 corresponds to approximately 7/8 turns of the coil L, and is formed in a substantially U shape on the ceramic layer A11. One end of the conductor pattern B10 includes a region electrically connected to each through-hole electrode C9 in a stacked state. A lead-out portion B10a is integrally formed at the other end of the conductor pattern B10. The lead-out part B10a of the conductor pattern B10 is drawn out to the edge of the ceramic layer A11, and its end is exposed on the end surface of the ceramic layer A11. As a result, the lead-out portion B10a is electrically connected to the terminal electrode 12.

Here, the thickness T ₁ of the conductor pattern in the inductor body 10 (thickness in the stacking direction, see FIG. 2) and the thickness T ₂ of the ceramic layers A1 to A12 (thickness in the stacking direction, see FIG. 2) , T ₁ / T ₂ ≧ 1.0 is preferable. That is, the thickness of the conductor patterns B1 to B10 is preferably equal to or greater than the thickness of the ceramic layers A1 to A12.

By doing so, the multilayer inductor 1 has a coil L having a large cross-sectional area, and can sufficiently cope with a large current. Further, since the distance between the adjacent conductor patterns becomes relatively small, the magnetic coupling between the turns in the coil L becomes strong, thereby increasing the inductor value. As a result, the number of turns of the coil L required for obtaining a desired inductance value can be reduced, and the multilayer inductor 1 can be easily reduced in size. From the viewpoint of obtaining these effects better, T ₁ / T ₂ is preferably 1.5 or more.

  As described above, the ceramic layers A1 to A12 are laminated, and the conductor patterns B1 to B10 are electrically connected to each other through the through hole electrodes C1 to C9, so that the number of turns is 7.5 turns. A coil L is formed. Here, each of the conductor patterns B1 to B10 and the lead-out portions B1a and B10a is formed by screen printing a conductor paste mainly composed of silver or nickel.

  Next, a manufacturing method of the multilayer inductor will be described with reference to FIG.

  FIG. 4 is a cross-sectional view schematically showing a part of the manufacturing process of the multilayer inductor according to a preferred embodiment, and is a diagram showing a multilayer structure including a ceramic green sheet and a conductive paste layer (conductive material layer). . Here, for convenience of explanation, a method for manufacturing a multilayer inductor will be described by taking as an example a structure including four ceramic layers and a three-layer conductor pattern provided therebetween.

  First, ceramic green sheets G1 to G4 for forming a ceramic layer are prepared (see FIG. 4A). These ceramic green sheets G1 to G4 constitute a ceramic layer of the multilayer inductor by firing. These ceramic green sheets G1-G4 are formed from the coating material for ceramic green sheets. First, a suitable ceramic green sheet paint will be described.

  The ceramic green sheet paint according to a preferred embodiment contains ceramic powder, a binder resin, a good solvent for the binder resin, and a poor solvent for the binder resin. The ceramic powder constituting the coating for the ceramic green sheet may be a ferrite as described above (for example, Ni—Cu—Zn based ferrite, Ni—Cu—Zn—Mg based ferrite, Cu—Zn based ferrite, or Ni—Cu based). A powder made of ferrite). The average particle size of the ceramic powder is preferably 0.06 to 0.6 [mu] m, and more preferably 0.1 to 0.6 [mu] m. The binder resin can be used without particular limitation as long as it is usually a resin material used by mixing with a ceramic material, and examples thereof include butyral, acrylic, and cellulose binder resins.

  As described above, the good solvent for the binder resin is a solvent that can dissolve the binder resin satisfactorily. Examples of such good solvents include ethanol, isobutyl alcohol, butyl acetate, xylene, toluene, acetone, methyl ethyl ketone, and the like. The mixed solvent is mentioned. These are preferably selected appropriately according to the type of the binder resin.

  The poor solvent for the binder resin is a solvent that is difficult to dissolve or cannot dissolve the binder resin. Examples of the poor solvent include mineral spirit, glycerin, ethylene glycol monoacetate, ethylene glycol, ethylene glycol diacetate, diethylene glycol, and mixed solvents thereof, and it is preferable to select appropriately according to the type of the binder resin. For example, in the case of a butyral binder resin, ethylene glycol, diethylene glycol, ethylene glycol monoacetate, ethylene glycol diacetate, kerosene, mineral spirit, etc. are preferred, and in the case of an acrylic binder resin, kerosene, mineral spirit etc. are preferred, cellulose In the case of a binder resin, ethylene glycol, glycerin, diethylene glycol and the like are preferable.

The coating material for ceramic green sheets containing the above components has a viscosity at shear rate (sialate) of 0.1 sec ⁻¹ (hereinafter referred to as “V _0.1 ”) of 90 to 600 Pa · s, and a shear rate of 0 The viscosity at _0.1 seconds ⁻¹ (hereinafter referred to as “V _0.01 ”) is 320 to 1400 Pa · s. Here, the viscosity of the coating material for ceramic green sheets can be measured with a conical disk viscometer.

By adjusting the viscosity of the coating material for the ceramic green sheet so as to be in the above range, a ceramic green sheet in which the ceramic powder is very well dispersed can be obtained. From the viewpoint of improving the dispersibility of the ceramic powder, V _0.1 of the ceramic green sheet coating is preferably 120 to 600 Pa · s, and V _0.01 is preferably 700 to 1400 Pa · s. .

  In addition, the coating material for ceramic green sheets of this embodiment may further contain a component that is usually included in the ceramic green sheet in addition to the above components. Examples thereof include plasticizers such as phthalate ester plasticizers, adipic acid ester plasticizers, and sebacic acid ester plasticizers. The amount of these other components added is preferably such that the viscosity of the coating for ceramic green sheets is within the above-described range. In addition, since the dispersing agent which is often contained in the ceramic green sheet coating material may excessively increase the density of the coating material, it is preferable to add a small amount, and it is desirable not to add as much as possible.

  Such a coating for ceramic green sheets can be prepared by mixing ceramic powder, a binder resin, a good solvent, a poor solvent, and other components as required. For example, it can be obtained by dissolving a binder resin in a good solvent and then mixing ceramic powder, a poor solvent and other components into the resulting solution. It is preferable to mix these components using, for example, a ball mill (20 to 200 liters).

And in the preparation of the coating material for ceramic green sheets, the blending amount and mixing time of these components are appropriately changed so that the V _0.1 and V _{0.01 of the} coating material are within the specific range described above. Adjust. For example, the viscosity of the coating material for ceramic green sheets can be adjusted by changing the blending amount of the ceramic powder and / or the blending amount of the good solvent. That is, V _0.1 or V _0.01 is measured while mixing the above components, and if the value is outside the above-mentioned specific range, ceramic powder or good solvent is added. It is preferable to adjust the viscosity. And the suitable coating material for ceramic green sheets is obtained by repeating this process until desired _V0.1 and _V0.01 are obtained.

  More specifically, the blending amount of each component is preferably adjusted so that the content of each component in the ceramic green sheet paint is within the following range. That is, in the total amount of the ceramic powder and the good solvent, the preferable content of the ceramic powder is 40 to 70% by mass, and more preferably 45 to 60% by mass. Moreover, preferable content of a good solvent is 25-55 mass%, More preferably, it is 30-50 mass%.

  Furthermore, the content of the binder resin is preferably 4 to 13 parts by mass, and more preferably 5 to 9 parts by mass with respect to 100 parts by mass of the ceramic powder. Furthermore, the content of the poor solvent is preferably 0.5 to 12 parts by mass and more preferably 3 to 9 parts by mass with respect to 100 parts by mass of the ceramic powder. In the ceramic green sheet paint, when each component is blended so as to satisfy the above content, the viscosity of the ceramic green sheet paint easily satisfies the above-described conditions. In this specification, values based on mass (mass%, parts by mass, etc.) are assumed to be substantially equivalent to values (weight%, parts by weight, etc.) based on weight (the same applies hereinafter).

  Hereinafter, a preferred method for manufacturing a multilayer inductor will be described with reference to FIG. 4 again. The ceramic green sheets G1 to G4 can be obtained, for example, by applying the above-described ceramic green sheet coating material on a substrate such as a PET film and then drying it. At this time, first, the good solvent in the paint volatilizes first, and the drying proceeds and the poor solvent volatilizes. Thus, innumerable minute holes are formed in the obtained ceramic green sheet. The obtained ceramic green sheets G1 to G4 may be peeled off from the base material, or may be used as they are after peeling off the base material after forming or laminating a conductive paste layer to be described later. Good.

Since the ceramic green sheets G1 to G4 thus obtained are formed using the ceramic green sheet paint as described above, there are many voids and the like due to volatilization of the poor solvent in the sheet. Contains. For this reason, it has the characteristic that it is a low density compared with the conventional ceramic green sheet. For example, when suitable, the density of the ceramic green sheets G1 to G4 is 2.61 to 3.35 g / cm ³ , more preferably 2.61 to 2.83 g / cm ³ , and still more preferably 2. 61 to 2.77 g / cm ³ .

Here, when the density of the ceramic green sheets G1 to G4 is less than 2.61, variation in thickness and characteristics of the obtained ceramic layer may easily occur. On the other hand, when the density exceeds 3.35 g / cm ³ , the flexibility of the ceramic layer becomes insufficient, and it is difficult to obtain sufficient characteristics to relieve stress during the manufacture of electronic components.

  After obtaining the ceramic green sheets G1 to G4 in this way, through holes are respectively formed by laser processing or the like in these predetermined positions, that is, positions where the through hole electrodes as described above are to be formed (not shown). .

  Next, the conductive paste layers P1 to P3 (see FIG. 4A) constituting the conductor pattern after firing are formed on the ceramic green sheets G1 to G4 by printing a conductive paste containing conductive powder and a binder. Form. These conductive paste layers P1 to P3 each have a pattern (for example, a shape like the conductor patterns B1 to B10 in FIG. 3) that can constitute a part of a coil in the multilayer inductor after lamination. At this time, the conductive paste is applied so as to fill the through holes described above. Thereby, in the baking mentioned later, a conductor pattern and a through-hole electrode will be formed simultaneously.

  Thereafter, the ceramic green sheets G1 to G4 are stacked (see FIG. 4A), and then pressure is applied in the stacking direction so that no gap is generated between the ceramic green sheets G1 to G4. (See FIG. 4B). As shown in the figure, in the laminate 20, the conductive paste layers P1 to P3 are in a state of being bitten into the adjacent ceramic green sheets G1 to G4 on both sides. In other words, the ceramic green sheets G <b> 1 to G <b> 4 have a shape that is greatly depressed in a region in contact with the conductive paste layers P <b> 1 to P <b> 3. However, since the ceramic green sheets G1 to G4 have the characteristic of low density as described above, even if they are in such a depressed state, the generation of stress is extremely small.

  Then, the obtained stacked body 20 is cut into chips, and then fired at a predetermined temperature (for example, about 870 ° C.) to form an inductor body. For example, the length of the inductor body in the longitudinal direction after firing is 2.0 mm, the width is 1.25 mm, and the height is 0.8 mm. By such firing, the ceramic green sheets G1 to G4 become ceramic layers, and the conductive paste layers P1 to P3 become conductor patterns. That is, the ceramic layer and the conductor pattern are composed of fired products of ceramic green sheets G1 to G4 and fired products of conductive paste layers P1 to P3, respectively.

  A multilayer inductor can be obtained by forming a terminal electrode for the inductor body. The terminal electrode is baked at a predetermined temperature (for example, about 700 ° C.) and electroplated after transferring an electrode paste mainly composed of silver, nickel, or copper to both end faces in the longitudinal direction of the inductor body. Can be formed. For this electroplating, Cu, Ni, Su or the like can be used.

  As described above, in the multilayer inductor manufacturing method of the present embodiment, the ceramic green sheets G1 to G4 are used as the material for forming the ceramic layer. The ceramic green sheets G1 to G4 are obtained by using the ceramic green sheet paint as described above, and have a characteristic that the density is lower than that in the past. For this reason, when the laminated body 20 is formed by pressing or the like, the ceramic green sheets G1 to G4 can be flexibly deformed in accordance with the shapes of the conductive paste layers P1 to P3, and the conductive paste layers P1 to P3. There is little generation of stress due to bite. As a result, cracks and delamination between the ceramic layer and the conductor layer due to the stress generated in the ceramic green sheet are hardly caused during firing or after firing.

  Further, since the ceramic green sheets G1 to G4 are obtained from the ceramic green sheet paint having a specific viscosity as described above, the ceramic powder is uniformly dispersed in the sheet. For this reason, the ceramic layer obtained from the ceramic sheets G1 to G4 is homogeneous. As a result, the obtained multilayer inductor has extremely few local insulation defects that have been easily caused by the uneven distribution of ceramic powder when the density of the ceramic green sheet is attempted.

  The multilayer inductor and the manufacturing method thereof according to the preferred embodiment have been described above. However, the present invention is not necessarily limited to the above-described embodiment, and modifications can be made as appropriate without departing from the spirit of the present invention.

  For example, in the multilayer inductor described above, the magnetic layer made of various ferrite materials is exemplified as the ceramic layer. However, the present invention is not limited to this, and a nonmagnetic layer made of a nonmagnetic material may be used.

  The present invention is not limited to the multilayer inductor described above, and can be applied without particular limitation as long as it has a structure in which conductor layers and ceramic layers are alternately stacked. Specifically, for example, a capacitor, a thermistor, a varistor, or a composite product thereof can be exemplified. Electronic components other than these inductors can be obtained by appropriately selecting the constituent material of the ceramic layer, the shape of the conductor layer, and the like suitable for each electronic component.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Preparation and Evaluation of Ceramic Green Sheet Paint]

(Examples 1-4, Comparative Examples 1-6)
First, a butyral resin as a binder resin was dissolved in toluene and isobutyl alcohol as good solvents. Next, Ni—Cu—Zn ferrite powder as a ceramic powder, ethylene glycol as a poor solvent, and a plasticizer were added to the obtained solution, and the mixture was placed in a ball mill and dispersed for 24 hours. The blending amount (parts by weight) of each component in each example or comparative example was as shown in Table 1.

Then, the ceramic green sheet slurry obtained, the viscosity when the viscosity at a shear rate of 0.1 sec ^-1 _{(V 0.1)} and 0.01 sec ^-1 _{(V 0.01)} Measured with a conical disk viscometer. The obtained V _0.1 and V _0.01 are collectively shown in Table 1.

［セラミックグリーンシートの作製及び評価］ Moreover, in the preparation of each ceramic green sheet paint, a part of each paint at the time of dispersion for 10 hours is extracted, and a coating film having a thickness of about 10 to 50 μm is formed on the glass surface using this. It observed with the microscope of 100 time. And the dispersibility of each ceramic green sheet coating material was evaluated by measuring the maximum value of the particle size of the ceramic powder contained in each coating material. The smaller the particle size, the better the dispersibility. The obtained results are shown in Table 1. In Table 1, the evaluation was performed based on the following criteria. In this evaluation, when the maximum particle size is 40 μm or less (A or B), it can be determined that the product has good dispersibility and is sufficient for practical use.
A: Maximum particle size is 20 μm or less B: Maximum particle size is more than 20 μm and 40 μm or less C: Maximum particle size is more than 40 μm and 60 μm or less D: Maximum particle size is larger than 60 μm

[Production and evaluation of ceramic green sheets]

  The ceramic green sheet paint of Example 2 was applied to a PET film by a doctor blade method so as to have a thickness of 45 μm, and then dried to obtain a ceramic green sheet.

The density of the obtained ceramic green sheet was measured and found to be 2.72 g / cm ³ . This is a value that is 14.2% lower than the ceramic green sheet obtained by using the ceramic green sheet paint having the same composition except that it does not contain ethylene glycol, which is a poor solvent. confirmed.
[Production and evaluation of multilayer inductors]

  After forming a plurality of ceramic green sheets obtained from the coating material for ceramic green sheets of Example 2, through holes were formed at desired positions using a laser. Then, on each ceramic green sheet, a conductive paste mainly composed of silver was applied through a metal mask to form a conductive paste layer having a predetermined pattern having a thickness of about 40 μm and a pattern width of 160 μm. . And the laminated body which incorporates the coil-like pattern which consists of an electrically conductive paste layer and a through hole was obtained by laminating | stacking each obtained ceramic green sheet. The number of turns of the obtained coiled pattern was 7.5 turns.

  Then, this laminated body was cut | disconnected so that a completion dimension might be length; 2.0mm, width | variety; 1.25mm, height; 0.8mm, and it was set as the single-piece | unit chip | tip. And after baking the obtained chip | tip at about 870 degreeC, after apply | coating the electrically conductive paste which has silver, copper, or nickel as a main component to both ends of a baked product, it baked at about 700 degreeC, and also by electroplating on it. Cu, Ni, and Sn plating were performed to form terminal electrodes. Thus, a multilayer inductor having a configuration as shown in FIGS.

As a result of analyzing the internal state of the obtained multilayer inductor by DPA, the thickness T ₁ of the conductor pattern is 21.8 μm, the width of the conductor pattern is 140 μm, and the interlayer distance T ₂ of this conductor pattern is 15. It was confirmed to be 6 μm. Thus, T ₁ / T ₂ of the obtained multilayer inductor was 1.4.

  Further, when the inductance of this multilayer inductor was measured, it was 1.03 μH, and when the DC resistance was measured, it was 0.11Ω. From this, it was found that even when the rated current was 0.5 A, the level was sufficient. These values are average values obtained by extracting 100 pieces from the multilayer inductor of the same lot and measuring them.

  Furthermore, 1000 pieces were extracted from the multilayer inductor of the same lot, and it was determined whether or not delamination or cracks were generated in the multilayer structure for all of these. As a result, of 1000 pieces, the ratio of occurrence of delamination was 0.8%, and the ratio of occurrence of cracks was 1.4%. All of these did not have an appearance problem.

  On the other hand, when the same evaluation was performed on a conventional multilayer inductor manufactured using a paint not containing a poor solvent, the occurrence rate of delamination or cracks was almost 100%.

  From this, it was found that the multilayer inductor obtained in this example has less occurrence of delamination and cracks, and is excellent in reliability and mass productivity as compared with the conventional case.

1 is a perspective view showing a multilayer inductor according to an embodiment. It is a figure for demonstrating the cross-sectional structure of the multilayer inductor which concerns on embodiment. 1 is an exploded perspective view of a multilayer body included in a multilayer inductor according to an embodiment. It is a figure for demonstrating the manufacturing method of the multilayer inductor which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer inductor, 10 ... Inductor body, 11, 12 ... Terminal electrode, A1-A12 ... Ceramic layer, B1-B10 ... Conductor pattern, C1-C9 ... Through-hole electrode, G1-G4 ... Ceramic green sheet, P1 ~ P3 ... conductive paste layer.

Claims (5)

Ceramic powder, binder resin, good solvent for the binder resin, poor solvent for the binder resin,
A ceramic green sheet paint having a viscosity of 90 to 600 Pa · s at a shear rate of 0.1 sec ⁻¹ and a viscosity of 320 to 1400 Pa · s at a shear rate of 0.01 sec ⁻¹ . Ceramic powder, binder resin, good solvent for the binder resin, and poor solvent for the binder resin,
Viscosity 90~600Pa · s next at a shear rate of 0.1 sec ^-1, and a viscosity at a shear rate of 0.01 sec ^-1 is characterized in that it comprises the step of mixing so that 320~1400Pa · s A method for producing a coating for a ceramic green sheet.   The method for producing a coating material for a ceramic green sheet according to claim 2, wherein the blending amount of the ceramic powder and / or the blending amount of the good solvent is changed to adjust the viscosity.   A ceramic green sheet obtained using the ceramic green sheet paint according to claim 1. Comprising a conductor layer and a ceramic layer;
The ceramic layer is formed from the ceramic green sheet according to claim 4,
An electronic component characterized in that a thickness T ₁ (μm) of the conductor layer and a thickness T ₂ (μm) of the ceramic layer satisfy T ₁ / T ₂ ≧ 1.0.

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