JP5676957B2 - A ceramic body with a conductive layer and a method for producing a ceramic body with a conductive layer. - Google Patents

Description

  The present invention relates to a ceramic body with a conductive layer and a method for producing a ceramic body with a conductive layer.

  A method of forming a conductive layer such as an electrode on a ceramic dielectric used for a capacitor, a resonator, or the like has been proposed in, for example, Patent Document 1 below.

In Patent Document 1, a paste in which glass and a metal material are mixed is applied to the surface of a ceramic body having BaTiO ₃ as a main crystal phase and fired to form a conductive layer (metal layer) containing Ag or Cu as a main component. Forming.

JP 2003-151847 A

In the conventional method as described in Patent Document 1, only a relatively low value is obtained for the bonding strength between the conductive layer and the ceramic body. Moreover, BaTiO ₃ described in Patent Document 1 has a low reactivity with Ba, Ag and Cu, which are highly reactive with glass and relatively easy to bond with the glass in the paste, and the entire ceramic body and conductive layer. Ti, which easily diffuses, has an atomic ratio of 1: 1. On the other hand, BaTi ₄ O ₉ has Ba: Ti of 1: 4, and the ceramic body having BaTiO ₃ as the main crystal phase has a relatively high bonding strength with the metal layer mainly composed of Ag, Cu, or the like. small. Conventionally, when a conductive layer is formed on a ceramic body having BaTi ₄ O ₉ as a main crystal phase, there has been a risk that relatively many defects such as electrode peeling may occur. The present invention aims to solve such a problem.

In order to solve this problem, in the present application, a ceramic body with a conductive layer in which a conductive layer is bonded to the surface of the ceramic body, the ceramic body having BaTi ₄ O ₉ as a main crystal phase, , Ag or Cu as a main component, Si and Bi as glass components, and a junction region containing Ti and O as well as Bi as a main component is formed at the boundary between the conductive layer and the ceramic body. A ceramic body with a conductive layer is provided.

Further, a paste formed by mixing a glass powder containing at least Bi ₂ O ₃ and a conductive powder mainly composed of either Ag or Cu is applied to the surface of the ceramic body having BaTi ₄ O ₉ as the main crystal phase. And a firing step of firing the paste to form a conductive layer containing Ag or Cu as a main component and Si and Bi as glass components on the surface of the ceramic body, and having an average particle size And a method for producing a ceramic body with a conductive layer, wherein the conductive powder is 3 μm or less.

The bonding strength of the conductive layer to the ceramic body having BaTi ₄ O ₉ as the main crystal phase is relatively high. A ceramic body including a conductive layer bonded with a relatively strong bonding strength can be manufactured.

(A) is a schematic perspective view of the dielectric substrate which is one Embodiment of the ceramic body with a conductive layer of this invention, (b) was cut | disconnected in the direction perpendicular | vertical to one main surface of the dielectric substrate shown to (a). It is the schematic which expands and represents a cross section. It is the photograph (cross-sectional SEM photograph) obtained by observing one Embodiment of the ceramic body with a conductive layer of this invention with a scanning electron microscope. (a) And (b) is the analysis result by EPMA (Electron Probe Micro Analyzer) in the said cross section measured when acquiring the cross-sectional SEM photograph shown to Fig.2 (a). (a) And (b) is the photograph (cross-sectional SEM photograph) obtained by observing the cross section of the dielectric substrate different from the sample shown in FIG. 2 and FIG. 3 with a scanning electron microscope. (a) is a cross-sectional SEM photograph of a sample using an Ag powder having an average particle diameter of 5 μm as a powder to be mixed with the paste, and (b) is an average particle diameter of 2 μm as a powder to be mixed with the paste. It is a cross-sectional SEM photograph using Ag powder.

  Hereinafter, the ceramic body with a conductive layer and the method for producing the ceramic body with a conductive layer of the present invention will be described in detail.

  FIG. 1A is a schematic perspective view of a dielectric substrate 10 which is an embodiment of a ceramic body with a conductive layer of the present invention, and FIG. 1B is cut in a direction perpendicular to one main surface of the dielectric substrate 10. It is the schematic which expands and represents the done cross section.

The dielectric substrate 10 of the present embodiment has a conductive layer 14 containing Ag as a main component and Si and Bi as glass components on the surface of a ceramic substrate (ceramic body) 12 having, for example, BaTi ₄ O ₉ as a main crystal phase. Is formed. In FIG. 1A, the conductive layer 14 is deposited only in a desired region on the surface of the ceramic substrate 12. The conductive layer 14 is formed so that metal particles mainly composed of Ag or the like are bonded via a glass component.

In the present embodiment, “BaTi ₄ O ₉ is the main crystal phase” means that 50% or more of the crystal phase of the barium titanate-based crystal phase contained in the ceramic body is a BaTi ₄ O ₉ crystal. Say. In addition, “mainly composed of Ag” means containing Ag in a proportion of 50% by mass or more. The type and content ratio of the crystal phase contained in the ceramic body can be easily identified and quantified by a known analysis method of observing a cross section of the ceramic body using, for example, an X-ray diffractometer or an ICP emission spectroscopic analyzer. it can.

The conductive layer 14 may be formed in a state of being attached to the surface of the ceramic substrate 12 using, for example, a conventionally known thick film paste method. Specifically, for example, a predetermined amount of Ag powder and glass powder are weighed, and each of the above powders is mixed with a mixer to prepare a paste. The mixing ratio of Ag powder and glass powder in the paste is, for example, 98% by mass for Ag powder and 2.0% by mass for glass powder. The prepared paste may be applied to a portion of the ceramic surface to be brazed by screen printing or the like, and fired in the air to form the conductive layer 14. The glass powder contains, for example, SiO ₂ particles, Bi ₂ O ₃ particles, B ₂ O ₃ particles, and ZnO particles.

In the dielectric substrate 10, a junction region 18 containing Bi as a main component and containing Ti and O is formed at a boundary portion between the conductive layer 14 and the ceramic substrate 12. The phrase “containing Bi as a main component” means that, in a broad sense, the peak intensity of the spectrum representing Bi is the highest among the peak intensities measured by the well-known EPMA (Electron Probe Micro Analyzer) analysis.

  The content ratio (mass%) of each element such as Bi and Ti can be determined by a conventionally known EDS (energy dispersive X-ray analysis method) performed using, for example, a scanning electron microscope apparatus. For example, a spectrum corresponding to each atom can be obtained at an acceleration voltage of 15 kV using PHOENIX manufactured by EDAX, and calculated from the spectrum intensity corresponding to each atom. In this embodiment, 50 mass% or more of Bi is included.

  In the dielectric substrate 10 of the present embodiment, Ti and O are contained in the bonding region 18, and the bonding region 18 is mainly composed of a compound in which Bi, Ti, and O are combined.

When a conductive layer is formed using a metal paste containing a glass component on a conventional BaTiO ₃ dielectric, the glass component in the conductive layer is segregated to the ceramic body side because the Ba content is large, and this glass component is ceramic. The conductive layer is bonded to the ceramic body by bonding with Ba of the body. Ti was weakly reactive with Ag and the like, diffused throughout the interior of the ceramic body and the conductive layer, and hardly contributed to the bonding.

  In the dielectric substrate 10 of the present embodiment, Bi and Ti from the conductive layer gather and react with each other at the joint between the conductive layer 14 and the ceramic substrate 12, and Bi, Ti, and O are combined. Thus, the junction region 18 containing the compound as a main component is formed.

  In the dielectric substrate 10, the conductive layer 14 and the ceramic substrate 12 are bonded relatively firmly by the bonding region 18.

  In the present embodiment, the aperture ratio of the pores in the bonding region 18 is 40% or less. The pores in the bonding region 13 are holes that penetrate the bonding region 18 from the conductive layer 14 side to the ceramic substrate 12 side, and can be confirmed, for example, in a cross-sectional view using a scanning electron microscope apparatus. The opening ratio of the porosity in the bonding region 18 is the total length of the pore sizes along the parallel direction in a range of 10 μm along the direction parallel to the ceramic substrate 12 in a cross-sectional view. It is the size of the ratio (ie, total length / 10) of (μm). By setting the aperture ratio to 40% or less, the bonding strength of the conductive layer 14 to the ceramic substrate 12 can be made relatively high.

  The dielectric substrate 10 includes a first portion 16 containing Si as a main component and containing Ba inside the conductive layer 14. The first portion 16 is a portion in which Ba of the ceramic substrate 12 is contained in the glass component included in the paste for forming the conductive layer 14. In the present embodiment, the first portion 16 also contains Zn contained in the paste.

  Of each region obtained by dividing the conductive layer 14 in the thickness direction, the first region closer to the surface of the ceramic substrate 12 is closer to the thickness direction than the second region far from the surface of the ceramic substrate 12. The occupation area ratio of the first portion 16 in the cross-sectional view by the parallel plane is large.

  That is, the first portion 16 segregates on the surface side of the ceramic substrate 12, and a part of the first portion 16 is bonded to the bonding region 18 and a portion of the ceramic substrate 12. In the present embodiment, the first portion 16 also contributes to the bonding between the conductive layer 14 and the ceramic substrate 12, and the first portion 16 segregates on the surface side of the ceramic substrate 12, so that a relatively high bonding is achieved. Realizes strength. The first portion 16 can be confirmed, for example, by observing a cross section of the conductive layer 14 with a scanning electron microscope. For example, by performing image processing on this electron microscope imaging layer, the ratio of the area of the first portion 16 to the area of the surrounding metal phase mainly composed of Ag can be calculated relatively easily.

  For example, in the cross-sectional view of FIG. 1B, a straight line L1 that passes through the highest point of the conductive layer 14 and is parallel to the main surface of the ceramic substrate 12 is 50% from the main surface of the ceramic substrate 12 to the highest point of the conductive layer 14. When the straight line L2 is parallel to the main surface of the ceramic substrate 12 and passes through the height position, the region sandwiched between the surface of the ceramic substrate 12 and the straight line L1 is sandwiched between the first region S1, the straight line L1, and the straight line L2. The region corresponds to the second region S2. The area occupied by the first portion 16 in this cross section is larger in the first region than in the second region.

  In the dielectric substrate 10, the area occupied by the first portion 16 in the second region S2 is, for example, less than 20% by mass. The first portion 16 is a portion formed by reacting the glass component with Ba of the ceramic substrate 12 when the conductive layer 14 is formed. By forming the first portion 16, Si and O are intensively distributed in the first portion 16. As a result, in the dielectric substrate 10 of the present embodiment, the area occupancy of the first portion 16 in the second region is relatively low at less than 20% by mass.

SiO ₂ or the like which is a compound of Si and O, Si and O contributes to the bonding between the conductive layer 14 and the ceramic substrate 12. For example, when SiO ₂ is exposed on the surface of the conductive layer 14, The wettability with respect to the surface solder (for example, SnAgCu solder) is relatively greatly reduced. In the present embodiment, the first portion 16 is formed in the first region S1, and the glass component is concentrated in the first region S1. Therefore, the second region S2 and thus the first portion 16 exposed on the surface of the conductive layer 14 is relatively small.

  Ti is relatively easy to oxidize. In the dielectric substrate, if Ti is exposed on the surface of the conductive layer, oxidation also proceeds from the exposed portion toward the inside, and the conductive layer 14 may be deteriorated. In addition, when the oxidation progresses and the bonding portion between the conductive layer 14 and the ceramic substrate 12 is oxidized, the bonding strength between the conductive layer 14 and the ceramic substrate 12 is reduced. In the dielectric substrate 10 of the present embodiment, even when Ti of the ceramic substrate 12 diffuses into the conductive layer 14, the dielectric substrate 10 segregates in the bonding region 18 formed in the bonding portion between the ceramic substrate 12 and the conductive layer 14, and the conductive layer 14 The Ti component exposed on the surface is relatively small. For this reason, in the dielectric substrate 10 of this embodiment, the oxidation of the surface of the conductive layer 14 is relatively small, and the progress of oxidation toward the inside is suppressed.

In the dielectric substrate 10 of the present embodiment, the bonding strength of the conductive layer 14 to the ceramic substrate 12 is relatively large as 400 N / mm ² or more, although the thickness of the conductive layer 14 is relatively large as 40 μm or more and 70 μm or less. It has become.

  The dielectric substrate 10 of the present embodiment may be manufactured by the following method, for example.

First, for example, a ceramic substrate 12 having a main crystal phase of BaTi ₄ O ₉ is prepared.

The ceramic substrate 12 can be formed as follows, for example. As raw material powder, BaCO ₃ , TiO ₂ and ZnO having a purity of 99% or more, and CuO powder having a purity of 98% or more were prepared, weighed a predetermined amount, mixed and pulverized, and the obtained powder was 1000 to 1150 ° C. Hold at temperature for 1 hour or longer and calcine. The temperature increase rate during calcination is an average temperature of 50 to 200 ° C./hour at a temperature of 800 ° C. or higher. The calcined powder is pulverized to a median diameter of 0.5 to 2.0 μm. A binder is added to the calcined powder after pulverization, and after forming into a predetermined shape by a known method such as press molding or a doctor blade method, the binder is removed so that the carbon amount after debinding is 0.1% by weight or less. The binder removal condition is maintained at 400 to 800 ° C. for 20 hours or more. After debinding, the temperature is raised at a rate of temperature rise of 20 to 300 ° C./hour in the air or an atmosphere containing oxygen, and baked at 1050 to 1300 ° C. for 5 to 30 hours. For example, the ceramic substrate 12 can be manufactured through the above processes.

  The surface of the ceramic substrate 12 is polished through a process using a surface grinding machine. In this polishing step, the surface of the ceramic substrate 12 including at least the region where the paste is applied is polished so that the arithmetic average surface roughness Ra is in the range of 0.4 μm to 1.5 μm. By polishing the surface within this range, the bonding strength of the conductive layer to the ceramic body can be made relatively high while the film thickness of the conductive layer is made relatively uniform.

  Thereafter, the polished partial conductive layer 14 of the ceramic substrate 12 is formed. For the formation (metallization process) of the conductive layer 14, a conventionally known thick film paste method can be used.

In this metallization treatment, for example, a predetermined amount of Ag powder and glass powder are weighed, and a vehicle in which a binder such as ethyl cellulose is dissolved in an organic solvent such as terpineol and the above powder are mixed with a mixer to prepare a paste. The mixing ratio of the Ag powder and the glass powder is, for example, 98 mass% for the Ag powder and 2.0 mass% for the glass powder. The prepared paste may be applied to a portion of the ceramic surface to be brazed by screen printing or the like, and fired in the air to form the conductive layer 14. The glass powder contains, for example, SiO ₂ particles, Bi ₂ O ₃ particles, B ₂ O ₃ particles, and ZnO particles.

  Thereafter, the conductive layer 14 is formed by firing in an air atmosphere. More specifically, after slowly raising the temperature from room temperature to 840 ° C. over 90 minutes in a baking furnace, the temperature of 840 ° C. is maintained for 20 minutes, and the temperature is lowered to room temperature in a short time of about 30 minutes. Through this firing step, it is possible to obtain the dielectric substrate 10 in which the ceramic substrate 12 and the conductive layer 14 are bonded, in which the bonding region 18 is formed in the bonding portion.

  Bi and Ti are known to form compounds at a temperature of about 900 ° C. On the other hand, for example, at a temperature of 900 ° C. or higher, the glass component starts to vaporize and bubbles are generated. Therefore, if the temperature is 900 ° C. or higher, the bonding strength is lowered. For this reason, paste baking has been conventionally performed in a temperature range of 800 to 850 degrees C. for a short time of about 10 minutes. In this embodiment, since the temperature is slowly raised to a temperature of about 840 degrees over a sufficiently long time, the glass paste can move sufficiently. In the paste, not only Bi and Ti but also a plurality of elements including Bi, Ti, and O are mixed, and the condition temperature for forming the compound containing Bi and Ti is 900 ° C. It is below. For this reason, by maintaining a temperature range of about 840 ° C., which is close to 900 ° C., for a relatively long time, the bonding region 18 containing Bi, Ti, and O becomes the bonding portion between the ceramic substrate 12 and the conductive layer 14. Formed over a relatively wide area.

  Note that the particle size of the Ag powder included in the paste when forming the conductive layer 14 is 3.0 μm or less, preferably 2.0 μm or less. By setting the particle size of the Ag powder to 3.0 μm or less, the density of the movement path of Bi, O, and Si is increased, and Bi, O, and Si are distributed in a wider range on the surface of the ceramic substrate 12 at a high density. To reach.

  Examples of the present invention will be described below, and examples of the effects of the present invention will be described.

First, the result of observing a cross section of an example of the dielectric substrate of the above embodiment will be described. FIG. 2 is a photograph (cross-sectional SEM photograph) obtained by observing a cross-section of the dielectric substrate manufactured through the above-described process with a scanning electron microscope. FIGS. 3A and 3B are analysis results by EPMA (Electron Probe Micro Analyzer) in the cross section measured when the cross-sectional SEM photograph shown in FIG. 2A is acquired. Scanning electron microscope
For example, using S-800 manufactured by Hitachi, the image was taken at an acceleration voltage of 15 kV.

  3A is a diagram showing the intensity of the characteristic X-ray of each element at point A shown in FIG. 2, and FIG. 3B is the intensity of the characteristic X-ray of each element at point B shown in FIG. FIG. A point A shown in FIG. 2 corresponds to the bonding region 18 in the above embodiment, and a point B shown in FIG. 2 corresponds to the first portion 16 in the above embodiment. As can be seen from FIG. 3A, the point A portion of FIG. 2 corresponding to the bonding region 13 contains Bi as a main component and contains Ti and O. It can be seen that a compound of Bi and Ti is formed at the boundary between the ceramic substrate and the conductive layer. Further, as can be seen from FIG. 3B, the point B in FIG. 2 corresponding to the first portion 16 contains Si as a main component and Ba. It can be seen that the ceramic substrate 12 and the conductive layer 14 are bonded together by the glass component in the conductive layer 14.

  4 (a) and 4 (b) are photographs (cross-sectional SEM photographs) obtained by observing a cross section of a dielectric substrate different from the sample shown in FIGS. 2 and 3 with a scanning electron microscope. is there. FIG. 4A is an SEM photograph of a sample using Ag powder having an average particle diameter of 5 μm as powder to be mixed with the paste, and FIG. 4B is an average particle diameter as powder mixed with the paste. Is an SEM photograph using 2 μm Ag powder.

Compared to FIG. 4A, it can be confirmed that in FIG. 4B, the aperture ratio of the pores in the bonding region 18 formed in the bonding portion between the ceramic substrate 12 and the conductive layer 14 is smaller. . The Ag particles used in the paste used for forming the conductive layer 14 preferably have a relatively small average particle size, for example, an average particle size of 3.0 μm or less.
Also, as a result of evaluating the bonding strength of the conductive layer 14 for each of the sample shown in FIG. 4A and the sample shown in FIG. 4B, the bonding strength of the sample shown in FIG. In the sample shown in FIG. 4B, the average was about 511N. For the evaluation of the bonding strength, a Cu pin was bonded to the surface of the conductive layer formed on the ceramic substrate via solder, and when this pin was pulled in a uniaxial direction, the strength when the Cu pin was peeled was measured. . An average value obtained by measuring 10 points for each material was obtained. The opening ratio of the pores in the bonding region 18 is related to the bonding strength between the ceramic substrate 12 and the conductive layer 14, and the bonding strength is higher as the area of the bonding region 18 is larger.

DESCRIPTION OF SYMBOLS 10 Dielectric substrate 12 Ceramic substrate 14 Conductive layer 16 1st part 18 Joining area | region

Claims (7)

A ceramic body with a conductive layer in which a conductive layer is bonded to the surface of the ceramic body,
The ceramic body has BaTi ₄ O ₉ as a main crystal phase,
The conductive layer includes Ag or Cu as a main component, Si and Bi as glass components,
A ceramic body with a conductive layer, wherein a junction region containing Ti and O and containing Bi as a main component is formed at a boundary portion between the conductive layer and the ceramic body. Inside the conductive layer has a first portion containing Si as a main component and containing Ba,
Of each region obtained by dividing the conductive layer into two in the thickness direction, the first region closer to the surface of the ceramic body is closer to the thickness direction than the second region far from the surface of the ceramic body. 2. The ceramic body with a conductive layer according to claim 1, wherein the area occupied by the first portion in a cross-sectional view by a parallel plane is large.   3. The ceramic body with a conductive layer according to claim 1, wherein Zn is contained in the first portion of the conductive layer and the ceramic body. 4.   4. With a conductive layer according to claim 1, wherein an opening ratio of pores in the bonding region is 40% or less in a cross-sectional view taken along a plane parallel to the thickness direction of the conductive layer. Ceramic body. 5. The conductive layer according to claim 1, wherein a thickness of the conductive layer is 40 μm or more and 70 μm or less, and an adhesive strength of the conductive layer to the ceramic body is 400 N / mm ² or more. With ceramic body. Application in which a paste formed by mixing a glass powder containing at least Bi ₂ O ₃ and a conductive powder containing either Ag or Cu as a main component is applied to the surface of a ceramic body having BaTi ₄ O ₉ as a main crystal phase. Process,
Firing the paste, and forming a conductive layer containing Ag or Cu as a main component and containing Si and Bi as a glass component on the surface of the ceramic body,
A method for producing a ceramic body with a conductive layer, wherein the conductive powder having an average particle diameter of 3 μm or less is used.   Prior to the applying step, the surface of the ceramic body including at least the region where the paste is applied is polished to an arithmetic average surface roughness Ra of 0.4 μm or more and 1.5 μm or less. Item 7. A method for producing a ceramic body with a conductive layer according to Item 6.