JP5142090B2 - Ceramic multilayer electronic component and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ceramic multilayer electronic component including an element body having ceramic as a main composition (main component) and a method for manufacturing the same.

  In a ceramic multilayer electronic component composed of a thermistor, a capacitor, an inductor, a LTCC (Low Temperature Co-fired Ceramics), a varistor or the like, and a composite thereof, an internal electrode is formed inside an element body made of ceramic. An internal electrode is exposed at a predetermined position on the end face of the element body, and after forming a base electrode thereon, a Ni layer and a Sn layer are provided by plating to form a terminal electrode. When the ceramic multilayer electronic component having such a configuration is mounted on, for example, a printed wiring board, the terminal electrode formed on the end surface of the element body in this way is provided on a predetermined wiring portion of the printed wiring board. Soldered to.

  Here, in the production of ceramic multilayer electronic components, when an element body made of ceramics is immersed in a plating solution for forming the Ni layer and the Sn layer, the fine pores existing in the element body and the base electrode are formed. In some cases, the plating solution may intrude and cause problems such as erosion of the ceramic body and deposition of plating metal on the surface of the ceramic body. Further, when the solder paste comes into contact with the element body, the flux contained in the solder paste directly reduces the element body, which may cause a problem of poor connection.

  In view of this, as a technique for suppressing problems caused by the penetration of the plating solution into the element body, a technique for forming a glass layer covering the surface of the element body has been proposed (see Patent Document 1).

JP-A-4-68502

  However, when the present inventor has conducted intensive research on such plating techniques including the above-described conventional technique, there are innumerable pores on the surface of the base electrode, which is a sintered body, and plating is performed on the base electrode. It has been found that a plating solution for forming a film may remain in the pores. If the plating solution remains in the pores of the base electrode in this way, the remaining plating solution expands due to the heat during soldering and the molten solder is scattered, resulting in poor connection (explosion failure). ) May occur.

  Therefore, the present invention has been made in view of the above circumstances, and its purpose is to prevent the plating solution from entering the element body and the base electrode, and to satisfactorily form the plating film and solder it. It is an object of the present invention to provide a ceramic multilayer electronic component and a method for manufacturing the same.

  In order to achieve the above object, a ceramic multilayer electronic component of the present invention includes an element body mainly made of ceramics, an internal electrode provided inside the element body, and a part thereof exposed on the end face of the element body, and an element body The base electrode formed on the end surface of the base electrode, a glass layer covering the exposed surface of the element body other than the base electrode forming portion, and a glass permeation layer formed by glass permeating the surface layer of the base electrode.

  According to the above configuration, the glass permeation layer is formed on the surface layer of the base electrode. Here, the “underlying electrode” refers to an electrode that becomes the underside of the plating film. The “surface layer” refers to a region inside the surface of the base electrode. Therefore, by forming the glass permeation layer on the surface layer of the base electrode, the pores formed in the surface layer of the base electrode are filled while maintaining the conductive surface of the base electrode. Therefore, it is possible to suppress the plating solution from remaining in the pores of the base electrode while forming the plating film on the base electrode. Further, since the exposed surface of the element body other than the base electrode forming portion is covered with the glass layer, the element body is prevented from being exposed to the plating solution. Accordingly, a good plating film is formed on the base electrode without the plating solution entering the element body.

  Preferably, the base electrode includes metal powder having an average particle size of 0.8 μm or more and 5 μm or less. When the particle size of the metal powder is smaller than 0.8 μm, the pores generated in the base electrode become excessively small, and the glass does not penetrate well into the base electrode, so that the surface is covered outside the surface of the base electrode. A glass layer is formed, and it tends to be difficult to form a plating film connected to the base electrode. In addition, if the particle size of the metal powder exceeds 5 μm, pores with a size comparable to the particle size are formed in the base electrode, the pore volume increases excessively, and the pores penetrate into the glass. Tend to fill well with layers.

  Furthermore, in order to achieve the above object, a method for manufacturing a ceramic multilayer electronic component according to the present invention is a method for effectively manufacturing a ceramic multilayer electronic component according to the present invention. Forming a laminated structure including an internal electrode embedded in the body and partially exposed at the end face of the element body; forming a base electrode by applying a conductive paste to the end face of the element body; A step of applying a glass slurry to the exposed surface of the element body other than the electrode forming portion to form a glass layer covering the exposed surface, and forming a glass permeation layer on the surface layer of the base electrode.

  According to the above configuration, since the formation of the glass layer on the exposed surface of the element body and the formation of the glass permeation layer on the inner surface of the base electrode are performed at the same time, plating on the element body without increasing the number of steps. It is possible to prevent the penetration of the solution and the remaining of the plating solution in the pores of the base electrode.

  Preferably, the conductive paste includes a metal powder, an organic binder, and a glass frit, and the content of the glass frit with respect to the total amount of the metal powder and the glass frit is not less than 0.5% by weight and not more than 8% by weight. is there. Since only the metal component and the glass component remain after firing, the content of the glass component with respect to the finally remaining solid content is specified. When the glass frit content is less than 0.5% by weight, pores may be easily generated in the base electrode to such an extent that it cannot be filled with the glass permeation layer. Further, if the glass frit content exceeds 8% by weight, the coverage of the base electrode by the plating film tends to decrease.

  Preferably, it is useful to fire the base electrode, the glass layer, and the glass permeation layer simultaneously. In this case, if the sintering temperature of the metal powder is set higher than the softening temperature of the glass, the glass penetrates into the gaps between the metal powders, and a glass permeation layer can be easily formed. On the other hand, in the case of firing the glass-penetrating layer after firing the base electrode, the silver is sintered at least partially, so the gap is smaller than the former, and the conditions for forming the glass-penetrating layer are The range becomes narrower. Furthermore, by firing these base electrode, glass layer, and glass permeation layer at the same time, the thermal history (thermal budget) imparted to the ceramic multilayer electronic component is reduced, resulting in problems such as fluctuations in characteristics and generation of strain due to heat. There is also an advantage that is reduced.

  According to the ceramic multilayer electronic component and the manufacturing method thereof of the present invention, since the element body is protected by the glass layer and the pores of the base electrode are filled by the glass permeation layer, the plating solution enters the element body. In addition, it is possible to sufficiently and effectively prevent the plating solution from remaining in the pores of the base electrode.

It is a schematic sectional drawing of the ceramic multilayer electronic component which concerns on this embodiment. It is sectional drawing which shows the manufacturing process of the ceramic multilayer electronic component which concerns on this embodiment. It is sectional drawing which shows the manufacturing process of the ceramic multilayer electronic component which concerns on this embodiment. It is sectional drawing which shows the manufacturing process of the ceramic multilayer electronic component which concerns on this embodiment. It is a figure which shows the relationship between a metal powder average particle diameter and the electrode coverage of a plating film. It is a figure which shows the relationship between a metal powder average particle diameter and an explosion failure incidence. It is a figure which shows the relationship between the glass frit amount and the electrode coverage of a plating film. It is a figure which shows the relationship between the amount of glass frit, and an explosion failure incidence.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Furthermore, the present invention can be variously modified without departing from the gist thereof.

  FIG. 1 is a cross-sectional view showing a schematic structure of a ceramic multilayer electronic component according to a first embodiment of the present invention.

  The ceramic multilayer electronic component 1 has a multilayer body 4 including an element body 2 made of ceramics and a plurality of internal electrodes 3 formed in the element body 2. More specifically, the internal electrode 3 having an end portion exposed from one side surface (end surface) of the element body 2 and the internal electrode 3 having an end portion exposed from the other side surface of the element body 2 include the element body. 2 are alternately stacked. Base electrodes 7 connected to the internal electrodes 3 are formed on both end faces of the element body 2. Further, a glass layer 6 a is formed on the exposed surface of the element body 2 other than the formation site of the base electrode 7, and a glass permeation layer 6 b formed by glass permeating the surface layer of the base electrode 7 is formed. .

  A terminal electrode 8 composed of a Ni layer 8a and a Sn layer 8b is further formed on the surface of the base electrode 7 by plating. These terminal electrodes 8 and, for example, electrodes on the wiring board are joined by solder or the like.

  Hereinafter, each component will be described.

  The element body 2 is made of ceramics, and specifically is made of semiconductor ceramics or dielectric ceramics. Such a ceramic material is not limited, and examples thereof include barium titanate, strontium titanate, boron nitride, ferrite, lead zirconate titanate, silicon carbide, silicon nitride, steatite, zinc oxide, and zirconia.

  A method for synthesizing the ceramic powder used for forming the element body 2 is not particularly limited, and for example, a hydrothermal method, a hydrolysis method, a coprecipitation method, a solid phase method, a sol-gel method, or the like is used. And may be calcined as necessary.

  For the internal electrode 3, for example, a material mainly composed of Ni, Cu, Pd, Ag, or Al is used in terms of enabling reliable ohmic contact with the element body 2. There is no limitation. The internal electrode 3 is formed, for example, by printing a conductive paste containing such a metal component.

  The base electrode 7 functions as a base layer for forming the terminal electrode 8 by electroplating. For example, the material of the base electrode 7 is not limited, but includes, for example, Ag, Cu, or Ni as a metal component. The base electrode 7 is obtained, for example, by applying and baking a conductive paste on the side surface of the multilayer body 4. Examples of the conductive paste for forming the base electrode 7 mainly include a glass powder (frit), an organic vehicle (binder), and a metal powder. By firing the conductive paste, the organic vehicle The base electrode 7 which volatilizes and finally contains a glass component and a metal component is formed. In addition, you may add various additives, such as a viscosity modifier, an inorganic binder, and an oxidizing agent, to an electrically conductive paste as needed.

  The glass layer 6a is formed in order to prevent erosion of the element body 2 made of ceramics and deposition of plating metal on the surface of the element body 2 in the plating of the Ni layer 8a and the Sn layer 8b. The material of the glass layer 6a is not limited, but preferably has good chemical resistance and a softening point lower than the sintering temperature of the element body. This makes it possible to set the firing temperature of the glass to be equal to or lower than the firing temperature of the element body, and to prevent fluctuations in element characteristics due to fluctuations in the element characteristics and diffusion of the metal constituting the internal electrode into the element body. It can be suppressed.

  The glass permeation layer 6b is a layer formed by filling the pores existing in the surface layer of the base electrode 7 that is a sintered body so that the glass permeates. The glass penetration layer 6b is formed at the same time as the glass layer 6a, and the ratio of glass is larger than the portion of the base electrode 7 other than the glass penetration layer 6b. In addition, the surface of the base electrode 7 is not covered by the presence of the glass permeation layer 6b, but the conductive surface of the base electrode 7 is exposed.

  The thickness of the glass layer 6a on the element body 2 is preferably 0.5 μm or more and 2 μm or less. If the thickness is 0.5 μm or more, the generation of pores in the glass layer 6a can be effectively suppressed, and the glass layer 6a having a uniform thickness tends to be easily formed. Further, when the thickness is 2 μm or more, the glass layer 6a becomes excessively thick and the glass does not easily penetrate into the inner surface (surface layer portion) of the surface of the base electrode 7. There is a tendency that a glass layer is also formed on the outside.

  The terminal electrode 8 is composed of a stacked body of a Ni layer 8a and a Sn layer 8b. The Ni layer 8a functions as a barrier metal that prevents the contact of the Sn layer 8b and the base electrode 7 and prevents the base electrode 7 from being corroded by Sn, and has a thickness of, for example, about 2 μm. Further, the Sn layer 8b has a function of improving the wettability of the solder, and the thickness thereof is, for example, about 4 μm. The Ni layer 8a and the Sn layer 8b are formed using a wet method such as electroplating or electroless plating. The material of the plating solution and the plating conditions are not limited, but the plating solution composition and the plating conditions that do not dissolve the glass layer 6a and the glass permeation layer 6b are appropriately selected.

  Next, a method for manufacturing the ceramic multilayer electronic component 1 according to the present embodiment will be described with reference to FIGS. 2 to 4 are process diagrams showing an example of a procedure for manufacturing the ceramic multilayer electronic component 1.

  First, as shown in FIG. 2, a laminated body 4 having a laminated structure of an element body 2 and internal electrodes 3 is formed. The laminated body 4 is manufactured as follows, for example. A ceramic powder, an organic solvent, an organic binder, a plasticizer, and the like are mixed to form a ceramic slurry, and then molded by a doctor blade method to obtain a sheet-like body, a so-called ceramic green sheet. Subsequently, a pattern of the internal electrode 3 is formed on the ceramic green sheet by printing a conductive paste containing metal powder, a binder resin, and a solvent. Further, subsequently, a plurality of element bodies 2 in which the internal electrodes 3 are formed and a plurality of element bodies 2 in which the internal electrodes 3 are not formed are alternately laminated, and further pressed to obtain a laminated structure. Then, the laminated structure is divided into individual laminated bodies 4 by cutting. Thereby, the edge part of the internal electrode 3 will be in the state exposed from the side surface of the laminated body 4 after a cutting | disconnection. Next, the laminate 4 is subjected to a binder removal treatment in the air and then fired to obtain a sintered laminate 4.

  Next, as shown in FIG. 3, the base electrode 7 a (before firing) is formed on the side surface of the element body 2. In the formation of the base electrode 7a, a conductive paste containing metal powder, an organic binder, glass frit, and a solvent is applied to the side surface of the element body 2 and dried. In this embodiment, the base electrode 7a is not yet fired at this stage. Further, the ratio of the glass frit to the total solid content remaining after firing, that is, the ratio of the glass frit to the total amount of the metal powder and the glass frit is preferably 0.5% by weight or more and 8% by weight or less. Further, the metal powder contained in the conductive paste preferably has an average particle size of 0.8 μm or more and 5 μm or less.

  Next, as shown in FIG. 4, a glass slurry containing glass powder, a binder resin and a solvent is applied to all exposed surfaces of the element body 2 and the base electrode 7a, followed by firing. By the firing at this time, the organic vehicle contained in the base electrode 7a is volatilized, and finally the base electrode 7 (after firing) including the glass component and the metal component is formed. Similarly, a dense and high-density glass layer 6 a is formed on the element body 2. Further, on the base electrode 7, the glass is softened before the metal powder is sintered in the firing process of the base electrode 7 a, and the glass is filled in the gap between the metal powders. A glass permeation layer 6 b is formed on the surface layer 7. For this purpose, the softening temperature of the glass is preferably lower than the sintering temperature of the metal powder.

  As the subsequent steps, as shown in FIG. 1, the Ni layer 8a and the Sn layer 8b are sequentially deposited on the surface of the base electrode 7 by electroplating to form the terminal electrode 8. For example, in the formation of the Ni layer 8a, a barrel plating method is adopted, and Ni of 2 μm is deposited using a Watt-based bath. Further, in the formation of the Sn layer 8b, a barrel plating method is adopted, and Sn is deposited by 4 μm using a neutral tin plating bath. Thus, the ceramic multilayer electronic component 1 is manufactured.

  According to the ceramic multilayer electronic component 1 having the above-described configuration and the manufacturing method thereof, since the exposed surface of the element body 2 other than the formation site of the base electrode 7 is covered with the glass layer 6a, the element body 2 is connected to the terminal electrode 8. Exposure to the plating solution for formation is prevented. Therefore, it is possible to form a good plating film on the base electrode 7 while avoiding problems such as erosion of the element body due to penetration of the plating solution into the element body and formation of a plating film on the element body. it can.

  In addition, since the glass permeation layer 6 b is formed on the inner surface of the base electrode 7, the pores existing on the inner surface of the base electrode 7 are filled while maintaining the conductivity of the surface of the base electrode 7. ing. As a result, the plating solution for forming the terminal electrode 8 is prevented from entering the pores of the base electrode 7. As a result, the plating solution that has entered the pores of the base electrode expands due to the heat during mounting and disperses the molten solder, causing short-circuit failure between wires (explosion failure) and entering the pores in a moisture resistance load test. Occurrence of defects such as short-circuit defects due to migration caused by the plating solution can be avoided.

  Furthermore, according to the manufacturing method of the ceramic multilayer electronic component 1 described above, since the glass layer 6a and the glass permeation layer 6b are formed simultaneously, the number of steps is not increased.

  Furthermore, by firing the base electrode 7a, the glass layer 6a, and the glass permeation layer 6b at the same time, the glass can be melted before the metal powder is sintered in the firing process, as compared with the case of firing separately. Thus, a glass permeation layer can be easily formed on the surface of the base electrode. Furthermore, by firing at the same time, the number of firing steps can be reduced, and defects such as distortion due to thermal history applied to the ceramic multilayer electronic component and fluctuations in characteristics can be reduced.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
A capacitor chip (chip of laminated body 4) having a main composition of element body 2 of strontium titanate, an internal electrode 3 of Ag, and an outer shape of 1.6 × 0.8 × 0.8 mm was produced. Then, an Ag paste having a frit amount of 5% and an average particle diameter of 3 μm was applied to the chip surface where the internal electrode 3 was exposed, and dried. Subsequently, an aqueous paint containing a glass powder having a softening point of 670 ° C. and an average particle diameter of 0.4 μm and a binder in an amount of 15% of the glass powder was sprayed by a Bares spray method to form a 2 μm glass slurry layer. . Thereafter, the chip was baked in the atmosphere at 710 ° C. to form a 1.3 μm glass layer 6 a on the surface of the element body 2, and a glass permeation layer 6 b was formed on the surface layer of the base electrode 7. A plating film can be continuously formed on the base electrode 7 of this chip by ordinary electroplating, and a 2 μm Ni layer 8 a and a 4 μm Sn layer 8 b were formed.

(Example 2)
In Example 1, the average particle diameter of the metal powder contained in the conductive paste for the base electrode 7 was changed, and the electrode coverage after plating was measured. The same conditions as in Example 1 were used except that the average particle size of the metal powder was changed. The results are shown in Table 1 and FIG. As shown in Table 1 and FIG. 5, when the average particle diameter of the metal powder was less than 0.8 μm, it was found that the coverage ratio was significantly reduced. This is because when the average particle size of the metal powder becomes small, the pore size generated in the base electrode 7 becomes too small, and the sintering temperature of the metal powder decreases as the particle size decreases, so that the glass is sufficiently melted and the viscosity is reduced. The tendency for the metal to sinter before it falls down, and thus the glass does not sufficiently penetrate the inside (surface layer portion) of the surface of the base electrode 7, and a glass layer is formed on the outer surface of the base electrode 7, It is presumed that it is difficult to form a plating film. However, the action is not limited to this.

  Further, Table 2 and FIG. 6 show the results of examining the occurrence rate of explosion failures after mounting. It has been found that when the average particle size of the metal powder exceeds 5 μm, explosion failure tends to occur. It can be considered that when the particle size of the metal powder is increased, the size of the pores generated in the base electrode 7 becomes excessively large, and the pores having such a large size cannot be filled with glass. As a result, it is presumed that the plating solution remains inside the pores during plating, and the plating solution expands and melts Sn due to the temperature rise during mounting. However, the action is not limited to this.

(Example 3)
Furthermore, the amount of glass frit contained in the conductive paste for the base electrode 7 in Example 1 was changed, and the electrode coverage after plating was measured. The results are shown in Table 3 and FIG. The glass frit amount (wt%) in Table 3 indicates the ratio of the glass frit to the total solid content remaining after firing, that is, the ratio of the glass frit to the total amount of metal powder and glass frit. It has been found that when the glass frit amount exceeds 8%, the coverage tends to decrease. This is because when the glass of the glass slurry layer melts, the glass frit contained in the conductive paste is also melted at the same time, and this partially fills the gaps in the metal powder, so the amount of glass frit contained in the conductive paste is small. It is thought that this is because the surface glass is inhibited from penetrating into the gaps of the metal powder when the number is increased.

  In addition, the occurrence rate of explosion defects after mounting was examined. The results are shown in Table 4 and FIG. It is understood that explosion defects tend to occur when the glass frit amount is less than 0.5%. This is presumed that when the amount of glass frit decreases, many pores are generated in the base electrode, and the pores are not easily filled with glass. As a result, it is presumed that the plating solution remains in the pores during plating, and the plating solution expands and melts Sn due to the temperature rise during mounting. However, the action is not limited to this.

  The present invention is not limited to the description of the above embodiments and examples. For example, in this embodiment, the base electrode 7a and the glass slurry layer are fired simultaneously, but may be fired separately. In addition, various changes can be made without departing from the scope of the present invention.

  The present invention includes a thermistor, a capacitor, an inductor, a LTCC (Low Temperature Co-fired Ceramics), a varistor, a ceramic multilayer electronic component composed of a composite part thereof, and a device, an apparatus, a system, a facility, and the like including the same, and It can be widely used for their production.

  DESCRIPTION OF SYMBOLS 1 ... Ceramic laminated electronic component, 2 ... Element body, 3 ... Internal electrode, 4 ... Laminated body, 6a ... Glass layer, 6b ... Glass penetration layer, 7a, 7 ... Base electrode, 8 ... Terminal electrode, 8a ... Ni layer, 8b ... Sn layer.

Claims (6)

An element made mainly of ceramics,
An internal electrode provided inside the element body and partially exposed on an end surface of the element body;
A base electrode formed on an end face of the element body;
A glass layer covering the exposed surface of the element body other than the formation site of the base electrode;
A glass permeation layer formed by glass permeating into pores present on the surface layer of the base electrode;
A terminal electrode formed by plating on the glass permeation layer;
Have
The glass penetration layer has a higher glass ratio than the portion other than the glass penetration layer in the base electrode.
Ceramic multilayer electronic components. The base electrode is formed by sintering a conductive paste containing metal powder having an average particle size of 0.8 μm or more and 5 μm or less.
The ceramic multilayer electronic component according to claim 1. The glass that penetrates into the pores existing in the surface layer of the base electrode to form a glass permeation layer is the same as the glass that forms the glass layer,
The ceramic multilayer electronic component according to claim 1 or 2 . The glass layer has a thickness of 0.5 μm or more and 2 μm or less.
The ceramic multilayer electronic component according to any one of claims 1 to 3 . Forming a laminated structure including an element body mainly made of ceramic and an internal electrode embedded in the element body and partially exposed at an end surface of the element body;
Applying a conductive paste to the end face of the element body to form a base electrode;
A glass layer is formed by applying glass slurry to the exposed surface of the element body and the surface of the base electrode other than the portion where the base electrode is formed, and a glass permeation layer is formed on the surface layer of the base electrode. Forming, and
Firing the base electrode, the glass layer, and the glass permeation layer simultaneously at a temperature higher than the softening temperature of the glass;
Forming a terminal electrode by plating on the glass permeation layer;
A method of manufacturing a ceramic multilayer electronic component having The conductive paste includes a metal powder, an organic binder, and a glass frit,
The content of the glass frit with respect to the total amount of the metal powder and the glass frit is 0.5 wt% or more and 8 wt% or less.
The method for producing a ceramic laminated electronic component according to claim 5 .

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