JPH11219849A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide reliable laminated ceramic capacitor with no possibility of defects in an outer electrode and cracks in a ceramic element, even if stress is caused by a drastic change in temperatures. SOLUTION: In a laminated ceramic capacitor, a ceramic element is formed by alternately laminating a dielectric ceramic layer 2 and inner electrodes 2 and 4, and outer electrodes 5 are formed at both end of the ceramic element. The outer electrode 5 is constituted of a first conductive layer 11, a second conductive layer 12 and a plurality of plated layers. A ceramic element 1 and the first conductive layer 11 are jointed with a jointing force F1 and the first and second conductive layers 11 and 12 are jointed with a jointing force F2 , where F1 <F2 , and F1 and F2 are both 1.0 kgf. An extended part 12a of the second conductive layer 12 is extended further than an extended part 11a of first conductive layer 11 by 0.05 mm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a capacitor ceramic body having, on an end portion thereof, a first conductor layer which is a baked conductor, a second conductor layer formed by curing a conductive resin, and a third conductor layer formed by plating. The present invention relates to a multilayer ceramic capacitor having external electrodes formed thereon.

[0002]

2. Description of the Related Art A conventional multilayer ceramic capacitor has a dielectric layer made of a dielectric ceramic material such as barium titanate and an internal layer made of a noble metal material such as silver or silver-palladium alloy or a base metal material such as nickel or copper. External electrodes are formed on opposing ends of a rectangular parallelepiped ceramic body in which electrode layers are stacked on each other, that is, on an end face and an outer peripheral face thereof. The internal electrode layers adjacent to each other in the laminating direction and arranged on the porcelain body were led out to different end faces of the porcelain body, and were connected to the external electrodes at the leading portions.

[0003] External electrodes formed at both ends of the porcelain body,
For example, Ag, Ag-Pd alloy, Cu,
A thick-film conductor layer formed by baking a conductive paste made of Ni, a surface of the thick-film conductor layer is covered, and a nickel plating layer made of a material that is unlikely to be eroded with solder, and a surface of the nickel plating layer 8 are covered. And an electrode layer made of tin (Sn) or solder (Sn-Pb alloy) (referred to as a thick-film conductor-plated external electrode).

Further, as an external electrode having another structure, for example, as shown in Japanese Patent Publication No. 58-40161, a thick film is formed by baking a conductive paste made of Ag or Ag-Pd alloy on the end of a porcelain body. A base conductor film was formed, and a second conductor layer was applied on the thick base conductor film by curing a resin-based conductive resin paste containing Ag powder (thick film conductor-resin curable type external). Electrodes). As a result, the adhesion strength between the ceramic body and the thick underlying conductor film has been increased, and the number of times parts can be replaced has been improved.

Further, as an external electrode having another structure, for example, as shown in Japanese Patent Application Laid-Open No. 4-257111, a thick base conductor film is formed at an end of a ceramic body, and the thick base conductor film is formed on the thick base conductor film. The epoxy / phenol-based thermosetting resin paste containing Ag powder was cured to form a buffer layer, and a plating layer was further applied to the buffer layer (thick conductor film).
Resin-plated external electrode).

[0006] Such a structure absorbs mechanical and thermal stress, particularly in the cushioning material layer.

[0007]

However, in a multilayer ceramic capacitor having a thick-film conductor-plated external electrode, the thick-film conductor film becomes a conductor serving as a main component of the external electrode, and has a sufficient thickness. For this reason, between the thick conductor film and the porcelain body, especially on the outer peripheral portion of the end of the porcelain body,
During baking of the thick conductor film, sintering shrinkage of the metal powder and diffusion of the glass component into the dielectric ceramic layer cause stress. When such a multilayer ceramic capacitor is bonded to a printed wiring board using solder and exposed to a severe environment with rapid thermal changes such as a temperature cycle test or thermal shock test, each of the external electrodes, solder, and printed wiring board However, there is a problem that the absorption of stress due to the difference in thermal expansion coefficient becomes insufficient, and cracks are generated in the ceramic body where the above-mentioned stress remains.

As a result, the multilayer ceramic capacitor does not function at all.

In a multilayer ceramic capacitor having a thick-film conductor-resin-cured external electrode or a thick-film conductor-resin-plated external electrode, when a stress acting outward from the ceramic body side is applied to the external electrode, Partial peeling is likely to occur in the conductive resin layer. When such a laminated ceramic capacitor in which the conductive resin layer has peeled off is solder-bonded to a printed wiring board, the laminated ceramic capacitor itself falls off the printed wiring board due to a decrease in the fixing force.

[0010] When a sudden thermal stress or an external stress exceeding the allowable amount is applied to the external electrode, destruction occurs in the external electrode.
Cracks may occur in the porcelain body. This is considered to be due to poor bonding strength between the porcelain body and the thick film underlying conductor layer, and poor bonding strength between the thick film underlying conductor layer and the conductive resin layer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide a highly reliable semiconductor device in which defects in external electrodes are less likely to be multiplied even when stress is generated due to an extreme change in temperature environment. An object of the present invention is to provide a multilayer ceramic capacitor. Another object of the present invention is to provide a highly reliable multilayer ceramic capacitor in which cracks do not occur in a ceramic body.

[0012]

SUMMARY OF THE INVENTION The present invention provides a porcelain body formed by alternately laminating dielectric layers and internal electrode layers.
In a multilayer ceramic capacitor having an external electrode formed from a first conductor layer containing a glass component, a second conductor layer containing a resin component, and a third conductor layer made of a plated metal from the side of the porcelain body, F ₁ the bonding strength between the first conductive layer, when the bonding strength F ₂ with the first conductor layer and the second conductive layer, F _1, F ₂ is, F ₁ ≧ 1.0 kgf, F ₂ ≧ 1.
0 kgf, F ₁ > F ₂ is satisfied.

[0013] Further, a part of an external electrode formed of a first conductor layer, a second conductor layer, and a third conductor layer formed on both end surfaces of the porcelain body extends to a lower surface of the porcelain body, And the second
The extension length of the conductor layer is more than the extension length of the first conductor layer by 0.
It is longer than 05 mm.

[0014]

According to the present invention, the end face of the porcelain body and the first electrode of the external electrode are provided.
It is obtained by identifying the first second of the relationship between the bonding strength F ₂ at the bonding interface between the bonding strength F ₁ and the first conductor layer and the second conductive layer of the junction interface between the conductor layer.

The bonding strength F ₁ of the first bonding interface between the end surface of the ceramic body and the first conductive layer of the external electrode is determined by the composition of the glass component of the conductive paste used when forming the first conductive layer. Can be controlled. Further, the bonding strength F ₂ at the second bonding interface between the first conductor layer and the second conductor layer is the second bonding strength.
It can be controlled by the weight ratio of the conductive resin paste forming the conductor layer, for example, an epoxy-based thermosetting resin.

For example, when the external electrode is pulled in the longitudinal direction of the porcelain body, a 1608 type (size: length × width × thickness =
1.6 × 0.8 × 0.8 mm), the bonding strength F ₁ of the first bonding interface between the ceramic body and the first conductor layer is 2.0 k.
gf or more, the bonding strength F ₂ of the adhesive of the second bonding interface between the first conductive layer and the second conductive layer is made to be 1.5～2.0Kgf. In addition, 2012 type (size: 2.0 × 1.2
5 × 0.6 to 1.25 mm), the bonding strength F ₁ is 2.5
kgf or higher, bonding strength F ₂ is made to be 1.5～2.5Kgf. 3216 type (size: 3.2 x 1.6 x
0.6～1.6Mm) in the bonding strength F ₁ is 3.0kgf
Above, the bonding strength F ₂ is made to be 1.5～3.0Kgf.

The external electrode in which the Ni plating layer and the Sn plating layer are adhered on the two conductor layers combined with the bonding strengths F ₁ and F ₂ has the tensile fixing strength of the first conductor. It will be rate-limiting in bonding strength F ₂ layer and the second conductive layers. In this case, the bonding strength F _2, since it is practical requirements bonding strength at a 1kgf above, even soldered multilayer ceramic capacitor on a printed wiring board, sufficient bonding strength can be achieved.

Further, when the first conductor layer and the second conductor layer are separated by an external force exceeding an allowable level, the first conductor layer and the second conductor layer are separated from each other. No breakage such as cracks occurs in the elementary porcelain.

In the outer peripheral portion of the end of the porcelain body,
The second conductor layer completely covers the first conductor layer, and further comprises the first conductor layer.
It extends 0.05 mm or more from the tip of the conductor layer and is directly attached to at least the lower surface of the porcelain body.

Thus, when excessive stress is applied to the external electrode from the outside, the stress concentrated between the external electrode and the porcelain body can be absorbed by the second conductor layer.
It is possible to effectively prevent damage such as cracks generated on the outer periphery of the end of the porcelain body.

In particular, when the second conductor layer extends 0.05 mm or more from the tip of the first conductor layer, the effect is high. Conversely, when the second conductor layer is less than 0.05 mm, the conventional thick film conductor-plating type is used. As described above, breakage such as cracks generated on the outer periphery of the end of the porcelain body becomes remarkable.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer ceramic capacitor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an external perspective view of a multilayer ceramic capacitor according to the present invention, and FIG. 2 is a structure showing a vertical section.

Referring to FIG.
Numeral 0 denotes a ceramic body 1 formed by alternately laminating dielectric layers 2 made of a dielectric ceramic material such as barium titanate and internal electrodes 3 and 4, and external members formed at both ends of the ceramic body 1. And electrodes 5 and 5.

The internal electrodes 3 and 4 are made of Pd or Ag-Pd
It is made of a noble metal material such as an alloy or a base metal material such as nickel (Ni). One end of the internal electrode 3 extends to one end surface of the ceramic body 1 and is connected to one external electrode 5. The other end of the internal electrode 4 extends to the other end surface of the ceramic body 1 and is connected to the other external electrode 5.

The external electrodes 5, 5 are formed on both ends of the porcelain body, that is, on the end face and the outer peripheral surface around the end face, and are formed by baking a conductive paste made of Ag or an Ag alloy or the like from the porcelain body side. The first conductor layer 11, the second conductor layer 12 formed on the surface of the first conductor layer by curing a conductive resin obtained by mixing Ag powder with an epoxy-based thermosetting resin, and the surface of the second conductor layer 12. Third conductor layer 13 formed by plating with a material such as nickel which is unlikely to cause solder erosion.
To adhere. If necessary, a tin or solder plating layer made of a material such as tin (Sn) or solder (Sn—Pb alloy) is formed on the third conductor layer 13.

Here, the second conductor layer 12 is formed of the first conductor layer 1
1 so as to completely cover the outer peripheral portion around the end face as well as the end face portion of the porcelain body 1.
That is, it extends and is attached to the upper surface, the lower surface, and the ends of both side surfaces of the porcelain body. Moreover, the length of the extending portion 12a of the second conductor layer 12 is 0.05 mm or more longer than the length of the extending portion 11a of the first conductor layer 11. This difference in the extension length is described as Δx as the extension displacement amount.

Next, a method of manufacturing the multilayer ceramic capacitor having the above structure will be described.

First, a ceramic green sheet serving as the dielectric layer 2 and having a shape capable of extracting a plurality of elements is formed by well-known tape molding. Next, an internal electrode 3 is provided in each element region.
Alternatively, a conductor film to be 4 is formed by printing and drying using a paste of metal powder. This conductive film is arranged so that a large number of rectangles are regularly arranged on the ceramic green sheet.

Next, the ceramic green sheets printed in this manner are laminated in a number corresponding to the number of laminated ceramic bodies,
Thermocompression bonding is performed, and each element is cut into a predetermined shape to obtain a laminated chip body. At this time, the conductor films to be the internal electrodes 3 and 4 are exposed from a pair of end surfaces of the laminated chip body.

Next, the cut laminated chip body is fired in a predetermined atmosphere and temperature to form the porcelain body 1.

Next, external electrodes 5 are provided at both ends of the porcelain body 1.
5 is formed. First, the first conductor layers 11 of the external electrodes 5 and 5
Means that both ends of the porcelain body 1 are made of Ag or Ag alloy, Cu
After being immersed in a conductive paste made of a base metal or the like and dried to form a coating film, the coating film is formed by baking in a predetermined atmosphere and temperature. The thickness of the fired first conductor layer 11 is, for example, 20 to 30 μm. Specifically, the type 1608 is 20 μm, the type 2012 is 30 μm, and the type 3216 is 30 μm. Here, the first
Since the conductor layer 11 is formed by immersion, the first conductor film is formed not only on the end face of the porcelain body 1 but also on the outer peripheral portion around the end face corresponding to the amount immersed from the end face.

Thereafter, a second conductive layer 12 made of a conductive epoxy-based thermosetting resin is formed on the surface of the first conductive layer 11. Specifically, the end of the porcelain body 1 on which the first conductor layer 11 is adhered is formed on a conductive resin paste obtained by mixing a metal powder made of Ag or an Ag alloy with an epoxy-based thermosetting resin. After immersion and drying, the applied film is
It is formed by curing at 250 ° C. The thickness of the cured second conductor layer 12 is, for example, 25 to 70 μm. Specifically, type 1608 is 25 μm, type 2012 is 60 μm,
Type 216 is 70 μm. Here, if the second conductor layer 12 is formed by immersion, the second conductor film 12 is also formed on the outer peripheral portion around the end face of the porcelain body 1 corresponding to the amount immersed from the end face of the porcelain body 1. Can be. That is, in the outer peripheral portion of the end surface, the second conductor layer is formed to extend from the tip portion of the first conductor layer 11 by 0.05 mm or more as the amount of extension displacement Δx, so that the second conductor layer is formed by immersion of the resin paste. In doing so, the immersion amount is further compared with the immersion amount immersed in the conductive paste to form the first conductor layer,
What is necessary is just to immerse 5 mm or more deeply.

As described above, the second conductor layer 12 is formed not only by dipping, drying, and curing the resin paste, but also by
For example, it may be formed by printing, drying, and curing a resin paste at a predetermined position.

Next, on the second conductor layer 12, the external electrodes 5,
In order to prevent solder erosion of No. 5, a third conductor layer such as nickel plating is formed. Further, in order to facilitate solder adhesion to the external electrodes 5, 5, for example, tin (S
n) or a tin or solder plating layer made of a material such as solder (Sn—Pb alloy). Such plating can be formed by electrolytic plating or the like.

Thus, the multilayer ceramic capacitor shown in FIG. 1 is completed.

In forming the external electrodes 4 and 5, both ends of the laminated body 1 are immersed in a conductive paste or a conductive resin paste as described above. The first conductor layer 11 and the second conductor layer 12 respectively extend in the portion. For example, in consideration of solder bonding to a printed wiring board, the external electrodes 4 and 4 are provided only on the lower surface side of the end of the ceramic body 1. 5 may be formed.

The conductive paste used to form the first conductor layer 11 may be a metal powder such as Ag or an Ag alloy, a low melting glass frit, a dispersing material, a binder, a mixed composition with a solvent, or a mixture thereof. It is composed of a mixed composition containing a ceramic powder such as alumina or silica. 5-20% by weight of glass frit to metal powder
It is important that The bonding strength F ₁ between the porcelain body and the first conductor layer 11 depends on the amount of the glass frit added.
This is because it is possible to control By adding the glass frit in the above-mentioned quantitative ratio, the area of the end face of the porcelain body is small, for example, 1608 type (end face area: 0.8 × 0.8 m).
Even m), bonding strength F ₁ a can be at least 2 kgf, can be more than 1kg tensile strength of the external electrodes 5, 5 are level with no problem in use.

If the ratio of the above glass frit is less than 5% by weight, the strength F ₁ of the porcelain body 1 and the first conductor layer 11 decreases, and even if the bonding strength F ₁ can be set to 1 kgf or more, Joint strength F ₂ between first conductor layer 11 and second conductor layer 12
It is difficult to make it larger.

The ratio of the above glass frit is 20% by weight.
When the ratio exceeds 1, the strength F ₁ between the porcelain body 1 and the first conductor layer 11 increases, but on the contrary, a glass component is deposited on the surface of the first conductor layer 11, and electrical conduction with the second conductor layer 12 occurs. And the bonding strength is degraded.

The above metal powder is composed of Ag, Pd, Cu, N
i and their alloys are used, and the glass frit is
A mixture of borosilicates such as Zn, Pb and Bi is used, and a hydrocarbon-based, acrylic-based, alkyd-based, amino-based polyester or rosin derivative is used as a binder, and a hydrocarbon-based or alcohol-based solvent is used. , Ethers, ketones, aliphatics, and the like.

The conductive resin paste for forming the second conductive layer 12 is formed by a mixed composition of a mixed composition of a metal powder, a thermosetting epoxy resin, and a curing agent and an organic medium.

The bonding strength to the first conductor layer can be controlled by the molecular weight of the thermosetting epoxy resin or the weight ratio of the metal powder to the thermosetting epoxy resin.

The molecular weight of the thermosetting epoxy resin is desirably relatively low, for example, desirably 1,000 or less.

The weight ratio of the thermosetting resin composition to the metal powder is desirably about 10 to 40% by weight.

By using the epoxy resin having a relatively low molecular weight in the above range, even if the porcelain body is of type 1608 (end surface area: 0.8 × 0.8 mm) having a small end surface area, it can be used for external purposes. It is possible to achieve a tensile strength of the electrode of 1 kgf or more, which is a level having no problem in use. Moreover, the bonding strength F ₂ with the second conductive layer 12 formed by the conductive resin paste and the first conductive layer 11, easily controlled below the bonding strength F ₁ between the porcelain body 1 and the first conductive layer 11 can do.

When the thermosetting epoxy resin has a very low molecular weight, for example, when the molecular weight is 300 or less, the reactivity becomes excessive, and it is difficult to reduce the bonding strength F ₂ to less than the bonding strength F ₁ . When the molecular weight is high, for example, 1
Exceeds 200, the bonding strength F ₂ itself can not be obtained.

In the weight ratio between the epoxy resin and the metal powder, the larger the resin ratio, the higher the fixing strength.
If the ratio of the epoxy resin to the metal powder exceeds 40% by weight, the resin is unevenly distributed on the surface of the cured second conductor layer 12, and it becomes impossible to cover the third conductor layer 13 with the plating layer. Would.

If the proportion of the epoxy resin is less than 10% by weight, it is difficult to make the bonding strength F ₂ between the first conductor layer 11 and the second conductor layer 12 equal to or more than 1.0 kgf.

The metal powder is made of gold, silver, platinum, palladium, rhodium, nickel or copper alone or an alloy thereof.

The epoxy resin comprises a compound having two or more epoxy groups in a molecule, and is cured by the action of a curing agent or a catalyst. The epoxy resin is selected from a liquid epoxy resin such as a bisphenol A epoxy resin, a bisphenol F epoxy resin, and a bisphenol AD epoxy resin.

As the curing agent, a polyamid curing agent, an aliphatic polyamine curing agent, a cycloaliphatic polyamine curing agent, an aromatic polyamine curing agent, dicyandiamide and the like are used. Examples of the organic medium include various aliphatic alcohols and esters thereof, carbitol solvents, ketone solvents, and hydrocarbon solvents.

As described above, the second conductive layer 12 is formed by coating a conductive resin paste by screen printing, immersion, or the like, and temporarily dried at a temperature of 80 to 140 ° C.
Thereafter, in order to completely remove the solvent component in the conductive resin paste, the solvent is removed in a temperature atmosphere of 60 to 120 ° C for 15 to 90 minutes, and then heated at a temperature of 150 to 250 ° C for 30 to 120 minutes. By doing so, it is cured and formed.

As described above, according to the multilayer ceramic capacitor of the present invention, the connection strength F ₁ between the ceramic body 2 and the first conductor layer 11 and the connection strength between the first conductor layer 11 and the second conductor layer 12 are determined. By controlling the relationship with the intensity F ₂ as described above,
Each connection should be 1.0 kgf or more, and both joint strengths F
The relationship between ₁ and F ₂ was set so that F ₁ > F ₂ .

As a result, the porcelain body 1 can be removed even when a normal external stress is applied to separate the external electrodes 5 and 5.
No separation occurs at the bonding interface between the first conductive layer 11 and the first conductive layer 11 and at the bonding interface between the first conductive layer 11 and the second conductive layer 12. Moreover,
Even when subjected to sudden thermal changes or excessive external force,
Since the conductive epoxy thermosetting resin layer serving as the conductive layer 12 absorbs the sudden impact, the ceramic body 1 does not crack or break.

If an external force exceeding the permissible impact is applied, no crack occurs in the dielectric ceramic layer 2 of the ceramic body 1, and the difference between the bonding strengths F ₁ and F ₂ causes the external electrodes 5 and 5 only causes peeling at the interface between the first conductor layer 11 and the second conductor layer 12 and causes the most fatal electrical short-circuit failure between the internal electrodes 3 and 4 where cracks occur in the capacitor ceramic body. Can be avoided.

Further, at the same time, the second conductor layer 12 is provided on the outer peripheral portions at both ends of the porcelain body 1, that is, on both main surfaces and both side surfaces of both ends of the porcelain body 1. The coating is extended toward the center from the edge of No. 11 as the extension displacement amount Δx by 0.05 mm or more. The extension of the first conductor layer is indicated by reference numeral 11a, and the extension of the second conductor layer 12 is indicated by reference numeral 12a.

Therefore, as described above, the external electrodes 5, 5
Even if stress such as impact is applied from outside to the first conductor layer 11
Before the stress is applied to the second conductor layer 12, the entire second conductor layer 12 absorbs the stress. The extending portion 1 of the first and second conductor layers 11 and 12
1a and 12a, the stress applied to the surface of the porcelain body 1 from the extending portion 11a of the first conductor
Before being applied to the extension 11a of the conductor layer 11, the absorption is performed by the extension 12a of the second conductor layer 12.

Therefore, the occurrence of cracks in the porcelain can be effectively suppressed at the joint between the extending portions 11a and 12a of the first and second conductor layers 11 and 12 and the porcelain body 1.

On the other hand, the extending portion 1 of the second conductor layer 12
2a does not extend closer to the center than the extending portion 11a of the first conductor layer 11, or even if it extends, it is 0.0.
If it is less than 5 mm, stress concentrates at the joint interface between the extending portion 11a of the first conductor layer 11 and the porcelain body 1, and as a result, cracks or the like occur in the porcelain.

[0061]

(Example 1) 2012 type of the present invention (2.0 × 1.
Using a ceramic body 1 of a multilayer ceramic capacitor (25 × 0.85 mm), a thickness of 3
The first conductor layer 11 having a thickness of 0 μm was formed. The conductive paste for forming the first conductor layer 11 has Ag as a main component, uses two types of zinc borosilicate-based and lead borosilicate-based glass frit, and adjusts the amount of glass frit added to Ag powder by weight. Was changed in the range of 5 to 20%. The paste viscosity was adjusted in advance with the amount of the solvent so as not to have a different coating shape. The silver powder was adjusted by changing the mixing ratio of the fine powder type and the flake-like coarse particle type so as not to cause electrode cracking during baking.

After forming only the first conductor layer 11, nickel and tin plating are applied so that the bonding strength between the porcelain body and the first conductor layer can be measured, and the lead wire is perpendicular to the center of the end face. And soldered to it using a load cell tester.
A tensile strength test was performed. At that time, 50 samples were examined.

As a result, the bonding strength F ₁ between the ceramic body 1 and the first conductor layer 11 was as shown in the characteristic diagram of FIG. The vertical axis represents the strength, and the horizontal axis represents the glass weight ratio when the metal component is 100.

As the amount of glass frit added to Ag increases, the fixing strength increases. In addition, as the amount of glass frit increases, the phenomenon that glass oozes out on the surface of the baked electrode increases, and when the amount of glass frit exceeds 20% by weight, a rotary barrel is then placed in a pot containing alumina polishing powder and water. However, the surface floating glass layer could not be removed cleanly. This surface glass layer reduces not only the electrical conductivity but also the bonding strength to the subsequent thermosetting resin.

(Example 2) The second conductor layer 12 was formed on the first conductor layer 11 by using a thermosetting type on the first conductor layer 11 using the sample of the multilayer ceramic capacitor prepared in the above-described example 1 on which the first conductor layer 11 was formed. A conductive paste was formed, and the bonding strength between the first conductor layer 11 and the second conductor layer was measured. The first conductor layer 11
A conductive resin paste in which an Ag-based conductive powder is dispersed in an epoxy-based resin is applied on the baked Ag conductive film in a thickness of 60 μm so as to completely cover the first conductive layer 11, and is further dried. Desolvation at a temperature of 120 ° C,
Then, it was cured at a temperature of 150 to 200 ° C., thereby forming a second conductor layer 12 made of an epoxy-based thermosetting resin. Then, the nickel plating layer 13 was formed by electrolytic plating, and a tin-based layer was formed on the nickel plating layer 13 by electrolytic plating. In producing such a laminated ceramic capacitor, the measurement was performed by changing the resin solid content ratio to the metal component 100 of the conductive resin paste by 10 to 40% by weight.

As a result, the first conductor layer 11 and the second conductor layer 1
Bonding strength F ₂ between 2 Results shown in the characteristic diagram of FIG.

As a result, as shown in FIG.
₂ , the abscissa of both the lines a and b in the characteristic diagram of FIG. 4 indicates the weight ratio of the glass frit to the solid component.

When the weight ratio of the epoxy resin exceeds 40% by weight, a resin component is deposited on the surface of the second conductor layer 12, and the nickel plating layer 13 cannot be formed stably.

The temperature cycle durability test was -5.
Hold at 5 ° C. atmosphere for 30 minutes, and hold at 150 ° C. atmosphere for 30 minutes, with a cooling / heating cycle of 10 minutes.
The test was performed 00 times and the state of reduction in capacity was examined. At that time, the occurrence frequency of cracks in the porcelain body and the peeling of the external electrodes were measured for 50 samples.

As a result of the temperature cycle test, the sample having a solid content ratio of 10 to 40 wt% with respect to the silver powder had a high initial fixing strength, and hardly decreased even in the temperature cycle durability test. In addition, no cracks occurred in the capacitor body, and the external electrodes were peeled off.

(Example 3) It is important that the relationship between the _two bonding strengths F ₁ and F ₂ shown in FIGS. 3 and 4 be F ₁ > F ₂ . Therefore, for example, the glass weight ratio of the conductive paste forming the first conductive layer 11 is 10% by weight, and the resin weight ratio of the conductive resin paste forming the second conductive layer 12 is 2%.
Above 0% by weight, F ₁ >
There is a case in which not a F _2. Therefore, each joint strength F
₁ , F ₂ must be measured and controlled so that F ₁ > F ₂ is satisfied.

Therefore, the present inventors have proposed a 1608 type, 20 type
The glass weight ratio of the conductive paste of the first conductive layer 11 constituting the external electrodes of the 12-type and 3216-type multilayer ceramic capacitors was set to 10% by weight, and the epoxy resin of the conductive resin paste of the second conductive layer 13 was used. It was set to 20% by weight. Then, the joining strength F ₁ between the porcelain body 1 and the first conductor layer 11 and the joining strength F between the first conductor layer 11 and the second conductor layer 12
₂ was synthesized in FIG.

Incidentally, the first conductor layer 11 according to the type of the sample,
The thickness of the second conductor layer 12 was set to the value shown in the above specific example. In FIG. 5, the horizontal axis indicates each type, and the vertical axis indicates the bonding strength.

[0074] As can be understood from FIG. 5, in this combination, even if variations occur in each of the bonding strength F _1, F _2, as more 1.0kgf respectively bonding strength F _1, F _2, moreover, F ₁ > and has a F _2.

In this example, the glass weight ratio of the first conductor layer 11 is 10% by weight. However, considering the result of FIG. 3, the weight ratio of the epoxy resin of the second conductor layer 12 is not changed. It can be seen that there is no problem even if the glass weight ratio is set to 10% by weight or more.

(Example 4) In the multilayer ceramic capacitor sample of (Example 2), the second conductor layer 1
2 completely covers the surface of the first conductor layer 11, and furthermore, the extension portion 11 of the first conductor layer 11 is formed on the outer peripheral surface of the end of the ceramic body 1.
Samples were prepared in which the distance Δx extending from the tip of “a” was variously changed.

Then, the above-mentioned temperature cycle durability test was performed, and the observation of internal cracks generated inside the porcelain body 1 was also used.

As a result, the second conductor layer 12 extends beyond the extension of the first conductor layer 11 extending to the outer peripheral portion of the end of the ceramic body 1.
When the extending portion 12a extends to at least 0.05 mm toward the center of the porcelain body, good results were obtained in both the adhesion strength test and the temperature cycle durability test. On the other hand, when the extension displacement amount Δx in which the extension 12a of the second conductor layer 12 further extends from the extension 11a of the first conductor layer 11 is less than 0.05 mm, occurrence of cracks is observed. Was done.

This was verified in a test only by applying a mechanical stress to the sample by forcibly bending the printed circuit board after soldering the sample to the printed circuit board.
For example, as shown in FIG. 6, in the accelerated bending test in which the beam is bent 10 mm in a span of 90 mm, as shown in FIG.
If it is 5 mm or more, cracks do not occur in all the samples.

According to the above results, the extending portion 12a of the second conductor layer 12 is located at least at a position closer to the center of the porcelain body than the extending portion 11a of the first conductor layer 11 on the outer peripheral portion of the end of the porcelain body 1. .
It has been found that it must be extended by at least 05 mm.

In the above-described experimental example, an experiment was performed using a 2012-type porcelain body. However, the end face area was a relatively small 1608 type, and the end face area was a relatively large 3216 type. Similar results were obtained.

[0082]

As described above, according to the present invention, even if stress is generated by a temperature cycle or thermal shock after mounting on a circuit board, cracks do not occur in the porcelain body. The external electrodes are not peeled off, and the bonding strength with the mounting substrate is excellent. As a result, a multilayer ceramic capacitor having high quality and long-term reliability is obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor of the present invention.

FIG. 3 is a characteristic diagram showing a joining strength between a ceramic body and a first conductor layer and a joining strength between a first conductor layer and a second conductor layer of the multilayer ceramic capacitor of the present invention.

FIG. 4 is a characteristic diagram showing a bonding strength between a first conductor layer and a second conductor layer of the multilayer ceramic capacitor of the present invention.

FIG. 5 is a characteristic diagram showing the joining strength between the ceramic body and the first conductor layer and the joining strength between the first conductor layer and the second conductor layer of the multilayer ceramic capacitor of different shapes according to the present invention.

FIG. 6 is a characteristic diagram showing a crack generation rate depending on a second conductor layer extension distance Δx on a porcelain body surface of the multilayer ceramic capacitor of the present invention.

[Explanation of symbols]

 Reference Signs List 10 multilayer ceramic capacitor 1 ceramic body 2 dielectric ceramic layer 3, 4 internal electrode 5, 5 external electrode 11 first conductor layer 12 Second conductor layer

Claims (2)

[Claims] 1. A first conductor layer containing a glass component and a second conductor containing a resin component on both end surfaces of a porcelain body formed by alternately laminating dielectric layers and internal electrode layers from the porcelain body side. A multilayer ceramic capacitor having an external electrode formed of a third conductor layer made of a plated metal and a third conductor layer, wherein the bonding strength between the porcelain body and the first conductor layer is F ₁ , and the first conductor layer and the second conductor layer are when the bonding strength F _2, F _1, F
_2. A multilayer ceramic capacitor, wherein ₂ satisfies the following conditions. F ₁ ≧ 1.0 kgf, F ₂ ≧ 1.0 kgf, F ₁ > F ₂ 2. A part of an external electrode formed of a first conductor layer, a second conductor layer, and a third conductor layer formed on both end surfaces of the porcelain body, extends on a lower surface of the porcelain body, And the extension length of the second conductor layer is 0.05 times greater than the extension length of the first conductor layer.
2. The multilayer ceramic capacitor according to claim 1, wherein the length is at least mm.