JP2003318059A - Multilayer ceramic capacitors - Google Patents

Abstract

(57) [Problem] To provide a high-quality and high-reliability multilayer ceramic capacitor in which a crack does not occur in a laminated body even when conditions of a temperature cycle and a thermal shock become severe. SOLUTION: A laminated body 1 is formed by alternately laminating dielectric layers 2 having internal electrode layers 3, 4 mainly composed of Ni or Cu, and internal electrode layers 3, 4 on both end surfaces of the laminated body 1. In the multilayer ceramic capacitor 10 formed with the external electrodes 5 and 6 to be connected, the external electrodes 5 and 6 are formed from the inside of the multilayer body 1 with the base conductor films 5 a and 6 a containing at least an alloy of Cu and Ni and a glass component. And conductive resin layers 5b and 6b containing at least one of Cu, Ni and Ag
And plating layers 5c to 5d and 6c to 6d are sequentially laminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic capacitor, and more particularly to the structure of external electrodes.

[0002]

2. Description of the Related Art Conventionally, a laminated ceramic capacitor is formed on both end faces of a laminated body in which a plurality of dielectric layers such as barium titanate and a plurality of internal electrode layers are alternately laminated. Each internal electrode layer, which is composed of a pair of external electrodes and is adjacent to each other in the stacking direction, is connected to different external electrodes. The external electrode contains Cu and a glass component and is formed by baking on both end faces of the laminated body, and a Ni plating layer, Sn or Sn-Pb formed on the surface of the underlying conductor film. It consists of a plating layer and the like.

However, in the above-mentioned laminated ceramic capacitor, since the base conductor film of the external electrode is formed by baking, the sintering contraction of the Cu powder at the joint between the base conductor film and the laminated body, especially at the peripheral portion of the base conductor film. Since stress is generated by the diffusion of the glass component into the dielectric layer and the dielectric layer, when a temperature cycle test or a thermal shock test is performed on the one mounted with the laminated ceramic capacitor on the circuit board by soldering, the dielectric layer, the external Due to the difference in thermal expansion coefficient between the electrodes, the solder, and the circuit board, stress absorption becomes insufficient, and cracks occur in the laminated body from the peripheral portions of the external electrodes, and as a result, the laminated ceramic capacitor fails to function.

Therefore, as an external electrode, from the inside of the laminate, a base conductor film containing a simple substance of Cu and a glass component,
A monolithic ceramic capacitor in which a conductive resin layer containing at least one of Cu, Ni and Ag and a Ni plating layer and a Sn or Sn-Pb plating layer are sequentially laminated is disclosed in Japanese Patent Laid-Open No. 6-29144. Kaihei 8-107039
It is disclosed in the publication.

Even when the monolithic ceramic capacitor is mounted on the circuit board by soldering and then subjected to a temperature cycle or thermal shock, the conductive resin layer can absorb the stress.
It was possible to prevent the occurrence of cracks in the laminate.

[0006]

However, according to the above-mentioned multilayer ceramic capacitor, when the base conductor film is baked, the wettability between the simple substance of Cu and the glass component is insufficient, and the distribution of Cu and glass is uneven. It was.
For this reason, the stress at the time of baking the underlying conductor film partially differs, and cracks may occur when the conditions of the temperature cycle test and the thermal shock test become strict.

The present invention has been devised in view of the above problems, and an object thereof is high quality and high reliability in which cracks do not occur in a laminated body even when the conditions of temperature cycle and thermal shock become severe. To provide a monolithic ceramic capacitor having excellent properties.

[0008]

A monolithic ceramic capacitor of the present invention comprises a laminated body formed by alternately laminating dielectric layers having internal electrode layers containing Ni or Cu as a main component, and both end faces of the laminated body. In a monolithic ceramic capacitor formed by forming an external electrode connected to the internal electrode layer, the external electrode includes a base conductor film containing at least an alloy of Cu and Ni and a glass component from the inside of the laminate, and Cu, N.
It is characterized in that a conductive resin layer containing at least one of i and Ag and a plating layer are sequentially laminated.

Preferably, the base conductor film is made of Cu and N.
The weight ratio with i is in the range of 95: 5 to 25:75.

According to the present invention, Cu and Ni are formed on both end faces of the laminate.
Even if the base conductor film made of the alloy and the glass component is formed, the wettability between the metal component and the glass component becomes better than when Cu alone is used. Therefore, the distribution of the metal component and the glass component in the underlying conductor film becomes uniform, and the stress generated during baking becomes uniform in the entire underlying conductor film. Therefore, after soldering on the circuit board, even if a temperature cycle test or a thermal shock test is performed, cracks may occur in the laminate,
It is possible to provide a monolithic ceramic capacitor having high quality and long-term reliability, since the external electrodes are not peeled off and the adhesion strength to the circuit board is excellent.

By setting the weight ratio of Cu to Ni of the base conductor film in the range of 95: 5 to 25:75, the wettability between the metal component and the glass component becomes particularly good during baking, and the lamination is achieved. The bonding strength between the ceramic capacitor and the circuit board can be further increased.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A laminated ceramic capacitor of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view of the monolithic ceramic capacitor of the present invention. FIG. 2 is a sectional view of the monolithic ceramic capacitor of FIG.

In the figure, 10 is a monolithic ceramic capacitor, 1 is a laminated body, 2 is a dielectric layer, 3 and 4 are internal electrode layers, and 5 and 6 are external electrodes.

The dielectric layer 2 is made of barium titanate (BaT).
It is made of a non-reducing dielectric material containing iO ₃ ) or the like as its main component, and its thickness is set to 5 to 10 μm for high capacity. This dielectric layer 2 has a shape of 2.0 mm × 1.2
mm or the like, and the laminated body 1 is configured by laminating in the upward direction in the drawing. The shape, thickness, and number of stacked layers of the dielectric layer 2 can be arbitrarily changed depending on the capacitance value.

The internal electrode layers 3 and 4 are made of a material whose main component is Ni or Cu, which is a single metal component, and the thickness thereof is 0.5 to 2 μm. The two internal electrode layers 3 and 4 that are adjacent to each other in the stacking direction of the dielectric layer 2 are
They extend to different end face sides of the laminated body 1 and are connected to different external electrodes 5 and 6, respectively.

The external electrodes 5 and 6 are, from the laminated body 1 side, respectively, underlying conductor films 5a and 6a, conductive resin layers 5b and 6b, and
The Ni plating layers 5c and 6c and the plating layers 5d and 6d such as Sn or Sn-Pb are sequentially laminated.

The underlying conductor films 5a and 6a are formed by applying and baking a conductive paste containing a metal component having a weight ratio of Cu and Ni in the range of 95: 5 to 25:75 and borosilicate glass such as zinc borosilicate. It is formed.

The conductive resin layers 5b and 6b are made of a thermosetting resin such as an epoxy resin, a phenol resin or an acrylic resin, and conductive powder such as Cu, Ni or Ag contained therein.

On the conductive resin layers 5b and 6b, Ni plating layers 5c and 6c made of a material in which solder erosion is unlikely to occur are formed, and tin (Sn) or solder (Sn-Pb) is further formed.
Plated layers of tin or solder (hereinafter abbreviated as tin-based layers) 5d and 6d made of a material such as alloy) are formed.

The method of manufacturing the monolithic ceramic capacitor 10 of the present invention will be described below.

First, a conductive paste containing a metal powder to be the internal electrode layers 3 and 4 is formed by screen printing on a predetermined region of the ceramic green sheet to be the dielectric layer 2.

Then, a predetermined number of such ceramic green sheets are stacked so that the internal electrode layers 3 and 4 face each other and the internal electrode layers 3 and 4 extend to different end faces, and then cut. Then, the laminated body 1 is obtained, and the laminated body 1 is fired by adding a predetermined atmosphere, temperature and time. As a result, the internal electrode layers 3 and 4 are exposed at the pair of end faces of the laminated body 1.

Next, external electrodes 5 and 6 are formed on both end faces of the laminate 1. Specifically, first, the underlying conductor films 5a and 6a are formed on the surface of the laminated body 1.

The base conductor films 5a and 6a are made of Cu powder and Ni.
A conductive paste prepared by mixing a mixed powder with a powder, a zinc borosilicate glass powder, an acrylic organic binder resin, and an organic solvent such as terpineol is applied to both ends of the laminate 1 by a dipping method, and at 100 to 150 ° C. After drying, it is formed by baking at 750 to 850 ° C. in a nitrogen atmosphere. Here, since the mixed powder of Cu powder and Ni powder is used as the metal powder, Cu is used for the underlying conductor films 5a and 6a.
An alloy of Ni and Ni is formed, and the thermal stress generated in the temperature cycle test or the thermal shock test can be made uniform as compared with the case where the underlying conductor films 5a and 6a are formed by using the Cu powder alone as in the related art.

Then, conductive epoxy thermosetting resin layers 5b and 6b are formed on the surfaces of the base conductor films 5a and 6a by sequentially applying, drying and curing steps.

Such a conductive resin paste is applied and attached by a conventionally known means such as screen printing or dipping. Next, it is temporarily dried at a temperature of 80 to 140 ° C., and thereafter, in a temperature atmosphere of 60 to 120 ° C. for 15 to 15 to completely remove the solvent component in the paste.
Desolvation is performed for 90 minutes. Next, it is cured by heating at a temperature of 150 to 250 ° C. for 30 to 120 minutes,
A conductive epoxy thermosetting resin layer is formed.

Ni plating layers 5c and 6c are formed on the conductive resin layers 5b and 6b by electrolytic plating or the like, and tin-based layers 5d and 6d are similarly formed by electrolytic plating or the like.

In this way, the monolithic ceramic capacitor 10 as shown in FIG. 1 is obtained.

The present invention is not limited to the above embodiment, and various modifications and improvements may be added without departing from the gist of the present invention.

For example, the surfaces of the conductive resin layers 5b and 6b may be covered with a plating layer of Ag, Au, Pd, Pt or the like which is hard to oxidize. As a result, it is possible to prevent the heat treatment involved in the connection and fixing with the conductive resin paste and the oxidation of the external electrodes 5 and 6 due to the change over time due to environmental conditions and the influence of humidity, and the electrical connection with the external circuit is improved. Become.

[0031]

EXAMPLE The above-mentioned base conductor films 5a and 6a are made of Cu and N.
A conductive paste containing a glass frit as a main component of the alloy i was applied in a thickness of 10 to 50 μm, dried and baked.

Next, the conductive resin layers 5b and 6b made of an epoxy thermosetting conductive resin material are formed from a conductive resin paste in which a Cu filler is dispersed in an epoxy resin. Base conductor film 5a, 6a
After being coated on the surface in a thickness of 20 to 100 μm, it is dried, then desolvated at a temperature of 80 to 120 ° C., and then 150 to 2
It was formed by curing at a temperature of 00 ° C.

Next, on the surfaces of the conductive resin layers 5b and 6b, N
i plating layers 5c and 6c are formed by electrolytic plating.
The tin-based layers 5d and 6d are formed on the surfaces of the plated layers 5c and 6c by electrolytic plating, and the total length is 2.0 based on the standard.
A mm type 2012 multilayer ceramic capacitor was obtained.

For the conductive resin layers 5b and 6b, a conductive resin paste in which a Ni-based filler or an Ag-based filler is dispersed in an epoxy-based resin is used, and the monolithic ceramic capacitor 10 is similarly manufactured.

Further, as a comparative example, the conductive resin layer 5
A monolithic ceramic capacitor 10 without b and 6b was prepared in the same manner.

An evaluation test was conducted using the sample of the present invention thus prepared and a comparative example prepared for comparison. The results are shown in Table 1.

[0037]

[Table 1]

As shown in the table, the metal of the internal electrode layers 3 and 4 is changed to N.
i, Cu and the underlying conductor films 5a and 6a
By changing the ratio of Cu and Ni in the resin electrode layer 5
Samples of the present invention in which the metal of b, 6b was changed to Cu, Ni, Ag (Sample Nos. 2 to 6, 9 to 13, 16 to 20, 22)
~ 25) were produced. As a comparative example, the base conductor film 5a,
Samples (sample numbers 1, 7, 8, 14, 15, 21) in which the metal component of 6a was Cu or Ni alone were prepared. Also, samples (Sample Nos. 26 to 29) in which the Ni plating layers 5c and 6c and the tin-based layers 5d and 6d were directly formed on the underlying conductor films 5a and 6a without forming the conductive resin layers 5b and 6b.
Was produced.

A temperature cycle durability test was conducted on these samples.

For the temperature cycle durability test, the sample was tested at -55.
After holding in the atmosphere of ℃ for 30 minutes, in the atmosphere of 150 ℃ 30
The cooling / heating cycle of holding for 1000 minutes was performed 1000 times and 2000 cycles to examine the bonding strength before and after the test. Adhesion strength is 2.5k as an evaluation standard
g. Goods with f or more are excellent products with double circles, 2.0 ~
2.5 kg. Items with f are good products with a circle, 2.0k
g. Those with a value of less than f were regarded as defective products with a cross mark. Also,
After the test, 50 samples were cut and the number of cracks generated in the laminate 1 was examined.

As is apparent from the table, the external electrodes 5, 6
Of the base conductor films 5a, 6 containing an alloy of Cu and Ni
a and the conductive resin layers 5b and 6b formed on the surfaces of the underlying conductor films 5a and 6a, respectively (the sample numbers 2 to 6,
9 to 13, 16 to 20, 22 to 25), the fixing strength was 2.0 kg. It was not less than f and no crack was generated in the laminate 1. In particular, the weight ratio of Cu and Ni is 9
In the range of 5: 5 to 25:75 (Sample No. 2 to
5, 9-12, 16-19, 22-25), and the fixing strength is 2.5 kg. It was a good product of f or higher. These results show that the metal components in the conductive resin layers 5b and 6b are C when the internal electrode layers 3 and 4 are both Ni and Cu.
The same was true in any of u, Ni, and Ag.

On the other hand, Comparative Examples (Sample Nos. 1, 8, 15) in which the metal component of the underlying conductor films 5a, 6a is Cu alone.
No cracks were generated after 1000 cycles, but 2 to 5 cracks were generated in 50 samples after 2000 cycles. This was the same in any case where the metal component in the conductive resin layers 5b and 6b was Cu, Ni or Ag.

On the other hand, in the comparative example (Sample Nos. 7, 14, and 21) in which the metal component of the underlying conductor films 5a and 6a was Ni alone, cracks were observed in 1 of 50 samples after 1000 cycles.
.About.3, and after 2000 cycles, 8 to 10 cracks in 50 samples. This is the conductive resin layer 5
The same was true in the cases where the metal components in b and 6b were Cu, Ni and Ag.

Further, the Ni plating layer 5 is directly formed on the underlying conductor films 5a and 6a without forming the conductive resin layers 5b and 6b.
In the samples (Sample Nos. 26 to 29) on which c, 6c and the tin-based layers 5d and 6d were formed, 21 to 26 cracks occurred in 50 samples after 1000 cycles. Also, 2000
After the cycle, 50 of 50 cracks were generated. This was the same even if the ratio of Cu and Ni was changed.

From these results, the external electrodes 5 and 6 are C
Base conductor films 5a and 5b containing an alloy of u and Ni and a glass component, and a conductive resin layer 5 formed on the surfaces thereof.
b and 6b, and the Ni plating layer 5c formed on the surface thereof.
5d and the tin-based layers 6c to 6d are sequentially laminated, the laminated ceramic capacitor 10 of the present invention has a fixing strength of 2. even after a 2000-cycle temperature cycle durability test.
0 kg. It can be seen that the value is not less than f and that cracks do not occur in the laminate 1.

[0046]

As described above, according to the monolithic ceramic capacitor of the present invention, even when a base conductor film made of an alloy of Cu and Ni and a glass component is formed on both end faces of the laminated body, it is more than in the case of using only Cu. The wettability between the metal component and the glass component is improved. Therefore, the distribution of the metal component and the glass component in the underlying conductor film becomes uniform, and the stress generated during baking becomes uniform in the entire underlying conductor film. For this reason, even if a temperature cycle test or a thermal shock test is performed after solder mounting on the circuit board, the laminated body is not cracked or the external electrodes are not peeled off, and the adhesion strength to the circuit board is also improved. As a result, it is possible to provide a high-quality and long-term reliable multilayer ceramic capacitor.

[Brief description of drawings]

FIG. 1 is an external perspective view of a monolithic ceramic capacitor of the present invention.

2 is a cross-sectional view of the monolithic ceramic capacitor of FIG.

[Explanation of symbols]

10 Multilayer ceramic capacitors 1 stack 2 Dielectric layer 3, 4 internal electrode layer 5, 6 External electrode 5a, 6a Base conductor film 5b, 6b conductive resin layer 5c, 6c Ni plating layer 5d, 6d tin-based layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E001 AB03 AC04 AC09 AF00 AF06                       AH07 AJ03                 5E082 AB03 BC23 BC33 EE04 EE23                       EE26 EE35 FG06 FG26 GG10                       GG11 GG26 GG28 JJ03 JJ12                       JJ21 JJ23 PP03 PP08

Claims (2)

[Claims] 1. A laminated body in which dielectric layers having internal electrode layers containing Ni or Cu as a main component are alternately laminated, and external electrodes connected to the internal electrode layers are formed on both end faces of the laminated body. In the monolithic ceramic capacitor, the external electrode includes a base conductor film containing at least an alloy of Cu and Ni and a glass component, and Cu,
A monolithic ceramic capacitor comprising a conductive resin layer containing at least one of Ni and Ag and a plating layer, which are sequentially laminated. 2. The multilayer ceramic capacitor according to claim 1, wherein the underlying conductor film has a weight ratio of Cu and Ni in a range of 95: 5 to 25:75.