JP2001297628A - Electrically conductive paste and ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically conductive paste and ceramic electronic component, in which the strength of connection between an external electrode and a ceramic element assembly and an adhesion of metal plating are secured, and an adhesion among electronic components can be prevented. SOLUTION: In an electrically conductive paste and ceramic electronic component an electrically conductive powder including Ag, glass powder, and an organic vehicle are included, and substantially, the alkaline earth metals and lead are not contained. In the glass powder, alkaline metal oxide, boron oxide, silicon dioxide, zinc oxide, and aluminum oxide are included and when each of them are expressed as M2O (M is at least one of the kinds selected from among Li, Na, K, Rb, Cs, and Fr), B2O3, SiO2, ZnO, and Al2O3, the range with respect to a glass composition of 100 weight % are in the range 5<=M2O<=12, 35<=B2O3<=45, 10<=SiO2<=20, 35<=ZnO<=45, and 1<=Al2O3<=5 (in weight %).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste and a ceramic electronic component, and more particularly, to a conductive paste used for forming external electrodes of a multilayer ceramic capacitor, and a laminate using the same to form external electrodes. It relates to a ceramic capacitor.

[0002]

2. Description of the Related Art A conventional ceramic electronic component, for example, a laminated ceramic electronic component, comprises a ceramic body and external electrodes formed on both end surfaces of the ceramic body. The ceramic body is formed by laminating a plurality of ceramic layers, and in a ceramic electronic component having internal electrodes,
A plurality of internal electrodes are formed between the ceramic layers such that each edge is exposed at any one end surface of the ceramic layer, and the external electrodes are electrically connected to the internal electrodes via the exposed edges of the internal electrodes. Have been.

In the case of a thick film external electrode, a conductive paste is used. This conductive paste is, for example, A
g, Ag / Pd, etc., and a glass frit are dispersed in an organic vehicle comprising an organic binder and an organic solvent, and are applied to the end surface of the ceramic body by dip coating, drying and firing to obtain an external component. An electrode is formed.

Further, in order to improve the solder wettability and solder heat resistance of the external electrode, Ni plating is applied to the external electrode made of a conductive paste, and various electrolytic plating such as Sn plating or Ni plating is applied thereon. There are cases. If this plating process takes a long time, the plating solution travels through the pores inside the external electrode and moves to the interface between the external electrode and the ceramic body, and the bonding strength (tensile strength) of the external electrode
May decrease. As a glass frit conventionally used for a conductive paste for the purpose of preventing this problem, a zinc borosilicate-based glass frit containing a large amount of SiO ₂ having excellent plating dissolution resistance can be cited. However, although the use of these glass frits has the effect of preventing the joint strength from deteriorating, the glass segregates on the surface of the fired external electrode, and a problem arises in that plating cannot be formed uniformly in a subsequent plating process.

[0005] Regarding this problem, Japanese Patent Publication No. 8-1713
According to Japanese Patent Publication No. 6 (1999), it is described that by using a zinc borosilicate glass based glass, it is possible to prevent the bonding strength between the external electrode and the ceramic body from deteriorating due to the plating treatment and to secure the plating adhesion. According to Japanese Patent Publication No. 8-34168, the use of a zinc borosilicate-based glass containing an alkali / alkaline earth metal oxide and lead oxide provides an external electrode and a ceramic body in addition to the above two effects. It is described that a crystal phase is formed at the interface of the ceramic body to suppress the occurrence of cracks in the ceramic body due to thermal shock or the like. In other words, in order to secure the bonding strength of the external electrode, by using glass having excellent wettability with respect to the ceramic body, that is, using a glass having a small contact angle with the ceramic body, the glass at the interface between the external electrode and the ceramic body is Is concentrated and the amount of glass on the surface of the external electrode after firing is reduced to ensure the plating adhesion.

[0006]

However, according to the prior art, since the amount of glass near the surface of the external electrode after firing is small, the sintering near the surface of the external electrode is poor and the electrode film becomes porous. Furthermore, there is little glass in the pores. Therefore, N formed by electrolytic plating
There is a case where i-plating or Sn-plating penetrates and deposits inside the external electrode to form a plating film. The residual stress due to the plating film is very large, and has, for example, various impacts generated during the mounting of the ceramic electronic component, particularly a mechanical stress, and also has an adverse effect of promoting the generation of cracks in the ceramic body.

Further, according to the prior art, when firing the external electrodes, a plurality of ceramic electronic components may adhere to each other via the external electrodes, that is, a so-called "sticking defect" may occur. This is because although the amount of glass present on the surface of the external electrode is small, the glass has good wettability to the ceramic body, so that the surface of the external electrode is in contact with the ceramic body of another ceramic electronic component. This occurs because a plurality of ceramic electronic components are joined together via the glass on the surface of the external electrode.

[0008] Lead borosilicate glass has conventionally been used as a low softening point glass frit, but lead is an environmentally hazardous substance and is regulated on a global scale.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to ensure the bonding strength and plating adhesion between an external electrode and a ceramic body, and to prevent external mechanical stress. Conductive paste capable of preventing deterioration of electrical characteristics as an electronic component and preventing sticking between ceramic electronic components generated during firing of an external electrode, and a ceramic electronic component using the same to form an external electrode Is to provide.

[0010]

In order to achieve the above object, the conductive paste of the present invention is a conductive paste used for forming a thick-film electrode of a ceramic electronic component, and the conductive paste is made of Ag.
Containing a conductive powder, a glass powder, and a vehicle, containing substantially no alkaline earth metal and lead, the glass powder contains an alkali metal oxide, boron oxide, and silicon oxide, It contains zinc oxide and aluminum oxide, each of which is M ₂ O (M is Li, Na, K, Rb,
Cs, Fr), B ₂ O ₃ , S
When expressed as iO ₂ , ZnO, Al ₂ O ₃ , the glass composition 1
5 ≦ M ₂ O ≦ 12% by weight, 35 ≦
B ₂ O ₃ ≦ 45% by weight, 10 ≦ SiO ₂ ≦ 20% by weight, 3
It is characterized in that 5 ≦ ZnO ≦ 45% by weight and 1 ≦ Al ₂ O ₃ ≦ 5% by weight.

The content of the glass powder in the conductive paste of the present invention is preferably 2 to 15 parts by weight based on 100 parts by weight of the conductive powder.

Further, the ceramic electronic component of the present invention is a ceramic electronic component comprising: a laminated body in which a plurality of ceramic layers are laminated; and a pair of external electrodes formed on an end face of the laminated body. Is characterized by being formed using the conductive paste of the present invention.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The glass frit used for the conductive paste of the present invention is hard to wet the ceramic body, that is, has a large contact angle with the ceramic body. Movement of glass from the glass to the interface with the ceramic body is suppressed, and the amount of glass remaining in the external electrode increases. Therefore, the glass exists in the liquid phase in the external electrode even at a high temperature, and the glass in the liquid phase promotes the liquid phase sintering of the external electrode, and the external electrode is densified. Further, most of the pores existing in the fired external electrode are covered with glass.

The alkali metal oxide contained in the glass frit used in the conductive paste of the present invention includes:
Examples include lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, and francium oxide. Of the glass frit 100% by weight, Li ₂ O, N
requires that _{a 2 O, K 2 O,} Rb 2 O, Cs 2 O, the total content of Fr ₂ O in terms of 5 to 12 wt%. That is, if the content is within the above range, the working temperature of the glass, the fluidity of the glass, and the breaking limit value of the ceramic body all become appropriate values, and so-called "sticking failure" does not occur. On the other hand, if the content is less than 5% by weight, the working temperature of the glass increases, and the fluidity of the glass decreases in the firing temperature range. On the other hand, if the content exceeds 12% by weight, the contact angle with respect to the ceramic body is reduced, that is, the wettability with respect to the ceramic body is improved. Therefore, when the external electrodes are fired, the ceramic electronic components adhere to each other. "Stick failure" occurs. Further, the glass and the ceramic body react with each other, and the breaking limit value of the ceramic body decreases.

The boron oxide contained in the glass frit used in the conductive paste of the present invention has a B ₂ O ₃ -equivalent content of 35 to 4% in 100% by weight of the glass frit.
It must be 5% by weight. That is, when the content is within the above range, vitrification is easy, and the fluidity of the glass, the solubility of the external electrode in the plating solution, and the bonding strength of the external electrode are all appropriate values. On the other hand, if the content is less than 35% by weight, vitrification becomes difficult, the fluidity is suppressed, and the sintering of the external electrode is hindered. On the other hand, when the content exceeds 45% by weight, the solubility in the plating solution becomes excessive, and the bonding strength of the external electrode after plating deteriorates.

Further, silicon oxide contained in the glass frit used in the conductive paste of the present invention, 10 to the content of SiO ₂ in terms of the glass frit 100 wt%
It needs to be 20% by weight. That is, when the content is within the above range, the solubility of the external electrode in the plating solution, the softening temperature of the glass, and the bonding strength of the external electrode are all appropriate values. On the other hand, if the content is less than 10% by weight,
The solubility in the plating solution becomes excessive, and the bonding strength of the external electrode after plating deteriorates. In addition, the content is 20% by weight.
If the temperature exceeds the above range, the softening temperature of the glass rises and sintering of the external electrode is suppressed, so that a dense external electrode cannot be obtained, and the bonding strength between the external electrode and the ceramic body decreases.

The zinc oxide contained in the glass frit used in the conductive paste of the present invention has a ZnO equivalent content of 35 to 4% in 100% by weight of the glass frit.
It must be 5% by weight. That is, when the content is within the above range, the softening temperature of the glass, the fluidity of the glass, and the bonding strength of the external electrode are all appropriate values, and so-called "sticking failure" does not occur. On the other hand, if the content is less than 35% by weight, the softening temperature of the glass increases and sintering of the external electrode is suppressed, so that a dense external electrode cannot be obtained,
Also, the bonding strength between the external electrode and the ceramic element decreases. On the other hand, if the content exceeds 45% by weight, vitrification becomes difficult, and the contact angle with the ceramic body is reduced, that is, the wettability with the ceramic body is improved. A so-called "sticking defect" occurs in which the pieces adhere to each other.

The aluminum oxide contained in the glass frit used in the conductive paste of the present invention must have an Al ₂ O ₃ content of 1 to 5% by weight based on 100% by weight of the glass frit. . That is, if the content is within the above range, the softening temperature of the glass and the bonding strength of the external electrode are both appropriate values. On the other hand, if the content is less than 1% by weight, the glass does not melt and an unmelted substance is generated, and a homogeneous glass frit cannot be obtained. On the other hand, if the content exceeds 5% by weight, the softening temperature of the glass rises and sintering of the external electrode is suppressed, so that a dense external electrode cannot be obtained, and the bonding strength between the external electrode and the ceramic element body Decrease.

Further, the conductive paste of the present invention needs to contain substantially no alkaline earth metal oxide in the glass frit. When an external electrode made of a conductive paste using a glass frit substantially containing an alkaline earth metal is fired, the glass is crystallized when the temperature is raised, and the fluidity of the glass is significantly impaired. For this reason, the glass component tends to remain excessively on the surface of the external electrode, and the plating adhesion is extremely reduced.

Further, the conductive paste of the present invention needs to contain substantially no lead component which is an environmentally harmful substance in the glass frit.

The content of glass frit in the conductive paste of the present invention is preferably in the range of 2 to 15 parts by weight based on 100 parts by weight of the conductive powder. When the content is 2 parts by weight or more, the bonding strength between the external electrode and the ceramic body is further improved. On the other hand, when the content is 15 parts by weight or less, so-called "sticking failure" hardly occurs when the ceramic electronic components adhere to each other when the external electrode is fired.

The glass frit may be used alone or in a mixture of two or more kinds as long as it is within the above-mentioned composition range of the present invention.

Next, a multilayer ceramic capacitor will be described as a ceramic electronic component according to one embodiment of the present invention, which will be described in detail with reference to FIG. The multilayer ceramic capacitor 1 includes a ceramic body 2 having a plurality of internal electrodes 3, external electrodes 4 and 4, and Ni plating films 5 and 5.
And Sn plating films 6 and 6. Ceramic body 2
Are a plurality of ceramic layers 2 mainly composed of BaTiO _3.
a is laminated and fired. The internal electrodes 3 are formed by firing the same electrode films formed on a predetermined number of ceramic layers 2a together with the ceramic layers 2a so that the respective edges are exposed on any of the end faces of the ceramic layers 2a. I have. The external electrodes 4 and 4 are a pair of thick-film electrodes formed by applying the conductive paste of the present invention to the end faces of the ceramic body 2, drying and firing, and the internal electrodes 3 exposed on the end faces of the ceramic body 2. , 3 so as to be electrically and mechanically connected to each other.

The shape and material of the ceramic body 2 in the ceramic electronic component of the present invention, the formation position and the number of the internal electrodes 3, the presence or absence of connection with the external electrodes 4 and 4, the internal electrodes 3
The presence or absence of itself, the material of the plating films 5, 5, 6, 6 and the number of layers are not particularly limited to the multilayer ceramic capacitor according to the above-described embodiment.

[0025]

EXAMPLES First, starting materials such as oxides were prepared so as to have the composition ratios shown in Table 1, and the starting materials were mixed at 1000 to 120.
After melting at 0 ° C., the glass was rapidly cooled to vitrify, coarsely pulverized and then finely pulverized to obtain glass frit of Samples 1 to 11 having an average particle diameter of 5 μm.

Next, an organic vehicle was prepared by mixing 25% by weight of an organic binder composed of ethyl cellulose and an alkyd resin and 75% by weight of an organic solvent composed of ethyl carbitol, 1-octanol and a kerosene-based solvent.

Next, 71% by weight of Ag powder as conductive powder and 5% by weight of glass frit of Samples 1 to 11 were
The mixture was mixed with 24% by weight of an organic vehicle, and kneaded and dispersed with three rolls to obtain conductive pastes of Samples 1 to 11.

Next, a ceramic layer containing BaTiO ₃ as a main component is prepared, and an internal electrode and an internal electrode are formed on the surface of a predetermined number of ceramic layers such that one edge is exposed to one of the end faces of the ceramic layer. An electrode film to be formed was printed, and a predetermined number of these ceramic layers were laminated and pressed to prepare a plurality of raw ceramic bodies.

Next, the conductive pastes of samples 1 to 11 were dip-coated on both end surfaces of the raw ceramic body,
After drying for 0 minutes, the mixture is baked at 750 ° C. for 10 minutes in the air to form a pair of external electrodes electrically and mechanically joined to the internal electrodes. A plating film is formed by electrolytic plating,
An Sn plating film was formed on the i plating film by electrolytic plating to obtain multilayer ceramic capacitors of Samples 1 to 11.

Then, for the multilayer ceramic capacitors of Samples 1 to 11, the bonding strength between the Ni plating film and the external electrode and the bending strength, that is, the so-called “sticking failure”, the adhesion force between the components was measured, and these are summarized in Table 1. In addition,
For samples within the scope of the present invention, the evaluation was rated as ○, and for samples outside the scope of the present invention, the evaluation was represented as x.

The plating film thickness was determined by an average value of n = 5 measured by a fluorescent X-ray film thickness meter. The larger the film thickness, the better the plating adhesion, but the larger the Ni film thickness. If it is too large, the bending strength may be deteriorated.

The bonding strength and the bending strength are n =
An average value of 10 indicates that the larger the value, the better. The flexural strength is determined by soldering the multilayer ceramic capacitors of Samples 1 to 11 to the mounting land at the center of the glass epoxy board, and applying force to the center point of the board with a pressure rod to bend the board, and AE (Acoustic Emission) The amount of deflection of the substrate when crack generation sound was detected by the sensor was measured and evaluated.

Further, the measurement of the adhesion force between components in the case of "sticking failure" is performed by baking in a state where an electrode film to be an external electrode of one ceramic electronic component and a ceramic body of the other ceramic electronic component are in contact with each other. This is the average value of n = 10 obtained by measuring the adhesion force between these components, and indicates that the larger the value, the more easily the "sticking failure" is caused.

[0034]

[Table 1]

As is clear from Table 1, samples 1 to 5
The multilayer ceramic capacitor using the glass frit of (1) has an excellent Ni-plated film thickness of 1.21 to 1.33 μm, and therefore has a high flexural strength of 5.51 to 6.09 mm and excellent external electrode bonding strength. 34.7-41.3N
And high and excellent. Also, the fixing force between parts is 7.0 to 8.5N.
And low, which was within the scope of the present invention.

In contrast, B ₂ O ₃ in the glass frit
Of the sample 6 in which the content of Ni was 46% by weight with respect to 100% by weight of the glass frit,
Since the plating film thickness was excessively large at 1.49 μm, the flexural strength was extremely low at 1.86 mm, and the bonding strength of the external electrode was low at 8.8 N, which was inferior. In addition, the adhesion between parts is 1
Since it was 5.8 N, which was higher and inferior than the bonding strength of the external electrode, it was out of the range of the present invention.

The multilayer ceramic capacitor of Sample 7, in which the content of SiO _{2 in} the glass frit was 24% by weight with respect to 100% by weight of the glass frit, was excellent in high flexural strength and low in fixing strength between parts. However, the bonding strength of the external electrode was 20.9 N, which was low and inferior, and thus was outside the scope of the present invention.

The multilayer ceramic capacitor of Sample 8, in which the content of ZnO in the glass frit was 46% by weight with respect to 100% by weight of the glass frit, was excellent in the bonding strength and the bending strength of the external electrode, and was excellent. The plating film thickness was as thin as 1.05 μm, and the inter-part adhesion force showing “sticking failure” was 13.2 N, which was higher and inferior than the bonding strength of the external electrode, and thus was out of the scope of the present invention.

The multilayer ceramic capacitor of Sample 9 in which the content of Al ₂ O _{3 in} the glass frit is 6% by weight with respect to 100% by weight of the glass frit is appropriate when the Ni plating film thickness is 1.33 μm. The bonding strength of the external electrodes was 16.7 N, which was low and inferior.
The flexural strength was 2.51 mm, which was low and inferior, and was out of the range of the present invention.

Further, Na ₂ O and Li ₂ in the glass frit
The total content of O and K ₂ O, that is, the total content of alkali metal oxides is 6% with respect to 100% by weight of the glass frit.
The multilayer ceramic capacitor of Sample 10 which is weight% is
The Ni plating film thickness was 1.20 μm, which was appropriate, and the bonding strength and flexural strength of the external electrode were high and excellent. However, the bonding strength between components was 17.3 N, which was inferior and was out of the range of the present invention.

The multilayer ceramic capacitor of Sample 11 containing CaO, which is an alkaline earth metal in the glass frit, has an extremely thin Ni plating film thickness of 0.51 μm and a bonding strength of the external electrode of 16.1 N. The flexural strength was as low as 2.13 mm. In addition, the fixing force between components was 16.6 N, which was higher and inferior than the bonding strength of the external electrode, and thus was out of the range of the present invention.

[0042]

As described above, the external electrode formed by using the conductive paste of the present invention has excellent shielding properties against the plating solution, prevents the joint strength with the ceramic body after electrolytic plating from deteriorating, and provides a sufficient effect. It is possible to obtain joint strength.

Although the glass component is present on the surface of the external electrode after firing, the glass component present on the surface of the external electrode during plating is slightly soluble in a weakly acidic Ni plating solution. It dissolves and the conductive powder contained in the external electrode is exposed on the surface, so that the plating adhesion is good.

Further, since the fired external electrode is dense and the pores near the surface of the external electrode are filled with glass, the formation of Ni plating film, that is, the precipitation inside the external electrode is small. The crack generation limit of the ceramic body with respect to a specific external stress, that is, the bending strength is improved.

Further, although glass exists on the surface of the external electrode, since the contact angle with the ceramic body is large, even when the external electrode overlaps with another chip at the time of firing the external electrode, the ceramic electronic components can be connected to each other via the glass. There is little so-called "sticking failure" that sticks together, and even if sticking, the sticking force is lower than before.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a ceramic electronic component according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic electronic component 2 Ceramic body 3 Internal electrode 4 External electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E001 AB03 AC04 AC09 AF00 AF06 AH01 AH07 AJ03 5E082 AA01 AB03 BC40 FG26 GG10 GG26 GG28 JJ03 JJ12 JJ13 JJ23 PP03 5G301 DA03 DA34 DA36 DA38 DA39 DA40 DA42 DA53 DD01

Claims (3)

[Claims] 1. A conductive paste for forming a thick-film electrode of a ceramic electronic component, comprising a conductive powder containing Ag, a glass powder, and an organic vehicle, and being substantially alkaline earth earth. Free of metal and lead, the glass powder contains an alkali metal oxide, boron oxide, silicon oxide, zinc oxide, and aluminum oxide, each of which is M ₂ O (M is Li, Na, K, Rb,
Cs, Fr), B ₂ O ₃ , S
When expressed as iO ₂ , ZnO, Al ₂ O ₃ , the glass composition 1
5 ≦ M ₂ O ≦ 12 wt% 35 ≦ B ₂ O ₃ ≦ 45 wt% 10 ≦ SiO ₂ ≦ 20 wt% 35 ≦ ZnO ≦ 45 wt% 1 ≦ Al ₂ O ₃ ≦ 5 wt% with respect to 00 wt% % Of the conductive paste. 2. The conductive paste according to claim 1, wherein the content of the glass powder is 2 to 15 parts by weight based on 100 parts by weight of the conductive powder. 3. A ceramic electronic component comprising: a laminated body formed by laminating a plurality of ceramic layers; and a pair of external electrodes formed on an end surface of the laminated body, wherein the external electrode is formed of a ceramic material. 3. A ceramic electronic component formed by using the conductive paste according to 2.