TWI402871B - Nickel paste for monolithic laminating ceramic capacitors - Google Patents

Description

Nickel paste for laminated ceramic capacitors

The present invention relates to a nickel paste used for forming an internal electrode of a laminated ceramic capacitor (MLCC).

In recent years, with the miniaturization of electronic devices, various electronic components have been rapidly miniaturized, and small-sized multilayer ceramic capacitors have also been used. High capacity. The multilayer ceramic capacitor has a structure of mutually overlapping, sintered and integrated ceramic dielectric layer and internal electrode layer. Further, in the case of the internal electrode material of the multilayer ceramic capacitor, precious metals such as palladium have been used in the past, but now, nickel has become the mainstream for cost reduction.

In general, in the manufacturing step of the laminated ceramic capacitor, for example, a nickel paste in which a nickel powder as an internal electrode material is dispersed in a vehicle liquid is printed on a ceramic substrate or a ceramic green plate, and heated in a state in which the layers are stacked in multiple layers. And integration. Next, in an oxidizing atmosphere gas or an inert atmosphere, a binder is removed at 500 ° C or lower, and then heated and fired in a reducing atmosphere under an unoxidized internal electrode.

However, in the above-described firing step, since the ceramic dielectric layer does not conform to the sintering-contraction of the nickel internal electrode layer, structural defects such as interlayer peeling or cracking tend to occur. Especially with small size. The capacity is increased, and the generation of structural defects becomes remarkable, in addition to the increase in the number of layers or the thinning of the thickness of the ceramic dielectric layer.

Relative to the related problems, it is eagerly studied to reduce the thickness of the internal electrode layer of nickel and to alleviate the mismatch of sintering-contraction. For one of the methods, there is a method of making the particle shape of the nickel powder into a spherical shape and smoothing the surface to improve the filling property of the nickel particles (International Publication No. 99/42237 pamphlet).

Further, in the debinding agent step, the nickel oxide powder is oxidized and subjected to intense sintering-shrinkage simultaneously with the reduction in the subsequent calcination step in the reducing atmosphere gas, and as a result, the sintering-contraction is not integrated, and the interlayer peeling is easily promoted. . Therefore, there is a method of adding phosphorus (P) to nickel powder (Japanese Laid-Open Patent Publication No. 2002-150834), or a method of controlling an oxide film on the surface of a nickel powder to improve oxidation resistance (Japanese Laid-Open Patent Publication No. 2001-152202). Countermeasures.

However, in recent years, the thinning of the ceramic dielectric layer and the nickel internal electrode layer or the increase in the number of layers of the ceramic dielectric layer and the nickel internal electrode layer are further increased, and the method is as described above. It is difficult to sufficiently eliminate structural defects.

In view of the above-mentioned conventional problems, the present invention provides a structure defect preventing interlayer peeling or the like in the debonding step of the laminated ceramic capacitor and the subsequent firing step, and is suitable for the formation of the nickel internal electrode. Nickel paste is for the purpose.

The inventors have focused on the occurrence of structural defects in the fabrication process of laminated ceramic capacitors, and have found that the ceramic dielectric layer and nickel are changed by the interaction of the nickel powder and the binder in the debonding step. The sintering-contraction of the internal electrode layer does not fit.

That is, in the conventional nickel paste, the thermal decomposition of the binder is accelerated by the catalytic activity on the surface of the nickel particles in the middle of the debonding step, for example, in the case where the binder is ethyl cellulose or the like, at about 260. Thermal decomposition near °C, judged to cause intense gas generation. The thermal decomposition of the binder at this point is limited to the vicinity of the surface of the nickel particles, and the other binders are substantially undecomposed. Therefore, it is understood that the gas generated by the partial decomposition of the binder is enclosed in the space, and the gap between the nickel internal electrode layer and the ceramic dielectric layer is enlarged by the gas.

The adhesion of the nickel internal electrode layer to the ceramic dielectric layer is weakened due to the intense gas generation caused by the partial decomposition of the binder on the way of the debonding step, or a partial interlayer peeling occurs. The subsequent firing step caused the structural defects of the laminated ceramic capacitor. In recent years, since the particle size of the nickel particles is made smaller by the thinning of the single layer of the nickel internal electrode layer, the catalytic activity on the surface of the nickel particles is also increased, and the above phenomenon becomes a larger problem.

In order to solve the above problems, the inventors of the present invention have repeatedly studied intensively and found that by adding a small amount of a sulfur-containing compound to the nickel paste, the catalytic activity on the surface of the nickel particles thermally decomposed by the binder can be suppressed, and the debonding agent can be prevented from being removed. The present invention has been completed by the intense gas generation caused by the partial thermal decomposition of the steps.

In other words, the nickel paste for laminated ceramic capacitors provided by the present invention is characterized in that nickel is dispersed in a vehicle liquid in which a binder is dissolved in a solution, and a sulfur-containing organic compound is contained. The content of the sulfur-containing organic compound is preferably 0.01 to 1% by weight in terms of sulfur relative to nickel.

Further, in the nickel paste for laminated ceramic capacitors according to the above aspect of the invention, the sulfur-containing organic compound is selected from the group consisting of three At least one of a mercaptan and a sulfate-containing compound is preferred.

According to the present invention, in the debonding step of the laminated ceramic capacitor, the thermal decomposition of the binder on the surface of the nickel particles in the paste and the intense gas generation accompanying it can be suppressed, preventing the subsequent firing step. The formation of structural defects such as interlayer peeling. Therefore, the shape or particle size of the nickel powder is not controlled, and although a binder or a solvent is used, only a very small amount of a sulfur-containing organic compound is added to the nickel paste, and a multilayer ceramic capacitor having no structural defects can be easily manufactured. .

The nickel paste for forming an internal electrode of the multilayer ceramic capacitor in the present invention is a paste obtained by dispersing a nickel powder in a vehicle solution in which a binder is dissolved in a solvent, and further contains a sulfur-containing organic compound.

The sulfur-containing organic compound added to the nickel paste is an organic compound containing sulfur (S), and it is necessary to have a significant influence on the viscosity characteristics of the paste. Further, the sulfur-containing organic compound is decomposed in the debonding step because the temperature at which the binder component of the nickel paste starts to decompose. When it disappears, the desired effect cannot be expected, and when it remains after the debonding step, it itself carbonizes at a high temperature and partially hinders the possibility of sintering the nickel powder. From these viewpoints, the thermal decomposition temperature of the sulfur-containing organic compound is 200 ° C or more and 400 ° C or less in an oxygen-containing atmosphere gas and 200 ° C in an inert atmosphere gas in accordance with a normal debinding agent condition. Above, 700 ° C or less is preferred.

For example, even if a fine powder of nickel sulfate or sulfur monomer is considered to have a similar gas generation preventing effect, it is dissolved in a general paste from the viewpoint of being uniformly dispersed on the surface of the fine nickel powder. The solvent used is preferred. Moreover, since only the amount of addition can be reduced, it is preferable to selectively act on the surface of the nickel particles with a small amount and to exhibit an effect of suppressing thermal decomposition of the binder.

From these points of view, in the case of sulfur-containing organic compounds, three can be suitably used. One type or two or more types may be used for the thiol group and/or the sulfate group-containing compound. So-called three The thiol is, for example, a compound group having a structure shown by the following Chemical Formula 1, wherein R is a -SH group, a -NHR ₁ group, or a -NR ₂ R ₃ group (wherein R ₁ , R ₂ , R ₃ means an aliphatic or aromatic hydrocarbon group).

Even shown in Chemical Formula 1 Among the mercaptans, from the viewpoints of the above thermal decomposition temperature and solubility, the preferred three In terms of mercaptans, 1,3,5-three having R as -SH is exemplified. -2,4,6-trithiol, R is -N(C ₄ H ₉ ) ₂ 6-dibutylamino-1,3,5-tri -2,4-dithiol, R is -N(C ₆ H _{1 3} ) ₂ 6-dihexylamino-1,3,5-three -2,4-dithiol, R is -N(C ₈ H _{1 7} ) ₂ 6-dioctylamino-1,3,5-three -2,4-dithiol, R is -N(C _{1 0} H _{2 1} ) ₂ 6-diaminol-1,3,5-three -2,4-dithiol, R is -N(C _{1 2} H _{2 5} ) ₂ 6-di-dodecyl-1,3,5-tri -2,4-dithiol.

Further, in addition to the chemical formula 1, it is also possible to use 1,3,5-three which replaces the H of the thiol group in the chemical formula 1 with sodium. -2,4,6-trithiol. Single sodium (FMN), or 1,3,5-three -2,4,6-trithiol. Single potassium, 1,3,5-three -2,4,6-trithiol. Monoethanolamine (FME), 1,3,5-three -2,4,6-trithiol. Diethanolamine (FDE), 1,3,5-three -2,4,6-trithiol. Triethylamine (F.TEA), 1,3,5-three -2,4,6-trithiol. Octamine, 1,3,5-three -2,4,6-trithiol. Tetrabutylammonium salt, 1,3,5-three -2,4,6-trithiol. Bis(tetrabutylammonium) (F2A), 6-anilino-1,3,5-three -2,4-dithiol (AF), 6-anilino-1,3,5-three -2,4-dithiol. Monosodium (AMN), 6-anilino-1,3,5-three -2,4-dithiol. Triethylamine, 6-dibutylamino-1,3,5-three -2,4-dithiol. Monosodium (DBMN), 6-dibutylamino-1,3,5-three -2,4-dithiol. Monoethanolamine (DBME), 6-dibutylamino-1,3,5-three -2,4-dithiol. Ethylamine, 6-dibutylamino-1,3,5-three -2,4-dithiol. Triethylamine, 6-dibutylamino-1,3,5-three -2,4-dithiol. Butylamine (DBB), 6-dibutylamino-1,3,5-three -2,4-dithiol. Tetrabutylammonium salt (DBA), 6-dibutylamino-1,3,5-three -2,4-dithiol. Tetrabutyl phosphonium salt, 6-diarylamino-1,3,5-three -2,4-dithiol, 6-diarylamino-1,3,5-three -2,4-dithiol. Monosodium (DAMN), 6-diarylamino-1,3,5-three -2,4-dithiol. Monoethanolamine (DAME), 6-diarylamino-1,3,5-three -2,4-dithiol. Butylamine, 6-diarylamino-1,3,5-three -2,4-dithiol. Ethylenediamine, 6-diarylamino-1,3,5-three -2,4-dithiol. Ethyltriamine, 6-octylamino-1,3,5-three -2,4-dithiol, 6-octylamino-1,3,5-three -2,4-dithiol. Single sodium Mercaptans.

Further, the sulfate-containing compound may be an aliphatic or aromatic hydrocarbon compound containing sulfate SO ₃ or a salt thereof, and specifically, sodium dodecyl sulfate CH ₃ (CH ₂ ) _{1 1} SO ₃ may be mentioned. Na, sodium dodecylbenzenesulfonate C _{1 2} H _{2 5} C ₆ H ₄ SO ₃ Na, and the like.

Although it is not described that the sulfur-containing organic compounds inhibit the intense gas generation on the way of the debonding step, it is considered to be because The sulfur of the mercaptan-based SH or the sulfuric acid-containing SO ₃ is adsorbed on the surface of the nickel particles to make it free from catalytic activity, and to prevent partial thermal decomposition of the binder. Especially considered to be three Since the thiol exhibits strong reactivity with the metal via the S group of the SH group, it is more strongly adsorbed on the surface of the nickel powder particles. Further, the nickel particles to which the sulfur-containing organic compound is adsorbed have an advantage that both the dispersibility and the corrosion resistance in the vehicle are improved.

The content of the sulfur-containing organic compound in the nickel paste is preferably in the range of 0.01 to 1% by weight in terms of sulfur, and more preferably in the range of 0.02 to 0.5% by weight, based on the weight of the nickel. When the content of the sulfur-containing organic compound is 0.01% by weight or less, the effect of suppressing thermal decomposition of the binder is insufficient. Further, even if the content is more than 0.5% by weight, it is not considered to have an effectful increase, and in addition to simply increasing the cost, the possibility of adversely affecting the characteristics of the electronic component when it exceeds 1% by weight is not preferable. Further, under the conditions of the process of using other materials or pastes combined with the nickel paste, even if the content of the sulfur-containing organic compound exceeds 1% by weight, it is also applicable.

These sulfur-containing organic compounds are mainly composed of a sulfur-containing portion such as SH or SO ₃ concentrated on the surface of the nickel particles, so that a sufficient effect is obtained with a very small amount of addition, which is much less than, for example, uniformly dispersing sulfur inside the nickel particles. The amount of the effect is sufficient. Further, when the paste contains an additive component other than the excess nickel, there is a possibility that the reliability of the final electronic component is adversely affected, so that the sulfur-containing organic compound having a sufficient effect in a very small amount is also considered from this viewpoint. For the benefit.

The method of adding the sulfur-containing organic compound is preferably added simultaneously with other additives in the production of the paste. For example, a method of re-kneading or the like before adding the paste prepared in the usual manner may be employed, and the sulfur-containing organic compound is dissolved in advance from the viewpoint of effectively uniformly coating the nickel particles with the sulfur-containing organic compound. It is preferred to dissolve the binder in a vehicle composed of a solvent. Further, in the case where a dispersant is used as the additive, it is considered that the action of adsorbing the nickel particles is preferentially inhibited and the action of the sulfur-containing organic compound is inhibited. In these cases, it is desirable to adjust the order of addition of the suitable dispersant.

Further, the solvent, the binder, and the nickel powder constituting the nickel paste may be the same as those conventionally known. For example, in terms of a solvent, terpineol, butyl carbitol acetate, butyl carbitol, dihydroterpineol, dihydroterpene alcohol acetate, other paraffinic hydrocarbon solvent, or the like can be used. Further, as the binder, cellulose such as ethyl cellulose or polyvinyl butyral can be used.

Hereinafter, examples of the invention will be specifically described.

Determining the thermal decomposition temperature of the binder and starting from the debonding agent in terms of the partial thermal decomposition of the binder on the way to the debonding step of the nickel paste (around 260 ° C) and the degree of intense gas generation associated with it The amount of weight reduction of the binder at 300 ° C was evaluated for the effect on the nickel particles in the above thermally decomposed slurry and the effect of the sulfur-containing organic compound added to the paste.

[Comparative example]

First, a coating liquid composed of ethyl cellulose and terpineol (excluding nickel powder) was applied to a PET film at a thickness of 100 μm using a coating roll, and dried at 90 ° C for 6 hours, and then only in the mortar. The dried film was pulverized and sieved with a 100 mesh sieve to obtain a dry liquid of the vehicle liquid.

In order to evaluate the thermal decomposition temperature of the binder and the weight loss at 300 ° C for the vehicle-dried body powder, a differential thermal analyzer (TG-DTA2000SA, manufactured by Brukaykes, Inc., TG-DTA2000SA) was used. The evaluation was carried out at a heating rate of 5 ° C / min in a nitrogen flow of a nitrogen flow rate of 200 ml / min.

As a result, the decomposition temperature of the binder was 325 ° C, and the weight reduction was performed approximately in the same manner, and partial thermal decomposition of the binder and intense gas generation accompanying the same were not caused. In addition, the amount of weight loss at 300 ° C in the differential thermal analysis of the vehicle liquid was 0.06 wt% in the case where the theoretical weight reduction amount of the binder in the nickel paste was determined by the following calculation formula.

[calculation]

Theoretical weight reduction of the binder in the nickel paste (% by weight) = weight loss at 300 ° C (% by weight) in the differential thermal analysis of the vehicle liquid × weight ratio of the binder in the nickel paste

[Examples 1~10]

50 parts by weight of nickel powder [manufactured by Sumitomo Metal Mining Co., Ltd., product name YH-641, 0.4 μm average particle size], 50 parts by weight of ethyl cellulose and terpineol were added in the same manner as in the comparative example. The composition of the vehicle (however, the weight of the adjusted ethyl cellulose is 3% by weight relative to Ni), and is shown in Table 3 below. Mercaptan (TST), which is kneaded by a three-roll mill [manufactured by Inoue Co., Ltd., 43/4×11 S-type rolling mill], and kneaded to a particle size of 10 μm in FOG specifications (particle size). The following is to adjust the nickel paste.

Also, the three used The type of thiol (TST) is as shown in the following table, corresponding to R in the chemical formula 1, and R=-N(C ₄ H ₉ ) ₂ 6-dibutylamino-1,3,5-three -2,4-dithiol (DB), R=-N(C ₆ H _{1 3} ) ₂ 6-dihexylamino-1,3,5-three -2,4-dithiol (DH), R=-N(C ₈ H _{1 7} ) ₂ 6-dioctylamino-1,3,5-three -2,4-dithiol (DO), R=-N(C _{1 0} H _{2 1} ) ₂ 6-diamidino-1,3,5-three -2,4-dithiol (DD), R=-N(C _{1 2} H _{2 5} ) ₂ 6-di-dodecyl-1,3,5-tri -2,4-dithiol (DL). Also, shown in Table 1 The amount of thiol (TST) added is in terms of sulfur relative to the weight of nickel.

In the same manner as the comparative example, each of the obtained nickel pastes of Examples 1 to 10 was applied to a PET film at a thickness of 100 μm using a coating roll, and dried at 90 ° C for 6 hours. Then, the dried film was pulverized only with a mortar, and sieved with a 100 mesh sieve to obtain a dried nickel powder paste.

For the nickel paste dry powder, in order to evaluate the thermal decomposition temperature and weight reduction of the binder, a differential thermal analyzer (TG-DTA2000SA, manufactured by Brukaykes, Inc.) was used in comparison with the above comparative example. The analysis was carried out at a temperature increase rate of 5 ° C / min in a nitrogen flow of a nitrogen flow rate of 200 ml / min.

Further, from the weight loss amount (% by weight) determined by differential thermal analysis at 300 ° C, and the theoretical weight reduction amount obtained in the above Comparative Example, the theoretical weight reduction amount (0.06% by weight) was calculated. The weight reduction amount at 300 ° C) is a reduction ratio at 300 ° C at 1 [i.e., weight loss at 300 ° C (% by weight) / theoretical weight loss (% by weight). The results of these assessments are summarized in Table 1 below.

[Example 11]

Except three The addition period of the thiol was carried out in the same manner as in Example 4 except that the paste was kneaded. Specifically, 50 parts by weight of a vehicle composed of ethyl cellulose and terpineol was added to 50 parts by weight of nickel powder [manufactured by Sumitomo Metal Mining Co., Ltd., product name YH-641, 0.4 μm average particle diameter]. (Adjusting the weight of ethyl cellulose to 3 wt% with respect to Ni), after kneading in a three-roll mill, changing the obtained paste into adding kneading three DB of mercaptans (TST).

With respect to the obtained nickel paste, a nickel powder dried body powder was prepared in the same manner as above, and the thermal decomposition temperature of the binder and the weight reduction amount and the reduction ratio at 300 ° C were determined by differential thermal analysis, and the results were combined. Table 1 below.

[Reference example]

In addition to using sodium dodecyl sulfate (SDS) instead of three A nickel paste was produced in the same manner as in Example 4 except for the mercaptan (TST). With respect to the obtained nickel paste, a nickel powder dried body powder was prepared in the same manner as above, and the thermal decomposition temperature of the binder and the weight reduction amount and the reduction ratio at 300 ° C were determined by differential thermal analysis, and the results were combined. Table 1 below.

[Comparative example]

Production did not add any kind of three A conventional nickel paste of a mercaptan (TST) type and sodium dodecyl sulfate (SDS) is used as a comparative example. Specifically, 50 parts by weight of a vehicle composed of ethyl cellulose and terpineol was added to 50 parts by weight of nickel powder [manufactured by Sumitomo Metal Mining Co., Ltd., product name YH-641, 0.4 μm average particle diameter]. However, the weight of the ethyl cellulose was adjusted to be 3% by weight based on Ni, and it was kneaded by a three-roll mill to form a paste.

The nickel paste of the comparative example was applied onto a PET film at a thickness of 100 μm in the same manner as the above-mentioned comparative examples and examples, and dried at 90 ° C for 6 hours to pulverize only the dried film with a mortar, using a 100 mesh sieve. For screening, a nickel paste dried body powder was obtained.

With respect to the nickel paste dried body powder of this comparative example, the thermal decomposition temperature of the adhesive, the weight reduction amount at 300 ° C, and the reduction ratio were evaluated by differential thermal analysis in the same manner as in the above Comparative Example and Example, and the results were combined. See Table 1 below.

As is known from the evaluation results of the comparative examples in Table 1, no one is added The conventional nickel paste of mercaptan (TST) and sodium dodecyl sulfate (SDS) causes the intense heat of the binder not only at 325 ° C which is the decomposition temperature of the usual binder, but also around 260 ° C on the way. break down. The result was that the weight loss at 300 ° C was as large as 1.75 wt%, and the reduction ratio at 300 ° C when the theoretical weight reduction in the comparative example of only the vehicle was 1 was extremely large 29.1. Therefore, it is known that a large amount of gas is generated therefrom, and structural defects such as interlayer peeling are likely to occur in the laminated ceramic capacitor.

In addition, in the nickel paste relating to each example of the present invention, by adding three Any of the mercaptan (TST) type and sodium dodecyl sulfate (SDS) was compared with the nickel paste which did not contain such comparative examples, and the reduction ratio at any of 300 ° C was greatly lowered. Further, it is known that thermal decomposition at a temperature of about 260 ° C is not caused, and the weight reduction is performed approximately simultaneously, and since the decomposition temperature of the binder rises to be higher than 325 ° C, the generation of a strong gas in the middle of the debonding step is suppressed. Therefore, it is known to reduce and improve the occurrence of structural defects such as interlayer peeling in the laminated ceramic capacitor finally obtained after the subsequent firing step.

Claims (3)

A nickel paste for a laminated ceramic capacitor, which is used for forming an internal electrode of a laminated ceramic capacitor, characterized in that a nickel powder is dispersed in a vehicle liquid in which a binder is dissolved in a solvent, and Dithiol or tri Three of trithiols Mercaptans. For example, the nickel paste for the multilayer ceramic capacitor of the first application of the patent scope, wherein the three The content of the thiol is 0.01 to 1% by weight in terms of sulfur relative to nickel. For example, the nickel paste for laminated ceramic capacitors of claim 1 or 2, wherein the three Mercaptans 1,3,5-three -2,4,6-trithiol, 6-dibutylamino-1,3,5-three -2,4-dithiol, 6-dihexylamino-1,3,5-three -2,4-dithiol, 6-dioctylamino-1,3,5-three -2,4-dithiol, 6-diaminol-1,3,5-three -2,4-dithiol, and 6-di-dodecyl-1,3,5-three -2,4-dithiol.