JPH1012403A - Paste composition for thick film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide paste for a thick film wherein thixotropy property is high, leveling property is excellent, and unevenness due to mesh traces is not left on a surface after coating. SOLUTION: An inorganic functional material is dispersed in organic vehicle and turned into the state of paste. The paste is printed on substrate material like alumina, and an inorganic functional film is obtained. The characteristic of the paste composition for a thick film is that polyhydric alcohol like glycol of 0.01-5wt.% is contained in the organic vehicle. A desirable glycol to be used is selected out of a group composed of ethyl hexanediol, trimethyl pentadiol, butyl ethyl propanediol, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a thick film paste composition for forming an inorganic functional film for use in electronic industrial parts.

[0002]

2. Description of the Related Art Thick film pastes in which an inorganic functional material is dispersed in an organic vehicle are used for forming functional films of various electronic components. For example, a paste mainly composed of silver, gold or silver-palladium is used for a resistor. As a conductive paste for forming electrodes, a paste made of ruthenium oxide and glass is used as a resistance paste, and a glass paste is used as a paste for protecting a resistor film.

[0003] These thick film pastes are usually printed on a substrate of alumina or the like by screen printing or the like, dried and fired to form a functional film according to the purpose of each component. These components have been miniaturized gradually with higher performance and higher density, and the printed pattern of the paste has also become finer. In addition, the problem of sagging of the printed shape is increasing with the miniaturization of the printed pattern, and it is desired to increase the thixotropic property of the paste.

Conventionally, as an organic vehicle used for these thick film pastes, ethyl cellulose dissolved in an organic solvent such as terpimeol has been mainly used. However, in order to enhance the thixotropic property of the paste, more polymerization is required. It has been proposed to use a resin having a high degree or to use various additives.

[0005] When screen printing is performed, irregularities are generated in the applied paste by traces of mesh on the screen. If the viscosity of the paste is low or the thixotropy is small, the screen traces on the paste will be leveled during the application and drying process, and the paste surface will be flat, but the leveling will decrease as the thixotropy increases The unevenness due to the traces of the mesh after printing is transferred to the drying process as it is, and in the part where the thin mesh wires cross, cracks and pinholes are generated in the drying process, which is the quality of the functional film after firing It will affect the characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has a high thixotropy and a good leveling property. It is an object of the present invention to provide a thick film paste that does not leave any irregularities.

[0007]

In order to achieve the above object, the present invention provides a method in which an inorganic functional material is dispersed in an organic vehicle to form a paste, which is printed on a substrate material such as alumina and fired. Thick paste for obtaining an inorganic functional film, characterized by comprising a thick film paste composition comprising 0.01 to 5% by weight of a polyhydric alcohol such as a glycol in the organic vehicle. It is. Further, the glycols used in the present invention are preferably selected from the group consisting of ethylhexanediol, trimethylpentadiol, and butylethylpropanediol.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The leveling property of a paste is affected not only by the viscosity of the paste but also by the wettability between the paste and the substrate. Most of the substrates on which the thick film paste is used are metal oxides, and alumina is particularly preferably used. The surface of these metal oxide substrates is generally hydrophilic, and it is preferable that the paste to be printed is also hydrophilic because it can be uniformly applied to the substrate without generating pinholes. However, terpineol, which has been conventionally used as a solvent, is a substance that shows some hydrophilicity compared to petroleum-based solvents, but hardly mixes with water.

As a solution, it is conceivable to use butyl carbitol or butyl carbitol acetate, which is used as a solvent having higher hydrophilicity, in place of terpineol. As a result, it was found that uniform coatability was good and pinholes were hardly generated. However, a drawback of these solvents is that the urethane resin used for squeezing during screen printing swells, thereby deteriorating the life of squeezing and lowering printing accuracy.

[0010] Then, when a study was made on a solvent capable of improving the leveling property of the paste without swelling the squeeze of the printing press, it was found that glycols could be used as the solvent. And glycols,
It was found that not only can it be used alone, but also its effect can be sufficiently exerted by adding a very small amount of glycols to terpineol which has been conventionally used as a solvent.

In addition, for use in a thick film paste, it is necessary to consider the volatility of the solvent, and the boiling point of the solvent is 2
It is considered that the temperature is desirably about 00 ° C. to 300 ° C. This is because, when a solvent having a lower boiling point is used for the paste, the solvent paste volatilizes during the printing operation and the viscosity changes, and the solvent having a higher boiling point is dried. This is because it is difficult to perform efficient drying in the process.

In view of these, in the present invention, ethyl hexanediol was selected as a glycol to be added to the organic vehicle. In addition, methylpentadiol and ethylheptanediol are generally solid at room temperature, but the same effect can be exerted when used in combination with another solvent. The addition amount in the organic vehicle is preferably 0.01% to 5% by weight. If it is less than 0.01%, the effect is not sufficiently exhibited, and if it exceeds 5%, no further effect can be obtained.

[0013]

EXAMPLES The following examples (Examples 1, 2 and 3)
The present invention will be described more specifically with reference to Comparative Examples (Comparative Examples 1 and 2). Table 1 shows the composition of the organic vehicle used in each example in% by weight. Using a vehicle shown in Table 1, a glass powder and a pigment having the composition shown in Table 2 were mixed and dispersed therein to prepare a glass paste. These pastes were formed on a 200-mesh stainless steel mesh with an emulsion thickness of 10 μm. After screen printing on an alumina substrate in a pattern of 1 mm ² according to a usual method,
The paste film was dried at 130 ° C., and the presence or absence of pinholes in the dried paste film and the presence or absence of swelling of the squeeze in the printing machine were determined by observation of 20 samples in each example. The results are shown in Table 1. The reason why the determination of pinholes was made on the dried film without performing the film formation after baking is that when baking was performed, the pinholes generated during drying were filled, making it difficult to determine whether or not the pinholes were generated.

[0014]

[Table 1] Example Example Example Example Comparative example Comparative example 1 2 3 12 (Vehicle composition) α-terpineol 95 95 95 96 40 Butyl carbitol 0 0 0 0 56 Acetate 2-ethyl-1,3 hex 1 0 0 0 0 Sanji All 2,2,4-trimethyl-1,3 0 1 0 0 0 pentanediol 2-n-butyl-2ethyl-1,3 0 0 1 0 0 propanediol ethyl cellulose 4 4 4 4 4 (Performance test) Pinhole ○ ○ ○ × ○ Swelling ○ ○ ○ ○ ×

[0015]

(Paste composition) Glass powder: 75% by weight Pigment (Cu (Cr, Fe) O ₂ ): 5% by weight Vehicle: 20% by weight (Glass composition) SiO ₂ : 20% by weight PbO: 60% by weight B ₂ O ₃ : 5% by weight Al ₂ O ₃ : 5% by weight

From the results shown in Table 1, no pinholes were found during drying in Examples 1, 2, and 3 and Comparative Example 2, whereas pinholes were generated in Comparative Example 1 and Comparative Example 2 Is good for pinholes, but swells the squeeze of the printing press. In the case of Comparative Example 1 in which pinholes occurred during drying, 1-2% of the fired products were defective. In addition, when the paste of the present invention according to Examples 1, 2 and 3 was used, the squeeze of the printing press did not swell, and the thixotropy of the paste was inhibited because the paste was mainly composed of terpineol. In addition, since the leveling property of the paste can be improved by the addition of polyhydric alcohol, the obtained product has no trace of mesh after printing, and all products were accepted.

[0017]

As described above, the paste for a thick film according to the present invention has high thixotropy, has good leveling properties, and has no irregularities due to mesh traces on the surface after application, so that it is used for electronic parts. It is suitable as a thick film paste.

Claims (2)

[Claims] A thick film paste for obtaining an inorganic functional film by dispersing an inorganic functional material in an organic vehicle to form a paste, printing this on a substrate material such as alumina, and firing it. A thick film paste composition comprising a polyhydric alcohol in an organic vehicle in an amount of 0.01 to 5% by weight. 2. The paste composition for a thick film according to claim 1, wherein the polyhydric alcohol is a glycol selected from the group consisting of ethylhexanediol, trimethylpentadiol, and butylethylpropanediol.