JPH0945130A - Conductor paste composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper conductor paste forming a good conductor film suitable for baking in a large quantity by dispersing the copper powder, an inorganic binder, and the TiO2 powder having the primary grain size of a specific value or below at specific pts.wt. respectively in an organic vehicle. SOLUTION: An inorganic binder 4-9 pts.wt. of one of the glass frit such as PbO-SiO2 -B2 O3 and a metal oxide such as Cu2 O or a mixture of them is combined into the mixed copper powder 100 pts.wt. preferably having the specific surface area about 0.5-2.0m<2> /g. The TiO2 powder 0-0.2 pts.wt. having the primary grain size 0.05μm or below is added, and it is kneaded and dispersed in an organic vehicle dissolved with ethyl cellulose in an organic solvent such as terpineol to obtain a conductor paste. A conductor film, which generates no color irregularity when a large quantity of this paste is printed on a ceramic substrate and put in a baking furnace for baking and is excellent in solder wettability and aging strength, is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor paste composition for printing and firing an insulating substrate to form a thick film wiring board, and more particularly to a conductor paste composition using copper as a conductive component. Is.

[0002]

2. Description of the Related Art A conventional thick film wiring board is formed by printing and firing a conductor paste composition containing silver or copper as a main component and an inorganic binder and an organic binder on an insulating substrate made of 96% alumina. Those that do are common. In recent years, in response to the demands for downsizing and high density of thick film wiring boards, attention is being paid to a copper paste that can form a conductor that is less likely to cause migration and has excellent electrical characteristics. Various improvements have been attempted because severe conditions are required for the solder characteristics of the conductor film. For example, as an example of improvement based on addition of a metal oxide, JP-A-3-223
In No. 06, the addition of ZnO powder and TiO ₂ improves solder wettability and adhesion strength.
In No. 0, 7 to 20% by weight of TiO ₂ was added for the purpose of laser processing through holes, but solder wettability was not considered. Further, there is also seen an example in which copper powder having an average particle diameter of 1 μm or less is used to densify the conductor film to improve the adhesion strength and conductivity after being left at high temperature.

[0003]

However, after the copper paste is printed on the substrate, the copper paste is fired in an inert atmosphere such as nitrogen containing a slight amount of oxygen, which causes burnout of the organic components in the paste. It tends to be sufficient. Especially,
When a large number of substrates are fired at once, or when the copper conductor pattern area on the substrates is large, the unburned residue of organic components increases, which adversely affects the conductor film after firing, causing discoloration of the conductor film or solder wettability. Appears as deterioration. This tendency becomes remarkable when the conductor film obtained by firing is dense. On the other hand, when the density of the conductor is reduced, the deterioration of the characteristics due to the remaining organic components is eliminated, but the problem that the adhesion strength is greatly deteriorated when left at high temperature remains.

The present invention solves the above problems and has a discoloration-free appearance and good solder wettability even when printed on an alumina substrate and baked in large quantities, and at the same time, deteriorates adhesion strength after being left at high temperature. The object is to provide a copper conductor paste composition for forming a small conductor film.

[0005]

The present invention provides a conductor paste composition comprising a copper powder and an inorganic binder dispersed in an organic vehicle, and a TiO having a primary particle size of 0.05 μm or less.
It is the one to which the ultrafine powder of ₂ was added. This is because the effect of controlling the film quality is difficult to appear with TiO ₂ having a size exceeding 0.05 μm. Further, it is necessary that the addition amount of TiO ₂ ultrafine powder does not exceed 0.2 parts by weight with respect to 100 parts by weight of copper powder. This is because if the addition amount exceeds 0.2 parts by weight, the solder wettability deteriorates and the conductor resistance value increases.

As the conductive powder used in the present invention, the copper powder conventionally used in the conductor paste can be used, but the copper powder having a specific surface area of about 0.5 m ² / g and the specific surface area of the copper powder can be used. Particularly desirable results are obtained when powders having a fine particle size of about 2.0 m ² / g are mixed and used.

In the present invention, the inorganic binder is Pb.
O-SiO ₂ -B ₂ O _{3 system, PbO-Al 2 O 3 -B} 2
Glass frit such as O ₃ system and PbO—SiO ₂ —B ₂ O ₃ —ZnO system and Cu ₂ O, Bi ₂ O ₃ , MnO ₂
, Metal oxides such as CoO and NiO, or a mixture thereof can be used. The blending amount of these inorganic binders needs to be 4 to 9 parts by weight with respect to 100 parts by weight of copper powder. This is because if the amount is less than 4 parts by weight, the adhesion strength deteriorates, and if the amount exceeds 9 parts by weight, the solder wettability deteriorates.

In the present invention, as the organic vehicle, resins such as ethyl cellulose and polyisobutyl methacrylate are used as terpineol, butyl carbitol acetate,
Those dissolved in an organic solvent such as 2,2,4 trimethylpentanediol monoisobutyrate are preferably used.

[0009]

EXAMPLE In a vehicle prepared by dissolving ethyl cellulose resin in 2,2,4 trimethylpentanediol monoisobutyrate, copper powder and glass frit (PbO by weight composition) were used.
54%, B ₂ O ₃ 14%, SiO ₂ 3%, ZnO 24
%, TiO ₂ 5%), copper oxide powder and TiO ₂ ultrafine powder (particle diameter of primary particles 0.02 μm) are shown in Table 1.
Was mixed and kneaded and dispersed to prepare conductor pastes of Examples, Comparative Examples and Conventional Examples. In the table, the copper powder A has a specific surface area of 1.
8 m ² / g, copper powder B having a specific surface area of 0.6 m ² / g was used.

[0010]

[Table 1]

96% of the conductor paste prepared in this way
After printing and drying on an Al ₂ O ₃ substrate, 90 using a conveyor furnace
The sample was fired in a nitrogen atmosphere at 0 ° C. peak for 10 minutes to prepare an evaluation sample having a copper conductor film. At that time, the substrates were arranged and fired so that the total area of the conductor-printed coating film occupied 90% or more of the area on the belt of the conveyor furnace. The screen is 32
A 5-mesh one was used.

The appearance of the evaluation sample thus prepared was visually observed to check for the presence of color unevenness. The one in which the color unevenness is not seen is indicated by ◯, and the one in which the color unevenness exists is indicated by x.

Next, the prepared evaluation sample was dipped in rosin flux and then dipped in lead-tin eutectic solder at 250 ° C. for 5 seconds, and then a solder-plated copper wire having a diameter of 0.6 mm was soldered to a 2 mm × 2 mm pad. It was soldered with a iron and the initial adhesion strength was measured by a peel test. Similarly, the sample to which the solder-plated copper wire was attached was left to stand in a constant temperature bath of 150 ° C. for 1000 hours, returned to room temperature, and then subjected to a peel test to obtain the aging strength.

Further, another evaluation sample was dipped in rosin flux, dipped in lead-tin eutectic solder at 220 ° C. for 5 seconds, cooled, and visually observed for a 5 mm × 5 mm square pattern.
The solder wettability was examined. Wet area 95
% Or more was evaluated as ◯, 85 to 95% as Δ, and less than 85% as x. The results are summarized in Table 2.

[0015]

[Table 2]

As is clear from Table 2, the evaluation sample using the conductor paste of this example has good firing appearance, solder wettability, and adhesion strength. On the other hand, in the evaluation sample using the conductor paste of the comparative example, the aging strength is poor when the inorganic binder is small, and the solder wettability is poor when the inorganic binder is excessive. Further, it can be seen that the solder wettability is poor in the sample in which the addition amount of the TiO ₂ ultra-fine powder is excessive, and the color unevenness occurs in the sample in which the TiO ₂ ultra-fine powder is not added.

[0017]

As described above, the conductor paste composition of the present invention does not cause color unevenness even when printed on a ceramic substrate and then placed in a large amount in a firing furnace and fired. This is a conductor paste composition which is capable of forming a conductor film excellent in wettability and aging strength on the surface of a substrate and is excellent in both mass productivity and basic properties of a conductor.

Claims (1)

[Claims] 1. (a) 100 parts by weight of copper powder, (b) 4 to 9 parts by weight of an inorganic binder, and (c) a primary particle size of 0.05.
A conductor paste composition comprising (e) an organic vehicle and 0 to 0.2 parts by weight of a TiO ₂ powder having a particle size of not more than μm.