JP2000315421A - Copper conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide copper conductive paste having low specific resistance of a conductor capable of being sintered at not higher than 700 deg.C and securing sufficient adhesive strength to an insulator. SOLUTION: This copper conductive paste contains at least one of copper powder and copper oxide powder, and organic vehicle. A thermal decomposition temperature of resin in the organic vehicle of the paste in nitrogen is set 200-350 deg.C. With this composition, sintering density is improved in sintering at not higher than 700 deg.C, sufficient adhesive strength after heat aging is secured. Thus, excellent effects such as not only improved yields of products but also greatly improved reliability can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper conductive paste used for forming a copper conductor pattern by coating and firing on an insulator such as ceramic.

[0002]

2. Description of the Related Art A technique for forming a conductor pattern by applying a predetermined pattern of an Ag-Pd-based conductive paste on an insulating substrate such as ceramic or glass by screen printing or a direct drawing method and firing the paste. Is widely used as a thick film technology. Recently, in such a thick film technique, a copper conductive paste has tended to be used instead of the conventional Ag-Pd-based conductive paste. This is because the copper conductor has low resistance and excellent migration resistance, and can form a wiring pattern of a fine circuit.

Generally, this copper conductive paste is obtained by dispersing copper powder or copper oxide powder in an organic vehicle together with glass frit as required. The copper powder or the copper oxide powder is sintered in a non-oxidizing atmosphere to form a thick-film conductor. In addition,
The glass frit has an effect of improving the adhesive strength of the conductor to the substrate. The organic vehicle is an organic liquid medium that enables the copper or copper oxide powder to be applied to a substrate, and is obtained by dissolving a resin in a solvent.

[0004]

As described above, the copper conductive paste contains a resin in its organic vehicle.
The copper conductive paste is applied to an insulating substrate or the like and then fired in a non-oxidizing atmosphere such as a nitrogen gas. When the firing temperature is relatively high, around 900 ° C., the resin in the organic vehicle is sufficiently decomposed and scattered, and the copper atoms in the paste are given a sufficient driving force, so that a dense fired film is obtained. Is obtained.

However, when characteristics are easily affected by heat, for example, when a resistor or the like is on an insulating substrate, it is necessary to fire the copper conductive paste at a low temperature of, for example, 700 ° C. or less. In this case, if the decomposition temperature of the resin in the organic vehicle is high, the resin component remains in the fired film and inhibits sintering. And since the firing temperature is low,
A sufficient diffusion driving force cannot be given, and a dense fired film cannot be obtained. For this reason, when a conductor is formed by applying and baking a copper conductive paste to an insulator such as a ceramic, the specific resistance of the conductor increases, and a sufficient adhesive strength of the conductor to the insulator cannot be obtained. In particular, as a result of the decrease in the adhesive strength after heat aging, the yield of the obtained product is reduced, and there is a problem that the reliability is lacking.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a conductor having a low specific resistance and a sufficient adhesive strength to an insulator. To provide a copper conductive paste.

[0007]

In order to achieve the above object, a copper conductive paste of the present invention is a copper conductive paste containing at least one selected from copper powder and copper oxide powder, and an organic vehicle. The thermal decomposition temperature of the resin in the organic vehicle in nitrogen is 200 to 350 ° C.
It is characterized by being.

[0008] The copper conductive paste is heated to 700 ° C.
It is characterized by being fired below.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The copper conductive paste of the present invention is obtained by dispersing copper powder and / or copper oxide powder in an organic vehicle, and has a thermal decomposition temperature of resin in the organic vehicle in nitrogen. Is in the range of 200 to 350 ° C.

As described above, since the resin contained in the copper conductive paste is decomposed at a temperature of 200 to 350 ° C. at an early stage of firing, the resin remains when fired at a temperature of 700 ° C. or less and inhibits sintering. In addition, the increase in the sintering density can reduce the resistance of the conductor and suppress the decrease in the adhesive strength after thermal aging.

When the decomposition temperature of the resin in the conductive paste is lower than 200 ° C., the resin is decomposed during drying after the paste is applied, and the strength of the dried coating film cannot be sufficiently obtained. The wiring pattern may be damaged during handling. On the other hand, the decomposition temperature of the resin in the organic vehicle is 350
If the temperature is higher than 0 ° C, the resin component remains, and the fired film cannot be sufficiently densified at a low temperature of 700 ° C or lower. Therefore, the decomposition temperature of the resin in the organic vehicle is 200-350.
C. is preferred.

The resin used includes, for example, ethyl cellulose resin, polyvinyl alcohol, and acrylic resin. However, the type of the resin is not particularly limited, and the thermal decomposition temperature of the resin in nitrogen is 200 to 200. It must be in the range of 350 ° C.

Examples of the solvent include, but are not particularly limited to, terpineol, various glycols, various cellosolves, and acetates. It can be appropriately selected and used depending on the type of the resin, the coating method, and the like.

Further, as the copper powder or copper oxide powder,
Various known copper powders can be used. Although there is no limitation on the method for producing the powder, the shape, and the like, it is preferable to use a copper or copper oxide powder having a particle diameter of 1 to 10 μm from the viewpoint of ease of pasting or printability.

Further, the copper conductive paste of the present invention can be a copper conductive paste to which glass frit is added in order to increase the adhesive strength to the substrate after coating and firing. The glass frit in this case is not particularly limited, and for example, borosilicate-based glass, zinc borosilicate-based glass, or the like can be used as appropriate.

[0016]

EXAMPLES Examples of the copper conductive paste according to the present invention will be described below. First, as a resin constituting one component of the organic vehicle of the conductive paste, five kinds of resins shown in Table 1 having different thermal decomposition temperatures in nitrogen were prepared. In Table 1, those marked with * are out of the scope of the present invention.

[0017]

[Table 1] Next, a copper conductive paste was prepared by weighing and kneading the paste composition so as to be 76% by weight of copper powder, 3% by weight of copper oxide powder, 7% by weight of glass frit, and 14% by weight of organic vehicle. The average particle size of the copper powder is 2 μm.
And a copper oxide powder having an average particle diameter of 1 μm. As the glass frit, a lead borosilicate glass material having an average particle size of 3 μm was used. Table 1 shows the organic vehicles.
Each of the resins shown in Table 1 was dissolved in a terpineol-based solvent or an alcohol-based solvent.

Thereafter, these copper conductive pastes were applied on an alumina substrate by a screen printing method and dried at 150 ° C. for 10 minutes. Further, by baking at a maximum temperature of 600 ° C. for 1 hour in a nitrogen atmosphere, a copper conductor having a thickness of 12 μm was formed.

Next, with respect to the obtained conductor, the conductor resistance and the adhesive strength to the substrate at the initial stage and after the heat aging were measured. Table 2 shows the results. The sample numbers in Table 2 correspond to the sample numbers in Table 1, and those marked with * are outside the scope of the present invention.

The conductor resistance (mΩ / □) has a dimensional relationship (L / W = 100) in which the length (L) and the width (W) are 100: 1.
It is obtained by measuring the resistance value between two points of the conductor pattern having the ratio of 100/1) by a four-terminal method. The adhesive strength (Kgf) is determined by soldering a lead wire to a conductor formed by sintering a copper conductive paste.
This value is obtained by pulling the lead wire. That is, Sn-P containing Ag whose temperature was adjusted to 235 ° C.
b. A conductor having a size of 2 mm × 2 mm was immersed in the eutectic solder for 5 seconds, and then the conductor was immersed in a 0.8 mm diameter.
After soldering the tin-plated copper wire, the tensile strength was measured by pulling the tin-plated copper wire at a speed of 20 cm / min using a tensile tester.

The adhesive strength immediately after soldering is measured as the initial adhesive strength, while the adhesive strength at 150 ° C. is 1000
Adhesive strength after heat aging treatment
It was measured as the adhesive strength after heat aging.

The quality of each of the obtained characteristic values is determined as follows.
The conductor resistance should be 3.5 mΩ / □ or less.
The case where it exceeded 5 mΩ / □ was judged as not. Regarding the adhesive strength, 3.0 Kgf or more is considered good at the initial stage, and 3.0 Kgf is considered.
Less than or equal to negative. After thermal aging, 1.0 kgf or more was regarded as good, and less than 1.0 kgf was regarded as bad.

[0023]

[Table 2] As is clear from Table 2, the conductors made of the copper conductive pastes within the scope of the present invention of Sample Nos. 1 to 3 have conductor resistances of 2.5 mΩ / □ or less as compared with those outside the scope of the present invention. It can be seen that the density is low and the sintering density is improved. Regarding the adhesive strength, the thick film conductor made of the copper conductive paste within the range of the present invention is 3.5 kgf or more at the initial stage, which is stronger than that outside the range of the present invention. 5K
gf, and a decrease in reliability due to a decrease in adhesive strength is also suppressed.

In the above description, the case where the copper conductive paste is applied and baked on the alumina substrate has been described, but the present invention is not limited to this. That is, the same effect can be obtained even when used for other insulating substrates, for example, low-temperature sintered glass ceramic substrates. In addition, even when the copper conductive paste does not contain glass frit, although the adhesive strength to the substrate is inferior to the case where glass frit is contained, the effect of similarly increasing the sintering density and lowering the conductor resistance is obtained. Obtainable.

[0025]

As is apparent from the above description, in the copper conductive paste of the present invention, the thermal decomposition temperature of the resin contained in the organic vehicle in nitrogen is 200 to 350 ° C.
It is to be. As a result, the sintering density is improved even in firing at 700 ° C. or less, and it is possible to secure sufficient adhesive strength after heat aging, and not only the yield rate of products but also the reliability is greatly improved. An excellent effect that it can be achieved can be obtained.

Claims (2)

[Claims] 1. A copper conductive paste containing at least one selected from copper powder and copper oxide powder and an organic vehicle, wherein the resin in the organic vehicle has a thermal decomposition temperature in nitrogen of 200 to 350 ° C. A copper conductive paste, comprising: 2. The copper conductive paste according to claim 1, wherein the copper conductive paste is fired at 700 ° C. or lower.