JPH0562516A - Conductive paste - Google Patents

Abstract

PURPOSE:To provide a conductive paste for forming an electrode excellent in solder wettability by suppressing a black body precipitating on the electrode surface formed during baking of conductive paste for a resistor. CONSTITUTION:Bismuth 1 of 3wt.% is added to a conductive paste in which metal powder composed of silver as a main component, a glass component, an organic binder and an solvent are kneaded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste which is applied to a substrate and applied to the substrate to form electrodes on both ends of a resistor formed by firing.

[0002]

2. Description of the Related Art Generally, a metal-based conductive paste used for an electrode of a resistor formed on a substrate such as an aluminum ceramic comprises a metal powder such as silver and palladium, a glass component, an organic binder and a vehicle thereof. Mix and
It is manufactured by kneading this with a three-roll mill or the like.

When forming a resistance element on a fixed resistor, a variable resistor, a hybrid integrated circuit or the like, that is, a resistance element on a ceramic substrate, first, a metal-based material is formed on the ceramic substrate by a method such as screen printing. The electrodes are printed by using a conductive paste, and then dried and baked to form the electrodes. Next, using a conductive paste for a resistor, the resistor is printed by a construction method such as screen printing so as to be connected across the electrodes. Then, the resistive element coated with the conductive paste is dried and fired to form the resistive element.

As described above, the conductive paste has been widely applied to the formation of resistive elements because it can easily form various shaped elements by the printing method.

[0005]

In the manufacturing process of the resistance element described above, a conductive paste containing ruthenium-based metal has hitherto been used. However, when a conductive paste for a resistor having a particularly high content of ruthenium is used in this conductive paste, when the resistor formed by application is fired, the ruthenium contained in the resistor becomes ruthenium oxide and volatilizes. However, it sometimes reacts with bismuth oxide contained in the electrode to be connected to form a black substance on the electrode surface. If this black material is formed on the surface of the electrode, there is a problem in that the solder wettability of the electrode is poor when the lead wire is connected to the electrode and the solder connection becomes difficult.

The object of the present invention is to solve the above problems.
An object of the present invention is to provide a conductive paste which can suppress the generation of a black substance and can form an electrode of a resistor having good solder wettability.

[0007]

The conductive paste of the present invention is a conductive paste prepared by kneading a metal powder containing silver as a main component, a glass component, an organic binder and a solvent.
It is characterized in that the content of bismuth is in the range of 1 to 3% by weight.

[0008]

The present invention will be described below with reference to the drawings.

First, various preliminary experiments were conducted in order to obtain the optimum conductive paste for electrodes according to the present invention. The black substance deposited after firing in the conductive paste for electrodes contained bismuth. We obtained the finding that it is affected by the rate. Therefore, the weight ratio excluding the organic binder and the solvent is mainly 70% silver, and the palladium 10 to 1
About 10 kinds of samples were prepared by adding 1 to 10% of bismuth to a conductive paste containing 5%. Then, these conductive pastes were kneaded using lead borosilicate glass as a glass component as a binder, ethyl cellulose resin as an organic vehicle, and a solvent of terpineol body.

The above-mentioned conductive paste was applied to each ceramic substrate for each sample to form a predetermined electrode pattern. Next, it was dried at a temperature of 150 ° C. for 10 minutes, further heated at a rate of 30 ° C./minute, and held at 850 ° C. for 10 minutes to burn the printed electrode pattern. Then, the same conductive paste (ruthenium content of 40 wt%) for resistance formation as in the conventional case was applied and connected between the two electrodes. Then, this conductive paste was fired under the same conditions as described above.

FIG. 1 is a graph showing the black matter generation rate, solder wetting failure rate, and bismuth content rate after firing of the conductive paste. With respect to the samples described above, the black matter generation rate was measured by a scanning electron microscope, and the bismuth content rate and the black matter generation rate obtained the results shown in the graph of FIG. Also,
Regarding the solder wetting failure rate, a eutectic solder of lead and tin containing 2% of silver was melted at 220 ° C., each sample was immersed in the melted solder, and the wetness of the solder was inspected.
The results shown in the graph of FIG. 1 were obtained.

From this graph, the black matter generation rate correlates with the bismuth content rate, and when the bismuth content rate reaches 3%,
You can see that it does not occur at all. However, when the content is 1% or less, the ability to deposit a metal component on the surface is lost in the cermet state, and the metal portion deposited on the surface is reduced, resulting in poor solder wettability.

Taking these results into consideration, a resistor was manufactured by adding 1 to 3% of bismuth to a conductive paste containing 7% of silver and 10 to 15% of palladium. I was able to obtain a great resistance.

[0014]

As described above, according to the present invention, the electrode generated by firing the conductive paste for resistors with the content of bismuth contained in the conductive paste containing silver or palladium as the main component is 1 to 3%. By suppressing the generation of black matter on the surface, there is an effect that a conductive paste capable of producing a resistor having electrodes having good solderability can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a black matter generation rate, a solder wetting failure rate, and a bismuth content rate after firing a conductive paste.

Claims (1)

[Claims] 1. A conductive paste obtained by kneading a metal powder containing silver as a main component, a glass component, an organic binder and a solvent, wherein the content of bismuth is in the range of 1 to 3% by weight. Conductive paste to do.