JPS61188473A - Production of conductor paste - Google Patents

Abstract

PURPOSE:To obtain a conductor paste with improved reliability in prolonged use, by mixing an inorganic oxide powder with a mixed powder comprising a secondary particle of an Ag powder and a Pd power and kneading the mixture with a vehicle. CONSTITUTION:A silver powder is mixed with a palladium powder in a twin- cylinder mixer for about 10hr to form a secondary particle of a finely divided silver and palladium. An inorganic oxide powder is added to and mixed with the secondary powder in the twin-cylinder mixer for about 1.5hr to disperse it in the secondary silver-palladium particle. A vehicle is added to the product and the mixture is kneaded by means of a triple roll mill to form a conductor paste. The use of the conductor paste as an internal electrode improves the tensile strength by about 3 times on average. In all the conventional products, breaking is caused at the internal electrode while, in the present conductor paste, the proportion is about 50%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to multilayer ceramic capacitors, multilayer ceramic capacitors,
The present invention relates to a method for manufacturing a conductive paste used for forming internal electrodes of wiring boards, laminated ceramic electrostrictive elements, etc.

[Conventional technology]

Conventionally, this type of conductor paste mainly consists of silver powder, palladium powder, inorganic oxide powder such as glass, and a vehicle. The powder and the inorganic oxide powder were mixed at the same time, and after mixing, a vehicle was added and kneaded using a three-roll mill or the like to form a paste.

[Problem that the invention seeks to solve]

The conventional conductor paste described above is made by simultaneously mixing silver powder, palladium powder, and inorganic oxide powder, and as a result, the inorganic oxide powder exists in a disordered state between each particle of the silver powder and palladium powder. However, during firing, only the silver component evaporates independently and the alloying of silver and palladium is not promoted, resulting in low conductivity. , vacancies were generated due to evaporation of the silver component], resulting in extremely weak resistance to thermal, mechanical, and mechanical stress. Especially laminated ceramic 4. - In the case of electrostrictive elements, extreme mechanical stress is constantly applied in a direction perpendicular to the laminated surface of the element, so the bonding strength between the internal electrodes, ceramic, and glass interfaces is extremely important. When conventional conductive paste was used, due to the reasons mentioned above, cracks, gluing, and breakage occurred at the interface between the internal electrode and the ceramic during repeated driving, resulting in extremely poor reliability during long-term practical use. .

[Means for solving problems]

The present invention has been made in order to eliminate such conventional drawbacks. First, silver powder and palladium powder are mixed to form secondary particles of these particles, and then an inorganic oxide powder is added.
It is characterized in that it includes a step of dispersing inorganic oxide powder between the secondary particles, and then adding a vehicle and kneading it to form a paste.

That is, the aim of the present invention is to mix silver powder and palladium powder in advance to form secondary particles of silver and palladium, whereas conventional pastes mix silver powder, palladium powder, and inorganic oxide powder at the same time. Because of this, there is no inhibition of alloying of silver and palladium by the inorganic oxide powder during firing, and therefore evaporation of the silver component is prevented.

Therefore, the above-mentioned electrical conductivity and thermal/mechanical stress can be improved, and the conventional drawbacks can be eliminated.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the manufacturing process of the conductive paste of the present invention.

In the present invention, silver powder and palladium powder are first mixed in a V-type mixer for 10 hours to form finely divided secondary particles of silver and palladium, and then inorganic oxide powder is mixed in the same V-type mixer. is added and mixed for 1.5 hours to disperse the inorganic oxide powder between the silver/palladium secondary particles, and a vehicle is added thereto and kneaded in a three-roll mill to produce a paste-like conductive paste.

Next, an example in which a conductive paste according to an embodiment of the present invention is applied to a product will be described.

FIG. 2 shows a manufacturing process for a laminated ceramic electrostrictive element using the conductive paste according to the present invention as an internal electrode.

As shown in Figure 2, first, a mixture of inorganic oxide powders consisting of lead oxide, nickel oxide, titanium oxide, niobium oxide, zirconium oxide, etc., mixed with an organic binder and an organic solvent is used to form a film using the slab casting method. Form a green sheet. Next, internal electrodes are formed on the green sheet by screen printing using the conductor paste according to the present invention. The composition of this conductor paste is 70 wt% of silver powder, 30 wt% of 1L palladium powder, and 15 wt$ of inorganic oxide powder with the same composition as green seeds added to the silver-palladium mixed powder, in accordance with the firing temperature conditions of the electrostrictive element. It consists of Next, all of the green sheets printed with the internal electrodes are punched into a predetermined shape, and a predetermined number of sheets are laminated and bonded under heat using a hot press or the like to obtain a laminate.

Further, this laminate was fired under conditions where the peak temperature was maintained at approximately 1100° C. for 2 hours, and the fired product was cut into a predetermined shape to form a multilayer ceramic electrostrictive element 1 as shown in FIG. obtain. In this example, the shape was 3 mm long, 2 m wide, and 9 nm thick. Note that □ symbol 2 is an internal electrode forming layer.

〔Effect of the invention〕

FIG. 4 is a diagram showing the results of a tensile test of ceramic electrostrictive elements using the conductor paste according to the present invention and the conductor paste according to the conventional method as internal electrodes. The tensile direction is the direction indicated by the arrow 3 in FIG. This is perpendicular to the internal electrode printing surface. As can be seen from FIG. 4, by using the conductor paste according to the present invention as an internal electrode, the tensile strength was improved by about three times on average.

In addition, as for the fracture mode, all of the conventional products were fractured at the internal electrode portion, whereas the fracture mode of the present invention product was approximately 50%.

This is because, in the conductive paste according to the present invention, silver and palladium are reliably alloyed after firing, and the mechanical strength of the internal electrode itself and the bondability with the ceramic material of the ceramic electrostrictive element are improved.

[Brief explanation of drawings]

Figure 5 is a conventional conductor paste manufacturing process diagram, Figure 1 is:
A manufacturing process diagram of the conductive paste according to the present invention, FIG. 2 is a manufacturing process diagram of a ceramic electrostrictive element using the conductive paste according to the present invention as an internal electrode, FIG. 3, and a ceramic electrostrictive element manufactured according to FIG. FIG. 4 is a diagram showing the tensile strength in a tensile test of ceramic electrostrictive elements using conductor bases of the present invention and a conventional conductor base. 1... Ceramic electrostrictive element, 2... Internal electrode formation layer, 3... Tensile test direction. Kaya 5 times

Claims (1)

[Claims] A step of mixing silver powder and palladium powder to form a mixed powder consisting of secondary particles, and adding an inorganic oxide powder to the mixed powder to disperse and mix the inorganic oxide powder between the secondary particles. 1. A method for producing a conductive paste, the method comprising: adding a vehicle and kneading the paste to form a paste.