JPH1074419A - Conductive paste composition for terminal electrode of chip resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductivity, adhesion, wettability, and solder waste resistance with a good balance by using, in a conductive paste composition, Ag having an effective characteristic, or an Ag conductive component such as a mixture or alloy of Ag with other noble metal. SOLUTION: A conductive paste composition for terminal electrode of chip resistor formed by dispersing a conductive component consisting of metal powder and an inorganic binder in a vehicle contains 50-87wt.% of at least one kind selected from the group consisting of silver single body and mixtures and alloys of silver with other noble metal powders. It also contains 3-10wt.% of a glass binder containing no Bi2 O3 and 0.1-15wt.% of a metal oxide, bichloride or boride selected from tin, iridium, rhodium, ruthenium and rhenium alone or in combination of two or more thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste in which a conductive component and an inorganic binder used for a terminal electrode material of a chip component are dispersed in an organic vehicle. The present invention relates to a conductive paste having good resistance to solder erosion when mounted on a substrate and suitable as an electrode composition for a chip resistor.

[0002]

2. Description of the Related Art In recent years, with the high-density mounting of electronic circuits,
2. Description of the Related Art Chip mounts for mounting a large number of miniaturized circuit components (referred to as chip components) such as miniaturized chip resistors and chip capacitors on a circuit board at the same time are widely used. These chip components are necessarily provided with lead terminal electrodes for mounting on a circuit board. A thick film conductive paste composition that has been widely used as a terminal electrode material in the past contains a conductive component, a binder, and an organic vehicle as main components. As the conductive component, fine powder of noble metal such as palladium (Pd), platinum (Pt) or silver (Ag) or a mixture or alloy thereof, an oxide of palladium and silver or a mixture thereof is widely used. As a binder, a glass binder is used, and as an organic vehicle, an inert organic liquid is used. The conductive component, the glass binder, and the inert organic vehicle are mixed together and dispersed by mechanical mixing to produce a paste composition having a suitable consistency and rheology.

In general, such a chip component is mounted on a pattern surface of a circuit board by soldering. In a circuit pattern of a copper-clad laminate for a printed circuit, a land portion where terminals of the chip component are located is provided. The permanent fixation is performed by using the molten solder. Therefore, this conductive paste composition is required to have not only adhesive strength and conductivity after forming the terminal electrode but also solderability. The solderability of the terminal electrode refers to good solder wettability and solder erosion resistance required from the soldering of the terminal electrode at the time of mounting or repairing the chip component on the circuit board.

[0004]

The inventor of the present invention has found the following problems as a result of studying the above-mentioned prior art. In a conductive paste composition which is a terminal electrode material of these chip components, it is practically advantageous to use an Ag-based conductor component which has low conduction resistance, good solder wettability and can be oxidized and fired as a conductive component. It is. However, when a terminal electrode is formed using a conductive paste composition using an Ag-based conductor component, there has been a problem that solder erosion resistance is poor. Furthermore, when forming a terminal electrode of a RuO ₂ -based or pyrochlore-based chip resistor that needs to be fired in an oxidizing atmosphere, there is a problem that the resistance value fluctuates after the electrode is formed.

[0005] The first problem described above is that when a conventional conductive paste composition is used for forming a terminal electrode of a chip component and soldered directly to the electrode, Ag, which is a main conductive component of the terminal electrode, is soldered. So-called solder erosion and tin (Sn), which is one of the components of the solder, diffuses into the electrode. If solder erosion of the electrodes occurs when mounting components,
Poor connection reduces reliability. In addition, when solder erosion of the electrode occurs at the time of repairing a component, there is a problem that the solder hardly wets the electrode and the component cannot be mounted. The diffusion of tin into the electrode breaks the adhesion at the interface between the electrode and the chip component body. In order to avoid this, silver and palladium are used as conductive components of the electrodes, and a method of alloying to suppress the diffusion of silver into the solder may be adopted. In some cases, the above-mentioned solder erosion cannot be prevented, and there is a problem that the conditions under which the solder can be used are limited.

A second problem is that when a terminal electrode of a chip resistor is formed by firing using a conductive paste composition in a manufacturing process of the chip resistor or the like, mutual contact between the resistor and the terminal electrode occurs. Diffusion and thermal stress occur, causing the resistance of the resistor to fluctuate greatly.

[0007] An object of the present invention is to provide a conductive paste composition which is required as a terminal electrode using Ag-based conductor components such as Ag or a mixture or alloy of Ag and other noble metals having the above-mentioned effective properties. Conductivity, adhesiveness, solder wettability and solder erosion resistance required when soldering on the substrate can all be obtained in a well-balanced manner, and terminal electrodes of chip resistors can be formed. An object of the present invention is to provide a conductive paste composition. Another object of the present invention is to provide the above conductive component, a glass binder having plating solution resistance in a solder plating step, tin,
Iridium, rhodium, ruthenium, and metal oxides selected from rhenium, pyrochlore or boride alone, or by containing two or more conductive inorganic filler, by solving the problem of soldering chip resistor An object of the present invention is to provide a conductive paste composition capable of forming a terminal electrode.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for producing a conductive material, comprising the above-mentioned Ag-based conductor component, a glass binder having plating solution resistance and a conductive inorganic filler.
The present inventors have found that it is possible to form a terminal electrode of a chip resistor in which all of solder wettability and solder erosion resistance can be obtained in a well-balanced manner, and completed the present invention. A conductive paste composition for a terminal electrode of a chip resistor in which a conductive component comprising a metal powder and an inorganic binder according to the first invention of the present application and an inorganic binder are dispersed in a vehicle is a simple substance of silver, a mixture of silver and another noble metal powder. And at least one member selected from the group consisting of alloys in an amount of 50 to 87% by weight.
A glass binder containing bO and SiO ₂ as main components and not containing Bi ₂ O ₃ is ₃ to 10% by weight, and tin,
It is characterized by containing 0.1 to 15% by weight of a metal oxide selected from iridium, rhodium, ruthenium and rhenium, pyrochlore or boride alone or two or more thereof. The conductive paste composition for a terminal electrode of a chip resistor according to the second invention of the present application is the conductive paste composition according to the first invention, further comprising B ₂ O ₃ as a component of the glass binder. Features.

In the conductive paste composition of the present invention, even if the Ag-based conductive component is eroded by solder after the formation of the terminal electrode, the conductive inorganic filler remains in the conductor thick film forming the terminal electrode, so that the conductive paste composition can be sufficiently formed. With such a structure, it is possible to prevent a reduction in reliability due to poor connection due to solder erosion and a failure to mount chip components due to deterioration in solder wettability.
The conductive component used in the present invention has low conduction resistance, good solder wettability, and at least one selected from the group consisting of silver, palladium, a mixture thereof, and an alloy thereof that can be oxidized and fired. Can be used. A mixture of these with other noble metal powders can also be used. These conductive components are used in the form of a fine powder. The particle size of the conductive metal powder is not particularly critical so long as it is a size suitable for the method to be applied (usually screen printing), but is preferably in the range of about 0.1 to 5 microns.

The glass binder as the inorganic binder used in the present invention has a high plating solution resistance and does not react with the above-mentioned conductive components, and the metal particles forming the conductive components in the firing step are sintered. Any material can be used as long as it has sufficient viscosity and glass fluidity at the sintering temperature in order to assist in sintering. Thus, a wide variety of oxide glasses containing conventional glass-forming and glass-modifying components can be used,
In particular, glass such as lead borosilicate and lead silicate itself has a softening point in the range of about 450 to 600 ° C. and is excellent from the viewpoint of plating solution resistance, so that such a PbO—SiO ₂ glass frit is used. And PbO-S
preferably used iO ₂ -B ₂ O ₃ based glass frit. When a glass binder containing Bi ₂ O ₃ is used for the glass composition, the plating solution resistance is low, and it cannot be used for the conductive paste composition of the present invention. The particle size of the glass binder has no particular critical value. However, the glass particles should range from 0.1 to 10 microns (preferably 0.5 to 5 microns) with an average particle size of 2 to 3 microns. Fine glass of less than 0.1 micron has a very large surface and requires a large amount of organic medium to obtain suitable fluidity as a printing paste. On the other hand, in the case of particles larger than 10 microns, printing becomes an obstacle.

The conductive inorganic filler used in the present invention includes: (1) iridium oxide: Ir ₂ O ₃ , IrO ₂ (iridium-based pyrochlore: Pb ₂ Ir ₂ O _7-x , Bi ₂ Ir ₂ O
_7-x , Lu ₂ Ir ₂ O ₇ ) (2) Rhodium oxide: Rh ₂ O ₃ , RhO ₂ , RhO
₃ (Rhodium pyrochlore: Pb ₂ Rh ₂ O _7-x , Bi _{2
Rh 2 O 7-x, Tl} 2 Rh 2 O 7) (3) ruthenium _{oxide: RuO 2, RuO 3, RuO} 4
(Ruthenium-based pyrochlore: Pb ₂ Ru ₂ O _7-x , Bi _{2
Ru 2 O 7-x, Tl} 2 Ru 2 O 7) (4) rhenium _{oxide: Re 2 O 3, ReO 3} , Re 2 O 7 (5) Tin oxide: SnO ₂ (6) borides: LaB ₆ , Ni ₃ B, and Ni ₂ B.

In the present invention, the conductive component of the inorganic solid component is 5% based on the total weight of the conductive paste composition.
It contains 0 to 87% by weight, 3 to 10% by weight of a glass binder, and 0.1 to 15% by weight of a conductive inorganic filler. In the present invention, the above-mentioned conductive powder and the glass binder and other inorganic fillers are dispersed in an organic vehicle, and are usually manufactured as a dispersion called “paste” having semi-liquid softness. Can be. The ratio of organic vehicle: inorganic solids in the dispersion in the thick film conductive paste composition of the present invention depends on the method of applying the paste and the type of organic medium used and can vary. Usually, to obtain good coating, the dispersion should be 50-90% by weight of inorganic solids
And 50 to 10% by weight of vehicle.

All inert liquids can be used as vehicles. Any one of water or various organic liquids, with or without thickeners and / or stabilizers and / or other common additives, can be used as vehicles. Examples of organic liquids that can be used are aliphatic alcohols, esters of such alcohols such as acetate and propionate,
Terpenes such as pine oil, terpineol and the like, as well as solvents such as pine oil and a solution of a resin such as polymethacrylate of lower alcohol or ethyl cellulose in a monobutyl ether of ethylene glycol monoacetate. The vehicle can contain a volatile liquid to promote rapid solidification after application to the substrate, or the vehicle can consist of it. Preferred vehicles are those based on ethyl cellulose and β-terpineol.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment. The numbers representing the component ratios are% by weight unless otherwise specified. Glass used as the inorganic binder in the following Examples and Comparative Examples are a mixture of glass frit PbO-SiO ₂ -B ₂ O ₃ based compositions.

[0015]

【Example】

Examples 1 to 12 Ag powder (pulverized to a particle size of 1 μm or less), Pd
A conductor paste composition was prepared by kneading powder, glass powder, ethyl cellulose, and terpineol into a paste, mixing with a mixer, and milling. The proportion of each component is as follows

[0016]

[Table 1]

[0017]

[Comparative example]

Comparative Examples 1 to 3 Comparative Examples 1 to 3 were prepared in the same manner as in Example 1 using the following components.
A conductive paste composition of No. 3 was prepared.

[0018]

[Table 2]

With respect to the conductive paste compositions of these Examples and Comparative Examples, the evaluation of the conductivity (whether or not poor conduction occurred) due to solder erosion during soldering was examined by the following method. The conductive paste compositions of Examples and Comparative Examples
In a measurement circuit for evaluating the relationship between solder erosion and conductivity after printing, drying, and firing the conductive paste composition shown in FIG. 1 using a 6% alumina substrate 1, a pattern 2 shown in FIG. When dried for 10 minutes, thick film 20-24
After printing to a micron size, it was fired in an ordinary electric belt furnace at 850 ° C. for 10 minutes in an ordinary electric belt furnace so that the total firing time was about 30 minutes.

The conductive paste compositions of Examples and Comparative Examples fired in this manner were applied to a molten eutectic solder (Sn: Pb = 63: 37) maintained at about 280 ° C. for 5 seconds and 10 seconds.
The resistance value of the thick-film conductor formed on the substrate when immersed for seconds, 15 seconds and 20 seconds was measured by using a generally used four-terminal resistance measurement method as shown in FIG. In FIG. 1, a resistance measurement device (for example, ADVANTEST R6871 DIGITAL MULTIMETER) 3 electrically connected to the thick film conductor pattern 2 formed on the substrate in FIG. 1 was used. The results are shown in Table 3 below. From Table 3, it can be seen that in the conductor paste composition using the Ag-based conductor component according to the present invention, the paste containing the conductive inorganic filler further suppresses conduction failure due to solder erosion. Of course, it has been confirmed that all of the other basic performance characteristics required for such a conductive paste composition, such as conductivity, adhesiveness, and the like, are more than practically acceptable.

[0021]

[Table 3]

[0022]

The effects obtained by the typical ones of the present invention will be briefly described as follows. A conductive paste composition for a terminal electrode of a chip resistor including a metal powder of a conductive component, an inorganic binder and a vehicle, an Ag-based conductor component, a glass binder having plating solution resistance in a solder plating step, and tin. , Iridium, rhodium, ruthenium and rhenium metal oxides, pyrochlores or borides alone, or by containing two or more conductive inorganic fillers, even if the Ag-based conductive component is eaten by the solder, Was able to maintain. In addition, a conductive paste composition was obtained which was capable of forming a terminal electrode of a chip resistor having sufficient conductivity and adhesive strength, and having all properties of solder wettability and solder erosion resistance in a well-balanced manner. .

[Brief description of the drawings]

FIG. 1 shows a measurement circuit used for evaluating conductivity due to solder erosion after printing, drying, and firing a conductive paste composition.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina board 2 Printing and baking pattern of conductive paste composition 3 Resistance measuring device by 4-terminal method

Claims (2)

[Claims] 1. A conductive paste composition for a terminal electrode of a chip resistor in which a conductive component composed of a metal powder and an inorganic binder are dispersed in a vehicle, comprising: Ag alone, a mixture of Ag and another noble metal powder, and an alloy. 50 to 87% by weight of at least one selected from the group consisting of: PbO and SiO ₂ as main components as inorganic binders;
The glass binder containing no Bi ₂ O _3, 3 to 10 wt%,
And a metal oxide, pyrochlor or boride selected from tin, iridium, rhodium, ruthenium and rhenium, alone or in an amount of 0.1 to 15% by weight;
A conductive paste composition for a terminal electrode of a chip resistor, comprising: 2. The conductive paste composition for a terminal electrode of a chip resistor according to claim 1, wherein the component of the glass binder further contains B ₂ O ₃ .