JPH02215006A - Conductive particle and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to conductive particles used in electrode materials and a method for producing the same.

Conventional technology Conventionally, conductive particles, resin, solvent, and a small amount of frit,
In some cases, conductive paints made of metal oxides and organometallic compounds are widely used as electrode materials for various parts. As the conductive particles, expensive noble metals such as silver, gold, platinum, and palladium are used.
In order to reduce the cost of electrode materials, consideration is being given to reducing the amount of precious metals used or replacing them with base metal materials.

Copper and nickel have been used for full-scale replacement with base metal materials, and silver-copper alloys have been used for partial replacement, but in both cases, by baking or leaving in the air,
Since oxides are formed and the conductivity decreases, baking requires controlling the atmosphere and coating the electrode surface, complicating the manufacturing process.

In addition, attempts have been made to reduce the amount of precious metals used by using base metals as a base material and coating them with precious metals (for example, Japanese Patent Publication No. 46-40593, Japanese Patent Application Laid-Open No. 60-1999).
-100679). When a conductive paint using such noble metal coated powder is applied to a ceramic material and baked in air to form an electrode, the coated noble metal is not sintered in a continuous state and the base material is exposed. In addition, the conductivity decreases due to the generation of oxides.

In order to prevent this, the coating thickness of the precious metal must be increased, and the cost reduction effect is suppressed. Also,
In order to control the exposure of the base material, improvements have been made to plating methods for noble metal coating (for example, Japanese Patent Publication No. 61-22
028 Publication).

However, with respect to powders made of base metal powder coated with noble metals, it is basically impossible to completely suppress heat diffusion from the base material to the coated metal when baking at high temperatures, so exposure of the base material is suppressed. In order to do this, the thickness of the coating metal must be increased, and a significant cost reduction cannot be expected. In addition, silicon oxide, aluminum oxide, zirconium oxide,
The use of oxides such as titanium dioxide or barium titanate is also being considered (for example,
No. 2029, No. 48586).

However, when using oxides, thermal diffusion into the noble metal layer is suppressed compared to base metals, but since all of the above oxides are insulators, in order to maintain conductivity as an electrode material, After all, the coating thickness must be increased, and it is difficult to significantly reduce material costs.

Problems to be Solved by the Invention Regarding the conductive particles having the above-mentioned structure, in which the base material is a base metal or an oxide and is coated with a noble metal, baking at high temperatures prevents the base material from being exposed or the conductivity from decreasing due to processing. In order to achieve this, the thickness of the coating must be increased. Therefore, the amount of precious metal used increases, and the cost of the conductive particles cannot be significantly reduced. There is also the problem of increased manufacturing costs due to high-temperature sintering.

The present invention has been made in view of these points, and an object of the present invention is to provide conductive particles at low cost that have excellent conductivity and thermal stability and can be sintered at low temperatures.

Means for Solving the Problems In order to solve the above problems, the conductive particles of the present invention have a conductive composite oxide particle surface coated with 10 to 6.0% by weight of phosphorus or 0.1 to 2.5% by weight. It has a structure in which it is coated with a noble metal containing % by weight of boron.

Here, as the conductive composite oxide, especially 1, a, -1
srxCoO, (o, 1≦x≦o, a), Pr1.5
rxCoo3 (0.2≦x≦0.8), Nd1z8
rxCo05≦x≦0.7).

Lal zBaxCoo3 (0.1≦I≦0゜5), P
rl zBazcoQ.

(0.2≦x≦0.6), or L! L2 zs
rxCuO4 (Q, 1≦x≦0.6), La2,
BaxCub4 (0.01≦x≦0.6), which has one or two types of answer system composition, and YB
a2 (ju507 series, Bi Ca Sr Cu 20
! , S-based compositions are preferred.

In addition, in order to reduce manufacturing costs, it is necessary to reduce the amount of precious metals used, but as a result, thermal diffusion of the base material during baking becomes more intense. It is desirable to reduce the Here, when baking a conductive paint containing glass frit, it is expected that phosphorus or boron will promote sintering. Therefore, the present invention aims to lower the sintering temperature, suppress thermal diffusion of the base material, and reduce the amount of precious metal used by containing phosphorus or boron in the coated noble metal.

Effect of the present invention With the above-described structure, since the base substance is an oxide, diffusion into the coated precious metal layer is suppressed, and even if the coating thickness is reduced, baking at low temperatures can be treated, so that the base substance is can be suppressed from being exposed on the particle surface.

Further, since the base material is conductive, even if the base material is exposed, a decrease in conductivity can be suppressed.

The reason why a composite oxide is used as the base material is that a composite oxide is superior in terms of conductivity and cost compared to an oxide containing a single metal element. In particular, La
1 zsrxICo03 (o, 1≦x≦o, s).

pr 1-x Sr z coo 5 (0.2≦x≦
o, a) jNbi −xSrxCoO3 (0.5≦x≦
o, 7), La1 zBaxCod, (0.1≦x
≦o, s).

One having a solid solution composition of one or more of Pr1, BalCoO3 (0.2≦x≦0.6), or La2 zsrzcu04 (0.1≦x≦
o, s) jLa2-xHaxCu04 (0.01
≦x≦o, s) +7)5? )+7) 111t or those having two types of solid solution compositions, and furthermore YBa2C
u3O7 system or BiCaSrCu2O5.5rCu2
All those having a composition of the 055 series have excellent conductivity, and high conductivity can be obtained even if the noble metal coating is thin, so it is possible to significantly reduce the cost of conductive particles.

In addition, there are various methods for coating precious metals on substrate materials, such as electroplating, electroless plating, thermal decomposition, and vapor deposition, but electroless plating is the most superior in terms of equipment scale and mass productivity. This makes it possible to produce noble metal-coated powder at low cost.

Furthermore, by containing phosphorus or boron in the coating noble metal, the sinterability of the glass frit can be improved and the sintering temperature can be lowered.

This makes it possible to better reduce the spread of heat to the ceramic component, even if the substrate material is exposed.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example 1) Starting with L&20s Sr co31 CO50a, the required amount of each was weighed, and 1% was added in ethanol.
The mixture was mixed for 2 hours, dried and then calcined at 900'C. After pulverizing this calcined powder, it was fired at 1100°C for 2 hours to produce LaO,
A powder having a composition of 5SrO, 5Coo 5 was obtained.

This was then immersed in a neutral type activation solution containing palladium ions for activation treatment, and the resulting powder was subjected to the following three plating treatments. (1) Palladium chloride is dissolved in ethylenediamine, thiodiglycolic acid and sodium hypophosphite are added thereto, and the activated powder is added to the palladium plating solution whose pH is adjusted to 90 with hydrochloric acid and stirred. Palladium-coated powder obtained by plating palladium, washing with water by decantation, and drying. therefore,
Contains phosphorus in palladium. (2) Sodium borohydride and the above activated powder are added to a plating solution consisting of palladium chloride, ethylenediamine, and sodium hydroxide and stirred to plate palladium, then washed with water and dried in the same manner as in (1). palladium-coated powder obtained by Therefore, palladium contains boron. (3) Add hydrazine and the activated powder to a plating solution consisting of palladium chloride, ammonia, and hydrochloric acid, stir, plate with palladium, and then wash with water and dry in the same manner as in (1). palladium coated powder. Therefore, neither phosphorus nor boron is contained in palladium. As mentioned above, the Lao, 5 Sr of these powders
O,50oos Tohara') '7 A 0TLIk
The ratio was 80/20.

Separately, magnesium fist lead niobate (Pb (Mg%Nb%)
)0. ], 10 parts by weight of dielectric powder, 8 parts by weight of polyvinyl butyral resin, 4 parts by weight of dibutyl phthalate.
Parts by weight, 40 parts by weight of trichloroethane, 25 parts by weight of butyl acetate
Parts by weight were added and kneaded in a ball mill for 20 hours. The dielectric slurry thus obtained was subjected to a reverse roll method for 4
A sheet was formed to a thickness of 0 μm. Next, a commercially available palladium paste is printed in a desired pattern on the dielectric sheet, and this is laminated to create a laminate in which electrodes and dielectrics are alternately laminated, and then cut into desired dimensions. It was fired at 1100'C for 12 hours. Palladium-coated powder and glass frit prepared by each method were placed on the side surface of the sintered body thus obtained where the electrode was exposed.
An electrode paste consisting of ethyl cellulose and terpineol was applied and baked at 760°C. The capacitance values of the multilayer chip capacitors obtained in this way agree well with the design values calculated from the dielectric constant (ε=12,000) of the dielectric material, and the capacitance values of the multilayer chip capacitors obtained by this method are in good agreement with the design values calculated from the dielectric constant (ε = 12,000).
The practicality of the electrode using o, 5 Sr o, 5 Coo 5 was confirmed.

Next, when these multilayer chip capacitors were soldered to a printed wiring board and an external electrode adhesion test was performed, the force was 1.2 kg for the coated powder (1) and 11 kg for the coated powder (2). However, in the case of coated powder (3), when a force of oak kg was applied, the terminal electrode did not peel off. Sara K, the above coated powder (1)
The results of studies conducted under various conditions regarding the plating bath (2) are shown in Tables 1 and 2 below.

Table 1 Table 2 These results are due to the inclusion of phosphorus or boron in the noble metal coating, which promotes sintering at the interface between the electrode and the dielectric and improves the adhesion strength. considered,
This confirmed the superiority of conductive particles containing phosphorus or boron in the coated noble metal. Regarding the contents of phosphorus and boron, as a result of examining various plating conditions, good results could only be obtained with the contents in the ranges shown in the table above.

(Example 2) La2 o, I Pr6011 * Nd20S e
""3jSr"3 La1 zs by the same method as above (Example 1) using #Co3O4 as a starting material
rxCo03, Pr1-1srzco03゜Nd1
zsr, CoO3, La1 zBazcoo3. Prl
Powders with different X of each composition system of zBaxCoQ3 were created. Using these powders as a base material, plating treatment was performed in the same manner as the coating powder (1) of (Example 1),
A palladium-coated powder with a weight ratio of base material to palladium of 75/25 was obtained.

Using this powder, a conductive paste was prepared in the same manner as in Example 1, and the conductive paste was baked onto an alumina substrate and the electrical resistance value was measured. The results of converting this measured value into units of Ω·cm are shown in Table 3 below.

From the results in Table 3, it can be seen that the electrical resistance value of the baked thick film is not determined only by the coated palladium, but is influenced by the composition of the base material. In order to obtain excellent conductivity, the composition of the base material must be
La1 zsrICjo05 (0.1≦x≦0.8)
, Prl zsrxOo03 (0.2≦x≦0.8)
.

Nd1zsrxCoo, ≦x≦0.7), La1
zBaxCo05 (0.1≦x≦0.6), Pr
1 zBaxCoo3 (0.2≦x≦0.5) is suitable.

Next, palladium plating, pasting, and baking were performed in the same manner as above using an oxide that is a composite of the above materials as a base material, and the electrical resistance value of the obtained thick film was measured. As a result, the following results were obtained. As shown in Table 4, excellent conductivity was confirmed.

(Hereinafter referred to as gold and white) <Table 4> (Example 3) La20. , 5r (j03. Using BaO05 and CuO as starting materials, weigh the required amount of each, mix in ethanol for 12 hours, dry and sinter at 900°C for 12 hours, then heat treat in oxygen at 600'C. La2-1srzc
Powders having compositions in which X of uo4°La2 zBazcu04 was variously changed were obtained.

Then, the above powder is immersed in an activation solution containing stannous chloride for activation treatment, and separately, sodium cyanosilver, sodium cyanide, and sodium borohydride are dissolved in pure water, and the pH is adjusted with sodium hydroxide. 13.0, and a silver plating bath was prepared.

The previously activated powder was placed in this plating bath, and the powder surface was plated with silver by stirring.

After this plating treatment, it was washed with water using the decanty silane method and dried to obtain a silver-coated powder. The powder thus obtained had a weight ratio of base material to silver of ao/20.

A conductive paste was prepared using the above silver powder in the same manner as in Example 1, baked on an aluminum substrate at a temperature of 850° C., and the electrical resistance was measured. This measured value is Ω・c
The results of unit conversion to m are shown in Table 6 below.

(Left below) From the results in Table 6, it is clear that in order to obtain excellent conductivity, the composition of the base material should be La2 zsrxOu04 (0.
1≦x≦0.5), LIL2-1BaICub4
It can be seen that (0.01≦x≦0.6) is suitable.

Next, using an oxide that is a composite of the above materials as a base material,
Silver plating, pasting, and baking were performed in the same manner as above, and the electrical resistance of the resulting thick film was measured, and as shown in Table 6 below, excellent conductivity was confirmed. did.

<Table 6> (Example 4) Y2O2, BaCO3, Cub, Bi2O3, CaC
Using O3 and F3rO05 as starting materials, weigh the required amount of each, mix in ethanol for 12 hours, and after drying
'C for 12 hours and then heat treated in oxygen at 6oooC to produce YBa2Cu2O7 and BiCaSrCu2O.
5.5rCu205. A powder with a composition of s was obtained.

Then, the above powder is put into an activation solution containing neutral type palladium ions for activation treatment, and a separate cyanide gold (
1) A plating solution consisting of potassium, potassium cyanide, and potassium hydride was prepared, and sodium borohydride and activated powder were added to this plating solution and stirred to plate the powder surface with gold. After this plating treatment, it was washed with water by a decantation method and dried to obtain a gold-coated powder. The powder thus obtained had a weight ratio of base material to gold of 76/25.

Using the above gold-coated powder, a conductive paste was prepared in the same manner as in (Example 1), and was placed on an alumina substrate with a width of 850'.
It was baked at C and the electrical resistance value was measured. Here, when the base material is YBa2Cu2O7, the electrical resistance value is 6×10
Ω cm, BiCaSrCu2O5.5rCu20
! In the case of L5, it was 8×10 Ω·CIl+, confirming excellent conductivity.

In addition to this example, it goes without saying that conductive composite oxide particles coated with noble metals have practical applications as electrodes for chip resistors, chip inductors, varistors, piezoelectric elements, and even ceramic multilayer wiring boards. .

Since all of the composite oxides targeted by the present invention usually have oxygen vacancies, the composition of oxygen is not particularly defined. Furthermore, in order to control the chemical stability or electrical properties of the base material, metal elements or anionic elements other than the main component elements may be added to the base material. Furthermore, the composite oxide powder used in the above examples was
Although the particles had particle diameters in the range of 01 to S and O8 types, the particle diameter and particle shape are not particularly defined.

On the other hand, in addition to the above embodiments, platinum, rhodium, iridium, ruthenium, and alloys thereof, which can be plated electrolessly, can be used as the noble metal to be coated. In addition, when coating with noble metals, it is also possible to coat the particle surface of the conductive composite oxide in multiple layers with two or more of the above-mentioned noble metals. o~e, o weight phosphorus or 0.1~2.6
It is an oxide coated with a noble metal containing % by weight of boron, and an electroless plating method is used as the noble metal coating method. Therefore, the present invention allows conductive particles with excellent conductivity and thermal and chemical stability to be produced at low cost, and is of great practical value.

Claims (1)

[Scope of Claims] (1) The particle surface of the conductive composite oxide is 1.0 to 6.0
1. Conductive particles coated with a noble metal containing phosphorus in an amount of 0.1% to 2.5% by weight or boron in an amount of 0.1 to 2.5% by weight. (2) The conductive composite oxide is La_1_-_xSr_x
CoO_3 (0.1≦x≦0.8), Pr_1_-_x
Sr_xCoO_3 (0.2≦x≦0.8), Nd_1
____xSr_xCoO_3 (0.3≦x≦0.7),
La_1_−_xBa_xCoO_3(0.1≦x≦0
．． 5), Pr_1_−_xBa_xCoO_3(0.2
2. The conductive particles according to claim 1, having a solid solution composition of one or more of the following: ≦x≦0.5. (3) The conductive composite oxide is La_2_-_xSr_x
CuO_4 (0.1≦x≦0.8), La_2_−_x
The conductive particles according to claim 1, having a solid solution composition of one or two of BaCuO_4 (0.01≦x≦0.5). (4) The conductive composite oxide is YBa_2Cu_3O_7
2. The conductive particles according to claim 1, having a composition of: (6) The conductive composite oxide is BiCaSrCu_2O_
5__. Claim 1 characterized by having a composition of __5 system.
Conductive particles as described. (6) A method for producing conductive particles, which comprises coating the surface of conductive composite oxide particles with a noble metal by electroless plating in which a plating solution contains phosphorus or boron. (7) An electrode for electronic components, characterized in that the conductive particles according to claim 1 are used.