JPH11251105A - Thick-film resistance paste and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thick-film resistance paste, having high EDS characteristic (high withstand voltage pulse characteristic) and which does not contain such harmful substance as Pd, Cd, Ni, etc., for obtaining a ceramic circuit board having superior performance. SOLUTION: A film resistance paste is prepared by adding an organic vehicle, a solvent, and a dispersant to a mixture prepared by mixing raw material powder composed of glass powder and conductive material powder with the organic vehicle. The mixture is prepared for satisfying the relation, 5.5A<=B<= 10.0A (where A represents the mean specific surface area (Am<2> /g) of the raw material powder, when the minor-axis diameter of the powder is less than or equal to 5μm and the volumetric ratio (%) of the vehicle to the raw material powder is B). At the manufacturing of the paste, the raw material powder is dispersed in the organic vehicle by forcibly passing the raw material mixture through a clearances of less than or equal to 5μm in width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film resistor paste for a ceramic circuit board having an external resistor and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a ceramic circuit board used for an integrated circuit, in addition to a built-in resistor provided between layers of a multilayer circuit board, a circuit comprising a conductor pattern and an external resistor is formed on the surface of the ceramic board. It contributes to higher performance and lower cost of ceramic circuit boards.

When a thick-film resistor is formed on the surface of a ceramic substrate, a paste obtained by adding a conductive substance to glass powder and using an organic vehicle is printed on the substrate surface and sintered to form a resistor. At this time, for the purpose of protecting the resistor and improving the weather resistance, printing is performed so that the resistor is covered with a glass-based material,
Overcoating is also performed by firing.

One of the important characteristics of a thick-film resistor is a high-voltage pulse resistance (ESD characteristic). Normally, EDS characteristics deteriorate with a resistance of 10 kΩ / □ or more. The reason is as follows. The conductivity of a thick-film resistor consists of a conductive material formed in the glass and a thin film of glass between the conductive materials, but when a high voltage is applied to the thick-film resistor, the fine conductive paths are broken. And the resistance value changes. As the resistance becomes higher, the amount of the conductive material decreases, and conduction by a thin glass film becomes more dominant. Conventionally, the following measures have been taken to solve such a phenomenon.

(1) Bi ₂ Ru ₂ O ₇ , P having a large resistivity
Use b ₂ Ru ₂ O ₆ powder and increase the amount of conductive material. However, glass containing Pb is used to prevent decomposition. (2) Using Pb-containing low-melting glass, a thin film is formed between conductive particles during firing.

(3) Use extremely fine glass powder and conductive particles to increase the number of conductive paths. (JP-A-8-2
However, (1) and (2) show that P is a harmful substance in raw materials.
b) is not preferred, and (3) was difficult to disperse.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides an ES
An object of the present invention is to provide a thick film resistor paste having good D characteristics and not containing harmful substances such as Pb, Cd, and Ni, and obtaining a ceramic circuit board having excellent performance.

[0008]

According to the present invention, there is provided a thick film resistor obtained by adding an organic vehicle, a solvent and a dispersing agent to a mixture obtained by mixing a raw material powder composed of a glass powder and a conductive substance powder with an organic vehicle. In the paste, the raw material powder has a minor axis particle size of 5 μm or less and an average specific surface area of Am ² /
g, the volume ratio of the organic vehicle to the raw material powder is B
%, Wherein a mixture having a relationship of 5.5 A ≦ B ≦ 10.0 A is used.

In the above, if B is less than 5.5 A, the amount of the vehicle is too small to adhere the powder to the roller, and if it exceeds 10.0 A, the amount of the vehicle is large. Powder cannot be dispersed, ED
The effect on the S characteristic is not so much exhibited. The viscosity of the organic vehicle is suitably from 10 pa · s to 300 pa · s. If the viscosity is less than 10 pa · s, there is no adhesive force, and it becomes difficult to attach the powder to the roller. Also, 300Pa.
When s exceeds s, the powder cannot be uniformly wetted with the vehicle, so that it is necessary to dilute the powder with a volatile solvent (for example, toluene, ethanol or the like).

[0010] Among powder materials, glass powder is CaO-
Al ₂ O ₃ —SiO ₂ —B ₂ O ₃ , Na ₂ O—SiO ₂ —B ₂ O
_3. Further, a mixed glass containing no Pb, Cd, or Ni is used. RuO ₂ is used as the conductive material. As the organic vehicle, ethyl cellulose and terpineol, butyral resin and terpineol, and the like are used.

[0011] The present invention also provides a method comprising: forcing a mixture of a powder material and an organic vehicle through a gap of 5 μm or less;
In the step of dispersing the raw material powder material in the organic vehicle, when the average specific surface area of the raw material powder is Am ² / g and the volume ratio of the organic vehicle is B%, 5.5A ≦ B ≦ 10.
A method for producing a thick-film resistance paste, comprising a step of adding and kneading a mixture having a relationship of 0 A with an organic vehicle, a solvent and a dispersant. First, the mixture having the relationship of A and B is forcibly passed through a gap of 5 μm or less, so that the glass and the conductive material can be uniformly dispersed.

A gap of 5 μm or less can be obtained, for example, by arranging two parallel rollers at an interval of 5 μm. By forcing the material through this gap, a diameter of 5
Crush or crush powder exceeding μm to a size of 5 μm or less. In this case, the major axis of the powder may exceed 5 μm, but it is appropriate that the major axis is twice or less the minor axis. If the gap exceeds 5 μm, no force is applied to the powder, so that the powder cannot be sufficiently dispersed. The material dispersed through the gap is kneaded by adding an organic vehicle and a solvent in order to form a paste that can be printed, so that a thick film resistance paste is obtained with an appropriate viscosity.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention and comparative examples will be described. The following three types of glass powder were prepared.

[0014]

[Table 1]

The following two types of vehicles were prepared. X: Ethyl cellulose, Terpionell Y: Butyral resin, Terpionel + butyl carbitol acetate RuO ₂ was used as the conductive substance.

After these materials are uniformly mixed in the composition shown in Table 2, additional organic vehicles, solvents and dispersants (Homogenol L-
95 ｛Product name: Kao Corporation｝)
A thick film resistor paste was prepared. After printing and firing the pattern of the resistance electrode part on a low-temperature firing ceramic substrate,
A thick film resistor was formed on a ceramic substrate. Table 2 also shows the sheet resistance (kΩ), 1.5 kV, ESD at 5 pulses, and the coefficient of the obtained resistor.

[0017]

[Table 2]

[0018]

[Table 3]

As shown in the above table, Examples 1 to 20 of the present invention have excellent EDS characteristics of 1.0% or less, and Comparative Examples 21 to 22 define the relational expressions in the present invention. Is not satisfied, and the EDS exceeds 1.0% and is poor. Also, Comparative Example 23 does not satisfy the relational expression in the present invention, and it is difficult to prepare a paste.

[0020]

According to the present invention, a thick film resistor paste having excellent ESD characteristics can be provided, and a ceramic circuit board having excellent performance can be obtained. This paste can be provided without containing harmful substances such as Pd, Cd, and Ni in the raw material powder, and is effective in maintaining a good use environment of the product.

Claims (6)

[Claims] 1. A thick-film resistance paste obtained by further adding an organic vehicle, a solvent and a dispersant to a mixture obtained by mixing a raw material powder composed of a glass powder and a conductive substance powder with an organic vehicle. When the axial particle size is 5 μm or less, the average specific surface area is Am ² / g, and the volume ratio of the organic vehicle to the raw material powder is B%, 5.5 A ≦ B
A thick film resistor paste using a mixture having a relationship of ≦ 10.0 A. 2. The thick film resistor paste according to claim 1, wherein said raw material powder material does not contain Pb, Cd, and Ni. 3. The method according to claim 1, wherein said conductive material is RuO _2.
The thick film resistor paste as described. 4. In the step of forcibly passing a mixture of a powder material and an organic vehicle through a gap of 5 μm or less to disperse the raw material powder in the organic vehicle, the average specific surface area of the raw material powder is Am ² / g; When the volume ratio of the organic vehicle is B%, a mixture having a relationship of 5.5A ≦ B ≦ 10.0A is formed, and a process of adding and kneading an organic vehicle, a solvent, and a dispersant is further included. Manufacturing method of thick film resistor paste. 5. The method according to claim 4, wherein the raw material powder does not contain Pb, Cd, and Ni. 6. The method according to claim 4, wherein said conductive material is RuO _2.
A method for producing the thick film resistor paste according to the above.