JPH06318503A - Conductive composition for ceramic semiconductor - Google Patents

Abstract

PURPOSE:To provide a conductive composition for a ceramic semiconductor in which its resistance can be reduced and at the same time the film strength of an electrode can be increased, by reducing a material cost, increasing a working temperature, avoiding a bad influence on a ceramic semiconductor and at the same time further improving ohmic contact. CONSTITUTION:In the case of constituting a conductive composition which is made of an Ag powder and at least one of base metals such Zn and Zn-Sb, a very fine Ag powder is added to all Ag components in the range of 20 to 80 parts by weight, where the particle diameter of the Ag powder is 2 to 10mum and the particle diameter of the very fine Ag power is 0.1 to 0.5mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition applied to a porcelain semiconductor having a positive resistance temperature characteristic, and more specifically, it reduces the material cost, improves the operating temperature, and adversely affects the porcelain semiconductor. The present invention relates to a structure of a conductive composition that can further improve ohmic contact while avoiding it and can improve the film strength of an electrode.

[0002]

2. Description of the Related Art A barium titanate-based porcelain semiconductor having a positive resistance-temperature characteristic whose electric resistance value changes depending on temperature must be provided with an electrode capable of obtaining a low resistance ohmic contact without rectification. As a conductive composition used for such an electrode, an In-Ga alloy, electroless plating of Ni, a mixture of a metal having an ohmic property and Ag, or an electrode film forming method by sputtering has been conventionally used. There is.

Although the above-mentioned In-Ga alloy can obtain a substantially ideal ohmic contact, the material cost increases due to the use of expensive Ga, and the ohmic property is easily lost at a temperature of about 200 ° C. There is a drawback that.
Further, the Ni plating has a problem that the characteristics of the porcelain semiconductor are easily deteriorated during the plating process, and the resistance is largely deteriorated with time.

On the other hand, the above ohmic metal and A
As a kind of mixture with g, conventionally, Ag and Zn,
A mixture of Zn-Sb, Sn, Al and the like is added at 300 to 700 ° C.
An electrode formed by baking is proposed (see, for example, Japanese Patent Publication No. 49-18158 and Japanese Patent Publication No. 55-26561). According to this electrode, since a relatively inexpensive base metal such as Zn is used, the material cost can be reduced as compared with the above In—Ga alloy. Moreover, since the baking temperature of the electrode is high, the ohmic property is not lost even when the electrode is used at 200 ° C. or higher, so that the ohmic property, environment resistance and productivity can be improved. Moreover, since no plating treatment is performed, it is possible to avoid adverse effects on the porcelain semiconductor.

[0005]

However, when the conventional mixture of Ag and a base metal such as Zn or Zn-Sb is applied as an electrode to a porcelain semiconductor having a lower resistance, it is compared with the In-Ga alloy. There is a problem that the ohmic contact is insufficient and the resistance value is high. Further, since the above conventional composition is fired at a low temperature, there is a problem that the film strength of the electrode is low.

The present invention has been made in view of the above conventional circumstances, and when employing a mixture of Ag and a base metal such as Zn or Zn-Sb, ohmic contact can be improved to further reduce the resistance value. Moreover, it is an object of the present invention to provide a conductive composition for a porcelain semiconductor which can improve the film strength of an electrode.

[0007]

Means for Solving the Problems The inventors of the present invention have studied to improve the ohmic property and film strength of a mixture of Ag and a base metal.
I focused on. That is, since the conventional Ag powder has a relatively small particle size, it is difficult to sinter when firing at a low temperature, which affects ohmic properties and film strength. Therefore, it was conceived that contact resistance can be reduced and film strength can be improved by replacing a part of the Ag component with a fine Ag powder having a high sinterability at low temperature firing. It was done.

Therefore, according to the present invention, Ag powder and Zn, Zn-
In a conductive composition for a porcelain semiconductor, which is composed of at least one base metal such as Sb, fine Ag based on all Ag components
It is characterized in that the powder was added in the range of 20 to 80 parts by weight.

Here, the above-mentioned Ag powder and fine Ag powder specifically refer to, for example, Ag powder having a particle size of 2 to 10 μm, and the fine Ag powder having a particle size of 0.1 to 0.
5 μm. Here, Ag powder and fine Ag
The particle size of the powder is limited to the above range because ohmic contact cannot be maintained outside this range.

Further, the conductive composition comprises 50 to 95 parts by weight of the Ag component, 5 to 50 parts by weight of a base metal such as Zn and Zn-Sb, and 2 to 20 parts by weight of a low melting point glass frit. Is preferred. Here, the Ag component is 50-
The reason why the amount is 15 parts by weight is that if the amount is less than 50 parts by weight, the conductivity of the film is lowered, and if it exceeds 95 parts by weight, ohmic contact cannot be maintained. Further, the reason why the base metal such as Zn and Zn-Sb is set to 5 to 50 parts by weight is that if less than 5 parts by weight,
A rectifying property such as a Schottky barrier is developed between the porcelain semiconductor and the electrode, and the resistance value remarkably increases. On the other hand, when it exceeds 50 parts by weight, the base metal is oxidized and the amount of the Ag component is increased. The film resistance increases because the film is not scraped. Further, a low melting point glass frit is added to 2 to 2
The reason why the amount is 0 parts by weight is that if the amount is less than 2 parts by weight, the electrode cannot be sufficiently baked, resulting in an increase in contact resistance and a decrease in film strength, while if the amount exceeds 20 parts by weight, the conductivity is lowered.

[0011]

According to the conductive composition for a porcelain semiconductor of the present invention, since the fine Ag powder is added in the range of 20 to 80 parts by weight with respect to the total Ag component, it is possible to improve the sintering during low temperature firing, and thus The ohmic contact can be improved to further reduce the resistance value, the film strength of the electrode can be improved, and the reliability of quality can be improved. As a result, while reducing the material cost, improving the operating temperature, and avoiding adverse effects on the porcelain semiconductor, the electrical characteristics substantially equivalent to those of the In-Ga alloy can be obtained.

[0012]

EXAMPLES Examples of the present invention will be described below. In this example, an experiment conducted to confirm the effect of the conductive composition applied to the porcelain semiconductor of the present invention will be described.

[0013]

[Table 1]

First, the sample used in this experiment will be described. In this experiment, as shown in Table 1, a Ag component formed by mixing a conventionally used Ag powder and a predetermined amount of fine Ag powder, which is a feature of the present invention, with Zn or Zn ₃
And _{Sb 2, PbO-Si O 2} -B 2 O 3 as a binder
A low fusing-point glass frit was prepared so that the total amount thereof was about 80 parts by weight. Further, 20 parts by weight of a resin component as a binder and a solvent were added and mixed, and then dispersed to prepare an electrode paste.

Next, as shown in FIG. 1, a porcelain semiconductor 1 containing barium titanate as a main component is used. After printing and drying the electrode paste on both main surfaces of the porcelain semiconductor 1,
The electrode 2 was formed by baking in a tunnel furnace having a top temperature of 420 ° C. On the surface of the electrode 2 of the sample thus obtained, a paste comprising 80 parts by weight of Ag powder and 20 parts by weight of a resin component as a binder and a solvent was printed and dried to form the second layer electrode 3. Then, the contact resistance value Ω generated between the electrode of each sample in which only the electrode 2 was formed and each sample in which the second layer electrode 3 was formed and the porcelain semiconductor was measured by the 4-terminal method. In addition, it was confirmed by measuring resistance in the forward and reverse directions in advance that there was no rectifying property.

Sample No. Samples 5 and 10 are made of only fine Ag powder, and samples 1 and 6 are made of conventional Ag powder. In addition, sample No. All of Nos. 11 to 14 are particles of Ag powder or fine Ag which are too large or too small. The same measurement was performed for each of these samples.

[0017]

[Table 2]

Table 2 shows the measurement results. First in the table
Column A shows the resistance value of each sample in which only the electrode 2 is formed,
The second column B shows the resistance value of each sample in which the above-mentioned second layer electrode 3 is formed.

In Table 2, in the case of the conventional sample Nos. 1 and 6 using only Ag powder, the contact resistance value is high.
Further, in the case of Sample Nos. 5 and 10 using only the fine Ag powder, the viscosity of the paste increases with the increase of the oil absorption amount, and thus the printability deteriorates, and thus the resistance value increases. The contact resistance value of the In-Ga alloy electrode generally used as the ohmic electrode was 0.467 Ω.

On the other hand, in the case of Sample Nos. 2 to 4 and Nos. 7 to 9 of this example, in which the ratio of the fine Ag powder to the total Ag component was within the range of 20 to 80 parts by weight. Sample No. 1 also has a low contact resistance value and has improved ohmic properties. Thus, it is understood that the resistance value can be reduced by setting the addition amount of the fine Ag powder to 20 to 80 parts by weight with respect to the total Ag component. The composition of the glass frit can be used in the present invention, PbO-Si O ₂
Not limited to -B ₂ O ₃ system, similar effects can be obtained if抵融point glass.

[0021]

As described above, according to the conductive composition for a porcelain semiconductor according to the present invention, since the fine Ag powder is added in the range of 20 to 80 parts by weight to the total Ag component, the material cost can be reduced. The effect of improving ohmic contact to reduce the resistance value and improving the film strength of the electrode while improving the operating temperature and avoiding adverse effects on the porcelain semiconductor is provided.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an experiment conducted to confirm the effect of a conductive composition for a porcelain semiconductor according to an example of the present invention.

[Explanation of symbols]

 1 Porcelain semiconductor 2 Ohmic electrode (conductive composition)

Claims (3)

[Claims] 1. A conductive composition for a porcelain semiconductor, which comprises Ag powder and at least one of base metals such as Zn and Zn—Sb, and the fine Ag powder is contained in an amount of 20 to 20 with respect to all Ag components.
A conductive composition for a porcelain semiconductor, which is added in a range of 80 parts by weight. 2. The porcelain semiconductor according to claim 1, wherein the particle size of the Ag powder is 2 to 10 μm, and the particle size of the fine Ag powder is 0.1 to 0.5 μm. Conductive composition. 3. The Ag component according to claim 1 or 2,
0 to 95 parts by weight, 5 to 5 base metals such as Zn and Zn-Sb
A conductive composition for a porcelain semiconductor, which comprises 0 parts by weight and 2 to 20 parts by weight of a low-melting-point glass frit.