JPH0613203A - Manufacture of semiconductor ceramic element - Google Patents

Abstract

PURPOSE:To abolish the barrier without fail further enabling the resistance to be lowered by impressing a specific pulse between an electrode and a semiconductor ceramic. CONSTITUTION:Both surfaces of semiconductor ceramic manufactured by baking a molded body at 1350 deg.C for two hours in atmosphere are printed in an electrode paste comprising Zn added Ag paste to form an ohmic electrode by baking e.g. at 800 deg.C for two hours. Next, the space between the electrode and the semiconductor ceramic is impressed with a pulse voltage exceeding 100V. When this impressed voltage is lowered down to the level not exceeding 100V, the barrier can not be abolished without fail thereby making it unable to gain the diminishing effect of the resistance value. On the other hand, although the upper limit of this impressed voltage fluctuates depending upon the characteristics of ceramic, it is recommemded that the pulse voltage not to break down the inner grain boundry barrier not exceeding e.g. 100kV as well as the impression time not to cause the breakdown due to thermal strain e.g. not exceeding 0.1sec are to be adopted. Through these procedures, the semiconductor ceramic element capable of abolishing the barrier in the interface between the semiconductor ceramic and the conductive electrode without fail also having the positive resistance temperature characteristics to make the lower resistance feasible can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor ceramic element having a positive resistance temperature characteristic, and in particular, it can surely remove a barrier at an interface between a semiconductor ceramic and a conductive electrode, and eventually a resistance can be reduced. Regarding the method that was made possible.

[0002]

2. Description of the Related Art Generally, a BaTiO ₃ type semiconductor ceramic element having a positive resistance temperature characteristic in which an electric resistance value changes with temperature has a characteristic in which the resistance value rapidly changes at a Curie point or higher. It is used in many fields as an overcurrent protection device for the above, or as a degaussing device for a CRT frame of a television. Such BaTi
In the O ₃ -based semiconductor ceramic element, the barrier existing at the interface between the semiconductor ceramic and the electrode is removed to reduce the specific resistance at room temperature. In order to remove this barrier, conventionally, for example, a method of adding a reducing metal such as Zn or Sn to Ag or the like employed in an ohmic electrode has been proposed.

[0003]

However, in the conventional method for manufacturing a semiconductor ceramic element in which a reducing metal is added to the above electrode to remove the barrier, the heat treatment condition for removing the barrier is extremely difficult, and the barrier remains. Therefore, there is a problem that it is difficult to reduce the resistance value as a result.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a semiconductor ceramic element which can surely remove the barrier by a simple method and can lower the resistance.

[0005]

Therefore, the present invention provides a method for manufacturing a semiconductor ceramic element having positive resistance temperature characteristics, which is obtained by forming a conductive electrode on a semiconductor porcelain, and provides 100 V between the electrode and the semiconductor porcelain. The feature is that the above pulse voltage is applied.

Here, the applied voltage is set to 100 V or more because if the voltage is set lower than this, the barrier cannot be removed reliably and the effect of reducing the resistance cannot be obtained. Also,
The upper limit of the applied voltage cannot be unconditionally determined because it changes depending on the characteristics of the ceramic.
If a pulse voltage exceeding 100 KV is applied, the grain boundary barrier inside the ceramic may be destroyed.
No more is preferred. Further, the length of the voltage application time is not particularly limited, but if it is longer than 0.1 seconds, the ceramic is likely to generate heat, and as a result, it may be destroyed by thermal strain. Is preferred.

[0007]

According to the method for manufacturing a semiconductor ceramic element of the present invention, a pulse voltage of 100 V or more is applied between the electrode and the semiconductor porcelain, so that the barrier formed at the interface between the semiconductor porcelain and the electrode is thereby prevented. Since it can be removed reliably by a simple method, the resistance value can be greatly reduced and the reliability of quality can be improved.

[0008]

EXAMPLES Examples of the present invention will be described below. In this example, a test conducted to manufacture the semiconductor ceramic device of the present invention and confirm the effect of the device thus obtained will be described. First, a method for manufacturing the semiconductor ceramic device of this embodiment will be described. As a raw material, BaC
O ₃ , CaCO ₃ , TiO ₂ , Y ₂ O ₃ , SiO ₂ , M
Using nCO ₃ , these are formulated to have the following composition. (Ba _0.876 Ca _0.12 Y _0.004 ) TiO ₃ +0.0008 Mn
+ 0.01SiO _{2 The} above raw materials are put in a polyethylene pot together with pure water and zirconia balls, pulverized and mixed for 5 hours, dried, and calcinated at 1100 ° C. for 2 hours.

Next, the calcined body is crushed to form a calcined powder, and the calcined powder is mixed with an organic binder to form a slurry. This slurry is pressed by a press to form a compact having a diameter of 10 mmφ and a thickness of 0.6 mmt.

The above-mentioned molded body is fired in the atmosphere at 1350 ° C. for 2 hours to obtain a semiconductor porcelain. Then, an electrode paste obtained by adding Zn to Ag paste is printed on both sides of this semiconductor porcelain and baked at 800 ° C. for 2 hours to form ohmic electrodes. As a result, the semiconductor ceramic device of this example is manufactured.

[0011]

[Table 1]

Next, the test of the semiconductor ceramic device obtained by the above method will be described. This test is shown in Table 1.
As shown in FIG.
Each sample was prepared by changing it in the range of mol%. A pulse voltage of 10 KV was applied to each sample, and the resistance value (specific resistance) and the temperature coefficient of resistance at room temperature before and after the application of the pulse were measured. The temperature coefficient of resistance was calculated by the following equation. Temperature coefficient of resistance = (2.303 / T2-T1) x 100 T1: Temperature at which resistance becomes 10 times room temperature resistance T2: Temperature at which resistance becomes 100 times room temperature resistance In addition, for comparison, In- Ga
An alloy was adopted as the electrode, and the same measurement was performed for this.

As is apparent from Table 1, the resistance value (specific resistance, the same applies hereinafter) is 50 to 17 Ω as the amount of Zn added increases.
Although it is as low as cm, it does not fall to the resistance value of the In-Ga electrode. On the other hand, when a pulse voltage is applied, the resistance value of all the samples is significantly reduced to 15 Ω · cm regardless of the amount of Zn added, and a value equivalent to that of the In-Ga electrode is obtained. From this, it can be seen that the barrier is surely removed. In addition, the temperature coefficient of resistance is equal to that before the pulse application even after the pulse application.

[0014]

[Table 2]

In this test, as shown in Table 2, room temperature resistance values were prepared when samples were prepared in which the amount of Zn added was 0 and the pulse voltage applied to each sample was changed in the range of 0 to 100 KV. And the temperature coefficient of resistance was measured.

As is clear from Table 2, the pulse voltage is
In each sample of 100V or less, the resistance value is 30Ω · cm and the barrier is not completely removed. In contrast, the applied voltage is 100V
In each of the above samples, the resistance value was reduced to 19 to 15 Ω · cm, and it is clear that a remarkable resistance reduction effect was obtained.

In the above embodiment, the case where Ag is used for the electrode has been described as an example, but according to the present invention, the same effect can be obtained when Pt, Pd, Cu is used as the electrode.

[0018]

As described above, according to the method for manufacturing a semiconductor ceramic element of the present invention, since a pulse voltage of 100 V or more is applied between the electrode and the semiconductor porcelain, the barrier can be reliably removed and the resistance value can be increased. There is an effect that can be significantly reduced.

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor ceramic element having positive resistance temperature characteristics, which comprises forming a conductive electrode on a semiconductor porcelain, wherein a pulse voltage of 100 V or more is applied between the electrode and the semiconductor porcelain. A method for manufacturing a semiconductor ceramic device characterized by the above. 2. The electrode according to claim 1, wherein the electrode is Pt,
A method of manufacturing a semiconductor ceramic element, characterized in that any one of Ag, Pd, and Cu is contained as a main component.