JPH06283314A - Voltage nonlinear resistance element - Google Patents

Abstract

PURPOSE:To provide a voltage nonlinear resistance element with such an inexpensive ohmic electrode that the electrode has excellent solder wettability and a strong strength of adhesion and stable electrical characteristics can be obtained without forming any potential barrier. CONSTITUTION:An ohmic electrode to be formed on the surface of a semiconductor ceramic in a coating state is composed of silver containing glass frit and at least one kind selected out of metallic tin and stannous oxide and the mixing amounts of the glass frit and metallic thin or stannous oxide against 100 pts. silver are respectively set at 1.5-6.0 pts. and 0.5-10.0 pts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistance element.

[0002]

2. Description of the Related Art Conventionally, in voltage non-linear resistance elements and thermistor elements based on semiconductor porcelain ceramics,
When electrodes of gold (Au), silver (Ag), copper (Cu), etc. are formed on the base material by baking or the like, a potential barrier is formed between the semiconductor porcelain and the electrode interface, and this potential Since the barrier itself is unstable to a high electric field or heat, it becomes an unstable element. For example, an element having such a potential barrier causes characteristic deterioration due to pulse or surge current, or deterioration due to soldering to electrodes.

Therefore, in order to improve these characteristic deteriorations,
Indium gallium (In-
By depositing a so-called ohmic electrode containing an alloy such as Ga) or a metal such as zinc (Zn), it is possible to form an electrode on the surface of a semiconductor porcelain without generating a potential barrier. The electric characteristics of the porcelain itself can be stably extracted.

[0004]

However, when the electrode is baked in the atmosphere of 500 to 600 ° C., A
In-Ga in g is oxidized, and the electrode formed by baking becomes very poor in soldering, which makes practical application difficult.

Therefore, a general Ag containing no In-Ga or the like is further coated on these electrodes to obtain solder wettability, which is practically used. However, in practice, two electrodes are provided on the element. Since the layers are printed, the first layer and the second layer may be misaligned, which not only causes a problem in appearance but also promotes variations in characteristics.

Further, since two layers are printed on the element, the process is laborious and the cost of the electrode material is high.
The voltage non-linear resistance element obtained in combination with the use of n-Ga becomes a very expensive element. Further, since the baking process must be performed at a low temperature, the weak adhesion strength to the semiconductor ceramics is also a drawback.

The present invention solves the above problems, has good solder wettability and adhesive strength, and has a voltage non-linear resistance element having an inexpensive ohmic electrode capable of obtaining stable electric characteristics without forming a potential barrier. The purpose is to provide.

[0008]

The voltage non-linear resistance element of the present invention is a voltage non-linear resistance element in which an ohmic electrode is formed on a semiconductor porcelain, wherein the ohmic electrode is silver and glass frit is made of metal tin or A baking electrode containing at least one kind of stannous oxide and baked in the air or in a neutral atmosphere, wherein metallic tin or an oxide is added to 100 parts of silver and 1.5 to 6.0 parts of glass frit. It is characterized by containing at least one kind of stannous in a range of 0.5 to 10.0 parts.

[0009]

The electrode having the above composition contains at least one of metallic tin and stannous oxide,
It becomes an ohmic electrode that does not have a potential barrier to the semiconductor porcelain, and the electrical characteristics of the semiconductor porcelain itself can be brought out as they are. Further, since it has no potential barrier, it is possible to obtain a voltage non-linear resistance element which is electrically stable and highly reliable without deterioration due to pulses.

Moreover, since it is not necessary to use an expensive In-Ga alloy as in the prior art for the electrode having the above composition,
The cost is lower than that of a conventional Ag ohmic electrode containing an In-Ga alloy.

When the electrode material is baked in a neutral atmosphere in order to obtain a baked electrode, the progress of oxidation of metallic tin on the electrode surface is suppressed, and good solder wettability is thereby obtained. Further, the electrode material containing stannous oxide has a relatively small progress of oxidation to stannic oxide even after baking treatment in the atmosphere, and sufficiently good solder wettability can be obtained within the above composition range.

In addition, since the electrode having the above-mentioned structure can obtain good ohmic electrode characteristics with only one electrode layer and can be well soldered, an electrode material such as an ohmic silver electrode containing a conventional In-Ga alloy is used. The two-layer printing is not required.

[0013]

EXAMPLES After printing an electrode material on a semiconductor porcelain according to the present invention and performing a baking process, the atmosphere is the kind of tin (metal tin or stannous oxide) contained in silver used as an electrode,
Depending on the content, the atmosphere or the neutral atmosphere may be used, and the neutral atmosphere is, for example, N ₂ 100%.

The baking temperature may be about 700 to 850 ° C. depending on the kind and content of tin (metal tin or stannous oxide) contained in the silver used as the electrode and the baking atmosphere.

Further, as the glass frit contained in silver, lead borosilicate can be mentioned, and the range of the amount of glass frit contained in 100 parts of silver is 1.5 to 6.0 parts because the content is This is because when the amount is less than 1.5 parts, sufficient electrode strength cannot be obtained, and when the content exceeds 6.0 parts, the solder wettability is deteriorated.

The amount of at least one of metallic tin or stannous oxide contained in silver and glass frit is set to 0.5 to 10.0 parts because the content is 0.5.
When the content is less than 1.0 part, stable and good ohmic properties cannot be obtained, and when the content exceeds 10.0 parts, the solder wettability is deteriorated.

Next, specific examples of the present invention will be described together with comparative examples.

Experimental Example 1 A semiconductor porcelain having SiTiO ₃ as a main component and having a surface or a grain boundary having a high resistance was prepared in advance. Separately from this,
Metal tin (Sn) to be contained as shown in Table 1 for a composition having a composition ratio of 100 parts of silver (Ag), 3 parts of glass frit (lead borosilicate) and 50 parts of organic vehicle as an electrode.
Electrode pastes having different amounts of metallic tin were prepared by variously changing the mixing ratio of the powders.

Then, each electrode paste is applied to the surface of the semiconductor porcelain in a thickness of 5 to 10 μm by an ordinary method, and then nitrogen (N
₂ ) After baking in a gas atmosphere at a temperature of 850 ° C,
Voltage non-linear resistance elements with different metal tin contents, so-called varistor elements (sample numbers 1 to 6) were obtained.

E ₁₀ (voltage value when a current of ₁₀ mA was applied), α (voltage non-linearity coefficient), pulse resistance, solder wettability, and electrode strength were measured as electrical characteristics of each obtained varistor element. Table 1 shows the measurement results.

Here, α = 1 / log (E ₁₀ / E ₁ ) is defined, and E ₁ is a voltage value when a current of ₁ mA is applied.

The pulse resistance was defined as the rate of change of the E ₁₀ value after applying a pulse voltage of 80 V for 10 cycles.

The solder wettability was measured by placing a ring solder having a diameter of φ2.2 on the electrode portion and allowing it to stand for 7 seconds on a hot plate having a temperature of 250 ° C., and measuring the extension of the solder after cooling.
It should be noted that in the measurement results, the circle marks show good solder wettability (solder extension 2.
5 mm or more), and the symbol X indicates poor solder wettability (solder extension is 2.5 mm or less).

Further, a lead wire having an electrode strength of φ0.5 and a length of 4 cm was soldered to the center of the electrode using the ring solder, and the tensile load when the electrode was peeled off was measured by a tensile loader. . In addition, in the measurement result, the mark ◯ is 3 kgf or more, and the mark Δ is less than 3 kgf.

For comparison, a conventional Ag electrode containing an In--Ga alloy was applied to the surface of the semiconductor porcelain, and a general Ag electrode was printed on it (two-layer electrode), and then the temperature was 580 ° C. in the atmosphere. Then, a baking process was performed to obtain a comparative element (Sample No. 7). The electrical characteristics of the obtained comparative element were E ₁₀
(Voltage value when a current of 10 mA is applied), α (voltage nonlinearity coefficient), pulse resistance, solder wettability, and electrode strength are measured under the same conditions as the varistor element of the present invention, and the measurement results are shown in a table. Shown in 1.

[0026]

[Table 1]

Experimental Example 2 The same procedure as in Experimental Example 1 was repeated except that the electrode paste was applied on the surface of the semiconductor porcelain and the temperature was 700 ° C. in the atmosphere. Different varistor elements (sample numbers 8 to 13) were obtained.

The electrical characteristics of each obtained varistor element were E ₁₀ (voltage value when a current of ₁₀ mA was applied), α (voltage nonlinear coefficient), pulse resistance, solder wettability, and electrode strength. The measurement was performed under the same conditions as in Experimental Example 1, and the measurement results are shown in Table 2.

In Table 2, the comparative element (Sample No. 7) and the measurement results of electrical characteristic values are also shown for reference.

[0030]

[Table 2]

As is clear from Tables 1 and 2, the content of metal tin (Sn) is 0.5 parts or more per 100 parts of silver (Ag), the pulse resistance is good, and the potential barrier is present. No ohmic varistor characteristics are obtained. This is at the same level as the varistor characteristic of the conventional ohmic silver electrode (containing Ag + In-Ga). Further, when the content of metallic tin is 10 parts or less, the solder wettability is good, and the product of the present invention can provide a voltage non-linear resistance element that can be sufficiently put into practical use with only one electrode.

If the content of metallic tin is less than 0.5 part, a potential barrier exists and pulse deterioration occurs, and if the content of metallic tin exceeds 10.0 parts, metallic tin is contained. Part of it is oxidized or the sintering of silver is delayed, so that the solder wettability is deteriorated.

Further, in the present invention, the atmosphere during the baking process of the electrode is either nitrogen (N ₂ ) gas atmosphere (neutral atmosphere) as in Experimental Example 1 or atmospheric air as in Experimental Example 2. However, the baking process can be performed at a temperature higher than the temperature at which the conventional ohmic silver electrode is baked, and an element having high electrode strength can be obtained.

Experimental Example 3 A semiconductor porcelain having SiTiO ₃ as a main component and having a surface or a crystal grain boundary having a high resistance was prepared in advance. Separately from this,
For a composition having a composition ratio of 100 parts of silver (Ag), 3 parts of glass frit (lead borosilicate) and 50 parts of organic vehicle as electrodes, stannous oxide (S) to be contained as shown in Table 3 is added.
(nO) powder was mixed in various proportions to prepare electrode pastes having different stannous oxide contents.

Then, each electrode paste is applied to the surface of the semiconductor porcelain in a thickness of 5 to 10 μm according to a conventional method, and then baked at a temperature of 800 ° C. in an N ₂ atmosphere so that the content of stannous metal varies. A voltage non-linear resistance element, a so-called varistor element (Sample Nos. 14 to 19) was obtained.

The electrical characteristics of each obtained varistor element were E ₁₀ (voltage value when a current of ₁₀ mA was applied), α (voltage non-linear coefficient), pulse resistance, solder wettability, and electrode strength. Measurement was performed under the same conditions as in Experimental Example 1, and the measurement results are shown in Table 3.

In Table 3, the comparative element (Sample No. 7) and the measurement results of electrical characteristic values are also shown for reference.

[0038]

[Table 3]

As is clear from Table 3, silver (Ag) 10
With respect to 0 part, the content of stannous oxide (SnO) is 0.5 part or more, the pulse resistance is good, and the ohmic varistor characteristic having no potential barrier can be obtained. Further, when the content of stannous oxide (SnO) is 10.0 parts or less, the solder wettability is also good, and the product of the present invention provides a voltage non-linear resistance element which can be practically used with only one electrode. You can do it.

Further, the baking temperature of the electrode can be made higher than the baking temperature of the conventional ohmic silver electrode, and an element having high electrode strength can be obtained.

Experimental Example 4 A semiconductor porcelain having SiTiO ₃ as a main component and having a surface or a crystal grain boundary having a high resistance was prepared in advance. Separately from this,
Metal tin (Sn) contained as shown in Table 4 with respect to a composition having a composition ratio of 100 parts of silver (Ag), 3 parts of glass frit (lead borosilicate) and 50 parts of organic vehicle as an electrode.
Electrode pastes having different amounts of metallic tin and stannous oxide were prepared by variously changing the mixing ratio of the metal stannous oxide (SnO) powder.

Then, each electrode paste was applied to the surface of the semiconductor porcelain in a thickness of 5 to 10 μm by a conventional method, and then baked at a temperature of 800 ° C. in an N ₂ atmosphere to obtain the contents of metallic tin and stannous metal. Various voltage non-linear resistance elements, so-called varistor elements (sample numbers 20 to 25) were obtained.

The electrical characteristics of each of the obtained varistor elements were E ₁₀ (voltage value when a current of ₁₀ mA was applied), α (voltage nonlinear coefficient), pulse resistance, solder wettability, and electrode strength. The measurement was performed under the same conditions as in Experimental Example 1, and the measurement results are shown in Table 4.

In Table 4, the comparative element (Sample No. 7) and the measurement results of electrical characteristic values are also shown for reference.

[0045]

[Table 4]

As is clear from Table 4, silver (Ag) 10
When the total content of metallic tin (Sn) and stannous oxide (SnO) is 0.5 part or more based on 0 part, stable and good ohmic property is obtained. Furthermore, metallic tin (Sn) and stannous oxide (Sn)
When the total content of O) is 10.0 parts or less, it is possible to provide a stable and good ohmic property and a varistor element having good solder wettability.

Experimental Example 5 A semiconductor porcelain mainly composed of SiTiO ₃ and having a surface or a crystal grain boundary having a high resistance was prepared in advance. Separately from this,
Silver (Ag) 100 parts, metallic tin (Sn) 5.0 as electrodes
Parts, and a composition having a composition ratio of 50 parts of organic vehicle, electrode pastes having different contents of glass frit (lead borosilicate) as shown in Table 5 were prepared.

Then, each electrode paste was applied to the surface of the semiconductor porcelain in a thickness of 5 to 10 μm according to a conventional method, and then baked at a temperature of 750 ° C. in an N ₂ atmosphere, and the voltage of the glass frit containing various contents was varied. Linear resistance elements, so-called varistor elements (sample numbers 26 to 30) were obtained.

The electrical characteristics of each obtained varistor element were E ₁₀ (voltage value when a current of ₁₀ mA was applied), α (voltage non-linear coefficient), pulse resistance, solder wettability, and electrode strength. The measurement was performed under the same conditions as in Experimental Example 1, and the measurement results are shown in Table 5.

[0050]

[Table 5]

As is clear from Table 5, silver (Ag) 10
A varistor having a sufficient electrode strength in which the content of metallic tin (Sn) is 5.0 parts (within the scope of the present invention) and the content of glass frit is 1.5 parts or more with respect to 0 part. The device is obtained. Further, when the content of the glass frit is 6.0 parts or less, it is possible to provide a varistor element having sufficient electrode strength and good solder wettability.

[0052]

As described above, according to the present invention, by baking and depositing the electrode of this structure on the semiconductor porcelain, the soldering is good, the adhesive strength to the semiconductor porcelain is large, and the pulse and the soldering There is an effect that a voltage non-linear resistance element having stable electrical characteristics and high reliability against heat at the time can be provided at low cost.

The product of the present invention can also be applied to a semiconductor ceramic electric component having a positive or negative temperature coefficient of resistance.

Claims (1)

[Claims] 1. A voltage non-linear resistance element in which an ohmic electrode is formed by depositing on a semiconductor porcelain, wherein the ohmic electrode contains at least one of metallic tin or stannous oxide in silver and glass frit, and A baking electrode baked in a neutral atmosphere, wherein at least one kind of metallic tin or stannous oxide is used for 0.5 to 10.0 with respect to 100 parts of silver and 1.5 to 6.0 parts of glass frit. A voltage non-linear resistance element, characterized in that it is contained within the range of a part.