JP2654824B2 - Resistance composition and method for producing thick film resistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention can be fired in an inert atmosphere such as a nitrogen atmosphere and has excellent electrical characteristics such as reproducibility of resistance value, resistance temperature characteristics, and noise (current noise). The present invention relates to a resistance composition for producing a tantalum-based thick film resistor and a method for producing a thick film resistor using the same.

2. Description of the Related Art Thick film resistors are prepared by dispersing a conductive powder composed of a metal compound such as a metal or a metal oxide and a glass powder in an organic vehicle into a paint or paste form on an insulating substrate. After printing in the pattern described above, firing is performed, and trimming is performed if necessary, so that a predetermined resistance value is obtained.
Conventionally, ruthenium oxide-based materials have been the mainstream, but in recent years, tin oxide-based and tantalum-based resistors have been put into practical use as thick film resistors that can be fired in an inert atmosphere and are compatible with base metal thick film conductors. Of these, in tantalum, metal tantalum,
It is known to use tantalum nitride, tantalum boride or the like as a conductive component. For example, JP-A-55-108702 discloses tantalum metal particles and glass frit, and titanium, boron, zirconium oxide, tantalum oxide, oxide A resistance composition is disclosed in which additives such as titanium, barium oxide, tungsten oxide, tantalum nitride, titanium nitride, molybdenum silicide, and magnesium silicate are blended up to 50% by weight of the tantalum particles. Also U.S. Patent No. 3503801, boride of tantalum (TaB ₂₎ resistor composition comprising a metal boride powder and a glass frit, such as is disclosed. Such a tantalum-based resistor is expected as a promising material for a low to medium resistance region in the range of 10Ω / □ to 10kΩ / □.

Problems to be Solved by the Invention However, a resistor obtained by firing a resistance composition composed of a tantalum metal powder and a glass powder is easily affected by firing conditions, and its characteristics are likely to fluctuate. In addition to the poor noise characteristics, there is a problem that the fluctuation of the TCR corresponding to the resistance value is large. In particular, in a relatively high resistance region exceeding 1 kΩ / □, the variation in the resistance value becomes abnormally large, and the temperature coefficient of resistance becomes extremely large negatively, which is not practical. This is because firing a composition consisting of tantalum metal and glass in an N ₂ atmosphere produces tantalum oxide in addition to tantalum.How the reaction occurs depends on the firing time, firing temperature,
Since there is a difference depending on the oxygen concentration in the firing atmosphere, etc., the ratio of tantalum, which is a conductive component in the fired body, to tantalum oxide, which is a non-conductive component, changes. It is considered that the characteristics are not stable.

The resistance of the resistor manufactured using the tantalum boride powder and the glass is not extremely bad, but the fired body shows a more semiconductor-like behavior and the temperature coefficient of resistance has a large negative value that is unacceptable. Show. Further, tantalum boride has a disadvantage that it is difficult to obtain fine particles, so that a resistive coating having a uniform fine conductive particle network cannot be obtained, and TCR and noise deteriorate.

Therefore, the object of the present invention is to provide a wide resistance value range, especially 10Ω.
An object of the present invention is to manufacture a stable resistor having low process sensitivity in the range of / □ to 100 kΩ / □, good reproducibility of resistance value, low temperature coefficient of resistance, and low noise.

Means for Solving the Problems The present invention provides a resistance composition comprising a tantalum oxide powder, a boron powder, a glass powder and an organic vehicle, and printing this resistance composition on an insulating substrate and firing in an inert atmosphere. And reacting boron with tantalum oxide to precipitate tantalum boride as conductive particles in a glass matrix.

The tantalum oxide powder and the boron powder used have an average particle size of 5 μm or less, preferably 1 μm or less. Especially,
Those having an average particle size of about 0.1 to 0.5 μm are preferred.

The glass powder is not particularly limited as long as it is commonly used for the resistance composition. For example, borosilicate alkaline earth metal glass, borosilicate alkaline earth aluminum glass and the like are representative.

The mixing ratio of each component is 5 to 60% by weight of tantalum oxide,
Desirably, boron is about 1 to 20% and glass is about 20 to 94%. When the content of tantalum oxide is less than 5%, even if tantalum boride is produced, the amount is small and properties such as TCR deteriorate. If it is more than 60%, the strength of the film becomes weak. If the amount of boron is less than 1%, the amount of tantalum boride produced is too small to obtain good resistance characteristics, and if it exceeds 20%, the strength also decreases.

In order to further adjust the resistance value, the resistance temperature characteristic, and other characteristics, an additive can be added to the resistance composition of the present invention up to about 30% by weight. As the additive, for example, generally known silicon, molybdenum, tungsten, titanium, tantalum, silicon oxide, zirconium oxide, zinc oxide, nickel oxide, cobalt oxide, vanadium oxide, titanium oxide, barium oxide, tungsten oxide, In addition to molybdenum silicide, tantalum nitride, titanium nitride, magnesium silicate, and the like, tantalate salts such as barium tantalate, cobalt tantalate, gallium tantalate, and indium tantalate can be given.

The resistor composition of the present invention is fired under an ordinary firing condition in an inert atmosphere such as an N ₂ atmosphere to form a resistor having tantalum boride dispersed in a glass matrix as a conductive component.

The present invention is characterized in that tantalum oxide powder and boron powder are used as starting materials, and that they are reacted during firing to deposit only tantalum boride as conductive particles.

When the composition comprising the tantalum oxide powder, the boron powder and the glass is fired in an inert atmosphere, the x-ray diffraction peak of the tantalum boride conductive phase crystal is shown. This tantalum boride is an interstitial compound represented by the chemical formula TaB ₂ and is the only conductive component generated by the reaction between tantalum oxide and boron. Tantalum boride has a specific resistance of about 100 × 10 ⁻⁵ Ω · cm, which is higher than that of tantalum metal of about 12 × 10 ⁻⁶ Ω · cm, and sinters a composition consisting of conventional tantalum metal powder and glass powder. As compared with the resistor obtained in this way, the volume of the conductive particles is increased at the same resistance value, so that the stability of the resistance characteristics is remarkably improved. Therefore, the resistor manufactured by such a process is
It is considered that fluctuations in characteristics due to changes in the firing atmosphere and the like are reduced, and variations in resistance values are reduced, so that reproducibility is greatly improved. Further, the tantalum boride conductive particle network formed in the resistor is stabilized, and noise and TCR characteristics are improved.

In addition, the present invention produces fine tantalum boride particles corresponding to the particle size of the tantalum oxide particles and boron particles used as the starting materials during firing, and these are dispersed very uniformly in the glass, so that from the beginning, Unlike the case where tantalum boride powder is used, the resistance distribution, TCR and noise are much better.

As a result, it is possible to manufacture a resistor having excellent characteristics not only in a low resistance region but also in a relatively high resistance region of 1 k to 100 kΩ / □ which has not been practically used until now.

It is to be noted that tantalum oxide and boron do not have to be completely reacted to form tantalum boride. This is because, as described above, the specific resistance of tantalum boride, which is a conductive component, is much higher than that of tantalum, so that the presence of tantalum oxide, which is a nonconductive component, has little effect on the resistance value. . Therefore, there is no adverse effect even if an excessive amount of tantalum oxide is used. Excess boron is also oxidized during firing, eventually forming a matrix of resistors with the glass.

Examples Table 1 shows the compositions of the glasses used in the examples.

Example 1 40 parts by weight of tantalum oxide powder, 6 parts by weight of amorphous boron powder, and 54 parts by weight of glass A powder were mixed, and 1 part by weight of ethyl cellulose and 2,2,4-trimethyl-1,3-pentane were used as an organic vehicle. 30 parts by weight of diol monoisobutyrate was added and kneaded to prepare a resistance paste.

This resistive paste was printed on an alumina substrate on which a copper thick film electrode was previously baked in a 1 mm × 1 mm square pattern, dried in air at 150 ° C. for 10 minutes, and then heated to a maximum temperature of 900 ° C. in N ₂ atmosphere for 10 minutes. The firing was performed under the conditions of a holding and 60-minute cycle. The sheet resistance and resistance variation (CV) of the obtained resistor are 107Ω / □ and 2.9%, respectively. TCR is + 65ppm / ° C on the high temperature side (H-TCR, + 25 ° C to + 125 ° C), and low temperature side. (C-TCR, -55 to + 25 ° C) was +93 ppm / ° C.
The noise was also excellent at -25 dB. CV is a value for 80 resistors.

When the fired body was examined with an X-ray diffractometer, a peak of tantalum boride (TaB ₂ ) was detected.

Examples 2 to 8 Tantalum oxide powder, amorphous boron powder and glass powder were mixed at the ratios shown in Table 2, and resistance pastes were produced in the same manner as in Example 1.

The resistance value, resistance value variation (CV), TCR, and noise of a resistor obtained by baking this resistance paste on an alumina substrate in the same manner as in Example 1 were examined.

Comparative Example 1 40 parts by weight of metal tantalum powder and 60 parts by weight of glass A powder were mixed to prepare a resistance paste in the same manner as in Example 1.

The resistance value of the resistor obtained by baking this resistor paste on an alumina substrate in the same manner as in Example 1, H-TCR, C
Although -TCR was 500Ω / □, + 35ppm / ° C, and + 38ppm / ° C, respectively, the CV was large at 10.6%, and the noise was -3dB. Compared to −15 dB in the sixth embodiment, it was very bad.

Comparative Examples 2-3 Tantalum powder and glass A powder were mixed at the ratio shown in Table 3, and resistance pastes were prepared in the same manner as in Example 1.

The resistance value, CV, TCR and noise of the resistor obtained by baking this resistor paste on an alumina substrate in the same manner as in Example 1 were examined.

As is evident from Table 3, the CV and noise characteristics are extremely poor and the TCR is extremely negative as compared with the values of the examples.

Comparative Example 4 50 parts by weight of tantalum boride powder and 50 parts by weight of glass A powder were mixed to prepare a resistance paste in the same manner. Table 3 shows the characteristics of the resistor obtained by baking on an alumina substrate. The resistor had extremely large TCR and noise and was not practically usable.

Effect of the Invention The present invention uses a mixture of a specific ratio of tantalum metal oxide powder and boron powder as a starting material, and reacts them during firing to form a tantalum boride conductive phase, thereby providing tantalum metal or conductive particles as conductive particles. As compared with a resistance composition using tantalum boride alone, a thick-film resistor excellent in electrical characteristics in a wide range of resistance values can be produced with good reproducibility.

Claims (2)

(57) [Claims] 1. A resistance composition comprising a tantalum oxide powder, a boron powder, a glass powder and an organic vehicle. 2. The method according to claim 1, wherein the resist composition is printed on an insulating substrate and fired in an inert atmosphere.
A method for producing a thick film resistor, comprising reacting tantalum oxide with boron to precipitate tantalum boride as conductive particles in a glass matrix.