KR0162022B1 - Thick film resistor composition and variable resistor - Google Patents

Abstract

The present invention seeks to provide a thick film resistor composition which has good electrical properties, has a low contact resistance and which is suitable for use in a regulating resistor which produces a stable conductive coupling during sliding between the slider and the resistor sliding passageway.

Oxide additive selected from the group consisting of 10 to 50% by weight of electrically conductive pyrochlore having a specific surface area of 7 m 2 / g or less, 20 to 70% by weight of glass binder free of cadmium oxide and aluminum oxide, zinc oxide and cadmium oxide 0 to 5% by weight is dispersed in an organic vehicle to produce a thick film resistor composition, which is then printed on a substrate and fired to produce a resistor for use in the regulating resistor.

Description

Thick Film Resistor Compositions and Rheostats

1 shows an equivalent circuit used for evaluation of contact resistance.

2 shows a measuring circuit used for evaluating a change in contact resistance.

3 shows an oscilloscope waveform.

The present invention relates to thick film pyrochlore resistor compositions suitable for use in regulating resistors and to regulating resistors prepared therefrom.

In regulating resistors widely used in the fields of control, sensors and settings, sliding contacts slide while maintaining conductive coupling and sliding passages formed from ohmic resistors obtained by firing a resistor composition screen-printed, sprayed or otherwise applied to a substrate. The movement and the current and magnitude obtained as the output signal depend on the magnitude of the voltage and resistance value corresponding to the sliding contact position on the sliding passage.

The regulating resistor is used to convert the rotational angle and other mechanical inputs of the rotary motion into a corresponding electrical output signal, for example a voltage, these electrical properties of which, among other things, wear of the sliding surface of the sliding passage, sliding contact and sliding passage. It is affected by the change in the conductive coupling between, and / or the sliding resistance. As a result, there is a undulation in the output smoothness of the regulating resistor.

Examples of important factors that contribute to stabilizing the linearity of the regulating resistor and suppressing the sliding noise include: stabilizing the conductive coupling between the slider and the sliding surface, and reducing contact resistance while stabilizing the overall resistance over temperature changes. Stabilization is mentioned. Therefore, it is desirable to develop a conductor composition paste that smoothes the sliding passage surface formed using the thick film resistor composition and has significant electrical conductivity and ensures stable conductive coupling.

The regulating resistor is generally formed from a thick film resistor composition, and most thick film resistor compositions contain a conductor component, a binder, and an organic vehicle as main components. The conductor component determines the electrical properties of the thick film conductors that make up the sliding passage formed by ohmic resistance and at the same time affects the mechanical properties. Binders, such as glass and / or crystalline oxide, act to fix the thick film together to bond to the substrate. Organic vehicles, on the other hand, are dispersion media that affect the use properties of the resist composition and in particular its properties.

It is an object of the present invention to provide a thick film resistor composition suitable for use in regulating resistors, which has good electrical properties, has low contact resistance and creates a stable conductive coupling during sliding between the slider and the resistor sliding passageway. It is another object of the present invention to provide a regulating resistor prepared from the above thick film resistor composition.

In order to achieve the above object, the present invention (A) 10 to 50% by weight of the electrically conductive pyrochlor of the following general formula having a specific surface area of 7 m 2 / g or less (based on the total weight of components A, B and C)

(M _x Bi _2-x ) (M ' _y M _2-y ) O _7-Z

Wherein M is selected from the group consisting of yttrium, thallium, indium, cadmium, lead, copper, and rare earth metals, M 'is selected from the group consisting of platinum, titanium, chromium, rhodium and antimony, and M is Ruthenium, iridium, or mixtures thereof, x is 0 to 2, with x≤1 for monovalent copper, y is 0 to 0.5, provided that M 'is rhodium or platinum, titanium, chromium, rhodium and When at least one element selected from antimony, y is 0 to 1, z is 0 to 1, provided that z is at least about x / 2 when M is divalent lead or cadmium), (B) cadmium oxide 20 to 70% by weight of the glass binder free of (based on the total weight of components A, B and C), (C) 0 to 5% by weight of an oxide additive selected from the group consisting of aluminum oxide, zinc oxide and gadolinium (component Based on the total weight of A, B, and C), and (D) an organic vehicle Provides a thick film resistor composition suitable for use in an adjustable resistor.

The present invention also provides an adjustable resistor in which a sliding passage is formed by applying the above-described thick film resistor composition to a substrate.

Inorganic solids of the thick film resistor composition according to the present invention include pyrochlor, glass binder and oxide additive. Now, the components will be described in detail.

Pyrochlor has the following general formula as a multicomponent compound of Ru ⁺⁴ , Ir ⁺⁴ , or mixtures (M) thereof.

(M _x Bi _2-x ) (M ' _y M _2-y ) O _7-Z

Wherein M is selected from the group consisting of yttrium, thallium, indium, cadmium, lead, copper, and rare earth metals, M 'is selected from the group consisting of platinum, titanium, chromium, rhodium and antimony, and M is ruthenium , Iridium or mixtures thereof, x is 0 to 2, with x≤l for monovalent copper, y is 0 to 0.5, provided that M 'is rhodium or platinum, titanium, chromium, rhodium and antimony When at least one element selected from among y is 0 to 1, z is 0 to 1, provided that z is equal to at least about x / 2 when M is divalent lead or cadmium.

These pyrochlor materials are described in detail in US Pat. No. 3,583,931.

Among the pyrochlorates, bismuth bismuth (Bi ₂ Ru ₂ O ₇ ) and lead luthenate (Pb ₂ Ru ₂ O ₆ ) can be easily obtained in pure form and are not adversely affected by the glass binder and are relatively affected by temperature. It is preferable because it has a low resistance value that is not affected and remains stable even when heated to about 1000 ° C. in air and relatively stable under a reducing atmosphere. Other examples of pyrochlore include Pb _1.5 Bi _0.5 Ru ₂ O _6.5 and GdBiRu ₂ O _6.5 . In all of these, y = 0.

The pyrochlor used in the present invention should have a specific surface area of 7 m 2 / g or less. In practice, fatigue chlorides with specific surface areas of 0.1 to 7 m 2 / g are used, but fatigue chlorides outside this range are adversely affected by the electrical properties of the regulating resistor, the contact resistance increases and the conductive coupling during sliding between the slider and the conductor sliding passageway. It is not suitable because it becomes unstable. In particular, in view of availability and other factors, pyrochlores having a specific surface area of 0.5 to 5 m 2 / g are suitable for use in the present invention.

The pyrochlor phase contained in the resistor composition of the present invention provides the conductivity, sinterability, and stability required for the resistor composition to form the regulating resistor, and the glass binder used is used to control the temperature coefficient (TCR) of the resistor in the past. Since it does not contain cadmium oxide added to it, it produces stable and low contact resistance (R _c ) and contact resistance change (CRV) without causing any side effects.

The composition of the glass binder depends on the need for a thick film to properly match the nonconductive substrate. Specifically, the glass binder should have a bonding temperature range of about 540 to 950 ° C. while having the same expansion / contraction properties as the substrate. Therefore, a wide range of glass binders meeting these requirements can be used in the present invention. A distinctive feature of the glass binders belonging to the present invention is the absence of cadmium oxide. Examples thereof include lead silicate glass, lead borosilicate glass, and aluminum borosilicate zinc glass. Representative compositions of the glass binders are shown in Table 1 below.

Among these glass binders, no. 1, 2, 4, 5 and 9 are preferred.

Glass binders were prepared by mixing certain components (or their precursors, such as HBO in the case of BO) in the desired proportions using conventional glass making techniques, and heating the resulting mixture to produce a melt. . As is well known, the technique involves performing heating to a peak temperature for a time sufficient to completely transform the melt into a liquid while avoiding gas production. In this type of study, the peak temperature is 1100-1500 ° C., generally 1200-1400 ° C. Typically, the melt is then poured onto a cooling belt or into a cooling water flow to cool it. It is then milled to reduce the particle size as desired.

In addition to the glass binder component, it is useful to include small amounts of oxide additives selected from the group consisting of aluminum oxide, zinc oxide and cadmium oxide in the thick film resistor composition of the present invention. The additives can be used in the form of commercially available particulates. These oxide additives further improve R and CRV by utilizing the formation of resistor microstructures.

The inorganic solids of the resistor composition of the present invention are dispersed in an organic vehicle to produce a printable composition paste. The weight ratio of inorganic material to vehicle is 1: 1 to 6: 1.

Any inert liquid can be used as the vehicle. The vehicle used may also be water or various organic liquids with or without thickeners and / or stabilizers and / or other conventional additives. Examples of organic liquids that can be used include aliphatic alcohols, esters of such alcohols (eg acetate and propionate), terpenes (eg turpentine and terpineol) and other solvents (eg turpenta) Resins contained in the monobutyl ether of phosphorus and ethylene glycol monoacetate, for example, polymethacrylate solution or ethyl cellulose solution of lower alcohol). The vehicle may contain a volatile liquid designed to accelerate the rapid cure that occurs after applying the material to the substrate. The vehicle may comprise the liquids.

Preferred vehicles are based on ethyl cellulose and B-terpineol.

The paste must be made using three roll mills

The sliding passage on the regulating resistor of the present invention can be produced, for example, by printing the presented resistor composition in a film form on a substrate made of ceramic, alumina or other dielectric in a conventional manner. It is better to use an alumina substrate.

In general, screen stencil technology should be used. The printed pattern obtained is generally left for leveling, dried for about 10 minutes at a high temperature such as 150 ° C., and calcined in air or in a belt furnace, for example at a peak temperature of about 850 ° C.

For example, palladium based PALINEY to reduce wear on sliding passage surfaces and to lower stenosis resistance. (Registered trade name) is used as a material for the regulating resistor slider. A 30 g crimp pressure must be applied to crimp the slider against the sliding passageway surface of the resistor to create a conductive coupling.

Among the regulating resistor characteristics, the contact resistance is evaluated using the narrow contact resistance (R _c ). The resistance R _l3 between the electrode terminals mounted at both ends of the sliding passage formed from the resistor in the manner as shown in FIG. 1 and the slider are measured when the slider is located at a point corresponding to about 1/2 of the total resistance value. Using the resistance values R _l2 and R ₂₃ between the slider and the corresponding terminal, R _c is calculated with the help of the following equation.

R _c (%) = {(R _l2 + R ₂₃ -R _l3 ) / 2R _l3 } x 100 (I)

The stenosis contact resistance (R _c ) is measured according to JIS C 45261. In the equivalent circuit shown in FIG. 1, the test resistance (R) has a contact resistance (R _c), the R _c may be calculated based on the equation 1.

In addition to using R _c in evaluating the contact resistance of the regulating resistor in the stationary state, the slider is slid over the resistor so that the contact resistance changes with position on the resistor, and the minimum and maximum of these changes are compared to The maximum change (Fig. 3A) obtained as a result of the comparison is called a change in contact resistance (RCV), and this parameter was used to evaluate the stability of the contact resistance.

Using a measuring circuit as shown in FIG. 2, a direct current is passed through the sample resistor and the oscilloscope generates the noise voltage generated between the sliding passage (resistor) and the slider as the slider rotates or moves at a rate of one cycle per two minutes. By measuring by, the contact resistance change (CRV) can be calculated from the waveform shown in FIG. 3 using, for example, Equation 2 below.

CRV (%) = {(R _c , (Max) -R _c (Min))} / {Total Resistance (R _l3 )} × 100 = (A / R _l3 ) × 100 (II)

In addition, the measured value from the contact resistance (about 0) on the terminal to the peak (maximum contact resistance; FIG. 3B) can be defined as the dynamic narrowing contact resistance (CR) and calculated using the following equation III.

CR (%) = {B / total resistance (R ₁₃ )} × 100 (Ⅲ)

Since relationship B A is always true, it is CR CRV, so CR approaching zero gradually corresponds to the anomaly-derating resistor.

The temperature coefficient (TCR) of the resistance, which represents the rate at which the resistance changes with temperature, is usually expressed in ppm / ° C. When the TCR is high, it is an important resistor characteristic because the temperature change is easy to produce a relatively large resistance change. TCR is generally calculated using measurements including (1) resistance at room temperature (25 ° C.), (2) resistance at −55 ° C., and (3) resistance at 125 ° C. Great care should be taken to achieve thermal equilibrium at each temperature. Resistance change is expressed as a function of room temperature resistance divided by temperature increase, which is made to obtain this temperature coefficient. The rate of change from resistance at −55 ° C. to resistance at room temperature is labeled with CTCR, and the change from resistance at room temperature to resistance at 125 ° C. is labeled with HTCR.

The thick film resistor composition of the present invention makes it possible to provide a regulating resistor which has excellent electrical properties, has a low contact resistance and creates a stable conductive coupling during sliding between the slider and the resistor sliding passageway.

Now, the present invention will be described in more detail with reference to Examples and Comparative Examples. The blending ratio of the inorganic binder, the conductive component and the oxide additive used in the examples are all expressed in weight percent. Among the examples shown in Table 2, Examples 1 to 8 and 17 to 24 represent Examples of the present invention, while Examples 9 to 16 represent Comparative Examples.

Example 1

25 wt% of GdBiRu ₂ O _6.5 pyrochlore having a specific surface area of about 3 m 2 / g and the glass binder No. 5 25% by weight was dispersed in a vehicle consisting of 15 parts ethyl cellulose and 85 parts β-terpineol and having a viscosity of about 30 Pa.S and blending the components using three roll mills to create a paste composition. The weight ratio of inorganic solids (pyrochlor + glass binder): vehicle in the composition was 70/30.

The starting materials are heated and melted in the temperature range of 1000 to 1700 (depending on the glass composition) for about 30 minutes to 5 hours until gas production is completely stopped, the melt is quenched in water and the product is then subjected to about 2 to The glass binder was prepared by milling to have a specific surface area of 5 m 2 / g. The resistor composition thus prepared was applied to the alumina substrate by screen printing and the resulting pattern was baked at 850 ° C. The electrical characteristics of this resistor were evaluated by the method described above. The results are shown in Table 2 below.

[Examples 2 to 8]

The paste composition and the resistor were prepared by performing the same method as in Example 1 according to the instructions specified in Table 2. The results obtained by measuring the electrical properties of the resistors are also shown in Table 2.

[Examples 9 to 16]

In Comparative Examples 9 to 12, Table 2 is used except that the pyrochlor component having a specific surface area of about 8 m 2 / g is used instead of the pyrochlor component having a specific surface area of about 3 m 2 / g used in Example 1. The paste composition and resistors were prepared by following the same method as in Example 1 according to the specified instructions.

In Comparative Examples 13 to 16, the paste composition was prepared by carrying out the same method as in Example 1 according to the instructions shown in Table 2 except for using ruthenium oxide (RuO ₂ ) instead of the pyrochlor component used in Example 1. Low antibodies were prepared. The results obtained by measuring the electrical properties of the resistors thus obtained are also shown in Table 2.

[Examples 17 to 24]

These examples relate to the use of oxide additives. The aluminum oxide used had a specific surface area of 0.2 to 0.7 m 2 / g (average: about 0.5 m 2 / g) and 7.4 to 10.5 m 2 / g (average: about 9 m 2 / g). The second type of aluminum oxide gave better results. The used zinc oxide and cadmium oxide had specific surface areas of 1.8 to 5.0 m 2 / g (average: about 3 m 2 / g).

The paste composition and the resistor were prepared by performing the same method as in Example 1 according to the instructions specified in Table 2. The results obtained by measuring the electrical properties of the resistors are also shown in Table 2.

As can be seen from Table 2, a resistor that maintains low CR over a wide range of firing temperatures and has a low TCR can be obtained using 3 m 2 / g pyrochlor as in Examples 1 to 8, and its TCR value The resistor whose CR value is closer to zero without changing this much can be obtained by adding an inorganic oxide as in Examples 17 to 24.

Claims (12)

(A) 10 to 50% by weight, based on the total weight of components A, B and C, of the electrically conductive pyrochlor of the following general formula having a specific surface area of 7 m 2 / g or less (M _x Bi _2-x ) (M ' _y M _2-y ) O _7-Z Wherein M is selected from the group consisting of yttrium, thallium, indium, cadmium, lead, copper, and rare earth metals, M 'is selected from the group consisting of platinum, titanium, chromium, rhodium and antimony, and M is Ruthenium, iridium, or mixtures thereof, x is 0 to 2, with x≤1 for monovalent copper, y is 0 to 0.5, provided that M 'is rhodium or platinum, titanium, chromium, rhodium and When at least one element selected from antimony, y is 0 to 1, z is 0 to 1, provided that z is at least about x / 2 when M is divalent lead or cadmium), (B) cadmium oxide 20 to 70% by weight of the glass binder free of (based on the total weight of components A, B and C), (C) 0 to 5% by weight of an oxide additive selected from the group consisting of aluminum oxide, zinc oxide and gadolinium (component Based on the total weight of A, B, and C), and (D) an organic vehicle Is a thick film resistor composition suitable for use in an adjustable resistor. The composition of claim 1, wherein the specific surface area of the electrically conductive pyrochlor is 0.1 to 7 m 2 / g. The composition of claim 1, wherein the specific surface area of the electrically conductive pyrochlor is 0.5 to 5 m 2 / g. The composition of claim 1 wherein the oxide additive is absent. The composition of claim 1 wherein said oxide additive is present. The composition of claim 1, wherein the organic vehicle is contained in an amount of 1: 1 to 6: 1 by weight of the mixture of components A, B, and C: organic vehicle. (A) 10 to 50% by weight, based on the total weight of components A, B and C, of the electrically conductive pyrochlor of the following general formula having a specific surface area of 7 m 2 / g or less (M _x Bi _2-x ) (M ' _y M _2-y ) O _7-Z Wherein M is selected from the group consisting of yttrium, thallium, indium, cadmium, lead, copper, and rare earth metals, M 'is selected from the group consisting of platinum, titanium, chromium, rhodium and antimony, and M is Ruthenium, iridium, or mixtures thereof, x is 0 to 2, with x≤1 for monovalent copper, y is 0 to 0.5, provided that M 'is rhodium or platinum, titanium, chromium, rhodium and When at least one element selected from antimony, y is 0 to 1, z is 0 to 1, provided that z is at least about x / 2 when M is divalent lead or cadmium), (B) cadmium oxide 20 to 70% by weight of the glass binder free of (based on the total weight of components A, B and C), (C) 0 to 5% by weight of an oxide additive selected from the group consisting of aluminum oxide, zinc oxide and gadolinium (component Based on the total weight of A, B, and C), and (D) an organic vehicle The regulating resistor having a sliding passage formed by applying the thick film resistor composition to a substrate. The regulating resistor according to claim 7, wherein the specific surface area of the electrically conductive pyrochlor is 0.1 to 7 m 2 / g. The regulating resistor according to claim 7, wherein the specific surface area of the electrically conductive pyrochlor is 0.5 to 5 m 2 / g. 8. The resistor according to claim 7, wherein the oxide additive is absent. 8. The resistor according to claim 7, wherein said oxide additive is present. 8. The resistor according to claim 7, wherein said organic vehicle is contained in an amount in which the weight ratio of the component: organic vehicle of the components A, B and C is 1: 1 to 6: 1.