JPWO2006115240A1 - Resistive paste, variable resistor and manufacturing method thereof - Google Patents

Abstract

Provided are a resistor paste that can provide a resistor that is not only inexpensive but also has excellent moisture resistance and TCR characteristics, and a variable resistor using the resistor paste. Resistive paste made of carbon-based conductive powder and substituted monohydric phenol resin, substrate 1 provided with resistor 5 on the upper surface, fixed side terminals and variable side terminals provided on substrate 1, and sliding on the substrate A variable resistor comprising a slider 6 that is movably arranged and has a contact portion that is in sliding contact with the resistor, wherein the resistor 5 is configured using the resistor paste.

Description

  The present invention relates to a resistance paste used for obtaining an electrical resistor, and more particularly, a resistance paste including a carbon-based conductive powder and a resin, and a variable having a resistor obtained using the resistance paste. The present invention relates to a resistor and a manufacturing method thereof.

  Conventionally, various resistors are used to manufacture various resistors such as variable resistors. When forming a resistor on a substrate or the like, a method of applying and baking a resistance paste is widely used. In the method of applying and baking the resistance paste, it is possible to easily form resistors having various resistance values by adjusting the composition, the application area and the application thickness of the resistance paste.

Conventionally, as the resistance paste, a cermet resistance paste mainly composed of a metal oxide powder such as RuO ₂ and glass, and a carbon resistance paste including a carbon based conductive powder such as carbon and a synthetic resin as main components. It has been known.

  Although the carbon-based resistance paste has the advantage of being cheaper than the cermet-based resistance paste, there is a problem that the high-temperature characteristics, the moisture resistance characteristics, and the resistance temperature characteristics (TCR characteristics) are not sufficient.

On the other hand, a resistor used in an in-vehicle electronic device is not only inexpensive, but is required to exhibit sufficient characteristics even in an environment where usage conditions are severe. Therefore, Patent Document 1 below proposes a resistor paste in which a carbon fibril material composed of aggregates having a specific average particle diameter in which specific fine thread-like carbon fibrils are entangled with each other is dispersed in a resin liquid. Yes. Here, by using the above-mentioned specific carbon fibril material as a carbon-based material, it has a stable resistance value from a low temperature range to a high temperature range, and changes in resistance value over time even when used for a long time at high temperatures. It is said that a carbon-based resistor with a small amount can be obtained.
JP-A-7-106104

  As described above, by using the resistor paste described in Patent Document 1 as described above, a resistor excellent in high-temperature characteristics can be obtained. However, in the resistor using the resistor paste, moisture resistance characteristics and TCR There was a problem that the characteristics were still not sufficient.

  An object of the present invention is to provide an inexpensive resistance paste containing carbon-based conductive powder and resin in view of the above-described conventional state of the art, and to obtain a resistor excellent in not only high temperature characteristics but also moisture resistance characteristics and TCR characteristics. It is an object of the present invention to provide a resistance paste that can be used, a variable resistor having a resistor formed by using the resistance paste, and a method of manufacturing the variable resistor.

  The resistance paste according to the present invention includes carbon-based conductive powder and a substituted monohydric phenol resin.

  In a specific aspect of the resistance paste according to the present invention, a resin obtained by a condensation reaction of a substituted monohydric phenol and formaldehyde is used as the substituted monohydric phenol resin, and preferably p as the substituted monohydric phenol is p. -T-Butylphenol is used.

  In another specific aspect of the resistance paste according to the present invention, the carbon-based conductive powder and the substituted monohydric phenol resin are 17.5 to 35.0: 41.5 to 53.0 in a weight ratio. Included as a percentage. In other words, the substituted monohydric phenol resin is included at a ratio of 118 to 303 parts by weight with respect to 100 parts by weight of the carbon-based conductive powder.

In still another specific aspect of the resistance paste according to the present invention, a polycarboxylic acid-based dispersant is further included.

  A variable resistor according to the present invention is disposed on a substrate having a resistor provided on an upper surface thereof, a fixed terminal and a variable terminal provided on the substrate, and slidable on the substrate. A slider having a contact portion slidably contacting the slider, the slider being electrically connected to the variable terminal, and the resistor being made of a resistance paste configured according to the present invention. It is characterized by.

The variable resistor manufacturing method according to the present invention includes a step of applying a resistance paste configured according to the present invention on an insulating substrate, a step of baking the applied resistance paste to form a resistor, and the insulating substrate. A step of providing a fixed-side terminal and a variable-side terminal, and a step of attaching a slider having a contact portion slidably contacting the resistor and electrically connected to the variable-side terminal to the insulating substrate It is characterized by providing.
(The invention's effect)

  Since the resistance paste according to the present invention includes carbon-based conductive powder and a substituted monohydric phenol resin, it is possible to obtain a resistor that is not only inexpensive but also has excellent moisture resistance and TCR characteristics. That is, although the resistance paste using the carbon-based conductive powder has an advantage that it is less expensive than the cermet resistance paste, there is a problem that the moisture resistance characteristics and the TCR characteristics are not sufficient. On the other hand, as described above, according to the present invention, since the substituted monohydric phenol resin is used as a synthetic resin combined with the carbon-based conductive powder, the moisture resistance and TCR characteristics of the obtained resistor are improved. It becomes possible.

  Prior to the filing of this application, it was known to use a phenolic resin as a resin combined with a carbon-based conductive powder in a carbon-based resistance paste, but in a carbon-based resistance paste using a normal phenolic resin, moisture resistance characteristics and TCR characteristics Was not enough.

  On the other hand, the substituted monohydric phenol resin used in the present invention, unlike the case of using a normal phenol resin, can not be expected to give a resistor excellent in moisture resistance and TCR characteristics. It gives an effect.

  Therefore, according to the present invention, it is possible to obtain a resistor that is not only inexpensive, but also excellent in moisture resistance and TCR characteristics.

  In addition, when a substituted monohydric phenol resin obtained by a condensation reaction of a substituted monohydric phenol and formaldehyde is used as the substituted monohydric phenol resin, the moisture resistance and TCR characteristics can be further enhanced. In particular, when the substituted monohydric phenol is p-t-butylphenol, the moisture resistance and TCR characteristics can be remarkably improved.

  When a polycarboxylic acid-based dispersant is further included, the wettability between the carbon-based conductive powder and the substituted monohydric phenol resin is increased, and the adhesion strength between the carbon-based conductive powder and the substituted monohydric phenol resin is increased. It is done. Therefore, the strength of the resistance paste coating is increased, and it becomes possible to reduce cracks in the resistor obtained by baking the resistance paste. Further, the wettability between the carbon-based conductive powder and the substituted monohydric phenol resin is increased, so that the viscosity of the resistance paste is lowered, and thereby the printability of the resistance paste can be improved.

  Details of the present invention will be described below.

  The resistance paste according to the present invention includes the carbon-based conductive powder and the substituted monohydric phenol resin as described above. Conventionally, although carbon-based resistance paste containing carbon-based conductive powder and synthetic resin is inexpensive, there is a problem that high temperature characteristics, moisture resistance characteristics, and TCR characteristics are not sufficient as compared with cermet-based resistance paste.

  Moreover, in the carbon-type resistance paste described in Patent Document 1 described above, high temperature characteristics have been improved by using a specific carbon fibril material. However, even when the carbon-based resistance paste described in Patent Document 1 is used, the moisture resistance characteristics and TCR characteristics of the obtained resistor are still not sufficient.

  As a result of earnestly examining the carbon-based resistance paste having the feature of being inexpensive, the inventor of the present application can improve moisture resistance and TCR characteristics if a specific substituted monohydric phenol resin is added to the carbon-based conductive powder. The present invention has been found and the present invention has been made.

  The substituted monohydric phenol resin used in the present invention is not particularly limited as long as it is a synthetic resin derived from a substituted monohydric phenol, but is preferably a substituted monohydric phenol resin obtained by a condensation reaction of a substituted monohydric phenol and formaldehyde. Are preferably used. By using a substituted monohydric phenol resin obtained by a condensation reaction between a substituted monohydric phenol and formaldehyde, the moisture resistance and TCR characteristics can be further enhanced.

  The substituted monohydric phenol has a structure in which one hydrogen bonded to carbon constituting the benzene nucleus other than the carbon bonded to the OH group in phenol is substituted with a monovalent substituent. It shall be said. Accordingly, examples of the monovalent substituent include a methyl group, an ethyl group, and a t-butyl group, and are not particularly limited.

  Examples of such substituted monohydric phenols include pt-butylphenol, cresol, xylenephenol, p-aminophenol, p-ethylphenol, and the like. Preferably, pt-butylphenol is used as the substituted monohydric phenol. When p-t-butylphenol is used, the moisture resistance and TCR characteristics can be significantly enhanced.

  The degree of polymerization of the substituted monovalent phenol resin is not particularly limited, but is preferably about 800 to 6000, for example. If it is less than 800, good temperature characteristics may not be obtained. If it exceeds 6000, kneading with the carbon-based conductive powder may be confused.

  In the substituted monohydric phenol resin, in addition to the substituted monohydric phenol, phenol may be further polymerized. That is, in a substituted monohydric phenol resin derived from a substituted monohydric phenol, phenol may be copolymerized with the substituted monohydric phenol. With substituted monohydric phenol resins copolymerized with phenol, water resistance may be reduced compared to substituted monohydric phenol resins using only substituted monohydric phenols as phenols, but the resistance paste printability is improved. It is done. Therefore, when it is desired to improve the printability, it is preferable to copolymerize phenol with a substituted monohydric phenol. In this case, the copolymerization ratio of phenol is 30% in a total of 100% by weight of the substituted monohydric phenol and phenol. It is desirable to set the ratio to not more than%. When the copolymerization ratio of phenol exceeds 30% by weight, the water resistance is undesirably low.

  As the carbon-based conductive powder used in the resistance paste according to the present invention, an appropriate carbon-based conductive powder conventionally used as the carbon-based conductive powder constituting the resistance paste can be used. Also, the average particle diameter of the carbon-based conductive powder that can be used is not particularly limited.

  However, in the present invention, the TCR can be controlled by using a plurality of carbon surface conductive powders having specific surface areas. That is, the carbon-based conductive powder having a large specific surface area has a function of shifting the TCR of the obtained resistor to the minus side, and the carbon-based conductive powder having a small specific surface area shifts the TCR of the obtained resistor to the plus side. Has a tendency. Therefore, it is desirable to mix a plurality of types of carbon-based conductive powders having different specific surface areas at an appropriate ratio so as to reduce the slope of the TCR characteristics. Therefore, in the present invention, preferably, carbon-based conductive powders having a plurality of specific surface areas are used in combination so that the TCR characteristics are within ± 150 ppm.

  In the resistance paste according to the present invention, the blending ratio of the carbon-based conductive powder and the substituted monohydric phenol resin is not particularly limited, but preferably, the carbon-based conductive powder and the substituted monohydric phenol resin are added by weight. In the ratio of 17.5-35.0: 41.5-53.0, in other words, in the ratio of 118-303 parts by weight of the substituted monohydric phenol resin with respect to 100 parts by weight of the carbon-based conductive powder. It is desirable to blend. When the blending ratio of the substituted monohydric phenol resin is less than the above ratio, cracking may occur in the resistor after the resistance paste is applied and baked. In addition, when the blending ratio of the substituted monohydric phenol resin is larger than the above blending ratio, the resistance paste has its own bleeding and the dimensional accuracy of the resistor may be lowered. In addition, the high temperature characteristics may deteriorate.

  More preferably, the substituted monohydric phenol resin is desirably 132 to 247 parts by weight with respect to 100 parts by weight of the carbon-based conductive powder, whereby the variation rate of moisture resistance can be less than 1%. In addition, the moisture resistance can be further enhanced.

  The resistance paste according to the present invention includes the carbon-based conductive powder and a substituted monohydric phenol resin as essential components. Therefore, the resistance paste according to the present invention is essentially composed of the carbon-based conductive powder and the substituted monohydric phenol resin.

  But in this invention, in the range which does not inhibit achievement of the subject of this invention, other components other than the said carbon type electrically conductive powder and substituted monohydric phenol resin can be mix | blended with resistance paste.

  In particular, it is desirable to add a polycarboxylic acid-based dispersant in addition to the carbon-based conductive powder and the substituted monohydric phenol resin. The polycarboxylic acid-based dispersant acts to increase the wettability between the carbon-based conductive powder and the substituted monohydric phenol resin and to increase the adhesion strength between the two.

The amount of the polycarboxylic acid dispersant added is preferably 0.3 to 5.0% by weight in the resistance paste. If it is less than 0.3% by weight, the effect of improving the wettability between the carbon-based conductive powder and the substituted monohydric phenol resin by the dispersant is hardly obtained. There is a risk that changes due to
In particular, in order to apply the resistance paste, an appropriate solvent for adjusting the viscosity is usually added in addition to the carbon-based conductive powder and the substituted monohydric phenol resin. Such a solvent is not particularly limited, and examples thereof include high-boiling solvents such as diethylene glycol monobutyl ether acetate (BCA), α-terpineol, dipropylene glycol methyl ether acetate (DPMA), and dihydroterpineol. .

  When adding a solvent, the addition amount of a solvent is suitably selected in the range which controls the applicability | paintability of resistance paste. Usually, when the total resistance paste containing carbon-based conductive powder and substituted monohydric phenol resin, other additives described later, and a solvent is 100% by weight, the blending ratio of the solvent is about 23 to 45% by weight. Good. If the content is less than 23% by weight, the coating property of the resistance paste may be reduced. If the content exceeds 45% by weight, the amount of the solvent becomes excessive, and bleeding tends to occur in the shape coated with the resistance paste, or time is required for drying. Sometimes.

  However, the solvent addition ratio varies depending on the type and blending ratio of the substituted monohydric phenol resin and carbon-based conductive powder used, the coating thickness of the resistance paste, and the type of solvent. May be selected as appropriate.

  In addition, in the resistance paste according to the present invention, other appropriate additives can be added in addition to the carbon-based conductive powder, the substituted monohydric phenol resin, and the solvent as long as the achievement of the object of the present invention is not hindered. Examples of such additives include graphite, alumina, and talc.

  The resistance paste according to the present invention is obtained by kneading the carbon-based conductive powder, the substituted monohydric phenol resin and a solvent in a solvent, and the production method is not particularly limited.

  The resistor according to the present invention is formed, for example, by applying to an insulating substrate and baking. The baking condition is not particularly limited, but is usually maintained at a temperature of about 180 to 300 ° C. for about 1 to 10 minutes.

  When the carbon-based conductive powder and the phenol resin are contained in a weight ratio of 17.5 to 35.0: 41.5 to 53.0, bleeding at the time of application of the resistance paste is difficult to occur. The resistor is more reliably provided with excellent resistance to cracking.

  In the variable resistor according to the present invention, since the resistor formed on the insulating substrate is configured using the resistance paste of the present invention, it is not only inexpensive but also has moisture resistance and TCR characteristics according to the present invention. It is possible to provide an excellent variable resistor.

  In the variable resistor manufacturing method according to the present invention, a resistor having excellent TCR characteristics and moisture resistance characteristics can be formed by applying and baking the resistance paste of the present invention on an insulating substrate. It is possible to easily provide the variable resistor of the present invention having excellent moisture resistance and TCR characteristics.

FIG. 1 is a front sectional view of an embodiment of a variable resistor according to the present invention. FIG. 2 is an exploded perspective view of the variable resistor according to the embodiment shown in FIG. 3A and 3B show a perspective view of the slider used in the variable resistor shown in FIG. 1 before folding and a perspective view after folding.

Explanation of symbols

1 ... Substrate 1a ... Central hole (recess)
DESCRIPTION OF SYMBOLS 1b ... Convex part 2-4 ... Terminal 5 ... Resistor 6 ... Slider 6a ... Driver plate part 6b ... Engagement groove 6c ... Tongue piece 6d ... Connection part 6e ... Restriction part (cylindrical part)
6g ... Contact part 6i ... Stopper piece 6j ... Opening

  Hereinafter, specific examples of the present invention and comparative examples will be given to clarify the effects of the present invention, and specific embodiments of a variable resistor and a manufacturing method thereof will be described with reference to the drawings. I will do it.

[Experimental example i]
(Example 1)
As the carbon-based conductive powder, 9 parts by weight of graphite having a specific surface area of 12 m ² / g, an average particle diameter of 6000 nm, a specific surface area of 211 m ² / g, 2.25 parts by weight of furnace black having an average particle diameter of 21 nm, a specific surface area of 98 m ² / g, Furnace black with an average particle size of 23 nm, 2.25 parts by weight, specific surface area of 68 m ² / g, acetylene black with an average particle size of 35 nm, 9 parts by weight, and pt-butylphenol resin (pt-butylphenol) represented by the following chemical formula 1 47.5 parts by weight of a resin obtained by condensation of styrene and formaldehyde, Showa Polymer Co., Ltd., trade name: CKM-1282) and 30.0 parts by weight of diethylene glycol monobutyl ether acetate (BCA) as a solvent The resistance paste of Example 1 was obtained by kneading.

(Example 2)
Resistive paste in the same manner as in Example 1 except that the cresol resin (Dainippon Ink Chemical Co., Ltd., trade name: KA-1160) represented by the following chemical formula 2 was used as the substituted monohydric phenol resin used. Got.

(Example 3)
A resistance paste was obtained in the same manner as in Example 1 except that a xylene phenol resin represented by the following chemical formula 3 (trade name: Nicanol PR-1440) represented by the following chemical formula 3 was used as the substituted monohydric phenol resin.

(Comparative Example 1)
In place of pt-butylphenol resin as a substituted monohydric phenol resin, an epoxy resin (manufactured by Japan Epoxy Resin, bisphenol A type epoxy resin, weight average molecular weight: 900, trade name: Epicoat EP-1001) was used. A resistance paste was obtained in the same manner as in Example 1 except for.

(Comparative Example 2)
Except that instead of pt-butylphenol resin, a mixed resin of ethylstyrene-divinylbenzene copolymer (Dainippon Ink Chemical Co., Ltd., trade name: CZ-256-A) and bisphenol A type epoxy resin was used. In the same manner as in Example 1, a resistance paste was obtained.

(Evaluation of Examples 1 to 3 and Comparative Examples 1 and 2)
Each of the obtained resistance pastes was applied to a plate made of PPS (polyphenylene sulfide) by screen printing so that the thickness was 0.5 mm × 4 mm × thickness 28 μm, and heat-treated at a temperature of 180 to 300 depending on the resin used. After curing, the temperature was maintained at 150 ° C. for 3 hours, followed by baking to obtain a resistor. About each obtained resistor, while measuring resistance value, the high temperature characteristic, the moisture-proof characteristic, and the TCR characteristic were evaluated in the following ways.

  1) High temperature characteristics: A resistor formed on a substrate was held for 24 hours in a desiccator maintained at a humidity of 30%, then taken out from the desiccator, and immediately measured for a resistance value to obtain an initial resistance value. Thereafter, the resistor was held for 5 hours in a thermostat kept at 70 ° C., and then the resistance value was measured to obtain the resistance value after being left at high temperature. The variation ratio of the resistance value after standing at this high temperature with respect to the initial resistance value was determined and used as the high temperature characteristic (%).

  2) Humidity resistance: The initial resistance value was determined in the same manner as in the evaluation of the high temperature characteristics. Next, after the resistor formed on the insulating substrate was maintained for 24 hours in a thermostatic chamber maintained at 40 ° C. and 90% relative humidity, the resistance value after the moisture resistance test was measured. The variation rate of the resistance value after the moisture resistance test with respect to the initial resistance value was determined and defined as the moisture resistance property (%).

3) TCR characteristics: The resistance value of a resistor maintained at a temperature of minus 25 ° C. for 0.5 hour in a constant humidity chamber maintained at 55% relative humidity is measured, and then the temperature in the constant humidity chamber is After raising the temperature to 85 ° C. and maintaining the temperature at 85 ° C. for 0.5 hour, the resistance value at a high temperature was measured. TCR characteristics (ppm / ° C.) were determined by (R _85-25 ) / (85 − (− 25)) where R ₋₂₅ is the resistance value at ₋₂₅ ° C. and R ₈₅ is the resistance value at 85 ° C.

  The results are shown in Table 1 below.

  As is clear from Table 1, in Comparative Example 1, a resistance paste was prepared using an epoxy resin excellent in moisture resistance, so that the high temperature characteristics and moisture resistance characteristics were good, but the TCR characteristics were low. That is, it can be seen that the change in resistance value due to temperature change is very large. In Comparative Example 2, a mixture of bisphenol A and ethylstyrene-divinylbenzene copolymer was used as a phenol resin having no substituent. In this case, the moisture resistance and TCR characteristics were very poor. . Also, the high temperature characteristics were not sufficient.

  On the other hand, in Examples 1-3, it turns out that the resistor excellent in all of a high temperature characteristic, a moisture-proof characteristic, and a TCR characteristic is obtained. This is because a substituted monohydric phenol resin is used as the resin, and therefore, high temperature characteristics, moisture resistance characteristics and TCR characteristics, particularly moisture resistance characteristics and TCR characteristics, are compared with the case where a phenol resin other than an epoxy resin or a substituted monohydric phenol resin is used. By being effectively enhanced.

(Experimental example ii)
In view of the fact that good results were obtained in Experimental Example i, each of the resistance pastes a to o shown in Tables 2 and 3 was prepared in the same manner as in Example 1, and the evaluations of Examples 1 to 3 were made. In the same manner, the resistance value, the high temperature characteristic, the moisture resistance characteristic and the TCR characteristic were evaluated. However, the high temperature characteristics and moisture resistance characteristics were measured for resistance values after being held for 100 hours. The results are shown in Tables 2 and 3 below.

  As is apparent from Tables 2 and 3, it can be seen that any of samples a to o is superior in moisture resistance and TCR characteristics as compared with the case of Comparative Example 2 described above. That is, by using a pt-butylphenol resin as a resin, even when the blending ratio of the pt-butylphenol resin was changed, a resin containing another phenol resin of Comparative Example 2 was used. It can be seen that the moisture resistance and TCR characteristics can be improved compared to the case.

  In particular, in the sample symbols b to n, the blending ratio of the carbon-based conductive powder and the pt-butylphenol resin is in the range of 17.5 to 35.0 to 41.5 to 53.0 by weight ratio. It can be seen that the moisture resistance and TCR characteristics are further enhanced. In addition, a good coating film can be obtained without cracking or bleeding.

  In addition, although the sample symbol a is inferior in moisture resistance and TCR characteristics as compared with the sample symbols c to j as described above, better results are obtained than in Comparative Example 2 described above. Yes.

  In addition, it can be seen that the sample symbol o is sufficiently superior in moisture resistance and TCR characteristics as compared with the above-described Comparative Example 2, although the moisture resistance is lower than the sample symbols c to j and the high temperature characteristics are also lower.

  Therefore, as long as the carbon-based conductive powder and the substituted monohydric phenol resin are included, it is supported from the results in Tables 1 to 3 that a resistor excellent in moisture resistance and TCR characteristics can be obtained according to the present invention.

(Experimental example iii)
In Example 1, the carbon-based conductive powder was 10.7 parts by weight of graphite having a specific surface area of 12 m ² / g and an average particle diameter of 6000 nm, and 16.0 parts by weight of furnace black having a specific surface area of 211 m ² / g and an average particle diameter of 21 nm. 40.0 parts by weight of pt-butylphenol resin (resin obtained by condensation of pt-butylphenol and formaldehyde, manufactured by Showa Polymer Co., Ltd., trade name: CKM-1282), and diethylene glycol mono as a solvent In 19.7 parts by weight of butyl ether acetate (BCA), 3.6 parts by weight of any one of the following dispersants A to C and E to G are kneaded, and samples 1 to 3, 5 to 5 shown in Table 4 below are mixed. A resistance paste of 7 was obtained.

  In addition, Sample 4 shown in Table 4 below was the same as above except that the dispersant was not added and the blending ratio of BCA as a solvent was changed to 33.3 parts by weight. A resistance paste was obtained. In Table 4, in the column of the dispersant of Sample 4, the symbol D was added as a symbol indicating that no dispersant was added.

  Using the resistance paste of samples 1 to 7 prepared as described above, applying the resistance paste in the same manner as in the evaluation of Examples 1 to 3 and Comparative Examples 1 and 2, baking, obtaining a resistor, Each obtained resistor was evaluated in the same manner as in Examples 1 to 3 and Comparative Examples 1 and 2. In the evaluation, in each of the 50 resistors obtained, whether or not cracks were generated was visually observed, and the ratio (%) of the resistors having cracks was evaluated. The results are shown in Table 4 below.

In Table 4, details of the dispersants A to G are as follows.
A Partially esterified product of α-olefin / maleic anhydride copolymer (manufactured by Kyoeisha Chemical Co., Ltd., trade name: Floren G700)
B Grafted product of allyl alcohol / maleic anhydride / styrene copolymer and polyoxyalkylene monoalkyl ether (manufactured by NOF Corporation, trade name: AFB-1521)
C Aliphatic polycarboxylic acid (manufactured by Enomoto Kasei Co., Ltd., trade name: Disparon 2150)
D No additive E Amide amine salt of high molecular weight polyester acid (manufactured by Enomoto Kasei Co., Ltd., trade name: Disparon DA-703-50)
F Amine salt of high molecular polyester (manufactured by Enomoto Kasei Co., Ltd., trade name: Disparon KS-860)
G Salt of linear polyamide amide and high molecular acid polyester (manufactured by Enomoto Kasei Co., Ltd., trade name: Disparon 1860)

  As is apparent from Table 4, all of Samples 4 to 7 were excellent in high temperature characteristics, moisture resistance characteristics and TCR characteristics, but cracks were observed in the obtained resistors. That is, when no dispersant is added, cracks are observed in 80% of the resistors, and when dispersants E to G other than the polycarboxylic acid-based dispersant are added, cracks are generated in 50% of the resistors. Admitted.

  On the other hand, in Samples 1 to 3, since a polycarboxylic acid-based dispersant was used, no cracks were observed in the obtained resistors. This is because the wettability between the carbon-based conductive powder and the pt-butylphenol resin is improved by the addition of a polycarboxylic acid-based dispersant, and it is difficult for fine pores to be formed in the coating formed by applying the resistance paste. For this reason, it is considered that cracks did not occur in the obtained resistor.

  Next, specific embodiments of the variable resistor and the manufacturing method thereof according to the present invention will be described.

  1 and 2 show an embodiment of a variable resistor according to the present invention. This variable resistor is formed in a chip type that is surface-mounted on a printed circuit board. This variable resistor is composed of two parts: a substrate 1 in which fixed-side metal terminals 2 and 3 and a variable-side metal terminal 4 are integrally insert-molded, and a slider 6 that is caulked and attached to the variable-side metal terminal 4. Has been.

  In order to withstand the heat of soldering and to enable stable operation in a high humidity atmosphere, the substrate 1 is made of a heat-resistant thermoplastic resin or a thermosetting resin. For example, liquid crystal (LCP) resin, modified 6T nylon, poniphenylene sulfide (PPS) resin, polyester resin, epoxy resin, diallyl phthalate resin, and the like are used. On the upper surface of the substrate 1, the conductive portions 2a and 3a of the fixed side terminals 2 and 3 are exposed. On the upper surface of the substrate 1, the resistance paste of the present invention (see FIG. 3) is applied in a substantially arc shape so as to cover the moving portions 2 a and 3 a of the fixed side terminals 2 and 3, and is baked. Thereby, the fixed side terminals 2 and 3 and the resistor 5 are electrically connected.

  The slider 6 is made of a metal having good conductivity and spring characteristics, and is made of a thin plate such as a copper alloy, stainless steel, or a noble metal alloy. As shown in FIGS. 3A and 3B, the slider 6 is formed by integrally punching an annular driver plate portion 6a and a cup-shaped throttle portion (cylindrical portion) 6e through a connecting portion 6d. The throttle part 6e is folded to the back side of the driver plate part 6a at the connecting part 6d. The driver plate portion 6a is formed with a cross-shaped engagement groove 6b that is rotated by an adjustment jig such as a driver. One of the engaging grooves 6b is bent downward without being pulled out to form a tongue piece 6c. A semicircular arc-shaped arm portion 6f is formed on the outer peripheral edge of the throttle portion 6e opposite to the connecting portion 6d, and a contact portion 6g that elastically contacts the resistor 5 at the center of the arm portion 6f. Is formed. A fitting hole 6h that fits into the eyelet part 4a of the variable side terminal 4 is formed in the central part of the throttle part 6e, and the fitting hole 6h is fitted into the eyelet part 4a of the variable side terminal 4, The slider 6 is rotatably attached to the substrate 1 by caulking the eyelet part 4a on the outside opening. In the vicinity of the bottom of the throttle portion 6e, a stopper piece 6i is formed by cutting and raising a part of the throttle portion 6e radially outward, and this stopper piece 6i is a convex portion 1b formed inside the central hole 1a of the substrate 1. The rotation angle of the slider 6 is regulated by abutting on.

  In order to change the resistance value of the variable resistor, the adjustment jig can be adjusted by engaging the adjusting jig with the engaging groove 6b of the driver plate portion 6a and turning the slider 6. When the slider 6 is rotated to the end, the stopper piece 6 i comes into contact with one side surface of the convex portion 1 b of the substrate 2, and at this time, the contact portion 6 g of the slider 6 comes into contact with one end portion of the resistor 5. To do.

  The present invention is not limited to the above embodiments. In the above embodiment, the slider has a folding structure of the driver plate part and the throttle part (cylindrical part), but the driver plate part and the cylindrical part are integrated and adjusted to the cylindrical part as in the conventional case. An engagement groove may be formed in the jig for use. Further, the convex portion of the substrate that contacts the stopper piece and regulates the rotation angle of the slider does not need to be formed of resin. For example, the stopper claw of the variable side terminal is exposed and the slider claw is exposed to the stopper claw. You may make it contact | abut a stopper piece.

  The variable resistor according to the present invention is not limited to the structure of the above embodiment, and the method for manufacturing the variable resistor is not particularly limited. In addition, the said fixed side terminal and the variable side terminal may be previously attached to the insulated substrate like the said embodiment. That is, the step of providing the fixed side terminal and the variable side terminal on the insulating substrate is performed before the formation of the resistance film. However, the fixed terminal and the variable terminal may be formed on the insulating substrate after the antibody is formed.

Claims (7)

  A resistance paste containing carbon-based conductive powder and a substituted monohydric phenol resin.   The resistance paste according to claim 1, wherein the substituted monohydric phenol resin is a resin obtained by a condensation reaction of a substituted monohydric phenol and formaldehyde.   The resistance paste according to claim 2, wherein the substituted monohydric phenol is pt-butylphenol.   The resistance paste according to any one of claims 1 to 3, further comprising a polycarboxylic acid-based dispersant.   The carbon-based conductive powder and the substituted monohydric phenol resin are contained in a weight ratio of 17.5 to 35.0: 41.5 to 53.0. The resistance paste according to any one of the above.   A substrate provided with a resistor on the upper surface, a fixed side terminal and a variable side terminal provided on the substrate, and a contact portion that is slidably disposed on the substrate and slidably contacts the resistor. The slider is electrically connected to the variable side terminal, and the resistor is made of the resistance paste according to any one of claims 1 to 5. Variable resistor. Applying the resistive paste according to any one of claims 1 to 5 on an insulating substrate;
Baking the applied resistive paste to form a resistor;
Providing a fixed terminal and a variable terminal on the insulating substrate;
And a step of attaching a slider that is slidably in contact with the resistor and is electrically connected to the variable terminal to the insulating substrate. Production method.

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