JP2000067646A - Conductive paste - Google Patents

Abstract

(57) [Problem] To provide a conductive paste whose resistance change is suppressed and which can be used for manufacturing a conductor and a resistor excellent in abrasion resistance. SOLUTION: The non-conductive material has a Mohs hardness of 5 or more, a major axis length in a range of 0.15 to 0.4 µm, and a ratio of the major axis length to a minor axis length in a range of 10 to 40. Powder and
By mixing the conductive powder, the binder, and the solvent, a conductive paste is obtained. In the solid content of the conductive paste, the content of the non-conductive powder is preferably in a range of 5 to 15% by weight. Further, as the non-conductive powder, iron oxide, titanium oxide, iron hydroxide and the like can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste used for producing, for example, an electric resistor film, an electric conductor film and the like.

[0002]

2. Description of the Related Art Conventionally, a conductive paste is usually prepared by kneading a conductive powder, a non-conductive powder and a binder in the presence of a solvent. An electric resistor film and an electric conductor film are manufactured. The types and contents of the conductive powder and the binder are not particularly limited, and are appropriately determined according to, for example, a desired resistance value of the electric resistor film or the like. Usually, as the conductive powder, conductive carbon black, gold, silver, copper, nickel, palladium, powder of aluminum or the like, or an alloy powder of these metals is used, as the binder resin as the binder Thermosetting resins such as phenol formaldehyde resin, xylene-modified phenol resin, epoxy resin, melamine resin, and acrylic resin are used.

However, in recent years, there has been an increasing demand for heat resistance of the electric resistor film and the like in order to cope with the use of the electric resistor film and the like in a high temperature environment and an increase in the amount of heat generated by downsizing and increasing the capacity of the element. ing.

[0004]

However, when a resistor film, a conductor film, or the like prepared using the conventional conductive paste as described above is used in a high-temperature environment, the curing reaction of the binding resin is not performed. There was a problem that the resistance value was unstable due to progress and deterioration.

[0005] Further, by sliding using an electrode brush or the like,
Since the problem of wear of the resistor film or the like occurs, the wear resistance is improved by adding a non-conductive inorganic filler. However, the conductive paste to which the non-conductive inorganic filler is added as described above can improve the wear resistance of the resistor film and the like, but on the other hand, the wear amount of the electrode brush and the like increases, and as a result, Another problem is that the life of elements such as resistors is shortened.

[0006] Therefore, an object of the present invention is to provide a conductive paste capable of producing a resistor, a conductor, or the like with a small change in resistance value and with reduced wear due to sliding.

[0007]

In order to achieve the above object, a conductive paste of the present invention is a conductive paste containing a conductive powder, a non-conductive powder, a binder and a solvent. Mohs hardness is 5 or more, the major axis length is 0.15 to 0.4 μm, and the ratio of the major axis length to the minor axis length (hereinafter, also referred to as “needle ratio”) is 10 to 4
It is characterized by being 0.

[0008] The conductive paste of the present invention contains a non-conductive powder having such physical properties and shape (hereinafter also referred to as "acicular non-conductive powder"), so that it can be used, for example, under high temperature conditions. Also, it is possible to obtain a conductor, a resistor, or the like with a small change in the resistance value. According to the study of the present inventors,
When the acicular non-conductive powder as described above is used as the material for the conductive paste, the non-conductive powder reinforces the binder due to the heat of the use environment, which causes the binder to cure and shrink or deteriorate to change its dimensions. It is presumed that it exerts an effect and that this can reduce the change in the resistance value. Further, usually, when the strength of the conductor or the like is increased in order to improve the wear resistance against sliding, on the other hand, there is a fear that the wear of the electrode brush or the like may be advanced. However, according to the conductive paste of the present invention, by setting the Mohs hardness of the non-conductive powder to 5 or more, the obtained conductor has sufficient strength,
By setting the major axis length and the needle ratio in the above-described range, the abrasiveness of the electrode brush (that is, the wear of the electrode brush) can be suppressed. By using such a conductive paste of the present invention, it is possible to manufacture a conductor, a resistor, or the like, which is hardly damaged, prevents abrasion of an electrode brush or the like, and suppresses a change in resistance during use.

The Mohs hardness of the non-conductive powder is 5 to 5.
The range of 7.5 is more preferred, and particularly preferred is 5 to 5.
6.5.

[0010] The major axis length of the non-conductive powder is 0.2 to
A range of 0.3 μm is more preferable. The major axis length is equal to 0.
If it is 15 μm or more, the reinforcing effect is exhibited, but 0.4 μm
If it exceeds m, for example, the abrasion of the conductor film itself becomes large, and the abrasion of the electrode brush may progress.

The needle ratio of the non-conductive powder is 10 to 30.
Is more preferable. When the acicular ratio is less than 10, the short axis length of the non-conductive powder increases, and the abrasion of the electrode brush may progress. On the other hand, if the acicular ratio is larger than 40, the non-conductive powder may be easily broken during kneading and dispersing with a binder resin or a conductive powder, and it may be difficult to maintain the acicular shape.

The Mohs hardness can be measured by a conventional Mohs hardness meter.

The method of measuring the major axis length and the minor axis length of the non-conductive powder is not particularly limited. For example, an electron micrograph of the non-conductive powder may be taken and measured.

In the conductive paste of the present invention, the content of the non-conductive powder in the solid content is preferably in the range of 5 to 15% by weight, more preferably 5 to 15% by weight.
In the range of 10 to 10% by weight.

In the conductive paste of the present invention, the type of the non-conductive powder is not particularly limited as long as it has the above-mentioned physical properties. For example, the non-conductive powder may be iron oxide or iron hydroxide. , Titanium oxide, silicon carbide, silicon nitride,
It is preferably at least one metal powder selected from the group consisting of potassium titanate, aluminum borate, basic magnesium sulfate, β-wollastonite and zonotolite. In addition to these, for example,
The non-conductive powder may use at least one fiber selected from the group consisting of glass fiber, carbon fiber, aramid fiber, and boron fiber. The non-conductive powder may be one type as long as the above-mentioned conditions are satisfied,
Two or more types may be used in combination. In addition, as long as the function of the conductive paste of the present invention is not impaired, other non-conductive substances may be contained in addition to the non-conductive powder.

In the conductive paste of the present invention, the binder is not particularly limited, and can be appropriately determined according to the intended properties of the conductor and the like. As the binder,
For example, a thermosetting resin such as a phenol resin, an epoxy resin, a melamine resin, and an acrylic resin can be used. Preferably, because it is excellent in heat resistance, it is a polyimide precursor, more preferably among the polyimide precursor,
Excellent solvent solubility, when used for conductive paste,
Because of its excellent printing characteristics, its weight average degree of polymerization n is 5
The polyimide precursor ranges from の 20 to ２０20.

The weight-average degree of polymerization is determined, for example, by measuring the weight-average molecular weight of the polyimide precursor by gel permeation chromatography (GPC) analysis, and dividing the value of the weight-average molecular weight by the molecular weight per constituent repeating unit. Can be obtained by The GPC analysis includes, for example,
GL-S300MDT-5 (manufactured by Hitachi Chemical Co., Ltd.) was used as a GPC column, a dimethylformamide solution containing 60 mM phosphoric acid and 30 mM lithium bromide was used as an eluent, and the polyimide precursor was used under the conditions of a flow rate of 1 ml / min. And elution of this with a differential refractometer.

Examples of the polyimide precursor having a weight-average degree of polymerization in the range of 5 to 20 include, for example, a compound having a repeating unit whose chemical structure has at least three aromatic rings in the straight chain.
And those having at least one ether bond per three aromatic rings for bonding aromatic rings can be used. That is, for example, if the number of aromatic rings per structural repeating unit is 3 or more and less than 6, the number of ether bonds is 1 or more per structural repeating unit, and if the number of aromatic rings is 6 or more and less than 9, the number of ether bonds is Is preferably two or more per constitutional repeating unit. The position of the ether bond bonding the aromatic rings to each other is not particularly limited. For example, even if the ether bond has two or more ether bonds, the ether bond may have an ether bond at any position in the structural repeating unit. (That is, in the constitutional repeating unit, the ether bond may be continuously provided on a straight chain or may be provided at a remote place). A polyimide precursor having a structural repeating unit having such a chemical structure has a relatively high ratio of ether bonds in the polyimide precursor molecule, and this ether bond gives a folded structure in the molecule of the polyimide precursor. Therefore, the interaction between molecules is reduced. For this reason, the solvent solubility of the polyimide precursor can be further improved, and the solution viscosity can be reduced, which is useful for a conductive paste.

Specific examples of the polyimide precursor having the above weight average polymerization degree are shown below. For example, a polyimide precursor composed of a structural repeating unit having at least one of the chemical structure represented by the chemical formula (Formula 1) and the chemical structure represented by the chemical formula (Formula 2) can be used. The chemical structures shown in the above formulas (Formula 1) and Formula (Formula 2) are related to isomers, and the ratio of each isomer in the polyimide precursor is not particularly limited. Hereinafter, the polyimide precursor having such a structure is referred to as “polyimide precursor A”.

Further, for example, a structural repeating unit having at least one of the chemical structure represented by the chemical formula (Chemical formula 3) and the chemical structure represented by the chemical formula (Chemical formula 4), and a chemical compound represented by the chemical formula (Chemical formula 5) A polyimide precursor having a structure and a structural repeating unit that is a chemical structure of at least one of the chemical structures represented by the above formula (Formula 6) can also be used.
Hereinafter, the polyimide precursor having such a structure is referred to as “polyimide precursor B”.

In the weight average degree of polymerization of the polyimide precursor B, the ratio of the structural repeating unit having at least one of the chemical structure represented by the formula (Chemical formula 3) and the chemical structure represented by the formula (Chemical formula 4) But more than 25% 1
And the proportion of the structural repeating unit that is at least one of the chemical structure represented by the formula (Chem. 5) and the chemical structure represented by the formula (Chem. 6) is greater than 0% and 75%. % Is preferable. For example, the weight average degree of polymerization n of the polyimide precursor B is 10, the ratio of the constitutional repeating units represented by the formulas (Chem. 3) and (Chem. 4) is 40%, and the formulas (Chem. 5) and (Chem. The proportion of the structural repeating unit shown in Chemical formula 6) is 6
In the case of 0%, the number of repeats (degree of polymerization) of the structural repeating units represented by the formulas (Chem. 3) and (Chem. 4) in the polyimide precursor B1 molecule is 4, and the formulas (Chem. 5) and (Chem. This means that the number of repetitions of the structural repeating unit shown in 6) is 6. In addition, in this polyimide precursor B, the polymerization order of each structural repeating unit is not particularly limited. Further, the chemical structures represented by the formulas (Chem. 3) and (Chem. 4) and the chemical structures represented by the formulas (Chem. 5) and (Chem. 6) are isomers, respectively, and the polyimide precursor In B, the ratio between these isomers is not particularly limited.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The conductive paste of the present invention contains, for example, the above-mentioned non-conductive powder, conductive powder, binder and solvent as described above.

As described above, the non-conductive powder has a Mohs hardness of 5 or more and a major axis length of 0.15 to 0.4.
μm, and the ratio between the major axis length and the minor axis length is 10 to 10 μm.
A range of 40 is sufficient. Further, as a raw material of the non-conductive powder, metal powders and fibers as described above can be used,
Among them, iron oxide and iron hydroxide are preferable, and iron hydroxide is particularly preferable.

As the conductive powder, for example, conductive carbon black, gold, silver, copper, nickel, palladium, aluminum and the like, and alloy powders of these metals can be used. One type of these metal powders may be used, or two or more types may be used in combination.

The solvent is not particularly limited and is appropriately determined depending on the type of each material used, its content, and the like. Examples of the solvent that can be used include a polar solvent, a nonpolar solvent, and a mixed solvent of the polar solvent and the nonpolar solvent.

Examples of the polar solvent include N-methyl-2-pyrrolidone, N, N-dimethylsulfoxide,
N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, hexamethylenephosphamide, butyrolactone, propylene carbonate and the like can be used. As the non-polar solvent, for example, diethylene glycol dimethyl ether, diethylene glycol methyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, isophorone, diacetone alcohol, dimethyl succinate, dimethyl glutarate And dimethyl adipate. When used as a mixed solvent, the combination of the polar solvent and the non-polar solvent and the mixing ratio thereof are not particularly limited, and these solvents are
Two or more types may be used in combination.

For example, when the binder is a polyimide precursor having the weight average polymerization degree, a mixed solvent of the polar solvent and the non-polar solvent is preferable, and the mixing ratio is 10: 0 to 0.5: It is preferably in the range of 9.5, more preferably in the range of 7: 3 to 1: 9, and particularly preferably in the range of 5: 5 to 1: 9. Further, in the case of the polyimide precursor having the weight average polymerization degree, among the mixed solvents,
A mixed solvent of N-methyl-2-pyrrolidone and diethylene glycol dimethyl ether is preferred.
The mixing ratio of 2-pyrrolidone and diethylene glycol dimethyl ether is, for example, preferably in a range of 2: 8 to 9: 1 by volume, more preferably 2: 8 to 7: 3.
And particularly preferably in a volume ratio of 2: 8 to 3: 7.
Range.

The conductive paste of the present invention may contain, for example, various additives as other components in addition to the non-conductive powder, the conductive powder, the binder and the solvent.

As the additives, for example, an antifoaming agent, a coupling agent, a dispersant and the like can be used.
There is no particular limitation as long as the function of the conductive paste of the present invention is not impaired.

The binder is not particularly limited, and various resins as described above can be used. The binder may be used alone or in combination of two or more.

The binder can be, for example, a commercially available binder or can be produced by a conventional method.

For example, the method for producing the polyimide precursor is not particularly limited, and it can be produced by a conventional method. less than,
Using oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether as raw materials, the weight average degree of polymerization n
1 shows an example of a method for producing a polyimide precursor A having 5 to 6.

For example, a reaction flask equipped with a cooling condenser, a thermometer, a stirrer, a gas injection pipe, and the like is
Mixed solvent of N, N-dimethylacetamide and diethylene glycol monomethyl ether (weight ratio 6: 4 to 5:
5) and the first raw material oxydiphthalic anhydride are added in a weight ratio of 10: 1 to 12: 1. Then, nitrogen gas is sealed in the flask, and the solvent and the first raw material are stirred and dissolved in a nitrogen atmosphere at a temperature of 40 to 50 ° C. After dissolution, it is cooled and the temperature is about 10 ° C.
The second raw material 4,4′-diaminodiphenyl ether is added to the melt under the conditions of (1) and (2) in a weight ratio of 98: 100 to 99: 100 with respect to the first raw material. And after aging these at room temperature for about 20 hours,
Pour into ice water to precipitate solids. The obtained solid is pulverized, and the powder is immersed in a methanol / water solvent having a volume ratio of 9: 1 to 5: 5 for about 15 hours. Then, the powder is filtered and dried using a drier. Dry at a temperature of about 80 ° C. By such a method, a polyimide precursor A having a weight average degree of polymerization n of 5 to 6 can be produced. In particular,
By using 1500 g of N, N-dimethylacetamide, 186 g of oxydiphthalic anhydride and 118 g of 4,4′-diaminodiphenyl ether under the above-mentioned conditions, a polyimide precursor A having a weight average polymerization degree n of 5 to 6 is obtained.
About 300 g can be obtained. The weight average degree of polymerization can be adjusted, for example, by changing the mixing ratio of the mixed solvent under the above conditions. Specifically, for example, the degree of polymerization can be increased as the content of N, N-dimethylacetamide in the mixed solvent is increased.

For the polyimide precursor B, for example, oxydiphthalic anhydride, 4,4′-diaminodiphenyl ether, and pyromellitic dianhydride can be used as raw materials. 99: 1
The range is 1:99:99. The method for producing the polyimide precursor B is not particularly limited, and for example, can be produced in the same manner as the above-mentioned method for producing the polyimide precursor A. In the case of having two types of structural repeating units (excluding isomers) as in the case of the polyimide precursor B, the ratio of the two structural repeating units may be determined, for example, by performing mass spectrometry and analyzing the ratio of the carbon element or the hydrogen element to the nitrogen element. It can be determined from the molar ratio.

Next, in the production of the conductive paste of the present invention, for example, the non-conductive powder, the conductive powder, the binder and the solvent are kneaded and mixed using a three-roll mill, a sand mill or the like. Can be manufactured.

In the conductive paste of the present invention, the mixing ratio of the non-conductive powder to the solvent is not particularly limited, but is, for example, preferably in the range of 4 to 27 parts by weight, more preferably 100 parts by weight of the solvent. Ranges from 4 to 9 parts by weight.

The mixing ratio of the conductive powder is not particularly limited, but is, for example, 180 to 640 parts by weight, preferably 300 to 640 parts by weight, based on 100 parts by weight of the non-conductive powder. Range of parts.

The mixing ratio of the binder is not particularly limited, but is, for example, in the range of 360 to 1280 parts by weight, preferably 600 to 1280 parts by weight, per 100 parts by weight of the non-conductive powder. Range.

As a method of using the conductive paste of the present invention, for example, the conductive paste is screen-printed on an insulating substrate on which electrodes are formed, dried, and then dried at a temperature of 270 to 350 ° C. for 1 to 2 times. A heat treatment may be performed for a time, and the composition may be cured.

[0040]

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

Example 1 Using various nonconductive powders,
A conductive paste was prepared. Then, a conductor sample was prepared using this, and various characteristics thereof were examined. The materials used, the composition ratio of the conductive paste, the method for preparing the conductive paste and the conductive sample, and the method for measuring various characteristics are described below.

(Binder) Phenol resin (Mirex XL-225, manufactured by Mitsui Chemicals, Inc.)

(Conductive powder) Carbon black (Acetylene black manufactured by Denka Kogyo Co., Ltd.)

(Solvent) Isophorone

(Non-conductive powder) Needle-shaped non-conductive powder A: α-iron oxide (major axis length 0.15μ)
m, needle ratio 10, Mohs hardness 5.5 to 6.5) needle non-conductive powder B: γ-iron oxide (major axis length 0.40 μm)
m, needle-like ratio 15, Mohs hardness 6) Needle-like non-conductive powder C: iron hydroxide (major axis length 0.3 μm, needle-like ratio 30, Mohs hardness 5)

(Composition ratio of conductive paste) Binder (solid) 100 parts by weight Carbon black 50 parts by weight Solvent 190 parts by weight Various nonconductive powders Predetermined amounts shown in Table 1 below

The amount of the non-conductive powder shown in Table 1 below is the content of the non-conductive powder in the solid content of the conductive paste. 10
The content (% by weight) of the non-conductive powder when 0% by weight is used.

(Method for Preparing Conductive Paste) The above-mentioned materials were blended so as to have the above-mentioned composition ratio, and these were kneaded and dispersed using a three-roll mill.

(Preparation Method of Conductor Sample) Each conductive paste was screen-printed (small general-purpose screen printer MR-60, Sakurai) on a ceramic insulating substrate in which silver paste was previously baked to form electrodes. (Graphics Systems) and a 200-mesh screen and dried. The printing step and the drying step were repeated to make the thickness of the conductive paste printed film after drying 10 ± 1 μm, and then cured at 350 ° C. for 1 hour to obtain a conductor sample.

(Measurement of Resistance Value) The initial resistance value of the conductor sample and the resistance value of the conductor sample after the heat treatment were measured, and the rate of change in the resistance value after the heat treatment (resistance reduction rate) was determined. . The measurement of the resistance value, the electrode portion of the conductor sample,
Tester (Digital Multimeter VP-2662A:
(Manufactured by Matsushita Electric Industrial Co., Ltd.).
The resistance value after the heat treatment was as follows.
For 500 hours and left for 30 minutes, and then measured in the same manner as described above. The results are shown in Table 1 below.

(Sliding Test) A copper slider (brush) was applied to the surface of each conductor sample, and the brush was slid reciprocally 10,000 times. The sliding condition is as follows.
m × 0.5 mm, load 150 g. Thereafter, the depth of the sliding trajectory of the conductor sample was measured using a contact type surface roughness meter (Talysurf: manufactured by Rank Taylor Hobson). When the depth of the sliding trajectory is 0.5 μm or less, ○, and when the depth is larger than 0.5 μm and 2 μm or less, Δ
When it exceeded μm, it was evaluated as x. The results are shown in Table 1 below.
Shown in The degree of wear of the brush after sliding was determined by measuring the brush sliding portion with an electron microscope (scanning electron microscope JSM5200L).
V: manufactured by JEOL Ltd.), and the length reduced in the direction perpendicular to the sliding surface of the brush sliding portion relative to the length before sliding was measured. Said reduced length is 0.2μ
When the particle size is less than m, the evaluation was ○, when the value was more than 0.2 μm and 0.5 μm or less, the evaluation was Δ, and when it exceeded 0.5 μm, the evaluation was ×. The results are shown in Table 1 below.

Comparative Example 1 A conductive paste was prepared in the same manner as in Example 1 except that the following various nonconductive powders were used as the nonconductive powder. Using these, a conductor sample was prepared in the same manner as described above, and various characteristics of the conductor sample were examined. The results are shown in Table 1 below.

(Non-conductive powder) Non-conductive powder D: α-alumina (particle size 0.2 μm)
m, Mohs hardness 8) Acicular non-conductive powder E: γ-iron oxide (major axis length 0.4 μm,
Acicular ratio 8, Mohs hardness 6) Non-conductive powder F: silica powder (particle diameter 0.2 μm,
Mohs hardness 5) Non-conductive powder G: calcium carbonate (particle size 0.2μ)
m, Mohs hardness 2)

The amount (content) of non-conductive powder added
Is as shown in Table 1 below.

Comparative Example 2 A conductive paste was prepared in the same manner as in Example 1 except that no nonconductive powder was added.
A conductor sample was prepared in the same manner as described above. Then, various characteristics of the conductor sample were examined. The results are shown in Table 1 below.

[0056]

[Table 1]

Example 2 A conductive paste and a conductive sample were prepared in the same manner as in Example 1 except that the following polyimide precursor was used as a binder and the following mixed solvent was used as a solvent. . Various characteristics of these conductor samples were examined in the same manner as described above. The results are shown in Table 2 below.

(Binder) Polyimide precursor B (weight-average degree of polymerization n = 5 to 6) The polyimide precursor B has the weight-average degree of polymerization shown in the above formulas (3) and (4). The proportion of the constitutional repeating unit is 40%, and the proportion of the constitutional repeating units represented by the formulas (Chem. 5) and (Chem. 6) is 60%.

(Solvent) Mixed solvent of N-methyl-2-pyrrolidone and diethylene glycol dimethyl ether (7: 3 by volume)

Comparative Example 3 A conductive paste was prepared in the same manner as in Example 2 except that the same non-conductive powder as in Comparative Example 1 was used. Then, a conductor sample was prepared using these conductive pastes, and in the same manner as described above,
Various characteristics of the conductor sample were examined. The results are shown in Table 2 below.

(Comparative Example 4) A conductive paste was prepared in the same manner as in Example 2 except that no non-conductive powder was added.
A conductor sample was prepared in the same manner as described above. Then, various characteristics of the conductor sample were examined. The results are shown in Table 2 below.

[0062]

[Table 2]

As shown in Tables 1 and 2, the conductor samples of Examples 1 and 2 were mixed with the non-conductive powders of Comparative Examples 2 and 4 by adding the various non-conductive powders. It was found that a smaller resistance value change rate was obtained as compared with each conductor sample to which no conductive powder was added, and a stable resistance value could be maintained. Furthermore, since the conductive sample had sufficient strength, the conductive member was not damaged by sliding and the sliding brush was not worn.
In addition, since each of the conductor samples of Example 1 and Example 2 had an appropriate cleaning property, no stain was attached to the sliding brush.

On the other hand, in Comparative Examples 1 and 3, the conductive samples using the particulate nonconductive powders D and F showed little damage due to sliding, but the sliding brush had a small amount of wear. It was large, and no improvement in the rate of change in resistance was observed in each of the conductor samples without the addition of the non-conductive powder in Comparative Examples 2 and 4. The conductor sample to which the non-conductive powder E having an acicular ratio of 8 was added had a small rate of change in resistance and was not damaged, but the abrasion of the sliding brush was large. The conductor sample using the non-conductive powder G having a low Mohs hardness did not show any improvement in the rate of change of the resistance value, and showed large damage due to sliding. Although the sliding brush was not abraded, the sliding brush was not sufficiently cleaned and was very dirty. It is presumed that the powder such as the non-conductive powder G deteriorates the strength of the coating film only by increasing the ratio between the powder and the resin in the conductor sample.

[0065]

As described above, according to the conductive paste of the present invention containing the non-conductive powder having the above-described physical properties and shape, a change in resistance value is suppressed and a conductor excellent in wear resistance is obtained. be able to.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01C 7/00 H01C 7/00 J (72) Inventor Masao Hasegawa 1006 Kazuma Kazuma, Kadoma, Osaka Matsushita Electric Within Sangyo Co., Ltd. (72) Inventor Toshiyuki Kitagawa 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A conductive paste containing a conductive powder, a non-conductive powder, a binder and a solvent, wherein the non-conductive powder has a Mohs' hardness of 5 or more and a major axis length of 0.
A conductive paste having a range of 15 to 0.4 μm and a ratio of the major axis length to the minor axis length of 10 to 40. 2. The solid content of the conductive paste, wherein the content of the non-conductive powder is in the range of 5 to 15% by weight.
4. The conductive paste according to claim 1. 3. The non-conductive powder comprises iron oxide, iron hydroxide, titanium oxide, silicon carbide, silicon nitride, potassium titanate, aluminum borate, basic magnesium sulfate, β
The conductive paste according to claim 1 or 2, wherein the conductive paste is at least one metal powder selected from the group consisting of wollastonite and zonotolite. 4. The conductive paste according to claim 1, wherein the non-conductive powder is at least one fiber selected from the group consisting of glass fiber, carbon fiber, aramid fiber, and boron fiber. 5. The binder according to claim 1, wherein the binder is at least one thermosetting resin selected from the group consisting of a phenol resin, an epoxy resin, a melamine resin, and an acrylic resin.
5. The conductive paste according to any one of items 4 to 4. 6. The conductive paste according to claim 1, wherein the binder is a polyimide precursor, and the weight average degree of polymerization (n) is in the range of 5 to 20. 7. The chemical structure of the constituent repeating unit of the polyimide precursor has at least three aromatic rings in the straight chain thereof, and at least one ether bond per three aromatic rings per aromatic ring. The conductive paste according to claim 6, which has the above ratio. 8. The polyimide precursor is composed of a structural repeating unit having at least one of the chemical structure represented by the following chemical formula (Chemical formula 1) and the chemical structure represented by the following chemical formula (Chemical formula 2). Or the conductive paste according to 7. Embedded image Embedded image 9. A polyimide precursor comprising a structural repeating unit having at least one of a chemical structure represented by the following chemical formula (Chem. 3) and a chemical structure represented by the following chemical formula (Chem. 4): 8. The conductive paste according to claim 6, comprising a structural repeating unit having at least one of a chemical structure represented by the following chemical formula and a chemical structure represented by the following chemical formula (6). Embedded image Embedded image Embedded image Embedded image 10. A ratio of a structural repeating unit having at least one of the chemical structure represented by the formula (Chem. 3) and the chemical structure represented by the formula (Chem. 4) in the weight average polymerization degree of the polyimide precursor. But 25% or more 100
%, And the ratio of the structural repeating unit which is the chemical structure represented by the chemical formula (Chem. 5) or at least one of the chemical structures represented by the formula (Chem. 6) is 0.
The conductive paste according to claim 9, wherein the range is more than 75% and less than 75%.