JPH0636902A - Polymer base resistor paste - Google Patents

Abstract

PURPOSE:To manufacture the title polymer base resistor paste having excellent, slidableness and slipperiness, neither fluctuating the resistance value by oxidation nor causing any defective insulation at all due to silver migration by making use of a mixture particles comprising copper alloy particles and carbon particles. CONSTITUTION:The title polymer base resistor paste is composed of 100wt.% of conductive particles comprising copper alloy particles and 5-100wt.% of an organic binder. At this time, the mean composition of this copper alloy particles is to be AgxCu1-x (where, 0.01<=x<=0.4, x representing atomic ratio) while the silver concentration on the copper alloy particle surface is larger than the mean silver concentration furthermore having the region wherein the silver concentration is to be gradually increased from outside to the surface. Through these procedures, the title polymer base resistor having excellent slipperiness, slidableness and lower resistance value neither fluctuating the resistance value nor causing any defective insulating at all due to silver migration can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer type resistor paste. More specifically, it relates to a polymer type resistor paste having excellent oxidation resistance, migration resistance and abrasion resistance.

[0002]

2. Description of the Related Art Conventionally, carbon, carbon and nickel, have been used as conductive powder of polymer type resistor paste.
A mixed powder of aluminum, copper, silver, a stainless steel alloy, and a silver-plated composite powder is used, and a resistor paste in which these conductive powders are dispersed by adding an organic binder, if necessary, a solvent and an additive is known. is there.

Carbon used as a known resistor paste, and carbon and nickel, aluminum,
The mixed powder of copper, silver, stainless alloy, and silver-plated composite powder has the following drawbacks. When carbon is used alone, it is inexpensive and its resistance value changes little with time, but its conductivity is low, and a resistor having a low resistance value cannot be produced. It also has the drawback of low sliding resistance. Even when a conductive powder obtained by mixing one or more kinds of aluminum and stainless alloy with carbon is used, the conductivity is low and a resistor having low resistance cannot be produced. On the other hand, silver has high conductivity and good oxidation resistance. Therefore, when a mixed powder of carbon and silver is used, a resistor with low resistance and small change in resistance over time can be produced. In particular, it has a drawback that silver easily migrates under high humidity and easily causes insulation failure. The same applies to silver-plated composite powder. copper,
Nickel has poor oxidation resistance, and oxidation causes an increase in resistance value.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a resistor paste which does not cause a change in resistance value due to oxidation, does not cause insulation failure due to silver migration, and is capable of producing a resistor having excellent slidability and slidability. provide.

[0005]

According to the present invention, a copper alloy powder having excellent conductivity, long-term oxidation resistance, and silver migration resistance is mixed with carbon powder, and a polymer using the mixed powder is used. The present invention relates to a mold resistor paste. That is, the present invention is as follows. 1. Conductive powder 100 composed of copper alloy powder and carbon powder
In a polymer type resistor paste having 5 to 100 parts by weight of an organic binder with respect to parts by weight, the average composition of the copper alloy powder is Ag _x Cu _1-x (where 0.01 ≦ x ≦ 0.
4, x represents an atomic ratio), and the silver concentration on the surface of the copper alloy powder is higher than the average silver concentration, and has a region where the silver concentration gradually increases from the inside to the surface. Polymer type resistor paste. 2. 1. The silver concentration on the surface of the copper alloy powder is 2.
It is 1 time or more, The polymer type resistor paste of Claim 1 characterized by the above-mentioned. 3. The weight ratio of the copper alloy powder to the carbon powder is 10: 1 to 1: 1.
3. The polymer type resistor paste according to claim 1, wherein the polymer type resistor paste is in the range of 100. 4. The average particle diameter of the copper alloy powder is 0.1 μm to 100 μm.
4. The polymer resistor paste according to claim 1, wherein the polymer resistor paste is m and has a spherical shape, a scaly shape, or a mixture thereof.

The copper alloy powder used in the present invention is produced by the high pressure atomizing method.
The high pressure water atomizing method is preferred. Silver and copper are mixed in a composition ratio to be prepared, and melted by using high frequency induction heating in a crucible in an inert gas atmosphere. Further, the melt is jetted into the inert gas atmosphere from the tip of the crucible. At the same time as jetting, a high-speed airflow generated by adiabatic expansion of a high-pressure inert gas is jetted toward the melt, atomized, and rapidly cooled and solidified. Cooling rate for rapid solidification of melt is 100 ℃
/ Sec or more is preferable, and 10000 ° C./sec or more is more preferable. As used herein, the inert gas means a gas that reacts with the melt having such a composition at all or very slowly. For example, nitrogen, helium, argon, a mixture thereof and the like can be mentioned.

The gas pressure (before expansion) is 70 kg / cm.
² G or more is preferable, and 100 kg / cm ² G or more is more preferable. The velocity of the high-speed air flow is 1 at the collision position with the melt.
00 m / sec is preferable, and 600 m / sec or more is more preferable. The mass ratio of the gas to the melt is preferably 2 or more, more preferably 4 or more. In the high pressure water atomizing method, the melt is jetted from the tip of the crucible. Simultaneously with the jetting, pressurized water is jetted from the nozzle toward the melt jetted from the tip of the nozzle, collides with the melt, becomes fine particles, and is rapidly solidified. At this time, it is more preferable that the water mass velocity / melt mass velocity ratio is 10 or more. The velocity of water at the collision position between water and the melt is preferably 80 m / sec, and
100 m / sec is preferred. The pressure at which the pressurized water is ejected from the tip of the nozzle is preferably 50 kg / cm ² G or more, more preferably 100 kg / cm ² or more.

The rapidly solidified powders produced by water atomization include many irregularly shaped powders, but they fall within the category of spherical powders in the present invention. In this case, the major axis of each particle is the particle diameter of each particle. Ag _x Cu of the present invention
_{The 1-x} copper alloy powder has 0.01 ≦ x ≦ 0.4 (atomic ratio), but if x is less than 0.01, conductivity and oxidation resistance equivalent to silver cannot be obtained, and x is 0. No more than 4 silver is needed. It is preferably 0.01 ≦ x ≦ 0.25, and more preferably 0.01 ≦ x ≦ 0.2.

The copper alloy powder of the present invention has a region where the silver concentration gradually increases toward the surface. The silver concentration on the surface is 2.1 times or more the average silver concentration, but is preferably 3 times or more and 20 times or less, more preferably 6 times or more and 15 times or less.
The silver concentration on the surface and near the surface was measured by the following method using XPS (X-ray photoelectron spectroscopy analyzer). Apparatus: XSAM800 manufactured by KRATOS, Inc. Sample: A double-sided adhesive tape was attached to a sample stand, and sample powder was attached so as to completely cover the double-sided adhesive tape. Etching conditions; pressure inside the apparatus 10 ^-7 torr, acceleration voltage 3
The argon ion beam was irradiated for 10 minutes each time using KeV and an incident angle of 45 ° with respect to the sample surface. Measurement conditions: Kα ray of magnesium (voltage: 12 KV, current: 10 mA) was incident, the photoelectron take-out angle was 90 ° with respect to the sample surface, and the apparatus internal pressure was 10 ⁻⁸ torr. The silver concentration was measured, and then the etching was repeated 5 times, and the average of the first 2 measurements was used as the surface silver concentration.

The average silver concentration was measured by dissolving the sample in concentrated nitric acid and using IPC [high frequency inductively coupled plasma emission spectrometer JY-48P manufactured by Seiko Denshi KK]. The average particle size of the copper alloy powder used in the present invention is
0.1 to 100 μm, but if spherical, 1 to 30
μm is preferable, and 1 to 20 μm is most preferable. In the case of a scaly form, the average diameter (the average value of both when there is a long diameter and a short diameter) is preferably 1 to 100 μm, and 1 to 30 μm
Is more preferable. When it exceeds 100 μm, printability and viscosity are poor, and when it is less than 0.1 μm, contact resistance increases and conductivity decreases. The shape may be spherical, scaly or a mixture thereof. The scale-like powder preferably has a diameter / thickness of 3 or more. A scanning electron microscope was used to measure the shape and particle size, and the average value of the measured values of 100 powders in the visual field was used.

In order to obtain the flaky powder, it is preferable to mechanically deform the copper alloy powder of the present invention by a known method. For example,
A method such as a stamp mill, a ball mill, and a vibration type ball mill is preferable. Above all, it is preferable to use a vibrating ball mill. As the carbon powder in the present invention, natural gas, spherical fine powder produced by vapor phase decomposition or incomplete combustion of hydrocarbon gas, or chain carbon powder, so-called carbon black, naturally produced hexagonal crystalline carbon, or Any of the so-called graphite powder obtained by industrially heating anthracite, pitch, etc. at high temperature in an arc furnace can be used,
A mixture of both may be used. Examples of carbon black include channel black, furnace black, thermal black, lamp black and the like, and any of them can be used, but channel black and furnace black having a small particle size are preferable. Further, when expressed by the iodine adsorption amount which is a measure of the specific surface area, the range of 120 mg to 320 mg is particularly preferable. Further, in the DBP (dibutyl phthalate) oil absorption used as an index of the degree of development of the structure of carbon fine powder, 20 ml / 100 g to 160
A range of ml / 100 g is particularly preferable.

As the graphite powder, either artificial graphite or natural graphite can be used. The shape may be any of scale, grain, lump, and soil, but scale and grain are particularly preferable. The particle size of the carbon powder is preferably 0.1 to 100 μm, and particularly preferably 0.1 to 50 μm. The amount of non-volatile impurities or volatile impurities contained in the carbon powder is preferably less than 1 part by weight based on 100 parts by weight of the carbon powder. The mixing ratio of the copper alloy powder and the carbon powder in the present invention is preferably 10: 1 to 1: 100 (weight ratio), and particularly preferably 1: 1 to 1:80. In this range, the resistance of the resistor made of the resistor paste is particularly excellent in sliding resistance.

As the organic binder used in the present invention,
A binder that is soluble in a known organic solvent and does not react with the copper alloy powder or the carbon powder during storage, drying of the solvent, or curing of the organic binder, and has good dispersibility is used.
The glass transition temperature of the organic binder is −50 to 300 ° C.
It is preferably within the range. Specifically, it is one or more selected from thermoplastic resins, thermosetting resins, and electron beam curable resins. Examples of the thermoplastic resin include acrylic resins, alkyd resins, vinyl chloride resins, urethane resins, Examples thereof include polyester resin, polycarbonate resin, and styrene resin. Among them, polyester resin, urethane resin and acrylic resin are preferable. Examples of thermosetting resins include epoxy resins, phenol resins, melamine resins, alkyd resins, polyurethane resins, polyester resins, acrylic resins, polyimide resins, and combinations of one or more of these modified resins.
Among these, one kind of epoxy resin, phenol resin, and melamine resin, or a combination of two or more kinds is preferable.

The polymer type resistor paste of the present invention has 5 to 100 parts by weight of an organic binder with respect to 100 parts by weight of a mixed powder of copper alloy powder and carbon powder. A sufficient amount of resin can be obtained to bond the conductive powder therein, and sufficient conductivity and mechanical strength can be obtained. When the amount is 100 parts by weight or less, a polymer type resistor paste having a good balance of conductivity and mechanical strength can be obtained. More preferably, it is 10 to 60 parts by weight.

The solvent which can be used in the present invention may be a single solvent or a mixed solvent, but one having a boiling point of 110 ° C. or higher is used.
It is preferable to include one or more kinds. When a solvent having a boiling point of 110 ° C. or higher is contained, the solvent is evaporated during screen printing and the phenomenon that the viscosity of the resistor paste changes does not occur, which is preferable. The amount of the solvent used may be appropriately selected so that the resistor paste has a viscosity suitable for screen printing.

For example, aromatics such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as butyl acetate and ethyl butyrate, ethers such as butyl cellosolve, ethyl cellosolve and ethyl cellosolve acetate, phenol, Phenols such as chlorophenol can be used. In order to improve the dispersibility of the copper alloy powder in the resistor paste of the present invention, an additive may be added to remove or reduce the metal oxide on the surface of the copper alloy powder. Examples of the additive include saturated fatty acids, unsaturated fatty acids, their metal salts, higher aliphatic amines, organic titanate compounds, organic phosphorus compounds, hydroquinone and its derivatives, metal chelate forming agents, phenol compounds, anthracene and its derivatives, One or more selected from the above. The addition amount of the additive is 1 part of the above additive based on 100 parts by weight of the copper alloy powder.
It is preferable to add 0.1 to 25 parts by weight of the seeds or more. If the amount of the additive is 0.1 parts by weight or less, the effects of the additive, such as dispersibility, defoaming, and reduction of oxides, do not sufficiently act. Characteristics as
For example, heat resistance, curability, adhesiveness, etc. are reduced. Preferably, it is 0.1 to 10 parts by weight. It goes without saying that the resistor paste of the present invention may appropriately contain known viscosity modifiers, diluents, anti-settling agents, leveling agents and coupling agents.

In order to improve the dispersibility of the carbon powder and the copper-silver alloy powder in the resistor paste of the present invention, a high-viscosity kneader such as a batch kneader, a spiral mixer, a planetary mixer, a pony mixer, a butterfly mixer, etc. A roll-type kneader such as a vertical axis kneader, a roll mill or a taper roll can be used. In order to fully exert the effects of the present invention, it is preferable that the carbon powder is uniformly dispersed between the copper-silver alloy powders in the resistor paste. Therefore, it is preferable that the carbon powder and the copper-silver alloy powder are made into pastes and preliminarily kneaded, and then the both are mixed in a paste state and sufficiently kneaded. At this time, it is particularly preferable to use a vertical kneader for the preliminary kneading and a roll-type kneader for the main kneading.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. Various tests described in the examples were carried out as follows. (1) Electric resistance value The terminals are printed and cured with a silver paste in advance on the substrate (terminal interval 10 mm). The resistor paste is hand-printed there (screen mesh 250, emulsion thickness 30μ
m) was printed in a line shape with a width of 10 mm so as to straddle the terminals, cured, and the conductivity between the terminals was measured using the 4-terminal method. (2) Migration The resistor paste was printed by a hand-printed screen printing machine (screen mesh 250, emulsion thickness 30 μm) in a linear shape at intervals of 1 mm (width 10 mm, length 30 mm) and cured. 0.2 ml of deionized water was dropped between the two resistors so as to make sufficient contact with both of the two resistors, and a direct current voltage of 10 V was applied between the resistors to reduce the direct current flowing between the resistors. taking measurement. If the current value exceeds 100 μA, it is assumed that silver migration has occurred. (3) Sliding property test A resistor is prepared in the same manner as (1), and the resistor surface is rubbed with a jig. Rubbing strength is 0.5 kg / cm
^{At 2} , the speed is twice per second (one round trip). The number of times
500 times. The surface rubbing jig is a rubber plate with electrodes (on 1 cm square glass epoxy substrate) made by curing silver paste, lined with a stick, and a mainspring attached to measure the rubbing force. And The rubber plate had a thickness of 1 cm ^2, a thickness of 5 mm, and a hardness of 30.
(Shore A) (JIS C 5261b)
Comply with. ). As for slidability, the resistance change after the test is 1%
Those with less than 1 are marked with ⊚, those with 1 to 5% are marked with ◯, and those with 5% or more are marked with x. (4) Sliding property In the test of (3), if something that causes a catch is x,
Those that do not occur are marked with ◎.

[0019]

Example 1 630 g of copper powder [purity 99.9% or higher, manufactured by Kojundo Chemical Co., Ltd.] and 216 g of silver powder [purity 99.9% or higher, manufactured by Mitsuwa Chemical Co., Ltd.] were mixed, and a graphite crucible (nitrided) (With a nozzle made of boron), melted by high frequency induction heating in an argon atmosphere, and heated to 1600 ° C. This melt was jetted from the nozzle for 30 seconds under argon atmospheric pressure. At the same time, fill the cylinder with argon gas (cylinder pressure 1
(50 atm) 4.2NTPm ³ was ejected from the surrounding nozzles toward the ejected melt. At this time, the gas mass velocity / melt mass velocity ratio was 8.46.

The obtained powder was used as a scanning electron microscope [Co., Ltd.
It was spherical (average particle size 20 μm) when observed with Hitachi X-650]. The powder was analyzed using XPS. Measured value Ag / (Ag + Cu) (atomic ratio x)
Are 0.65, 0.55, 0.
45, 0.37, 0.33, the first 2 by definition
The average value of the two was 0.60. When part of the particles was dissolved in concentrated nitric acid and the average silver concentration was measured by ICP, the atomic ratio x was 0.168. The silver concentration on the powder surface was 3.75 times the average silver concentration. From the obtained copper alloy powder, take a part of the powder having a diameter of 10 μm or less,
It was spread with a vibrating ball mill together with 100 ml of mineral spirits. The obtained powder is scaly and has an average diameter of 20.
The thickness was 1 μm.

Powder 5 having a particle size of 15 μm or less among the obtained powders 5
g and carbon powder [Denka Black, Denki Kagaku Kogyo Co., Ltd.
50 g of polyester resin was mixed with 45 g of polyester resin (toluene solution having a solid content of 55%) divided into two equal parts, an appropriate amount of methyl cellosolve was further added, and the mixture was pre-kneaded with a three-roll mill to prepare a silver-copper alloy powder preliminary paste. And a carbon powder preliminary paste was prepared. After that, the silver-copper alloy powder preliminary paste and the carbon powder preliminary paste were mixed, and finally kneaded with a three-roll mill to obtain a resistor paste. The obtained resistor paste,
On a polyester film, apply as in (1) above,
It was dried at 50 ° C. in the air for 1 day. The film thickness of the resistor after drying was 17 μm, and the sheet resistance value was 17.0Ω. When this resistor was left to stand at 60 ° C. and 90% humidity for 1000 hours, the sheet resistance value hardly changed. When applied as in (2) above and subjected to a migration test, the current value after 10 minutes was 0 A, and migration did not occur.

The slidability and slidability tests were conducted as in (3) and (4) above, and the results are shown in Table 1.

[0023]

Example 2 Of the spherical powder obtained in Example 1, 10 μ
10 g of powder of m or less and 10 g of carbon powder [HS-500, manufactured by Asahi Carbon Co., Ltd.], 1 g of hydroquinone, 7 g of epoxy resin [AER661, manufactured by Asahi Chemical Industry Co., Ltd.], 6 g of melamine resin (ethyl of solid content 75%) (Cellosolve solution) and 2 g of butyl carbitol were mixed with the resin composition divided into two equal parts and kneaded with a three-roll to prepare a silver-copper alloy powder preliminary paste and a carbon powder preliminary paste. After that, the silver-copper alloy powder preliminary paste and the carbon powder preliminary paste were mixed and kneaded by a three-roll mill to obtain a resistor paste. The obtained resistor paste is applied onto a glass epoxy substrate as described in (1) above, and 16
It was heat-cured at 0 ° C. for 30 minutes in the air. The film thickness of the resistor after curing was 19 μm, and the sheet resistance value was 9.0Ω. This resistor was left standing at 60 ° C and 90% humidity for 1000 hours, and then the resistance value was measured.
Only a 1.9% change. When applied as in (2) above and subjected to a migration test, the current value after 10 minutes was 1.5 μA, and migration did not occur.

[0024]

[Example 3] 10 µ of the scale-like powder obtained in Example 1
3 g of m or less powder and 5 of the spherical powders obtained in Example 1
Powder 7 μm or less and carbon powder 5 g (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.), 6.5 g of resole type phenol resin [PL2212, manufactured by Gunei Chemical Co., Ltd.], 0.9 g of linolenic acid, ethyl carb 5 g of Thor and a resin composition to which an appropriate amount of methyl cellosolve was further added were divided into two equal parts and kneaded with a three-roll mill to prepare a silver-copper alloy powder preliminary paste and a carbon powder preliminary paste. After that, the silver-copper alloy powder preliminary paste and the carbon powder preliminary paste were mixed and kneaded by a three-roll mill to obtain a resistor paste.

The resulting resistor paste was applied onto a paper phenol substrate as described in (1) above, and heat-cured at 150 ° C. for 30 minutes in the atmosphere. The film thickness of the resistor after curing was 20 μm, and the sheet resistance value was 5Ω. This resistor is 6
The resistance value was measured after leaving it at 0 ° C. and 90% humidity for 1000 hours, and the resistance value changed only by + 2.9%. When applied as in (2) above and subjected to a migration test, the current value after 10 minutes was 2.5 μA and migration did not occur.

[0026]

Comparative Example 1 A resistor paste was obtained in the same manner as in Example 1 except that the scaly copper alloy powder of the present invention was changed to 5 g of commercially available dendritic copper powder [FCC115, manufactured by Fukuda Industry Co., Ltd.]. The obtained resistor paste was applied on a polyester film as in the above (1), and dried in air at 50 ° C. for 1 day.
The film thickness of the resistor after drying was 18 μm, and the sheet resistance value was 50Ω. When this resistor was left standing at 60 ° C. and 90% humidity for 1000 hours, the sheet resistance value was 170.
It changed greatly with Ω. When applied as in (2) above and subjected to a migration test, the current value after 10 minutes was 0 A.
So no migration happened.

[0027]

Comparative Example 2 A resistor paste was obtained in the same manner as in Example 2 except that 10 g of the spherical copper alloy powder was replaced with 10 g of commercially available silver powder (average particle size 3 μm). The obtained resistor paste was applied onto a glass epoxy substrate as described in (1) above, and heat-cured at 160 ° C. for 30 minutes in the atmosphere. The film thickness of the resistor after curing was 18 μm, and the sheet resistance value was 6.0Ω. This resistor was left standing at 60 ° C. and 90% humidity for 1000 hours and then the resistance value was measured, but the resistance value changed only by + 0.8%. (2)
It was applied as above and a migration test was carried out.
After a minute, the current value exceeded 100 μA, and silver migration occurred.

[0028]

Comparative Example 3 5 g of the silver-copper alloy flaky powder in Example 1
And a resistor paste was prepared in exactly the same manner as in Example 1 except that only 30 g of powder having a particle size of 15 μm or less among the flaky powder obtained in Example 1 was used instead of 50 g of carbon powder,
A resistor was produced in exactly the same manner as in Example 1. The film thickness of the resistor after drying was 16 μm, and the sheet resistance value was 10.
It was 0Ω.

The slidability and slidability tests were conducted as in (3) and (4) above, and the results are shown in Table 1.

[0030]

Comparative Example 4 Instead of 5 g of silver-copper alloy powder and 50 g of carbon powder in Example 1, carbon powder [Denka Black,
A resistor was produced in exactly the same manner as in Example 1 except that only 50 g of Denki Kagaku Kogyo Co., Ltd. was used. The dried resistor had a film thickness of 17 μm and a sheet resistance of 50Ω.

Table 1 shows the test results of slidability and slidability.

[0032]

[Table 1]

[0033]

EFFECTS OF THE INVENTION The present invention has a small change in resistance value due to oxidation, does not cause insulation failure due to silver migration,
The present invention provides a polymer type resistor having excellent slidability and slidability and having a low resistance value. INDUSTRIAL APPLICABILITY The resistor paste of the present invention can be used for a variable resistor such as a volume of an audio device, a variable resistor of a control device of an automobile or the like, and a printed resistor of a home electric appliance.

Claims (4)

[Claims] 1. In a polymer type resistor paste having 5 to 100 parts by weight of an organic binder with respect to 100 parts by weight of a conductive powder composed of a copper alloy powder and a carbon powder, the average composition of the copper alloy powder is Ag _x. Cu _1-x (however, 0.
01 ≦ x ≦ 0.4, x represents an atomic ratio), the silver concentration on the surface of the copper alloy powder is higher than the average silver concentration, and
A polymer resistor paste having a region where the silver concentration gradually increases from the inside to the surface. 2. The polymer resistor paste according to claim 1, wherein the silver concentration on the surface of the copper alloy powder is 2.1 times or more the average silver concentration. 3. The weight ratio of the copper alloy powder and the carbon powder is 1.
The polymer type resistor paste according to claim 1 or 2, which is in the range of 0: 1 to 1: 100. 4. The average particle diameter of the copper alloy powder is 0.1 μm.
2. The particle size is ˜100 μm, and the shape is spherical, scaly, or a mixture thereof.
The polymer type resistor paste according to claim 2 or 3.