JPS627641B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive composition having excellent initial conductivity and sufficient conductivity durability under high humidity. Conductive compositions containing silver powder and resin as main components have been put into practical use because they can easily form conductors in jumper circuits, through-hole filling, capacitor electrodes, and the like. However, conductive compositions and conductors using silver powder are mainly used for economic reasons and because silver migration tends to occur, so base metal powders such as copper and nickel are used, or blends of silver powder and copper powder are used. Or silver-plated copper powder, silver-plated copper powder,
Measures have been considered to reduce the silver content as much as possible by using silver-plated glass beads, alloys of silver and copper or nickel, and composite powders mechanically bonded together. However, it is still insufficient to develop a conductive composition that has good initial conductivity and shows little change in conductivity even under high humidity. The present inventor has discovered that a composition containing (a) metallic copper powder, (b) a copper compound, (c) a reducing agent capable of producing metallic copper by reducing copper in the copper compound, and (d) a resin is conductive. It has been found that a cured resin with good properties can be obtained. However, in this case, if an organic or inorganic phosphorous acid compound such as mono- or diester of phosphorous acid is used as a reducing agent, a cured resin with excellent initial conductivity can be obtained; It has been found that when resin is left at high temperature and high humidity for a long period of time, a verdigris-like substance is formed on the surface of the cured resin, and the conductivity gradually decreases over time. On the other hand, a method using a reducing agent having a dihydroxybenzene ring was also discovered (Japanese Patent Application No. 109737/1982), but this method was still not satisfactory for applications requiring even higher long-term reliability. Generally, in electrical applications, high temperatures,
There is a strong desire for a conductive cured resin whose resistance value hardly changes even when left under high humidity. For this reason, the present inventor has developed a composition that provides a conductive cured resin that has good initial conductivity, does not generate a verdigris-like substance even when left under high temperature and high humidity, and has extremely small change in conductivity. As a result of research, we have achieved this goal and completed the present invention. That is, the present invention comprises (a) copper-silver composite powder, (b) copper compound, (c)
Contains a reducing agent having a 1,4 or 1,2-dihydroxybenzene ring (hereinafter simply referred to as dihydroxybenzene ring) and (d) a resin, or further contains these and (e) a chelate-forming substance. This is a characteristic conductive composition. In the case of a composition that does not contain (e) a chelate-forming substance in the present invention, although the mechanism is unknown, the storage stability of the composition is somewhat poor, and as the storage time elapses, it comes into contact with air. There is a tendency for the surface of the composition to harden, impairing its quality, and eventually rendering it unusable (hereinafter abbreviated as scalding phenomenon). If the composition of the present invention is to be put to practical use in applications that require long shelf life, this scalding phenomenon is inconvenient as it must be used immediately after preparation. (e) It has been found that by adding a chelate-forming substance, the parenchymal epithelial burr phenomenon can be prevented without causing any other problems, although the mechanism is also unclear. The copper-silver composite powder used in the present invention is a metal powder whose metal particles are composed of copper and silver, and includes, for example, a metal powder in which the surface of copper particles is plated with silver, an alloy powder of copper and silver, and the like. In this case, the alloy may be an atomically dissolved solid solution made by adding and melting copper and silver metals, a eutectic state that is simply a mixture of copper and silver, or an alloy between copper and silver metals. There is a state in which an intermetallic compound is formed. It also includes metal powders obtained by mixing copper and silver metal powders and mechanically forcibly joining them using a vibration mill, ball mill, stamp mill, etc. Also, other than copper and silver, for example, precious metals such as platinum, mercury, palladium, gold, nickel, zinc, tin, etc.
Lead, iron, aluminum, manganese, tungsten, titanium, silicon, magnesium, chromium, cadmium, cobalt, molybdenum, antimony,
It may also contain metals such as vanadium. The content of copper in the copper-silver composite powder used in the present invention is preferably 50 to 99.8% for performance and economic reasons.
Particularly preferred is 70-99.5%. The shape of the copper-silver composite powder used in the present invention is not particularly limited, and may be, for example, flaky, dendritic, spherical, or irregularly shaped. The particle size is usually preferably 100 microns or less, but depending on the application,
100μ to 1mm can also be used. Of course, copper-silver composite powders having different shapes and particle sizes may be mixed and used. The copper-silver composite powder of the present invention may have an oxide film on its surface or be treated with anti-oxidation treatment, or it may be a commercially available powder that has been treated with stearic acid or the like to prevent agglomeration. Copper composite powder may also be used. The composition of the present invention needs to contain (b), (c) and (d) in addition to (a), or (e) in addition to (a), (b),
It is not necessarily necessary to use four or five separate substances corresponding to (c), (d), and (e); (a), (b), (c), (d) by using a commercially available copper-silver composite powder that has a copper film, or by using a resin with a dihydroxybenzene ring that also serves as (c) and (d). ) and (e), it is also possible to achieve the objective simply by mixing four, three, or two types of substances. Hereinafter, various substances used in the present invention will be explained by giving examples. (1) Copper compounds having only the properties specified in (b) Cuprous chloride, cuprous oxide, cupric oxide, copper acetate, copper salicylate, copper stearate. (2) Substances having only the properties of (c) with a dihydroxybenzene ring: Hydroquinone, catechol, 2-methyl-
Hydroquinone, vinylhydroquinone, tertiarybutylhydroquinone, chlorohydroquinone, phenylhydroquinone, and other substances with the following structures.

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[Formula] A substance that produces a reducing agent having a dihydroxybenzene ring as described above by further heating or adding other substances, such as an adduct of catechol, hydroquinone, etc. and phenyl isocyanate, 2-methyl Substances such as adducts of 2 moles of hydroquinone and 1 mole of tolylene diisocyanate. (3) Resin, that is, a substance that has only the properties as (d) The resin in the present invention is one that has already become a polymer before it is finally cured, or one that becomes a polymer substance through a reaction during curing. It refers to a substance that is a substance that is conductive and that produces an electrically conductive cured product when the composition of the present invention is cured. Specifically, urea formaldehyde resin, melamine formaldehyde resin, phenol formaldehyde resin, unsaturated polyester resin, thermosetting saturated polyester resin, polycarbonate resin, polyphenylene oxide resin, polyphenylene sulfide resin, fatty acid alkyd resin. , polyamide resin, polyimide resin, epoxy acrylate resin, aryl resin (diallyl phthalate resin, etc.), epoxy resin, urethane resin, polyoxymethylene resin, spiroacetal resin, silicone resin, xylene resin, ketone resin, polysulfide rubber, acrylic Resin, styrene resin, olefin resin, vinyl alkanoate resin, butadiene rubber,
Isobutylene rubber, ethylene-propylene rubber, chloroprene rubber, epichlorohydrin rubber, cellulose resin, rosin resin, fluorine resin, phosphonitrile chloride resin,
Ethyl silicate polymer. (4) a copper compound having a dihydroxybenzene ring,
That is, a substance that serves both (b) and (c); a copper salt of the substance in item (2) above; copper salt. (5) Resin-like copper compounds, i.e. substances that serve as both (b) and (d) Copper salts of saturated or unsaturated polyester resins, copper salts of vinyl chloride-vinyl acetate-maleic acid copolymers, sulfoethyl methacrylate-ethyl acrylate copper salts, copper salts of rosin resins. (6) Resin having dihydroxybenzene ring, i.e.
Substances that serve both (c) and (d) Vinyl hydroquinone polymers and copolymer resins, hydroquinone-formaldehyde phenolic resins, hydroquinone-phenol-formaldehyde phenolic resins, catechol-formaldehyde phenolic resins,
1,4-dihydroxynaphthalene-formaldehyde resin. Furthermore, as in the case of (2) above, resins that generate dihydroxybenzene rings by heating or reaction with other substances, such as adducts of vinyl hydroquinone polymer and phenyl isocyanate, and J. Polymer Sci. , part A-1, 7 ,
A mixture of bislactone and diamine of hydroquinone-2,5-bis(ethyl-2'-carboxylic acid) published by N.NAKABAYASHI et al. in 1275-1278 (1969). (7) A resinous copper compound having a dihydroxybenzene ring, that is, a substance that also serves as (b), (c), and (d): a copper salt of a vinylhydroquinone-methacrylic acid copolymer, a copper salt of the resin described in item (6) above. Among the substances that serve as (c) and (c) of the present invention described above, substances that serve as (c) and (d), and substances that serve as (b), (c), and (d) are preferable, and only (c) When using a substance that functions as (b) and (c), the change in conductivity may be a little large when the cured conductive resin is immersed in a solder bath, or the initial conductivity may be slightly inferior. This may result in performance deterioration. (8) Chelate-forming substances, that is, substances exhibiting properties as (e) Chelate-forming substances suitable for the present invention include:
The logarithm value of the stability constant Kma for divalent copper ions at 25° C. and ionic strength of 0.1 is 3 or more, preferably 5 or more. These substances include the following: 8-1 Aliphatic amines and their derivatives Ethylenediamine, N-(2-hydroxyethyl)ethylenediamine, trimethylenediamine, 1,2-diaminocyclohexane,
Triethylenetetramine, 2-aminomethylpyridine. 8-2 Aromatic polyamine Purine, adenine, 2-aminomethylpyridine, histamine. 8-3 β-diketone acetylacetone, trifluoroacetylacetone, 4,4,4-trifluoro-1-
Phenyl-1,3-butanedione, hexafluoroacetylacetone, benzoylacetone, dibenzoylmethane, 5,5-dimethyl-1,3-cyclohexanedione. 8-4 Phenolic acid compound oxine, 2-methyloxine, oxine-5-sulfonic acid, dimethylglyoxime,
1-Nitroso-2-naphthol, 2-nitroso-1-naphthol, salicylaldehyde. 8-5 Others 2,2'-dipyridine, 1,10-phenanthroline. Of course, it is also possible to use substances that have the property (e) and other properties such as (b), (c), and (d). The proportion of the copper compound used in the present invention is such that the copper content of the copper compound relative to the copper-silver composite powder is 0.1 to 30% by weight, preferably 0.2 to 10% by weight. The proportion of the reducing agent having a dihydroxybenzene ring used in the present invention is preferably 80 equivalent % or more, particularly preferably 95 equivalent % or more, based on the amount sufficient to reduce all the copper in the copper compound. The proportion of the resin used in the present invention is 5 to 60% by weight, preferably 8 to 45% by weight based on the total nonvolatile content of the composition used in the present invention. The resin used in the present invention may be solid per se, but it may be one that becomes substantially or apparently liquid upon curing by itself or in the presence of an organic solvent, water, plasticizer, etc. . Usage forms of resin include solvent type dissolved in organic solvent, water soluble type, water emulsion type, solvent emulsion type,
It may be either a 100% liquid resin type or a 100% solid resin type that becomes liquid at the temperature during curing, and is not particularly limited. The following methods may be used to cure each of these resins. That is, if these are cured while evaporating volatile substances by drying, such as room temperature drying type resins (Latzker type), or if they have (a) thermosetting properties, depending on the type, ( 1) cured by heat or (2) for resins cured by vinyl polymerization, such as unsaturated polyester resins and acrylate resins, azobisisobutyronitrile, di-t-
In the case of epoxy resins, triethylenetetramine, polyamide polyamine, diaminodicyclohexylmethane, diaminodiphenylmethane, adipic acid dihydrazide, imidazole derivatives, dicyandiamide, etc. , boron trifluoride/ethylamine complex,
Using known curing agents such as polymercapto compounds, polyhydric carboxylic acids and their anhydrides, and in the case of phenolic resins, hexamethylenetetramine,
By using a curing agent or curing accelerator such as paraformaldehyde, P-toluenesulfonic acid, etc., or by using a known dryer such as naphthenate, cobalt octylate, etc. in the case of oxidative curing type resin. (b) In the case of thermoplastic,
What is necessary is just to harden by a well-known means, respectively, by cooling after heating. In short, the resin may be cured by any known means depending on the type and nature of the resin. Note that the reducing action in the present invention is preferably exerted at the stage of curing the resin, and if this reduction reaction is too rapid or slow compared to the curing, the purpose obtained by the method of the present invention may be impaired. Since it affects the durability of the conductivity of the material, the reduction temperature is usually not high enough due to the curing conditions and workability in practical use.
The temperature is 250°C or less, preferably room temperature to 200°C, particularly preferably 50°C to 180°C. Therefore, in order to satisfy such conditions, a reducing agent having a dihydroxybenzene ring, a copper-silver composite powder, a copper compound, a resin,
What is necessary is to select a chelate-forming substance or the like. Further, the atmosphere for curing the composition of the present invention may be any atmosphere such as nitrogen, an inert gas such as carbon dioxide gas, or air, and there is no particular restriction on the atmosphere. When curing the resin in the method of the present invention,
Various known additives such as those listed below may be added in advance. For example, molecular weight regulators such as mercaptopropionic acid, carbon tetrabromide, stabilizers such as p-benzoquinone, phenothiazine, reactive diluents such as butyl glycidyl ether, phenyl glycidyl ether, dibutyl phthalate, tricresyl phosphate, etc. Noble metals belonging to group B and groups of the periodic table such as gold, silver, and palladium, and their compounds; inorganic bases such as lithium hydroxide and potassium hydroxide; dimethylbenzylamine, ethanolamine, and tris(N.N. - amino compounds such as (dimethylaminomethyl)phenol, N/N-dimethylaniline, acids such as acetic acid, oxalic acid, benzoic acid, PH regulators such as sodium orthophosphate, borax, potassium acetate, polyvinyl alcohol, polyvinylpyrrolidone. Viscosity modifiers such as potassium oleate,
Surfactants such as sodium dodecylbenzenesulfonate, polyoxyethylene lauryl ether, octadecylpyridinium chloride, solvents such as water, toluene, methyl ethyl ketone, ethylene glycol monoethyl ether, paraffin wax, carbon black, methyl ethyl ketoxime, lubricants, These include flame retardants, colorants, blowing agents, and thixotropic agents. When curing the composition of the present invention, various substrates such as polysulfone resin sheets, phenolic resin laminates, epoxy resin laminates, polyimide films, organic materials such as non-woven fabrics, glass, inorganic materials such as alumina, painted iron plates, coatings, etc. It may be applied or printed on an aluminum plate or the like and cured, or it may be formed by placing it in a mold. The conductive cured product obtained by curing the composition of the present invention may be subjected to various known protective treatments as described below, taking into consideration the intended use, environment of use, enhancement of reliability, etc. That is, such treatments include electrical or chemical plating with nickel, copper, etc., coating with epoxy resin, phenolic resin, rosin-based substances, polyethylene film, etc., surface treatment with imidazole-based processing agents, silicone-based processing agents, etc. There is. The composition of the present invention can be used in paints, adhesives, printing inks, molded products, etc., and is used in conductive circuits, crossover circuits, high frequency protection circuits, heat dissipation circuits, through-hole parts, etc. in the electrical and electronic industrial fields. It has a wide range of practical applications, such as filling, adhesion of parts, etc. in the automobile industry, dew condensation prevention circuits on windows, and heaters in the housing field, and is extremely useful industrially. Examples will be described below. Parts and % hereinafter mean parts by weight and % by weight, respectively, and concentrations described in the examples represent the proportion of the component in all components in % by weight. The "printed material by screen printing method" in the examples described below was formed by the following method. An S-shaped linear printed material having a total length of 200 mm and a width of 0.5 mm with a line interval of 0.5 mm was formed on the surface of the printing material by the following method. In other words, a film was made directly on a 180-mesh Tetron screen using a photographic engraving method so that the film thickness of the entire screen was 145 μm, and the structure was such that the screen was closed except for the necessary image lines. Create a screen for screen printing and apply the conductive composition used in each experiment to the rubber hardness.
A squeegee using No. 70 urethane rubber was used to print on the surface of the printing material, and then the material was cured under the curing conditions of each experiment to form a printed material. In addition, the resistance value and specific resistance value listed as a guide for conductivity are measured using a tester (manufactured by Yokogawa Electric Corporation, Type
−3201) Wheatstone Bridge (manufactured by Yokogawa Electric Corporation,
Type-2755) was used to measure the resistance value by contacting both ends of the cured product of the printed material, and the thickness of the cured product,
The length and width were measured and the specific resistance value was calculated. The durability tests in the examples described below were carried out using a constant temperature and humidity tester (ETAC's tabletop temperature and humidity tester JLH-
An accelerated test was conducted using a 400-40 type under the conditions of 50℃, RH95%, and 1000 hours.The printed material was taken out at each time, and after being left at room temperature for 1 hour, changes in resistance and appearance were measured. did. Example 1 Each of the liquid compositions obtained in Experiment Nos. 1 to 7 below was printed by the above-mentioned "screen printing method" on the surface of each of six glass plates (thickness 1.7 mm) whose one surface had been cleaned with ethyl acetate. Each printed body obtained in this way was pre-dried at 100°C for 20 minutes in a thermostat in an air atmosphere, and then dried at 165°C. The cured coating film obtained by heating and curing for 90 minutes was left to cool at room temperature, and the resistance and specific resistance values of each were measured, and the test specimens were subsequently subjected to a durability test. Further, 100 g of each of the liquid compositions obtained in Experiment Nos. 1 to 7 below was placed in a 100 ml polyethylene container, the container was tightly stoppered, and the container was left at room temperature to observe the skinning phenomenon on the surface. The results are shown in Table 1. Experiment No. 1 (Comparative Example) (a) 110 parts of industrial copper powder (amorphous, average particle size 15μ, containing about 2% copper oxide), (b) hydroquinone modification with 80% resin dissolved in ethylene glycol monobutyl ether 42 parts of resol type phenolic resin (obtained by reacting formalin containing 2 moles of hydroquinone, 0.5 moles of phenol, and 6 moles of formaldehyde in the presence of an ammonia catalyst), A liquid composition prepared by mixing 0.2 parts of methyl)phenol and 10 parts of ethyl (d)acetoacetate. Experiment No. 2 (Example of the present invention) Other than using 110 parts of copper-silver alloy (copper content 60%, flaky shape, average particle size 13μ) and 0.5 part cupric oxide as (a) in Experiment No. 1 above. is a liquid composition having the same composition as Experiment No. 1. Experiment number 3 (example of the present invention) In the above experiment number 2, as (d) 4.4.4-
A liquid composition having the same composition except that 10 parts of trifluoro-1-phenyl-1,3-butanedione is used. Experiment No. 4 (Example of the present invention) In Experiment No. 1, copper-silver composite powder (85
Powder made by mechanically joining % electrolytic copper powder and 15% silver powder using a vibrating mill, average particle size 15 μ, copper oxide 0.58%, flake form) The composition is the same except that 110 parts are used. Liquid composition. Experiment No. 5 (Example of the Present Invention) A liquid composition having the same composition as Experiment No. 4 except that 5 parts of 2,2'-dipyridyl and (v) 5 parts of diethylene glycol monomethyl ether were used as (d). Experiment No. 6 (Example of the present invention) In Experiment No. 2, modified resol type phenolic resin with a resin content of 80% (1.2 mol of methylhydroquinone, 0.3 mol of catechol, 0.5 mol of tert-butylphenol) dissolved in diethylene glycol monoethyl ether as (b) (obtained by reacting an aqueous formalin solution containing 4 moles of formaldehyde in the presence of an ammonia catalyst). Experiment No. 7 (Example of the Present Invention) A liquid composition having the same composition as (b) in Experiment No. 3 except that 45 parts of the modified resol type phenolic resin used in Experiment No. 6 was used. Example 2 Each liquid composition obtained in Experiment Nos. 6 and 7 in Example 1 and Experiment No. 8 below was screen printed on the surface of a glass-epoxy resin laminate having a thickness of 1.7 mm in the same manner as in Example 1. Then, the mixture was cured by heating to obtain a conductive cured coating film. Next, after measuring the resistance value of the cured coating film, it was immersed in a 260°C solder bath for a certain period of time, and after cooling to room temperature, the resistance value was measured to evaluate the solder heat resistance. The results obtained are summarized in Table 2. Experiment number 8 (a) Copper-silver alloy 110 used in experiment number 2
(b) A formalin aqueous solution containing a resol type phenolic resin (1.5 mol of phenol, 0.5 mol of tert-butylphenol, and 4 mol of formaldehyde) with a solid content of 80% dissolved in diethylene glycol monoethyl ether is reacted in the presence of an ammonia catalyst. ), (c) 7 parts of catechol, (d) 18 parts of methylhydroquinone, (v) 6 parts of diethylene glycol monomethyl ether, (h) tris(N・N'-dimethylaminomethyl)phenol 0.2
10 parts of ethyl (tri)acetoacetate.

【table】

[Table] Comparative Example 2 Alcohol-soluble room temperature curing resol type phenolic resin with methanol content of 10% and cured resin content of 72% liquid
70 parts, industrial copper powder (flake form, 325 mesh)
Add phosphorus to a well-stirred mixture of 50 parts of metallic copper powder from which oxides on the surface of 4 parts of acid were added and mixed to obtain a conductive composition. After printing and curing using the conductive composition according to the methods of Examples 1 and 2 of the present invention, a durability test and an evaluation of solder heat resistance were conducted. 50℃, 95%
RH, initial resistance value 400Ω in 1000 hours moisture resistance test
(specific resistance value 5×10 ^-3 Ω・cm) is 50KΩ (approximately 100 times)
rose to Furthermore, after the moisture resistance test, the cured product had a patina that appeared to be greenish blue on the entire surface. Meanwhile 260℃
When immersed in a solder bath for 20 seconds, the initial resistance value is 400.
Ω increased to 4KΩ (10 times).

Claims (1)

[Claims] 1 (a) copper-silver composite powder, (b) copper compound, (c) reducing agent having a 1,4- or 1,2-didroxybenzene ring,
(d) A conductive composition characterized by containing a resin. 2 Contains (a) copper-silver composite powder, (b) copper compound, (c) reducing agent having 1,4 or 1,2-dihydroxybenzene ring, (d) resin, and (e) chelate-forming substance. Characteristic conductive compositions.