JPS62160603A - Conducting paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a conductive paste, and more particularly to a conductive wave paste containing copper powder.

In recent years, with the development of electronic devices, the conventional method of forming conductor circuits by etching copper foil, etc., has changed to the formation of conductor circuits by screen printing using conductive paste, and the use of solder to connect conductors. Attachment has shifted to adhesion using conductive paste.

Further, electromagnetic waves generated in electronic devices such as converters have become a problem as electromagnetic interference, but this problem has been solved by applying a conductive paste to the electromagnetic shielding material.

[Conventional technology]

Conductive wave strike is made of conductive filler, mainly metal powder,
It is a composite material consisting of a binder made of synthetic resin, a solvent and additives as necessary, and the performance of yeast is determined by the characteristics and combination of these materials. Among them, it is natural that conductive fillers are the ones that affect the conductivity itself, and there are various types such as silver, copper, nickel, and carbon powder, but for those that require high conductivity, it is necessary to use conductive fillers. Metal fillers are the main filler, and carbon is either not used or only used as a supplement.

However, silver, copper, and nickel powder as metal fillers each have advantages and disadvantages, and in terms of original conductivity, silver,
Copper powder is superior, but silver powder is a precious metal and is the most expensive. Copper powder is the most advantageous in terms of cost, but it forms a surface oxide film at a high rate, making it difficult to connect the original conductivity. Nickel powder has lower inherent conductivity than copper powder.

Although the price is generally higher than that of copper powder, it is cheaper than silver powder, and the rate of formation of a surface oxide film is slower than that of copper powder, making it easier to maintain conductivity.

As shown above, copper powder is very advantageous as a conductive paste material both in terms of its inherent conductivity and in terms of price, but it forms a non-conductive oxide film very quickly and cannot be used in the air. Not only is it difficult to handle, but even if conductive yeast is temporarily prepared using reduced copper powder, oxidation will begin again and it will not have drowsy conductivity. Various proposals have been made to solve this problem. One method is to mix or alloy copper powder with metal powder that is difficult to oxidize, such as silver powder, or to plate the surface of copper powder. Although this method is effective, it is expensive to use silver with this method alone, and it is becoming impossible to use silver in terms of cost for electronic equipment.

In addition, as additives such as reducing agents, benzotriazole, titanium-based coupling agents, fixed particle size nocarbon powder, etc. have been proposed, but they are still insufficient, and in particular, the particle size of copper powder becomes fine. As the surface area increases, the effect becomes very small.

[Problem that the invention seeks to solve]

The present invention has been made in order to solve the above-mentioned drawbacks by using copper powder which is advantageous in terms of cost, and to obtain a conductive yeast capable of permanently forming a stable conductive film even in the air.

[Failure to solve the problem]

The present invention provides a conductive paste comprising (A) 70 to 90 parts by weight of copper powder and (B) 30 to 10 parts by weight of at least one resin selected from phenolic resins, epoxy resins, and acrylic resins. 0.1 to 8 parts by weight of the C1 copper chelating agent per 100 parts by weight of the active ingredient consisting of 0.1 to 8 parts by weight, preferably 0.
5 to 5 parts by weight and (D) glycerin 1 to 30 parts by weight, preferably 5 to 2 parts by weight.
It is characterized by using a solvent containing 0 parts by weight as a part thereof.

[For production]

In order to put copper powder-containing conductive waves into practical use, the electrical resistance value of the coating film must be 1 × 10-”Q'Cm~1X1
Approximately 0-4 Ω is required, but even if copper powder and resin such as phenol resin, epoxy resin, acrylic resin, etc. are mixed in a solvent and made into a waveform, the electrical resistance value of the coating film is 1 × 1.
It is 0 Ω・1 or more.

In other words, the surface of normally provided copper powder has already been oxidized and each grain is covered with a non-conductive oxide film, so by forming a film on the copper powder, the metal particles are brought into contact with each other. However, its electrical resistance will be extremely large. In addition, even if a similar paste is made into a film using reduced copper powder with very little oxide film due to careful handling, if heat is applied during film formation or time is taken to evaporate the solvent at low temperature, the oxide film will form during that time. This causes the formation of stains and increases the stain resistance value. Moreover, this tendency is toward thicker fine copper powders with larger surface areas.

However, the copper powder-containing conductive paste obtained by adding the copper chelating agent and glycerin of the present invention surprisingly shows a coating film with an IX 10- The electrical resistance value is reduced to a value of 1.about.I x 10-' Ω/step, making it useful enough for practical use.

The reason is not clear, but the copper chelating agent reacts with the surface oxide film of the copper powder during coating film formation by heating, etc., and it is dissolved in a solvent containing glycerin, and the newly formed conductive It is presumed that this is because the surface of the copper is then covered with resin, which isolates it from the atmosphere and significantly slows down its oxidation rate.

As the copper powder used in the present invention, a commercially available product produced by an ordinary electrolytic method is sufficient, and the shape of the powder may be dendritic, scaly, or spherical.

Further, the particle size is preferably 0.1 to 200 microns, but it can be used depending on the purpose and is not limited.

The resin used in the present invention is at least one resin selected from phenol resins, epoxy resins, and acrylic resins, each of which is commercially available and available.

Examples of the phenolic resin include reactants of heptenols such as phenol, cresol, and xylenol, and toformaldehyde.

Examples of epoxy resins include bisphenol A type I-oxy resin made of bisphenol A and epichlorohydrin, noblak type epoxy resin made of phenol novilac and epichlorohydrin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, etc. Examples include, but are not limited to, alicyclic epoxy resins.

Examples of acrylic resins include acrylic resins polymerized as monomers such as methyl, ethyl, butyl esters of acrylic acid or methacrylic acid.

The copper chelating agent used in the present invention is a compound that forms a chelate compound with copper, and specifically, sodium ethylenediaminetetraacetic acid, nitrilotriacetic acid, noethylenetriaminepentaacetic acid, cyclohexanethoaminetetraacetic acid, Examples include alkali metal salts such as potassium, and alkaline earth metal salts such as calcium and barium.

The blending amount is 0.1 parts by weight per 100 parts by weight of the active ingredient consisting of 70 to 90 parts by weight of copper powder and 30 to 10 parts by weight of resin.
It is desirable to use 0.5 to 5 parts by weight, preferably 0.5 to 5 parts by weight. If the amount of the copper chelating agent is as small as 0.1 part by weight, the electrical resistance value of the coating film will not become small.

Further, if the amount is greater than 8 parts by weight, it is not preferable because not only is there no advantage in terms of cost, but the coating film becomes brittle and other properties other than conductivity are deteriorated.

Using glycerin as part or all of the solvent
The above-mentioned copper chelating agent can be partially or completely dissolved in the paste, and the effect can be significantly improved. The amount to be blended is preferably 1 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the active ingredient. If the amount is less than 1 part by weight, the effect will not be expressed, and if the amount is more than 30 parts by weight, other properties of the coating film other than conductivity will be deteriorated. That is, the coating film is too soft, takes too long to dry or harden, and has poor solvent resistance.

In the present invention, it is natural to add a solvent other than glycerin if necessary, and this can be done depending on the workability of the plating process. It is better that this solvent be a good solvent for glycerin, but the effect can be expected even if it is a poor solvent.

Examples of good solvents include alcohols such as methanol and ethanol, esters such as ethyl acetate and methyl acetate,
Cellosolves such as ethylseronlube and butylseronlube, and glycols such as ethylene glycol and propylene glycol are used.

Examples of poor solvents include aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as pentane and hexane, halogenated hydrocarbons such as chloroform, carbon tetrachloride and trichloroethane, and ketones such as acetone and methyl ethyl ketone.

〔Example〕

The present invention will be explained in detail below with reference to Examples.

However, the parts in the text mean parts by weight.

Example 1 80 parts of dendritic electrolytic copper powder (average particle size 20μ, manufactured by Nippon Mining Co., Ltd. +6), phenol resin (B manufactured by Showa Kobunshi Co., Ltd.)
RM-2120) 20 parts, butyl cellosolve' 20 parts,
After thoroughly mixing 10 parts of glycerin and 2 parts of trisodium ethylenediaminetetraacetate using a three-roll mill, the mixture was screen printed at 200 ml and then heated in an oven at 150°C.
, hardened for 30 minutes, width 1f1m, length 5α, thickness 50
A micron film was obtained.

The electrical resistance value (volume specific resistance) of the coating film is 2X10-5Ω・
The electrical resistance value after being exposed in air at 80° C. for 500 hours in a box was 5×10−30·q.

Examples 2 to 6, Comparative Examples 1 to 5 Coating films were prepared in the same manner as in Example 1, except that the amount of glycerin and the amount of copper chelating agent were changed, and the electrical resistance values were measured.

The results are shown in Table 1.

Examples 7 to 12 Coating films were prepared in the same manner as in Example 1, except that the type of copper chelating agent was changed, and the electrical resistance values were measured.

The results are shown in Table 1.

Example 13 A coating film was prepared in the same manner as in Example 1, except that the phenol resin was changed to an epoxy resin (manufactured by Yuka Shell Co., Ltd., Epicoat 828) and the curing agent was changed to 2 parts of DMP-300, and the electrical resistance value was determined. was measured.

The results are shown in Table 1.

Example 14 A coating film was created in the same manner as in Example 1, except that the phenol resin was replaced with an acrylic resin (Dyanal BR-73 manufactured by Mitsubishi Rayon Co., Ltd.) and the butyl cellosolve was replaced with methyl ethyl ketone, and the electrical resistance was measured. did.

The results are shown in Table 1.

(The following is a blank space) [Effects of the invention] As shown in the examples and comparative examples above, if a copper chelating agent or glycerin is not blended, the electrical resistance value is extremely high at 1 × 100・α or more. However, when this copper chelating agent and glycerin are blended, the electrical resistance value of the coating film decreases to I x 10'-'' to 1 x 10-4, making it useful enough for practical use as a conductive paste.

Claims (2)

[Claims] (1) 100 parts by weight of an active ingredient consisting of (A) 70 to 90 parts by weight of copper powder and (B) 30 to 10 parts by weight of at least one resin selected from phenolic resin, epoxy resin, and acrylic resin. A conductive paste comprising a solvent containing (C) 0.1 to 8 parts by weight of a copper chelating agent and (D) 1 to 30 parts by weight of glycerin. (2) The conductive paste according to item 1, wherein the copper chelating agent is an alkali metal salt or an alkaline earth metal salt of ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, or cyclohexanediaminetetraacetic acid.