JPS5852502B2 - double conductive coating - Google Patents

Description

[Detailed description of the invention] The present invention relates to dual conductive coatings.

More specifically, the present invention relates to a double conductive coating having excellent conductivity and durability.

Conventionally, a composition made of silver powder and a resin has been used as a so-called conductive paste.

When this composition is applied onto a substrate and dried, the silver powders in the solid resin come into contact with each other to form a conductive film.

Such a conductive paste made of silver thread is expensive due to the use of expensive silver powder, so it is difficult to apply it to general purposes.

The present inventor conducted extensive research in order to obtain a conductive film using copper powder, which can be supplied in abundance at a much lower price than silver powder.

However, when copper powder is used, even if the initial conductivity is good, its retention is not sufficient, and in particular, the phenomenon that the conductivity gradually decreases in high humidity air may occur depending on the treatment. It turned out to be terrible.

As a result of further research to solve this problem, we succeeded in obtaining excellent conductivity and excellent conductivity retention using copper powder, and achieved the present invention.

The present invention involves coating or printing a copper-containing composition consisting of copper powder, copper in the form of a compound, and a resin containing a reducing agent on a base material, and then reacting the composition to reduce the copper in the compound form by the action of the reducing agent. The present invention relates to a double current-conducting film in which copper powder is connected in a resin using the metallic copper produced by the process, and the conductive film thus obtained is melted and coated with solder.

The copper powder used in the present invention may have various shapes such as dendritic, granular, and flake, either alone or in combination as appropriate.

Its composition may be pure copper or a copper alloy such as brass or bronze.

Contains no copper in compound form. The compound copper used in the present invention refers to copper in a compound form, not as a pure metal.

Typical examples include organic acids, inorganic acids, and copper salts of resins with acid groups.

For example, (1) copper octylate, copper acetate, diethyl phosphite copper salt, copper chloride (2) methacrylic acid, acrylic acid, maleic acid,
Copper salts of acrylic resins and vinyl acetate resins containing fumaric acid monoester, itaconic acid monoester, crotonic acid, and styrene phosphonic acid as one component (3) Copper salts of polyester resins and polyamide resins having carboxyl groups (4) Epoxy resins Copper salts of resins obtained by reacting polymers with epoxy groups with phosphorous acid, hypophosphorous acid, etc. (5) Copper salts of phenolic resins.

In addition, the copper oxide surrounding the copper powder can also be used as compound copper.

In this case, the shape of the copper oxide does not matter, so it may be in powder form.

In the resin containing a reducing agent used in the present invention, the reducing agent and the resin may coexist in the form of a mixture, or the resin itself may have a group exhibiting a reducing action.

Examples of the former include phosphorous acid, phosphite ester, hypophosphorous acid, hypophosphite ester, dialkylphosphine oxyto, diarylphosphonite, arylphosphonite, formaldehyde, hydrazine, etc. Other known reducing agents such as hydroquinone, catechol, toluenesulfinic acid, etc. are representative.

In the latter case, the group exhibiting a reducing action includes a phosphite group, a hypophosphite group, a hydrazine group, and other known reducing groups such as a hydroquinone group, a catechol group, and a sulfinic acid group. It is true.

In addition, such resins themselves include (1) a resin obtained by reacting an epoxy resin with phosphorous acid or hypophosphorous acid, (2) an acrylic polymer containing glycidyl methacrylate as one component, and glycidyl allyl ether. Resin obtained by reacting a polymer such as vinyl acetate or vinyl chloride containing as one component with phosphorous acid or hypophosphorous acid (3) Reacting hydrazine with an acrylic polymer containing glycidyl methacrylate as one component A typical example is a resin containing a hydrazine group.

Examples of the resin used in the present invention include melamine-formaldehyde resin, phenol-formaldehyde resin (
Publicly known documents, such as R,W.

Written by Martin, John Wiley & 5o
ns, Inc.

Published in 1956 1 The Cherrixistry o
f PhenolicResins, pages 27-31
Resins using formaldehyde such as phenol-formaldehyde resins as described on pages 88 to 107), polyester resins, polyamide resins,
Polyurethane resin, epoxy resin, diallyl phthalate resin, polyimide resin, acrylic resin, vinyl acetate resin, petroleum resin, silicone resin, cellulose resin, fluororesin, butadiene rubber, epichlorohydrin rubber,
Resins mainly composed of organic substances such as chloropyrene rubber, etc.
Representative examples include resins mainly composed of inorganic substances such as ammonium silicate and ethyl silicate.

Types of resin include aqueous solution type, organic solvent solution type, aqueous emulsion type, solvent emulsion type, 100% polymerizable liquid type, solid type, etc., and may be either thermosetting or thermoplastic.

In the present invention, the copper-containing composition consisting of copper powder, copper in the form of a compound, and a resin containing a reducing agent may include methanol, isopropyl alcohol, methyl ethyl ketone, cyclohexanone, acetophenone, butyl acetate, xylene, as long as it does not impede the purpose of the present invention. , hexane, mineral spirits,
Organic liquids such as ethylene glycol monoethyl ether, ethoxyethanol acetate, dimethylformamide, volatile substances such as water, ethylenediaminetetraacetic acid,
Chelating substances such as ethylenediamine, acetylacetone, ethyl acetoacetate, diethyl malonate, phytic acid, orthophenanthroline, etc., acids such as acetic acid, benzoic acid, salicylic acid, etc., substances for adjusting the curing rate such as bases such as amines, gold, Of course, other additives such as noble metals such as silver, noble metal compounds such as platinum chloride and rhodium acetate, curing agents, polymerization initiators, polymerization inhibitors, plasticizers, fillers, etc. can also be blended.

In the present invention, the amount of copper powder relative to the non-volatile content in the copper-containing composition consisting of copper powder, copper in the form of a compound, and a resin containing a reducing agent is usually 50-85% by weight, depending on the formulation, 50-95% by weight. Regarding copper in compound form, the weight of the copper element is usually 0.1 to 10%, and the non-volatile substance of resin containing a reducing agent is usually 49 to 10% by weight.
4 weight ratio, depending on the formulation, 49 to 5 weight ratio.The amount of reducing agent is sufficient to connect the copper powder and develop conductivity by reducing the compound copper, and there are no special restrictions. There isn't.

The base material on which the above-described copper-containing composition is coated or printed includes base materials made of resins such as phenol resin, epoxy resin, polyimide resin, polyester resin, polyethylene, etc., and these resins and glass fibers and paper. , various non-conductive organic substrates such as substrates combined with non-woven fabrics, cloth, etc., various organic materials such as polyethylene, acrylic resin, etc. on plates, films, etc. of metals such as aluminum, iron, stainless steel, copper, etc. Typical examples include base materials coated with non-conductive substances such as epoxy resins, and various non-conductive non-metallic inorganic base materials such as silica, alumina, aluminosilicate, etc.

The difference in shape does not matter.

There are no particular restrictions on the method of coating or printing the copper-containing composition on these substrates, and there are various methods such as roll coater, tipping, and screen printing.

After coating or printing the copper-containing composition on the substrate, the conditions for reacting it include a temperature of room temperature to 250°C, usually below 200°C, and an atmosphere of air or an inert gas such as nitrogen. During this reaction, curing or reaction of the resin containing the reducing agent also proceeds.

Through this reaction, the copper powder is bonded by copper precipitated by reduction from copper in the form of a compound.
Even if the film has the following values and is left in an air atmosphere with a relative humidity of 20φ or less and a temperature of 150°C for 200 hours, it will still be 10-
This can be practically confirmed by not exceeding 29 cm.

In the present invention, the conductive film obtained as described above may be melted and coated with solder by, for example, being brought into contact with a molten solder bath.

Typical methods include melting solder on this film, or applying solder cream and melting it by heating.

In this case, the typical solder is an alloy consisting of tin and lead, but there are also solders containing a small amount of other metals such as silver and copper, and solders containing only tin.

In addition, when coating the solder, it is also possible to improve the solder coverage by treating the conductive film to be coated with the solder with solder flux immediately before or for a long period of time.

The double conductive film of the present invention is particularly useful for various conductive circuits such as electronic circuits, since it has extremely excellent conductivity and conductivity retention.

A further surprising fact in the present invention is that the solder is well wetted and coated on the conductive film connected to the copper powder, and its adhesion is good.

Normally, if a composition consisting of copper powder and resin is simply coated or printed on a base material in a similar manner and then dried, attempts are made to coat it with solder, but the solder is repelled and a continuous layer remains on the coating. It is difficult to form a coating, and in this case, no significant improvement is observed even with the use of solder flux, which is commonly used to prevent solder from repelling to copper plates and copper wires.

In the case of the present invention, the reason why the solder is well coated is not clear, but it is presumed that the properties of the copper powder connected by copper probably exceed the properties of the resin to repel the solder.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

All terms and parts in the examples are based on weight.

Example 1 (a) Preparation of a copper-containing composition and its cured film 100 parts of pass flake copper powder (contains 10% copper wire in the form of copper oxide on the surface of the copper powder as compound copper), resol type phenol resin (resin content about 70 parts, methanol about 3 parts)
120 parts of a reducing agent having a ring phosphate ester group [3,160 parts of ethylene glycol di(2-hydroxypropyl acid phosphite) ether, 100 parts of acetophenone, 150 parts of cyclohexanone, 25 parts of dipyridyl, dimethylaminoethanol] A copper-containing composition was prepared by stirring 10 parts in a bath at room temperature for 30 minutes.

Using the obtained copper-containing composition, a screen printing machine (1
Approximately 1w11 width on paper/phenol resin laminate (thickness 271m) using 80 mesh, Tetron screen)
10 sheets were printed with a total length of 18 crrL.

Next, this was placed in a heating dryer with an air atmosphere at a temperature of 150° C. to carry out a heating reaction for 30 minutes, and then taken out and left to cool to room temperature.

(This is referred to as cured product A.) The thickness of the conductive coating of cured product A was about 50 μm.

(0) Preparation of double conductive film After applying solder flux to the entire conductive film on the five cured products A, apply 28% of solder (Sn60%) on the conductive film.
It was melted at 0° C. and the solder was allowed to adhere (for 2 to 3 seconds).

The solder spread and adhered to the entire surface of the conductive film on cured product A without repelling (this is referred to as cured product B).

The thickness of the solder film was about 50 μm to 80 μm.

(c) Conductivity and conductivity retention test Cured product A and cured product B were placed in a constant humidity chamber at a temperature of 40°C and a relative humidity of 90°C, left for a specified period of time, then taken out, and left for one day and night (
Table 1 shows the resistance of the circuit measured using a Wheatstone bridge resistance measuring device.

Example 2 (a) Preparation of copper-containing composition and its cured film 325 mesh pass industrial copper powder (average particle size 15μ, copper oxide content approximately 0)
．． 5), 1050 parts of hydroquinone, 2 methylated methylolmelamine resin (trade name Cymel 350)
5 parts, 65 parts of ethylene glycol monobutyl ether,
A copper-containing composition consisting of 1.5 parts of N,N'-dimethylaminomethylphenol was prepared.

Using the obtained copper-containing composition, a screen printing machine (2
Using a 00 mesh tetroon free reel), the total length is 1 mm with a width of about IM on a glass epoxy board (thickness of about 2M).
Ten sheets were printed with a length of 8 cIrL.

Next, this was dried with 300 molecules at a concentration of 80°C in an air atmosphere, and then heated and cured for 40 minutes in a heating dryer at a temperature of 160°C in an air atmosphere, and then taken out and cooled to room temperature. Let it be object C.

) The thickness of the conductive film of cured product C was about 50 μm.

(b) Preparation of double conductive film Solder flux (Solder flux S-100, manufactured by Tamura Kaken Co., Ltd.) was applied to five sheets of the cured product C prepared in (a) so as to wet the entire conductive film. After that, the substrate surface temperature is 80°C and the two molecules are dried, and then molten solder (S
Solder adhesion resistance (250-260℃,
2-3 seconds).

The solder spread and adhered to the entire surface of the conductive film on the cured product C without repelling it (this is referred to as the cured product C).

). The thickness of the solder film was about 50 μm to 80 μm.

(c) Conductivity and conductivity retention test Cured product C and cured product were placed in a constant humidity chamber at a temperature of 40℃ and a relative humidity of 95 degrees, left for a specified period of time, taken out, and left for one day and night (at room temperature). , the resistance of the circuit was measured using a Wheatstone bridge resistance measuring device Example 3 (a) Preparation of a copper-containing composition and its cured film 325 mesh pass industrial copper powder (average particle size 15μ, copper oxide content approximately 0)
．． 3 section) was dissected at 180, and 325 mesh bath industrial copper powder (
50 parts of hydroquinone-modified resol type phenolic resin (average particle size 20μ, copper oxide content approximately 1.0%) were reacted with 71 moles of hydroquinone, 0.2 moles of P-cresol, and 3.4 moles of formalin under an ammonia catalyst. The obtained ethylene glycol monobutyl ether-soluble hydroquinone-modified resol type phenol resin was diluted with ethylene glycol monobutyl ether to a resin content of 80%.

), 1.5 parts of dipyridyl, and 20 parts of a mixed medium of acetylacetone and diacetone alcohol (1:1) to prepare a copper-containing composition.

Using the obtained copper-containing composition, a screen printing machine (1
Using a 80 mesh Tetron screen, 10 sheets were printed on a ceramic substrate with a width of 2M and a total length of 9CrfL.

Next, this was dried in a heating dryer under an air atmosphere at 100° C. for 20 molecules, and then caloric thermosetting was performed at 160° C. for 40 minutes, and then it was taken out and left to cool to room temperature.

(This is referred to as cured product E.) The thickness of the conductive coating of cured product E was about 60 μm.

(b) Preparation of double conductive coating Apply solder flux (Solder Flux Y-2, Tamura Kaken Co., Ltd. product) to the entire conductive coating on the five cured products E.
After applying 0), the substrate was dried at a substrate surface temperature of 80° C. for two molecules, and then molten solder (Sn60φ) was applied to make the solder stick (250 to 260° C., 2 to 3 seconds).

The solder spread and adhered to the entire surface of the conductive film on cured product E without being repelled (this is referred to as cured product F).

). The thickness of the solder film was about 50 μm to 80 μm.

(c) Conductivity and conductivity retention test Cured products E and F were placed in a constant temperature and humidity chamber at a temperature of 40°C and a relative humidity of 95 degrees, left for a specified period of time, taken out, and left for one day and night (at room temperature). After that, the resistance of the circuit was measured using a Wheatstone bridge resistance measuring device, and the values are shown in Table 3.

From these results, it can be seen that in the case of the double conductive film coated with solder, no decrease in current conductivity was observed, whereas in the case of no coating, the conductivity deteriorated significantly.

Claims (1)

[Claims] 1. After coating or printing a copper-containing composition consisting of copper powder, copper in the form of a compound, and a resin containing a reducing agent on a base material, the copper in the form of a compound is reduced by the action of the reducing agent by causing this to react. Copper powder is connected to the resin by the metallic copper produced,
A double conductive film is formed by melting and coating solder on the conductive film obtained in this way.