JPH0953031A - Conductive paste and production of electrical circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive paste which has a low resistivity, a high conductivity, and improved adhesive properties and curability by compounding a conductive powder, an alkoxylated resol phenol resin, a specific unmodified resol phenol resin, and a solvent. SOLUTION: An electric circuit comprising a copper foil 2 is formed on a substrate 1 for a both-side-printed circuit board. A conductive circuit is formed inside a through-hole 4 by screen printing, etc., from a conductive paste 3 contg. a conductive powder, an alkoxylated resol phenol resin, an unmodified resol phenol resin obtd. from a phenol and an aldehyde, and a solvent. A part or the whole of the electrical circuit formed on the substrate 1 usually from a copper foil 2 may be formed from the paste 3. Printing an electric circuit on a substrate followed by pressing the resulting printed circuit is pref. since the conductivity is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste useful for electronic materials and a method for manufacturing an electric circuit forming substrate using the conductive paste.

[0002]

2. Description of the Related Art Conventionally, as one method for forming an electric circuit such as a printed wiring board and electronic parts, it is described in "Electronic Materials", October 1994, pages 42-46, published by the Industrial Research Board. In addition, a method of applying or printing a conductive paste is known. As a conductive component of this paste, silver, copper,
A metal powder such as nickel is used. The conductive paste using copper powder has a decrease in conductivity due to oxidation of copper, and various conductive pastes in which the surface oxidation of copper is suppressed have been proposed (JP-A-58-104699 and JP-A-60-1).
No. 30495 gazette), but a highly conductive paste is not obtained.

Since the conductive paste using silver powder has good conductivity, it is used as a wiring conductor or an electrode for printed wiring boards, electronic parts and the like. As a resin for silver paste, one using an epoxy resin, a phenol resin or the like is known (Japanese Patent Laid-Open No. 62-164737 and Japanese Patent Laid-Open No. 1-11).
65654, etc.). However, although they have good adhesiveness to the base material such as a paper phenol laminated plate and a glass epoxy laminated plate, they have a drawback that the adhesiveness to a copper foil is rather weak. In particular, there is a drawback in that the adhesiveness is deteriorated when a conductive paste pattern is formed and cured, the electric circuit is made to absorb moisture, then immersed in a solder bath and rapidly heated.

Therefore, in order to form a conductor having good conduction resistance, the conductor pattern is increased, the conductor width is devised,
Although measures such as forming an overcoat layer are taken, these were not fundamental solutions, but they had to be tested on an actual machine each time they were designed. For this reason, there are drawbacks that it takes time to design and the degree of freedom in design is low.

[0005]

The invention according to claims 1 and 2 has a low specific resistance and high conductivity, and changes in the specific resistance even under harsh conditions such as a thermal shock test and a humidity / humidity load test. The present invention provides a conductive paste which is small in size, does not peel even under severe conditions such as a moisture absorption dip test, and has sufficient adhesiveness. The invention described in claims 3 to 6 provides a conductive paste which is particularly excellent in conductivity among the inventions described in claims 1 and 2.

The invention according to claim 7 provides a conductive paste which is particularly excellent in adhesiveness among the inventions according to claims 1 and 2. The invention according to claim 8 provides a conductive paste which is particularly excellent in the effect of lowering the specific resistance among the inventions according to claims 1 and 2. The invention described in claim 9 provides a conductive paste having a great effect of improving curability in addition to the inventions described in claims 1 and 2. In addition to the inventions of claims 1 and 2, the inventions of claims 10 and 11 provide a conductive paste having an excellent balance between curability and pot life. The invention according to claim 12 provides a conductive paste which is particularly excellent in adhesiveness among the inventions according to claims 1 and 2 and further has excellent curability balance in addition to the inventions according to claims 1 and 2. is there.

The invention according to claim 13 has a low specific resistance,
It is highly conductive, has a small change in resistivity even under severe conditions such as a thermal shock test and a humidity / humidity load test, and does not peel off even under the severe conditions such as a moisture absorption dip test. A method for manufacturing a circuit-forming substrate is provided. According to a fourteenth aspect of the present invention, in addition to the thirteenth aspect of the present invention, there is provided a method of manufacturing an electric circuit forming substrate in which the conductive paste characteristics are particularly utilized.

[0008]

The present invention provides a conductive paste containing a conductive powder, an alkoxy group-containing resol-type phenol resin, an unmodified resol-type phenol resin produced from phenols and aldehydes as raw materials, and a solvent. Regarding The present invention also relates to a conductive paste containing an electroconductive powder, an alkoxy group-containing resol-type phenol resin, an unmodified resol-type phenol resin produced using phenols and aldehydes as raw materials, an epoxy resin, and a solvent. Further, the present invention relates to a conductive paste in which the conductive powder contains two kinds of conductive powder, that is, flat conductive powder and irregular-shaped conductive powder. The present invention also relates to the conductive paste, wherein the flat conductive powder and the irregular-shaped conductive powder are both silver or silver alloy.

Further, the present invention relates to the conductive paste, wherein the conductive powder contains two kinds of conductive powders having an aspect ratio of 6 or more and a conductive powder having an aspect ratio of 5 or less. . Further, the present invention relates to a conductive paste in which the conductive powder having an aspect ratio of 6 or more and the conductive powder having an aspect ratio of 5 or less are both silver or a silver alloy. Further, in the present invention, in this conductive paste, the alkoxy group-containing resol-type phenol resin has an alkoxylation rate of 5 to 100%.
The present invention relates to a conductive paste. Also, the present invention
This conductive paste relates to a conductive paste in which an unmodified resol-type phenolic resin produced using phenols and aldehydes as raw materials is produced using ammonia or a primary amine as a catalyst.

Further, the present invention relates to a conductive paste containing an acidic or basic compound as a curing accelerator in this conductive paste. Further, the present invention relates to a conductive paste in which, in this conductive paste, 5 to 30 parts by weight of all phenolic resin is used with respect to 100 parts by weight of conductive powder. Further, the present invention relates to a conductive paste in which 5 to 30 parts by weight of total phenol resin and 0.1 to 10 parts by weight of epoxy resin are used for 100 parts by weight of conductive powder in this conductive paste. Further, in the present invention, in the conductive paste, the mixing ratio of the alkoxy group-containing resol type phenol resin and the unmodified resol type phenol resin is 20/80 to 90 in terms of the former / the latter weight ratio.
/ 10 for the conductive paste.

The present invention also relates to a method of manufacturing an electric circuit forming substrate, characterized in that a part or the whole of an electric circuit is formed using the conductive paste described in any one of the above. Further, according to the present invention, the electric circuit formed by using the conductive paste in the method for manufacturing the electric circuit forming substrate is an electric circuit of a through hole portion of an electric circuit board having electric circuits on both sides, and The present invention relates to a method for manufacturing an electric circuit forming substrate, which is characterized in that electric circuits formed on both surfaces are conducted through the through holes.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the conductive paste of the present invention,
As the conductive powder, silver, copper, nickel, alloys of these,
Examples include various shapes such as silver plated copper and nickel. Among these, as the shape of the conductive powder, it is preferable to use a combination of flat conductive powder and irregular-shaped conductive powder or a combination of conductive powder having an aspect ratio of 6 or more and conductive powder having an aspect ratio of 5 or less. As a result, the probability of contact between the conductive powders can be improved, the conductivity of the electric circuit can be increased, and especially when the circuit is printed on a sheet-shaped substrate and the printed circuit is pressed, the conductivity can be increased. With only one kind of conductive powder or a combination of conductive powders having an aspect ratio other than the above, it is difficult to obtain a conductive paste having high conductivity as in the present invention.

In the present invention, the aspect ratio of the conductive powder means the ratio of the major axis and the minor axis of the particles of the conductive powder (major axis / minor axis). In the present invention, particles of conductive powder are mixed well in a curable resin having a low viscosity, the resin is cured as it is while the particles are allowed to settle by allowing it to stand, and the resulting cured product is cut in the vertical direction. The shape of the particles appearing on the cut surface is magnified and observed with an electron microscope, the major axis / minor axis of each particle is determined for at least 100 particles, and the average value thereof is used as the aspect ratio. Here, the minor axis is defined as a combination of two parallel lines that are in contact with the outside of the particle with respect to the particle that appears on the cut surface so as to sandwich the particle. Distance. On the other hand, the major axis is the two parallel lines perpendicular to the parallel line that determines the minor axis, and is the distance between the two parallel lines that are the longest among the combinations of the two parallel lines that contact the outside of the particle. is there. The rectangle formed by these four lines is sized to fit the particle exactly inside it. The specific method used in the present invention will be described later.

The flat conductive powder is a conductive powder composed of fine particles having a substantially flat shape, and for example, there is a flaky conductive powder. Irregularly shaped conductive powder is a conductive powder having a shape other than flat, and is called spherical, cubic, tetrahedral, lumpy, roughly spherical, etc., powder with a projection on the surface such as sucrose. It is a conductive powder of various shapes such as a body and a mixture thereof. Examples of the conductive powder containing various shapes of conductive powder include reduced silver powder. A conductive powder having an aspect ratio of 6 or more and a conductive powder having an aspect ratio of 5 or less can be used for each of the flat conductive powder and the irregular-shaped conductive powder.

In many cases, the conductive powder having an aspect ratio of 6 or more corresponds to a flat conductive powder, and there is also a so-called dendritic (also called dendrite) powder, which is also used in combination. be able to. As the conductive powder having an aspect ratio of 6 or more, an aspect ratio of 7 or more is preferable, an aspect ratio of 8 or more is more preferable, and an aspect ratio of 10 or more is further preferable, in that a highly conductive paste can be obtained. Therefore, in terms of both shape and aspect ratio, flat conductive powder having an aspect ratio of 7 or more is more preferable, and flat conductive powder having an aspect ratio of 8 or more is more preferable in terms of high conductivity, viscosity of conductive paste, and the like. A flat conductive powder having an aspect ratio of 10 or more is most preferable.

The average particle size of the particles of the flat conductive powder or the conductive powder having an aspect ratio of 6 or more is preferably 25 μm or less, from the viewpoint of not impairing printability, and 20 μm.
It is more preferably m or less, and further preferably 10 μm or less. The average particle diameter here can be measured by a laser scattering type particle size distribution measuring device. In the present invention, the measurement was performed using Mastersizer (manufactured by Malvan Co., Ltd.) as the device.

On the other hand, as the conductive powder having an aspect ratio of 5 or less, most of the above-mentioned irregular-shaped conductive powders are applicable. As the conductive powder having an aspect ratio of 5 or less, an aspect ratio of 4 or less is preferable, an aspect ratio of 3 or less is more preferable, and an aspect ratio of 2.5 or less is further preferable, since a highly conductive paste can be obtained. . The average particle size of the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less is preferably 20 μm or less in view of excellent printability.
It is more preferably not more than μm, still more preferably 3 to 10 μm. Here, the average particle size can be measured by a laser scattering type particle size distribution measuring device in the same manner as described above. In the present invention, the measurement was performed using a master sizer (manufactured by Malvern) as the device.

The material of the conductive powder is silver, as described above.
Examples include copper, nickel, alloys thereof, silver plated copper, nickel and the like. Among these, from the viewpoint of conductivity and oxidation resistance, copper or copper alloy whose surface is subjected to oxidation resistance treatment with silver, silver alloy or organic material, silver or silver alloy is preferable, and the same. From the viewpoint, it is more preferable that any conductive powder is silver or silver alloy.

As the silver alloy, it is preferable to use an alloy with palladium (for example, about 1 to 5% by weight in the silver alloy), platinum (for example, about 1% by weight in the silver alloy) and the like. Further, one of the methods for producing the above-mentioned silver powder is an in-liquid reduction method, and since the silver powder produced by this method is a fine powder having an average particle size of several μm, it is widely used as an industrial production method. There is. The in-liquid reduction method is a method in which silver is dissolved with an acid, then neutralized with an alkali, and then a reducing agent such as formalin and starch is added to the solution to reduce it into a fine powder. The powder obtained by this is called reduced silver powder, and its shape is close to a lump, but is not a constant shape but an irregular shape. This reduced silver powder can be used as an irregularly shaped conductive powder or a conductive powder having an aspect ratio of 5 or less in the present invention. Each conductive powder may be a silver-coated conductive powder in which a conductor other than silver or a silver alloy is coated with silver or a silver alloy.

The irregular-shaped conductive powder may be a silver-coated conductive powder as described above, but the coated conductor is preferably a conductor having a hardness higher than that of silver or a silver alloy. As such a conductor, for example, Co, Ni, C
Metal powders such as r, Cu and W or alloy powders thereof can be used, but among these, it is preferable to use copper powder or copper alloy powder. It is preferable to use this because when the electric circuit is pressurized, the irregular-shaped conductive powder bites into the flat silver powder or the silver alloy powder to increase the conductivity of the electric circuit. As the above-mentioned copper alloy powder, for example, alloy powders of copper and tin, copper and zinc, etc. are used.

To coat the surface of the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less with silver, there are methods such as displacement plating, electroplating, and electroless plating, and the irregular-shaped conductive powder or the aspect ratio is 5 or less. Since the adhesion between the conductive powder and silver described below is high and the running cost is low, it is preferable to perform the coating by the displacement plating method. The amount of silver coated on the surface of the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less is less than that of the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less from the viewpoints of cost and the effect of suppressing electrolytic corrosion. 3-
The range of 50% by weight is preferable, and the range of 3 to 20% by weight is more preferable.

It is preferable to use any one of the above silver-coated conductor powders because it has excellent migration resistance. As the silver-coated conductor powder, one in which a part of the conductor is exposed (exposed coating conductor powder) can be used. The exposed coated conductor powder can be used for each of the flat conductive powder or the conductive powder having an aspect ratio of 6 or more and the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less. The exposed area of the conductive powder is preferably 50% or less in order to obtain good conductivity, and 2
0% or less is more preferable.

Since the spherical silver-coated copper powder or silver-coated copper alloy powder after displacement plating has few contact points, the resistance tends to increase. Therefore, the spherical silver-coated copper powder or silver-coated copper alloy powder after displacement plating may be impacted to change the particle shape to a flat shape or an aspect ratio of 6 or more. Specifically, it can be deformed by a method such as a ball mill or a vibration mill.

In the total amount of conductive powder, the flat conductive powder or the conductive powder having an aspect ratio of 6 or more is preferably contained in an amount of 30 to 95% by weight from the viewpoint of conductivity and printability, and 50 to 50%.
More preferably, it is contained in an amount of 90% by weight. In addition, the irregular-shaped conductive powder or the conductive powder having an aspect ratio of 5 or less is preferably contained in an amount of 5 to 70% by weight, more preferably 10 to 50% by weight, from the viewpoint of conductivity and printability. Further, the conductive powder in the conductive paste is preferably 20 to 60% by volume, and more preferably 30 to 60% by volume, based on the total volume of the components excluding the solvent. If the ratio is less than 20% by volume, the resistance of the conductor tends to increase, and if it exceeds 60% by volume, it becomes economically disadvantageous and the adhesiveness tends to decrease.

In the present invention, it is important to use two kinds of phenol resins, that is, an alkoxy group-containing resol type phenol resin and an unmodified phenol resin produced from phenols and aldehydes as raw materials.
This makes it possible to improve the adhesiveness of the conductive paste and reduce the specific resistance.

The alkoxy group-containing resol-type phenolic resin used in the present invention is produced from phenols, aldehydes and alkyl alcohols containing an alkyl-substituted phenol or bisphenol as an essential component. This resin particularly contributes to the effect of the adhesiveness of the conductive paste in the present invention. Examples of the phenols include phenol, o-cresol, p-cresol, p
-Tert-butylphenol, pt-amylphenol, pt-octylphenol, pt-nonylphenol, xylenol and the like, alkyl-substituted phenol having one or two or more alkyl groups having 1 to 6 carbon atoms, bisphenol A, Examples thereof include bisphenols such as bisphenol F. These may be used alone or in combination of two or more. Among these, it is preferable to use an alkyl-substituted phenol or bisphenol having one alkyl group having 1 to 6 carbon atoms since the effect of adhesiveness is high, and it is more preferable to use 50% by weight or more of all phenols. It is particularly preferable to use 100% by weight because the effects such as adhesiveness are high.

As the aldehydes, those generating aldehydes such as formaldehyde, paraformaldehyde, tetramethylenehexamine and the like can be used.
As the alkyl alcohols, as preferable ones,
Methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol , 1-hexanol, 2-hexanol, 3-hexanol, and other alkyl alcohols having 1 to 6 carbon atoms are mentioned, and particularly preferable ones form a butoxy group in a phenol resin such as 1-butanol and 2-butanol. There are things. These can be used alone or in combination of two or more.

As a method for producing the above-mentioned alkoxy group-containing resol type phenol resin, a known method can be used and it is not particularly limited. In general, phenols and aldehydes are reacted in the presence of a basic catalyst such as a metal hydroxide or an amine, and then reacted with an alkyl alcohol to alkoxylate, or the alkyl alcohol is also present from the beginning. A method of alkoxylation is used.

In the present invention, the alkoxy group-containing resol type phenolic resin preferably has an alkoxylation rate, that is, an alkoxylated proportion of all methylol groups of 5 to 100%, more preferably 10 to 100%. , 30 to 100% is more preferable. Further, the alkoxy group in the resol-type phenol resin preferably has a range of 0.1 to 2 alkoxy groups per benzene ring, more preferably 0.3 to 1.5, and more preferably 0.5.
The range of up to 1.2 is more preferable. When the alkoxylation ratio is less than 5% or when the number of alkoxy groups is too small, the adhesiveness of the conductive paste tends to decrease. The alkoxylation rate and the number of alkoxy groups can be measured based on nuclear magnetic resonance spectrum analysis (hereinafter referred to as NMR method). As for the molecular weight of the resol type phenol resin in the present invention, one having a weight average molecular weight of 1,000 to 500,000 is preferable since various properties as a conductive paste are excellent. The molecular weight can be determined by measuring by gel permeation chromatography and converting to standard polystyrene.

The unmodified phenol resin produced by using phenols and aldehydes as raw materials is one which has not been modified by alkoxy modification such as the above-mentioned alkoxy group-containing resol type phenol resin. It is manufactured from only raw materials. As the phenols and aldehydes used,
The above-mentioned examples are mentioned, and there is no particular limitation. As a method for producing the unmodified resol-type phenol resin, a known method can be used and is not particularly limited. Generally, a method of reacting phenols and aldehydes in the presence of a basic catalyst such as a metal hydroxide or an amine is used. Among these, those using primary amines such as ammonia, methylamine and ethylamine as the catalyst are particularly preferable because they are excellent in the effect of lowering the specific resistance of the conductive paste.

The molecular weight of the unmodified resol type phenol resin in the present invention is 1,000 in terms of weight average molecular weight.
It is preferable that those having a content of up to 500,000 are excellent in various properties as a conductive paste. The molecular weight can be determined by measuring by gel permeation chromatography and converting to standard polystyrene. The mixing ratio of the alkoxy group-containing resol-type phenolic resin and the unmodified resol-type phenolic resin is 20 in terms of the former / latter weight ratio because of the excellent balance between adhesiveness and reduction in specific resistance.
/ 80 to 90/10 is preferable, 30/70 to 70/3
0 is more preferred.

The epoxy resin used in the present invention includes various kinds such as bisphenol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, epoxidized polybutadiene, flexible epoxy resin and polyfunctional epoxy resin. Epoxy resin. Among these, bisphenol-type epoxy resins are preferred because they are particularly excellent in curability and conductivity.
These resins can be used alone or in combination of two or more.

In the present invention, the object of the present invention can be achieved by using the above-mentioned two kinds of resol-type phenolic resins as a binder, but it is more preferable to use two kinds of resol-type phenolic resins and epoxy resins in combination. An electric circuit having excellent adhesiveness and low resistance of the cured product can be obtained. The weight ratio of the total phenolic resin to the epoxy resin is preferably 95/5 to 50/50 in terms of the former / the latter (weight ratio) from the viewpoint of the balance between adhesiveness and curability, and 9
More preferably, it is set to 0/10 to 60/40.

In the conductive paste of the present invention, it is preferable to further use a curing accelerator because the curing property can be improved. Examples of the curing accelerator include an acidic or basic compound, and preferred are p-toluenesulfonic acid, p-toluenesulfonamide, sulfanilic acid,
Examples thereof include sulfamine, oxalic acid, phosphoric acid, and 1,8-diazobicyclo- (5,4,0) -undecene-7. Among these, an acidic compound is preferable, and oxalic acid is particularly preferable because the obtained conductive paste is particularly excellent in storage stability.

In addition to the above components, fine graphite powder, a corrosion inhibitor for the conductive powder, and the like may be contained, if necessary, for the purpose of preventing oxidation of the conductive powder. The fine graphite powder and the corrosion inhibitor are added as necessary, but if added, the content of the fine graphite powder is 1 to the conductive paste.
It is preferably in the range of 10% by weight. The corrosion inhibitor is preferably in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of the binder. Further, a coupling agent such as titanium-based or silane-based coupling agent may be contained for the purpose of improving the dispersibility of the conductive paste. If a coupling agent is added, its content is 0.05 to 100 parts by weight of the binder.
It is preferably in the range of 3 parts by weight.

The above components are generally dissolved or dispersed in a solvent, usually an organic solvent. The organic solvent is not particularly limited, but preferable examples include ethyl cellosolve, butyl cellosolve, cellosolve acetate, carbitol, butyl carbitol and the like.

The amount of each component dissolved or dispersed in the solvent is preferably 5 to 30 parts by weight, more preferably 10 to 20 parts by weight, based on 100 parts by weight of the conductive powder. When an epoxy resin is also used, 5 to 30 parts by weight of total phenolic resin and 0.1 to 10 parts by weight of epoxy resin are preferable, and 10 to 20 parts by weight of total phenolic resin and epoxy resin are used per 100 parts by weight of conductive powder. 0.
It is more preferably 5 to 8 parts by weight. If the amount of total phenolic resin is less than 5 parts by weight, it is difficult to sufficiently bond the conductive powder, so the effect of improving the conductivity tends to be small, and if it exceeds 30 parts by weight, excess resin tends to exist between the conductive powders. Therefore, the effect of improving the conductivity tends to be small. Also,
If the amount of the epoxy resin is less than 0.1 parts by weight, the effect of improving the adhesion to the copper foil tends to be small, and if it exceeds 10 parts by weight, the effect of improving the conductivity tends to be small.

When a curing accelerator is further used, its addition amount is preferably 0.05 to 10% by weight, and preferably 1 to 3% by weight, based on the total amount of the phenol resin or the phenol resin and the epoxy resin. Is more preferable. 0.05
If it is less than 10% by weight, the curability tends to be insufficient and the properties as a conductive paste tend to deteriorate, and if it exceeds 10% by weight, the pot life tends to decrease. The mixing ratio of the organic solvent and other components is not particularly limited,
In terms of printability (bleeding and sagging),
50 wt% is preferable, and 15 to 35 wt% is more preferable.

Next, a method for manufacturing an electric circuit forming substrate, which is characterized in that a part or the whole of an electric circuit is formed by using the conductive paste, will be described. As a substrate for forming an electric circuit, a paper phenol laminated plate, a glass epoxy laminated plate, a composite laminated plate using glass nonwoven fabric and glass cloth in combination, a laminated plate such as a polyamide imide laminated plate, a polyester such as polyethylene terephthalate, a polyamide imide, etc. A film or the like can be used.
The method for forming an electric circuit on these substrates is not particularly limited, but a screen printing method, a computer-controlled dispenser method, and the like are preferable in terms of workability, productivity, and the like.

As an electric circuit formed by the conductive paste, for example, a through hole is formed through an electric circuit board having copper foil circuits on both sides, and an electric circuit for conducting the electric circuits on both sides through the through hole is used. It can be mentioned as a preferable one that takes advantage of the characteristics of this conductive paste. Schematic diagrams of this electric circuit are shown in FIGS. 1 and 2. FIG. 1 is a plan view and FIG. 2 is a sectional view. An electric circuit made of copper foil 2 is formed on a substrate 1 of a double-sided printed wiring board. A conductive circuit made of the conductive paste 3 is formed in the through hole 4 by screen printing or the like. In addition,
The conductive paste can form a part or all of an electric circuit instead of the copper foil circuit itself generally formed on the substrate, or a jumper circuit. It is preferable to print an electric circuit on the substrate and press the printed circuit because the conductivity can be further improved.

[0041]

EXAMPLES Examples of the present invention will be described below. Example 1 60 parts by weight of a butoxy group-containing resol type phenolic resin synthesized from cresol, formaldehyde and butanol (Hitachi 401 manufactured by Hitachi Chemical Co., Ltd.)
0) desolvated, butoxylation rate 95%, number of butoxy groups per benzene ring is 1.2, weight average molecular weight is about 2,500, unmodified resol type phenol resin (Gunei Chemical Industry Co., Ltd.) Co., Ltd. product name cash register top PL220
7) desolvated, a resin having a weight average molecular weight of about 2,000 produced using ammonia as a catalyst, and a bisphenol A type epoxy resin (produced by Yuka Shell Epoxy Co., Ltd.,
Product name Epicoat 1004) 20 parts by weight of which have been dissolved by heating in advance, and then cooled to room temperature, 2 parts by weight of oxalic acid, 20 parts by weight of ethyl carbitol, and 20 parts by weight of butyl cellosolve are added and uniformly mixed to obtain a resin composition. It was a thing.

Next, silver powder, a flaky conductive powder having an aspect ratio of 8 (manufactured by Tokuriki Kagaku Kenkyusho, trade name TCG-1,
The average particle size is 5 μm) and the aspect ratio is 250 parts by weight.
3 silver powder having an average particle diameter of 7 μm (manufactured by Rare Metallic Co., Ltd.) 5
0 part by weight was added to the resin composition and uniformly dispersed with a stirrer and a triple roll to obtain a conductive paste. The volume content of the conductive powder is 26%.

The circuit pattern 5 shown in FIG. 3 was printed by the screen printing method using the above-mentioned conductive paste and then heat-cured. The substrate material is a paper phenol substrate (manufactured by Hitachi Chemical Co., Ltd., trade name MCL437F, thickness 1.6 mm) laminated with a copper foil having a thickness of 35 μm. The heating and curing conditions were 80 ° C. for 2 hours and 155 ° C. for 45 minutes. The specific resistance was 55 μΩ · cm. As a result of performing a thermal shock test on the obtained electric circuit forming substrate, the rate of change in specific resistance was 5%. In addition, the same as the above, on a copper foil of a paper phenol substrate laminated with copper foil, 50 mm square and 30 mm thick
After printing and curing a solid surface of μm, it was left in a thermo-hygrostat at 40 ° C. and a relative humidity of 95% for 120 hours, and then 260
After performing a moisture absorption dip test of immersing in a solder bath at 0 ° C. for 5 seconds, a cross cut test was conducted in which a cutter was put in a 1 mm square (10 × 10) and peeled off with cellophane tape, but no peeling was found. The cooling and heating test conditions were 125 ° C., 30 minutes and −65 ° C., 30 minutes as one cycle, and this was 100
Cycled.

Example 2 A flaky silver powder 500 having an aspect ratio of 8 as described in Example 1
Parts by weight and silver powder 1 having an aspect ratio of 2.3 described in Example 1
00 parts by weight was uniformly mixed and dispersed in 142 parts by weight of the resin composition described in Example 1 to obtain a conductive paste. The volume content of the conductive powder is 41%. The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated. As a result, the specific resistance was 40 μΩ · cm. As a result of performing a thermal shock test on the electric circuit forming substrate,
The rate of change in specific resistance was 5%, and the result of the cross-cut test after the moisture absorption dip test was that there was no peeling.

Example 3 The flaky silver powder 420 having an aspect ratio of 8 described in Example 1 is used.
Parts by weight and silver powder 8 having an aspect ratio of 2.3 described in Example 1
0 part by weight was uniformly mixed and dispersed in 142 parts by weight of the resin composition described in Example 1 to obtain a conductive paste. The volume content of the conductive powder is 36%. The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated. As a result, the specific resistance was 43 μΩ · cm. As a result of the thermal shock test of the electric circuit forming substrate, the rate of change in specific resistance was 5%, and the result of the cross-cut test after the moisture absorption dip test was that there was no peeling.

Example 4 The flaky silver powder 420 having an aspect ratio of 8 described in Example 1 is used.
Parts by weight and silver powder 8 having an aspect ratio of 2.3 described in Example 1
0 part by weight was uniformly mixed and dispersed in 142 parts by weight of the resin composition described in Example 1 to obtain a conductive paste. The volume content of the conductive powder is 36%. The electric circuit forming substrate of Example 1 was prepared using the conductive paste, and then the printed circuit was densified with a hot press (100 ° C., 100 kg / cm ² (about 9.8 × 10 ⁶ Pa)). Was evaluated. As a result, the specific resistance was 18 μΩ · cm. Further, as a result of the thermal shock test of the electric circuit forming substrate, the rate of change in resistivity is 5%.
The result of the cross-cut test after the moisture absorption dip test was that there was no peeling.

Example 5 75 parts by weight of the butoxy group-containing resol type phenolic resin described in Example 1 and 25 parts by weight of the unmodified resol type phenolic resin described in Example 1 were dissolved by heating in advance and then cooled to room temperature. Oxalic acid 2 parts by weight, ethyl carbitol 2
0 parts by weight and 20 parts by weight of butyl cellosolve were added and uniformly mixed to obtain a resin composition. Next, 250 parts by weight of flaky silver powder having an aspect ratio of 8 described in Example 1 and 50 parts by weight of silver powder having an aspect ratio of 2.3 described in Example 1 were added to the resin composition, and the method described in Example 1 was added. Was uniformly mixed and dispersed to obtain a conductive paste. Volume content of conductive powder is 2
It is 5.7%. The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated.
As a result, the specific resistance was 51 μΩ · cm. As a result of the thermal shock test of the electric circuit forming substrate, the rate of change in specific resistance was 7%, and the result of the crosscut test after the moisture absorption dip test was that there was no peeling.

The specific measuring method of the aspect ratio in the present invention is shown below. 8 g of a base material (No. 20-8130) of a low-viscosity epoxy resin (manufactured by Buehler) and 2 g of a curing agent (No. 20-8132) are mixed, and the conductive powder 2 is added thereto.
g were mixed and dispersed well, followed by vacuum degassing at 30 ° C. as it was, and then allowed to stand at 30 ° C. for 6 to 8 hours to precipitate and harden the particles. Thereafter, the obtained cured product was cut in the vertical direction, the cut surface was magnified 2000 times with an electron microscope, and the long diameter / short diameter was determined for 100 particles that appeared on the cut surface,
The average value was used as the aspect ratio.

Comparative Example 1 80 parts by weight of a resole phenolic resin (a resin synthesized from phenol and formaldehyde, manufactured by Hitachi Chemical Co., Ltd., trade name VP13N, weight average molecular weight of about 1,800) and a bisphenol A type epoxy resin ( 20 parts by weight of Yuka Shell Epoxy Co., Ltd., trade name Epikote 1004) was heated and dissolved in advance, and then cooled to room temperature, and oxalic acid 2 was added.
By weight, 20 parts by weight of ethyl carbitol and 20 parts by weight of butyl cellosolve were added and uniformly mixed to obtain a resin composition.

Then, silver powder having an aspect ratio of 8 as flaky conductive powder (manufactured by Tokuriki Kagaku Kenkyusho, trade name TCG-1,
420 parts by weight with an average particle diameter of 5 μm and an aspect ratio of 2.
3 silver powder having an average particle diameter of 7 μm (manufactured by Rare Metallic Co., Ltd.) 8
0 part by weight was added to the above resin composition and uniformly mixed and dispersed by the method described in Example 1 to obtain a conductive paste. The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated. As a result, the specific resistance is 6
It was 2 μΩ · cm. As a result of the thermal shock test of the electric circuit forming substrate, the rate of change in specific resistance was 10%, and the result of the cross-cut test after the moisture absorption dip test was peeling of 53%.

Comparative Example 2 80 parts by weight of a resole phenolic resin (a resin synthesized from phenol and formaldehyde, manufactured by Hitachi Chemical Co., Ltd., trade name VP13N, weight average molecular weight of about 1,800) and a bisphenol A type epoxy resin ( 20 parts by weight of Yuka Shell Epoxy Co., Ltd., trade name Epikote 1004, was heated and dissolved in advance and then cooled to room temperature, 2 parts by weight of oxalic acid, 20 parts by weight of ethyl carbitol, 20 parts by weight of butyl cellosolve. Was added and mixed uniformly to obtain a resin composition. Then, the aspect ratio of the flaky conductive powder is 8
Of silver powder (manufactured by Tokuriki Kagaku Kenkyusho, trade name TCG-1, average particle diameter 5 μm) of 500 parts by weight is added to the resin composition,
By the method described in Example 1, the conductive paste was uniformly mixed and dispersed. The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated. As a result, the specific resistance was 80 μΩ · cm. As a result of the thermal shock test of the electric circuit forming substrate, the rate of change of the specific resistance was 5%, and the result of the crosscut test after the moisture absorption dip test was that the peeling was 62%.

Comparative Example 3 80 parts by weight of a resole phenolic resin (a resin synthesized from phenol and formaldehyde, manufactured by Hitachi Chemical Co., Ltd., trade name VP13N, weight average molecular weight of about 1,800) and a bisphenol A type epoxy resin ( 20 parts by weight of Yuka Shell Epoxy Co., Ltd., trade name Epikote 1004) was heated and dissolved in advance, and then cooled to room temperature, and oxalic acid 2 was added.
By weight, 20 parts by weight of ethyl carbitol and 20 parts by weight of butyl cellosolve were added and uniformly mixed to obtain a resin composition. Next, 500 parts by weight of silver powder (made by Rare Metallic Co., Ltd.) having an aspect ratio of 2.3 and an average particle diameter of 7 μm was added to the resin composition, and uniformly mixed and dispersed by the method described in Example 1 to obtain a conductive paste. . The electric circuit forming substrate described in Example 1 was produced using the conductive paste, and its characteristics were evaluated. As a result, the specific resistance was 150 μΩ · cm. As a result of the thermal shock test of the electric circuit forming substrate, the rate of change in specific resistance was 7%, and the result of the cross-cut test after the moisture absorption dip test was that peeling was 67%.

[0053]

The conductive paste according to claims 1 and 2 is
It is a conductive paste having a low specific resistance and high conductivity, and is an excellent one in which the change in the specific resistance is small even under severe conditions such as a thermal shock test and a wet and medium load test. In addition, it does not peel even under severe conditions such as a moisture absorption dip test, and thus has excellent adhesiveness, and also has excellent curability. The conductive pastes according to claims 3 to 6 have the effects of the conductive pastes according to claims 1 and 2, and are particularly effective in improving conductivity.

The conductive paste according to claim 7 is the conductive paste according to claim 1.
And the effect of the conductive paste described in 2 are exhibited, and particularly the effect of improving the adhesiveness is large. The conductive paste according to the eighth aspect has the effects of the conductive paste according to the first and second aspects, and particularly has a large effect of lowering the specific resistance. The conductive paste according to the ninth aspect has the effects of the conductive paste according to the first and second aspects, and in addition to the conductive paste according to the first and second aspects, has a large effect of improving the curability. The conductive paste according to claims 10 and 11 has the effects of the conductive paste according to claims 1 and 2, and is excellent in balance between curability and pot life in addition to the conductive paste according to claims 1 and 2. is there. The conductive paste according to the twelfth aspect has the effects of the conductive paste according to the first and second aspects, and is particularly excellent in the balance between adhesiveness and curability.

In the method for manufacturing an electric circuit forming substrate according to the thirteenth aspect of the present invention, the specific resistance is low, the conductivity is high, and the change in specific resistance is small even under severe conditions such as a thermal shock test and a humidity and humidity load test. An excellent electric circuit can be formed. Further, the electric circuit is particularly excellent in adhesiveness because it does not peel even under severe conditions such as a moisture absorption dip test. The method for producing an electric circuit forming substrate according to claim 14 has the effects of the method for producing an electric circuit forming substrate according to claim 13, and in addition to the method for producing an electric circuit forming substrate according to claim 13, An electric circuit in which the characteristics of the conductive paste are utilized can be formed.

[Brief description of drawings]

FIG. 1 is a plan view of a through-hole portion of a double-sided wiring board in which an electric circuit is formed with a conductive paste of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a plan view showing a state of a circuit pattern printed in this example.

[Explanation of symbols]

 1 substrate 2 copper foil 3 conductive paste 4 through hole 5 circuit pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Kikuchi 3-3-1 Ayukawa-cho, Hitachi-shi, Ibaraki Yamazaki Plant, Hitachi Chemical Co., Ltd.

Claims (14)

[Claims] 1. A conductive paste containing a conductive powder, an alkoxy group-containing resol-type phenol resin, an unmodified resol-type phenol resin produced from phenols and aldehydes as a raw material, and a solvent. 2. A conductive paste containing conductive powder, an alkoxy group-containing resol-type phenol resin, an unmodified resol-type phenol resin produced using phenols and aldehydes as raw materials, an epoxy resin, and a solvent. 3. The conductive paste according to claim 1, wherein the conductive powder contains two kinds of conductive powder, that is, flat conductive powder and irregular-shaped conductive powder. 4. The conductive paste according to claim 1, wherein the flat conductive powder and the irregular conductive powder are both silver or a silver alloy. 5. The conductive paste according to claim 1 or 2, wherein the conductive powder contains two kinds of conductive powder having an aspect ratio of 6 or more and a conductive powder having an aspect ratio of 5 or less. 6. The conductive paste according to claim 1, 2 or 5, wherein each of the conductive powder having an aspect ratio of 6 or more and the conductive powder having an aspect ratio of 5 or less is silver or a silver alloy. 7. The conductive paste according to claim 1, wherein the alkoxy group-containing resol-type phenol resin has an alkoxylation rate of 5 to 100%. 8. The unmodified resol type phenolic resin produced from phenols and aldehydes as raw materials is produced using ammonia or a primary amine as a catalyst. Conductive paste. 9. The conductive paste according to claim 1, which contains an acidic or basic compound as a curing accelerator. 10. The whole phenol resin is used in an amount of 5 to 30 parts by weight based on 100 parts by weight of the conductive powder.
Alternatively, the conductive paste according to any one of 3 to 9. 11. A total of 5 to 30 parts by weight of a phenolic resin and 0.1 to 1 of an epoxy resin with respect to 100 parts by weight of conductive powder.
The conductive paste according to claim 2, wherein 0 part by weight is used. 12. The mixing ratio of the alkoxy group-containing resol-type phenolic resin and the unmodified resol-type phenolic resin is
The conductive paste according to claim 1, wherein the weight ratio of the former / the latter is 20/80 to 90/10. 13. A method of manufacturing an electric circuit forming substrate, wherein a part or the whole of an electric circuit is formed using the conductive paste according to any one of claims 1 to 12. 14. An electric circuit formed by using a conductive paste is an electric circuit of a through hole portion of an electric circuit board having an electric circuit on both surfaces thereof, and the electric circuit formed on both surfaces by the conductive paste through the through holes. 14. The method for manufacturing an electric circuit forming substrate according to claim 13, wherein the electric field is conducted.