JPH05114772A - Printed wiring board formed by use of conductive paste - Google Patents

Abstract

PURPOSE:To enable conductive powder to be enhanced in oxidation stability by controlling it in affinity and reactivity to the surface of metal by using conductive paste which contains hydroxystyrene copolymer of specific weight- average molecular weight and/or its derivative as organic binder. CONSTITUTION:In hydroxystyrene copolymer and/or its derivative represented by a formula: m and n are set to arbitrary numbers until the copolymer concerned becomes 10-2 million in weight-average molecular weight and so set as to satisfy formulas, m>=0 and n>=3; k, p, and u are so set as to satisfy formulas, 0<=k<=2, 0<=p<=2, and 0<=u<=2 (k, p, and u denote average values in copolymer); R<1>-R<3> indicate alkyl groups whose number of carbon or hydrogen atoms is 1-5; X indicates polymerizable vinyl monomer; and Y and Z are the same or different in kinds and selected from prescribed substituting groups or alkyl or aryl groups whose number of carbon atoms is 1-18. It is preferable that the compounding ratio of the copolymer to thermosetting resin is set to 95/5-40/60. It is preferable that the compounding ratio of conductive powder to conductive paste except solvent ranges from 50 to 95wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a printed wiring board.
More specifically, it relates to a printed wiring board using a conductive paste containing a hydroxystyrene copolymer and / or a derivative thereof as an organic binder.

[0002]

2. Description of the Related Art A conductive silver paste containing silver powder as a conductive filler is used to print a printed wiring board on a wiring board, which is excellent in terms of conductivity. Therefore, various attempts have hitherto been made to manufacture circuit boards using a conductive silver paste. But,
It has been pointed out that, in addition to the problem that the conductive silver paste is expensive, the use of silver powder causes the migration of silver when left under high humidity under load. .. It has been pointed out that due to this problem, a high-density circuit cannot be obtained, interlayer insulation failure occurs when multiple layers are used, and the stability of the resistance formed between the electrodes cannot be obtained. .. As a method of eliminating these problems, in recent years, research on circuit fabrication using a copper paste, which is less expensive than silver and has migration resistance, has been widely conducted.

However, in the case of a circuit using a copper paste, it has been pointed out that the migration phenomenon can be prevented, but on the other hand, the conductivity is inferior, and the conductivity is liable to deteriorate due to oxidative deterioration. In addition, the conventional copper paste does not have good adhesion to the resist used for the printed wiring board, depending on the type of resist, and adheres to the metal surface such as copper, gold or platinum that forms the contact terminals on the board. However, it was pointed out that the conventional copper paste is inferior to the conventional one. As a proposal for solving such a problem, an attempt to produce a printed wiring board by using a conductive paint obtained by dispersing fine copper powder in a lacquer type resin has been reported (Japanese Patent Publication No. Sho 58-24032). Bulletin). However, although it is described that high conductivity and moisture resistance can be obtained by this method, it is pointed out that the pot life is short because of its poor dispersion stability.

As described above, the printed wiring board using the conductive copper paste is inexpensive and has excellent migration resistance, but on the other hand, it has many characteristics such as conductivity, moisture resistance reliability and adhesion reliability. However, there are still some problems, and the printed wiring board obtained by using a conductive paste that solves these problems has not yet been obtained.

Therefore, an object of the present invention is to provide a printed wiring board manufactured by using a conductive copper paste having improved conductivity, moisture resistance reliability and adhesion reliability, and more excellent migration resistance. is there.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, the present invention has made earnest studies to maintain and improve conductivity and improve adhesion with a substrate by the oxidation stability of a conductive paste. By using a conductive paste containing a polymer and / or its derivative as a binder component, affinity with the metal surface and the insulating layer surface,
It has been found that the reactivity can be increased and the above-mentioned object can be achieved, and the present invention has been completed.

That is, the gist of the present invention is a conductive paste containing a conductive powder, an organic binder, an additive and a solvent as essential components, wherein the organic binder has a weight average molecular weight of 1
The present invention relates to a printed wiring board obtained by printing an electric circuit using a conductive paste containing a hydroxystyrene-based copolymer and / or a derivative thereof and then curing the printed circuit.

According to the present invention, the affinity and reactivity with respect to the metal surface are controlled by adjusting the type and density of the substituents introduced into the organic polymer contained in the organic binder, and the conductive powder It is possible to improve the oxidation stability and the adhesion to a metal or an insulating layer.

Examples of the organic polymer contained in the organic binder in the present invention include the following general formula (1):

[Chemical 3] [Wherein, m ≧ 0, n ≧ 3, and an arbitrary number until the weight average molecular weight of the organic polymer of the general formula (1) becomes 1,000 to 2,000,000; 0 ≦ k ≦ 2; 0 ≦ p ≦ 2; 0 <u ≦ 2
(However, k, p, and u represent average values in the polymer.); R
^{1 to} R ³ are H or an alkyl group having 1 to 5 carbon atoms; X is a polymerizable vinyl monomer; Y and Z are the same or different, and

[Chemical 4] Or selected from an alkyl group or an aryl group having 1 to 18 carbon atoms (wherein M is H, an alkali metal,
Organic cations such as alkaline earth metals or amines; Y
¹ and Y ⁴ are halogens; Y ²⁻ and Y ³⁻ are counterions such as halogen ions, organic acid anions and inorganic acid anions; W is S
Or O; R ^{4 to} R ⁸ are the same or different and are linear or branched alkyl groups, alkyl derivative groups, aromatic groups,
Alternatively, H, and R ⁶ and R ⁷ may form a ring with the N group. R ^{9 to} R ¹⁵ are the same or different and are a linear or branched alkyl group, an alkyl derivative group, an aromatic group, or H; q, s, t is 0 or 1, and r is 0, 1
Or 2)], and a hydroxystyrene-based copolymer and a derivative thereof.

In the above general formula (1), m, n, k,
p and u are arbitrary numbers (real numbers) within a certain fixed range. When considering the monomers constituting the polymer, k and p are naturally integers, when considering each block of the constitutional unit, m is an integer, and when considering each molecule,
n is an integer. However, polymers are, by their nature, mixtures, and it is more appropriate to regard the properties of the polymer as the properties of the mixture, rather than the individual building blocks. Therefore, in the present invention, m,
n, k, p and u are displayed as average values in the polymer.

The hydroxystyrene copolymer represented by the general formula (1) or a derivative thereof may or may not have a substituent represented by Y or Z in the general formula (1). A copolymer of hydroxystyrene-based monomers such as hydroxystyrene, hydroxy-α-methylstyrene or hydroxy-α-ethylstyrene, or a copolymer of these hydroxystyrene-based monomers with another polymerizable vinyl-based monomer. It may be a copolymer with the monomer (X). The hydroxystyrene-based monomer of the polymerized unit may be an ortho body, a meta body, a para body or a mixture thereof, but a para body or a meta body is preferable.

Other vinyl-based monomers (X) in the case of copolymers include anionic or cationic ionic monomers, nonionic monomers, methacrylates, vinyl esters, vinyl ethers, Malate, fumarate,
Known compounds such as α-olefin can be mentioned.

Specific examples of these compounds include acrylic acid, methacrylic acid, maleic acid, anhydrides thereof and unsaturated carboxylic acid monomers such as monoalkyl esters and carboxyethyl vinyl ether thereof, styrenesulfonic acid and allyl. Unsaturated sulfonic acid monomers such as sulfonic acid, unsaturated phosphoric acid monomers such as vinylphosphonic acid and vinyl phosphate, α, β-unsaturated carboxylic acid amides such as acrylamide and methacrylamide, methyl acrylate,
Methyl methacrylate, ethyl acrylate, and diesters of maleic acid and fumaric acid, esters of α, β-unsaturated carboxylic acids, substituted amides of unsaturated carboxylic acids such as methylolacrylamide, α of acrylonitrile, methacrylonitrile, etc. A nitrile of β-unsaturated carboxylic acid,
In addition to vinyl acetate, vinyl chloride, chlorovinyl acetate, etc.,
Divinyl compounds such as divinylbenzene, vinylidene compounds, aromatic vinyl compounds represented by styrene, heterocyclic vinyl compounds represented by vinylpyridine and vinylpyrrolidone, vinylketone compounds, monoolefin compounds such as propylene, conjugated diolefins such as butadiene. Compounds, allyl compounds such as allyl alcohol, and one or more monomers selected from the group of monomers represented by glycidyl methacrylate and the like are used.

Of these monomers, there is no particular limitation, and any of them can be used, but specifically, the following are preferably used.

[Chemical 5]

In the present invention, the copolymerization of hydroxystyrene-based monomers alone may be carried out as described above, but in the case of copolymerization with another polymerizable vinyl-based monomer (X), The ratio of hydroxystyrene-based monomer / other vinyl-based monomer (X) is preferably 1/10 to 20/1 in terms of molar ratio.

If the proportion of the vinyl-based monomer (X) exceeds 10 times the molar amount (molar ratio) of the hydroxystyrene-based monomer, the effect of the hydroxystyrene-based monomer will not be exhibited, which is not preferable. If the ratio of the body (X) is less than 1/20, the effect of copolymerization is not exerted, so it is not necessary to purposely copolymerize with the vinyl-based monomer (X). Therefore,
In the present invention, the number of such vinyl monomers (X) is m ≧ 0.

Examples of the substituent of the hydroxystyrene-based monomer include the following. (I)

[Chemical 6] Here, M is an alkali metal or an alkaline earth metal, and for example, Li, Na, K, Mg, Ca, Sr, Ba and the like are suitable. The introduction of the sulfone group can be achieved by an ordinary sulfonation method using fuming sulfuric acid or sulfuric anhydride as a sulfonating agent.

(B)

[Chemical 7] R ^{4 to} R ⁸ are the same or different and are linear or branched alkyl groups, alkyl derivative groups, aromatic groups or H, and R ⁶ and R ⁷ may form a ring with N group. I don't care. Y ^2- represents a counter ion such as a halogen ion, an organic acid anion and an inorganic acid anion. here,
Examples of the straight chain or branched chain alkyl group include those having 1 to 36 carbon atoms, and as the alkyl derivative group, a hydroxyalkyl group, an aminoalkyl group, a phosphoalkyl group,
Examples thereof include a mercaptoalkyl group, and examples of the aromatic group include a benzyl group substituted with a linear or branched alkyl group having 1 to 16 carbon atoms. Preferably, a linear or branched alkyl group, a hydroxyalkyl group, or an aromatic group substituted with a linear or branched alkyl group having 1 to 5 carbon atoms is used. The introduction of the above-mentioned tertiary amino group can be easily carried out by a Mannich reaction using, for example, a dialkylamine and formaldehyde, —CH ₂ —N (R ⁶ ) (R ⁷ ).
Is obtained. The introduction of the quaternary ammonium base can be easily carried out, for example, by the Menschutkin reaction of the above-mentioned tertiary amino compound with an alkyl halide.

[Chemical 8] Is obtained.

(C)

[Chemical 9] Here, R ⁴ and R ⁵ are the same as defined above, R ^{9 to} R ¹² are the same or different, and are linear or branched alkyl groups,
Represents an alkyl derivative group, an aromatic group, or H. W is S or O, q is 0 or 1, r is 0, 1
Or 2 is shown. Here, the linear or branched alkyl group has a carbon number of 1 to 36, the alkyl derivative group includes a hydroxyalkyl group, an aminoalkyl group, a mercaptoalkyl group, a phosphoalkyl group, and the like, and the aromatic group is Examples thereof include a phenyl group substituted with a straight chain or branched chain alkyl group having 1 to 16 carbon atoms. Preferable one is a linear or branched alkyl group having 18 carbon atoms, a hydroxyalkyl group, or an aromatic group substituted with a linear or branched alkyl group having 1 to 5 carbon atoms. The compound represented by the formula (C-1) is, for example, as disclosed in JP-A-53-71190, a hydroxystyrene-based copolymer which is converted into a phosphoric acid or a phosphoric acid ester group-introduced product after methylolation. Obtained by reacting. The hydroxystyrene-based copolymer represented by the formula (C-2) is disclosed, for example, in JP-A-53
As disclosed in Japanese Patent No. 47489, a hydroxystyrene copolymer is first halogenated or halomethylated and then reacted with a trivalent phosphorus compound (Arbuzov reaction).
And then subjecting it to thermal rearrangement.

(D)

[Chemical 10] Here, R ⁴ and R ⁵ are the same as described above, and R ¹³ , R ¹⁴ and R
¹⁵ is the same or different and represents a linear or branched alkyl group, an alkyl derivative group, an aromatic group or H. S represents 0 or 1. Y ^3- represents a counter ion such as a halogen ion, an organic acid anion and an inorganic acid anion. The production of the hydroxystyrene-based copolymer containing the phosphonium group is carried out by reacting a hydrogen halide and formaldehyde to form a halogenomethylation (for example, -CH ₂ C
It can be easily obtained by carrying out (1) conversion and then acting with trivalent phosphite.

(E)

[Chemical 11] Here, Y ¹ and Y ⁴ are halogen, and R ⁴ , R ⁵ and R ⁶ are the same as above. t represents 0 or 1.

(F) In addition, an alkyl group or an aryl group having 1 to 18 carbon atoms can be mentioned.

In the general formula (1), Y. The number of Z is an average value in the polymer, 0 ≦ k ≦ 2, 0 ≦ p ≦ 2, and
The number of OH is 0 <u ≦ 2.

The hydroxystyrene copolymer and / or its derivative which can be used as the organic binder component in the present invention has a weight average molecular weight of 1000 to 2
It is in the range of, 000,000, preferably in the range of 1,000 to 1,000,000. The reason for this is that the molecular weight of the organic polymer affects the effect of the present invention, and in the case of a low molecular weight substance having a molecular weight of less than 1000, it is difficult to obtain the oxidative stability of the conductive powder.
If it exceeds, 000,000, it is difficult to obtain good conductivity. To obtain such a compound, the repeating unit represented by the general formula (1) usually has n ≧ 3.

A polar group such as an amino group, a phosphoric acid group and a sulfone group (not containing a hydroxyl group or an aromatic ring) is particularly important from the viewpoint of enhancing the affinity and reactivity with the metal powder of the organic polymer, and its preferred The range of polar group densities is between 0.01 and 5 on average per 500 units of molecular weight. Polar group density is 0.0
If it is less than 1, the affinity with the metal powder is poor, which causes a problem.
This is because if the number of the pastes exceeds the limit, the corrosion resistance of the obtained paste will be reduced, which will be a problem. From the viewpoint of improving the corrosion resistance of the conductive powder, amino group-based, methylol group and phosphorus-based polar groups are preferable. The hydroxyl group is important for improving the corrosion resistance of the metal powder and improving the adhesion to the insulating layer, and it is preferable that the hydroxyl group is directly attached as a substituent or the number thereof is large because the effect is exhibited well. The factors such as the molecular weight of the organic polymer, the constitutional unit, the type and density of the polar group, the type of the main chain and the like are important factors that play an essential role for the binder of the conductive paste of the present invention.

Most of the hydroxystyrene copolymer and its derivatives are thermoplastic resins, so it is preferable to use a thermosetting resin together. The blending ratio when using a thermosetting resin varies depending on the purpose. Here, the compounding ratio of the thermosetting resin and the hydroxystyrene copolymer and / or its derivative is 1/99 to 99/1, preferably 95/5 to 40/60. If the compounding ratio of the thermosetting resin is less than 1, it is difficult to obtain conductivity, and if it is 99 or more, the characteristics of the hydroxystyrene copolymer and / or its derivative are lost.

The thermosetting resin effectively used in the present invention is a known thermosetting resin such as phenol resin, urea resin, amino resin, alkyd resin, silicon resin, furan resin, unsaturated polyester resin, epoxy resin and polyurethane resin. A curable resin can be used. Particularly preferred are phenolic resins and amino resins. Among the amino resins, alkyl etherified melamine resins are effective and have a weight average molecular weight in the range of 500 to 50,000 and an alkyl etherification degree of 10% to 95% (at 100%, triazine ring 1
A range of 6 alkyl ether groups is introduced per unit) is preferred.

Examples of the conductive powder used in the present invention include metal powders such as copper powder, silver powder, nickel powder, and aluminum powder, and powders having a coating layer of the above metal on the surface, but copper powder is particularly preferable. .. Its morphology is dendritic,
It may be in any form of flakes, spheres, and irregular shapes, but dendritic electrolytic copper powder produced by electrolysis or spherical powder is preferable. The average particle diameter is preferably 30 μm or less, and from the viewpoint of high density and multi-contact filling, dendritic powder having a particle diameter of 1 to 10 μm is more preferable. The average particle diameter as used herein means a volume-based median diameter determined by a LA-500 type laser diffraction particle size distribution analyzer manufactured by Horiba Ltd. This is because if the average particle size exceeds 30 μm, it becomes difficult to densely fill the conductive powder, the conductivity is lowered, and the printability is deteriorated. Further, when the surface-treated copper powder is used, particularly excellent conductivity, migration resistance and flexibility are easily obtained. Since it is not necessary to attach solder to the surface of the copper paste and its coating film of the present invention, it may be an organic surface treatment agent or an inorganic surface treatment agent. The conductive powder may be used alone or in a mixed system.
It is preferable that the purity of the metal powder is high. Particularly, the copper powder is most preferably the one having the same purity as that of the copper foil or the plated copper layer used for the conductor of the circuit board.

The content of the conductive powder in the conductive paste of the present invention is 50% by weight or more based on the total weight excluding the solvent.
The range is preferably 5% by weight or less, more preferably 60% by weight or more and 95% by weight or less, further preferably 80% by weight.
It is above 95% by weight. If the blending amount is less than 50% by weight, the absolute amount of the conductive powder is insufficient and sufficient conductivity cannot be obtained. On the contrary, if it exceeds 95% by weight, the absolute amount of the binder is insufficient and the base material of the conductive paste is used. It is not preferable because the adhesiveness with

The conductive paste of the present invention is one kind selected from saturated or unsaturated fatty acids or metal salts thereof and higher aliphatic amines for the purpose of preventing oxidation of conductive powder, imparting dispersibility, or curing catalyst. Alternatively, two or more kinds of additives may be used. Preferred saturated fatty acids include, for example, palmitic acid, stearic acid, arachidic acid, etc., and preferred unsaturated fatty acids include, for example, oleic acid and linoleic acid. Examples of these metal salts include sodium salts and potassium salts. In addition, such that it contains 60% or more of unsaturated fatty acids,
It is also possible to use vegetable oils such as soybean oil, sesame oil, olive oil, and safflower oil.

Further, when an alkyl or alkenylphenol derivative represented by the following formula (2) such as linoleic acid phenol or ricinoleic acid phenol is used, particularly excellent conductivity, migration resistance and rust prevention (moisture resistance reliability) are obtained. Is obtained.

[Chemical 12] Here, R ¹⁶ is a residue of an unsaturated fatty acid represented by the following formula (3) or an ester thereof, which is bonded to the ortho or para position of phenol. R ¹⁷ COOR ¹⁸ (3) (In the formula, R ¹⁷ is an alkyl group or an alkenyl group having 15 to 21 carbon atoms, R ¹⁸ is hydrogen, a hydroxyalkyl group having 1 or more carbon atoms, a branched or straight chain alkyl group, or Indicates an aryl group.)

The unsaturated fatty acid represented by the formula (3) includes palmitooleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, vaccenic acid, arachidonic acid and α-.
Examples thereof include eleostearic acid, talylic acid, ricinoleic acid, and erucic acid.

The unsaturated fatty acid esters are mono-, di-, and triesters obtained by the esterification reaction of the unsaturated fatty acid with various alcohols. The alcohols to be esterified are: Methanol, ethanol, propanol, octyl alcohol,
Linear or branched monohydric alcohols such as dodecyl alcohol, stearyl alcohol, oleyl alcohol, and isostearyl alcohol, ethylene glycol,
Examples include polyhydric alcohols such as propylene glycol, butanediol, hexanediol, nonanediol, propylene glycol, glycerin, and sorbitol, and aromatic monohydric or dihydric alcohols such as benzyl alcohol, phenol, octylphenol, nonylphenol, and catechol. ..

The amount of the saturated or unsaturated fatty acid or metal salt thereof as described above is preferably 0.01% by weight or more and less than 20% by weight, more preferably 0.1% by weight, based on the conductive powder. % And less than 10% by weight.
If it is less than 0.01% by weight, the effect of addition hardly appears, and if it is 20% by weight or more, not only the improvement of dispersibility corresponding to the added amount cannot be obtained, but also the conductivity of the coating film obtained and its durability This is not preferable because it deteriorates the property.

The higher aliphatic amine in the conductive paste used in the present invention may be any organic compound having an amino group, and may have other substituents. For example, it may be an amine having a hydroxyl group derived from an α-olefin. However, since it is necessary to use it together with the conductive powder, for example, a solid substance that is insoluble in a solvent cannot be used. Preferred are higher aliphatic amines having 8 to 22 carbon atoms. Such higher aliphatic amines include stearylamine, palmitylamine,
Examples thereof include saturated monoamines such as behenylamine, unsaturated monoamines such as oleylamine, diamines such as stearylpropylenediamine and oleylpropylenediamine. The total amount of the higher aliphatic amine is preferably 0.01% by weight or more and less than 10% by weight with respect to the conductive powder.

The conductive paste used in the present invention may contain one or more known reducing agents or chelating agents, if necessary, in order to prevent oxidation of the conductive powder. Examples of preferable reducing agents include inorganic reducing agents such as phosphorous acid and hypophosphorous acid, and hydroquinone, catechols, ascorbic acids, hydrazine compounds, formalin, borohydride compounds, reducing sugars, amino acids such as ethylenediaminetetraacetic acid. Examples thereof include polycarboxylic acids and aminophenols such as orthoaminophenol. When a reducing agent or a chelating agent is used in the conductive paste used in the present invention, it is 0.01% by weight based on the conductive powder.
It is preferably 20% by weight or more and less than 20% by weight, and more preferably 0.1% by weight or more and less than 10% by weight.

In order to produce the conductive paste used in the present invention, for example, the binder is first dissolved in a solvent, then the conductive powder is added, and this is kneaded sufficiently uniformly with a disper, a ball mill, a three-roll mill or the like to conduct the conductive material. A sex paste.

As the solvent that can be used here,
Known solvents such as alcohols, ethylene-based or propylene-based glycol ethers such as butyl cellosolve, butyl cellosolve acetate and butyl carbitol, and dibasic acid diesters such as dimethyl adipate can be used. Moreover, these can also be mixed and used.

A preferred embodiment of the circuit board of the present invention will be described with reference to FIG. 1 is a sectional view showing an example of the circuit board of the present invention. As shown in FIG. 1, the circuit board is a conductive layer including the substrate 1, the circuit pattern 2, the ground pattern 3, and the component mounting land 4, and an insulating layer 7 formed so as to cover all or part of the conductive layer. And through holes 5 and 6 are formed if necessary. The circuit board may have a single-sided, double-sided or multi-layer structure, but FIG. 1 shows an example of a double-sided circuit board. The substrate 1 is made of glass / epoxy resin, paper / phenol resin, a synthetic resin substrate such as a polyimide film, or an insulating material such as ceramics.

The conductive layer on the substrate 1 is composed of the circuit pattern 2, the ground pattern 3, the component mounting land 4, etc. as described above, and is produced by screen-printing a conductive paste to form a necessary circuit. To be done. In the present invention, the conductive paste used for producing the conductive layer is a conductive paste prepared as described above, that is, a conductive paste containing conductive powder, an organic binder, an additive and a solvent as essential components. In, a conductive paste in which the organic binder contains a hydroxystyrene-based copolymer having a weight average molecular weight of 1,000 to 2,000,000 and / or a derivative thereof is used. The conductive paste used in the present invention, by coating or screen printing,
A circuit board having an effective conductive layer can be produced by coating the entire surface or a part of the insulating board and curing it by heating or active energy rays.

The film thickness of the printed wiring of the electric circuit which can be used for the printed wiring board of the present invention is usually in the range of 5 to 100 μm, preferably 10 to 50 μm.
If it is less than 5 μm, sufficient conductivity cannot be obtained, and if it is 100 μm or more, the adhesion is lowered, which is not preferable.

The substrate 1 may have through holes 5 if necessary.
6 is opened. That is, in the case of connecting the conductive layers on both sides (for example, the circuit patterns 2 to each other) on the double-sided board, it is desirable to provide through holes (through holes 6) as necessary.
The inner wall of the through hole 6 may be conductive or filled with metal plating or solder, but it may be filled with a conductive paste. As a result, both ends thereof are connected to the corresponding circuit patterns 2 (conductive through holes). If the through hole 5 is merely a component insertion hole (component mounting through hole), a hole filled with a conductive paste or a plating layer is not necessary.

The conductive layer on the substrate 1 is covered with the insulating layer 7 except the component mounting lands 4 and the like. This insulating layer 7 is formed in order to prevent the adhesion of solder in a later process and ensure the insulating property. The insulating layer 7 is made of a thermosetting resist ink, an active energy ray curable resist ink such as an ultraviolet curable resist ink or an electron beam curable resist ink, and is used alone or in combination. Further, a multilayer structure can be formed by repeating the process of printing a conductive paste on the formed insulating layer to form an electric circuit.

In the printed wiring board of the present invention, the solder layer is formed on the electric circuit made of the conductive paste in a bare state before or after printing the overcoat insulating layer by a molten solder bath dipping method or a solder plating method. It can also be formed. The formation of this layer has the effect of improving the conductivity of the electric circuit or facilitating the component mounting on the component mounting land.

[0045]

The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these examples. "Part" in Examples and Comparative Examples
Means "parts by weight".

Examples 1 to 4 A conductive copper paste having the composition shown in Table 4 was prepared using the binder resin shown in Table 1 and the other additives shown in Table 2, and a printed wiring board as shown in FIG. 1 was prepared. Was produced. That is,
Glass / epoxy resin substrate (CEM-3) as substrate 1
First, the through hole 5 is opened. Terminal plating 8
I do. Next, a conductive copper paste was applied by screen printing to a thickness of 20 to 30 μm and cured at 160 ° C. for 30 minutes to form the required circuit pattern 2, ground pattern 3, and component mounting land 4. Further, an insulating layer was formed by screen printing so as to cover the conductive paste layer using the resist shown in Table 3.

Comparative Examples 1 and 2 A conductive copper paste having the composition shown in Table 4 was prepared, and a printed wiring board was prepared in the same manner as in Examples.

Test Example Table 4 also shows the results of examining various characteristics of the printed wiring boards obtained in Examples 1 to 4 and Comparative Examples 1 and 2 described above. Conductivity measurement Conductivity is a digital multimeter (Advantest R6551) that measures the volume resistivity of a heat-cured conductive circuit.
Is a value measured by the two-terminal method using. The formula for calculating the volume resistivity is shown below. Volume resistivity (Ω · cm) = (R × t × W) ÷ LR: Resistance between electrodes (Ω); t: Thickness of coating film (cm);
W: coating width (cm) L: distance between electrodes (cm)

Moisture resistance test Moisture resistance means that the printed wiring board is left standing for 500 hours in an environment of 60 ° C. and 95% relative humidity, and the rate of change in resistance value W _R before and after that is calculated by the following formula. I asked. Resistance change rate _{W R (%) = (R} 500 -R 0) ÷ R 0 R 0: resistance value of the conductive circuit before test (Ω) R _{500: 500} hours the resistance after testing (Omega) W values of _R The moisture resistance of the conductive circuit is displayed as follows. A: W _R is less than 30% B: W _R is less than 100% or more 30% C: W _R is more than 100%

Initial Adhesion Test For the adhesion of the conductive circuit, a 5% aqueous solution of sulfuric acid / ammonium citrate (1: 1) was immersed for 30 seconds at 40 ° C. to dissolve the surface oxide film, and then air-dried with jet air. Conductive paste is screen-printed to a thickness of 20 to 30 μm on a copper foil having a metallic copper surface and an insulating substrate degreased with a solvent to cure it, and further an insulating layer for various overcoats of 20 μm.
After screen-printing and curing to the thickness of, the adhesion of the copper foil / paste interface and the paste / overcoat insulating layer interface was measured according to the cross-cut test method of JIS K 5400 (1979). The judgment criteria are as follows. A: 100/100 B: 90/100 or more to less than 100/100 C: 50/100 or more to less than 90/100 D: 0/100 or more to less than 10/100

Adhesion after Solder Test An organic acid type flux was applied to the surface of a printed wiring board by a brush and then immersed in a molten solder bath at 260 ° C. for 10 seconds.
After leaving the substrate to return to room temperature, an adhesion test was conducted by the above method, and judgment was made according to the above judgment criteria.

[0052]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

Adhesion after Humidification / Soldering Test Under the environment of 60 ° C. and 95% relative humidity, the printed wiring board was left standing for 100 hours, dried at room temperature for 1 hour, and then the organic acid flux was removed. And then immersed in a molten solder bath at 260 ° C. for 10 seconds. After returning the substrate to room temperature, an adhesion test was conducted by the above method, and judgment was made according to the above judgment criteria.

Table 4 shows various characteristics of the printed wiring board according to the present invention together with comparative examples. The conductive circuits of Examples 1 to 4 exhibit excellent volume resistivity (10 ⁻⁴ to 10 ⁻⁵ Ω · cm) while maintaining high adhesion.
The pastes (Comparative Examples 1 and 2) containing no hydroxystyrene copolymer and / or its derivative show that it is difficult to satisfy all of the conductivity, the moisture resistance reliability and the adhesion. Therefore, it can be seen that when the printed wiring board of the present invention is used, high conductivity and high moisture resistance reliability can be exhibited while maintaining particularly excellent adhesion.

[0055]

The printed wiring board of the present invention is characterized in that a conductive paste containing a hydroxystyrene copolymer and / or its derivative as a binder component is used. That is, by adjusting the kind and density of the substituents introduced into the hydroxystyrene-based copolymer and / or its derivative, the affinity and reactivity with the metal surface are controlled to improve the oxidation stability of the conductive powder. As a result, it is possible to maintain the conductivity of the paste for a long period of time. Furthermore, it is possible to significantly improve the adhesion to the surface of the copper foil and the insulating layer.

Therefore, the printed wiring board of the present invention utilizing the conductive paste using the hydroxystyrene copolymer and / or its derivative as the binder component has the moisture resistance reliability and the base material, which have been the major drawbacks of the prior art. It is possible to significantly improve the adhesiveness with. Using this new printed wiring board, it is extremely reliable and simple.
The printed wiring board can be formed inexpensively and stably.
These effects are extremely large industrially.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a printed wiring board showing a configuration of the present invention, which is an example in which circuits are provided on both sides.

[Explanation of symbols]

 1 Board 2 Circuit Pattern 3 Ground Pattern 4 Component Mounting Land 5 Component Mounting Through Hole 6 Conductive Through Hole 7 Insulating Layer 8 Terminal Plating

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/24 B 6736-4E 3/38 Z 7011-4E

Claims (7)

[Claims] 1. A conductive paste containing a conductive powder, an organic binder, an additive and a solvent as essential components, wherein the organic binder contains a hydroxystyrene copolymer having a weight average molecular weight of 1,000 to 2,000,000 and / or a derivative thereof. A printed wiring board obtained by printing an electric circuit using the contained conductive paste and then curing it. 2. A hydroxystyrene copolymer and / or
2. The printed wiring board according to claim 1, wherein the derivative thereof is an organic polymer represented by the following general formula (1). General formula (1): [Wherein, m ≧ 0, n ≧ 3, and an arbitrary number until the weight average molecular weight of the organic polymer of the general formula (1) becomes 1,000 to 2,000,000; 0 ≦ k ≦ 2; 0 ≦ p ≦ 2; 0 <u ≦ 2
(However, k, p, and u represent average values in the polymer.); R
^{1 to} R ³ are H or an alkyl group having 1 to 5 carbon atoms; X is a polymerizable vinyl monomer; Y and Z are the same or different, and Or selected from an alkyl group or an aryl group having 1 to 18 carbon atoms (wherein M is H, an alkali metal,
Organic cations such as alkaline earth metals or amines; Y
¹ and Y ⁴ are halogens; Y ²⁻ and Y ³⁻ are counterions such as halogen ions, organic acid anions and inorganic acid anions; W is S
Or O; R ^{4 to} R ⁸ are the same or different and are linear or branched alkyl groups, alkyl derivative groups, aromatic groups,
Alternatively, H, and R ⁶ and R ⁷ may form a ring with the N group. R ^{9 to} R ¹⁵ are the same or different and are a linear or branched alkyl group, an alkyl derivative group, an aromatic group, or H; q, s, t is 0 or 1, and r is 0, 1
Or 2))] 3. The printed wiring board according to claim 1, wherein the conductive powder is copper powder. 4. The thickness of printed wiring of an electric circuit is 5 to 100.
The printed wiring board according to claim 1, wherein the printed wiring board has a thickness of μm. 5. The printed wiring board according to claim 1, wherein the through holes formed in the printed wiring board are filled with a conductive paste. 6. A multi-layer structure obtained by repeating a process of forming an insulating layer on an electric circuit formed of a conductive paste, and printing the conductive paste on the insulating layer to form an electric circuit. The printed wiring board according to claim 1, further comprising: 7. The printed wiring board according to claim 1, wherein a solder layer is formed on an electric circuit formed of a conductive paste.