JP2648006B2 - Circuit board for EMI measures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a circuit board for EMI countermeasures.
Paper or phenolic resin substrate or glass with an insulating layer
After applying a conductive paste on a circuit board such as an epoxy resin board by screen printing, etc., heat and cure it to form a conductive coating film, and radiate unnecessary electromagnetic waves from the electronic circuit configured on the circuit board Also, the present invention relates to a circuit board for EMI (electromagnetic interference) countermeasures, which is excellent in reliability and productivity, which can effectively suppress unnecessary electromagnetic waves radiated from other devices.

[Conventional technology]

Conventionally, in a television, a radio, a personal computer, a home video game, and the like, unnecessary electromagnetic waves are generated by applying a conductive paste to a high-frequency portion of a circuit or the like via an insulating layer and curing by heating to form a conductive layer. Curb
A circuit board for EMI countermeasures has been proposed (June 55-29276).
JP-A-62-213192, JP-A-62-295498, JP-A-62-295498
63-15498, JP-A-1-175292).

[Problems to be solved by the invention]

A conductive paste is used for the shield electrode layer of the EMI countermeasure circuit board (hereinafter abbreviated as EMI board). Among the conductive pastes, copper paste is particularly inexpensive and migration compared to silver paste (a phenomenon in which copper is ionized when moisture is present at the time of applying a voltage, which is reduced and deposited, grows in a dendritic manner, and causes a short circuit). Because it is difficult to occur, it is attracting attention as a new conductor replacing silver paste. However, when a conductive paste is used as a conductor for an electromagnetic noise suppression (EMI suppression) substrate, extremely strict migration resistance is required. If migration occurs, it will be a serious accident leading to malfunction of the circuit, so this problem is the greatest concern that prevents the spread of EMI boards. At present, although a quick solution has been devised exclusively by applying a special measure to the epoxy-based intermediate insulating layer and the overcoat layer, a basic solution using the copper paste itself is expected. For the above disadvantages,
Although there are few studies from the copper paste side, for example, a method of adding a small amount of zinc to copper metal has been proposed for improving the migration resistance (Japanese Patent Application Laid-Open No. 63-312997). Remains unresolved.

Furthermore, although the current copper paste has fairly good adhesion in the state of a cured coating film, it generally has a disadvantage in that it lacks flexibility and is vulnerable to mechanical shocks when components are mounted. Therefore, the flexibility of the cured coating film is improved by strictly adjusting the curing conditions of the copper paste. Although there are few examples of direct improvement of the flexibility of the copper paste coating film, there are many examples of improvement of the binder in consideration of closely related adhesion. For example, an attempt was made to improve the adhesion between a metal or an insulating layer using a resin or a polyol and a polyester resin or / and an alkyd resin (Japanese Patent Laid-Open No. 62-253675), or a mixture of a melamine resin and an acrylic resin. There is an example in which the adhesion to metal is attempted to be improved by using the method (Japanese Patent Application Laid-Open No. 63-83178), but none of these methods has sufficiently satisfied the requirements.

In addition, the current EMI substrate has many manufacturing steps and takes a long time to manufacture, so that it is very problematic in terms of productivity and cost. This is because a thermosetting resist ink having a long curing time is used for the insulating layer of the EMI substrate.
Therefore, use of an active energy ray-curable resist ink having a shorter curing time for the insulating layer has been studied. However, in the conventional EMI substrate, various problems occur when an active energy ray-curable resist ink is used for the insulating layer. For example, the conductivity of the shield layer in the EMI board is reduced, and the effect of suppressing electromagnetic wave noise is reduced. Cause a defect. This is because the copper paste used for the conventional EMI substrate easily adheres to the thick copper oxide film. When the active energy ray-curable resist ink is used as the insulating layer, a thick copper oxide film is not formed on the surface of the ground pattern after the insulating layer is formed. This is probably because the copper paste does not adhere to the ground pattern. In other words, when the active energy ray-curable resist ink is used as the insulating layer of the EMI substrate, the copper paste is an earth pattern without a thick copper oxide film,
That is, it is necessary to adhere to metallic copper.

Therefore, it is difficult to manufacture an EMI substrate using an active energy ray-curable resist ink for an insulating layer for the above-mentioned reason, and there is a strong demand for improvement of the EMI substrate as well as the above-described migration and flexibility.

[Means for solving the problem]

In view of the present situation, the present inventors have developed an EMI substrate having improved migration resistance and flexibility and an active energy ray-curable resist ink as an insulating layer in order to provide a highly reliable and highly productive EMI substrate. As a result of intensive studies on usable EMI substrates, a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof with respect to a conductive paste used for a shield layer in the EMI substrate, and a thermosetting resin, Is used as a binder component, and the conductive powder is blended, it is possible to reduce the electrochemical activity of the metal surface, reduce the residual internal stress in the coating film, etc., and further form a copper oxide coating. The present invention has been found to be able to adhere to the surface of a non-existent (that is, metallic copper) ground pattern and to achieve the above object, and has completed the present invention.

That is, the present invention provides a substrate, a conductive layer formed on at least one main surface of the substrate and having a circuit pattern including a ground pattern formed thereon, and covering the conductive layer on the substrate except for the portion of the ground pattern. And a shield electrode layer formed so as to cover all or a part of the insulating layer, and connected to the ground pattern,
The EMI countermeasure wherein the shield electrode layer is formed from a conductive paste containing a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof and a thermosetting resin. A circuit board is provided.

It is preferable that the EMI substrate of the present invention further includes a second insulating layer formed so as to cover the shield electrode layer.

A preferred embodiment of the EMI substrate of the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing an example of the EMI substrate of the present invention.

The EMI board is a board 1 and a circuit pattern 2 as shown in FIG.
And a conductive layer such as a ground pattern 3, an insulating layer 7, a conductive paste 8 as a shield electrode layer, and a second insulating layer 9. A through hole 5 and a surface mounting component land 4 are formed as necessary. The EMI substrate may be a single-sided, double-sided or multilayer substrate, but FIG. 1 is an example of a double-sided substrate.

The substrate 1 is made of a synthetic resin substrate such as glass / epoxy resin, paper / phenol resin, or polyimide film, or an insulating material such as ceramics.

The conductive layer on the substrate 1 includes a circuit pattern 2, an earth pattern 3, a surface mounting component land 4, and the like. For example, a copper foil is etched to form a necessary circuit. A through hole 5 is formed in the substrate 1 as necessary. When connecting conductive layers (for example, circuit patterns 2) on both surfaces of a double-sided board, a plating layer 6 is formed on the inner wall of the through hole 5, and both ends thereof are connected to the corresponding circuit patterns 2 respectively.
When the through hole 5 is simply a component insertion hole, the plating layer 6 is unnecessary.

The conductive layer on the substrate 1 is covered with the insulating layer 7 except for the ground pattern 3 and the surface land 4 for surface mounting. The insulating layer 7 is formed in order to prevent the adhesion of solder in a later step and to secure insulation with a conductive paste 8 described later. The insulating layer 7 is made of a thermosetting resist ink, an ultraviolet ray-curable resist ink, an active energy ray-curable resist ink such as an electron beam-curable resist ink, or the like, and is used alone or in combination to form a single layer or a multilayer. You.

The conductive paste 8 covers the whole or a part of the insulating layer 7 and the ground pattern 3 which is not covered with the insulating layer 7.
Thereby, conductive paste 8 is connected to ground pattern 3.

Specifically, the conductive paste 8 used for the shield electrode layer in the EMI substrate of the present invention includes a conductive powder, an organic binder, and a solvent, and the organic binder is a poly-hydroxystyrene derivative or a poly-hydroxystyrene. A conductive paste containing a system copolymer and / or a derivative thereof and a thermosetting resin is used.

In the present invention, the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or a derivative thereof is particularly preferably, for example, a poly-hydroxystyrene derivative represented by the following general formula (I) or a poly-hydroxystyrene derivative represented by the following general formula (II) )) And / or a derivative thereof is effectively used.

[Wherein, n is n ≧ 3 and an arbitrary number until the weight average molecular weight of the organic polymer of the general formula (I) reaches 2,000,000; k, p, u are 0 ≦ k ≦ 2,0 ≦ p ≦ 2, 1 ≦ u ≦ 2, where k + p + u>1; R ^{1 to} R ³ are H or an alkyl group having 1 to 5 carbon atoms; Y and Z are the same or different, and —SO ₃ M, −OCH ₃ , −CR ⁴ R ⁵ OR ⁶ , Or an alkyl or aryl group having 1 to 18 carbon atoms.

(Wherein, M is an organic cation such as H, an alkali metal, an alkaline earth metal or an amine; Y ⁴ is a halogen; Y ^{2 -to} Y ^3- is a halogen ion, an organic acid anion, an inorganic acid anion, etc. A counter ion; W is S or O; R ^{4 to} R ⁸ are the same or different and are a linear or branched alkyl group or an alkyl derivative group such as a hydroxyalkyl group or an aromatic group, or H, further R ⁴ and R ⁷ May form a ring with the N group.

R ^{9 to} R ¹⁵ are the same or different and are linear or branched alkyl groups, or alkyl derivative groups such as hydroxyalkyl groups, aromatic groups, or H; q, s is 0 or 1; t is 1 ; r represents 0, 1 or 2)] [Wherein, m> 0, n ≧ 3, an arbitrary number until the weight average molecular weight of the organic polymer of the general formula (II) reaches 2,000,000; k, p, u are 0 ≦ k ≦ 2,0 ≦ p ≦ 2,1 ≦ u ≦ 2, where k + p + u>0; 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 -SO ₃ M, −Y ¹ , −OCH ₃ , −CR ⁴ R ⁵ OR ⁶ , Or an alkyl or aryl group having 1 to 18 carbon atoms.

(Wherein, M is an organic cation such as H, alkali metal, alkaline earth metal or amine; Y ¹ and Y ⁴ are halogens; Y ^{2 to} Y ³ are halogen ions, organic acid anions, and inorganic acids. counterions such anions; W is S or 0; R ⁴ to R ⁸ are the same or different straight-chain or branched-chain alkyl group or an alkyl derivative group or an aromatic group, or H, such as a hydroxyalkyl group, further R ⁴ And R ⁷ may form a ring with the N group.

R ^{9 to} R ¹⁵ are the same or different, and a linear or branched alkyl group, or an alkyl derivative group such as a hydroxyalkyl group, an aromatic group, or H; q, s, t is 0 or 1; Represents 0, 1 or 2)] In the present invention, the shield electrode layer is 1 × 10 ⁻² obtained by heating and curing the conductive paste used in the present invention.
It means a cured product or a cured coating film having a specific resistance (volume resistivity) of Ω · cm or less.

The synergistic effect of the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer used in the EMI substrate of the present invention and / or the derivative thereof and the thermosetting resin is adjusted by adjusting the kind and the mixing ratio thereof. For the first time, it is possible to control the activity of the metal surface, the shrinkage force in the cured coating state, and the residual internal stress by combining the two components to the maximum extent. The flexibility and flexibility are enhanced, and the reliability as an EMI substrate is ensured.

In addition, due to the synergistic effect of the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or the derivative thereof and a thermosetting resin, an earth pattern after forming an insulating layer using an active energy ray-curable resist ink, That is, the conductive paste comes into close contact with the ground pattern on which the thick copper oxide film is not formed, and the active energy ray-curable insulating layer can be used, so that the production of an EMI substrate excellent in productivity can be achieved. .

One of the organic binder components used for the EMI substrate of the present invention is a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof represented by the general formula (I) or (II). In general formulas (I) and (II), k, m, n, p and u are not defined as integers, but are arbitrary numbers (real numbers) within a certain range. When considering the monomers constituting the polymer, k, m, n, p and u are naturally integers. However, the polymer is a mixture in its properties, and it is more correct to consider the properties of the polymer as the properties of the mixture than to consider its individual building blocks. Therefore, the present invention
In the organic binder used for the EMI substrate, the general formulas (I) and (II) are shown as an average composition.

The poly-hydroxystyrene derivative represented by the general formula (I) is a compound having a substituent represented by Y or Z in the general formula (I), such as hydroxystyrene, isopropenylphenol (hydroxy-α- (Methylstyrene) or a homopolymer of a hydroxystyrene derivative such as hydroxy-α-ethylstyrene. The polymerized units such as hydroxystyrene and isopropenylphenol may be in an ortho-form, a meta-form, a para-form or a mixture thereof, but a para-form or a meta-form is preferred.

The substituents of the hydroxystyrene unit -SO ₃ M or As the alkali metal or alkaline earth metal of M in the above, Li, Na, K, Mg, Ca, Sr, Ba and the like are suitable.

Also, a substituent of the hydroxystyrene unit R ^{4 to} R ⁸ are the same or different and have 1 to 1 carbon atoms.
36 straight-chain or branched-chain alkyl groups, or alkyl derivative groups such as hydroxyalkyl groups, aminoalkyl groups, phosphoalkyl groups, mercaptoalkyl groups, or straight-chain or branched-chain alkyl groups having 1 to 16 carbon atoms R ⁶ is selected from aromatic groups such as a phenyl group.
And R ⁷ may form a ring. 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.

Also, a substituent of the hydroxystyrene unit R ^{9 to} R ¹⁵ are the same or different, and are H or a linear or branched alkyl group having 1 to 36 carbon atoms or an alkyl derivative group such as a hydroxyalkyl group, an aminoalkyl group, a mercaptoalkyl group, or a phosphoalkyl group. Or an aromatic group such as a phenyl group substituted with a straight-chain or branched-chain alkyl group having 1 to 16 carbon atoms, and preferably a straight-chain or branched chain having 1 to 8 carbon atoms. Chain alkyl group, hydroxyalkyl group or carbon number 1
And aromatic groups substituted with a straight-chain or branched-chain alkyl group.

Polar groups (excluding hydroxyl groups and aromatic rings) such as amino groups, phosphoric acid groups, and sulfone groups are particularly important in terms of enhancing the affinity and reactivity of the polyhydroxystyrene derivative with the metal powder. Density range is molecular weight 500
On average between 0.01 and 5 per unit. Polar group density is 0.
If it is less than 01, the affinity for the metal powder is poor and a problem occurs.
This is because if the number exceeds the limit, the obtained migration resistance is reduced, which causes a problem. From the viewpoint of improving migration resistance, amino-based, methylol-based and phosphorus-based polar groups are preferred. The hydroxyl group is important for improving the migration resistance and the adhesion to the insulating layer, and it is preferable that the hydroxyl group is directly provided as a substituent, and that the larger the number thereof, the better the effect is exhibited.

The poly-hydroxystyrene-based copolymer represented by the general formula (II) and / or a derivative thereof has a substituent having or not having a substituent represented by Y or Z in the general formula (II). , A copolymer of hydroxystyrene, isopropenylphenol (hydroxy-α-methylstyrene) or hydroxy-α-ethylstyrene, or a copolymer of these hydroxystyrene monomers and other polymerizable vinyl monomers (X )). The polymerized units such as hydroxystyrene and isopropenylphenol may be in an ortho-form, a meta-form, a para-form or a mixture thereof, but a para-form or a meta-form is preferred.

Other vinyl monomers (X) in the case of a copolymer
Examples thereof include known compounds such as anionic and cationic ionic monomers and nonionic monomers, methacrylate, vinyl ester, vinyl ether, malate, fumarate, and α-olefin.

Specific examples of these compounds include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, α, β-unsaturated carboxylic acid amides, α, β-unsaturated carboxylic acids. Representatives of acid esters, substituted amides of unsaturated carboxylic acids, nitriles of α, β-unsaturated carboxylic acids, vinyl acetate, vinyl chloride, vinyl chloroacetate, divinyl compounds such as divinylbenzene, vinylidene compounds, and styrene. Aromatic vinyl compounds, heterocyclic vinyl compounds represented by vinylpyridine and vinylpyrrolidone,
Vinyl ketone compounds, vinyl ether compounds, vinyl amide compounds, monoolefin compounds such as ethylene and propylene, conjugated diolefin compounds such as butadiene, isoprene, and chloroprene, allyl compounds such as allyl alcohol and allyl acetate, and monomers represented by glycidyl methacrylate One or more monomers selected from the group of bodies are used. In this case, the ratio of hydroxystyrene units such as hydroxystyrene units or isopropenylphenol units to other vinyl monomers is suitably from 1/10 to 20/1 in molar ratio.

The substituent of a hydroxy styrene units -SO ₃ M or As the alkali metal or alkaline earth metal of M in the above, Li, Na, K, Mg, Ca, Sr, Ba and the like are suitable.

Also, the substituent of the hydroxystyrene-based unit R ^{4 to} R ⁸ are the same or different and have 1 to 1 carbon atoms.
36 straight-chain or branched-chain alkyl groups, or alkyl derivative groups such as hydroxyalkyl groups, aminoalkyl groups, phosphoalkyl groups, mercaptoalkyl groups, or straight-chain or branched-chain alkyl groups having 1 to 16 carbon atoms R ⁶ is selected from aromatic groups such as a phenyl group.
And R ⁷ may form a ring. 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.

Also, the substituent of the hydroxystyrene-based unit R ^{9 to} R ¹⁵ are the same or different, and are H or a linear or branched alkyl group having 1 to 36 carbon atoms or an alkyl derivative group such as a hydroxyalkyl group, an aminoalkyl group, a mercaptoalkyl group, or a phosphoalkyl group. Or an aromatic group such as a phenyl group substituted with a straight-chain or branched-chain alkyl group having 1 to 16 carbon atoms, and preferably a straight-chain or branched chain having 1 to 8 carbon atoms. Chain alkyl group, hydroxyalkyl group or carbon number 1
And aromatic groups substituted with a straight-chain or branched-chain alkyl group.

Polar groups (excluding hydroxyl groups and aromatic rings) such as amino groups, phosphoric acid groups, and sulfone groups are particularly important in increasing the affinity and reactivity with organic polymer metal powder, and the preferred polar group density Range is 0.01 on average per 500 molecular weight units
It is between ~ 5. If the density of the polar group is less than 0.01, the affinity with the metal powder is poor, and if it exceeds 5, the migration resistance is lowered, which causes a problem. From the viewpoint of improving migration resistance, amino-based, methylol-based and phosphorus-based polar groups are preferred. The hydroxyl group is important for improving the migration resistance and the adhesion to the insulating layer, and it is preferable that the hydroxyl group is directly provided as a substituent, and that the larger the number thereof, the better the effect is exhibited.

The poly-hydroxystyrene derivative represented by the general formula (I) or the poly-hydroxystyrene-based copolymer represented by the general formula (II), which can be used as an organic binder component of the conductive paste used in the present invention. The combined and / or derivative thereof has a weight average molecular weight (w)
Is preferably in the range of 10 to 2,000,000, and 1000 to 100
More preferably, it is in the range of 10,000. The reason for this is poly-
This is because the molecular weight of the hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or its derivative greatly affects some effects of the present invention. That is, the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or the derivative thereof serves as a soft segment in the cured coating film—a portion that acts to alleviate residual internal stress—and has a fine structure on the surface of the metal powder. It plays the role of forming an insulating film or exhibiting adhesion to an earth pattern (that is, the surface of metallic copper) on which the above-mentioned thick copper oxide film is not formed. It is difficult to improve flexibility and adhesion to metallic copper. On the other hand, if w exceeds 2,000,000, the solubility in a solvent such as butyl carbitol and the compatibility with the thermosetting resin blended in the paste are reduced, which is problematic.

Most of the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or its derivative is a thermoplastic resin, and thus it is preferable to use a thermosetting resin in combination.

The thermosetting resin effectively used in the conductive paste used in the present invention includes phenolic resin, urea resin, amino resin, alkyd resin, silicon resin, furan resin, unsaturated or saturated polyester resin, epoxy resin, polyurethane resin Known thermosetting resins such as polyester polyol resin and acrylic resin can be used. In particular, resol type phenolic resins and amino resins are preferred. Among amino resins, alkyl etherified melamine resins are effective, and those having a weight average molecular weight in the range of 1,000 to 25,000 and a degree of alkyl etherification in the range of 20 to 80% are preferable.

It is extremely effective to use a known acidic catalyst for the curing reaction between the amino resin and the poly-hydroxystyrene derivative or the poly-hydroxystyrene-based copolymer and / or the derivative thereof. A conductive coating film having excellent durability and adhesion to an insulating layer and an earth pattern in contact with the shield electrode layer is formed. Examples of the acidic catalyst include mineral acids such as hydrochloric acid and phosphoric acid, linoleic acid, organic fatty acids such as oleic acid, phenol oleate, alkylphenols such as phenol linoleate,
Known acids such as organic acids such as oxalic acid, tartaric acid, paratoluenesulfonic acid or amine salts thereof can be used.

The aforementioned thermosetting resins used for the conductive paste may be used alone or in combination of two or more.

The compounding ratio of the binder component in the conductive paste used in the present invention is 5 to 50% by weight, preferably 5 to 40% by weight, based on the total weight excluding the solvent. Insufficient absolute amount lowers the adhesion, lowers the fluidity of the resulting conductive paste, lowers printability and easily oxidizes the conductive powder during heat curing, and reduces the flexibility of the EMI substrate. This leads to a decrease in the conductivity of the shield electrode layer. When the amount of the binder is more than 50% by weight, the absolute amount of the conductive powder is insufficient, so that the conductivity required for the EMI substrate cannot be obtained.

A poly-hydroxystyrene derivative represented by the general formula (I) or a poly-hydroxystyrene-based copolymer represented by the general formula (II) and / or a derivative (A) thereof and a thermosetting resin (B) And the weight ratio (A / B) of 5/95 to 95 /
A range of 5 is appropriate, preferably a range of 10/90 to 70/30.

Examples of the conductive powder in the conductive paste 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 metal on the surface. Powders are preferred. The form of the conductive powder may be any of resin, flake, sphere, and amorphous. Preferably, the conductive powder is resin-like electrolytic copper powder generated by electrolysis or spherical powder. The average particle diameter is preferably 30 μm or less, and more preferably 1 to 10 μm resinous powder from the viewpoint of high density and multi-contact point filling.

The amount of the conductive powder in the conductive paste used in the present invention is preferably in the range of 50% by weight or more and less than 90% by weight, more preferably 60 to 88% by weight, and particularly preferably, based on the total weight excluding the solvent. Is 75-88% by weight. Compounding amount is 50
If the amount is less than 90% by weight, sufficient conductivity cannot be obtained with respect to the EMI substrate. On the other hand, if the amount is more than 90% by weight, the conductive powder is not sufficiently bound, and the resulting coating film becomes brittle, and the flexibility and migration resistance of the EMI substrate. In addition, the adhesion between the shield electrode layer and the earth pattern or the insulating layer is reduced.

In the conductive paste used in the present invention, one or more selected from saturated or unsaturated fatty acids or metal salts and higher aliphatic amines for the purpose of preventing oxidation of the conductive powder or imparting dispersibility or curing catalyst. Two or more additives may be used. Preferred saturated fatty acids include
For example, palmitic acid, stearic acid, arachiic acid and the like are mentioned, and preferable unsaturated fatty acids are, for example, oleic acid and linoleic acid. Examples of such metal salts include sodium salts and potassium salts. It is also possible to use vegetable oils such as soybean oil, sesame oil, olive oil, safflower oil and the like containing 60% or more of unsaturated fatty acids.

The amount of the saturated or unsaturated fatty acid or the metal salt thereof as described above is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the conductive powder.
10 parts by weight. If the amount is less than 0.1 part by weight, the effect of addition is hardly exhibited.If the amount exceeds 20 parts by weight, not only the dispersibility cannot be improved corresponding to the amount added, but also the conductivity and durability of the obtained coating film. Will decrease.

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 another substituent. For example, an amine having a hydroxyl group derived from an α-olefin may be used. However, for example, a solid that is insoluble in a solvent cannot be used due to the necessity of using it with a conductive powder. Preferred are those having 8 to 22 carbon atoms.
Is a higher aliphatic amine. Examples of such higher amines include saturated monoamines such as stearylamine, palmitylamine and behenylamine, unsaturated monoamines such as oleylamine, and diamines such as stearylpropylenediamine and oleylpropylenediamine.

The higher aliphatic amine is preferably used in a total amount of 0.1 to 10 parts by weight based on 100 parts by weight of the conductive powder.

In the conductive paste used in the present invention, one or more known reducing agents or chelating agents can be used as necessary to prevent oxidation of the conductive powder. Preferred reducing agents include, for example, phosphorous acid, inorganic reducing agents such as hypophosphorous acid, and hydroquinone, catechols,
Examples include ascorbic acids, hydrazine compounds, formalin, borohydride compounds, reducing sugars, aminopolycarboxylic acids such as ethylenediaminetetraacetic acid, and aminophenols such as orthoaminophenol.

When using a reducing agent or a chelating agent in the conductive paste used in the present invention, preferably 0.1 to 20 parts by weight, more preferably 100 parts by weight of the conductive powder.
0.5 to 10 parts by weight.

To produce the conductive paste used in the present invention,
For example, first, a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof is dissolved in a solvent, and then a thermosetting resin and a conductive powder are added. A conductive paste is prepared by kneading the mixture sufficiently using a roll or the like.

Solvents that can be used here include alcohols, butyl cellosolve, butyl cellosolve acetate,
Ethylene or propylene glycol ethers such as butyl carbitol;
Known solvents such as basic acid diesters can be used. These can be used in combination.

As shown in FIG. 1, the conductive paste 8 used in the present invention is coated on the entire surface or a part of the insulating layer 7 so as to be connected to the ground pattern 3 by coating or screen printing. By curing with a wire or the like, an EMI substrate having an effective shield electrode layer can be manufactured. This EMI substrate can also be effectively used as an electrostatic shield.

Further, a second insulating layer 9 is formed to cover the shield electrode layer, that is, the conductive paste 8. The insulating layer 9 is made of a thermosetting resist ink, an active energy ray-curable resist ink such as an ultraviolet ray-curable resist ink or an electron beam-curable resist ink, and is used alone or in combination.
It is formed as a single layer or a multilayer, and prevents the adhesion of solder in a later step.

The operation of the EMI substrate of the present invention for suppressing unnecessary electromagnetic waves will be described.

The conventional circuit board does not have the shield electrode layer, that is, the conductive paste 8, and a floating capacitance or a distributed capacitance is formed between adjacent patterns of the circuit pattern 2. In the EMI board of the present invention, the distributed capacitance is formed between the circuit pattern 2 and the shield electrode layer since the shield electrode layer (conductive paste 8) exists closer to the circuit pattern 2 than between the adjacent patterns. I have. Therefore, the energy of the unnecessary frequency component induced in the circuit pattern 2 flows to the conductive paste 8 through the formed distributed capacitance. Since the conductive paste 8 is connected to the ground pattern 3 of the conductive layer and grounded at a high frequency, the conductive paste 8 described above is used.
The energy of the unnecessary frequency component flowing into the ground pattern 3 flows into the ground pattern 3. Therefore, the energy of the unnecessary frequency component is not accumulated in the circuit pattern 2. Further, since unnecessary frequency component energy is removed from the circuit board itself as described above, even if a cable or the like is connected to the circuit board, unnecessary electromagnetic wave radiation does not occur through the cable.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples. In the examples and comparative examples, “parts” means “parts by weight”.

Example 1 A printed wiring board as shown in FIG. 1 was produced.

That is, a copper-clad laminate was used as the substrate 1, a through hole 5 was first opened, and the inner wall of the through hole 5 was subjected to electroless plating or electrolytic plating to form a plating layer 6. Thereafter, a required printed wiring circuit (circuit pattern 2, ground pattern 3, surface mounting component land 4) was formed on the substrate 1 by etching.

Next, an ultraviolet curable resist ink is applied by screen printing so as to cover the circuit pattern 2, and 1500 mJ / cm ²
And then the same operation was repeated twice to obtain a film thickness of about 50
A μm insulating layer 7 was formed. A copper paste (the composition is shown in Table 1) is applied by screen printing so as to cover the insulating layer 7 and the earth pattern 3 and is cured at 160 ° C. for 30 minutes to obtain a conductive paste layer 8 having a thickness of about 20 μm. Was formed. Further, an ultraviolet curable resist ink is applied by screen printing so as to cover the conductive paste layer 8,
The composition was cured under the condition of 1500 mJ / cm ² to form a second insulating layer 9 having a thickness of about 15 μm.

Example 2 A thermosetting resist ink was used in place of the UV-curable resist ink used for the insulating layer in Example 1, and this ink was cured at 140 ° C. for 20 minutes, and 3 coats and 3 bake were performed to form insulating layers 7 and 9 Was formed. Before the conductive paste 8 is applied, a portion of the printed wiring circuit (for example, the ground pattern 3) that is in contact with the conductive paste 8 is etched with an acid or the like to remove the copper oxide layer on the circuit surface.

The composition of the copper paste in Example 2 is shown in Table 1.

Comparative Example 1 A printed wiring board was produced in the same manner as in Example 1 using a copper paste having the composition shown in Table 1.

Test Example In order to evaluate the reliability of the EMI substrates obtained in Examples 1 and 2 and Comparative Example 1, migration resistance, adhesion, and electromagnetic wave suppression effect (radiation level) were measured by the following methods.

<Migration resistance> Test Under the conditions of 60 ° C and 95% relative humidity, in each of the examples and comparative examples, a DC voltage of 50 V was applied between some of the circuit patterns 2 and the conductive paste layer 8, and the insulation resistance was measured. And the time T until the insulation resistance reaches 10 ⁸ Ω was measured.
In comparison with the T _0, it was evaluated according to the following criteria. Table 1 shows the results.

A: T / T ₀ > 2 B: 1.5 <T / T ₀ ≦ 2 C: 1 <T / T ₀ ≦ 1.5 D: T / T ₀ ≦ 1 Test Using an unsaturated pressure cooker, 121
C., 95% relative humidity, 2 kg / cm ² , in each of the examples and comparative examples, applying a DC voltage of 50 V between some of the circuit patterns 2 and the conductive paste layer 8 to measure the insulation resistance Then, the time T required for the insulation resistance to reach 10 ⁸ Ω was compared with T _{0 of} Comparative Example 1 and evaluated according to the following criteria. Table 1 shows the results.

A: T / T ₀ > 2 B: 1.5 <T / T ₀ ≦ 2 C: 1 <T / T ₀ ≦ 1.5 D: T / T ₀ ≦ 1 <Adhesion> For adhesion, use a cross cut tape peeling test. Was.

In the printed wiring boards of the example and the comparative example, the coating film in the portion where the conductive paste 8 and the ground pattern 3 are in close contact with each other was evaluated.

The cross-cut test means that the cured coating of conductive paste 8
Draw a line that reaches the earth pattern 3 with 11 vertical and horizontal lines at intervals of to make 100 grids. This is a method in which cellophane tape is stuck on top of it, and it is peeled off at a stretch just above. Then, the adhesion was evaluated based on the following criteria based on the number of remaining grids / 100. Table 1 shows the results.

Evaluation criteria ○: 100/100 (no peeling) ×: less than 100/100 <Electromagnetic wave suppression effect (radiation level)> A predetermined component was mounted on the printed wiring boards of the examples and comparative examples, and a board for electromagnetic wave noise measurement (a ) Is prepared. In addition, a predetermined component is mounted on a substrate on which the conductive paste layer 8 and the insulating layer 9 of the example and the comparative example are not printed (that is, a substrate having no shield electrode layer) in the same manner as described above, and the electromagnetic wave noise measurement substrate is formed. (B) is prepared.

The measurement of the electromagnetic wave suppression effect was performed based on the technical standard of the VCCl, 3m method. Specifically, on the open site,
The antenna is fixed vertically and horizontally, and the radiation noise intensity of vertically polarized waves and horizontally polarized waves is measured for a frequency band of 30 to 1000 MHz.

The circuits of the above-mentioned substrates (a) and (b) are operated to perform measurement based on the above-mentioned measuring method, and the result (horizontal polarization) is shown in FIG. From FIG. 2, the frequencies (65 MHz and 115 MHz) where the electric field strength is strong (a) are selected, and the difference between the electric field strengths (a) and (b) at that time is shown in Table 2 as the electromagnetic wave suppression effect (ΔE).

Further, the substrates (a) of the examples and the comparative examples were subjected to a humidity resistance test (60 ° C., 95% relative humidity, 2000 hours), and after the test, the radiation nozzle strength was measured. And 65MHz and 115
The electric field intensity at the frequency of MHz is compared with the electric field intensity of the above-mentioned substrate (b), and a difference between the electric field intensity and the electromagnetic wave suppression effect (ΔE ')
The results are shown in Table 2. It is better that the change in the difference in electric field strength before and after the moisture resistance test is small.

The EMI of the present invention based on the electromagnetic wave suppression effect before and after the above moisture resistance test
The reliability of the substrate was evaluated.

[Effect of the Invention] As described above, the EMI substrate of the present invention has a conductive property containing a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof and a thermosetting resin as a binder component as a shield electrode layer. The use of a conductive paste has a great feature.

From Table 1, it can be seen that an EMI substrate using a poly-hydroxystyrene derivative or a poly-hydroxystyrene-based copolymer and / or a derivative thereof as the conductive paste (Examples 1 and 2)
Exhibits excellent migration resistance, and exhibits excellent adhesion even when a thermosetting or active energy ray-curable resist ink is used for the insulating layer of the EMI substrate. For these reasons, the migration resistance of the EMI substrate is significantly improved, and the EMI substrate can be manufactured using the active energy ray-curable resist ink.

Therefore, for example, the above-mentioned poly-
By using a hydroxystyrene derivative or a conductive paste containing a poly-hydroxystyrene copolymer and / or a derivative thereof, it is possible to measure a significant improvement in reliability and productivity, which have been regarded as major drawbacks of conventional EMI substrates. It is possible.

From FIG. 2 and Table 2, it can be seen that the EMI substrate of the present invention exhibits an excellent electromagnetic wave suppressing effect as compared with a conventional printed wiring board having no shield electrode layer. Further, from Table 2, the present invention using the above-mentioned poly-hydroxystyrene derivative or poly-hydroxystyrene-based copolymer and / or its derivative for the shield electrode layer (conductive paste layer) is shown.
The EMI substrate maintains the effect of suppressing electromagnetic waves even after the moisture resistance test, which indicates that the EMI substrate of the present invention is very excellent in reliability.

As described above, by using the EMI substrate of the present invention, it is possible to provide an EMI substrate having high reliability such as migration resistance and high productivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of the EMI substrate of the present invention, and FIG. 2 shows the electromagnetic wave suppression effect (radiation level) of the conventional substrate (a) having no shield electrode layer and the EMI substrate (b) including the shield electrode layer. FIG. 1: Board 2: Circuit pattern 3: Ground pattern 4: Surface mount component land 5: Through hole 6: Plating layer on the inner wall of through hole 7: Insulation layer 8: Conductive paste (shield electrode layer) 9: Insulation layer

Claims (3)

(57) [Claims] 1. A substrate, a conductive layer formed on at least one main surface of the substrate and having a circuit pattern including an earth pattern formed thereon, and covering the conductive layer on the substrate except for a portion of the earth pattern. And a shield electrode layer formed so as to cover all or a part of the insulating layer and connected to the ground pattern, wherein the shield electrode layer is made of a poly-hydroxystyrene derivative or a poly-hydroxystyrene. An EMI countermeasure circuit board formed of a conductive paste containing a hydroxystyrene-based copolymer and / or a derivative thereof and a thermosetting resin. 2. The EMI countermeasure circuit board according to claim 1, wherein a second insulating layer is formed on the circuit board according to claim 1 so as to cover the shield electrode layer. 3. The EMI countermeasure circuit board according to claim 1, wherein the conductive paste is a copper paste.