JPH09180543A - Conductive copper paste composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide good conductivity, migration resistance and quick hardenability while screen printing can be performed, by using copper powder, thermosetting resin, polyvalent phenol monomer, specific amine, etc. SOLUTION: As copper powder used in conductive copper paste, atomized copper powder, stamped copper powder and electrolytic copper powder are used, and as a thermosetting resin used as a binder, epoxy resin, melamine resin, unsaturated polyester resin, phenol resin, etc., are used. An additive amount of polyvalent phenol monomer is set to 3 to 10 pts.wt. relating to 100 pts.wt. copper powder, further in order to give flexibility by reaction to a resol resin, an imidazole compound is used. Further as specific amine displayed by a prescribed chemical formula, an amine compound having an alcohol system hydroxyl group, for instance, in a molecule like monoethanol amine, is used. After screen printing in a through hole of a printed circuit board, by heating and hardening, good conductivity is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive copper paste composition, and more particularly, it is screen-printed on through holes of a printed circuit board such as a paper-based phenol resin substrate or a glass fiber-based epoxy resin substrate. The present invention relates to a conductive copper paste composition having good substrate adhesion and good conductivity by heating and curing thereafter.

[0002]

2. Description of the Related Art Conductive copper paste (hereinafter, referred to as copper paste) has attracted attention as a conductor for circuit boards in place of expensive conductive silver paste (hereinafter, referred to as silver paste). As a copper paste, a paste composition using a phenol resin or the like as a binder in copper powder is known,
Since copper is inherently more easily oxidized than silver, the copper paste has a problem in maintaining conductivity for a long time. That is, copper is oxidized in the process of curing after screen printing, and as a measure for preventing such oxidation, for example, JP-A-61-3154 and JP-A-63-286.
The method described in Japanese Patent No. 477, etc. is known. Furthermore, in the case of a copper paste, if the copper powders do not contact each other sufficiently, they will not conduct electricity, and it is difficult to immediately become a silver paste substitute.

In order to sufficiently bring the copper powders into contact with each other, attempts have been made to use a resin such as a resole resin having a large curing shrinkage as a binder. Further, in order to effectively exert the binding force, a heterocyclic compound is added as disclosed in JP-A-5-179164. However, depending on the curing conditions, the curing speed is high, and the solvent inside the through holes may remain, causing blistering.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been studied to improve the drawbacks of the conventional copper paste as described above, and as a result, copper powder, thermosetting resin, polyhydric phenol monomer, imidazole compound, and specific It was found that the occurrence of blisters at the time of curing is suppressed by using the above amine as an essential component. An object of the present invention is fine pitch which can be screen-printed, has good conductivity equal to or higher than that of silver paste, and has migration resistance that cannot be obtained with silver paste, and can be rapidly cured in a printing process. It is to provide a copper paste composition suitable for a corresponding through hole.

[0005]

The present invention relates to a conductive copper paste composition comprising a copper powder, a thermosetting resin, a polyhydric phenol monomer, an amine represented by the chemical formula 1 and a solvent. _{H n -N - ((CH 2} ) p -OH) q (1) (n: 0~2, p: 1~6, q: 3-n)

In the present invention, a commercially available copper powder can be used as it is, and the shape can be any of scale, dendritic and spherical, and atomized copper powder, ground copper powder, electrolytic copper powder. Any of these can be used. The particle size is not particularly limited, but in the case of a copper paste having good screen printing characteristics, it is desirable that the powder is as fine as possible.

In the present invention, the thermosetting resin used as the binder may be an epoxy resin, a melamine resin, an unsaturated polyester resin, a phenol resin, or the like, and is not particularly limited, but phenol and formaldehyde are used. A resole-type phenol resin that is methylolated under an alkaline catalyst is preferable in terms of heat resistance and adhesion to copper. In the present invention, catechol, resorcin, hydroquinone, and the like can be used as the polyhydric phenol monomer used for preventing copper oxidation, and hydroquinone is particularly preferable.

The amount of the thermosetting resin compounded is preferably 8 to 20 parts by weight with respect to 100 parts by weight of the copper powder. If it is less than 8 parts by weight, the amount of resin is small and a sufficient bonding force cannot be obtained, and if it is more than 20 parts by weight, the conductivity is lowered. The amount of polyhydric phenol monomer added is 3 with respect to 100 parts by weight of copper powder.
It is preferably from 10 to 10 parts by weight, and when it is less than 3 parts by weight, the antioxidant effect of the copper powder is small, and when it exceeds 10 parts by weight, various performances such as conduction resistance as a copper paste are deteriorated.

In the present invention, it is preferable to use an imidazole compound in order to give flexibility by reacting with the resole resin. Examples of the imidazole compound include N,
N '-{2-methylimidazolyl- (1) -ethyl}-
One or more imidazole compounds having long-chain aliphatic hydrocarbons such as eicosandioyldiamide are used.
This imidazole compound buffers the curing shrinkage of the resin itself and the internal shrinkage caused by the volatilization of the solvent, and prevents the cured product in the through-hole and cracks due to thermal stress such as solder heat resistance after curing and can maintain reliability. Further, the imidazole compound forms a chelate compound with the copper powder, whereby the adhesion is improved, the contact between the copper powders is made dense, and good electrical conductivity is obtained. The compounding amount of such an imidazole compound is 10 parts by weight or less based on 100 parts by weight of the resole resin.

The amine represented by the chemical formula (1) used in the present invention is an amine compound having an alcoholic hydroxyl group in the molecule such as monoethanolamine. This amine compound prevents the rapid progress of curing during the curing process of the resin itself, buffers the internal stress due to shrinkage and solvent volatilization, and prevents cracks due to thermal stress such as the cured product in the through hole and the solder heat resistance after curing. It can prevent and maintain reliability. As an example of such an amine compound, H ₂ N (C
H ₂ ) ₂ OH, HN ((CH ₂ ) ₂ OH) ₂ , N ((CH ₂ )
₂ OH) ₃ , H ₂ N (CH ₂ ) ₃ OH, HN ((CH ₂ ) ₃ O
H) ₂ , N ((CH) ₃ OH) _{3 and the} like. This compounding amount is 0.1 to 100 parts by weight of the entire copper paste.
5 parts by weight. If it is 0.1 part by weight or less, the effect of Amin is small, and if it is more than 5 parts by weight, the heat resistance of the copper paste is lowered and blisters are likely to occur.

The solvent used in the present invention is, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monopropyl ether, Dipropylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether,
Diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether,
Ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol mono 2-ethylhexyl ether, ethylene glycol monoallyl ether, ethylene glycol monophenyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether , And glycol ether inducers such as these ester compounds are used in one kind or in a mixture of two or more kinds.

Although various methods can be applied to the method for producing the conductive copper paste composition, after mixing the structural components,
It is generally obtained by kneading with three rolls. Further, if necessary, various antioxidants, dispersants, and
It is possible to add a solvent or the like.

[0013]

EXAMPLES The present invention will be described below with reference to examples and comparative examples (conventional examples). A resole type phenol resin was used as a thermosetting resin, and kneaded with a three-roll mill according to the mixing ratio shown in Table 1 to obtain a copper paste composition. The obtained copper paste was screen-printed on a paper-based phenolic resin laminate (through-hole hole diameter 0.4 mm) and then cured in an oven at 150 ° C. for 30 minutes.

The blisters in the through holes of this test piece were measured. Further, the through-hole conduction resistance value was measured, the through-hole conduction resistance value was measured even after the heat treatment at 100 ° C. for 1000 hours, and the rate of change of the conduction resistance from the initial value was obtained. Table 1 shows the results. (Blistering in Through Holes) After curing, it was observed how many blisters were produced in 100 through holes. (Rate of change in conduction resistance) Processing was performed at 100 ° C. for 1000 hours.
The rate of change was calculated from the initial conduction resistance value and the treated conduction resistance value by the following formula. Rate of change = (initial conduction resistance value−conduction resistance value after treatment) /
Initial conduction resistance value

[0015]

[Table 1] Amine compound 1 H ₂ N (CH ₂ ) ₂ OH (1) Amine compound 2 HN ((CH ₂ ) ₂ OH) ₂ (2) Amine compound 3 N ((CH ₂ ) ₂ OH) ₃ (3) Amine compound 4 H ₂ N (CH ₂ ) ₃ OH (4) Amine compound 5 HN ((CH ₂ ) ₃ OH) ₂ (5) Amine compound 6 N ((CH ₂ ) ₃ OH) ₃ (6)

[0016]

EFFECTS OF THE INVENTION The copper paste composition according to the present invention is embedded in a through hole provided on a printed circuit board such as a paper-based phenol resin substrate or a glass-based epoxy resin substrate by screen printing and then heated and cured. Due to
It is very useful as a copper paste for through holes because it gives good conductivity to the through holes and does not cause blistering during the curing process.

Claims (1)

[Claims] 1. A conductive copper paste composition comprising copper powder, a thermosetting resin, a polyhydric phenol monomer, an amine represented by the chemical formula 1 and a solvent. _{H n -N - ((CH 2} ) p -OH) q (1) (n: 0~2, p: 1~6, q: 3-n)