JPH0969314A - Conductive copper paste composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive copper paste composition with good adhesivity and conductivity by forming the composition with copper powder, thermosetting resin, couping agent shown in the Formula containing Ti or Al and solvent and then heating and hardening it after screen-printed to a through-hole in a printed circuit board. SOLUTION: Finest possible copper powder available in a market is used. Resol type phenol resin is suitable for thermosetting resin as binder. The reaction of coupling agent shown in the Formula containing Ti or Al in the center with the surface of copper prevents oxidation inside and improves scattering property. The combination rate is preferably 0.5-2 wt.pts to 100 wt.pts copper powder. In addition, polyvalent phenol monomer, imidazole compound and reactive rubber elastomer are preferably incorporated therewith for oxidation and crack prevention and flexibility improvement. In this way, less deteriorating conductivity is obtained in long time use, specially at a severe temperature.

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, to screen printing on through holes of a printed circuit board such as a paper-based phenolic resin board or a glass fiber-based epoxy resin board. rear,
The present invention relates to a conductive copper paste composition which has good substrate adhesion and good conductivity by heating and curing, and has little change with time after curing, especially the change in conductivity of through-hole parts due to thermal shock. is there.

[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 essentially more easily oxidized than silver, it is difficult for copper paste to maintain conductivity for a long period of time. That is, copper is oxidized in the process of hardening after screen printing, and measures for preventing such oxidation are known, for example, in JP-A-61-3154 and JP-A-63-286477. . Furthermore, in the case of a copper paste, if the copper powders do not come into sufficient contact with each other, they will not conduct and will not be a substitute for the silver paste.

[0003]

In order to bring the copper powders into sufficient contact with each other, attempts have been made to use a resin such as a resole having a large curing shrinkage as a binder. In addition, in order to effectively exert its binding force, Japanese Patent Laid-Open No. 5-179164
Heterocyclic compounds have also been added as disclosed in the publication. However, especially in the case of a small-diameter through hole, unlike a circuit on a plane, stress due to curing shrinkage of the resin and stress due to linear expansion of the printed circuit board in the Z-axis direction cause cracks and are likely to cause poor conduction.

The present inventor has conducted an improvement study on the drawbacks of conventional copper pastes, and as a result, by using copper powder, thermosetting resin, polyhydric phenol monomer, coupling agent and imidazole compound as essential components, Copper paste for through-holes, which suppresses the generation of cracks, which was the biggest problem, and makes the contact between copper powders due to curing shrinkage of the resin very efficiently, and achieves conduction performance and high reliability comparable to silver paste. Completed and filed a patent application (Japanese Patent Application No. 6-20
7824).

Further, since the printed circuit board comes into contact with molten solder when mounting components, the copper paste needs heat resistance. However, by mixing an optimum amount of a reactive rubber elastomer, the heat resistance of solder and the like can be instantaneously improved. We have completed a copper paste with improved thermal shock resistance at high temperatures and applied for a patent (Japanese Patent Application No. 6-
295384).

Further, the printed circuit board is often continuously exposed to various temperatures ranging from low temperature to high temperature after mounting components, and it is desired that the printed circuit board has high reliability against continuous high temperature and low temperature. The present invention has completed a highly reliable copper paste for through-holes, which has almost no change in conductivity even at continuous high and low temperatures by the above composition. The object of the present invention is fine pitch which can be screen-printed, has both good conductivity as silver paste and migration resistance which cannot be obtained with silver paste, and has long-term reliability even under severe continuous use temperature. It is to provide a copper paste composition suitable for a corresponding through hole.

[0007]

The present invention relates to a copper powder, a thermosetting resin, a polyhydric phenol monomer, an imidazole compound, a reactive rubber elastomer, a coupling agent represented by the chemical formula 1 having Ti or Al at the center, and The present invention relates to a conductive copper paste composition containing a solvent. (Hydrolyzing group) _n - _{Mn + p-} (Hydrophobic group) _p (1) M: Ti or Al, n: Number of hydrolyzing groups, p: Number of hydrophobic groups

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

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 as an alkali catalyst. The so-called resol type phenolic resin which has been converted to methylol below is preferable in terms of heat resistance and adhesion to copper. It is preferable to add a polyhydric phenol monomer to the present invention to prevent copper oxidation. As the polyhydric phenol monomer, catechol, resorcin, hydroquinone and the like can all be used, but hydroquinone is particularly preferable.

The amount of the thermosetting phenolic resin used in the present invention is preferably 8 to 20 parts by weight with respect to 100 parts by weight of copper powder. When the amount is less than 8 parts by weight, the amount of the phenol resin is small, so that a sufficient binding force cannot be obtained, and when the amount is more than 20 parts by weight, the conductivity decreases. The amount of polyhydric phenol monomer added is preferably 3 to 10 parts by weight with respect to 100 parts by weight of copper powder.
If it is less than 10 parts by weight, the effect of preventing oxidation of the copper powder is small, and if it exceeds 10 parts by weight, various performances such as conduction resistance of the copper paste deteriorate.

In the present invention, it is preferable to add an imidazole compound. The imidazole compound is, for example, N, N ′-{2-methylimidazolyl- (1) -ethyl}
-One or more imidazole compounds with long-chain aliphatic hydrocarbons, such as eicosandioyldiamide, are preferably 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 becomes dense, and good electrical conductivity is obtained.

In the present invention, it is preferable to blend a reactive rubber elastomer. As the reactive rubber picture last mart, one or more kinds of polybutadiene type or polyacrylonitrile butadiene type having a reactive group at the end are used. The terminal reactive group of this reactive rubber elastomer may be a carbonyl group, an amino group, an epoxy group, a hydroxy group, an amide group or the like as long as it can react with a phenol resin when heated, and is not particularly limited, but a carbonyl group, an amino group A base and an epoxy group are preferable in terms of the performance of the copper paste. This reactive elastomer imparts flexibility to the cured product without reducing the reliability as a copper paste,
The reliability of impact resistance can be greatly improved.

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.

The structure of the coupling agent used in the present invention is represented by Chemical Formula 1. (Hydrolysis group) _n - _{Mn + p-} (Hydrophobic group) _p (1) M: Ti or Al, n: Number of hydrolyzing groups, p: Number of hydrophobic groups This coupling agent reacts with the surface of copper. By coating the surface, it has the effect of preventing internal oxidation of copper powder,
Furthermore, since the dispersibility of the copper powder is improved, it has stable conductivity and excellent heat shock properties. The blending amount is preferably 0.2 to 4 parts by weight with respect to 100 parts by weight of copper powder. If the amount is less than 0.2 parts by weight, the effect cannot be sufficiently exhibited, and even if the amount is 4 parts by weight or more, the effect cannot be further improved.

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

[0016]

EXAMPLES The present invention will be described below with reference to examples. A resol type phenol resin was used as the thermosetting resin, and the mixture was kneaded with three rolls according to the blending ratios in Tables 1 to 4 to obtain a copper paste composition.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

Table 5 shows chemical formulas of the titanate coupling agents 1 to 12 used.

[Table 5]

The chemical formula of the coupling agent 13 is shown below.

Embedded image

The prepared 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. After measuring the through-hole conduction resistance value of the test piece thus produced, the test piece was left in an oven at 100 ° C. for 1000 hours, and the change in conduction resistance from the initial value was obtained.

[0024]

The copper paste composition according to the present invention is embedded in a through hole portion provided on a printed circuit board such as a paper base substrate or a glass base substrate by screen printing and then heated and cured to form a through hole portion. It is very useful as a through hole for printed circuit boards because it gives good conductivity and does not deteriorate in conductivity even in continuous use at a severe temperature.

Claims (5)

[Claims] 1. A conductive copper paste composition containing copper powder, a thermosetting resin, a coupling agent represented by Chemical Formula 1 having Ti or Al in the center, and a solvent as main components. (Hydrolyzing group) _n - _{Mn + p-} (Hydrophobic group) _p (1) M: Ti or Al, n: Number of hydrolyzing groups, p: Number of hydrophobic groups 2. The compounding ratio of the coupling agent is 0.5 to 2 parts by weight with respect to 100 parts by weight of copper powder.
The conductive copper paste composition as described in the above. 3. The conductive copper paste composition according to claim 1, which contains a polyhydric phenol monomer. 4. The conductive copper paste composition according to claim 1, containing an imidazole compound. 5. The conductive copper paste composition according to claim 1, which contains a reactive rubber elastomer.