JP3142462B2 - Conductive copper paste composition - Google Patents

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,
It relates to a conductive copper paste composition that has good substrate adhesion and good conductivity by heating and curing, and has little change over time after curing, especially a small change in conductivity of through-hole portions 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,
Copper paste has a problem in that it is difficult to maintain conductivity for a long time because copper is more easily oxidized than silver. That is, it is because 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-63-286577 are known. . Furthermore, in the case of copper paste, if the copper powders do not sufficiently contact each other, they do not conduct, and do not become silver paste substitutes.

[0003]

Attempts have been made to use a resin such as resol which has a large curing shrinkage as a binder in order to bring the copper powders into sufficient contact with each other. Further, in order to effectively exhibit the bonding force, Japanese Patent Application Laid-Open No. 5-179164 is disclosed.
The addition of a heterocyclic compound has also been carried out as disclosed in Japanese Patent Publication No. However, in particular, in the case of a small-diameter through hole, unlike a circuit on a plane, stress due to curing and 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 inventor of the present invention has conducted studies to improve the drawbacks of the conventional copper paste, and as a result, has found that copper powder, a thermosetting resin, a polyhydric phenol monomer, a coupling agent, and an imidazole compound are used as essential components. Copper paste for through-holes, which suppresses the generation of cracks, which is the biggest problem, and allows copper powder to contact each other very efficiently due to resin shrinkage due to curing shrinkage, achieving conduction performance comparable to silver paste and high reliability Was completed and a patent application was filed (Japanese Patent Application No. 6-20).
No. 7824).

[0005] In addition, since the printed circuit board comes in contact with the molten solder during component mounting, heat resistance is required for the copper paste. Completed a copper paste with improved thermal shock resistance at very high temperatures and filed a patent application
295384).

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

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a copper powder, a thermosetting resin, a polyhydric phenol monomer, an imidazole compound, a reactive rubber elastomer, a coupling agent represented by the formula 1 having Ti or Al in the center, and A conductive copper paste composition comprising 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

[0008] In the present invention, commercially available copper powder can be used as it is, and any shape can be used, such as scaly, dendritic, and spherical, and atomized copper powder, ground copper powder, and electrolytic copper powder can be used. Both can be used. The particle size is not particularly limited, but is preferably 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 a binder may be an epoxy resin, a melamine resin, an unsaturated polyester resin, a phenol resin or the like, and is not particularly limited. A so-called resol-type phenol resin which is converted to methylol below is preferred in terms of heat resistance and adhesion to copper. It is preferable to blend a polyhydric phenol monomer in the present invention to prevent oxidation of copper. As the polyhydric phenol monomer, any of catechol, resorcin, hydroquinone and the like can be used, but hydroquinone is particularly preferable.

The amount of the thermosetting phenol resin used in the present invention is preferably 8 to 20 parts by weight based on 100 parts by weight of the copper powder. If the amount is less than 8 parts by weight, the amount of the phenol resin is small, so that a sufficient bonding force cannot be obtained. If the amount is more than 20 parts by weight, the conductivity decreases. The addition amount of the polyhydric phenol monomer is preferably 3 to 10 parts by weight based on 100 parts by weight of the copper powder.
If the amount is less than 10 parts by weight, the effect of preventing oxidation of the copper powder is small. If the amount exceeds 10 parts by weight, various properties such as conduction resistance as a copper paste are deteriorated.

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 having a long-chain aliphatic hydrocarbon such as eicosandioildiamide are preferably used. This imidazole compound buffers the curing shrinkage of the resin itself and the internal shrinkage due to solvent volatilization, prevents cracks due to thermal stress such as a cured product in the through hole and 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 incorporate a reactive rubber elastomer. As the reactive rubber picture last-mart, one or more of polybutadiene-based and polyacrylonitrile-butadiene-based ones having a reactive group at a terminal are used. The terminal reactive group of the reactive rubber elastomer is not particularly limited as long as it can react with the phenol resin at the time of heating, such as a carbonyl group, an amino group, an epoxy group, a hydroxy group, and an amide group. Groups and epoxy groups are preferred 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 Formula 1. (Hydrolyzing 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. And by covering the surface, has the effect of preventing the internal oxidation of copper powder,
Further, since the dispersibility of the copper powder is improved, it has stable conductivity and has excellent heat shock properties. The compounding amount is preferably 0.2 to 4 parts by weight based on 100 parts by weight of the copper powder. If the amount is less than 0.2 part by weight, the effect cannot be sufficiently exhibited, and even if the amount exceeds 4 parts by weight, no further improvement in the effect can be seen.

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

[0016]

EXAMPLES The present invention will be described below with reference to examples. A resole type phenol resin was used as a thermosetting resin and kneaded with three rolls according to the mixing 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 the 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 prepared in this way, it was left in an oven at 100 ° C. for 1000 hours to determine the change in conduction resistance from the initial value.

[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 substrate substrate or a glass substrate substrate by screen printing, and then heated and cured to form a through-hole portion. It is very useful for printed circuit board through-holes because it provides good conductivity and hardly deteriorates conductivity even in continuous use at severe temperatures.

Continuation of the front page (56) References JP-A-63-271995 (JP, A) JP-A-5-29738 (JP, A) JP-A-5-29736 (JP, A) JP-A-6-244520 (JP) JP-A-5-179164 (JP, A) JP-A-6-184409 (JP, A) JP-A-6-139818 (JP, A) JP-A-5-114772 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 1/22 C09D 5/24 H05K 1/09

Claims (1)

(57) [Claims] 1. Copper powder, thermosetting resin , polyhydric phenol
Monomers, imidazole compounds, reactive rubber elastomers
-A conductive copper paste composition comprising as a main component a coupling agent represented by Formula 1 having Ti or Al at the center and 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