JPH0912937A - Electroconductive copper paste composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition produced by using a specific mixed solvent, free from change of composition on a printed board and the filling of a through hole with a filled copper paste in the case of curing in the through hole and, accordingly, generating no strain and having high reliability. CONSTITUTION: This copper paste composition contains, as essential components, (A) copper powder (preferably a dendritic electrolytic copper powder), (B) a thermosetting resin (preferably a resol-type phenolic resin), (C) a polyhydric phenol monomer (preferably hydroquinone), (D) an imidazole compound, (E) a reactive rubber elastomer (preferably e.g. a polybutadiene elastomer having carboxyl group, amino group, etc., as terminal reactive groups) and (F) a mixed solvent produced by compounding a glycol ether derivative (preferably ethylene glycol monomethyl ether, etc.) with a phenolic compound (preferably phenol, p-cresol, etc.). The glycol ether derivative is preferably compounded with 5-30wt.% of the phenolic compound.

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 excellent in the reliability of through holes in a printed circuit board. More specifically, it is a paper base material phenol resin base material or glass cloth base material. After embedding a copper paste by screen printing in the through holes provided on the printed circuit board such as the epoxy resin board, heat it.
The present invention relates to a conductive copper paste composition which, when cured, imparts good conductivity to the through-hole portion and does not cause poor conductivity of the through-hole portion due to aging, particularly thermal shock.

[0002]

2. Description of the Related Art Through holes are provided in lands of a printed circuit board such as a paper-based phenolic resin board or a glass cloth-based epoxy resin board, and a conductive silver paste (hereinafter, referred to as a silver paste) is screen-printed there. A method of manufacturing a printed wiring board by heat curing after embedding has recently become popular. However, when a silver paste is used, a migration problem frequently occurs especially in a pattern circuit which has been made finer recently. Also,
Although silver has excellent conductivity, it is an expensive metal.

For this reason, a conductive copper paste (hereinafter, referred to as a copper paste) has recently attracted attention as an alternative. However, copper is easily oxidized, and since the oxide is an insulator, it is necessary to effectively suppress the oxidation of copper and further to add a substance having a reducing action. As measures for preventing such oxidation, for example, JP-A-61-3154 and JP-A-63-286577 are known.
However, in the case of a copper paste, ohmic contact cannot be obtained unless the copper powders are in sufficient contact with each other, and a silver paste has not yet been replaced.

[0004]

In the case of through holes, both the silver paste and the copper paste can be embedded in a small diameter hole, have low bleeding property, low plate dryness, and other printing workability, and the paste in the through hole can be formed. The shape greatly affects the reliability. Ideally, it is preferable that the through holes are covered with a uniform thickness with the copper paste and the walls are not filled with the copper paste as shown in FIG. When the inside of the wall is partially filled as shown in FIG. 2, stress concentration occurs due to hardening shrinkage of the copper paste, which causes strain and leads to a decrease in reliability.

[0007] Japanese Patent Application No. Hei 7 (1994) is used to form such a shape after curing.
Although the presence of a low boiling point solvent becomes important as described in US Pat. No. 3,133,209, when printing a large number of printed circuit boards, the low boiling point solvent volatilizes over time on a screen plate. Finally, a conductive copper paste different from the original solvent composition is printed and embedded in a small diameter. Therefore, by using a glycol ether derivative as the main solvent instead of the low-boiling point solvent, it is possible to suppress the composition change on the plate, prevent the skin from sticking, and have a moldability that does not lead to wall separation after curing. It was

[0006]

The present invention comprises a copper powder, a thermosetting resin, a polyhydric phenol monomer, an imidazole compound, a reactive rubber elastomer and a solvent as essential components,
A conductive copper paste composition, which is a mixed solvent containing at least one glycol ether derivative as a solvent and further containing 5 to 30% by weight of phenols with respect to the glycol ether derivative.

In the present invention, examples of glycol ethers include 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 the like, and esterified products thereof are used.

Those having appropriate boiling points and vapor pressures are appropriately selected depending on the solubility, drying and curing conditions of the thermosetting resin used. Preferred glycol ethers are ethylene glycol monomethyl ether and 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 monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether.

In addition to this glycol ether derivative,
By blending phenols, which easily volatilize in the drying step, it is possible to further suppress the composition change of the solvent on the plate. Phenol, para-cresol, ortho-cresol and the like are effective as the phenols. If the addition amount of these phenols is less than 5% by weight, the effect of controlling the copper paste cured product in the through-holes so as not to fill the wall is small, and if it exceeds 30% by weight, printing bleeding may occur.
This may cause a short circuit between wiring circuits.

As the copper powder used in the present invention, a commercial product can be used as it is, and any shape such as scale, dendritic or spherical shape can be used, but dendritic electrolytic copper powder is particularly preferable. . The thermosetting resin used in the present invention may be an epoxy resin, a melamine resin, an unsaturated polyester resin, a phenol resin or the like, but a so-called resol type phenol resin obtained by methylating phenol and formaldehyde under an alkali catalyst is particularly preferable.

The polyhydric phenol monomer used in the present invention may be catechol, resorcin, hydroquinone, etc., but hydroquinone is particularly preferable. Further, this polyhydric phenol monomer, for example, hydroquinone forms the following redox system. This facilitates electron conduction, and hydrogen released from the redox system can reduce copper oxide, resulting in long-term reliability.

[0012]

Embedded image

As the reactive rubber elastomer used in the present invention, one or more of a polybutadiene type or a polyacrylonitrile butadiene type having a reactive group at the terminal is used. The terminal reactive group of this reactive rubber elastomer is a carboxyl group, an amino group, an epoxy group, a hydroxyl group,
It is not particularly limited as long as it can react with the phenol resin when heated, such as an amide group, and is not particularly limited, but a carboxyl group, an amino group, and an epoxy group are preferable from the viewpoint of the performance of the copper paste. This reactive rubber elastomer imparts flexibility to the cured product without lowering the reliability as a copper paste, and can greatly improve the reliability of thermal shock resistance.

Although various methods can be applied as a method for producing the conductive copper paste composition, it is generally obtained by mixing the components and kneading them with a three-roll mill. Further, if necessary, various antioxidants, dispersants, and
It is possible to add fine fused silica, a coupling agent, an antifoaming agent, a solvent and the like.

[0015]

EXAMPLES The present invention will be described below with reference to examples. An electrolytic copper powder having an average particle diameter of 10 μm was used as the copper powder, and a resol-type phenol resin was used as the thermosetting resin. The copper paste prepared in this manner was used as a paper base phenol resin substrate PLC-2 manufactured by Sumitomo Bakelite Co., Ltd.
A 0.4 mmφ through hole of 147 RH (plate thickness 1.6 mm) was filled by a screen printing method, and cured by a box hot air dryer at 150 ° C. for 30 minutes.

The conduction performance per through hole of this test piece was measured and confirmed as a resistance value. Then 26
Solder heat resistance test with 5 dips at 0 ° C for 5 seconds, and -6
5 ° C, 30 minutes ← → 125 ° C, 30 minutes temperature shock test (1
000 cycles) to determine the rate of change from the initial conduction resistance. Then, the inside of the through hole of this test piece was observed and it was confirmed whether the copper paste had cracks. Further, the shape of the copper paste portion was observed after cutting and polishing in the vertical direction from the center of the through hole. Table 1 shows the above results.

[0017]

[Table 1]

[0018]

EFFECT OF THE INVENTION The copper paste composition according to the present invention causes no change in solvent composition when it is embedded by screen printing in a through hole portion provided in a printed circuit board such as a paper-based phenol resin substrate or a glass cloth-based epoxy resin substrate. Almost no, so-called plate dry work can be done. Also,
By heating and hardening after filling, it gives good conductivity in the through-hole part and its change with time is extremely small, and since the inside of the wall is not filled with the filled copper paste after hardening, the copper paste is hardened. Stress concentration due to shrinkage does not occur, and the occurrence of strain is suppressed, resulting in high reliability.

[Brief description of the drawings]

FIG. 1 is a through-hole cross-sectional view when a copper paste of the present invention is screen-printed on a circuit board.

FIG. 2 is a through-hole sectional view when a conventional copper paste is screen-printed on a circuit board.

[Explanation of symbols]

 1 circuit board 2 through hole 3 copper paste 4 circuit

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H05K 1/09 7511-4E H05K 1/09 D

Claims (2)

[Claims] 1. A copper powder, a thermosetting resin, a polyhydric phenol monomer, an imidazole compound, a reactive rubber elastomer and a solvent as essential components, and as the solvent, at least one or more glycol ether derivatives are contained, and further phenols are contained. A conductive copper paste composition, which is a mixed solvent blended. 2. The conductive copper paste composition according to claim 1, wherein the phenols are blended in an amount of 5 to 30% by weight based on the glycol ether derivative.