JPH10261319A - Electrically conductive copper paste composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion between copper paste and a copper foil of a circuit without deteriorating heat resistance by including a specific quantity of diamino-diphnyl sulfide relative to a thermosetting resinous solid component as well as copper powder, thermosetting resin as inevitable components. SOLUTION: Copper power and thermo-hardening resin are used as inevitable components, and furthermore, 5 to 30 wt.% of diamino-diphenyl sulfide is included relatively to thermosetting resinous solid component. In this case, the configuration of copper power can be any one of scaly, arborescent and spherical shape, but particularly arborescent electrolytic copper powder is preferable. Further, epoxy resin, melamine resin, unsaturated polyester resin and phenol resin, etc., can be used as a thermosetting resin. Particularly, so-called resol type phenol resin which is a product of phenol and formaldehyde reacted under an alkaline catalyst is considered preferable. And by such a component composition, this resin can be adequately used for communication at the through-hole part on a printed circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is suitable for conducting through holes in a printed circuit board.
The present invention relates to a conductive copper paste composition that is useful in applications such as circuits and electromagnetic wave shielding.

[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. After embedding, a method of manufacturing a printed wiring board by heat curing has become popular. However, when a silver paste is used, a problem of silver migration has frequently occurred, particularly since the pattern circuit has recently become finer in pitch. Further, silver is an expensive metal although having excellent conductivity.

For this reason, a conductive copper paste (hereinafter, referred to as a copper paste) has recently attracted attention as an alternative. However, since copper is easily oxidized and its oxide is an insulator, it is necessary to incorporate a substance having a reducing action in order to effectively suppress the oxidation of copper. As measures for preventing such oxidation, for example, JP-A-61-3154 and JP-A-63-286577 are known. However, in the case of copper paste, ohmic contact cannot be obtained unless the copper powders are in sufficient contact with each other, and there is still no substitute for silver paste.

[0004]

Heretofore, the present inventors have proposed a copper paste for through-holes as disclosed in Japanese Patent Application No. 6-2 / 1990.
No. 07824, Japanese Patent Application No. 6-295384, Japanese Patent Application No. 7-
No. 161224, Japanese Patent Application No. 7-177822, Japanese Patent Application No. 7
After embedding by screen printing as described in the specification such as -224401 or the like, by heating and hardening, good conductivity of the through hole portion is given, and aging, especially a thermal shock test, a solder dip test, etc. A copper paste has been provided which does not cause poor conductivity in through-hole portions due to thermal shock.

However, recently, some users have shown thermal shock resistance after moisture absorption, that is, as shown in the test method of copper-clad laminates for multilayer printed wiring boards according to JIS standard C-6486, MIL standard P-13949G, and the like. Test after solder boiling and after C treatment (ie, 40 ° C 90%
RH, 96-hour treatment), and there is a demand that the change rate of the conduction resistance value be within 100% by immersion in a solder bath.

In the solder dip test after moisture absorption, the cured conductive copper paste must withstand not only stress due to thermal expansion of the substrate but also stress due to volume expansion caused by rapid gasification of moisture. In the present invention, as a result of examining various additives for expressing the above properties, it was found that diaminodiphenyl sulfide was very effective against stress such as thermal shock. This effect is considered to be due to the fact that diaminodiphenyl sulfide contains a sulfur atom and has a high chemical affinity with copper, so that the adhesion is improved.

[0007]

The present invention relates to a conductive copper paste composition comprising copper powder and a thermosetting resin as essential components, and further comprising diaminodiphenyl sulfide. Is a copper paste composition containing 5 to 30% by weight of diaminodiphenyl sulfide based on the solid content of the thermosetting resin.

As the copper powder used in the present invention, a commercially available product can be used as it is, and any shape such as a scaly shape, a dendritic shape, and a spherical shape can be used. Particularly, a dendritic electrolytic copper powder is preferable. . As the thermosetting resin used in the present invention, an epoxy resin, a melamine resin, an unsaturated polyester resin, a phenol resin and the like can be used, and a so-called resol type phenol resin obtained by reacting phenol and formaldehyde under an alkali catalyst is particularly preferable.

When a solvent is used in the present invention, glycol ethers are preferred. 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 the like, and esters thereof are used. A resin having an appropriate boiling point and vapor pressure can be selected depending on the solubility, drying, and curing conditions of the thermosetting resin.

The diaminodiphenyl sulfide used in the present invention has an action of improving the adhesion between the copper paste and the copper foil of the circuit without lowering the heat resistance.
The amount of diaminodiphenyl sulfide is preferably 5 to 30% by weight based on the solid content of the binder resin. 5
When the content exceeds 30% by weight, the cured product becomes brittle, so that the effect of improving the adhesion is reduced and the reliability of conduction is reduced.

Although various methods can be applied as a method for producing the conductive copper paste composition, it is generally obtained by mixing the constituent components and kneading with a three-roll mill. Also, if necessary, various antioxidants, reducing agents in the composition,
It is also possible to add a solvent, a curing agent, a dispersant, a filler, a coupling agent, an antifoaming agent, a leveling agent and the like.

[0012]

The present invention will be described below with reference to examples and comparative examples.

Example 1-4 Electrolytic copper powder having an average particle diameter of 10 μm as copper powder, resol type phenol resin as thermosetting resin, ethylene glycol monobutyl ether, propylene glycol monobutyl ether and propylene glycol monopropyl ether as solvents Using a mixed solvent, diaminodiphenyl sulfide was further blended, and the mixture prepared in the ratio shown in Table 1 was kneaded with a three-roll mill to obtain a copper paste composition. The copper paste prepared in this manner was used as a paper base phenolic resin substrate PLC-21 manufactured by Sumitomo Bakelite Co., Ltd.
0.5mmφ provided on 47RH (sheet thickness 1.6mm)
Was filled by a screen printing method and cured at 150 ° C. for 30 minutes by a box-shaped hot air drier.

The resistance of each test piece per through hole was measured to confirm the conductivity. Then, at 40 ° C 95
%, A heat-absorbing solder heat resistance test in which a solder dip is performed twice at 260 ° C. for 5 seconds for a sample subjected to a moisture absorbing process for 96 hours, and at −65 ° C.3
A temperature shock test (1000 cycles) was performed at 0 ° C. →→ 125 ° C. for 30 minutes, and the rate of change from the initial conduction resistance was determined for each. Then, a cross section of the inside of the through hole of the test piece was observed, and it was confirmed whether cracks or peeling had occurred in the copper paste. Table 1 shows the above results.

Comparative Example 1 A copper paste was prepared and evaluated in exactly the same manner as in the Example except that diaminodiphenyl sulfide was not blended.

[0016]

[Table 1]

1. Moisture absorption solder test: Test pieces at 40 ° C 95
%, For 96 hours, and then immersed twice in a 260 ° C. solder bath for 5 seconds. 2. Temperature shock test: 1000 cycles of a temperature shock test of -65 ° C for 30 minutes ← → 125 ° C for 30 minutes.

[0018]

As is clear from the above examples, the conductive copper paste composition of the present invention is a conductive copper paste composition excellent in the reliability of through-hole portions in a printed circuit board, and is based on paper. After embedding copper paste by screen printing in through holes provided in printed circuit boards such as phenolic resin substrates or glass cloth base epoxy resin substrates, and then curing by heating, good conductivity of through holes is given, Even after aging, especially after moisture absorption, conductivity failure due to thermal shock does not occur, so that highly reliable electrical connection of through holes can be made. The copper paste of the present invention is not only used for through-hole connection, but also has high adhesion to a printed circuit board substrate or copper foil, and has both heat resistance and flexibility. Of the present invention, and further, it is suitably used for a flexible circuit board.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H05K 1/09 H05K 1/09 D 3/40 3/40 K

Claims (2)

[Claims] 1. An essential component comprising copper powder and thermosetting resin,
A conductive copper paste composition further comprising diaminodiphenyl sulfide. 2. The conductive copper paste composition according to claim 1, which comprises 5 to 30% by weight of diaminodiphenyl sulfide based on the solid content of the thermosetting resin.